HK1185319B - Recyclable printed plastic container and method - Google Patents

Description

Recyclable printed plastic container and method

Related application

Priority of united states patent application No. 13/168,181, filed 24/6/2011, is claimed in this application, which is incorporated by reference herein in its entirety. United states patent application number 13/168,181 claims the benefit of provisional application number 61/360,512 filed on 1/7/2010.

Technical Field

The present invention generally relates to plastic articles having digital images printed thereon, including plastic containers having digital images with improved adhesion and/or recycling characteristics, and methods for facilitating recycling.

Background

The amount of recovery utilized by the plastics industry is still increasing. Container manufacturers have recently begun producing containers with digitally printed labels that are highly legible, of good quality, comparable to, and potentially replacing, existing conventional labeling techniques. Examples of these printing techniques are described in commonly owned U.S. patent No. 7,625,059 and U.S. patent No. 7,736,713, both of which are incorporated by reference herein in their entirety.

Challenges may arise in introducing containers with digitally printed labels into conventional container recycling processes. Some of the challenges have been mentioned and discussed in U.S. patent application No. 12/581,952, which is incorporated herein by reference in its entirety. The trend is clear for container manufacturers, brands, end users, and government agencies, to improve and enhance the recycling of plastic containers. Accordingly, there is a need to provide industry-acceptable articles that are sufficiently compliant with current recycling infrastructure and processes, or that provide sufficient incentive and/or numbers to make industry-wide changes. It is desirable, at least initially, to provide a digital printed article that can be recycled using standard processes in the current industry (i.e., processes that typically include alkaline high temperature washing and grinding). Thus, there is a need for digitally printed plastic articles, e.g., containers, having digital images that adhere to the article without quality problems over the lifetime of the article, but that are easier to remove during plastic recycling.

Disclosure of Invention

A recyclable plastic article having a digital image printed on an outer surface thereof by cured ink droplets is disclosed. The ink droplets may be monomer-based and may include an ink composition that includes a removal-promoting additive (removal-promoting). The removal-promoting additive may include a hydrophilic component and/or an acidic component, and may be configured or composed to cause the solidified ink droplets to separate from or loosen from the outer surface of the article when the digital image is exposed to a liquid-based (e.g., water-based) solution at or about a predetermined elevated temperature. Such predetermined elevated temperatures may include, but are not limited to, those temperatures associated with conventional recovery processes. Various embodiments of methods for facilitating such recovery are also disclosed.

Drawings

Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:

FIG. 1 generally shows a side view of a portion of a plastic container with an embodiment of a digital image printed thereon;

fig. 2 is a general representation of a quality review table/matrix that can be used to evaluate the acceptability of printed images on plastic articles.

Detailed Description

Reference will now be made in detail to the 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 the 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.

With general background and without limitation, fig. 1 generally illustrates a portion of a plastic article (e.g., container) surface 10 having an embodiment of a printed image 20. The illustrated embodiment of the image 20 includes a primer layer 30 that may be comprised of a plurality of primer layer ink drops 32, and may also include a secondary coating layer 40 that may be comprised of a plurality of secondary coating ink drops 42.

Containers, including bottles, associated with the present invention are composed of plastic materials or resins (e.g., Acrylonitrile Butadiene Styrene (ABS), polyethylene terephthalate (PET), Polystyrene (PS), Polyethylene (PE), including High Density Polyethylene (HDPE), polypropylene (PP), polyvinyl chloride (PVC), etc.). Further, the container may be a single layer container or a multilayer container and may be formed using a variety of conventional forming techniques including, but not limited to, injection molding, blow molding, thermoforming, and the like. In one embodiment, the outermost layer/surface may be composed of a pure plastic material. It should be noted, however, that containers according to the teachings of the present disclosure may also include a percentage of recycled content, including a percentage of recycled content in the outer layer of the container.

