Embossed absorbent paper having combined patterns

The present invention relates to the field of absorbent paper to use sanitary and domestic, and is a laminated sheet for products such as paper toiletries, handkerchiefs, towels or rags.

In the household and sanitary paper industry, is used to carry product absorbent crepe paper designated cellulose wadding. We take advantage of its extensibility afforded by crimping for crimping; that is to say distort sheet in parts permanently, and in particular to obtain protuberances on one face of the sheet.

Indeed, the trend in recent years, as regards the products hygiene was to make them softer, softer, more attractive while maintaining or improving their functional characteristics and thickness including resistors. The latter may be affected, improved or degraded, by the embossing process. The embossing is done either on paper high humidity, that is to say, on paper machine wet end or on the Paper low humidity, that is to say, transforming the dry part. The invention relates to embossing low moisture paper.

The most common embossing patterns consist of a repetition, on a geometric basis of elementary protrusions of small cross section and simple geometric shape (see Figure 1). We find an embodiment in US Patent 3,414,459.

This kind of grounds including protrusions repetition frequency can be high - density of elements ranging from 5 to 60 per cm² depending on whether a paper towel or toilet paper - and the surface of the elementary protrusions summits can be less than 1 mm²Mainly affects the characteristics related to the thickness of the sheet, on one hand, and its rigidity and strength on the other. These grounds to achieve a good compromise between the desired improvements features when converting the semi-finished product finished product, and industrial operating conditions; they allow, inter alia, the application of a adequate embossing intensity.

In contrast, numerous studies have shown that these patterns, which can be described as "technical", were perceived by consumers as visually unattractive when they were particularly low density. This negative perception is reinforced by their wide distribution in anonymous.

Solutions to increase the visual impact of these hygiene products without harm the basic properties of the paper have been developed.

One solution is to print decorative patterns before or after operations embossing. It has the advantage of little change embossing contribution and enhancing product visibility. However it has the drawback of positioning the product the market for colored products and decorated while consumers are largely in favor of the united. It also requires investment additional and sometimes a factor penalizing the performance of the line manufacturing.

Another solution of the prior art was to provide, adjacent to the immense Most reasons "technical", embossing patterns favoring the visual aspect. These patterns have a much lower repetition frequency compared to previous patterns and a surface area of ​​a higher order of magnitude. Figure 2 illustrates an example corresponding to the teaching of patent EP 265 298.

The impact of these patterns on the physical characteristics of the paper is more low; the rigidity and the thickness of the sheet are not impaired. Their main asset is the signature or at least the possibility of differentiation they provide. However, this major benefit is directly related to legibility or visibility.

But to achieve this visual attraction, two approaches are a priori identified. The first is to apply imprinting intensity important to ensure proper marking, the second to be limited to giving reasons a good embossing under the usual processing conditions. In the prior art, these two approaches have been necessarily carried out simultaneously.

The more we focus on the visual value unless the forms are geometrically simple. This means less power and marking on the sheet the impression obtained is less regular. Accordingly, it is necessary to increase the intensity of the embossing if we want to affect in the desired extent, Product Features. In doing so, the inherent flaws are amplified to such ground vis-à-vis the lawfulness of the embossing process, and, therefore, behavior the tablecloth both locally and globally. This results locally by a degradation of the product appearance, and in an overall performance restriction the process of embossing in terms of size, speed, and more generally yield.

This explains the need for compromise, for these reasons, between intensity of marking and operating on an industrial scale, which is carried out expense of readability and visibility, and the expected improvement of the characteristics resulting from the processing of semi-finished products into finished products. In the practice, arbitration is necessarily done for the constraints the development of the hygiene product, overshadowing constraints aesthetic value.

These patterns, which can be described as "techno-aesthetic", therefore, have a relatively large repetition frequency, form a relatively compact and closed, and use simple geometric shapes as required assembled into a unit pattern is repeated indefinitely sense walking and cross direction and the orientation is always the same. Finally for a reason produced according to the teaching of patent EP 265 298, the thickness uniformity is noted of the lines forming the outline of the elements.

