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EP2179089B1 - Procédé pour traiter un substrat - Google Patents

Procédé pour traiter un substrat Download PDF

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Publication number
EP2179089B1
EP2179089B1 EP08795254.5A EP08795254A EP2179089B1 EP 2179089 B1 EP2179089 B1 EP 2179089B1 EP 08795254 A EP08795254 A EP 08795254A EP 2179089 B1 EP2179089 B1 EP 2179089B1
Authority
EP
European Patent Office
Prior art keywords
coating
nip
milliseconds
drum
substrate
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.)
Not-in-force
Application number
EP08795254.5A
Other languages
German (de)
English (en)
Other versions
EP2179089A1 (fr
Inventor
Gary P. Fugitt
Scott E. Ginther
John W. Stolarz
Robert W. Carlson
Jr. Stanley H. Mcgrew
Steven P. Metzler
Terrell J. Green
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
WestRock MWV LLC
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Priority claimed from US11/893,736 external-priority patent/US20070295466A1/en
Priority claimed from PCT/US2007/019917 external-priority patent/WO2008103154A1/fr
Application filed by WestRock MWV LLC filed Critical WestRock MWV LLC
Publication of EP2179089A1 publication Critical patent/EP2179089A1/fr
Application granted granted Critical
Publication of EP2179089B1 publication Critical patent/EP2179089B1/fr
Not-in-force legal-status Critical Current
Anticipated expiration legal-status Critical

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Classifications

    • 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
    • B05D5/00—Processes for applying liquids or other fluent materials to surfaces to obtain special surface effects, finishes or structures
    • B05D5/02—Processes for applying liquids or other fluent materials to surfaces to obtain special surface effects, finishes or structures to obtain a matt or rough surface
    • 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
    • D21H19/10—Coatings without pigments
    • D21H19/12—Coatings without pigments applied as a solution using water as the only solvent, e.g. in the presence of acid or alkaline compounds
    • 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
    • B05D3/02—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 by baking
    • B05D3/0254—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
    • 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
    • B05D3/12—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 by mechanical means
    • 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
    • D21H19/66—Coatings characterised by a special visual effect, e.g. patterned, textured
    • D21H19/70—Coatings characterised by a special visual effect, e.g. patterned, textured with internal voids, e.g. bubble coatings
    • 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
    • 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
    • D21H23/00—Processes or apparatus for adding material to the pulp or to the paper
    • D21H23/02—Processes or apparatus for adding material to the pulp or to the paper characterised by the manner in which substances are added
    • D21H23/22—Addition to the formed paper
    • D21H23/52—Addition to the formed paper by contacting paper with a device carrying the material
    • D21H23/56—Rolls

Definitions

  • This patent application relates to a method and apparatus for forming a coated substrate, eg in papermaking.
  • the present disclosure relates to a method for treating a substrate with a polymer film-forming composition. More particularly, the disclosure relates to a paper or paperboard manufacturing method comprising the steps of applying a polymer film-forming coating to a substrate, and, bringing the polymer coating into contact with a heated surface while the polymer coating is still in a wet state. The resulting polymer layer has a smooth surface with voids (e.g., bubbles) just below the surface.
  • the polymer coating may comprise a crosslinkable hydrogel, and a crosslinking solution may be applied to the polymer coating on the substrate surface thereby forming at least a partially crosslinked polymer coating then placed into contact with a heated surface.
  • the present disclosure also relates to a treated substrate product.
  • the present disclosure also relates to a method for treating a substrate with a polymer film-forming composition, and bringing the substrate into contact with a heated surface in a pressure nip.
  • Paper is manufactured by an essentially continuous production process wherein a dilute aqueous slurry of cellulosic fiber flows into the wet end of a paper machine and a consolidated dried web of indefinite length emerges continuously from the paper machine dry end.
  • the wet end of the paper machine comprises one or more headboxes, a drainage section and a press section.
  • the dry end of a modern paper machine comprises a multiplicity of steam heated, rotating shell cylinders distributed along a serpentine web traveling route under a heat confining hood structure.
  • the screen is constructed and driven as an endless belt carried over a plurality of support rolls or foils.
  • a pressure differential across the screen from the side in contact with the slurry to the opposite side draws water from the slurry through the screen while that section of the screen travels along a table portion of the screen route circuit.
  • the fibrous constituency of the slurry accumulates on the screen surface as a wet but substantially consolidated mat.
  • the mat Upon arrival at the end of the screen circuit table length, the mat has accumulated sufficient mass and tensile strength to carry a short physical gap between the screen and the first press roll.
  • This first press roll carries the mat into a first press nip wherein the major volume of water remaining in the mat is removed by roll nip squeezing.
  • One or more additional press nips may follow.
  • the mat continuum now generally characterized as a web, enters the dryer section of the paper machine to have the remaining water removed thermodynamically.
  • the ultimate properties of a particular paper are determined in large part by the species of raw material used and the manner in which the paper machine and web forming process treat these raw materials. Important operative factors in the mechanism of forming the paper web are the headbox and screen.
  • Coated paper or paperboard used for printing and for packaging is generally required to have high level of gloss, excellent smoothness, and excellent printability, as well as certain strength and stiffness characteristics.
  • coated paper or paperboard has a high stiffness, it can pass smoothly through highspeed printing or packaging machines with less feeding jams.
  • Higher stiffness paper can be advantageously used in books, magazines, and catalogues, because it provides a feel of hardness or heaviness similar to a hardcover book.
  • high stiffness is necessary for maintaining the structural integrity of the paperboard product during filling and in subsequent use.
  • Stiffness has close relationship to the basis weight and density of paper. There is a general trend that stiffness increases as the basis weight increases (for a given caliper), and decreases as the paper density increases (for a given basis weight). Stiffness and other properties can be improved by increasing basis weight. However, this would result in a product utilizing more fibers, which add cost and weight. Therefore, coated paper or paperboard with high stiffness but moderate basis weight is desirable. Paper with moderate basis weight is also more economical because less raw material (fiber) is utilized. In addition, shipping costs based on weight are less for low basis weight paper.
  • coated paper or paperboard which must be printed is often required to have high gloss and smoothness.
  • density typically must be increased to some extent to allow for a usable printing surface.
  • Smoothness is normally achieved by calendering.
  • calendering will cause a reduction in caliper, which typically results in a corresponding reduction in stiffness.
  • the calendering process deteriorates the stiffness of paper by significantly reducing caliper and increasing the density.
  • the base sheet for conventional coated board grades typically is heavily densified by calendering to provide a surface roughness low enough to produce final coated smoothness acceptable to the industry.
  • These calendering processes, including wet stack treatment may increase density by as much as 20% to 25%.
