JP2018529007A - Method and composition for direct printing with improved recyclability - Google Patents

Abstract

The present disclosure relates to an ink composition for digital printing on the outer surface of a plastic article. The ink composition includes an ink removal promoting additive. In some aspects, the ink removal promoting additive can facilitate separation or release of the image from the outer surface of the article when the image is exposed to a liquid-based solution at an elevated temperature. Also disclosed is a recyclable plastic article having an image printed outer surface using the disclosed ink composition and a method of removing cured ink from a plastic container. This summary is intended as a scanning tool for searching a particular technical field and is not intended to limit the present invention. [Selection] Figure 1

Description

CROSS REFERENCE TO RELATED APPLICATIONS This application claims priority to US patent application Ser. No. 14 / 846,032, filed on Sep. 4, 2015, which is a U.S. application filed on Oct. 30, 2014. No. 14 / 528,324, which is a continuation-in-part of U.S. patent application Ser. No. 13 / 168,181, filed Jun. 24, 2011 S. Issued as 8,876,979, which claims priority from US Provisional Patent Application No. 61 / 360,512, filed July 1, 2010, and further filed on October 20, 2009. Claiming priority from US Provisional Patent Application No. 61 / 106,860, filed Oct. 20, 2008, which is a continuation-in-part of US patent application Ser. All of which are hereby incorporated by reference as if fully set forth herein.

TECHNICAL FIELD The present invention relates generally to ink compositions for digital printing on the outer surface of plastic articles. The invention also relates to plastic articles printed with digital images, including plastic containers having digital images with improved adhesion and / or recycling properties, and methods for facilitating their recycling.

  The plastic container industry will continue to use increasing recycling volumes. Container manufacturers have recently begun manufacturing containers with digitally printed labels of sufficient image quality and quality to compete with and potentially replace previous prior labeling techniques. Examples of such printing techniques are described in commonly owned US Pat. No. 7,625,059 and US Pat. No. 7,736,713, which are hereby incorporated by reference.

  A potential challenge arises when introducing containers with digitally printed labels into conventional container recycling processes. Some issues are mentioned and discussed in US patent application Ser. No. 12 / 581,952, which is also incorporated herein by reference in its entirety. There is a clear trend between container manufacturers, brand owners, end users, and municipalities to improve and increase plastic container recycling efforts. Accordingly, it is desirable to provide an industry acceptable product that is well compatible with current recycling infrastructure and processes, or that provides sufficient incentives and / or quantities to achieve industry-wide changes. At least initially, it would be desirable to provide recyclable digitally printed articles using current industry standard processes, i.e. processes that generally include caustic hot cleaning and grinding. As such, there is a need for a digitally printed plastic article, such as a container, that adheres to the article without quality issues over its lifetime but has a digital image that can be more easily removed during the plastic recycling process. is there.

  In an exemplary embodiment, an ink composition for digital printing on a plastic article is disclosed. Ink compositions generally include a base ink; an ink removal promoting additive; and a carrier capable of dissolving at least a portion of the ink removal promoting additive. The removal-enhancing additive plasticizes at least some of the ink-cured droplets when the printed digital image is exposed to a liquid-based (eg, water-based) solution at or near a predetermined high temperature. Configured or selected to separate or release from the outer surface of the article. Such a predetermined high temperature may include, but is not limited to, that associated with a conventional recycling process.

  In another aspect, a recyclable plastic article is disclosed having an outer surface with a digital image printed with cured droplets of ink. The ink droplets comprise an ink composition as summarized above, which includes a removal enhancing additive. Also disclosed are method embodiments for removing the ink from plastic containers and methods for facilitating such recycling.

  Additional advantages of the invention will be set forth in part in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. It should be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention as claimed.

  Embodiments of the present invention will now be described by way of example with reference to the accompanying drawings.

In general, a side view of a portion of a plastic container with a digital image of an embodiment printed thereon is illustrated. A general notation of a quality review table / matrix that can be used to assess the acceptability of printed images into plastic articles.

  In various aspects, reference will now be made in detail to embodiments of the 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.

  In a general but non-limiting situation, a portion of the surface 10 of a plastic article (eg, container) having an embodiment of the printed image 20 is generally illustrated in FIG. The illustrated embodiment of the image 20 includes a base coat 30 that can consist of a plurality of base coat ink droplets 32 and can also include a secondary coat 40 that can consist of a plurality of secondary coat ink droplets 42.

