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
  • D21F1/0027—Screen-cloths

Definitions

• This invention relates to the production of wet-felted fiberboard having a textured surface. It relates more particularly to the texturing of a fiberboard surface before the mat is fully de-watered. It relates still more particularly to the creation of a pattern on a fiber felting screen.
• the fiberboard is processed further to form acoustical ceiling tiles or panels, wall panels, and the like. It is often desirable to impart a pleasing texture to such products for esthetic reasons, and, to some extent, for improved acoustical properties.
• Methods known for imparting a texture include the patterned sandblasting of the dried fiberboard, rough screeding of the partially de-watered slurry of fibers, and pressing of the wet mat under a solid press roll having the reverse of the desired pattern in the metal.
• the sandblasting procedure must be very carefully controlled and it is wasteful of the eroded material.
• the screeding procedure is limited as to the number of distinctive patterns that can be formed.
• the solid press rolls do not achieve high fidelity in the reproduction of the pattern.
• the removal of water from the slurry of fibers is accomplished not only by free drainage through the felting wire near the headbox and by vacuum during passage over the suction boxes but also by vacuum as the slurry passes under a series of suction press rolls mounted above the bottom wire and mated with a series of rolls which contact the bottom wire.
• the top suction press, rolls are perforated cylinders, each having a vacuum slice which is stationary but mounted within the perforated cylinder in slidable contact with the inner wall.
• the top wire of the Fourdrinier forms a continuous loop around the set of suction rolls.
• suction rolls are used only to consolidate the slurry and smooth its surface.
• this invention is a method for forming a texturing pattern on a fiber felting screen, said method c ⁇ nprising casting a positive mold of a texture pattern having a miltiplicity of cavities, coating the mold with a release agent, spreading a resin precursor over the mold to fill the cavities, partially curing the resin precursor to form a convex meniscus above each cavity, pressing a fiber felting screen into the resin precursor protruding from the cavities, curing the resin, and separating the screen and the negative mold bonded thereto from the positive mold.
• FIG. 1 is a cross section of a positive mold of a texturing pattern having a partially cured resin precursor in the mold cavities.
• FIG. 2 is a cross section of the positive mold of FIG. 1 on which a fiber felting screen is laid.
• FIG. 3 is a cross-section of positive mold immediately after having a resin precursor distributed over the surface of the mold and into the mold cavities.
• FIG. 5 is a cross section of a fiber felting screen to which a negative mold of the texturing pattern has been bonded by the method of this invention.
• FIG. 6 is an enlarged view of a portion of the screen in FIG. 5.
• the positive mold 10 has a body 11 which is surrounded by the frame 12.
• the body 11 and the frame 12 are coated with a mold release agent; alternatively one or both may be formed from a silicone rubber or a like material which will not adhere to a cured resin.
• the cavities 13 are of irregular shapes and are randomly placed according to the pattern chosen for the textured fiberboard to be produced on a Fourdrinier machine equipped with the top wire of this invention.
• the ridges 14 are substantially flat so that the convex meniscus 15 of partially cured resin 16 in each cavity 13 protrudes beyond them.
• the screen 17 is pressed against the mold 10 so that the partially cured resin precursor 16 is forced into the voids of the screen wherever a meniscus 15 rises from a cavity 13.
• the mounds 18 of resin precursor are generated by spreading the uncured resin precursor over the mold with a serrated trowel or the like.
• the cohesive forces within the precursor exceed the adhesive forces between the mold and the precursor and as a result the mounds disappear quickly as the precursor creeps away from the ridges 14 and gathers to form the convex menisci 15.
• a layer of the resin precursor may be spread across the mold 10 by a straightedge, distribution by a serrated trowel or the like is preferred because the thickness of the layer can be more accurately gauged and the mounds 18 seem to provide pathways to the cavities 13.
• An initially even layer of precursor may creep haphazardly along the ridges 14 without finding a cavity and form nodes of partially cured resin which would block out more than just the textured portions of the screen, thus reducing the porosity.
• the screen 17 is bonded to the cured resin at the dots 20 from which the nodules 21 extend.
• the screen 19 is a negative of the pattern which is to be impressed on wet mat of fibers during the production of a textured fiberboard on a Fourdrinier or similar machine.
• the partial curing of the resin precursor has reached the proper state for placement of the fiber felting screen on the mold when the resinous liquid will hold a peak for about 60 seconds. By this time, the low viscosity liquid will have crawled on the mold, creating the convex meniscus in each mold detail.
• the resin precursor is the reaction mixture in a two-part resin system. It is preferable that the polymerization, i.e., curing, takes place at from about 65° to about 90°F (18°-32°C) and at atmospheric pressure. It is essential that the resin precursor be such that the cohesive forces therein are greater than the adhesive forces with respect to the surface of the mold.
• Polyurethane and epoxy resins exemplify the two-part resin contemplated for use in the method of this invention.
• the mold release agent is exemplified by a silicone resin such as is sold under the trademark KRAKO 1711 by Eager Plastics; other examples of the release agent include waxes, fluoroplastics, metallic stearates, fatty amides, and polyethylene.
• a dilute solution, suspension or emulsion of the release agent may be brushed or sprayed onto the mold and allowed to penetrate the crevices and cavities therein. Upon evaporation of the vehicle, a thin film of the release agent remains on the mold.
• the liber felting screen may be a woven mesh of metal wires or plastic fibers.
• a double or triple weaved mesh is preferred because the extra thickness provides more space for the vertical distribution of excess resin as opposed to a horizontal spreading of the resin which would reduce the porosity of the texturing screen.
• a plastic screen is preferred because its flexibility provides for better contact with the mold. To ensure such contact, the screen is pressed down onto the surface of the mold by a uniformly distributed weight exerting a pressure of at least about 0.5 psi.
• the weight may be supplied by a water-filled plastic bag or some other suitable means.
• the plastic bag or other weight must be coated with a mold release agent also to prevent adhesion of the cured resin to the weight when the weight is removed from the screen.

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• 1986
  • 1986-03-04 EP EP19860902148 patent/EP0215904A4/fr not_active Withdrawn
  • 1986-03-04 WO PCT/US1986/000492 patent/WO1986005220A1/fr not_active Application Discontinuation
  • 1986-03-04 JP JP50167786A patent/JPS62502127A/ja active Pending
  • 1986-10-16 DK DK494586A patent/DK494586D0/da not_active Application Discontinuation

Patent Citations (3)

Non-Patent Citations (1)

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