Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B31—MAKING ARTICLES OF PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER; WORKING PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER
  • B31F—MECHANICAL WORKING OR DEFORMATION OF PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER
  • B31F1/00—Mechanical deformation without removing material, e.g. in combination with laminating
  • B31F1/07—Embossing, i.e. producing impressions formed by locally deep-drawing, e.g. using rolls provided with complementary profiles
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H27/00—Special paper not otherwise provided for, e.g. made by multi-step processes
  • D21H27/02—Patterned paper
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B31—MAKING ARTICLES OF PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER; WORKING PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER
  • B31F—MECHANICAL WORKING OR DEFORMATION OF PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER
  • B31F2201/00—Mechanical deformation of paper or cardboard without removing material
  • B31F2201/07—Embossing
  • B31F2201/0707—Embossing by tools working continuously
  • B31F2201/0715—The tools being rollers
  • B31F2201/0723—Characteristics of the rollers
  • B31F2201/0725—Hardness
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B31—MAKING ARTICLES OF PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER; WORKING PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER
  • B31F—MECHANICAL WORKING OR DEFORMATION OF PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER
  • B31F2201/00—Mechanical deformation of paper or cardboard without removing material
  • B31F2201/07—Embossing
  • B31F2201/0707—Embossing by tools working continuously
  • B31F2201/0715—The tools being rollers
  • B31F2201/0723—Characteristics of the rollers
  • B31F2201/0728—Material
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B31—MAKING ARTICLES OF PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER; WORKING PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER
  • B31F—MECHANICAL WORKING OR DEFORMATION OF PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER
  • B31F2201/00—Mechanical deformation of paper or cardboard without removing material
  • B31F2201/07—Embossing
  • B31F2201/0707—Embossing by tools working continuously
  • B31F2201/0715—The tools being rollers
  • B31F2201/0723—Characteristics of the rollers
  • B31F2201/0733—Pattern
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B31—MAKING ARTICLES OF PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER; WORKING PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER
  • B31F—MECHANICAL WORKING OR DEFORMATION OF PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER
  • B31F2201/00—Mechanical deformation of paper or cardboard without removing material
  • B31F2201/07—Embossing
  • B31F2201/0707—Embossing by tools working continuously
  • B31F2201/0715—The tools being rollers
  • B31F2201/0753—Roller supporting, positioning, driving means
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B31—MAKING ARTICLES OF PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER; WORKING PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER
  • B31F—MECHANICAL WORKING OR DEFORMATION OF PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER
  • B31F2201/00—Mechanical deformation of paper or cardboard without removing material
  • B31F2201/07—Embossing
  • B31F2201/0756—Characteristics of the incoming material, e.g. creped, embossed, corrugated
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B31—MAKING ARTICLES OF PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER; WORKING PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER
  • B31F—MECHANICAL WORKING OR DEFORMATION OF PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER
  • B31F2201/00—Mechanical deformation of paper or cardboard without removing material
  • B31F2201/07—Embossing
  • B31F2201/0758—Characteristics of the embossed product
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B31—MAKING ARTICLES OF PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER; WORKING PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER
  • B31F—MECHANICAL WORKING OR DEFORMATION OF PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER
  • B31F2201/00—Mechanical deformation of paper or cardboard without removing material
  • B31F2201/07—Embossing
  • B31F2201/0771—Other aspects of the embossing operations
  • B31F2201/0774—Multiple successive embossing operations
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B31—MAKING ARTICLES OF PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER; WORKING PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER
  • B31F—MECHANICAL WORKING OR DEFORMATION OF PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER
  • B31F2201/00—Mechanical deformation of paper or cardboard without removing material
  • B31F2201/07—Embossing
  • B31F2201/0779—Control
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B31—MAKING ARTICLES OF PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER; WORKING PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER
  • B31F—MECHANICAL WORKING OR DEFORMATION OF PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER
  • B31F2201/00—Mechanical deformation of paper or cardboard without removing material
  • B31F2201/07—Embossing
  • B31F2201/0782—Layout of the complete embossing machine, of the embossing line
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B31—MAKING ARTICLES OF PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER; WORKING PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER
  • B31F—MECHANICAL WORKING OR DEFORMATION OF PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER
  • B31F2201/00—Mechanical deformation of paper or cardboard without removing material
  • B31F2201/07—Embossing
  • B31F2201/0784—Auxiliary operations
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H27/00—Special paper not otherwise provided for, e.g. made by multi-step processes
  • D21H27/30—Multi-ply
  • D21H27/40—Multi-ply at least one of the sheets being non-planar, e.g. crêped

Definitions

• the present invention relates to a sheet of absorbent paper made of tissue paper, comprising one or more plies, each having a basis weight of approximately 12 to approximately 70 g/m 2 , and a part of the surface of which is marked. It also relates to a marking process in order to obtain this sheet and to a device for implementing the process.
