Classifications

• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
  • D21F11/00—Processes for making continuous lengths of paper, or of cardboard, or of wet web for fibre board production, on paper-making machines
  • D21F11/006—Making patterned paper
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
  • D21F1/00—Wet end of machines for making continuous webs of paper
  • D21F1/44—Watermarking devices

Definitions

• the present invention relates to a method for marking a flexible structure, the marked flexible structure thus obtained and its use in a method for marking a cellulosic sheet.
• Another way to mark the basket is to emboss the sheet still wet, before or in the dryer of the machine, using knurling wheels watermarks or a marker felt marker, exerting a mechanical effect on the sheet and thus leaving an imprint by modifying the relief.
• rods are simply formed by parallel lines giving the paper a laid appearance. They are obtained with the aid of a frictional marker with a particular weaving of parallel longitudinal lines.
• the plaintiffs therefore sought a means of obtaining, without modifying the machines and the methods of manufacturing felts, various patterns in size, shape and arrangement, on the surface of a cellulosic sheet.
• the present invention therefore relates to a flexible structure which can be likened to a joinable or endless belt, marked by an engraving or printing process.
• the flexible structure can be a paper machine drying cloth or a felt usable in the wet part such as a coating felt, or even a drying felt or else a vellum or orchard friction felt.
• the felt can be a woven, non-woven structure or a combination of the two, composed of natural fibers, synthetic fibers or their mixtures.
• the flexible structure can also be a canvas composed of synthetic and / or metallic threads.
• a mixed felt of natural fibers such as wool
• synthetic fibers such as polyamide, polyester fibers or acrylic fibers.
• non-woven felt mention may be made of a needled felt such as a 100% synthetic felt made of polyester fibers.
• the marked friction felt according to the invention can be a felt having a uniform texture making it possible to obtain a paper of vellum appearance or may also have a particular weaving, for example of parallel longitudinal lines giving the paper a laid appearance.
• the flexible structure according to the invention is obtained by a method of marking by etching, that is to say removal of material or densification or by printing or coating, that is to say surface addition of material.
• the invention therefore also relates to the method of marking a flexible structure mentioned above.
• the etching process can be a densification process by pressure or fusion or both jointly or by removal of material; it can therefore be a mechanical, chemical or thermal process, the latter being carried out using a heated form, applied with pressure, at a temperature above the melting temperature of at least one of the constituents of the flexible structure.
• the marking process of the flexible structure can also be a printing or coating process, that is to say a superficial addition of material, by stencil printing-coating, serigraphy, transfer or any other means making it possible to apply the selected patterns to the surface of the flexible structure, with good definition.
• the flexible structure has a relief on the face opposite to the mark, this will be locally or uniformly removed by application of material identical to or different from that used for marking.
• the material or materials used for printing these patterns are chosen to be resistant to hydrolysis in the medium slightly acidic or slightly basic, resistant to the constraints of temperature, pressure, deformation and abrasion, resulting from the manufacturing process of the cellulosic sheet. Furthermore, these materials must be flexible enough to follow without breaking or altering the curvatures of the felt or the canvas in its continuous path in the paper machine. These materials must also adhere perfectly to the natural and / or synthetic fibers of the flexible structure and be durably linked to them.
• these materials are chosen from thermoplastic, thermosetting or elastomeric synthetic resins.
• the resins chosen must not creep or melt at a temperature below 140 ° C.
• the materials which can be used are classified in particular among polyolefinic, polyvinyl, halogenated polyolefin, polystyrene, polyesters, polyurethanes, silicones or elastomers of styrene-butadiene, butadiene-acrylonitrile or polychloroprene resins.
• the resin used is applied in the molten state or in the state of a self-crosslinking aqueous dispersion (latex) or in solution in a solvent or in the pure state, in the form of '' a paste with one or more components.
• the preparation used for marking the flexible structure may contain any additives making it possible to adjust the viscosity or itself. confer the particular properties sought, such as antioxidants, vulcanizing agents, dyes, mineral or organic pigments, etc.
• the preferred resins according to the invention, for use in marking the flexible structure are polyurethane resins.
• the polyurethanes used can be in the form of reactive or thermoplastic mixtures, in 100% paste, in one-component aqueous dispersion or in one-component or two-component solution in an organic solvent.
• the present invention also relates to the use of the marked flexible structure thus obtained, in a process for marking a cellulosic sheet.
• the cellulosic sheet may be a cardboard or a paper intended for printing, writing, packaging or any other processing use such as impregnation, coating, laminating on sheet or film, polyolefin extrusion-coating, etc.
• a cellulosic sheet is made using as main raw material for example, combinations of softwood pulp and hardwood pulp treated with soda or bisulfite, bleached or semi-bleached.
• the raw material used is preferably unbleached softwood pulp obtained by the sulphate process.
• the paper may also contain in its composition other types of fibers and papermaking adjuvants, commonly used and known to those skilled in the art.
• the paper marking process according to the invention is implemented by pressing the marked flexible structure defined above against the sheet of paper, thus allowing the marks to be transferred onto the latter.
• a preferred application of the marked flexible structure according to the invention is its application to a method for marking unbleached brown kraft paper.
• the marks carried by the frictionneur, vergeur or plain texture felt reproduce on the sheet of paper by pressing the felt against the non-friction side of the sheet, at the time of its application against the said drying cylinder.
• Marking of intaglio letters is carried out on a sample of coating felt of composition 100% polyamide fibers.
• a wet sheet is drawn from an unbleached pine kraft paste refined at 23 ° SR, for a final grammage after drying, of approximately 70 g / m2. This sheet is pressed against the previous marked felt, to a final dryness of 33% and then dried in contact with the same felt, in the Rapid-Köthen dryer.
• the sheet resulting from the formette in the preceding test is previously pressed by passing through a cylinder press, under a linear pressure of 12 kg / cm.
• a mark is thus obtained having an average allowance of approximately 1mm.
• a layer of the same resin is applied to the back of the felt using a doctor blade.
• This felt is installed in a combined paper machine as a friction felt, the marked side being applied against the sheet of paper in contact with the Yankee drying cylinder.
• An unbleached kraft paper is made from a maritime pine pulp, refined at a SR of 25, to which 3 kg / t of resin soap and aluminum sulphate for a pH of 4 have been added, 8 in the fibrous suspension at the machine head.
• the marker felt is pressed against the sheet of paper then having a dryness of 60%, by a friction press under a linear pressure of 100 kg / cm.
• the sheet On leaving the Yankee cylinder, the sheet has a residual water content of 7.2% and an average grammage of 50 g / m2.

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Applications Claiming Priority (2)

Publications (1)

Family

ID=9381021

Family Applications (1)

Country Status (5)

Cited By (10)

Citations (8)

• 1989
  • 1989-04-21 FR FR8905365A patent/FR2646181B1/fr not_active Expired - Fee Related
• 1990
  • 1990-04-19 EP EP90401066A patent/EP0394134A1/fr not_active Withdrawn
  • 1990-04-19 NO NO90901724A patent/NO901724L/no unknown
  • 1990-04-20 PT PT93826A patent/PT93826A/pt not_active Application Discontinuation
  • 1990-04-20 FI FI901978A patent/FI901978A0/fi not_active IP Right Cessation

Patent Citations (8)

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