In various embodiments, an article (e.g., a container) can include a first coating or primer layer (e.g., primer layer 30 shown in fig. 1). The primer layer 30 may be comprised of a plurality of primer layer ink drops 32 that are printed (e.g., digitally printed using a drop-on-demand ink jet process, etc.) on the outer surface of the article and subsequently cured or allowed to cure. The ink may be a UV curable ink that may be cured by UV radiation applied by a variety of known means, including, but not limited to, UV lamps or LED lamps. The ink droplets may be monomer based and consist of an ink composition that is used to improve the application of the ink droplets (e.g., to provide good processing characteristics for printing), and/or to provide visual characteristics (e.g., color or texture). For various embodiments, the primer layer 30 may include white and/or colorless portions. Further, with the disclosed ink droplets, i.e., those based on monomers, the curing process can cause the ink droplets to polymerize. Because the ink used is not solvent based, the ink can be combined so that the ink does not bleed into solution and emit volatiles during recycling as does the solvent. It should be noted that the united states Environmental Protection Agency (EPA) has issued guidelines for solvents, however, polymers are solids and do not flash off or emit volatiles. That is, the inks as disclosed herein can be separated mechanically in nature because the inks are in a cured polymer state and can be physically removed (e.g., in the form of a sheet or film) rather than added as part of a chemical dissolution.

Further, according to the teachings of the present invention, the ink composition constituting the ink droplets may include a removal promoting additive. The "removal-promoting additive" includes at least one hydrophilic component or acidic component. The hydrophilic component may include one or more constituent elements that exhibit hydrophilic (water-loving) properties. The acidic component may include one or more constituent elements that exhibit acidic properties. For some embodiments, the removal-promoting additive will include a combination of a hydrophilic component and an acidic component, i.e., at least two removal-promoting additives. For some ink drop compositions, i.e., a "dual" composition in which the removal-promoting additive includes both hydrophilic and acidic components, a smaller weight percentage (compared to the total) may be used to obtain comparable results to using a composition with only a single additive.

Such hydrophilic components may include hydrophilic monomers, hydrophilic oligomers, and water-dispersible monomers that provide the desired functionality. Hydrophilic monomers are generally characterized by having oxygen or nitrogen atoms in their backbone structure in addition to halogens. Such monomers are generally susceptible to polar solvents such as water and ketones. Hydrophilic monomers are also less resistant to thermal degradation. Thus, the addition of one or more hydrophilic components to the associated ink drops can facilitate the separation of the image (i.e., the solidified ink drops) from the plastic structure of the article at some later time (e.g., at a post-consumer recycling time). By way of example and without limitation, in the cured state, the hydrophilic portion of the polymer will generally absorb water. When this occurs, water can act as a plasticizer, increasing the mobility of the polymer chains. The increased flowability may cause the polymer to soften and thus be easier to remove. Thus, exposing a plastic article, such as a container, including an image comprised of an ink composition having a removal-promoting additive (e.g., a hydrophilic monomer) to a liquid-based solution at elevated temperatures (e.g., agitated water) can facilitate softening of the ink composition (i.e., the hydrophilic monomer) and separation of the image from the plastic material. The elevated temperature may be predetermined and may be a temperature higher than the temperature typically encountered by the article during normal use. Furthermore, if desired, the adhesion-separation threshold may be established such that softening and subsequent removal occurs substantially only at elevated temperatures (e.g., during recycling), and not during substantially normal intended use. It should be noted that aliphatic urethane acrylates are a general class of hydrophilic monomers, which absorb water in general and are likely to act as hydrophilic components. Furthermore, if some hydrophilic oligomers are suitably viscous (i.e., not too viscous) for inkjet/digital printing applications, they can also be used as hydrophilic components.