  • Improvements in the calendering process including moisture gradient calendering, hot calendering, soft calendering, and belt calendering slightly improved stiffness for a given caliper but did not change the fundamental ratio between caliper, stiffness, smoothness, and printing properties.
  • JP 10168792 discloses a method of forming high gloss and high smoothness paper in which an aqueous coating composition is applied to an undercoating layer on the paper and the coating composition is dried by contact under pressure with a heating drum having a mirror surface.
  • the aqueous coating composition comprises a synthetic resin.
  • US 4,084,380 discloses a papermaking apparatus comprising an applicator for applying a film of aqueous coating to a web of paper, and a heated drum and a press roll forming a nip with the drum for pressing the paper.
  • the coated paper is dried and re-wetted before being fed into the nip of the drum and press roll.
  • This document discloses a drum diameter of 1.22 metres at a temperature of 120°C to 130°C which is stated to be adequate for web speeds of 1 to 1.25 ms -1 . It is disclosed that a temperature range of 100°C to 150°C can be employed but that poor release can occur at drum temperatures near 150°C.
  • a release agent can be added to the water used for re-wetting in order to address this problem.
  • the invention provides a process for treating a substrate, comprising the steps of:
  • the nipped contact has a nip local pressure, and comprises a first duration during which the nip local pressure increases and the film undergoes heating with substantially no vapor formation, and a second duration during which the nip local pressure decreases and the polymer solution boils and forms voids that remain in the film.
  • the invention also provides an apparatus for treating a substrate, comprising: an applicator for applying to the substrate an aqueous coating as a film,
  • the coating includes a water soluble polymer and essentially no elastomeric material. There are voids formed within the coating.
  • the surface of the coating has a Sheffield Smoothness of less than 300 units. There are voids formed under the surface of the coating.
  • the coating includes a water soluble polymer, a release agent, and essentially no elastomeric material.
  • the coating includes a surface, and the surface has a Sheffield Smoothness of less than 300 units. There are voids formed under the surface of the coating.
  • a wet film of aqueous polymer solution is applied to the substrate.
  • the aqueous polymer solution is immobilized by bringing it into contact with a heated surface to cause the aqueous polymer solution to boil, and to at least partially dry the aqueous polymer solution.
  • a wet film of aqueous polymer solution is applied to the substrate.
  • the aqueous polymer solution is immobilized by bringing it into contact with a heated surface to cause the aqueous polymer solution to boil and form voids that remain in the aqueous polymer solution, and to at least partially dry the aqueous polymer solution.
  • a coating of aqueous polymer solution is applied to the substrate as a wet film.
  • the coating includes a water soluble polymer and a release agent.
  • the film is immobilized by bringing it into contact for less than 3 seconds with a heated surface with a temperature above 150°C so as to cause the aqueous polymer solution to boil and form voids in the film, and to at least partially dry the film.
  • a coating of aqueous polymer solution is applied to the substrate as a wet film.
  • the coating includes a water soluble polymer and essentially no elastomeric material.
  • the film is immobilized by bringing it into contact for less than 3 seconds with a heated surface with a temperature above 150°C so as to cause the aqueous polymer solution to boil and form voids in the film, and to at least partially dry the film.
  • a coating of aqueous polymer solution is applied to the substrate as a wet film.
  • the coating includes a water soluble polymer and essentially no elastomeric material.
  • the film is immobilized by bringing it into contact for less than 3 seconds with a heated surface with a temperature above 150°C so as to cause the aqueous polymer solution to boil and form voids in the film, and to at least partially dry the film.
  • the coating surface after drying has a Sheffield Smoothness of less than 300 units.
  • a coating of aqueous polymer solution is applied to the substrate as a wet film.
  • the coating includes a water soluble polymer, a release agent, and essentially no elastomeric material.
  • the film is immobilized by bringing it into contact for less than 3 seconds with a heated surface with a temperature above 150°C so as to cause the aqueous polymer solution to boil and form voids in the film, and to at least partially dry the film.
  • the coating surface after drying has a Sheffield Smoothness of less than 300 units.
  • a wet film of aqueous polymer solution is applied to the substrate.
  • the aqueous polymer solution includes at least about 60% water soluble polymer by dry weight, and up to 10% release agent by dry weight.
  • the aqueous polymer solution is immobilized by bringing it into contact for less than 3 seconds with a heated surface with a temperature above 150°C so as to cause the aqueous polymer solution to boil and form voids in the aqueous polymer solution, and to at least partially dry the aqueous polymer solution.
  • a coating film is applied to a substrate, the film is brought into contact with a heated surface in a nip, the nip local pressure initially increasing and the film being heated with no vapor formation, the nip local pressure then decreasing and the coating film boiling and forming voids in the film, the film being at least partly dried.
  • a coating film is applied to a substrate, the coating including a water soluble polymer and a release agent, the film is brought into contact with a heated surface in a nip, the nip local pressure initially increasing and the film being heated with no vapor formation, the nip local pressure then decreasing and the coating film boiling and forming voids in the film, the film being at least partly dried.
  • a coating film is applied to a substrate, the film is brought into nipped contact for less than 3 seconds with a heated surface having a temperature above 150°C, the nip local pressure initially increasing and the film being heated with no vapor formation, the nip local pressure then decreasing and the coating film boiling and forming voids in the film, the film being at least partly dried.
  • an apparatus for treating a web substrate, comprising a coating applicator, a drum having a diameter between 61cm (24 inches) and 213cm (84 inches), a press roll forming a nip with the drum having a nip dwell time of 1 - 60 milliseconds, the web substrate travels through the nip at between 1.53m/s (300 fpm) and 15.3m/s (3000 fpm), and an energy source for maintaining the drum temperature above the boiling point of the coating.
  • an apparatus for treating a web substrate, comprising a coating applicator, a drum having a diameter between 61cm (24 inches) and 213cm (84 inches), a belted shoe device forming a nip with the drum having a nip dwell time between about 1 - 225 milliseconds, the web substrate travels through the nip at between 1.53m/s (300 fpm) and 15.3m/s (3000 fpm), and an energy source for maintaining the drum temperature above the boiling point of the coating.
  • a process includes applying a coating film to a substrate, heating the film under a pressure with no vapor formation, and reducing the pressure so that the film boils and forms voids that remain in the film.
  • a process in another embodiment, includes applying a coating film to a substrate, wherein the coating includes a water soluble polymer and a release agent, heating the film under a pressure with no vapor formation, and reducing the pressure so that the film boils and forms voids that remain in the film.
  • a process includes applying a coating film to a substrate, bringing the film into contact for less than 3 seconds with a heated surface having a temperature above 150°C, wherein the contact comprises a nipped contact with the heated surface, heating the film under a pressure with no vapor formation, and reducing the pressure so that the film boils and forms voids that remain in the film.