  Containers (including bottles) associated with the present disclosure may be plastic materials or resins (eg, acrylonitrile-butadiene-styrene (ABS), polyethylene terephthalate (PET), polystyrene (PS), polyethylene (PE) (high density polyethylene ( HDPE), polypropylene (PP), polyvinyl chloride (PVC), etc.). Further, the container may be a single layer or multilayer container and can be formed using a variety of conventional molding techniques including, but not limited to, injection molding, blow molding, thermoforming, and the like. In one embodiment, the outermost layer / surface may consist of unused plastic material. However, it is noted that containers according to the teachings of the present disclosure may also include a certain percentage of recycled content, including a percentage of recycled content in the outer layer of the container.

  In embodiments, an article (eg, a container) can include a first coat or base coat (eg, base coat 30 shown in FIG. 1). Basecoat 30 may consist of a plurality of basecoat ink droplets 32 that are printed on the outer surface of the article (e.g., digitally printed, such as by a drop-on-demand ink jet process), and subsequently cured or allowed to cure. . The ink may be a UV curable ink, which is curable by UV radiation that can be applied by various known means including, but not limited to, UV or LED lamps. The ink droplets may be monomer based and help improve ink droplet application (eg, provide good process properties for printing) and / or visual properties (eg, color or texture) ). In embodiments, the base coat 30 may include white and / or colorless portions. Further, for the disclosed ink droplets, ie monomer-based, curing can cause the ink droplets to polymerize. Since the ink used is not solvent based, the ink can be configured so that the ink does not flow into the solution and does not emit volatiles during the recycling process, like a solvent. Note that the US Environmental Protection Agency (EPA) has published guidelines on solvents, but the polymer is solid and does not flash off or release volatile materials. That is, separation of ink as disclosed herein is included as part of chemical dissolution, as the ink is in a cured polymer state and can be physically removed (eg, in the form of flakes or films). Rather, it may be mechanical in nature.

  As summarized above, the ink composition comprising the ink droplets includes a removal promoting additive. In some aspects, the “removal promoting additive” includes at least one hydrophilic or acidic component. The hydrophilic component may include one or more composition elements that exhibit hydrophilicity (water-like properties). The acidic component may include one or more composition elements that exhibit acidity. In some embodiments, the removal promoting additive will comprise a combination of hydrophilic and acidic components, ie, at least two removal promoting additives. Some ink droplet compositions, “binary” compositions, where the removal-promoting additive contains both hydrophilic and acidic components, give results equivalent to using a composition containing only one additive. A smaller percentage of weight (relative to the total) may be used to provide.

  Such hydrophilic components may include hydrophilic monomers, hydrophilic oligomers, and water dispersible monomers that provide the desired functionality. Hydrophilic monomers are often characterized as having an oxygen or nitrogen atom in addition to the halogen in the backbone structure. Such monomers are generally susceptible to attack by polar solvents such as water and ketones. Hydrophilic monomers also tend to be less resistant to thermal degradation. Thus, when one or more hydrophilic components are included in the associated ink droplet, the image (ie, the cured ink droplet) is removed from the plastic structure of the article at a later time (eg, after recycling after use). Separation can be improved. By way of example and not limitation, in the cured state, the hydrophilic portion of the polymer will normally absorb water. When this happens, water can act as a plasticizer to increase the mobility of the polymer chain. The increased mobility can soften the polymer and make it more susceptible to removal. As such, a plastic article, such as a container containing an image composed of an ink composition containing a removal promoting additive (eg, a hydrophilic monomer), at a high temperature in a liquid based solution (eg, agitated water). Exposure will promote softening of the ink composition (ie, hydrophilic monomer) and separation of the image from the plastic material. The elevated temperature can be predetermined and can be a temperature that the article generally exceeds the temperature found in normal use. Furthermore, to the desired extent, the adhesion separation threshold is such that softening and subsequent removal occurs only at substantially high temperatures (eg, during the recycling process) and is substantially prevented during normal intended use. It may be set as follows. Note that aliphatic urethane acrylates are a common class of hydrophilic monomers that generally absorb water and can potentially be used as hydrophilic components. In addition, some hydrophilic oligomers may also be used as the hydrophilic component if they are of a suitable viscosity for ink jet / digital printing applications (ie not too high).

