US3462290A - Curtain coating process and apparatus - Google Patents

Curtain coating process and apparatus Download PDF

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Publication number
US3462290A
US3462290A US539046A US3462290DA US3462290A US 3462290 A US3462290 A US 3462290A US 539046 A US539046 A US 539046A US 3462290D A US3462290D A US 3462290DA US 3462290 A US3462290 A US 3462290A
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US
United States
Prior art keywords
coating
substrate
roll
curtain
temperature
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
US539046A
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English (en)
Inventor
Herman J Kresse
Joe F Alix
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.)
ConocoPhillips Co
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Continental Oil Co
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Publication date
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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B3/00—Ohmic-resistance heating
    • H05B3/62—Heating elements specially adapted for furnaces
    • H05B3/64—Heating elements specially adapted for furnaces using ribbon, rod, or wire heater
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D1/00—Processes for applying liquids or other fluent materials
    • B05D1/30—Processes for applying liquids or other fluent materials performed by gravity only, i.e. flow coating
    • B05D1/305—Curtain coating
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D1/00—Processes for applying liquids or other fluent materials
    • B05D1/40—Distributing applied liquids or other fluent materials by members moving relatively to surface
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D3/00—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials
    • B05D3/007—After-treatment
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D2252/00—Sheets
    • B05D2252/02—Sheets of indefinite length
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S118/00—Coating apparatus
    • Y10S118/04—Curtain coater