  • FIG. 1 is a schematic view of an apparatus for treating a substrate with a polymer coating in accordance with one embodiment of the present invention.
  • FIGs. 2 - 9 are cross section micrographs showing the morphology of samples made in accordance with one embodiment of the invention, and having a top coating.
  • FIGs. 10-12 are cross section micrographs showing the morphology of samples made in accordance with one embodiment of the invention, and having no top coating.
  • FIGs. 13-14 are surface micrographs made by scanning electron microscope showing the morphology of samples made in accordance with one embodiment of the invention, and having no top coating.
  • FIGs. 15-16 are surface micrographs made by backscatter scanning electron microscope showing the morphology of samples made in accordance with one embodiment of the invention, and having no top coating.
  • FIG. 17 is a graph showing distribution of void dimensions in samples made in accordance with one embodiment of the invention.
  • FIG. 18 is a detail view of an apparatus for treating a substrate with a polymer coating in accordance with certain embodiments of the present invention.
  • FIG. 19 is a graph showing a relationship between heat transfer rate and temperature difference.
  • the present disclosure relates to a method for treating a substrate with a polymer film-forming coating. More particularly, the disclosure relates to a paper or paperboard manufacturing method comprising the steps of applying a polymer coating to a substrate, and bringing the polymer coating into contact with a heated surface while the polymer coating is still in a wet state. Boiling of water in the polymer coating causes voids to form under the surface, but the surface of the film is smooth due to intimate contact with the heated surface.
  • the paper or paperboard produced in accordance with certain embodiments of the present invention exhibits desirable levels of surface flatness and smoothness without significant densification of the base paper.
  • the polymer coating may include a crosslinkable material and a crosslinking solution may be applied to the polymer coating on the substrate surface thereby forming at least a partially crosslinked polymer film-forming composition.
  • the polymer coating may typically be applied to the web first and then the cross linking solution applied before the treated web contacts the heated surface.
  • weakly cross linking polymers it may be possible to provide the cross linking solution in the coating itself.
  • One advantage of treating a substrate with a polymer film-forming coating in accordance with the present invention relates to the improvement in smoothness and/or flatness that can be obtained without significantly increasing the density or decreasing the caliper of the sheet.
  • the heavy calendering of the cellulose paper web associated with conventional techniques is not required to produce a paper having print properties comparable to conventional coated papers.
  • much lower pressures can be applied to provide similar printing properties on papers with increased stiffness.
  • the cellulose paper web is smoothed such that the caliper decreases not more than about 7% and typically is decreased by between about 2% and 5%. Depending on the properties of the substrate, the caliper decrease may be less.
  • the cellulose paper web may be calendered to a Parker Print Surf smoothness of between about 2 and 6 ⁇ m prior to application of the polymer film.
  • substrates with higher Parker Print Surf values may be used.
  • a substrate with a Parker Print Surf smoothness of about 9 microns may be used.
  • Parker Print Surf smoothness is determined in accordance with TAPPI standard T 555 om-99.
  • FIG. 1 illustrates an apparatus 10 useful in practicing certain embodiments of the invention.
  • a substrate 12 is subjected to treatment on one surface thereof with crosslinkable polymer coating 14 to form a layer of polymer coating 16 on substrate 12. While the polymer coating is still wet, an optional crosslinking solution 18 may be applied to the layer of polymer coating 16 thereby forming a cross linked polymer coating 20 on substrate 12.
  • the polymer coating 20 is typically at least partially crosslinked.
  • the polymer coating is still in a wet state before being brought into contact with hot polished drum 22 by pressing the web 12 against the drum surface with a press roll 24. Heat from the drum surface causes boiling within the wet polymer coating, so that voids form in the polymer under the surface.
  • the crosslinking solution causes the polymer coating to crosslink and gel into a substantially continuous layer or film. Typically, the resulting film will exhibit improved strength over the base sheet.
  • the polymer treated sheet may not be fully dried so it may be conveyed through a secondary heater 26. Any type of secondary heating device can be used that is capable of drying the treated sheet without adversely affecting the properties of the sheet.
  • the treated sheet emerges from secondary heaters 26 as a polymer film treated substrate 28 characterized by improved flatness and smoothness.
  • additional coating processes 30 and other processes such as coating, gloss calendering, etc) may be used to form a coated product 32.
  • the web wraps a substantial portion of hot polished drum 22.
  • the amount of wrap may depend on operating conditions such as web speed, moisture content of the polymer film forming composition 20, temperature of the drum, and other process factors. It is possible that a small amount of contact time with hot polished drum 22 may be sufficient. Besides providing the substrate in web form, it may also be provided in sheet form.
  • the crosslinkable polymer coating and the optional crosslinking solution may be applied by any number of techniques, such as dip-coating, rod coating, doctor blade coating, gravure roll coating, reverse roll coating, metered size press, smooth roll coating, extrusion coating, curtain coating, spray coating and the like.
  • the crosslinkable polymer coating and crosslinking solutions may be applied by the same coating technique or different methods may be used for each.
  • One embodiment in accordance with the present invention is based on the coagulation or gelling that occurs between polyvinyl alcohol and borax.
  • polyvinyl alcohol PVOH
  • a borax solution is an example of a corresponding crosslinker.
  • the crosslinker solution 16 is applied at a rate and solution solids to give a borax coverage of at least about 0.1 g/m 2 dry.
  • This wet, crosslinked polymer film 20 is then brought into contact with a hot polished drum 22 by pressing the web 12 against the drum surface with a press roll 24.
  • the drum surface temperature is at least 150°C, or in accordance with certain embodiments, at least 190°C so that the coating can be dried and release from the drum surface.
  • the contact time of the polymer film to the drum may be in the range of up to 3.0 seconds, more particularly between about 0.5 - 2.0 seconds. This is sufficient time for the polymer film to immobilize and solidify, giving the surface of the polymer film a flat smooth finish mirroring the surface of the drum.
  • Immobilizing the polymer film includes at least partially drying the film.
  • the coating is not necessarily completely dry when it leaves the drum, so additional drying 26 may be needed.
  • the web then continues on through the process and may receive additional coating layers, for example conventional coatings, prior to being wound up.
  • the polymer coating may be applied as a single layer or as two or more layers. Limited experiments also suggest that a polymer film may be immobilized or solidified with just momentary contact with the heated drum, as may be achieved by using a press roll 24 to press the web 12 against the hot drum 22, without any additional wrap of web around the hot drum. However, it is contemplated that some wrap of the hot drum may be practiced, and that optionally a felt 23 may be used to help press the web into contact with the hot drum. If a felt 23 is used to help press the web into contact with the hot drum, then the felt 23 may be carried between the press roll 24 and the heated drum 22.
