The present invention relates generally to laminate structures, and more specifically to metal-polymer-metal laminates and methods of manufacturing the same.
Decorative panels that can be painted or finished for aesthetic purposes are utilized in various industries for innumerable products. Many conventional home appliances, for example, have a number of external surfaces that are visible after installation which can consist of a decorative panel. Specifically, dishwashers, trash compactors, stoves, and most other kitchen appliance can have a decorative front surface.
It is often desired that the decorative surface provide a “finished metallic look”. In addition to home appliances, decorative surfaces with a “finished metallic look” may be used for decorative metal faced building panels, metal faced sectional water tanks, and metal faced components for the automotive industry. However, the use of certain monolithic metal substrates to provide the desired “finished metallic look” for the decorative surface may be limited due to the high cost of the metallic materials—e.g., titanium, stainless steel, nickel, copper, and other expensive metal sheet stock.
Some prior art attempts have been made to mitigate the costs of using certain monolithic metal substrates to provide a “finished metallic look” for decorative surfaces. One proposal is to reduce the thickness or gauge of the monolithic panel and, thus, the total volume of material being used. However, reducing the thickness of the monolithic metal substrate may eventually reduce its robustness (e.g., reducing structural or surface integrity), and may eliminate certain post processing operations, such as brushing, polishing, embossing, or other decorative finishes imparted by mechanical means, due to minimal thickness requirements.
Another proposal has been to use electroplating, electrodeposition, and other similar processes to coat a substrate of lesser expensive metal with a film of the more expensive and more aesthetically appealing metallic material. Unfortunately, the electroplated surface will read through (or telegraph) the appearance of the substrate surface to which it is coating. Moreover, the extremely thin layers produced by electroplating have a limited life expectancy, are expensive to produce, and are prone to damage under certain post processing operations.
It has also been proposed to “metalize” a surface of a polymeric panel to create the desired “finished metallic look” for a decorative surface. However, the peel strength of the metal-film polymer laminate is often insufficient for many processing and post-processing operations and, thus, the metal-film layer is susceptible to delamination. That is, the mechanical stresses generated when first forming the metal on the polymeric substrate and in subsequent processing steps can cause the metal-film to distort or flex, which may cause the metal to bubble on and/or peel away from the substrate. Film laminates also do not have the same chemical resistance or scratch resistance, and cannot be repaired the same as solid metal when scratching, staining, etc., occurs.
The present invention provides a metal-adhesive-metal laminate, and a method of manufacturing the same, which reduces the cost of expensive monolithic metal substrates, such as, but not limited to, stainless steel, titanium, brass, nickel, and copper. The methods of the present invention eliminate substantially all facial defects and read through appearance on the decorative surface of the metal laminate, which might otherwise be expected when using an adhesive beneath a thin sheet of metal. As such, the resultant metal-adhesive-metal laminates of the present invention look identical to their monolithic metal counterparts, yet are substantially less expensive. In addition, the present invention provides a bimetal laminate with improved durability, which can be roll-formed without the edges delaminating, and has the ability to be post processed—e.g., welded, formed, stamped, painted, brushed, clear coated, etc., using existing techniques and equipment without failing.
According to one embodiment of the present invention, a method of manufacturing a metal laminate structure is provided. The method includes: applying a first layer of adhesive to an interface surface of a supporting metallic substrate; and laminating an inner surface of a decorative metallic sheet to the interface surface of the supporting metallic substrate in such a manner that substantially all surface defects and read through (also known as surface telegraphing) along an outer surface of the decorative metallic sheet are eliminated.
According to one aspect of this embodiment, the first layer of adhesive is applied via a finish coater that is configured to increase wet out of the first layer of adhesive. As used herein, the term “wet out” should be defined or interpreted to indicate a liquid's or adhesive's natural ability to flow or spread out evenly and, thus, intimately covers the surface to which it is applied. To this regard, the finish coater preferably includes an applicator roll positioned adjacent the metallic substrate, and operable to apply the first layer of adhesive thereto in a substantially continuous manner. The applicator roll has a kiss pressure that is selected to increase wet out of the first layer of adhesive. Alternatively, or in addition thereto, the finish coater further includes a pickup roll positioned a first distance from the applicator roll and operable to transfer adhesive thereto. The first distance is also selectively modified to control the thickness of the wet film and to increase wet out of the first layer of adhesive. In addition, the applicator roll is configured to rotate at a first speed, whereas the pickup roll is configured to rotate at a second speed. The first and second speeds are preferably also selectively modified to obtain the specific targeted film thickness and to maximize the wet out of the first layer of adhesive.
