Patent Application
20100096386
The present invention relates generally to plastic containers having digital images printed thereon, particularly containers having improved adhesion and recycling characteristics and methods for digitally printing containers and facilitating recycling.
Product manufacturers commonly impose labeling standards on plastic containers that are intended to hold their products. Various tests, including a number of industry standardized tests, have been used to measure and evaluate the quality of label application. Some standard test methods that have been employed include, by way of example and without limitation, ASTM International test designations D 3359-08 (Standard Test Methods for Measuring Adhesion by Tape Test); D 5264-98 (Standard Practice for Abrasion Resistance of Printed Materials by the Sutherland Rubber Tester); and F 1842-02 (Standard Test Method for Determining Ink or Coating Adhesions on Plastic Substrates for Membrane Switch Applications). Product manufacturers often define testing requirements and resultant scores that should be met for a labeled product to be deemed acceptable.
Container manufacturers have recently produced containers with digitally printed labels that are of a sufficient definition and quality to compete with and potentially replace prior conventional labeling techniques. Examples of such printing techniques are described in U.S. patent application Ser. No. 11/562,655, which is incorporated herein by reference. However, for many applications, it is desirable to utilize standards for providing, measuring, and assessing printed images that may serve as labels.
Potential challenges arise introducing containers with digitally printed labels into conventional container recycling processes. There is a clear trend amongst container manufacturers, brand owners, end users, and governmental entities to improve and increase container recycling efforts. Consequently, it would be desirable to provide industry-acceptable containers that are sufficiently compatible with the current recycling infrastructure and processes, or that provide sufficient incentive and/or volumes to effectuate industry-wide changes. At least initially, it would be desirable to provide digitally printed containers that are recyclable using current industry standard processes—i.e., processes that commonly include caustic high-temperature washing and grinding. As such, there is a desire for digitally printed plastic containers that have digital images that adhere to the container without quality issues throughout its useful life, but are readily removable during plastic recycling processes.
A plastic container is disclosed that has an external surface with a digital image printed thereon by droplets of ink. The digital image includes a base coat and a secondary coat that is applied to the base coat. Embodiments of the invention disclose containers having improved adhesion and/or recycling characteristics. In an embodiment, the digital image adheres to the plastic container and the digital image has an acceptable or “passing” adhesion score (which for some scoring systems is a score of 6.0 or greater). Methods for digitally printing containers and facilitating recycling are also disclosed.
Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, wherein:
Reference will now be made in detail to embodiments of the present invention, examples of which are described herein and illustrated in the accompanying drawings. While the invention will be described in conjunction with embodiments, it will be understood that they are not intended to limit the invention to these embodiments. On the contrary, the invention is intended to cover alternatives, modifications and equivalents, which may be included within the spirit and scope of the invention as defined by the appended claims.
A portion of a surface 10 of a container with a printed digital image 20 is generally illustrated in
The base coat 30 may be comprised of a material that serves to improve the application of ink droplets and/or provides a visual characteristic. For embodiments, the base coat 30 may comprise white and/or colorless portions. In embodiments of the invention, at least a first base coat 30 is applied to a surface of a container at a first time t1 and at a first temperature T1. The temperature T1 will be in the range of temperatures that are appropriate for application of the associated base coat. In an embodiment, the base coat 30 may be ultraviolet (UV) curable, and further may be cured prior to an application of a secondary coat.
The secondary coat 40 may be comprised of a plurality of secondary coat ink droplets 42 that are distributed on at least a portion of the base coat 30. A plurality of secondary coat ink droplets 42 may collectively form a part of an application pattern which, in turn, may form all or a portion of a digital image. Furthermore, as generally illustrated in
In embodiments of the invention, the time between application of a base coat and the application of a secondary coat (e.g., t2 minus t1) may be reduced—for example, to as little as ten seconds or less. For some embodiments, the application time differential will be within two to six seconds. Moreover, in embodiments, the application temperature differential between the temperature at which the base coat 30 is applied and the temperature at which a secondary coat 40 is applied to a portion of the base coat 30, i.e., T1 minus T2, may be controlled to be equal to or less than about 10° F. For some embodiments, the application temperature differential will be within about 5° F. to about 10° F. Moreover, for some applications, it may be desirable to modify the temperatures associated with the application of the base coat 30 and the secondary coat 40 so that the respective application temperatures are closer together—i.e., so that the temperature differential between the applied coats is reduced or minimized. This can be accomplished, for instance, by (a) lowering/decreasing T1, (b) raising/increasing T2, or (c) a combination of (a) and (b). Such aforementioned time and/or temperature control with respect to the base coat and secondary coat can provide for better adhesion of the resulting printed digital image with respect to the container.