• the invention finds application in sanitary and domestic papers, such as toilet paper, papers for wiping, such as kitchen paper towel, disposable handkerchiefs, facial tissues or else products of the table range, such as disposable napkins and tablecloths.
• sanitary and domestic papers such as toilet paper
• papers for wiping such as kitchen paper towel, disposable handkerchiefs, facial tissues or else products of the table range, such as disposable napkins and tablecloths.
• the invention allows finishing the tissue paper products.
• marking » as it is used in the following description, consists in compressing certain parts of one side of the sheet, thus forming compacted areas and significantly reducing the thickness of the sheet in these areas without forming a corresponding relief on the opposite side.
• This ply is then brought into contact with another ply, also pre-embossed, in order for the two plies to be adhesively bonded together, connecting them at the contact points or surfaces generated by the embossing.
• an adhesive makes the process particularly tricky and, in fact, it is necessary to take care that the phenomenon of filling does not occur in the conversion installation.
• the adhesive stiffens the sheet in the bonding areas.
• embossing and of creating reliefs increases the roughness of paper surface. Conventional embossing also adversely affects the mechanical properties of strength and elongation and increases the thickness ofthe structure.
• the embossing technique limits the choice of patterns which can be applied on the sheet of absorbent paper. The reason for this is that only patterns which are rounded and devoid of sha ⁇ angles may be used to engrave the embossing surfaces so as in particular to avoid too great a loss of mechanical strength.
• a cellulose cloth for hygiene comprising at least two layers of tissue with , ⁇ n embossed pattern consisting of a plurality of individual spot-shaped impressions which deform and mutually transversely connect the layers of tissue.
• the impressions are formed by embossed spots which originate from the two outer layers of tissue and are curved concavely inwardly in each case and which are mutually transversely aligned and in whose head-to-head base regions the tissue layers are connected to one arother by the embossing action.
• the impressions are applied on both sides.
• the embossing process requires an appropriately precise arrangement and control of the rigid embossing rollers in such a way that the embossed mounds with which the external surface ofthe embossing rollers are provided, are arranged exactly head-to-head in each case but do not touch one another. This process might require a high level of p-ecision and control.
• Watermarks have been used to mark papers, generally in fields quite far removed from those of sanitary and domestic papers.
• a watermark is the impression of a design in the thickness or body of the paper, which is produced intentionnaly in the paper, and is visible when viewed against a contrasting background.
• Watermarking is a very ancient technique and has served since the Xllth and Xlllth centuries to mark sheets, to trace their movement in the market place and to vouch for their provenance.
• watermarks are more conventionally used for papers of low grammage and thickness. They are encountered on paper of the uncoated type, for example letter paper.
• the watermark is termed a « wet » or « true » watermark, when it is produced during the manufacture of the paper in the wet phase of the process, either by means of an impression in the form of reliefs or in the form of depressions in the wire, for example, of the wire mould or of the cylinder mould machine, or by means of an impression in the form of reliefs or depressions at the surface of an open-ended cylinder rotating in contact with the wet pulp on the forming wire of a Fourdrinier former.
• This technique is used for the manufacture of bank notes.
• the design is then obtained by localized displacement ofthe fibers.
• United-States Patent No. 5,328,565 without mentioning watermarks, describes an absorbent paper made of tissue paper comprising a single ply and including surfaces with a non-embossed pattern. This pattern produces regions in the paper having different opacity, height and creping frequency (the number of times a peak appears on the surface for a given distance). The various visually discernible regions forming a particular pattern have different basis weights.
• the pattern is formed directly by the wire during the drying by means of the blowing of air through the sheet in the wet state. After drying, a pattern is certainly formed on the sheet but it does not stand out in contrast with the other areas since the areas with patterns are not actually and clearly visible when viewed against a contrasting background, as conventionally the watermarked patterns aie, and these areas do not have a smooth and glossy appearance.