According to another aspect of this embodiment, laminating the inner surface of the decorative metallic sheet to the interface surface of the metallic substrate includes: heating the metallic substrate to a first temperature; heating the decorative metallic sheet to a second temperature; and compressing the decorative metallic sheet together with the metallic substrate. Heating the decorative metallic sheet is selectively modified so as to achieve a predetermined temperature difference between the first and second temperatures prior to compressing the decorative metallic sheet together with the metallic substrate (e.g., a temperature where the two layers will shrink together at roughly the same amounts and thus minimize any forced shape). Ideally, a second layer of adhesive is applied to the decorative metallic sheet prior to compressing the decorative metallic sheet together with the metallic substrate.
In accordance with another aspect of this embodiment, compressing the decorative metallic sheet together with the metallic substrate includes passing the decorative metallic sheet and metallic substrate through a nip press in a substantially continuous manner. The nip press has a lamination pressure that is selected such that substantially all deformation of the decorative metallic sheet resulting from compressing the decorative metallic sheet together with the metallic substrate is eliminated. Ideally, the lamination pressure of the nip press is less than 80 pounds per square inch (psi).
In accordance with yet another aspect, the method of the present invention also includes: applying a first coating of metal pretreatment to the inner surface of the decorative metallic sheet prior to laminating the decorative metallic sheet to the metallic substrate; and applying a second coating of metal pretreatment to the interface surface of the metallic substrate prior to applying the first layer of adhesive thereto. The first and second coatings of metal pretreatment help to facilitate laminating of the inner surface to the interface surface (e.g., create complementary surfaces conducive to lamination).
In accordance with another embodiment of the present invention, a metal laminate structure is provided. The metal laminate structure includes a decorative metallic layer consisting of a first metallic material. The metal laminate structure also includes a metallic substrate layer consisting of a second metallic material that is different from the first metallic material. The metal substrate layer has a thickness that is greater than the thickness of the decorative metallic layer. An adhesive layer is disposed between, and spans substantially the entirety of the decorative metallic layer and the metallic substrate layer to rigidly attach the same. The decorative metallic layer has opposing inner and outer surfaces. The outer surface is characterized by an absence of substantially all surface defects and read through appearance.
According to one aspect of this embodiment, it is desired that the liquid adhesive have a viscosity of less than 1440 Centipoise (cps) prior to roll application to facilitate smooth surface formation. In addition, the decorative metallic layer preferably has a thickness of approximately 0.102-0.305 millimeters (4-12 mils). In contrast to the decorative metallic layer, the metallic substrate layer has a thickness of approximately 0.203-1.524 millimeters (8-60 mils).
According to another aspect of this embodiment, the decorative metallic layer is characterized by a surface with an appearance finish, whereas the metallic substrate layer is characterized by the absence of a surface with an appearance finish. As used herein, the term “appearance finish” should be defined or interpreted to indicate a surface refinement such as, but not limited to, a shine, glaze, texturing, varnish, polish, brushing, staining, or topical treatment.
The above features and advantages, and other features and advantages of the present invention will be readily apparent from the following detailed description of the preferred embodiment and best modes for carrying out the present invention when taken in connection with the accompanying drawings and appended claims.
Referring to the drawings, wherein like reference numbers refer to like components throughout the several views,
The laminate structure 10 of
The decorative metallic layer 12 consists of a first metallic material, whereas the metallic substrate layer 14 consists of a second metallic material that is different from the first metallic material. Specifically, the decorative metallic layer 12 may be any of a variety of decorative metal types, which is inclusive of, but not exclusive to, 304(L) stainless steel alloy, 430 stainless steel alloy, copper foil alloy C11000, brass alloy C260, titanium alloy, nickel alloy, etc. In contradistinction, the metallic substrate layer 14 is formed from a material with the necessary stiffness and structural durability for the metallurgical characteristics of the decorative metallic layer 12 and the intended application of the laminate structure 10. By way of example, metallic substrate layer 14 is preferably fabricated from high strength, low cost metal sheet stock, which may include, but is not limited to, cold rolled steel, electro-galvanized steel, hot-dip galvanized steel, tin free steel, and tin mill black plate steel.