Another solution of the prior art has been to first define a pattern "Technique" and releasing regularly spaced areas, generally geometric, removing the pins to this ground. These areas are then either left as such, is decorated with aesthetic design. sometimes also associated a printed pattern, but this has been at the expense of the visibility and hence the readability of the visual element of the pattern.

These associations are essentially aimed at modulating, based on patterns "Technical", functional factors of thickness, strength and softness Example of US patent 4320162 or US-A-4 376 671. This patent relates to a combination of two reasons, double deep: the first pattern with relatively spaced elements each others with significant depth, the second shallower. Sure the illustration given in this patent, the first pattern is arbitrarily symbolized by a flower, the second is conventionally identified by pins. Characteristics essential described above for the reasons "techno-aesthetic", particularly the almost constant orientation of the primary reasons are kept in these types of combination.

None of these solutions can play fully on the potential by aesthetic reasons vis-à-vis the final consumer.

Indeed, it is recognized that it is possible to convey values ​​systems (Positive or negative) by the judicious use of shapes, movements, directions (to Example logos). Many studies have also revealed a phenomenon of "halo" induced a particularly positive perception of characteristic of the product by the consumer, and descending masking or otherwise the perception of its potential weaknesses.

In the prior art, the application of such principles to embossing patterns was impossible.

The major reason is that the essential characteristics of freedom, movement, visibility and readability are to a large extent incompatible with the constraints related to the function and production of hygiene products (thickness, regular behavior of the web appearance of the product, speed and performance production).

The incompatibility is also more marked than those characteristics Essential are reinforced by the high embossing intensity required to achieve minimum objectives of economic efficiency due to the very low power embossing such free patterns.

The invention proposes to solve this problem.

The paper diaper according to the invention, in particular for toilet paper, consisting at least one tissue paper ply creped of weight between 12 and 35g / m², Having first and second protrusions disposed respectively according to a first and a second pattern, the first pattern being composed relatively spaced pattern elements to each other, each consisting at least one of said first protrusions and the second pattern, said bottom, comprising the said second protuberances arranged closer together between said pattern elements, is characterized in that the pattern elements form a said first pattern chart being distributed in a proportion of at most 0.5 elements per cm², the first protuberances constituting them having at their summit a surface shape linear whose width is between 0.1 and 2 mm, and in that the second protuberances are disposed in a proportion of at least 30 per cm², Preferably at 40 cm², ensuring the essential functional features relating to embossing.

Thanks to the invention there is provided a combined embossing structure offering benefits arising from the use,<sl><li>a graphic pattern, that is to say the choice of the elements is free, without constraint looking for an increase in thickness or absorption by embossing, this choice may well have the sole objective of finding a attractive and evocative,</li><li>with a background pattern providing technical inputs to the embossing ie in particular, thickness and absorption.</li></sl>

Compared to the embodiment shown in the figures of US Patent 4376671, the embossing structure of the invention, the high density pattern of protuberances background, gives also a textile appearance, pleasing to the eye. the second protrusions do not easily being individually visible to the naked eye because of their small size necessary, the surface at the top is less than 1 mm², are highlights therefore the main reason. This contrast results, in particular, the high ratio between the surface of a pattern element and that of a second protuberance, this ratio being in accordance with another characteristic of the invention greater than 50 and preferably greater than 100, on the one hand, and their high number per unit area, on the other hand.

According to another characteristic of the invention, the graphic pattern elements are distributed in a proportion of at most 0.2 elements per cm². So the effect is further improved contrast.

According to another characteristic of the invention, the width of said surface linear shape is not uniform within the same pattern element. Unlike the "techno-aesthetic" reasons of prior art, an example is shown in Figure 2, by overcoming technical constraints of the pattern, the choice of the pattern becomes more freely allowing access to forms having a Call force to the consumer or a higher appeal. By shaped surface linear, it comprises a surface which the ratio of the length, that is to say the length of the most direct path within this area between the two points farthest on the width, that is to say the average distance between two points any taken on either side of this path, is greater than 1. It is in fact the most often high. Along a path above-mentioned width may thus vary. It is at least 0.1 mm and at most 2 mm. For example, if a pattern element represents a letter of the alphabet, the width can vary from Just as the thick and thin strokes of calligraphy writing.

