US3575707A - Method of cost coating paper - Google Patents

Method of cost coating paper Download PDF

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Publication number
US3575707A
US3575707A US779115A US3575707DA US3575707A US 3575707 A US3575707 A US 3575707A US 779115 A US779115 A US 779115A US 3575707D A US3575707D A US 3575707DA US 3575707 A US3575707 A US 3575707A
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United States
Prior art keywords
coating
web
water
moisture content
coated
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Expired - Lifetime
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US779115A
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English (en)
Inventor
Theodor Ploetz
Bruno Hagg
Wolfgang Barnscheidt
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Feldmuehle AG
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Feldmuehle AG
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    • 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

Definitions

  • This invention relates to coated papers and other coated, glossy webs of fibrous material, and particularly to the cast coating of paper and related products.
  • paper carrying a soft coating composition whose essential ingredients are a liquid carrier, normally water, an inorganic pigment and a binder for the pigment dispersed in the Water, is pressed with its coated face against a smooth solid surface, and dried.
  • the dried coating duplicates the surface finish of the contacted surface.
  • An object of the invention is the provision of a method for cast coating paper and other webs of fibrous material which is simple, inexpensive and capable of being performed at high output rates on machinery of relatively modest dimensions.
  • the invention resides in an improvement in the known method of coating a Web of fibrous material briefly described above in which one face of the web is covered with a coating composition essentially consisting of a volatile liquid carrier, such as Water, an inorganic pigment, and a binder for the pigment, the pigment and the binder being dispersed in the carrier.
  • a coating composition essentially consisting of a volatile liquid carrier, such as Water, an inorganic pigment, and a binder for the pigment, the pigment and the binder being dispersed in the carrier.
  • the moist coating so produced is pre-dried to remove a major portion of the water, and an amount of Water sufiicient to soften the dried coating is thereafter applied to the same.
  • the softened coating is held in contact with a smooth, non-adherent surface under sufiicient pressure to smoothen the coating, and the Water is substantially completely removed from the smoothened coating.
  • the removal of the carrier from the smoothened coating can be performed in a fraction of the time required heretofore if the pre-drying step of the moist coating is controlled in such a manner that the web and the coating are overdried until the residual water content of the coated web is substantially lower than the equilibrium moisture content of the coated web under the usual standard conditions of 73 F. and 50 per cent relative humidity and the coating is hardened.
  • the amount of water used thereafter for softening the coating is not substantially greater than the amount of applied water required to make the combined moisture content of the web and of the coating equal to the equilibrium moisture content.
  • the amount of water can be held to a minimum when the water is applied only to the coating. and moistening of the overdried web is prevented.
  • a web 2 of uncoated cardboard is drawn from a supply reel 4 over guide rollers 6, 8 to a supporting roller 10 on which one face of the web is covered with a coating composition discharged from an airbrush 12.
  • the coated web then travels through a drying zone equipped with two gas-fired infrared heaters 14, 16.
  • the radiation emitted from the first heater 14 is directed toward the uncoated face of the web 2, whereas infrared radiation from the second heater 16 is directed against the coated face.
  • the dried coating then passes under a bank 18 of spray nozzles which apply water to the coating before the coated web enters the nip between two driven cylinders 20, 22.
  • the unheated cylnder 20 has a rubber facing and the cylinder 22 a highly polished, chromium plated surface. It is heated with steam supplied through non-illustrated hollow trunnions, as is conventional.
  • the coated web 2 is trained over approximately of the circumference of the cylinder 22, and the hot material is festooned over guide rollers in a cooling zone 24 before being wound on a take-up reel 26.
  • the base stock 2 was cardboard 220 cm. wide having a weight of 220 g. per m. It traveled at a speed of 60 meters per minute.
  • the coating composition consisted of water and 45% solids as follows (in weight percent of total solids):
  • Acronal 500 is a commercially available copolymer of acrylic and vinyl polymers (BASF).
  • the base stock was coated with the above composition at a rate to make the weight of the applied coating solids approximately g./m.
  • the first infrared heater 14 had an efiective length of 3 meters in the direction of web travel, the second heater 16 a length of 5 meters.
  • the residual moisture in the cardboard was approximately 1 percent after passing the second heater.
  • the equally overdried coating was uniformly sprayed with water containing O.51% non-ionic wetting agent (a commercial mixture of fatty alcohol polyglycol ethers: Dehypon) at a rate of 8 g./m.
  • non-ionic wetting agent a commercial mixture of fatty alcohol polyglycol ethers: Dehypon
  • the distance between the second heater 16 and the bank 18 of spray nozzles was too short for absorption of significant moisture by the web from the ambient atmosphere, and the nip between the cylinders 20, 22 was so close to the nozzles 18 that there was no significant evaporation of the applied water.
  • the rubber facing of the pressure cylinder 20 had a hardness of to Shore, and the external diam eter of the cylinder was cm.
  • the polished smoothing cylinder 22 had a diameter of cm., and its cylindrical surface was kept at a temperature of 120 C. by means of superheated steam.
  • the web 2 covered with a white coating free from defects was spontaneously released from the hot cylinder surface prior to cooling and reeling.
  • the coating surface had a whiteness of 83% as measured with a Zeiss instrument (Elrepho), and the gloss readings obtained on a Zeiss goniophotometer were 118 and 74 based on a barium sulfate reference standard.
  • the equilibrium moisture of fibrous material suitable for use in the method of the invention generally varies between 2 to 10 percent, and may even be higher, depending on the fiber composition, the higher end of this range being typical of ordinary paper stock.
  • the fibrous material When overdried as described above, the fibrous material will not normally contain more than 1% moisture. Practically all coating compositions now commercially employed for cast coating are soft enough during smoothing at elevated temperature when remoistened with water at a rate of 1 to 12 g., a rate of 4 to 10 g./m. being generally most favor able.
  • a typical heavy paper or cardboard having a total Weight of 200 g./m. and a moisture content of 1% when overdried, has a total moisture content of 5% when remoistened with 8 g. water per square meter prior to smoothing a value well below the equilibrium moisture content.
  • roller coating may replace the spraying specifically referred to in the preceding example of a preferred embodiment, and other methods are available to those skilled in the art.
  • the successful operation of the method requires very careful balancing of operating variables when the moisture content of the coated web is not reduced to 3% or less during overdrying, regardless of the equilibrium moisture of the material, and infrared radiant heaters have been found to provide adequate removal of water from the moist coating and the supporting web at the high rate necessary if the drying zone is not to become excessively long.
  • the invention does not rely on evaporation of water from the coated web, and the time of contact between the coated material and the heated smoothing drum may thus be very short.
  • the plant more specifically described above operates at a speed which is many times higher than that of known apparatus used in a conventional manner and having cylinders of twice the diameters.
  • the small amount of steam, if any, generated in the instant method on the smoothing cylinder does not tend to accumulate at the interface of the coating and of the cylinder, and thus need not be overcome by high mechanical pressure. It does not tend to disrupt the bond between the coating and the base stock, and the coating composition thus need not include hardeners, and all conventional cast coating compositions are suitable for the instant method.
  • a coating composition essentially consisting of water, an inorganic pigment, and a hinder, the pigment and the binder being dispersed in the water; the moist coating so produced is dried to remove a major portion of the water; an amount of water sufficient to soften the dried coating is applied to the same; and the softened coating is held in contact with a hot, smooth, non-adherent surface under sufiicient pressure to smoothen the applied coating until the water is substantially completely removed from the smoothened coating; the improvement which comprises:
  • said web being continuous and being coated while moving, the softened coating being held in contact with said surface under said pressure by moving the same between two moving members, one of said members having said surface, the other member having a face more resilient and softer than said surface, the temperature of said face being lower than the temperature of said surface, said face engaging said web.
  • said members being cylinders rotating about respective axes, the diameter of said other member being at least one-third of the diameter of said one member, and said face being sufficiently soft to cause a circumferential portion of said face to become concavely arcuate under said pressure for conforming engagement with said web while the coating conformingly engages said surface, the circumferential length of said concave portion being sufficient for holding said web in contact with said portion until at least onehalf of said moisture content of the softened coating is absorbed by said paper or cardboard.