Definitions

  • FIG. 2 CURTAIN COATING PROCESS AND APPARATUS Filed March 31, 1966 COATING HEAD 7 ⁇ i FALLING Fll-M RESILIENT ROLL COLLECTOR m DEGASSER AND L BACK TO MELT RESERVOIR FIG. 2
  • This invention relates to applying a hot melt coating to at least one surface of a substrate.
  • this invention relates to curtain coaters.
  • this invention relates to an improved method of applying a hot melt to a substrate.
  • hot melts When applied to the coating of certain solid substrate materials with hot viscous liquids, such as molten Wax, molten synthetic resins, and blends of wax with synthetic resins (generally referred to as hot melts), most coating procedures are characterized in varying degree by a number of disadvantages. Among such disadvantages there may be mentioned: waste or uneconomical use of the coating material, decrease in flexibility of the substrate as a result of coating, and failure of the coating technique to successfully apply a smooth continuous coating which is free from cracks, bubbles, pinholes, blisters and the like.
  • the curtain coater process has been developed to applying such hot melt coatings to substrates.
  • the stock to be coated is passed through a gravitating or falling curtain or film of the coating medium so that the coating medium impinges upon the exposed surface of the stock and is deposited thereon as a thin, relatively uniform film.
  • the excess coating material which is not deposited on the stock is collected in a suitable receiving container and, preferably, degassed and cycled to the point of origin of the gravitating curtain for reuse.
  • the stock is preheated prior to coating; however, with relatively thin stocks such as cellophane, and similar thin plastic sheets, this is generally not required.
  • the hot melt must be cooled below the tacky point prior to rolling the stock to prevent sticking.
  • the stock itself can be the source of the gas bubbles, e.g., a small amount of moisture; also, a small amount of air can be entrapped at the point of impingement.
  • the degassed hot melt may give an apparently uniform, hole-free coating, the coating may not actually adhere uniformly and thus the coating will break subsequent to the coating.
  • porous substrates steam formed by moisture or other gas will pass through the substrate, whereas with semi-porous 3,462,290 Patented Aug. 19, 1969 substrates, the gas flow meets with suificient pressure to be a source of potential diificulty. This is illustrated by clay-backed substrates. It has been found that little or no trouble is encountered when using the degassed hot melt to the coated side of the substrate.
  • Another object of this invention is to provide a method for improving the adhesion of coatings to substrates.
  • Another object of this invention is to provide a method for flattening bubbles and closing of craters, pinholes and ruptures formed by applying hot melts to substrates with a curtain coater.
  • Another object of this invention is to provide a method for maintaining the flatness of thin substrates after applying hot melts to the surface thereof.
  • Still another object of this invention is to improve heat transfer at the chill roll following application of hot melt to substrates, and still other objects, features and advantages of this invention will be apparent to those skilled in the art having been given this disclosure and the appended claims.
  • the substrates to which this invention is of particular usefulness are impervious substrates such as metallic foils, i.e., aluminum foil, etc., plastic sheets such as cellophane, polyethylene and other polymer and copolymer flexible sheeting materials and semi-pervious sheets such as clay-backed and lacquerbacked papers, pouch paper, greaseproof paper, glassine paper and the like.
  • the coating materials to which this invention is particularly useful are hot melts which are subject to applying to substrates, e.g., a falling curtain as utilized in a curtain coater.
  • These materials are waxes, wax-copolymer blends and the like. In general, these materials have an inherent viscosity at 250 F. in the range of 15,000 to 100,000 cps.
  • a typical wax-copolymer blend would be a hydrocarbon high melting wax with butyl rubber, or ethylene-vinylacetate copolymer.
  • melts are known in the art, and are not a part of this invention.
  • the apparatus by which the present invention is practiced in one embodiment comprises a curtain coating device which can be of conventional type and which functions to provide a gravitating or downwardly propelled curtain or film of the coating composition; a conveyor system or means for moving the substrate stock to be coated through the gravitating curtain of the coating composition and a means for cooling the stock after coating.
  • the curtain coater will have conduit means for collecting and recycling to the curtain coating device all the excess coating composition which is not deposited upon the stock; means for preheating the stock when so desired and means for removing gas from the coating composition.
  • An important feature of a preferred embodiment of the apparatus used in the practice of the present invention is a pressure roll in cooperation with the means for cooling so as to press the film against the stock as it passes over the cooling means.
  • the cooling means intermediate the curtain coater and the reroller will comprise a chill roll and a pressure roll so arranged that the pressure roll is held in contact with the stock as it passes over the cooling roll.
  • the pressure roll will have a resilient surface such as rubber or high melting plastic, e.g., butadiene, styrene copolymers, high melting point polyethylene or polyvinylchloride, copolymers of these with copolymerizable monomers or polyvinylfluorides such as Teflon.
  • humidifying means for adding sufiicient moisture to the stock to be coated to prevent excessive dehydration of the stock and fiber embrittlement in those cases where the stock is preheated prior to the application of the coating thereto.
  • the coating material useful in this invention is any hot melt suitable for use in a falling film or curtain coater.
  • these materials are mixtures of paraffin and/ or microcrystalline wax with a compatible resin.
  • the melt is such a wax with an ethylene-vinylacetate copolymer, e.g., 30% wax and 70% copolymer of 80% ethylene with 20% vinylacetate.
  • Other polymers and copolymers are sometimes used such as polyethylene, polystyrene, polybutadiene, butadiene-styrene copolymer, vinylchloride and its copolymer.
  • the blend or melt will form a free-flowing film at the extrusion temperature which should be low enough so that the substrate is not damaged at the point of contact.
  • any melt having a viscosity in the range of 15,000 to 100,000 cps. at 250 F. can be used.
  • 250 F. is the reference temperature
  • the coater reservoir or extrusion temperature will generally be higher than this, e.g., 270 to 400 F.
  • the actual viscosity will be halved.
  • the film viscosity would be about 25,000 centipoises.
  • the pressure in a curtain coater extruder or film former ranges generally from 5 to 20 p.s.i.g.
  • the falling film flows upon the substrate to be coated, and the excess runs off, is collected, degassed and returned to the film former where the temperature and pressure desired for the particular melt is maintained.
  • the substrate then passes over a chill roll wherein the coated material is cooled to a temperature wherein it is no longer tacky, and the coated substrate can then be rerolled on the reroller.
  • the chiller is ordinarily cooled with refrigerated water; however, with some hot melts, a lower temperature may be required and some other cooling medium such as alcohol or ethylene glycol can be employed. The amount of cooling required is such that the coated material can be rerolled without sticking.
  • the temperature of the chill -roll will be dependent upon the nature of the melt, the speed of the substrate, the surface area (heat transfer surface) of the chill roll and the like. In general, this temperature varies from 5 to 150 F. All of the above is known in the art as used in the coating industry not only with curtain waters, but coaters in general, and no detailed description is deemed necessary in this specification.
  • the temperature of the coating as it enters the nip between the pressure roll and the chill roll should be such that the coating material has set sufficiently that it will not rupture as the gas bubbles are compressed and yet retain sufficient adhesion properties to adhere to the substrate when bubbles and the like are forced by the pressure roll against the substrate.
  • this temperature will be dependent upon the nature of the coating and the substrate, and each individual case will have its own range which can readily be determined by the skilled operator. This temperature will generally range from about to F., but is not necessarily limited thereto.
  • This temperature can be regulated by controlling the temperature of the substrate and the falling film temperature and the feed rate of the substrate. This feed rate generally will vary from about 200 ft.
  • a prechill roll can be used to control the temperature of the coating at the nip.
  • the prechill roll also serves a useful purpose where the substrate has been previously coated on the reverse side, e.g., with thermoplastic lacquer or hot melt, in that the hot curtain can soften the underside of the substrate and the prechill -roll serves to resolidify this reverse side coating and prevent its being marred by the pressure roll.
  • FIGURE 1 is a schematic illustration of a conventional curtain coater incorporating a resilient pressure roll
  • FIGURE 2 is a schematic of such a curtain coater utilizing a prechill roll.
  • FIGURE 3 is a schematic illustration of an embodiment of the invention wherein the chill roll is also utilized for prechill.
  • substrate 2. from supply roll 1 is passed over rollers 3, 4 and 5 under coating head 6 which has an elongated nozzle at its lower end so as to provide a falling film or curtain 7 which impinges on the substrate 2 thus coating same.
  • Excess coating material from curtain 7 falls over the sides of the substrate into overflow collector 8 and is passed via conduit 9 back through a degasser (not shown) to the melt reservoir (not shown).
  • This reservoir is equipped with suitable means for maintaining the desired temperature, e.g., internal heating coils or jacket, and a pump for delivering coating material to the coating head 6 at a controlled rate.
  • an agitator can be provided as is known in the art.
  • the coated substrate then passes through the nip 15 between a pressure roller 10 (preferably having a resilient surface) and chill roller 11 and over rollers 12 and 13 to rewind, not shown.
  • a pressure roller 10 preferably having a resilient surface
  • chill roller 11 over rollers 12 and 13 to rewind, not shown.
  • a prechill roller 14 is put ahead of rollers 10 and 11, otherwise the operation and description is the same as FIGURE 1, and the same numbers are used to illustrate the corresponding parts.
  • the pressure between the pressure roll and chill roll can vary over a wide range, say from 10 lbs./in. of nip to 500 lbs./in. of nip and preferably from 25 to 150 lbs. per inch of nip.
  • the substrate after passing the gravitating film passes over roller 16 and back around chill roll 11 and then between the nip formed by chill roll 11 and resilient pressure roll 10.
  • the chill roll serves as prechill as well as final chill.
  • the remaining rollers are numbered as in FIGURE 1 and only so much of this embodiment is shown as to illustrate the modification.
  • the pressure between the rubber roll 10 and chill roll 11 was 50 pounds per inch of nip.
  • the resilient or rubber roll 10 had a rubber surface of 70 Shore A hardness.
  • the chill roll was of metal finish.
  • the coating composition was a mixture of parafiin wax and ethylene-vinyl-acetate copolymer. The mixture was varied to obtain the desired viscosity at 250 F.
  • Substrate Aluminum foil-pouch stock laminate, coating foil side.
  • Web feed rate 800 f.p.m. (feet per minute).
  • the coating contained visible bubbles.
  • the pressure roll at 50 lbs/inch, the bubbles were flattened and the general appearance of the coating was much improved. The flattened portions appeared to have adhered to the substrate.
  • Coating weight 10.5 lbs/3000 ft.
  • the coating was rough and had many air inclusions between the film and substrate. The coating was easily abraded over the air inclusions.
  • the coating was smooth and of good appearance. Adhesion and resistance to abrasion was greatly improved.
  • Substrate 30# clay-coated bleached kraft, coating nonclay side.
  • Coating weight 9.9 lbs/3000 ft.
  • Coating weight 38.7 lbs/3000 ft.
  • rollers shown can vary and that the passage of the coated substrate between the nip of the resilient and chill roll can vary from that shown, e.g., the substrate need not pass over the resilient roll, but by placing the chill roll on top and the resilient roll below, the substrate could pass directly to the nip 15.
  • Other changes can be made by those skilled in the art without departing from the scope and spirit of the invention. While all of the cylindrical surfaces have been described as rollers, it is obvious that low friction stationary bars can also be used.
  • a hot melt is gravitated as a film upon a substrate to be coated and said substrate is continuously passed beneath the gravitating film and over a chill rodd spaced downstream from said gravitating film
  • the improvement comprising a pressure roll in alignment with said chill roll and adjacent said roll and exerting a pressure upon said chill roll and so aligned that said substrate with the resulting film passes between the nip formed between said chill roll and said pressure roll with the coated side of said substrate in contact with said chill roll and the underside of said substrate is in contact with said pressure roll.