According to another characteristic of the invention, the second protrusion most close to the pattern element is located at a distance therefrom at least equal to the distance separating two adjacent second elements. This improves yet the contrast between the two patterns.

According to another characteristic, the paper sheet may be composed of at least two plies of which at least one is embossed in accordance with the invention.

According to another characteristic, the first protrusions are provided on one face of the paper sheet and the second protuberances on the other face.

According to another characteristic of the paper sheet consists of at least two embossed plies together.

According to another aspect the invention is particularly a sheet laminate composed of at least two plies of paper that have been embossed separately before their association. Thus the Laminated paper sheet according to the invention, in particular for toilet paper, consisting of at least two plies of absorbent paper crepe basis weight of between 12 and 25 g / m², Each having on the side inwardly of the laminate, the first and second protrusions disposed respectively in a first and second pattern, the first pattern being composed relatively spaced pattern elements to each other, each consisting said first protrusions and the second pattern, called the background pattern, comprising said first protrusions arranged so tighter between said elements pattern, is characterized in that the pattern elements form a graphic pattern being distributed in a proportion of at most 0.5 elements per cm², The first protrusions the component having at their summit a surface of linear form with a width between 0.1 and 2 mm, and the second protrusions are arranged at a rate at least 40 per cm². In particular, the ratio of the area of ​​a pattern element to that a second protuberance is greater than 50.

According to another characteristic of the invention, the height of the second protrusions is different from that of the first protrusions, in particular it is lower. The height difference between them preferably remaining below 0.3 mm. Thanks to this feature, it is possible to combine the two sheets according to only protuberances projecting from the other whose height is more low. Indeed the glue applicator which usually consists of a cylinder mounted in parallel to the embossing cylinder comes into contact only projecting parts. It is the same with spray application. Bonding is only by the protruding elements. We reduced that way the whole surface bonded attending leaves the organization. The rigidity induced by this combination is thereby limited.

According to another characteristic of the invention, the height of the second protrusions is less than 0.5 mm.

Other features and advantages become apparent on reading the description following a non-limiting embodiment of the invention, accompanied by drawings annexed in which:<ul><li>Figures 1 and 2 show embossed products in patterns of art prior,</li><li>3 shows a first exemplary pattern according to the present invention,</li><li>4 shows a sectional view on AA of Figure 3,</li><li>5 shows a second pattern of embodiment according to the invention,</li><li>Figure 6 is a schematic representation of an embossing installation can be used to make a product for which the embossing pattern is according to the invention.</li><li>7 shows a third pattern embodiment consistent with the invention.</li><li>8 shows an enlarged detail of the cylinder surface embossing;</li></ul>

As has been mentioned in the preamble, Figure 1 shows a top view of an absorbent paper, such as paper towels or toilet paper, that commonly found in commerce. The folds constituting the sheet are linked them through the protrusions on each of the plies and tours inwardly of the sheet. Such an assembly is known for example from US Patent 3414459 for an association like the tip / tip - the two plies are glued them by the tops of their bosses - or US patent 3867225 for a Association of the type which they are nested and where the protrusions of one ply are arranged between the protuberances of the other ply, and the connection made through the vertices the protuberances of one with the unembossed portions of the other. In the case of embodiment of Figure 1, these protrusions are shaped with a pointed section transverse circular, oval or polygonal. The number of protrusions per unit surface is a function of the thickness which it is desired for the product. A paper towel to wherein a large absorption is desired, present, for example, 10 protuberances per cm² uniformly distributed.

