Classifications

• • 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
  • D21H25/00—After-treatment of paper not provided for in groups D21H17/00 - D21H23/00
  • D21H25/08—Rearranging applied substances, e.g. metering, smoothing; Removing excess material
  • D21H25/12—Rearranging applied substances, e.g. metering, smoothing; Removing excess material with an essentially cylindrical body, e.g. roll or rod
  • D21H25/14—Rearranging applied substances, e.g. metering, smoothing; Removing excess material with an essentially cylindrical body, e.g. roll or rod the body being a casting drum, a heated roll or a calender
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21G—CALENDERS; ACCESSORIES FOR PAPER-MAKING MACHINES
  • D21G9/00—Other accessories for paper-making machines
  • D21G9/009—Apparatus for glaze-coating paper webs
• • 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
  • D21H19/00—Coated paper; Coating material
  • D21H19/36—Coatings with pigments
  • D21H19/44—Coatings with pigments characterised by the other ingredients, e.g. the binder or dispersing agent
• • 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
  • D21H19/00—Coated paper; Coating material
  • D21H19/80—Paper comprising more than one coating
  • D21H19/82—Paper comprising more than one coating superposed

Definitions

• This invention relates to a process for the production of mineral-coated paper having a high gloss of the kind commonly called cast-surfaced coated paper.
• mineral-coated paper we mean paper bearing a coating consisting essentially of a mineral pigment and a hydrophilic adhesive.
• Cast-surfaced mineral-coated paper was first described in Bradner Patent No. 1,719,166, issued July 2, 1929. Since that time several minor variations in procedure have been made public, all of which yield products generally similar in appearance to that described in said Bradner patent. All known methods of producing castsurfaced coated paper are similar to the extent that in all cases a coated surface of the paper is set while in adherent contact with a finishing surface such as a polished chromium-plated cylinder or drum, from which the coated surface separates with a finish substantially mirroring the finishing surface.
• a finishing surface such as a polished chromium-plated cylinder or drum
• U. S. Patent No. 2,568,288 to Montgomery discloses a method of preventing sticking. According to this patent there is maintained on the finishing surface an invisible film, substantially less than 2000 Angstrom units in thickness, of an oil or other fatty material, such substances being designated as oleaginous film-forming material. The film has to be maintained at a critical thickness not great enough to prevent adhesion of the wet coated surface to the finishing surface but still thick enough to prevent sticking of the dry coated surface to the finishing surface.
• the preferred method of maintaining the film is to include in the aqueous mineral coating composition with which the paper is coated a quantity of the oleaginous release agent generally amounting to between 0.1 and 1.0% of the dry weight of the coating. Enough of the oleaginous material is adsorbed on the finishing surface from the wet coating composition to make up for the quantity which the dried coating takes away and thus the oleaginous film is maintained.
• Patent 2,568,288 requires very close and constant observation with adjustment of the oleaginous ingredient in the coating composition to maintain the film at the desired thickness. Any increase in the thickness of the oleaginous film over the minimum required for satisfactory release causes a corresponding diminution in the gloss of the finished coated paper. Even a moderate increase in the thickness of the oleaginous film may cause a mottled appearance of the finished coated paper and may leave sufficient grease on the surface of the coated paper both to make the paper distasteful to handle and to produce scumming on a printing press when the paper is printed.
• Another object is to provide a release agent for cast surfaced coated paper which when used in excess of the minimum quantity required for release does not cause diminution of gloss of the finished coated paper.
• Another object is to provide a release agent for use in making cast-surfaced coated paper which release agent substantially all leaves the finishing surface and becomes or remains a part of the cast surface of the coated paper.
• Another object is to provide a method of imparting various desirable functional qualities to cast-surfaced coated paper without detracting from the glossiness thereof.
• the preferred release agents for use according to the invention are normally solid resinous materials which are soluble, either molecularly or colloidally, in aqueous 'media which contain dissolved alkali or other agent to solvate this resinous material.
• Such resinous release agents are particularly adapted for use in producing castsurfaced coated paper by the modern processes in which a layer of coating already formed on a paper base is brought into contact with a finishing surface while both the layer of coating and the finishing surface are bathed in aqueous medium.
• Patent No. 2,678,890 a freshly applied but already formed layer of coating on a paper web is brought, before it has dried, into contact with a heated finishing surface, e. g. a polished chromium plated drum, while the line of contact i. e. the nip between the coated surface and the finishing surface is kept flooded to a depth of A to 2 inches with aqueous medium substantially free from suspended solids.
• a heated finishing surface e. g. a polished chromium plated drum
• Patent No. 2,759,847 discloses a process by which paper is coated, dried, and super-calendered, and then the densified supercalendered surface is passed through a pool of aqueous medium substantially free from suspended solids and into contact with a heated finishing surface, against which it is dried as in Patent No. 2,678,890.
• the product yielded by this process appears identical with prior art cast-surfaced coated papers but the product, due to its having been previously supercalendered, possesses other desirable properties not obtainable previously in cast-surfaced coated papers.