Without limitation, for some embodiments, the removal-promoting additive may include a hydrophilic monomer in a weight percentage to total weight (i.e., the total weight of the associated ink and the removal-promoting additive) in a range of from approximately 0 wt% up to 20 wt%. For some embodiments, the weight percent of the removal-promoting additive will fall within a range of approximately 0 to 10 percent of the total weight. Without limitation, one example of a hydrophilic monomer that may be used is methoxypolyethylene glycol monoacrylate (e.g., CD553 commercially available from sartomera, LLC (sartomera), usa).

It should be noted that some water-dispersible monomers are also hydrophilic and appear to absorb water upon curing. With such a composition, water can act as a plasticizer and soften the cured ink composition (e.g., the cured ink film on the surface of the container), thereby making it easier to remove the ink film during recycling processes. In various embodiments of the present invention, the addition of suitable hydrophilic components to the ink composition can impart hydrophilic properties to the ink while allowing the ink to be jetted and adhered to the substrate of the article throughout the lifetime of the article.

The acidic component comprises an acidic monomer having a measurable acid value. It should be noted that measurable amounts may be based on pH, acid weight percent, or titration value of alkaline chemicals (e.g., mgKOH/g [ mg potassium hydroxide per gram monomer ]). Further, for example, in the cured state, the acidic portion of the polymer may be susceptible to alkaline solutions. Reactions between the acidic function of the polymer chain and the alkalinity of the solution can result in reduced adhesion to the substrate to which it is applied, thereby facilitating polymer separation. Without limitation, examples of acidic monomers that may be used include acidic acrylate oligomers (e.g., CN147, available from sardoxa), and monofunctional acid esters (e.g., CD9050, available from sardoxa). For example, when a container containing an acidic component is contacted with a washing liquid (wash), such as a conventional type of alkaline washing liquid, the relevant bond is broken, thereby promoting the intended separation of the printed image (ink droplets) from the plastic substrate.

By way of example and not limitation, an embodiment of a polyethylene terephthalate (PET) container comprising a UV curable printing ink with a hybrid removal-promoting additive performs an ink removal test. The mixed removal promoting additives for the tested containers included acidic monomers of the type described above, i.e., acidic acrylate oligomers and/or monofunctional acid esters. The container may be subjected to an electrolyte having a pH of at least 9.0 which may assist in label removal, as is well known in the art of recycling plastic containers, wherein the electrolyte is heated to about 85 ℃. Each sample was exposed to this condition for 12 minutes and evaluated according to the following scale 0 to 5:

0-No improvement in removal compared to control sample

1-little improvement is observed: by wearing with metal objects, only some areas are removed

2-some improvement was observed: by scraping with a metal object, the entire film can be removed

3-removal of the cured ink film by scraping with a fingernail

4-simply wiping with a clean rag, the cured ink film can be easily removed

5-during the flushing test, the cured ink film fell.

The test is intended in particular to determine the removal performance level of solutions which provide a level of 4 or 5. However, a level of at least 4 is not necessarily required, and lower removal levels may be acceptable for some applications. The test results show that the addition of the mixed removal-promoting (acidic) additive to the ink composition significantly aids in the removal of the cured ink from the Plastic (PET) material. Although both forms of acidic additives facilitate ink removal, a slightly lower composition percentage of acidic acrylate oligomer (15% and 10%, respectively) can be used compared to the monofunctional ester to achieve a removal level of at least level 4 in the case of the rapid test configuration.

In various embodiments, the ink composition may optionally include a hydrophobic component. That is, for example, the ink composition may include a hydrophilic component and a hydrophobic component. The hydrophobic component may comprise a hydrophobic monomer. Hydrophobic properties generally relate to polarity. Many hydrophobic monomers are characterized by having an organic backbone structure composed primarily of hydrogen and carbon, and thus, such monomers tend to be non-polar and resistant to polar solvents (e.g., water and alcohols), as well as acids and bases. For such two-component embodiments, the ink composition should balance hydrophilic components with hydrophobic components (e.g., hydrophilic monomers with hydrophobic monomers). The hydrophobic monomer can help keep the ink droplets adhered to the article substrate, while the hydrophilic monomer can help soften (or even separate) when the image is exposed to the recycling process/electrolyte (e.g., whipped water at high temperatures).