  • crosslinkable polymers useful in certain embodiments of the present invention include crosslinkable hydrogels.
  • the following crosslinkable hydrogels are particularly useful: starch, waxy maize, protein, polyvinyl alcohol, casein, gelatin, soybean protein, and alginates.
  • One or more polymers selected from the above-recited ones can be used.
  • the crosslinkable polymer typically is applied in solution form and usually as an aqueous solution.
  • concentration of the polymer in solution is not particularly limited but can be easily determined by one of ordinary skill in the art. For example, a solution of about 20% starch may be used as described below.
  • the crosslinkable polymer may be applied to provide a surface coverage (dry basis) of from about 3 to about 15 gsm (g/m 2 ) more particularly from about 4 to about 8 gsm.
  • the crosslinkable polymer may be used in an amount ranging from about 60% to about 100% by weight of the dry materials.
  • crosslinkers include borates, aldehydes, ammonium salts, calcium compounds and derivatives thereof.
  • the crosslinker if used typically may be applied in solution form and usually as an aqueous solution.
  • concentration of the crosslinker in solution is not particularly limited but can be easily determined by one of ordinary skill in the art.
  • the crosslinker may be applied to provide a surface coverage (dry basis) of from about 0.1 to about 0.5 gsm more particularly from about 0.2 to about 0.3 gsm.
  • the temperature of the heated surface is in excess of that typically used for cast coating.
  • the higher temperature should allow for higher run speeds. It is anticipated that paper or paperboard produced in accordance with certain embodiments of the present invention may be produced at speeds in the range of 3.8 to 15.3 m/s (750 to 3000 fpm), more particularly from about 7.65 to 9.2 m/s (1500 to 1800 fpm).
  • the higher temperature and the dwell time are selected such that the coating composition is heated and it appears that when the coating boils it remains for a time in contact with the drum. The contact results in a polymer film surface that exhibits improved smoothness and gloss.
  • the treated surface is ink receptive. Boiling of the coating as it is being smoothed on the polished drum surface appears to significantly improve gloss and smoothness of the finished polymer film treated substrate.
  • the polymer coating on the substrate is typically pressed against the heated surface for a sufficient period of time to allow the coating to boil and then set to a smooth, glossy finish.
  • the contact time of the forming polymer film to the drum is within the range of up to 3.0 seconds, more particularly up to about 2.0 seconds, and most particularly up to about 0.5 seconds.
  • the polymer coating may also include one or more pigments.
  • useful pigments include, but are not limited to, kaolin, talc, calcium carbonate, calcium acetate, titanium dioxide, clay, zinc oxide, alumina, aluminum hydroxide and synthetic silica such as noncrystalline silica, amorphous silica or finely divided silica are examples thereof.
  • Organic pigments may also be used.
  • the crosslinkable polymer coating and/or the crosslinking solution may further include one or more release agents.
  • release agents include, without limitation, waxes, such as petroleum, vegetable, animal and synthetic waxes, fatty acid metal soaps, such as metal stearates, long chain alkyl derivatives, such as fatty esters, fatty amides, fatty amines, fatty acids, and fatty alcohols, polymers, such as polyolefins, silicone polymers, fluoropolymers, and natural polymers, fluorinated compounds, such as fluorinated fatty acids and combinations thereof.
  • waxes such as petroleum, vegetable, animal and synthetic waxes
  • fatty acid metal soaps such as metal stearates
  • long chain alkyl derivatives such as fatty esters, fatty amides, fatty amines, fatty acids, and fatty alcohols
  • polymers such as polyolefins, silicone polymers, fluoropolymers, and natural polymers, fluorinated compounds
  • the coating may contain from about 0.3 to 10 percent release agent, more particularly from about 2 to 5 percent by weight.
  • release agent may be sprayed onto the coating surface, or applied to the heated drum surface. If a non-sticking surface can be provided on the heated drum, whether by a release agent or other means, then application of a release agent in the coating or onto the coating surface may not be needed.
  • the polymer coating employed in certain embodiments of the present invention, wherein at least the aforementioned polymer is contained, is generally prepared in the form of an aqueous composition.
  • An appropriate ratio between those ingredients is different depending on the polymer composition, the application conditions and so on, but it has no particular limitation as far as the treated paper produced can satisfy the quality required for the intended use thereof.
  • the polymer coating according to certain embodiments of the present invention can optionally contain additives, such as a dispersant, a water retaining agent, a thickening agent, an anti-foaming agent, a preservative, a colorant, a waterproofing agent, a wetting agent, a drying agent, an initiator, a plasticizer, a fluorescent dye, an ultraviolet absorbent, a release agent, a lubricant and a cationic polyelectrolyte.
  • additives such as a dispersant, a water retaining agent, a thickening agent, an anti-foaming agent, a preservative, a colorant, a waterproofing agent, a wetting agent, a drying agent, an initiator, a plasticizer, a fluorescent dye, an ultraviolet absorbent, a release agent, a lubricant and a cationic polyelectrolyte.
  • the substrate is treated with the polymer coating near a central region of the paper machine, such as the size press position.
  • the apparatus for applying the polymer coating to the substrate may be positioned relative to the paper machine so as to apply the polymer film to either surface of the forming paper web. More than one apparatus may be employed to apply a polymer film to each side of the forming paper web.
  • the base sheet is typically formed from fibers conventionally used for such purpose and, in accordance with the particular embodiments, includes unbleached or bleached kraft pulp.
  • the pulp may consist of hardwood or softwoods or a combination thereof.
  • the basis weight of the cellulose fiber layer may range from about 30 to about 500 gsm, and more particularly, from about 150 to about 350 gsm.
  • the base sheet may also contain organic and inorganic fillers, sizing agents, retention agents, and other auxiliary agents as is known in the art.
  • the final paper product can contain one or more cellulose-fiber layers, polymer film layers and, in accordance with certain embodiments, other functional layers.
  • the present invention in accordance with certain embodiments, provides one or two-sided coated paper or paperboard for printing or packaging whose Parker Print Surf smoothness value after the coating and finishing processes, when measured according to TAPPI paper and pulp test method No. 5A, is lower than about 2-3 ⁇ m.
  • the paper or paperboard described herein may further be provided with one or more additional coatings.
  • a top coating containing conventional components may be provided to improve certain properties of the paper or paperboard. Examples of such conventional components include pigments, binders, fillers and other special additives.
  • the top coating when present, may be applied at much lower coat weights than conventional coatings and yet provide similar print properties. Accordingly, the top coating weight may be about 4 to 9 gsm as a single coating layer or about 8 to 18 gsm as two coating layers.
