Patent Application
20210222365
The present application relates to the field of coatings and, more particularly, to systems and methods for applying multi-layer coatings onto substrates, such as paper or paperboard substrates.
Typical systems and methods for applying two coating layers onto a paperboard substrate utilize two coating units, including drying and web handling components for each unit, resulting in significant capital expenditures for each unit, as well as operating and maintenance costs for each unit.
Accordingly, those skilled in the art continue with research and development in the field of coating systems and methods.
Disclosed are methods for applying a multi-layer coating onto a substrate, such as a paper or paperboard substrate.
In one example, the disclosed method for applying a multi-layer coating includes passing a substrate through a nip defined by two rolls to apply a first thickness of a first liquid coating material, applying a second liquid coating material on the first liquid coating material having the first thickness as applied by passing through the nip, and controlling a thickness of the applied second liquid coating material.
Also disclosed are systems for applying a multi-layer coating onto a substrate, such as a paper or paperboard substrate.
In one example, the disclosed multi-layer coating system includes a nip defined by two rolls. The nip is configured to apply a first thickness of a first liquid coating material to a substrate passing through the nip. The system further includes a topcoat applicator configured to apply a second liquid coating material on the first liquid coating material having the first thickness as applied by passing through the nip and a postmetering surface configured to control a thickness of the applied second liquid coating material.
Other examples of the disclosed method and system for applying a multi-layer coating will become apparent from the following detailed description, the accompanying drawings and the appended claims.
By reference herein to a “multi-layer” coating system and a “multi-layer” coating, it will be understood that the resulting coatings may include two layers or more than two layers. In other words, the multi-layer coating may include two layers, though third or additional coating layers may be applied before, during, or after utilization of the coating system and method herein described.
As shown in
Returning to
The outer cylindrical surface 10 of the applicator roll 8 may be positioned adjacent to the outer cylindrical surface 4 of the backing roll 2 to define a nip 14 therebetween for passing the substrate 100 therethrough.
By driving the applicator roll 8, a first liquid coating material 28 on the outer cylindrical surface 10 of the applicator roll 8 may be applied to the substrate 100 passing through the nip 14.
The first liquid coating material 28 may be provided to the outer cylindrical surface 10 of the applicator roll 8 in any manner. For example, as shown in
The amount of the first liquid coating material 28 provided to the outer cylindrical surface 10 of applicator roll 8 and applied to the substrate 100 may be have improved control by premetering a thickness of the first liquid coating material 28 provided on the outer cylindrical surface 10 of the applicator roll 8. For example, as shown in
In an aspect, the substrate 100 passing through the nip 14 defined between the outer cylindrical surface 4 of the backing roll 2 and the outer cylindrical surface 10 of the applicator roll 8 may be compressed therebetween. The pressure applied between the backing roll 2 and the applicator roll 8 may be, for example, a compressive pressure in a range of 5 to 150 pounds per linear inch. By applying a compressive force 16 between the outer cylindrical surface 4 of the backing roll 2 and the outer cylindrical surface 10 of the applicator roll 8, a method of the present description is facilitated, in which the substrate may be passed through the nip to apply a first thickness of a first liquid coating material, in which the first thickness of the first liquid coating material is maintained during a subsequent step of applying a second liquid coating material on the first liquid coating material, without necessitating a subsequent metering of the first liquid coating material. In particular, the first liquid coating material 28 may be more immobilized against the substrate 100 by the compressive force 16, facilitating the application of the second liquid coating material 48 on the first liquid coating material 28 without necessitating subsequent metering or drying of the first liquid coating material 28 and without significantly disturbing the first liquid coating material 28.
In another aspect, the first driving speed the outer cylindrical surface 10 of the applicator roll 8 may be substantially the same as the driving speed of the substrate and/or backing roll 2. In an example, a driving speed of the outer cylindrical surface 10 of the applicator roll 8 may be within 10% of a driving speed of the substrate 200 and/or backing roll 2. In another example, a driving speed of the outer cylindrical surface 10 of the applicator roll 8 may be within 5% of a driving speed of the substrate 200 and/or backing roll 2. In yet another example, a driving speed of the outer cylindrical surface 10 of the applicator roll 8 may be within 2% of a driving speed of the substrate 200 and/or backing roll 2. In yet another example, a driving speed of the outer cylindrical surface 10 of the applicator roll 8 may be within 1% of a driving speed of the substrate 200 and/or backing roll 2. In yet another example, a driving speed of the outer cylindrical surface 10 of the applicator roll 8 may be within 0.1% of a driving speed of the substrate 200 and/or backing roll 2.