To the upperAn embodiment of a container having an image printed thereon may be at least at a first time t₁And a first temperature T₁Next, a first primer layer 30 (which may include a hydrophilic component) is applied to the surface of the container. First temperature T₁Will be in a temperature range suitable for application of the relevant primer layer. In one embodiment, the primer layer 30 may be cured (e.g., Ultraviolet (UV) cured), and may be further cured prior to application of the secondary coating.

For some embodiments, the secondary coating 40 may be comprised of a plurality of secondary coating ink droplets 42 distributed over at least a portion of the primary coating 30. In addition, additional layers of "secondary" coatings (e.g., tertiary coatings, etc.) may also be applied over the secondary coating 40, as desired. In various embodiments of the present invention, the secondary coating ink droplets 42 may also be comprised of an ink composition that includes a hydrophilic component.

Collectively, the plurality of secondary coating ink droplets 42 may form a portion of the coating pattern, which in turn may form all or a portion of the image. Further, portions of one or more adjacent secondary coating ink droplets 42 may overlap or mix with one another, as generally shown in FIG. 1. The secondary coating 40 and the component secondary coating ink droplets 42 may include a variety of known colors including, but not limited to, cyan, magenta, and yellow, among the primary print colors. Furthermore, controlling the overlap or combination of certain colors in certain areas may provide additional "process" colors. In addition, the secondary coating ink droplets 42 may be cured. For example, the UV cured secondary coating ink droplets may comprise all or a portion of the intended image. If curing is accomplished by radiation, the ink composition may include a photoinitiator. It should also be noted that the cured ink on the container surface may be held first by two bonds, namely a polar bond between the ink polymer and the plastic, and a mechanical bond formed by the plastic surface having an uneven surface on a microscopic level (e.g., microstructure). For many embodiments of the present invention, it is preferable to break both keys. For some applications, the hydrophilic component may perform better at mechanical bonds, while the acidic component may perform better at polar bonds. Of ink droplets for secondary coating, depending on the applicationThe diameter may vary, ranging, for example, from about 10 microns to about 200 microns. At a second time t₂And a second temperature T₂Next, a secondary coating 40 may be applied to the surface 10 of the container, wherein the secondary coating 40 is applied at a second temperature T₂Is generally greater than the first temperature T at which the primer layer 30 is applied₁Low.

In various embodiments of the invention, the time (e.g., t) between the application of the primary coating and the application of the secondary coating₂Minus t₁) May be reduced, for example, to ten seconds or less. For some embodiments, the coating time difference will be within two to six seconds. Further, in various embodiments, there is a coating temperature differential, i.e., T, between the temperature at which the primary coating 30 is applied and the temperature at which the secondary coating 40 is applied over a portion of the primary coating 30₁Minus T₂The coating temperature differential may be controlled to be equal to or less than about 10 ° F. For some embodiments, the coating temperature differential will be within about 5 ° F to 10 ° F. Furthermore, for some applications, it may be desirable to modify the temperatures associated with applying the primary coating 30 and the secondary coating 40 so that the respective application temperatures are closer together, i.e., so that the temperature difference between the applied coatings is reduced or minimized. This can be done, for example, by: (a) reduction/reduction of T₁(b) increasing/increasing T₂Or (c) a combination of (a) and (b). Such time and/or temperature control as described above with respect to the primary and secondary coatings may provide better adhesion of the resulting printed image to the article.