  • conventional coated papers typically require about 10 to 20 gsm as a single coating layer or 18 to 30 gsm as two coating layers to provide comparable surface properties.
  • the paper or paperboard may also be coated on the side of the sheet having the non-treated surface.
  • a base sheet having a caliper of about 10 points, a Parker Print Surf (PPS) value of about 9 ⁇ m (10kg pressure with a soft backing) and a Sheffield smoothness of about 310 can be treated in accordance with certain embodiments of the present invention to provide a treated sheet having improved smoothness with only a minimal decrease in caliper.
  • the base sheet may be treated by applying a PVOH solution at approximately 25% solids to the base sheet to provide a coverage of about 5 g/m 2 dry.
  • the crosslinker solution may be applied at a rate and solution solids to give a borax coverage of at least about 0.1 g/m 2 dry.
  • the wet, crosslinked polymer film can be brought into contact with a hot polished drum by pressing the sheet against the drum surface.
  • the drum surface temperature may be at least about 190°C.
  • the coating would be dried and released from the drum surface.
  • the contact time of the polymer film to the drum would typically be in the range of between about 0.5 - 2.0 seconds.
  • the treated sheet would have a caliper of between about 9.6 and 10.0 points, a PPS value of about 2.4 to 3.0 and a Sheffield smoothness of about 140 - 170.
  • a starch solution may be used as the polymeric material in the polymer coating.
  • the method includes applying a polymer coating comprising a crosslinkable hydrogel to a substrate, applying a crosslinking solution to the polymer coating on the substrate surface thereby forming at least a partially crosslinked polymer film-forming coating and bringing the polymer film-forming coating into contact with a heated surface while the polymer film-forming coating is still in a wet state.
  • the heated surface may be a hot polished drum having a flat smooth finish.
  • the temperature of the heated surface typically is within a range of from 150°C to about 240°C. Higher temperatures may be used, for example up to about 300°C.
  • the temperature of the heated surface in accordance with certain embodiments is within a range of from 180°C to about 200°C, and in accordance with certain embodiments is at least about 190°C.
  • the crosslinkable polymer may be selected from the group consisting of starch, waxy maize, protein, polyvinyl alcohol, casein, gelatin, soybean protein, and alginates. In accordance with certain aspects of the present invention, the crosslinkable polymer may be used in amounts ranging from about 60 to about 100% by weight of the dry materials.
  • the crosslinker may be a borate or borate derivative such as borax, sodium tetraborate, boric acid, phenyl boronic acid, or butyl boronic acid.
  • the crosslinker may be used in amounts ranging from about 1 to about 12% based on the crosslinkable polymer.
  • the treated papers obtained by the above process are characterized by improved smoothness in conjunction with relatively minor increases in density compared to the original sheet.
  • the coating may be moistened for example by applying water.
  • One method is to spray water onto the coating before it contacts the hot drum.
  • it may also be possible to operate without any additional moistening.
  • starch may be used as the soluble polymer.
  • starch-based coatings can be run successfully without a crosslinker, and good results may be obtained without gelling (also called coagulating).
  • a starch solution containing 2-5% of a release agent was brought into contact with a heated drum under conditions described above. In certain conditions, if moistening of the coating is desired, water alone may be used as the spray and yield a good reproduction of the polished surface. If the coating solids are low enough, the process works without a moistening water spray. A 20% solids starch coating was applied to the web and brought into contact with a heated drum, and gave good reproduction.
  • a run consists of the drum being heated to approximately 190°C, the spray level being set, coating being applied to the web by a metered rod method, optionally followed by moistening spray (which optionally may contain a cross linking agent), and then by the web being brought into contact with the drum at 0.18 m/s (35 fpm).
  • the drum temperature during a run varied between 180°C and 190°C. During a run, the only variable that was changed was the coating weight applied by the metering rod.
  • Coat weight was measured by differential weight and is reported as bone-dry.
  • the first coating was 95% by dry weight CELVOL 203S polyvinyl alcohol (PVOH) and 5% Emtal 50 VCS, a triglyceride used as a release agent (CELVOL is made by Celanese).
  • the coating solids were 20% by weight.
  • the coating was applied by a metering rod. Table 1 is a list of samples and test conditions.
  • Sample 1.1 was made by spraying the coating with a crosslinking solution containing 3% by weight borax and 1% by weight of a sulfonated castor oil as a release agent.
  • the spraying rate was 48 milliliters per minute.
  • the sample replicated the drum well and released from the drum without sticking. Significant improvements in smoothness were obtained with minimal loss of caliper.
  • the conditions were the same except that no borax was used in the spray solution. Without the borax to crosslink the polyvinyl alcohol, the coating did not release from the surface, and part of the film remained on the drum surface. This experiment clearly showed the benefit of crosslinking the polyvinyl alcohol.
  • CMC carboxymethyl cellulose
  • the carboxymethyl cellulose was FINNFIX 30 (made by Noviant, a division of Huber), which could only be run at 7% solids due to coating viscosity.
  • the coating was formulated with 95% polymer and 5% Emtal.
  • Samples 1.3 and 1.4 are two different coat weights sprayed with 48 ml/min of borax spray. The coating replicated the drum surface well and released completely from the drum. Smoothness was improved with minimal loss of caliper, but smoothness was not as good as for polyvinyl alcohol.
  • no borax was used in the spray.
  • the coating replicated the drum surface well and released completely from the drum. Smoothness was improved by removing the borax. This showed that a non-crosslinked coating could replicate and release from the drum, which indicates that materials other than crosslinkable materials can be used in this process.
  • a minimally pressed base sheet having a basis weight of 181 g/m 2 (111 lb/3000 ft 2 ) was used as a substrate on which to apply and treat simple coating compositions.
  • the first coating was 95% by dry weight CLEER-COTE 625 starch (a viscosity modified waxy corn starch, made by A.E. Staley, a division of Tate & Lyle) and 5% Emtal 50 VCS, a triglyceride used as a release agent.
  • the coating solids were 20% by weight. The coating was applied by a metering rod.
  • Sample 2.1 was made by spraying the coating with a crosslinking solution containing 3% by weight borax and 1% by weight of a sulfonated castor oil as a release agent. The spraying rate was 46 milliliters per minute. The sample replicated the drum well and released from the drum without sticking. Significant improvements in smoothness were obtained with minimal loss of caliper. Samples 2.2, 2.3, 2.4 and 2.5 were made with different coat weights of the same coating, but the spray did not contain borax. All samples replicated the surface well and released completely from the drum. Samples 2.6 and 2.7 were run without any spray at all. The samples replicated the surface well and completely released. Smoothness values were not quite as good, but samples still had significantly improved smoothness with minimal reduction in caliper. This demonstrates that the process can work without any moistening spray.