• the resinous release agents of the present invention are as efiicacious in promoting clean release of dry cast-surfaced coated paper from a casting or finishing surface as are the oleaginous release agents of the prior art but it is believed that the resinous release agents must effect release by a mechanism which is different from that of the greasy agents.
• Oleaginous release agents as is well known, must, for best results, be used in amount not far above the minimum quantity which will effect release, since only a slight increase over the minimum quantity will result in a decrease in gloss of the dried coated surface, and a considerable increase may not only entirely prevent formation of a cast surface but if continued in use may actually build up into a visible film of grease on the finishing surface.
• Resins suitable for use under the invention are resins which are soluble in water containing ammonia, caustic soda, or similar alkali. Rosin, shellac and Manila copal are examples of such resins. Synthetic resins soluble in the presence of alkali: are also usable. An example of such a synthetic resin, is. synthetics A-56, an adduct of maleic anhydride and pentaerythritol ester of rosin sold by Hercules Powder Company. synthetics A-56 is soluble in aqueous ammonia and in aqueous caustic soda. it is a desirable non-oleaginous release agent which is effective in promoting release of dried cast-surfaced coated paper from a finishing surface when applied in aqueous solution to the surface of the coating prior to contact of the latter with said finishing surface.
• the absolute minimum of resinous material required to effect release of the dry coated paper surface from the finishing surface may vary depending upon several factors, including the specific resinous material, the particular coating composition, and the particular finishing surface being used. Generally speaking, application to the surface of the coated paper of an aqueous solution conraining from 0.25 to 0.50 percent of resinous release agent in quantity suflicient to form a continuous film of solution on said surface is adequate to ensure satisfactory release of the dry coated surface from the finishing surface.
• the quantity of resinous release agent deposited per unit of area of the coated paper is, as will be apparent from the foregoing description, quite variable. If all other conditions which might result in variation of the quantity of release agent deposited on the paper surface are disregarded or considered to be non-variable it appears that the amount of release agent deposited per unit of area may vary in the same ratio as the concentration of the solution applied i. e. from .25 to 25.
• the principal variable factors aside from the concentration of the solution which may result in variation of the amount of release agent deposited are (1) the viscosity of the solution of the release agent (2) the pressure at the nip (3) the smoothness or texture of the coated surface being treated and (4) the density of the release agent. We have calculated that the weight of release agent deposited on the cast-surface coated paper may vary within the range from 0.01 to several pounds per 1080 square feet.
• the resin solution may be applied to the paper coating by any means which will deposit a film thereof on said surface, for instance by spraying or the resin solution may be applied by passing the coated paper into contact with the finishing surface in such a way that a V shaped pocket is formed by the paper and the finishing surfce adjacent the nip and this pocket is kept flooded With resin solution to a suitable depth e. g. V4 to 2 inches.
• the resin solution may be applied to the paper in advance of the nip in quantity sufficient to flood the nip with resin solution or resin solution may be applied to the paper in advance of the nip in quantity only sufficient to form a film on the surface thereof but insufficient to flood the ni in this event the nip may remain free of any pool of liquid. or it may he flooded with resin solution fer ⁇ thereto directly, or it may be flooded with water or aqueous liquid free of resin.
• a flooded nip i. e.
• a nip which is flooded with water or resin solution or any of the other aqueous liquid which is free of suspended solids.
• the flooded nip is in fact practically essential when the coated paper to which the resin solution is applied is one which has been dried and calendered and is dry at the point at which the resin solution is applied because the aqueous liquid in the nip serves to rewet and replasticize the surface of the coating and enable it to be deformed sufliciently by contact with the finishing surface to yield in effect a cast surface.
• the flooded nip may however be not used if suflicient resin solution is applied to the coated paper ahead of the nip to moisten and plasticize the surface thereof.
• Process for cast-coating paper which comprises applying to a paper base a layer of aqueous coating composition comprising finely divided mineral pigment and hydrophilic adhesive, wetting the surface of the layer of coating with a release agent comprising an alkaline aqueous solution of a normally solid resin, thereafter pressing the coated surface while still in a wet and plastic condition into adherent contact with a heated finishing surface, and drying the coating in contact with said finishing surface until it no longer adheres thereto.
• aqueous solution is a solution of a resinate of an alkali metal.
• aqueous solution is a solution of an ammonium resinate.

Landscapes

• Paper (AREA)
• Cigarettes, Filters, And Manufacturing Of Filters (AREA)
• Application Of Or Painting With Fluid Materials (AREA)

Priority Applications (5)

Applications Claiming Priority (1)

Publications (1)

Family

ID=23531418

Family Applications (1)

Country Status (5)

Cited By (8)

Citations (5)

Family Cites Families (3)

• 0
  • BE BE531889D patent/BE531889A/xx unknown
• 1953
  • 1953-10-22 US US387804A patent/US2819184A/en not_active Expired - Lifetime
• 1954
  • 1954-09-14 FR FR1112176D patent/FR1112176A/fr not_active Expired
  • 1954-10-21 DE DEW15134A patent/DE1007165B/de active Pending
  • 1954-10-22 GB GB30475/54A patent/GB769460A/en not_active Expired

Patent Citations (5)

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