Figure 2 shows an embodiment of the prior art with a pattern "techno-aesthetic" the type described in patent EP 265 298 for toilet paper marketed by the Applicant under the name "Lotus Little Flower." Each pattern element is a flower, and is defined by a plurality of protuberances elementary in form of closed linear impressions. The line thickness is small: the order of 1 mm. The two plies are joined to one another according to the arrangement tip / tip. The choice of design is still relatively limited because these achievements we wanted to play this forms a functional role and not merely decorative, by ensuring that the pattern can be embossed intensely in order to provide maximum volume. As is described in patent US 4320162, it is also possible to provide protrusions of lesser height between the elementary patterns so charpenter the sheet is to reduce its crushing.

Figures 3 and 5, there is shown the products of the invention, seen from above. The pattern elements 1 of the main graphic pattern consist of first protrusions 10 of elongated shape combining them so as to represent a flower in the example of figure 3 - with the protrusions 10a, 10b, 10c, 10d - and letters in Figure 5 Other patterns are of course possible, such as feathers to evoke softness and flexibility. These protrusions have a width between 0.1 and 2 mm. Thereof is not constant. It reproduces full and hairlines. Furthermore the pattern elements are oriented relative to the machine direction MS in different directions. We note in Figures 3 and 5 that the directions of pattern elements shown are all different. Taking advantage of not assign to these pattern elements the function of imparting thickness to the sheet, can thus choose a design much more freely. It is sufficient that the mark left by the embossing roller on the paper is readable. You can adjust the intensity of the pressure applied by the rubber cylinder to achieve embossing, to a value well below the maximum value likely to be achieved when seeking to give depth to the sheet. The latter then being used less and submitted at low mechanical stress, will not form folds or will not rip despite the use of protrusions whose profile has kinks, and including the distribution of surfaces coming into contact with the sheet is not balanced within a scope in which is inscribed the pattern element. Therebetween pattern of relatively spaced from each other, preferably with at most one element to 5 cm², The second protrusions is shown 2. These have a shape tip, frustoconical or truncated pyramid, of less than 0.5 mm height preferably less than 0.1 mm, with polygonal section, such as a diamond, circular, or well elongated machine direction or cross direction. In particular, protrusions 2 with the first protrusions have a height difference of at least 0.3 mm. The surface of the top of the tips is less than 1 mm². As seen in figure, the distribution of the second projections is regular between the elements of pattern 1. In the example shown, the protrusions are distributed in a staggered configuration as not constant, machine direction and cross direction. Their high density gives the sheet a textile appearance. For this purpose, it is necessary that the number is at least To 30 cm² preferably at 40 cm²In particular it may be higher, 60 or 80 cm² to strengthen this appearance. In addition, the area ratio between an element Pattern 1 and a second protrusion 2 is preferably greater than 50. A ratio higher than 100, further accentuates the contrast. By arranging the second protuberances so as to provide a free zone 12 between protuberances the pattern elements and the background pattern, it enhances contrast and improves the appearance visual. To achieve this open area 12, just delete on the cylinders embossing protrusions 2 immediately adjacent to the protuberances 10 pattern elements, a distance corresponding to the minimum pitch of the pattern of bottom, measured respectively machine direction and cross direction.

Is shown in Figure 7 another embodiment of the invention to further enhance the visibility and legibility of the pattern elements 1. According this embodiment a number of second protrusions 2 situated preferably near the protrusions 10 are arranged in rows 21 parallel to the contours of the pattern elements 1. By alignment is meant here the assembly constituted by the projections which are located on one line, two adjacent protuberances on said line being at a distance from each other less the distance separating them from other surrounding protrusions. The distribution of these breaking with the protrusions, regular projections of the background pattern, accentuates the route pattern elements 1 and improves readability. The distance separating two protuberances along these rows 21 is preferably as small as possible to give the visual impression of a line almost continuously. The protuberances being obtained by embossing on cylinders with spikes in shaped tapered tips, the minimum distance that we can achieve will be that separating adjacent barbs whose bases are touching. These alignments are arranged one side of the projections 10 or on both sides. There may be a single alignment. But it is best to have at least two. If the pattern element 1 is defined by a closed line as shown in Figure 7, will be available, preferably as many rows as well defined space permits. Each pattern Figure 7 contains three rows 21, 22, 23

