EP0794286B1 - Composition de couchage du papier - Google Patents

Composition de couchage du papier Download PDF

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Publication number
EP0794286B1
EP0794286B1 EP19960301627 EP96301627A EP0794286B1 EP 0794286 B1 EP0794286 B1 EP 0794286B1 EP 19960301627 EP19960301627 EP 19960301627 EP 96301627 A EP96301627 A EP 96301627A EP 0794286 B1 EP0794286 B1 EP 0794286B1
Authority
EP
European Patent Office
Prior art keywords
group
coating
sodium
viscosity
additives
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP19960301627
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German (de)
English (en)
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EP0794286A1 (fr
Inventor
Michael L. Dematte
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
WestRock MWV LLC
Original Assignee
Westvaco Corp
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Filing date
Publication date
Application filed by Westvaco Corp filed Critical Westvaco Corp
Priority to EP19960301627 priority Critical patent/EP0794286B1/fr
Publication of EP0794286A1 publication Critical patent/EP0794286A1/fr
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Publication of EP0794286B1 publication Critical patent/EP0794286B1/fr
Anticipated expiration legal-status Critical
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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
    • 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
    • D21H19/46—Non-macromolecular organic compounds

Definitions

  • the present invention relates to coating papers suitable for printing. More particularly, the present invention relates to an improved coating formulation and application method characterized by improved healing properties. Most particularly, the invention relates to an improved coating formulation comprising, as a lubricant therefor, a sulfated oleic acid.
  • Coatings are applied to paper stock for the purpose of providing an improved surface suitable for printing.
  • High quality coated paper for printing must meet a number of requirements dictated by the nature of the printing process. Thus, the requirements are somewhat different depending on whether the printing is to be done by offset, gravure, or letterpress methods.
  • paper for offset printing generally must have higher moisture resistance than paper for letterpress or gravure printing because the paper is moistened incident to the offset printing process.
  • coated printing paper must be smooth and level, dimensionally stable, strong, moisture resistant, resistant to "picking" or pulling up of coating or fibers by contact with a tacky inked surface, and, above all, it must accept ink uniformly without absorbing it excessively.
  • such properties as opacity, gloss,'and color are imparted by the coating: requirements for these vary widely depending on the desired appearance of the finished printed matter but they must be uniform throughout a particular stock.
  • An uncoated paper surface is not completely smooth but contains higher and lower areas since the thickness of the felted cellulose fibers varies from point to point. The magnitude of these variations in thickness is reduced by the smoothing effect of calendering. However, if the paper is again moistened with water, the cellulose fibers tend to swell and "spring back," increasing the magnitude of the variations. To create a smooth and level printing surface, the coating must fill in all of the low areas of the paper, while, to provide a uniform surface for ink reception, the coating must also cover the fibers in the high areas. When a paper is moistened by application of an aqueous coating, the magnitude of the surface irregularities is increased, and a larger amount of coating must be applied to create a uniform surface.
  • a high solids content (absent excessive scratching) produces a higher quality coating. Also, a reduction in coating formulation solvent content can reduce production costs significantly, not just in reduced formulation costs but the reduced drying time increases production rate and saves energy costs.