• the watermark is called a rubber mark (one still speaks of press mirking) when the impression is produced on the paper during its manufacture on the machine by passing the wet web through a roller- whell press.
• An imitation or simulated watermark is an impression similar in a apearance to a true watermark, produced in the finished paper by mechanical means (for example the impression produced on cigarette paper). In this case, the fibres are crushed and compacted.
• the simulated watermark may also be produced by removinj; material or else by applying certain products, such as resin-based substances. Many techniques for producing a simulated watermark on small quantities of finished paper have been developed for replacing the wet watermarking which requires much heavi er and more expensive installations.
• European Patent Application No. 0,195,887 describes a process for producing a watermarking resembling a wet watermark, which means that the paper documents obtained in this way cannot be falsified.
• This process consists in passin 5 a sheet of paper between two rolls rotating in opposite directions, one of the rolls including a pattern and being made of steel. The pattern thus marked is visible when the sheet is held up to the light or by difference in reflection of light on the paper.
• Canadian Patent No. 1,116,851 relates to the surface treatment cf a sheet of paper in order to create a pattern by removal of material.
• the process here consists in passing the sheet of paper between a roll which includes marking patterns and an abrasive roll or else a roll provided with cutters, the two rolls rotating at different speeds.
• the abrasive material or the cutters remove from the sheet of pap « ⁇ a constant thickness of approximately 1/3 to 2/3 of the total thickness of the sheet.
• a simulated watermark is obtained which has a light transmission which is different from that of those parts of the sheet which have not undergone removal of mat .rial. Papers which have undergone this treatment are also unsfalsifiable.
• the simulated watermark may also be produced by impregnating a resin-based composition into a sheet of paper, which makes the sheet translucent in the impregnation areas.
• This technique and compositions which can be usec are widely described in the patent literature, for example British Patent No. 1,489,08 ⁇ and United States Patents No. 3,985,927, No. 4,824,486 and No. 4,919,044.
• simulated watermark is described in Europear Patent No. 0,203,499. This entails a process which consists in preparing a sheet of paper containing a suitable amount of a heat-sensitive material, a polymer ofthe polyethylene type, and in applying heat to part ofthe surface ofthe sheet so as to make that part of the surface ofthe sheet translucent.
• the subject of International Application WO 94/07694 is a device for making a simulated watermark on paper (letterhead paper, certified documents, etc.) by chemical means.
• the simulated watermark is made and the paper is printed preferably in one and the same step. More precisely, this device comprises the combination of coating rolls applying the chemical composition serving for making the simulated watermark with a roll provided with a matrix and an impression cylinder.
• 0,446,138 relates more precisely to a process for manufacturing filter bags which consists, after producing, using a known technique, a non-woven paper composed of a layer based on synthetic fibres and of a layer of cellulosic fibres which are superimposed, in subjecting the non-woven paper to a calendering operation between a support structure, a smooth roll or a roll having an elastic pliant external surface, and a heated roll having reliefs.
• the present invention relates to the application of a pattern or impression resembling a watermarked pattern, to a sheet of absorbent paper made of tissue paper, when that sheet has already been manufactured and dried , which process has hitherto never been employed.
• the watermark applied to the sheet of absorbent paper according to the invention belongs to the category of imitation or simulated watermarks produced on finished paper using mechanical means ; and the term « watermark » used hereafter in the following description of the invention has the above-mentioned meaning.
• the object of the invention is to provide a sheet of absorbent paper, made of tissue paper, which mitigates all the drawbacks mentioned above for sheets of paper of this same kind which have been marked or embossed by processes in the prior art.
• a further object ofthe invention is to provide a sheet of absorbent paper which includes an aesthetic pattern without modifying the thickness of the sheet by removal of material ; or without modifying its mechanical and physical properties ; and in particular without adversely affecting the softness properties of the sheet.
• the invention allows an infinitude of designs to be chosen for the patterns. It provides a matt/gloss contrast effect on the sheet : the marked parts are smooth and glossy and the non-marked parts remain matt and « fluffy cheese The contrast effect can be correlated with the reflection of light.
• the invention also provides a translucent effect ; the marked parts being visible when viewed against a contrasting backgroun .
• the object of the invention is also to connect the two plies together easily.
• Another object of the invention is to provide a process for marking a sheet of absorbent paper made of tissue paper, based on short papermarking fibrfjs, which has neither the problems of the conventional marking processes nor those of the known processes, mentioned above, for watermarking other types of paper ; the watermarking process according to the invention does not use, for example synthetic components.