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  • Paper (AREA)
US779115A 1967-11-27 1968-11-26 Method of cost coating paper Expired - Lifetime US3575707A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP7607267A JPS5335162B1 (enrdf_load_stackoverflow) 1967-11-27 1967-11-27

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US3575707A true US3575707A (en) 1971-04-20

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US779115A Expired - Lifetime US3575707A (en) 1967-11-27 1968-11-26 Method of cost coating paper

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JP (1) JPS5335162B1 (enrdf_load_stackoverflow)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3911180A (en) * 1971-10-15 1975-10-07 Fuji Photo Film Co Ltd Method of making a resin coated paper having a smooth surface
US3963843A (en) * 1972-12-20 1976-06-15 Domtar Limited Production of coated paper
DE2603155A1 (de) * 1975-01-31 1976-08-05 Star Paper Ltd Gussgestrichenes papier, seine herstellung und streichmassen
EP0290194A1 (en) * 1987-04-30 1988-11-09 Kanzaki Paper Manufacturing Company Limited Method of producing cast coated paper
EP0120095A4 (en) * 1982-09-28 2003-12-17 Kanzaki Paper Mfg Co Ltd Method of manufacturing cast-coated paper
DE102022112687A1 (de) 2022-05-20 2023-11-23 Voith Patent Gmbh Verfahren und Maschine zur Erhöhung der Querdehnung einer Testliner-Papierbahn in Hochgeschwindigkeits-Papiermaschinen

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3911180A (en) * 1971-10-15 1975-10-07 Fuji Photo Film Co Ltd Method of making a resin coated paper having a smooth surface
US3963843A (en) * 1972-12-20 1976-06-15 Domtar Limited Production of coated paper
DE2603155A1 (de) * 1975-01-31 1976-08-05 Star Paper Ltd Gussgestrichenes papier, seine herstellung und streichmassen
US4048380A (en) * 1975-01-31 1977-09-13 Star Paper Limited Cast coated paper and its production and compositions for it
DK149029C (da) * 1975-01-31 1990-06-25 Star Paper Ltd Fremgangsmåde ved fremstilling af en støbebelægning på et substrat af papir, pap eller karton
EP0120095A4 (en) * 1982-09-28 2003-12-17 Kanzaki Paper Mfg Co Ltd Method of manufacturing cast-coated paper
EP0290194A1 (en) * 1987-04-30 1988-11-09 Kanzaki Paper Manufacturing Company Limited Method of producing cast coated paper
US4900583A (en) * 1987-04-30 1990-02-13 Kanzaki Paper Mfg. Co., Ltd. Method of producing cast coated paper using near-infrared radiation
DE102022112687A1 (de) 2022-05-20 2023-11-23 Voith Patent Gmbh Verfahren und Maschine zur Erhöhung der Querdehnung einer Testliner-Papierbahn in Hochgeschwindigkeits-Papiermaschinen

Also Published As

Publication number Publication date
JPS5335162B1 (enrdf_load_stackoverflow) 1978-09-26

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