  • the above stated objectives are achieved by incorporating in the coating formulation, as a lubricant, a sulfated oleic acid.
  • the sulfated oleic acid containing coating formulation is characterized by improved healing properties and permits coating at higher solids levels over formulations containing prior art lubricants when applied to the paper with blade coaters.
  • a paper coating formulation comprising a scratch-healing additive and one or more additives selected from the group consisting of mineral pigments, adhesives, dispersants, lubricants, insolubilizers, viscosity-reducing additives and viscosity-increasing additives; characterised in that the coating has a solids content of greater than 60%, in that the scratch-healing additive is sulfated oleic acid, and in that the viscosity-increasing additives are selected from the group consisting of sodium alginate, sodium carboxy methylcellulose, and hydroxy ethylcellulose.
  • a method of applying a coating formulation comprising a scratch-healing additive and one or more additives selected from the group consisting of mineral pigments, adhesives, dispersants, lubricants, insolubilizers, viscosity-reducing additives and viscosity-increasing additives, on to paper employing blade applicators, characterised in that the coating has a solids content of greater than 60%, in that the scratch-healing additive is sulfated oleic acid, and in that the viscosity-increasing additives are selected from the group consisting of sodium alginate, sodium carboxy methylcellulose, and hydroxy ethylcellulose.
  • the major coating additives are the various pigments. These pigments improve surface smoothness and uniformity. They also contribute to increased brightness, opacity and gloss for appearance, and to reduced ink showthrough.
  • Major pigments utilized include hydrous kaolin coating clays, fine calcined clay, trihydrated alumina, calcium carbonate, and titanium dioxide.
  • Dispersants promote and maintain the separation of individual pigment particles. This group of additives reduces coating viscosities, enhances coating flow during the application process and contributes to improved coating lay on the base sheet.
  • Typical products utilized include pentasodium tripolyphosphate, tetrasodium pyrophosphate, sodium tetraphosphate, casein, sodium silicate and sodium salts of carboxylic acids. Selection of a dispersant is largely determined by the type of pigments utilized in a specific coating color.
  • Coating lubricants also improve coating flow properties, coating lay, surface finish and product printability. They reduce the tendency of coating to crack, and they prevent dusting in the paper finishing operation.
  • Typical additives include sodium stearate, calcium stearate, sulfonated oils, and polyethylene emulsions.
  • Insolubilizers are incorporated in coating colors to improve water resistance. These additives reduce the sensitivity of the adhesives to water and generally improve the wet rub resistance of the coating. Urea resins, such as urea-formaldehyde, melamine resins, such as melamine-formaldehyde, and glyoxal are typical additives used for this end-use requirement.
  • Viscosity-reducing additives control, lower and stabilize the viscosity of adhesives or pigments in the wet coating prior to application.
  • Typical additives include urea, dicyandiamide, and ethylenediamine. They are important from the standpoint of maintaining uniform flow properties in the coating operation. Viscosity-increasing additives build viscosity into coatings where the primary binder is latex. Additives such as sodium carboxy methylcellulose, which is also an adhesive, increase viscosity to improve runnability, coating lay, and uniformity of deposition. Other such additives include sodium alginate (such as Kelgin®) and hydroxy ethylcellulose (HEC).
  • Paper coatings are generally applied by blade coating or roll coating.
  • Roll coaters usually are not subject to the type of wear in operation which results in the creation of the type scratching of the coating that the invention coating formulation is designed to heal. Nevertheless, the improved flow properties provided by the invention improvements are beneficial to roll coating operations as well.