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US539046A 1966-03-31 1966-03-31 Curtain coating process and apparatus Expired - Lifetime US3462290A (en)

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US (1) US3462290A (fr)
BE (1) BE709695A (fr)
FR (1) FR1511838A (fr)
GB (1) GB1123636A (fr)
NL (1) NL6701880A (fr)
SE (1) SE306897B (fr)

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4577585A (en) * 1984-04-23 1986-03-25 Anselmo Anthony G Method and apparatus for making a color blended wall covering
US5447753A (en) * 1991-06-07 1995-09-05 Nippon Paper Industries Co., Ltd. Method of manufacturing coated paper for printing
US5611859A (en) * 1995-06-07 1997-03-18 Kimberly-Clark Corporation Apparatus for coating a strip of paper
US5795320A (en) * 1995-06-07 1998-08-18 Kimberly-Clark Worldwide, Inc. Paper applicator containing a compostable coating
WO1998047630A1 (fr) * 1997-04-21 1998-10-29 Bachofen + Meier Ag Maschinenfabrik Procede et dispositif pour appliquer des dispersions sur une bande de materiau
US5984888A (en) * 1995-06-07 1999-11-16 Kimberly-Clark Worldwide, Inc. Applicator and coating
WO2001053004A2 (fr) * 2000-01-24 2001-07-26 Weirton Steel Corporation Bande metallique enduite de polymere et procede de production de celle-ci
US20130030399A1 (en) * 2005-04-29 2013-01-31 The Procter & Gamble Company Polymeric film exhibiting improved anti-blocking characteristics and process of making
CN112452613A (zh) * 2020-11-23 2021-03-09 北京燕山电子设备厂 玄武岩纤维混纺涂层布生产设备、方法