  • a conventional pigmented clay coating about two-thirds clay and one third carbonate, with a latex binder, applied in a single coat of approximately 16 g/m 2 (10 lb/ 3000ft 2 ) applied over the smooth polymer layer.
  • FIG. 2 Micrographs revealed that voids exist in the polymer coating layer, as shown in FIGs. 2 through 9 , which include measurement bars to indicate their scale. For FIGs. 2-5 , the microscope magnification was 1000, and the measurement bars are 20 ⁇ m long.
  • the structure as shown includes a paperboard substrate 110.
  • the substrate thickness generally extends below the area of the micrograph. Because of the freeze fracturing process, the substrate 110 as shown in the micrographs is sometimes separated or partly separated from polymer layer 120. Therefore the upper boundary of substrate 110 may be only approximately shown by the bracketed distance denoting the substrate.
  • the polymer coating layer 120 had been applied onto substrate 110, and dried against a heated drum, as described previously. Then a top coating 130 was applied and dried.
  • the term "polymer coating” is used here to describe that layer applied as described above, then contacted while wet against a heated drum.
  • the term “top coating” is used to describe the outer layer, which was applied as one layer. Obviously the “top coating” could be applied in more than layer and could be of coating materials other than those used here.
  • Voids 121 are evident in the polymer coating layer 120, as seen in FIGs. 2-9 .
  • FIG. 2 for example shows several voids 121 in polymer coating layer 120, with the voids appearing to be approximately 5 to 20 ⁇ m in lateral dimension. It is assumed that their size going "into" the fractured sample is in approximately the same range.
  • the voids typically appear to be somewhat “flattened” in the "vertical” direction, that is, going into the sample thickness.
  • the voids also appear to have "walls" that are relatively smooth, and generally thin. These thin walls are most apparent as seen between adjacent voids. Where a void wall is adjacent to the top coating 130, its thickness may be difficult to see but its presence may be deduced by the smooth lower contour of the top coating 130 adjacent to the void.
  • FIG. 3 is an example micrograph showing several voids 121 in the polymer coating layer. The voids appear to extend over an area equivalent to more than half the coated surface area. The polymer coating layer is not well defined in this micrograph.
  • FIG. 4 is an example micrograph showing several voids 121 in polymer coating layer 120.
  • the walls of the voids appear to be relatively thin, as evidenced by a somewhat translucent appearance in the walls of two of the voids.
  • FIG. 5 shows several voids 121 in polymer layer 120, with individual measurement bars showing dimensions of the selected voids, for example, moving generally from left to right, measurements of 10.5 ⁇ m in vertical distance, 36 ⁇ m in lateral distance, 10.6 ⁇ m in vertical distance, and 36.3 ⁇ m in lateral distance. Again the voids appear to extend over an area equivalent approximately half the coated surface area.
  • FIG. 6 shows another sample with similar measurement bars, for example, moving generally from left to right, measurements of 8.66 ⁇ m in vertical distance, 32.1 ⁇ m in lateral distance, 11.8 ⁇ m in vertical distance, and 22.7 ⁇ m in lateral distance. Measurements such as these in FIGs. 5 and 6 were collected for use in the graph discussed later in FIG. 17 .
  • FIG. 7 shows voids 121 in polymer layer 120, including several showing a generally flattened aspect. The voids appear to extend over an area equivalent to nearly all the coated surface area.
  • FIG. 8 shows another sample with similar widespread voids 121. The wall areas of several voids are visible.
  • FIG. 9 shows yet another sample where the voids 121 appear to extend over an area equivalent to nearly all the coated surface area.
  • FIG. 10 shows the polymer layer 120, which contains voids 121 and has a very smooth outer surface.
  • the polymer layer is on paperboard substrate 110, and one of the cellulose fibers 112 is denoted.
  • the substrate thickness generally extends below the area of the micrograph.
  • FIGs. 11 and 12 show additional micrographs of samples that were polymer coated but not top-coated. Again the smoothness of the polymer layer 120 is evident, as are the underlying voids 121. The walls of the voids often coincide with the surface of the polymer coating.
  • FIG. 13 (at 200x magnification) and FIG. 14 (at 500x magnification) show the surface of samples as seen under a scanning electron microscope. These samples were not given top coating 130.
  • the larger string-like structures 112 are cellulose fibers of the substrate 110.
  • the smaller cell-like structures 122 that appear as a fine network or mesh are individual voids in polymer layer 120.
  • the polymer layer here appears essentially transparent, except for the walls of the voids.
  • FIGs. 15 and 16 show the surface of samples as seen under a backscatter scanning electron microscope. These samples were not given top coating 130.
  • the larger string-like structures 112 are cellulose fibers of the substrate 110.
  • the smaller cell-like structures 122 that appear as a fine network or mesh are the walls of individual voids in polymer layer 120.
  • the polymer layer here appears essentially transparent, except for the walls of the voids. The voids appear to be distributed over the entire surface.
  • FIG. 17 is a graph showing the distribution of void sizes based on approximately 90 measurements each of void width (lateral dimension) and height (vertical dimension in the micrographs).
  • the measurements show an average void width (measured in the direction parallel to the thickness of the sample) of about 19 ⁇ m, with a standard deviation of about 9 ⁇ m.
  • the measurements show an average void height (measured in the direction going "into" the sample thickness) of about 10 ⁇ m, with a standard deviation of about 4 ⁇ m.
  • the voids typically help bridge the gap between an otherwise rough substrate layer 110, and the smooth surface of the heated drum.
  • the dried polymer coating has a smooth replicated surface, which is smoother than the substrate layer 110. It appears that many or most of the voids remain intact when top coating 130 is applied. Therefore the top coating ends up smoother because of the relatively smooth underlying polymer layer 120. This is seen as an advantage achieved by the invention. Besides the influence of the voids on help creating a smooth replicated surface, the voids also contribute to a lower density in the product.
  • the conditions in the nip between press roll 24 and hot drum 22 influences whether voids form in the polymer coating. Depending on press roll hardness, and the diameters of the press roll and hot drum, it may be necessary to adjust the nip loading (for example, the PLI loading on the nip) in order to achieve boiling in the nip which creates the voids.
  • Polymer coated substrate 220 enters the nip between press roll 224 and hot polished drum 222.
  • a nip pressure profile 250 exists between the hot polished drum and the press roll.
  • the nip pressure profile has an ingoing portion 252 and an outgoing portion 254.
  • the shape of nip pressure profile 250 is meant as an example only.
  • a nip local pressure exists at any point on the profile, and the nip local pressure may vary going through the nip, as shown by the nip pressure profile 250. For example, it may increase on the ingoing side of the nip, then decrease on the outgoing side of the nip.