In the case of a laminated sheet having two plies, where the two plies have been embossed separately before being assembled, as can be seen in Figure 4, the first projections are preferably higher than the second. Can, in this way, readily bind the two sheets by the first only which is placed in position points / points. This gives a less rigid laminated sheet, so more pleasant to touch, a sheet stuck on the majority of its protuberances. However, it is also possible to obtain a bond between the sheets without too stiffen the assembly by spraying a small amount of glue on one of the folds. It is then not necessary to provide a double height between the first and the second protrusions. In this case, each of the folds will have a weight between 12 and 25 g / m².

The invention also covers a sheet to a fold or more embossed plies set so as to have the appearance, for example, in Figure 3 but which sectional shows one of the two plies of Figure 4.

The following describes a known device that enables the manufacture laminated product of the invention. In Figure 5, a first pair is shown in cylinders 101, 103 having a metal engraved roll 101 whose surface implanted geometry corresponding to elements in relief embossing wish. The metallic cylinder is rotated around a horizontal axis and is associated with a rubber cylinder 103 parallel thereto, and with which it a cleaning nip 101, 103. While passing through this gap, a sheet of absorbent crepe paper, such as cellulose wadding, undergoes deformations permanent mechanical due to the pressure exerted by the rubber on the paper supported by the relief elements of the rigid cylinder; he married the then form. Depending on the intensity of the embossing, the paper penetrates more or less into the spaces between the raised elements.

To achieve the desired embossing, the raised elements are distributed according to two patterns: a first pattern with first protuberances that define themselves pattern elements 1 and a second pattern with the second protuberances.

The installation comprises a second pair of embossing rollers with a metal cylinder 105 of the same diameter and rotating in the same horizontal plane the cylinder 101; it cooperates with a rubber cylinder 107 for the embossing.

The cylinders 101 and 105 form between them a clamping gap 101-105 and are driven in opposite rotational speed, synchronous, so as to roll one on the other without slipping.

The facility also includes a gluing system with cylinder 110 applicator 111 of rubber or other equivalent material, bearing against the cylinder 101 upstream of the nip 101-105. A transfer cylinder 113 transfers the adhesive from a plunger cylinder 115 on the applicator roll 111. The plunger cylinder 115 fee glue in a tray not shown.

The paper sheets to be combined are fed from the coils 21, 22. The sheet 1 is guided around the rubber roll 103 and passes into the gap 101-103 she spring embossed by marrying the relief surface of the cylinder metal 101. The application roller 111 deposits the glue in metered quantity on the surface protrusions of the sheet, forming flats.

The second sheet 2 undergoes a similar treatment by passing through the gap 105-107, and is associated with the sheet 1 in the interval 101-105. The laminated sheet which results is then transformed into finished product.

In the case of a sheet with a ply or several plies embossed together, we retains course, only one pair of cylinders 101, 103.

Is shown in Figure 8 a portion of the surface of one of the cylinders embossing, 101 or 105, with first salient elements 150. The shape of these past is lengthened. They have a flat surface on top of which the width is not constant when moving along the element. It is at least 0.1 mm and at maximum of 2 mm. However the height from the bottom of the engraving is substantially constant. Of both sides of the elements 150 are arranged second raised elements 152 in form of a truncated cone or pyramid with a flat at shaped top of small circle, 1mm². From a peak of 150 elements, their level is below. The level difference between them is of the order 0.3 mm. On one side of the first protrusions 150, we observe that the latter raised elements 152 are arranged in rows 161 parallel to the curvature of the element 150. The distance between the alignment 161 of the element 150 is determined depending on the average width of the element 150.

During the embossing operation, the tissue paper sheet is pressed to means of a deformable coating cylinder such as rubber on these elements raised and is of matching shape. Due to the low height of the pattern etching handset and the presence of the background pattern, the sheet is not subjected to excessive stresses at the graphic pattern.