  Without limitation, in some embodiments, the removal promoting additive has a percent weight in the range of approximately 0% to 20% by weight relative to the total weight (ie, relative to the associated ink and removal promoting additive). Certain hydrophilic monomers may be included. In some embodiments, the percent weight of the removal promoting additive will fall within the range of approximately 0-10% of the total weight. A non-limiting example of a hydrophilic monomer that can be used is methoxy polyethylene glycol monoacrylate (eg, CD553 marketed by Sartomer USA, LLC (Sartomer)).

  Note that some water-dispersible monomers are also hydrophilic and appear to absorb water upon curing. In such a composition, water can act as a plasticizer to soften the cured ink composition (eg, the cured ink film on the surface of the container) and facilitate removal of the ink film during the recycling process. In embodiments of the present disclosure, when a suitable hydrophilic component is included in the ink composition, it imparts hydrophilicity to the ink while maintaining the jet ability and adhesion of the ink to the article substrate over the useful life of the article. be able to.

  The acidic component includes an acidic monomer having a measurable acidic value. Note that the measurable amount can be based on pH, acid weight percentage, or titration of alkaline chemicals (eg, mg KOH / g [milligrams of potassium hydroxide per gram of monomer]). Further, for example, in the cured state, the acidic portion of the polymer may be vulnerable to caustic solutions. The reaction between the acidic functionality of the polymer chain and the alkalinity of the solution can result in a decrease in adhesion to the applied substrate and promote polymer separation. Non-limiting examples of acidic monomers that can be used include acidic acrylate oligomers (eg, CN147 commercialized by Sartomer) and monofunctional acid esters (eg, CD9050 commercialized by Sartomer). ). For example, when a container containing an acidic component comes into contact with a cleaning fluid (eg, a conventional caustic cleaning fluid), the associated bond is broken to facilitate the intended separation of the printed image (ink droplets) from the plastic substrate. Can do.

  In other embodiments, the removal promoting additive is configured or otherwise selected according to desired properties that can facilitate removal of the cured ink composition from the surface of the plastic article. For example, in one aspect, it is desirable for the removal promoting additive to exhibit relatively high solvent solubility and relatively high water solubility in combination with a glass transition temperature that is lower than that typically used in conventional recycling processes. . For this purpose, according to an exemplary embodiment, the removal promoting additive exhibits a glass transition temperature (Tg) of less than about 130 ° C. This is a glass transition temperature that is less than about 120 ° C, less than about 110 ° C, less than about 100 ° C, less than about 90 ° C, less than about 80 ° C, less than about 70 ° C, less than about 60 ° C, or even less than about 50 ° C ( A removal promoting additive exhibiting Tg) may be included. In a further aspect, the ink removal promoting additive has a glass transition temperature (Tg) in the range of about 50C to about 130C. In yet another aspect, the ink removal promoting additive has a glass transition temperature (Tg) in the range of about 55 ° C to about 125 ° C, or about 65 ° C to about 105 ° C, or about 55 ° C to about 95 ° C. In yet another aspect, the ink removal promoting additive may have any range of glass transition temperature (Tg) derived from any of the above exemplary values.

  As those skilled in the art will appreciate, the desired level of water solubility can be characterized, for example, as a function of the acid number of the removal promoting additive. The acid number can be expressed as a titration value of an alkaline chemical (eg, mg KOH / g [milligrams of potassium hydroxide per gram of removal promoting additive]). In these embodiments, the removal enhancing additive is 110 mg KOH / gram, 120 mg KOH / gram, 130 mg KOH / gram, 140 mg KOH / gram, 150 mg KOH / gram, 160 mg KOH / gram, 170 mg KOH / gram, 180 mg KOH / gram. , 190 mg KOH / gram, 200 mg KOH / gram, 210 mg KOH / gram, 220 mg KOH / gram, 230 mg KOH / gram, and 240 mg KOH / gram, in the range of about 100 mg KOH / gram to about 250 mg KOH / gram May show acid value. In a further aspect, the ink removal promoting additive has an acid number in the range of about 150 mg KOH / gram, about 205 mg KOH / gram, including values of 175 mg KOH / gram, 185 mg KOH / gram, and 195 mg KOH / gram. In yet another aspect, the ink removal promoting additive can have any range of acid numbers derived from any of the above exemplary values.