• the process according to the invention makes it possible to mark the sheet over its entire width unlike the known processes of press marking and of embossing of edges without adhesive bonding by means of steel steel or steel/paper rolls.
• the subject ofthe invention is a sheet of absorbent paper made of tissue paper comprising one or more plies, each having a basis weight of approxi rnately 12 to approximately 70 g/m 2 and part ofthe surface of which is marked.
• the marked surface comprising at least one marked unit region wherein the ratio ofthe thickness to the area of this marked unit region is less than 0.C27.
• the difference between the average grey level ofthe marked surface and the average grey level ofthe unmarked surface is at least 20 by image analysis.
• the sheet comprises at least two plies joined together at the impression resembling the watermarked pattern.
• the subject ofthe invention is also a process for marking a pattern resembling a watermark on a sheet of paper made of tissue paper comprising one cr more plies, each having a basis weight of approximately 12 to approximately 70 g/m 2 , consisting in impressing one side of said sheet without forming a corresponding relief on the other opposite side, by deforming, the said sheet under stress, by at least one pass between a hard engraved roll and a receiving roll having a surface hard less of more than Shore-D 40, the specific pressure exerted on the marked surface being at least 150 kg/cm 2 and the linear marking speed being at least 50 m/min.
• the hardness of the receiving roll is at least Shore-D 80 and preferably greater than Shore-D 90.
• the said engraved roll preferably made of steel, is heated to a temperature ranging from approximately 50°C to approximately 100°C and preferably from approximately 75°C to approximately 85°C.
• the process comprises a preliminary step of treating the sheet before deformation, consisting in bringing the surface of the sheet into contact with small amounts of water in the form of liquid or steam.
• the subject of the invention is also a device for implementing the process, comprising at least one engraved roll, optionally heated, and at least one receiving roll.
• the device comprises one engraved roll optionally heated, arranged between two receiving rolls.
• FIG. 1 represents the surface of a sheet comprising simulated watermarks according to the invention ;
• Figure 2 represents a cross-section of the sheet shown in Figure 1 along the line II-II ;
• Figures 3 A, 3B and 3C represent marked and embossed patterns of the art and impressed patterns according to the invention ;
• FIG. 4 is a schematic diagram of an embodiment of the process according to the invention .
• FIG. 5 represents a device according to one embodiment ofthe invention .
• FIG. 6 represents a device according to another embodiment of the invention .
• FIG. 7 represents a device according to another embodiment of the invention.
• a part of the surface of the sheet is marked by an impressed pattern simulating a watermark.
• the impression is applied to one side or the two sides of the sheet.
• the opposite side corresponding to the applied impression is plane.
• the impression does not form a relief on the corresponding opposite side ofthe sheet.
• a sheet 1 of absorbent paper made of tissue paper includes decorative patterns 2 and 3. These patterns produced in the sheet are simulated watermarks. They are marked in the thickness of the sheet and the lines 5 and 5', or the marking points defining them, are smooth, glossy and translucent to that the patterns are clearly visible when the sheet is viewed against a contrasting background. These lines 5 and 5' form an integral part of the decorative pattern. The papermarking fibres are crushed in the region of the marked surfaces. The pattern is also visible by the impression of relief which it gives the parts ofthe sheet surrounding the pattern, because of the crushing. The sheet is also given a matt/gloss effect.
• the surface parts marked are smooth and glossy and the unmarked remaining parts keep the matt and more fluffy appearance of a conventional non-converted sl eet of tissue paper.
• the marked surface is smooth due to the creped tissue paper sheet elevations which have been reduced or even removed by marking.
• This smooth and glossy aspect advantageously brings out the design of the pattern, enhancing the aesthetic appearance of the sheet. Any design, whether of simple or complex shape, may be envisaged, such as flowers, for example a lotus flower, or calligraphcd words or combinations of lines, strokes and curves defining a pattern. This pattern may occur just once, or more usually, it is repeated.
• the sheet may comprise one or more plies. Each ply has a basis weight lying within the range of approximately 12 to approximately 70 g m 2 . The basis weight preferably lies within the range of approximately 12 to approximately 50 g/m 2 .
• the density ofthe pattern is generally less than 30 per cent.
• Figure 2 shows a cross-section of the sheet 1 comprising two pi ies 6 and 7. The thickness of the sheet is reduced at the place where the marked surface corresponding to the line 5' ofthe pattern of figure 1 is.