It is noted that in addition to time and temperature, irradiance is a factor that can also affect the effective cure rate for a printed image. That is, with certain times (e.g., t1 and t2) and temperatures (e.g., T1 and T2), there may be an associated irradiance—i.e., ε1 and ε2. For example, in embodiments a base coat may be cured at irradiance ε1, and an associated secondary coat may be cured at irradiance ε2. Further, in embodiments, the effective cure rate—which may be based on a combination of time, temperature, and irradiance—the irradiance may generally be provided by the following equation:
Irradiance(ε)=(dφ/dA)
The containers (which includes bottles) associated with the present invention are comprised of a plastic material (e.g., PET, HDPE, PP, PE, etc.). The containers may be mono-layer or multi-layer containers, and can be formed using various conventional forming techniques including, without limitation, blow molding, thermoforming, etc. In an embodiment, the outermost layer/surface is comprised of a virgin plastic material. Although, it is noted that containers in accordance with the teachings of the invention may include some percentage of recycled content, including a small percentage (e.g., 20% or less) in the outer layer of the container.
For some applications, such as where a curable ink (e.g., a UV-curable ink) is used, the relevant coat or ink may be cured after each respective print station. For example, without limitation, an embodiment of a process may, at least in part, comprise: application of base coat; cure step; application of secondary coat; and cure step. Alternatively, also by way of example and without limitation, the process may, at least in part, comprise: application of base coat; cure step; application of base coat; cure step; application of secondary coat, and cure step. Moreover, for embodiments of the invention, it can be desirable for the production/subsequent handling rate of containers/bottles to match or substantially match the flow/processing rates of the associated printing machine(s).
Further, it has been found that the quality of printed digital images may be, at least in part, controlled and/or improved through one or more of the following techniques:
(a) selection and/or calibration of ink sets;
(b) control of substrate (i.e., container surface) temperature; and/or
(c) timing control.
With respect to the selection and/or calibration of ink sets, this is accomplished, at least in part, by the selection and/or calibration of the inks comprising the base and secondary coats. It has been discovered that the inks used can be selected to provide desired time and/or temperature characteristics, including relative to one another in combination. For example, selection of certain inks having given viscosities can exhibit or provide certain desired temperature related effects.
With regard to the control of the substrate (i.e., container surface) temperature, the temperature of a relevant portion of a sidewall (or other portion of a container) can be treated or controlled to some measure. For example a given portion of the container can be pre-treated. Such pre-treatment can be facilitated using various known techniques that may include, without limitation, flame, corona, and plasma treatment. However, the invention is not limited to those specific pre-treatment techniques.
With respect to timing control, the time associate with the movement of containers, for instance through a production machine, as well as the timing of the applications of the base coat and/or secondary coat, can be controlled. It can be desirable for the production/subsequent handling rate of containers/bottles to match or substantially match the flow/processing rates of the associated printing machine(s).
The present invention also includes a system for assessing or evaluating the “acceptability,” such as the commercial acceptability, of a container having a digitally printed image—such as a digitally printed label. That is, for embodiments of the invention, the system for assessing or evaluating can provide an “adhesion score.”
In an embodiment, it is desirable to provide a container with a printed digital image that, at a minimum, passes a modified 3M #610 tape test and is nonetheless “recyclable.” A digital image that is printed on a container is considered to be “recyclable” if it would achieve less then a “4B” classification (i.e., 5% of more of the area is removed) employing an ASTM D 3359 standard #810 tape test. A container with a digital image that passes Test 2 (modified 3M #610 Tape Test) and Test 3 (Simulated Ship Test), yet fails Test 4 (3M #810 Tape Test), would achieve an adhesion score of either 6.0 or 7.0. Such a container with a printed image having an adhesion score of 6.0 or 7.0 is commercially suitable for shipment (i.e., passing a Simulated Ship Test) while providing an adhesion associated with the printed image that is sufficient for normal/intended use but is favorably separable for subsequent recycling. Stated differently, the adhesion associated with the configured digital image is sufficiently strong for intended use but does not impede separation during recycling.
With respect to such a table/matrix, each test may be conducted on a adequate (e.g., statistically significant or representative) sampling of containers. After all tests are completed, results may be tabulated and entered into the table/matrix, to provide an “adhesion” score. The associated score outcomes can then be correlated.
Among other things, the present invention can provide for improved recyclability. For example, without limitation, containers with digitally printed images (which may be formed by cured UV-curable ink) can be conveniently removed in connection with conventional plastic recycling processes. Industry standard recycling process of plastic containers conventionally include grinding containers into granulated plastic flakes, subjecting these flakes to a high-heat caustic wash process, drying the cleaned flakes, sorting, and extruding into resin pellets for resale. With embodiments of the invention, digital image on the container may remain with the resin flakes after the grinding process, the digital image will be substantially separated from the resin flakes during the high-heat caustic wash process, thereby not contaminating the clean resin flakes to be formed into resin pellets.
The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and various modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to explain the principles of the invention and its practical application, to thereby enable others skilled in the art to utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto and their equivalents.
This application claims the benefit of U.S. provisional patent application Ser. No. 61/106,860, filed Oct. 20, 2008, which is incorporated by reference in its entirety as if fully set forth herein.
| Number | Date | Country | |
|---|---|---|---|
| 61106860 | Oct 2008 | US |