  • the invention coating formulations and methods are designed primarily to aid blade coating processes.
  • the blade doctors off excess coating that has been picked up in the applicator pan.
  • the blades usually are tilted toward the incoming web.
  • blades are thin, only 0.2-0.5 mm thick, and can be rigid or flexible (of spring steel). Blades wear fast and have to be changed relatively often, perhaps 2-4 times a day. Blades are always pressed against the web, which is supported by a backing roll. Wear of the blade results in nicks and other deformatives to the edge contacting the coating which induces visible scratches which, in turn, results in poor coating.
  • the present invention coating formulations and methods provide a solution to the scratching problem which avoid increased use of water.
  • the scratch healing benefits of the invention are such that improved coatings are provided economically with higher solids formulations.
  • Sulfated tall oil fatty acid is known to be used as an additive in paper coating formulations and is believed to promote coating leveling. Several years ago it was surmised that sulfate tall oil fatty acid could be substituted for the calcium stearate additive in a particular commercial formulation. In appreciation of the fact that the sulfated tall oil fatty acid acts as a water-holding agent, it was hypothesized that the additive may allow healing of coating scratches by maintaining coating fluidity. The results of the experiments conducted are shown in Example 1.
  • PC-60 tall oil fatty acid
  • the coating formulation control used for evaluations is shown in Table I. Ingredients Parts Pigment 100 Protein 2 PVAC 16 Kelgin® MV 0.103 Ca Stearate 1.7 The control formulation exhibited a Brookfield viscosity of 2600 cps, a Hercules 1st Pass of 37, and 2nd Pass of 35.
  • PC-60 is not particularly compatible with Kelgin® and Alcogum® thickeners, but it is quite compatible with hydroxyethyl cellulose (HEC, Natrosol) and carboxymethyl cellulose (CMC). Therefore, appropriate substitutions were made in the experimental formulations to account for such incompatibilities.
  • the coatings were based on the standard top coat formulation in Table I, except that coating 2 was thickened with HEC instead of Kelgin® and had no lubricant, coating 3 used HEC and calcium stearate (C-104), coating 4 used HEC and PC-60, and coating 5 used PC-60 with a lower than usual amount of Kelgin®.
  • the common substrate coated in the tests was a mill-base-coated board produced at Westvaco's Covington, Virginia bleached board mill.
  • the coatings were applied using a benchtop coater in pond-blade mode with the minimum loading required for runnability.
  • the coater was run at 9.14 meters (30 feet) per minute with hot air drying.
  • the time from the blade to drying was about two seconds (as compared to ⁇ 0.5 second on a paper machine).
  • the coating scratch was induced by means of a pin placed immediately after the blade. Photomicrographs of the scratches were made at a magnification of 64 diameters. The widths of the scratches were measured.
  • the C 104 coating was 63.2% solids, 4080 cps Brookfield viscosity and 64.6 cps Hercules high shear viscosity.
  • the WVSRTM coating was 63.0% solids, 4000 cps Brookfield viscosity and 55.6 cps Hercules viscosity.
  • the sequence of blade pressure application 15, 9.1, 11.3, 13.6, 2.7 and 4.5 kg per 2.5 linear centimeters (20, 25, 30, 6, and 10 pounds per linear inch, pli). Some scratches at low pressures may be residual from higher blade pressure.
  • the lower high shear viscosity for coatings containing the sulfated oleic acid could be advantageous not only in reducing coating scratching but also may have potential to improve print quality.
  • Print quality often can be improved by increasing coating solids. This is because, at higher coating solids, less coating and binder strikes into the board result in a more uniform, continuous coating layer. Since the normal limitation on coating solids is coating scratches, the lower high shear viscosity may allow higher coating solids to be run on the blade coater.