• the marked surface area comprises at least one marked unit reg on fullfilling the following requirement.
• the ratio of the thickness of the marked unit region to the area of the marked unit region is less than 0.027.
• the marked surface of the sheet comprises at least one closed impression pattern having a reduced thickness and a minimal surface area. This minimal surface area corresponds to a marked unit region.
• the patterns 3 A limited to a band of diamonds or dashes, parallel to the edge of the sheet, are obtained by « press marking » of a cold and dry sheet of tissue paper.
• the patterns 3B- and 3B 2 illustrate embossed flowers for toilet tissue.
• the patterns 3C ⁇ and 3C 2 represent a tulip and a stylized flower, respectively, and illustrate a simulated watermark pattern according to the invention. Samples of tissue paper sheet have been made with the corresponding patterns 3A, 3B, and 3C according to the marking or embossing process corresponding thereof
• sample sheets of the art comprise two plies
• sample sheets of the invention comprise one, two or three plies
• Patterns 3B and 3C have been splitted up into unit patterns (petals, stems, and leaves) to measure their corresponding unit marked (or embossed) surface areas and adding them to obtain the total pattem marked surface area.
• the thickness reduction is similar between the embossed patterns (3B) and the simulated watermark patterns (3C)
• the average unit marked surface area of the « press marking » samples 3 A is clearly smaller than the average unit marked surface area of the simulated watermark patterns (3C)
• the simulated watermark pattem distinguishes over the « press marking » pattem by comprising at least one marked unit surface having a ratio ofthe thickness thereof to the area thereof of less than 0 027.
• the simulated watermark pattem can comprise marked unit surfaces with a ratio less than 0 027 and other marked unit surfaces with a ratio greater than 0 027 such as small patterns like diamonds, circles, dashes, etc
• the simulated watermark patterns have marked unit surfaces with a ratio which is close to the embossed pattem one, but the obtained sheet is fundamentally different since the embossing technique creates, on part of the surface of eacli of the plies forming the sheet, reliefs with corresponding depressions on the opposii e sides of the plies whereas the simulated watermark pattem corresponds to an impression applied to one side ofthe sheet, the opposite side ofthe sheet being plane without corresponding depressions
• the advantage of the simulated watermark pattem is to provide a decorative pattem similar to an embossed pattem with regard to the design, the si2e thereof and so on, with in addition the simulated watermarked effect
• a further advantage of the simulated watermark pattem is an unlimited choice of decorative patterns without technical restraints, compared with the known « press- marked » or embossed patterns
• Paper tissue sheets according to the invention comp ⁇ sing impressed patterns simulating a watermark, have been analyzed with regard to light transmission
• the method consists of providing a lighting through a sheet sample by the means of optical fibers and a light diffuser, measuring the grey level of an image by th; means of a camera 3 CCD and of a QUANTIMET 600 S LEICA as an image analyzer apparatus
• a surface is delimited
• the image is divided into pixels which correspond to the image units
• Each pixel of that surface has a gi ey level
• the average value of all the pixels ofthe image gives the average grey level oi a surface
• black has a grey level of zero and white has a grey level of 256
• the average grey level of a marked surface is measured by delinking a small closed marked surface area
• the average grey level of an unmarked surface is measured by delimiting a corresponding unmarked surface area closed to the selected marked one And the difference between the two average grey levels is mide
• First tissue paper sheet samples (I) have patterns resulting from the wire during the drying of the sheet in the wet state The papermarking fibers are probably displaced and the pattem regions have different opacity
• the sheet samples (I) comprise two plies and have a total basis weight of approximately 40 g/m 2
• Second tissue paper sheet samples (II) have embossed pattem cor esponding to the pattem 3B 2 of figure 3
• the sheet samples (II) also comp ⁇ se two p ;s and have a total basis weight of approximately 32 g/m 2
• Third tissue paper sheet samples (III) have an embossed pattem corresponding to the stylized flower pattem 3C 2 of figure 3. These samples comprise three plies and have a total basis weight of approximately 52 g/m 2 .
• a tissue paper sheet according to the Figure 1 of the invention is made.
• This tissue paper sheet comprises two plies and has a basis weight of approximately 30 g/m 2 .
• Samples corresponding to the calligraphic LOTUS pattem (la), the lotus flower pattem (lb) and the stroke pattem (lc), have been analysed by image analysis, respectively.