It should be noted that in addition to time and temperature, irradiance is also a factor that can affect the effective cure rate of the printed image. That is, at a particular time (e.g., t)₁And t₂) And temperature (e.g., T)₁And T₂) There may be an associated irradiance, i.e.,₁and₂. For example, in various embodiments, the primer layer may be at an irradiance₁Curing is performed while the associated secondary coating may be at irradiance₂Then, curing is carried out. Further, in various embodiments, the effective cure rate may beBased on the combination of time, temperature, and irradiance, irradiance may be generally provided by the following equation:

irradiance () = (d phi/dA)

Where Φ = irradiation flux (in watts) and a = area (cm)²）。

For example, without limitation, for some embodiments the irradiance will range from about 0.1 watts/cm²And about 10.0 watts/cm²In the meantime.

For some applications, for example, applications using a curing ink (e.g., a UV-curable ink or a radiation-curable ink), the associated coating or ink may be cured after each respective printing station. For example, without limitation, an embodiment of a process may include, at least in part: coating a base coat; a curing step; coating a secondary coating; and a curing step. Alternatively, also by way of example and without limitation, the process may comprise, at least in part: coating a base coat; a curing step; coating a base coat; a curing step; coating a secondary coating; and a curing step. Furthermore, for various embodiments of the present invention, it may be desirable to match or substantially match the production/subsequent processing rates of the containers/bottles to the flow/processing rates of the associated printing press.

Furthermore, it has been found that the quality of the printed image can be controlled and/or improved at least in part using one or more of the following techniques:

(a) selecting and/or calibrating an ink set (inkset);

(b) controlling the substrate (i.e., container surface) temperature; and/or

(c) And (5) controlling time.

With respect to selecting and/or calibrating an ink set, this may be accomplished, at least in part, by selecting and/or calibrating an ink that includes a primary coating and a secondary coating. It has been found that the inks used can be selected to provide desired time and/or temperature characteristics, including combinations with respect to each other. For example, selecting certain inks with a given viscosity may exhibit or provide certain desired temperature-related effects.

With respect to controlling the temperature of the substrate (i.e., the surface of the container), some measure may be taken to treat or control the temperature of the relevant portion of the sidewall (or other portion of the container). For example, a given portion of the container may be pretreated. Such pretreatment may be facilitated using a variety of known techniques, which may include, but are not limited to, flame treatment, corona treatment, and plasma treatment. However, the present invention is not limited to these specific pretreatment techniques.

With regard to time control, the time associated with the movement of the container, for example, by the production machine, and the application of the primary and/or secondary coating may be controlled. It may be desirable to match or substantially match the production/subsequent processing rate of the containers/bottles to the flow/processing rate of the associated printer.

The present invention may also include a system for evaluating or assessing the "acceptability," e.g., commercial acceptability, of containers having printed images such as digitally printed labels. That is, for various embodiments of the present invention, a system for evaluation or assessment may provide an "adhesion score. Fig. 2 generally represents a quality review table/matrix that may be used to assess or evaluate the acceptability of a printed image on a container. Generally as shown, the Y-axis may relate to numbers associated with passing or failing total points. In the embodiment shown, the numbers 1 to 5 indicate that the container is unacceptable, while the numbers 6 to 9 indicate that the relevant container is acceptable. It is important to note that while a score of at least 6 would be acceptable for a current table/matrix to "pass," the invention is not limited to the specific table/matrix shown, and further, the invention may provide more scores and/or increase or decrease the pass score as needed or desired. The plurality of tests are presented in a column disposed on the X-axis and may include a variety of standard tests, including those previously mentioned. For example, before no limitationUnder the circumstances, test 1 may include a "satherland friction test", test 2 may include a "3M #610 band test", test 3 may include a "simulated ship test", and test 4 may include a "3M #810 band test". Generally as indicated in the table, in connection with each of the tests, an individual pass or fail indication may be presented on the table. As for several of the above "standard" tests, the tests may be suitably modified for use in conjunction with printed images as opposed to labels applied in a conventional manner. For example, for various "tape" tests that may conform to the astm d3359-08 standard, the tests associated with the table/matrix may/may not involve cutting the image portion with a cutting tool prior to applying the pressure sensitive tape. That is, in one embodiment, "test 2" may relate to a "modified" 3M #610 strip test in the sense that the portion of the container image portion that is subjected to the test cannot be cross-cut or otherwise separated from the container. Further, in the table set forth in FIG. 2, the indication of "pass" for testing directly practicing the modified ASTM standard (i.e., testing that does not involve cross-cutting/separation) is generally by no greater than 2.0mm²Any removed portions of (a). For a tape test that directly practices ASTM standards, an indication of "pass" will generally be of the category "4B" or "5B" (classified according to ASTM fig. 1 for adhesion test results), or will involve removal of less than 5% of the printed area.