  • a nip average pressure 256 also exists.
  • the liquid was superheated, that is, heated beyond its atmospheric-pressure boiling point, there is sufficient energy not only to vaporize liquid and create bubbles or voids, but also enough energy to sufficiently dry the polymer coating (such as around the bubbles, for example in the walls of the bubbles) so that upon leaving the nip, the coating with its voids and smooth surface retains its structure.
  • the vapor as its escapes from the coating layer, may thus help dry the coating.
  • the web 230 releases from the hot drum and the surface replication process is complete.
  • water in the coating is vaporized to form the voids.
  • the pressure in the nip is great enough to promote a high rate of heat transfer, and lead to a superheated condition in the coating.
  • the pressure is too great, it may lead to a reduction in caliper, which is not desired. Excess pressure might possibly force coating into the substrate to the extent that there is poor surface replication.
  • the process depicted in FIG. 18 occurs within a certain range of hot drum temperatures and nip widths (related to time in the nip).
  • the temperature difference (T s -T sat ) is sometimes termed the delta T ( ⁇ T).
  • FIG. 19 shows an exemplary graph of heat transfer q from a heated surface to a liquid undergoing phase change.
  • the heat transfer behavior as depicted in FIG. 19 is a well known phenomenon.
  • the log-log graph shows heat transfer rate q vs. temperature difference ⁇ T.
  • the notation "C” denotes a maximum or "critical" heat transfer rate. For boiling water, this maximum heat transfer rate may occur at a ⁇ T of about 50°C. It is understood that the critical heat transfer rate for a polymer coated substrate in a pressure nip may differ from this particular ⁇ T, but the general shape of the graph, and the underlying physics, may still apply.
  • Equation 1 the equation may be modified, for example based on empirical data, or an alternative equation may be used.
  • the nip dwell time appears to be an important parameter. Along with delta T, it plays an important role in determining the amount of energy transferred in the nip.
  • the hot drum temperature T s and the nip pressure may be controlled to achieve operation near point "C" on the heat transfer curve, in order to maximize energy transfer.
  • boiling may initially be inhibited (for example on the ingoing side of the nip where the pressure is increasing) so that a very high heat transfer rate occurs, allowing an excess of energy to be transferred to the coating.
  • the delta T may preferably be optimized. For example to run at a certain speed, parameters such as roll diameter and hardness, and nip load, may be chosen to obtain sufficient dwell time. Operating conditions may be chosen to achieve a desired delta T, for example, to operate close to a target value, such as 50°C.
  • Equation 1 (or a similar equation or equations) can be used, along with physical properties and dimensions of the rolls, to determine suitable operating conditions to give an appropriate time in the nip. Because of the interactions of the different variables, some trial and error may be required to optimize the process. When work with a bench scale apparatus has determined a suitable combination of hot drum temperature, nip pressure, and dwell time for making acceptable product with the desired void-containing coating, then theory may be used to determine approximate operating conditions for a larger scale apparatus.
  • a bench scale apparatus makes acceptable product using a hot drum temperature of about 220°C (425°F), for a specific nip pressure and nip dwell time.
  • a hot drum temperature of about 220°C (425°F)
  • the larger apparatus will be capable of running with a hot drum temperature of about 220°C. Knowing the desired operating speed, and the suitable nip dwell time, a target nip width may be calculated.
  • Equation 1 (or other suitable theoretical, empirical, or otherwise derived equation) may be used to directly, indirectly, iteratively or otherwise determine one or more sets of operating conditions for the production equipment that will result in the desired target nip width.
  • factors to consider are the diameters of the hot drum and the press roll, the hardness of the press roll (or the hardness and thickness of its cover), and the operating ranges available for loading the nip (e.g. the PLI range of the apparatus). These factors may apply to the existing in-place equipment, or to replacement equipment that may be used instead.
  • a list of candidate press roll covers may be created, which each by virtue of their respective thickness and hardness are suitable for providing the target nip width.
  • An appropriate one of the candidate press roll covers may then be chosen, for example based on availability, durability at a given temperature, surface properties, etc.
  • the contact time of the polymer coated substrate with the hot drum surface includes the nip dwell time and may also include additional time, preferably after leaving the nip, during which the substrate is in contact with the hot drum surface.
  • the hot drum had a diameter of 1.17 m (46") with a tungsten carbide surface polished to a 2 ⁇ m finish.
  • the press roll has a diameter of 0.97 m (38") with a 30 Shore D soft covering.
  • the web width was 0.91 m (36") and nip load about 99.8 kN/m (570 PLI). This would provide an estimated average nip pressure of about 3.45 MPa (500 psi).
  • the base substrate was a bleached board with a nominal basis weight of 332 g/m2 (204 lb/3000 ft 2 ). Coatings were applied to the web using a rod coater prior to contact with the heated drum.
  • Example A used a coating made up of 97% by weight CLEER-COTE, (made by A.E. Staley, a division of Tate & Lyle) low viscosity starch and 3% of a homogenized vegetable oil release agent (triglyceride Emtal 50 VCS). The coating solids were 17.1%.
  • Example B used a PG270 (made by Penford Products) medium viscosity starch at 97% by weight with 3% vegetable oil release agent. Although the caliper of the Example B basesheet was less than the caliper of the Example B treated board, this could be due to variability in the board.
  • the heated drum temperature was about 450°F (about 230°C) at a web speed of 800 fpm. At higher web speeds, the temperature was lower.
  • the aqueous polymer coating may be optimized for the new conditions. For example, it appears that as speed increases, coating solids may be decreased slightly to provide best results.
  • the pilot conditions were run over a range of dwell times, depending on nip width and web speed. For example, good results were obtained at about 1.0 m/s (200 fpm) with a nip dwell time of about 27 milliseconds, and at about 4.5 m/s (900 fpm) with a nip dwell time of about 6 milliseconds. Less satisfactory results were obtained at about 7.5 m/s (1500 fpm) with a nip dwell time of about 3 milliseconds. These dwell times correspond to a nip width of about 28 mm (1.1 inches).
  • the heating may be by electrical resistance heating, electrical induction heating, gas-fired heating, hot oil heating, combinations of these, or other heating methods as are known in the art.
  • dwell times may range from about 3 milliseconds (for example, with a 51 mm (two-inch) shoe running at 15.2 m/s (3000 fpm)) to about 225 milliseconds (for example, if an 0.46 m (18 inch) shoe were available running at 2.0 m/s (400 fpm)).
  • paper or “paperboard” to describe the substrate. These terms are not meant to limit the type of substrate, as it is envisioned that the methods here may be suitable for various substrates including without limitation either paper or paperboard.
  • the polymer-coated paper or paperboard created by this process may be used wherever a smooth substrate or finished product is desired.