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2443222A (en) * 1945-02-23 1948-06-15 Robert Morris Bergstein Process for waxing paper
US2753275A (en) * 1952-02-05 1956-07-03 Marathon Corp Method of continuously coating paper with wax and resultant product
US2882182A (en) * 1955-08-30 1959-04-14 Sun Oil Co Method of preparing a wax coated fibrous sheet material
US3218212A (en) * 1960-06-14 1965-11-16 Union Carbide Corp Method of and apparatus for forming a clear glossy laminate
US3284228A (en) * 1962-02-14 1966-11-08 Tetra Pak Ab Method of rendering polyolefine surfaces non-adherent
US3308006A (en) * 1961-10-19 1967-03-07 Continental Oil Co Laminated corrugated paper board
US3376244A (en) * 1964-10-30 1968-04-02 Chevron Res Polypropylene wax film

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2443222A (en) * 1945-02-23 1948-06-15 Robert Morris Bergstein Process for waxing paper
US2753275A (en) * 1952-02-05 1956-07-03 Marathon Corp Method of continuously coating paper with wax and resultant product
US2882182A (en) * 1955-08-30 1959-04-14 Sun Oil Co Method of preparing a wax coated fibrous sheet material
US3218212A (en) * 1960-06-14 1965-11-16 Union Carbide Corp Method of and apparatus for forming a clear glossy laminate
US3308006A (en) * 1961-10-19 1967-03-07 Continental Oil Co Laminated corrugated paper board
US3284228A (en) * 1962-02-14 1966-11-08 Tetra Pak Ab Method of rendering polyolefine surfaces non-adherent
US3376244A (en) * 1964-10-30 1968-04-02 Chevron Res Polypropylene wax film

Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4577585A (en) * 1984-04-23 1986-03-25 Anselmo Anthony G Method and apparatus for making a color blended wall covering
US5447753A (en) * 1991-06-07 1995-09-05 Nippon Paper Industries Co., Ltd. Method of manufacturing coated paper for printing
US5611859A (en) * 1995-06-07 1997-03-18 Kimberly-Clark Corporation Apparatus for coating a strip of paper
US5795320A (en) * 1995-06-07 1998-08-18 Kimberly-Clark Worldwide, Inc. Paper applicator containing a compostable coating
US5984888A (en) * 1995-06-07 1999-11-16 Kimberly-Clark Worldwide, Inc. Applicator and coating
WO1998047630A1 (fr) * 1997-04-21 1998-10-29 Bachofen + Meier Ag Maschinenfabrik Procede et dispositif pour appliquer des dispersions sur une bande de materiau
WO2001053004A2 (fr) * 2000-01-24 2001-07-26 Weirton Steel Corporation Bande metallique enduite de polymere et procede de production de celle-ci
WO2001053004A3 (fr) * 2000-01-24 2002-01-10 Weirton Steel Corp Bande metallique enduite de polymere et procede de production de celle-ci
US20130030399A1 (en) * 2005-04-29 2013-01-31 The Procter & Gamble Company Polymeric film exhibiting improved anti-blocking characteristics and process of making
US9096731B2 (en) * 2005-04-29 2015-08-04 The Procter & Gamble Company Polymeric film exhibiting improved anti-blocking characteristics and process of making
US20150314490A1 (en) * 2005-04-29 2015-11-05 The Procter & Gamble Company Polymeric Film Exhibiting Improved Anti-Blocking Characteristics and Process of Making
US9637603B2 (en) * 2005-04-29 2017-05-02 The Procter & Gamble Company Polymeric film exhibiting improved anti-blocking characteristics and process of making
CN112452613A (zh) * 2020-11-23 2021-03-09 北京燕山电子设备厂 玄武岩纤维混纺涂层布生产设备、方法
CN112452613B (zh) * 2020-11-23 2022-07-12 北京燕山电子设备厂 玄武岩纤维混纺涂层布生产设备、方法

Also Published As

Publication number Publication date
BE709695A (fr) 1968-05-30
GB1123636A (en) 1968-08-14
FR1511838A (fr) 1968-02-02
SE306897B (fr) 1968-12-09
NL6701880A (fr) 1967-10-02

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