In one embodiment, it is desirable to provide a container having a printed image (e.g., a digital printed image) that is at least to be tested by the modified 3M #610 tape, but is still "recyclable". If less than the "4B" category is reached (i.e., 5% or more of the area is removed) with the ASTM D3359 Standard #810 tape test, then the digital image printed on the container is considered "recyclable". If the printed image of the container passed test 2 (modified 3M #610 tape test) and test 3 (simulated boat test), but did not pass test 4 (3M #810 tape test), the container would achieve an adhesion score of 6.0 or 7.0. Commercially, such containers with printed images having an adhesion score of 6.0 or 7.0 are suitable for shipping (i.e., passed a simulated shipping test) while providing adhesion associated with the printed image that is sufficient for normal/intended use, but yet separates smoothly for subsequent recycling. In other words, the adhesion forces associated with the configured digital image are sufficiently strong for the intended use, but do not interfere with separation during recycling.

With such tables/matrices, each test may be performed by sampling the container appropriately (e.g., statistically significant or representative). After all tests are completed, the results can be tabulated and entered into a table/matrix to provide an "adhesion" score. Subsequently, the relevance score results may be correlated.

In addition, the teachings of the present invention can improve recyclability. Recycling ink printed on various articles in an efficient manner can provide many cost and efficiency benefits, as well as being environmentally friendly. For example, without limitation, the present invention may facilitate removal of containers having digitally printed images (which may be formed from cured UV ink or radiation cured ink) that are at least partially composed of ink compositions that include hydrophilic and/or acidic components, as opposed to conventional plastic recycling processes. Traditionally, industry standard recycling processes for plastic containers include: grinding the containers into granular plastic flakes, subjecting the flakes to a high hot caustic wash process, drying off the washed flakes, sorting, and extruding into resin pellets for resale. In embodiments embodying aspects of the disclosed teachings, a digital image on the container may be left on the resin sheet after the grinding process, which is then separated from the resin sheet during a high thermal caustic wash process, which may be agitated, so as not to contaminate the clean resin sheet from which the resin pellets are to be formed.

By separation techniques, at least four methods may be used, alone or in various combinations, to break the polar and/or mechanical bonds to facilitate removal of the ink from the article. The techniques include those that use: (1) water-based or liquid-based solutions (e.g., for additives with hydrophilic components); (2) basic components (e.g., for additives with acidic components), i.e., chemical reactions can be used to release polar bonds; (3) heat or temperature; and/or (4) mechanical forces (e.g., high pressure jetting (psi)).

The present invention contemplates a variety of recycling processes that can be used to remove ink from an article. For example, one embodiment of a method for recycling plastic articles comprises: providing a plastic container having a digital image, the ink composition including a removal-promoting additive (e.g., a hydrophilic component or an acidic component); and exposing the digital image to a high temperature liquid-based solution (e.g., water with or without an alkaline component); optionally agitating the solution. The container may be subjected to a grinding operation before or after exposure. It can be said that a similar embodiment follows the following method: dry milling, elutriation, rinsing, drying and elutriation.