  • the polymer-coated paper or paperboard may be used as-is (e.g., as shown in FIGS. 10-16 ), or it may be used as a substrate for additional coatings or other treatments to be applied (for example the top coating 130 shown in FIGs. 2-9 , or other coatings) thereon.
  • Additional finishing materials or processes may be applied to the polymer-coated paper or paperboard, with or without additional coatings.
  • one or more additional coatings may be applied, as is typical with base coating, top coating, and triple coating of conventional paper or paperboard substrates.
  • Calendering processes may be applied, before or after optional additional coating.
  • one or more additional coatings may be applied, followed by a gloss calendering step.

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Claims (14)

  1. Procédé pour le traitement d'un support, comprenant les étapes consistant à :
    appliquer sur le support (12/220) un premier revêtement (16) d'une solution aqueuse de polymère sous forme d'un film,
    mettre le film en contact pendant moins de 3 secondes avec une surface chauffée (22/222) ayant une température supérieure à 150 °C,
    le contact comprenant un contact pincé avec la surface chauffée,
    le contact pincé comprenant une première durée pendant laquelle la pression locale de pincement augmente et le film est soumis à un chauffage pratiquement sans formation de vapeur, et une seconde durée pendant laquelle la pression locale de pincement diminue et la solution aqueuse de polymère bout et forme des vides (121/221) qui restent dans le film.
  2. Procédé selon la revendication 1, dans lequel le premier revêtement inclut un polymère hydrosoluble.
  3. Procédé selon la revendication 1, dans lequel le premier revêtement ne contient pratiquement pas de matériau élastomère.
  4. Procédé selon la revendication 1, dans lequel la solution aqueuse de polymère comprend au moins 60 % en poids sec de polymère hydrosoluble et jusqu'à 10 % en poids sec d'agent anti-adhérence.
  5. Procédé selon la revendication 1, dans lequel le contact pincé est entre un rouleau presseur (24 ; 224) et la surface chauffée (22/222) et le contact pincé a un temps de séjour choisi parmi l'un de l'ensemble constitué par entre 1 milliseconde et 60 millisecondes, entre 4 millisecondes et 25 millisecondes et entre 6 millisecondes et 10 millisecondes.
  6. Procédé selon la revendication 1, dans lequel le contact pincé est entre un dispositif à patin actionné par courroie et la surface chauffée, et le contact pincé a un temps de séjour choisi parmi l'un de l'ensemble constitué par entre 1 milliseconde et 225 millisecondes, entre 4 millisecondes et 150 millisecondes et entre 6 millisecondes et 60 millisecondes.
  7. Procédé selon la revendication 1, dans lequel le contact pincé a une pression moyenne de pincement qui lui est associée, la pression moyenne de pincement étant choisie dans l'ensemble constitué par entre 482 kPa (70 psi) et 4 823 kPa (700 psi) et entre 1 034 kPa (150 psi) et 3 790 kPa (550 psi).
  8. Procédé selon la revendication 1, dans lequel le premier revêtement (120) inclut une surface ayant un lissé Sheffield dans une plage choisie parmi l'une de l'ensemble constitué par moins de 300 unités, moins de 200 unités et moins de 150 unités.
  9. Procédé selon la revendication 1, dans lequel le premier revêtement (120) inclut une surface et au moins 50 % de la surface du premier revêtement comportent des vides de sous-surface (121/21) ayant une dimension transversale d'au moins 5 µm.
  10. Appareil (10) pour le traitement d'un support (12/110), comprenant :
    un applicateur pour l'application sur le support d'un revêtement aqueux (16) sous forme d'un film,
    un tambour (22/222) ayant un diamètre compris entre 61 cm (24 pouces) et 213 cm (84 pouces),
    un rouleau presseur (24 ; 224) ou un dispositif à patin actionné par courroie, capable de former un pincement avec le tambour, et
    une source d'énergie disposée pour chauffer le tambour à une température de plus de 150 °C, supérieure au point d'ébullition du revêtement aqueux,
    l'applicateur, le tambour et le rouleau presseur ou le dispositif à patin actionné par courroie étant configurés pour permettre au support de passer à travers le pincement à une vitesse comprise entre 1,53 m/s (300 pieds/min) et 15,3 m/s (3 000 pieds/min),
    et le pincement produisant un temps de séjour compris entre 1 milliseconde et 225 millisecondes si un dispositif à patin actionné par courroie est utilisé et entre 1 milliseconde et 60 millisecondes si un rouleau presseur est utilisé.
  11. Appareil selon la revendication 10, comprenant un rouleau presseur (24 ; 224), dans lequel le pincement produit un temps de séjour dans une plage choisie dans l'ensemble constitué par entre 4 millisecondes et 25 millisecondes, et entre 6 millisecondes et 10 millisecondes.
  12. Appareil selon la revendication 10, comprenant un dispositif à patin actionné par courroie, dans lequel la longueur de pincement dans la direction de l'acheminement du support est comprise entre 2,5 mm (0,1 pouce) et 457 mm (18 pouces), et dans lequel le pincement produit un temps de séjour dans une plage choisie dans l'ensemble constitué par entre 4 millisecondes et 150 millisecondes, et entre 6 millisecondes et 60 millisecondes.
  13. Appareil selon la revendication 11, dans lequel le rouleau presseur (24 ; 224) a un diamètre choisi parmi l'un de l'ensemble constitué par entre 30,5 cm (12 pouces) et 183 cm (72 pouces), et entre 61 cm (24 pouces) et 122 cm (48 pouces).
  14. Appareil selon la revendication 10, dans lequel le pincement fournit une pression moyenne de pincement comprise entre 482 kPa (70 psi) et 4 823 kPa (700 psi) ou entre 1 034 kPa (150 psi) et 3 790 kPa (550 psi).
EP08795254.5A 2007-08-17 2008-08-12 Procédé pour traiter un substrat Not-in-force EP2179089B1 (fr)

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US2007018418 2007-08-17
US11/893,736 US20070295466A1 (en) 2006-02-23 2007-08-17 Method for treating a substrate
US95747807P 2007-08-23 2007-08-23
PCT/US2007/019917 WO2008103154A1 (fr) 2007-02-22 2007-09-13 Procédé pour le traitement d'un substrat
PCT/US2008/009649 WO2009025739A1 (fr) 2007-08-17 2008-08-12 Procédé pour traiter un substrat

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Also Published As

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CN101827974A (zh) 2010-09-08
BRPI0815496A2 (pt) 2017-03-21
BRPI0815496B1 (pt) 2020-04-14
EP2179089A1 (fr) 2010-04-28
WO2009025739A1 (fr) 2009-02-26
CN101827974B (zh) 2015-10-21

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