By driving the outer cylindrical surface 10 of the applicator roll 8 at substantially the same as the driving speed of the substrate and/or backing roll 2, a method of the present description is facilitated, in which the substrate may be passed through the nip to apply a first thickness of a first liquid coating material, in which the first thickness of the first liquid coating material is maintained during a subsequent step of applying a second liquid coating material on the first liquid coating material, without necessitating a subsequent metering of the first liquid coating material. In particular, the first liquid coating material 28 may be more immobilized against the substrate 100, facilitating the application of the second liquid coating material 48 on the first liquid coating material 28 without necessitating subsequent metering or drying of the first liquid coating material 28 and without significantly disturbing the first liquid coating material 28.
By avoiding the need for intermediate metering, the method and system of the present description may be simplified. By avoiding the need for intermediate drying, detrimental effects through shrinkage for the first liquid coating material 28 may be avoided.
In a specific example, the substrate 100 passing through the nip 14 defined between the outer cylindrical surface 4 of the backing roll 2 and the outer cylindrical surface 10 of the applicator roll 8 is compressed therebetween and the outer cylindrical surface 10 of the applicator roll 8 and is driven at a substantially the same as the driving speed of the substrate and/or backing roll 2 to immobilize the first liquid coating material 28 against the substrate 100.
Referring to
Returning to
At this point, those skilled in the art will appreciate that the second liquid coating material 48 applied by the topcoat applicator 40 need not be the final (i.e., top-most) coating applied to the substrate 100. Additional layers of coating material may be applied over the second liquid coating material 48 without departing from the scope of the present disclosure.
The system and method of the present disclosure may further control an amount of the second liquid coating material applied on the substrate 100. Particularly, a thickness of the second liquid coating material applied on the substrate may be controlled. For example, as shown in
In an aspect, as shown in
In an aspect, the thickness of the second liquid coating material applied on the substrate is controlled by removing an excessive amount of the second liquid coating material applied on the substrate 100 by the topcoat applicator 40. The topcoat applicator 40 does not necessitate application of a controlled amount of the second liquid coating material 48.
Referring to
The first and second liquid coating materials are not yet in a dried state. The system and method of the present disclosure may further include drying the first and second liquid coating materials applied on the substrate. The method and devices for drying the first and second liquid coating materials are not limited.
The substrate 100 may be any suitable substrate material capable of being used with the exemplary system and method. As one specific, non-limiting example, the substrate 100 may be a paper substrate. As another specific, non-limiting example, the substrate 100 may be a paperboard substrate The paperboard substrate may be any web of fibrous material that is capable of being coated. The paperboard substrate may be bleached or unbleached, and may have an uncoated basis weight of about 85 pounds per 3000 ft2 or more. The paperboard substrate may be bleached or unbleached may be formed from virgin fibers, recycled fibers, or combinations thereof. Examples of appropriate paperboard substrates include corrugating medium, linerboard, solid bleached sulfate (SBS), secondary fiber such as recyclable, cup-stock and plate base paperboard, aseptic liquid packaging paperboard, and a combination of such materials.
Any substrate suitable liquid coating materials may be utilized for the first and second liquid coating materials. For example, the liquid coating materials may be paper or paperboard coatings, such as coatings containing pigment (e.g., clay and/or calcium carbonate) and binder (e.g., latex).
The first liquid coating material may have a different composition than the second liquid coating material. The coating system and method as described above enables for applying first and second coating layer having different compositions without necessitating separate coating units. However, the coating system and method is not limited to utilization of different coating materials. Thus, the first liquid coating material may have the same composition than the second liquid coating material.
By way of example, the first liquid coating material 28 may include an aqueous-based coating material. However, the first liquid coating material may include a solvent-based coating material.
By way of example, the second liquid coating material 48 may include an aqueous-based coating material. However, the second liquid coating material may include a solvent-based coating material.
Although various examples of the disclosed multi-layer coating system and method for applying a multi-layer coating have been shown and described, modifications may occur to those skilled in the art upon reading the specification. The present application includes such modifications and is limited only by the scope of the claims.