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  • Paper (AREA)

Claims (14)

  1. Formulation pour le couchage de papier comprenant un additif réparant les rayures et un ou plusieurs additifs choisis dans le groupe constitué par les pigments minéraux, les adhésifs, les dispersants, les lubrifiants, les agents insolubilisants, les additifs réduisant la viscosité et les additifs augmentant la viscosité ;
       caractérisée en ce que le couchage a un taux de matière solides supérieur à 60 %, en ce que l'additif réparant les rayures est un acide oléique sulfaté et en ce que les additifs augmentant la viscosité sont choisis dans le groupe constitué par l'alginate de sodium, la carboxyméthylcellulose sodique, et l'hydroxyéthylcellulose.
  2. Formulation pour le couchage de papier selon la revendication 1, caractérisée en ce que les pigments minéraux sont choisis dans le groupe constitué par l'argile pour couchage, l'argile fine calcinée, l'alumine trihydratée, le carbonate de calcium et le dioxyde de titane.
  3. Formulation pour le couchage de papier selon la revendication 1 ou 2, caractérisée en ce que les adhésifs sont choisis dans le groupe constitué par l'amidon, la caséine, le latex, l'alcool polyvinylique, la carboxyméthylcellulose sodique et l'hydroxyéthylcellulose.
  4. Formulation pour le couchage de papier selon la revendication 1, 2 ou 3, caractérisée en ce que les dispersants sont choisis dans le groupe constitué par le pyrophosphate tétrasodique, le tripolyphosphate pentasodique, le tétraphosphate sodique, le silicate de sodium, la caséine et les sels de sodium d'acides carboxyliques.
  5. Formulation pour le couchage de papier selon la revendication 1, 2, 3 ou 4, caractérisée en ce que les lubrifiants sont choisis dans le groupe constitué par le stéarate de sodium, le stéarate de calcium, les huiles sulfonées, l'acide gras de tallol sulfaté et les émulsions de polyéthylène.
  6. Formulation pour le couchage de papier selon l'une quelconque des revendications précédentes, caractérisée en ce que les agents insolubilisants sont choisis dans le groupe constitué par les résines d'urée, les résines mélamine, le glyoxal, les composés du zinc, le formaldéhyde et la diméthylolurée.
  7. Formulation pour le couchage de papier selon l'une quelconque des revendications précédentes, caractérisée en ce que les additifs réduisant la viscosité sont choisis dans le groupe constitué par l'urée, le dicyandiamide et l'éthylènediamine.
  8. Méthode d'application d'une formulation pour couchage comprenant un additif réparant les rayures et un ou plusieurs additifs choisis dans le groupe constitué par les pigments minéraux, les adhésifs, les dispersants, les lubrifiants, les agents insolubilisants, les additifs réduisant la viscosité et les additifs augmentant la viscosité, sur du papier en utilisant des applicateurs à lames, caractérisée en ce que le couchage a un taux de matière solides supérieur à 60 %, en ce que l'additif réparant les rayures est un acide oléique sulfaté et en ce que les additifs augmentant la viscosité sont choisis dans le groupe constitué par l'alginate de sodium, la carboxyméthylcellulose sodique, et l'hydroxyéthylcellulose.
  9. Méthode selon la revendication 8, caractérisée en ce que les pigments minéraux sont choisis dans le groupe constitué par l'argile pour couchage, l'argile fine calcinée, l'alumine trihydratée, le carbonate de calcium et le dioxyde de titane.
  10. Méthode selon la revendication 8 ou 9, caractérisée en ce que les adhésifs sont choisis dans le groupe constitué par l'amidon, la caséine, le latex, l'alcool polyvinylique, la carboxyméthylcellulose sodique et l'hydroxyéthylcellulose.
  11. Méthode selon la revendication 8, 9 ou 10, caractérisée en ce que les dispersants sont choisis dans le groupe constitué par le pyrophosphate tétrasodique, le tripolyphosphate pentasodique, le tétraphosphate sodique, le silicate de sodium, la caséine et les sels de sodium d'acides carboxyliques.
  12. Méthode selon la revendication 8, 9, 10 ou 11, caractérisée en ce que les lubrifiants sont choisis dans le groupe constitué par le stéarate de sodium, le stéarate de calcium, les huiles sulfonées, l'acide gras de tallol sulfaté et les émulsions de polyéthylène.
  13. Méthode selon la revendication 8, 9, 10, 11 ou 12, caractérisée en ce que les agents insolubilisants sont choisis dans le groupe constitué par les résines d'urée, les résines mélamine, le glyoxal, les composés du zinc, le formaldéhyde et la diméthylolurée.
  14. Méthode selon la revendication 8, 9, 10, 11, 12 ou 13, caractérisée en ce que les additifs réduisant la viscosité sont choisis dans le groupe constitué par l'urée, le dicyandiamide et l'éthylènediamine.
EP19960301627 1996-03-08 1996-03-08 Composition de couchage du papier Expired - Lifetime EP0794286B1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP19960301627 EP0794286B1 (fr) 1996-03-08 1996-03-08 Composition de couchage du papier

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP19960301627 EP0794286B1 (fr) 1996-03-08 1996-03-08 Composition de couchage du papier

Publications (2)

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EP0794286A1 EP0794286A1 (fr) 1997-09-10
EP0794286B1 true EP0794286B1 (fr) 2003-06-25

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EP19960301627 Expired - Lifetime EP0794286B1 (fr) 1996-03-08 1996-03-08 Composition de couchage du papier

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Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4012543A (en) * 1969-06-25 1977-03-15 Scott Paper Company Coated paper and method of making same
US4676836A (en) * 1984-10-16 1987-06-30 Diamond Shamrock Chemicals Company Anionic Lubricant dispersions useful in paper coatings
US5500191A (en) * 1994-10-26 1996-03-19 Westvaco Corporation Paper coating composition

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