The decorative metallic layer 12 has opposing inner and outer surfaces, identified in
The layer of adhesive 16 consists of those adhesives, whether natural or synthetic, which provide sufficient bonding strength for the decorative metallic layer 12, and sufficient resiliency to withstand the manufacturing environment and post processing operations for fabricating the laminate structure 10. Purely by way of example, the layer of adhesive 16 may be a cold-forming PSA acrylic adhesive, dry-bond adhesive, such as polyester urethanes, and the like. However, as will be described in extensive detail hereinbelow, the viscosity of the layer of adhesive 16 is minimized to promote “wet out” during fabrication of the laminate structure 10. As used herein, the term “wet out” should be defined or interpreted to indicate a liquid or viscoelastic adhesive's natural ability to flow or spread out evenly and, thus, intimately covers the surface to which it is applied (liquid beading being an antithetical example of wetting out). According to preferred practice, it is desired that the adhesive layer 16 have a viscosity of less than 1440 Centipoise (cps), and preferably 200-500 cps. Notably, the thickness and composition of the layer of adhesive 16 may be modified to tailor to the precise bond strength, overall stiffness, and additional characteristics dictated by the specific application of the laminate structure 10.
As seen in
An exemplary coil coating and lamination assembly for practicing the methods of the present invention is schematically shown in
Referring first to
After the decorative metallic sheet 22 is properly cleaned, it is fed or passed through a first coating device, such as top coater 24. The top coater 24 is operable to apply a layer or coating of preferably organic-type metal pretreatment to an inner surface (i.e., inner surface 15 of
The layer of adhesive 16 (shown in
In pass two P2 of the coil coating and lamination process, which is schematically illustrated in
With continuing reference to
The finish coater 48 is configured to increase wet out of the first layer of adhesive 16. For example, the applicator roll 43 has a kiss pressure that is selected or optimized to increase wet out of the first layer of adhesive 16. Specifically, the applicator roll 43 is designed with an almost perfectly smooth surface. By selectively increasing the kiss pressure of the very smooth applicator roll 43 based upon the viscosity and shear strength of the type of adhesive being applied, an almost glass-like layer of adhesive 16 is achieved. Alternatively, or in addition thereto, the first distance D1 between the applicator roll 43 and pickup roll 45 can also be selectively modified to increase wet out of the first layer of adhesive. That is, the distance D1 may be set to a predetermined optimal distance in order to optimize the pressure between the pickup roll 45 and applicator roll 43, as well as provide the most favorable thickness of adhesive transferred thereto. In addition, the applicator roll 43 is configured to rotate at a first speed (represented for explanatory purposes by arrow V1 in
The adhesive-coated metallic substrate is thereafter passed through a heating device, such as fourth oven 50, which increases the temperature of the metallic substrate 42 to a first temperature, dries the adhesive layer, and reacts the glass-like adhesive surface in place for subsequent lamination of the metallic substrate 42 and decorative metallic sheet 22. By heating the adhesive-coated metallic substrate, for example, to 385 degrees Fahrenheit (° F.), the pretreated interface surface (i.e., 17 of FIG. 1) and adhesive coating (i.e., layer of adhesive 16 of
Once the first and second strips of sheet metal 22, 42 are cleaned, pretreated, and coated with adhesive, the two are thereafter laminated or married together in such a manner that substantially all surface defects and read through (also known as surface telegraphing) along the outer surface 13 of the decorative metallic sheet 12 are eliminated. According to the arrangement of
The thermally activated decorative metallic sheet 22 and metallic substrate 42 are then compressed together, for example, by passing the sheets 22, 42 through a set of nip rolls (referred to collectively as “nip press”), defined by mutually coacting and opposing lam rolls 54, in a substantially continuous manner, to form the laminate structure 10. The nip press—i.e., lam rolls 54, has a lamination pressure that is selected or modified such that substantially all deformation of the decorative metallic sheet 22 resulting from compressing the decorative metallic sheet 22 together with the metallic substrate 42 is eliminated. Although 80-120 pounds per square inch (psi) may be used to laminate, the lamination pressure of the nip press of
Post lamination cooling should occur slowly in order to allow metallic layers (i.e., 12 and 14 of
While the best modes for carrying out the present invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention within the scope of the appended claims.