• a tissue paper sheet according to the invention with the stylized flower pattem of Figure 3C 2 is made.
• This tissue paper comprise two plies and has a basis weight of approximately 30 g/m 2 .
• a tissue paper sheet with the same pattem as the one of example 1 is made except that it comprises three plies and has a basis weight of approximately 52 g/m 2 .
• the samples corresponding to the calligraphic LOTUS pattem, the lotus flower pattem and the stroke pattem are numbered 3 a, 3 b and 3 c, respectively.
• a tissue paper sheet with the same pattem as the one of example 2 is made except that is comprises three plies and has a basis weight of approximately 52 g/m 2 .
• a tissue paper sheet according to invention with a tulip pattem of figure 3C] is made. It comprises three plies and has a basis weight of approximately 52 g/m 2 .
• the average grey level is determined for each marked and unmarked surface of every control and example sample.
• Average grey level difference 0 72 52 83 30 41 In view of the above table, same pattem obtained by embossing (control III) and by simulating watermark (example 4) does give none or an average grey level difference, respectively. The light cannot go through the control III with an embossed pattem.
• the embossed tissue paper does not allow the light to make the pattern stand out as a simulated watermark does.
• control I tie pattem of which resulting from a wet end papermaking process A low average grey level difference is observed for control I tie pattem of which resulting from a wet end papermaking process.
• a lower limit of average grey level difference has been defined : 20.
• the average grey level difference of the tissue paper sheet according to the invention is more than 20. It is believed that this characteristic is correlated with the smooth and translucent aspect ofthe simulated watermark disclosed therein.
• the glossy appearance, or brightness of the simulated watermark pattem it is linked to the reflection of light.
• the incident light rays are reflected on the marked pattem surface into one single direction whereas i he same are reflected on the unmarked surface into a plurality of directions by the patches of the tissue paper sheet surface.
• the grey level values by image analysis with a lighting directed onto the sheet surface show the differences between the marked regions which are black and the unmarked regions which are lighter and have a grey level more heterogenous resulting from the surface patches and the fluffy appearence.
• the brightness of the tissue paper has been measured by the means of a mini GLOSSMATER ERICHSEN (Model 507) apparatus.
• the measuring window is a rectangle the area of which is 13 cm 2 .
• the incident lighting has an angle of 60° out of the verticale.
• the weight per cent of reflected light is measured with regard to the surface state ofthe sample.
• the values have been measured on black and white backgrounds.
• the brightness values of the tissue paper with a simulated watermark pattem ⁇ .ccording to the invention are generally higher than the ones of the tissue paper wit I a « press- marking » pattem illustrated by Figure 2, A.
• the two plies 6 and 7 are advantageously bonded or connected together by the watermarked pattem 5'.
• the sheet generally comprises between one and three plies.
• the object of the invention is especially to bond the plies together.
• the quality and appeal ance of the watermark are directly related to the mutual bonding ofthe plies.
• a test is performed to analyze the behaviour of a tissue paper sheet with a simulated watermark pattem according to the figure 3C 2 (samples 1 and 2), comprising three plies, compared with a tissue paper sheet having a simil ⁇ .r embossed pattem (T), comprising three plies.
• the embossing of the control sheet is an ordinary embossing without adhesive. Samples 1 and 2 and T having a width of 50 mm, have been cut.
• the delaminating test consists of measuring the average force of delaminating a sample at an angle of 180° and a constant speed of 100 mm min. There is no value for the samples corresponding to the embossed pattem since the plies divide each other before measuring, in particular between the first two plies. With regard to the samples according to the invention, the average of the plotted values during the continue testing of delaminating is not representative. Only the pic values corresponding to the pattem regions when the plies are bonded, can be inte ⁇ reted.
• the simulated watermark tissue paper sheet according to the invention allows the plies to bond together contrarily to the embossed tissue paper sheet.
• the average thickness of the watermarked sheet has not changed.
• the sheet has kept all its physical and mechanical properties, the strength properties have not decreased and the elongation of the sheet has not been changed. In particular, the softness properties have not been adversely affected.
• the main step in the process for marking with an impressed pattem resembling a watermark, a sheet of absorbent paper made of tissue paper, comprising one or more plies, is the deformation under stress of the sheet by at least one pass between a hard engraved roll and a receiving roll having a hardness of more than Shore-D 40, the specific pressure exerted on the marked or watermarked simulating surface being at least 150 kg/cm 2 and the linear marking speed being at least 50 m/min.