It can be said that another process, more like traditional industrial recovery and commercial (e.g., available from sorema (italy)) involves single washing, wet grinding, centrifugation, classification, and flotation tank/separation. For example, a "single rinse" may be performed by passing the bottle (e.g., by a fixed screw or multi-screw system) through a high pressure wash (e.g., a high temperature caustic wash). This may add a mechanical force component to aid in label removal. Typically, the bottles are intact, that is, not ground prior to such rinsing. The material comprising the polymeric ink may be washed away and fall into a collection or grid system below the conveyor mechanism.

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 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 enable one 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 following claims and their equivalents.

Claims (22)

1. A recyclable plastic container, comprising:

an outer surface having an image printed directly thereon, the image comprising cured ink droplets, and the ink droplets comprising a composition comprising a release-promoting additive;

wherein the ablation promoting additive causes the solidified ink droplets to separate from, or to release from, the outer surface of the container when the image is exposed to a liquid-based solution at an elevated temperature of at least 85 ℃;

wherein the image is configured to pass a modified 3M #610 tape test and a simulated watercraft test and not pass a 3M #810 tape test to show that the image has an adhesion score of 6.0 or 7.0;

wherein the modified 3M #610 strip test does not involve cross-cutting or separation of images.

2. The plastic container of claim 1, wherein the container comprises a plastic bottle.

3. The plastic container of claim 1, wherein the removal-promoting additive comprises a hydrophilic component.

4. The plastic container of claim 1, wherein the removal-promoting additive comprises an acidic component.

5. The plastic container of claim 4, wherein the acidic component comprises an acidic acrylate oligomer.

6. The plastic container of claim 4, wherein the acidic component comprises a monofunctional acid ester.

7. The plastic container of claim 4, wherein the acidic component comprises an acidic acrylate oligomer and a monofunctional acid ester.

8. The plastic container of claim 4, wherein the acidic component comprises at least 10% of the total composition of the ink droplets.

9. The plastic container of claim 1, wherein at least two ablation-promoting additives are present in the ink droplets.

10. The plastic container of claim 9, wherein one removal-promoting additive includes a hydrophilic component and the other removal-promoting additive includes an acidic component.

11. The plastic container of claim 1, wherein the image comprises:

a primer layer comprising a plurality of cured primer layer ink droplets, and

a secondary coating comprising a plurality of cured secondary coating ink droplets, the secondary coating applied to at least a portion of the primary coating.

12. The plastic container of claim 11, wherein the base coat comprises a white or colorless portion.

13. The plastic container of claim 1, wherein the container is comprised of one or more of the following materials: polyethylene, polyethylene terephthalate, and polypropylene.

14. The plastic container of claim 13, wherein the polyethylene is high density polyethylene.

15. A method for removing cured ink from a plastic container, the method comprising:

providing a plastic container having an image printed directly on an outer surface thereof, the image comprising cured ink droplets, and the ink droplets comprising a composition comprising a release-promoting additive, wherein the image is configured to pass a modified 3M #610 tape test and a simulated marine test, and to fail a 3M #810 tape test to indicate that the image has an adhesion score of 6.0 or 7.0;

wherein the modified 3M #610 strip test does not involve cross-cutting or separation of images;

exposing at least a portion of the image of the plastic container to a liquid-based solution at an elevated temperature, wherein the elevated temperature is a minimum of 85 ℃; and

removing at least a portion of the image from the outer surface on which the image is printed.

16. The method of claim 15, wherein the removal-promoting additive comprises a hydrophilic component.

17. The method of claim 15, wherein the removal-promoting additive comprises an acidic component.

18. The method of claim 15, wherein the elevated temperature is predetermined.

19. The method of claim 15, comprising scraping or wiping ink from the container after exposing the image to the liquid-based solution.

20. The method of claim 15, wherein the ink is mechanically removed in the form of a flake or film.

21. The method of claim 15, wherein the plastic container comprises a plastic bottle.

22. The method of claim 15, wherein the liquid-based solution has a pH of at least 9.0.