• the sheet makes at least two passes between an engraved roll and a receiving roll.
• the resulting watermark may be distinctly improved by playing with the following parameters.
• receiving rolls having a hardness greater than Shore-D 80 are used.
• Heating the engraved roll also considerably improves the markinj;.
• the heating temperature lies within the interval ranging from approximately 50°C to approximately 100°C and preferably from approximately 75°C to approximately 85°C.
• the sheet Before the sheet undergoes the process, it initially comprises one ore more superimposed and non-connected plies, each stemming from a conventional process for manufacturing absorbent tissue paper and being dried.
• the sheet may or may not be initially creped and/or calendered.
• the sheet may also be impregnated with a softening lotion partly or essentially comprising fatty components.
• the process for marking according to the invention can be done on the papermachine calender when the drying ofthe sheet is completed.
• the process according to the invention is preferably entirely separate from the process for manufacturing the sheet. This is a conversion process closely related to simulated watermarking processes, which may be placed in a unit other than that for manufacturing the sheet.
• the sheet coming from the unwind roll 8 is brought into contact with water.
• water is applied to the sheet in the forrr of steam by passing the sheet over a tank 9 containing water heated to a temperature greater than or equal to the boiling point of water.
• Steam 10 released from the tan comes into contact with the sheet surface which will subsequently undergo the deformation.
• Steam can also be applied with a steam pipe and a nozzle.
• the amount of steam applied is less than approximately 3 per cent by weight of the weight of the sheet and is preferably less than 2 per cent by weight.
• the >team has an effect on the definition and uniformity of the mark or simulated wat ⁇ rmark. It is conceivable that the steam partially penetrates the sheet and acts on the papermarking fibers. Water may also be supplied in liquid form, for example by ⁇ raying fine droplets. The amount supplied is also less than 3, and preferably less than 2, per cent by weight of the weight of the sheet. Likewise, the definition of the simulated watermark is improved by supplying water in liquid form. The next step is the formation proper of the simulated watermark. The sheet 1 then makes a first pass between a steel engraved roll 11 which is hard and a first receiving roll 12, and then a second pass between this same engraved roll 11 and a second receiving roll 13.
• the engraved roll 11 is heated to a temperature which may lie within the range of approximately 50°C to 100°C.
• the heating temperature of this roll is 75°C. It has been observed that increasing the temperature up to 75°C has an influence on the transparency ofthe marked surfaces in the region ofthe patterns.
• the receiving rolls 12 and 13 have a high hardness, greater than Shore-D 80 and preferably greater than Shore-D 90. They may be made of paper, of composite material, or of any other material having this hardness.
• the receiving roll is preferably substantially elastic and deformable under the pressure exerted by the engraved roll. This means that the receiving roll surface tends to take or takes again its original form further to the pressure exerted by the engraved roll.
• the cylinder elasticity is defined herein by the ratio of the energy restored by the cylinder following deformation to the energy that was imparted to it for deformation. This ratio can be determined from hysteresis cycles entailed by consecutive tension and relaxation using a dynamometer or by applying fly-based impact to a test bar.
• Receiving rolls the surface of which have a hardness more than 30 HRC (Rockwell hardness), can be generally used.
• the ceramic material fullfills this hardness characteristic.
• the receiving rolls may also be made of steel for very high hardness. As a matter of fact, these receiving rolls are first elastic and then have a plastic behaviour when a pressure is applied on the surface thereof.
• the hard engraved roll in particular a steel roll, can have a surface hardness which is higher or lower than the receiving roll surface hardness.
• the receiving cylinders may be of the same or different kind.
• Composite materials offer the best results in terms of resistance to mechanical and thermal stresses.
• the specific pressure applied to the patterns or the local specific pressure is at least 150 kg/cm 2 .
• the force applied has been measured during the sheet's pass, under particular test conditions :
• the average specific pressure is calculated and then, from the latter and the surface area occupied by the engraved patterns, the local specific pressure on each pattem is calculated, this being at least 300 kg/cm 2 . Above a local specific pressure of approximately 300 kg/cm 2 it has been found that the bonding ofthe plies and the definition ofthe watermark were; improved.
• impression according to the pattem may be larger or smaller and tests have been carried out for impressions ranging from 4 to 12 millimetres, these values not being limiting.
• the linear marking speed is at least 50 m/min. Maximum speeds of 300 m min have been experimentally tested. However, under suitable conditions, higher theoretical speeds would be conceivable, in particular for new types of cover for the receiving roll, making them more resistant to the stresses exerted.
• the transparency effect may be improved for a given speed by supplying steam or by heating the engraved roll. For example, the effect may be insufficient at a speed of 300 m min with neither steam supply nor heating, whereas the effect is entirely satisfactory it this same speed with an engraved roll heated to 75°C. It has been found that the speed, heat and steam parameters act independently and may be cumulative.
• the sheet may be calendered during the marking process or thereafter.
• the process allows the engraving pattem to be easily changed by replacing the engraved roll in the sheet- conversion installation according to the customer's choice.
• a simulated watermark has been produced on a sheet of absorbent paper which had been impregnated beforehand with a softening lotion. It has been foi nd that the fact of treating the surface of the sheet intending to be marked in no case changed the parameters of the marking process, or the actual simulated watermark on the finished product, whereas in certain processes in the prior art (for example ihe process described in United States Patent No. 4,481,243), the regions intended to be marked or embossed had not to be impregnated with a lotion. The properties of the lotion- impregnated sheet, which has been submitted to a simulated watermarking, were unchanged.
• the subject of the invention is also a device for implementing i he process described above.
• a device comprises at least one engraved roll, optionally heated, and at least one receiving roll.
• This device comprises a steel roll 1 10 which is engraved and optionally heated.
• This roll 110 is arranged between two receiving rolls 120 and 130 which are substantially elastic further to the pressure exerted by the engraved roll 110.
• One of the rolls has a fixed central rotation axis and the other two rolls can move about an axis which is other than their central rotation axis.
• the receiving roll 130 is fixed (its central rotation spindle 135 is fixed) and the roll 110 and 120 can move laterally.
• the roll 130 is fixedly mounted in the stack frame.
• the two rolls 110 and 120 are mounted in cases which are themselves positioned in vertical slideways. Stops are provided for the rolls.
• the upper mechanical stops can prove to be useful in the case of large vibrations.
• the lower stops serve to support the various rolls when the device is not running.
• the compressive force is exerted by the hydraulic rams 140 or by any equivalent means.
• the receiving roll 120 and the engraved roll 110 are applied, by means of pressure, against the receiving roll 130.
• the central cylinder 200 or 300 is the engraved roll and is fixed.
• the other two rolls 201 and 202 or 301 and 302, are movable.
• the rolls 201 and 202 of the device of figure 6 can come into contact with the fixed roll 200 by rotation.
• Two engraved rolls can be contemplated. These engraved rolls can have same or different pattems engraved in their surface. The two impressed pattems can be applied on the same side of the sheet or each pattem is applied on each side, respectively.
• those pattems can preferably be complementary to obtain a complex pattem on the tissue paper sheet.
• the present invention also encompasses tissue paper sheet comprising one or more plies and having on the one hand, pattems obtained by embossing or « press- marking » and, on the other hand, simulated watermark pattems obtained according to the process disclosed in the preceeding description.
• the embossing allo ws the sheet to increase its thickness, and the simulated watermarking allows the sheet to obtain an attractive aesthetic effect.
• the simulated watermarking can be applied before or after the enbossing or press-marking step.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Paper (AREA)
• Laminated Bodies (AREA)
• Sanitary Thin Papers (AREA)
• Absorbent Articles And Supports Therefor (AREA)
• Application Of Or Painting With Fluid Materials (AREA)

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Citations (8)

• 1995
  • 1995-11-30 GB GBGB9524450.5A patent/GB9524450D0/en active Pending
• 1996
  • 1996-11-29 AT AT96938411T patent/ATE212685T1/de not_active IP Right Cessation
  • 1996-11-29 ES ES96938411T patent/ES2171741T3/es not_active Expired - Lifetime
  • 1996-11-29 EP EP96938411A patent/EP0864014B1/en not_active Revoked
  • 1996-11-29 TR TR1998/00942T patent/TR199800942T2/xx unknown
  • 1996-11-29 DE DE69618983T patent/DE69618983T2/de not_active Revoked
  • 1996-11-29 PT PT96938411T patent/PT864014E/pt unknown
  • 1996-11-29 WO PCT/IB1996/001326 patent/WO1997020107A1/en not_active Application Discontinuation
  • 1996-11-29 DK DK96938411T patent/DK0864014T3/da active

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