  In a further aspect, the removal promoting additive can exhibit a glass transition temperature (Tg) of less than about 100 ° C. and an acid number ranging from about 100 mg KOH / gram to about 250 mg KOH / gram. In yet another aspect, the ink removal promoting additive exhibits a glass transition temperature (Tg) in the range of about 50 ° C. to about 90 ° C. and an acid number in the range of about 150 mg KOH / gram to about 205 mg KOH / gram. it can. In yet another aspect, the ink removal promoting additive can have any range of acid values derived from the glass transition temperature (Tg) and any of the exemplary values described above.

  By selecting removal-promoting additives that exhibit the desired combination of water solubility and glass transition temperature, the desired adhesion, scratch resistance, and solvent resistance are also facilitated while facilitating the ink removal process as a precursor to the recycling process. It is possible to provide a curable ink exhibiting When exposed to a caustic environment at temperatures above the Tg of the removal-promoting additive, the additive's softening can be this, resulting in a relatively clean release of the cured ink layer from the printed plastic surface. There is.

  These removal promoting additives can be present in the ink composition in an amount of from about 1 to about 20 weight percent of the ink composition. This is a specific exemplified amount of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, and 19 weight percent. Further can be included. In a further aspect, the ink removal promoting additive can be present in any range of amounts derived from any of the above exemplary values. For example, the removal promoting additive can be present in the ink composition in an amount of from about 5 to about 20 weight percent of the ink composition.

  In an exemplary embodiment, the ink removal promoting additive exhibiting the above combination of water solubility and relatively low glass transition temperature comprises a styrene maleic anhydride resin. In a further aspect, the styrene maleic anhydride resin can be a copolymer of a styrene maleic anhydride copolymer. In yet another aspect, the styrene maleic anhydride is esterified styrene maleic anhydride. Exemplary non-limiting commercially available styrene maleic anhydride resins suitable for use as removal promoting additives are Cray Valley SMA® 3840 and SMA® 1440F resins from Total.

  In a further aspect, the ink composition comprising the ink droplets also includes a carrier capable of solubilizing and dissolving at least a portion of the ink removal promoting additive. The carrier can be monomer-based or solvent-based. Exemplary monomers that can be used as carriers include a class of acrylic monomers. In exemplary embodiments, suitable acrylic monomers include 1,3-butylene glycol diacrylate, 1,6-hexanediol diacrylate, 1,3-butylene glycol dimethacrylate, isobornyl acrylate, or Mention may be made of isodecyl methacrylate, or a combination thereof. In some embodiments, the acrylic monomer is selected from 1,3-butylene glycol diacrylate, 1,6-hexanediol diacrylate, and 1,3-butylene glycol dimethacrylate. As described above, in embodiments, the carrier that can solubilize the removal promoting additive can be solvent-based. A suitable solvent can be an aprotic solvent or an aqueous solvent in some embodiments. Specific, non-limiting examples of suitable solvent carriers include N-methyl-2-pyrrolidone (NMP) and acetone.

  The carrier component can be present in the ink composition in an amount from about 1 to about 20 weight percent of the ink composition. This is a specific exemplified amount of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, and 19 weight percent. Further can be included. In a further aspect, the carrier can be present in any range of amounts derived from any of the above exemplary values. For example, the carrier can be present in the ink composition in an amount from about 5 to about 15 weight percent of the ink composition.

  The base ink portion of the ink composition can be any conventionally known curable ink, such as a conventional UV curable ink. The base ink is 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, In amounts ranging from about 50 to about 85 weight percent of the ink composition, including exemplary weight percent values of 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, and 84 weight percent. It can be present in the ink composition. In a further aspect, the base ink can be present in any range of amounts derived from any of the above exemplary values. For example, the base ink can be present in the ink composition in an amount of about 65 to about 85 weight percent of the ink composition.

  In one exemplary embodiment, (a) about 65 to about 85 weight percent base ink; (b) about 5 to about 20 weight percent ink removal promoting additive having a glass transition temperature less than about 100 ° C .; Disclosed herein is an ink composition comprising: c) about 5 to about 15 weight percent carrier capable of dissolving at least a portion of the ink removal promoting additive. According to this exemplary embodiment, the base ink can be a base UV white ink, the ink removal promoting additive can be a styrene maleic anhydride resin, and the carrier can be solvent based. N-methyl-2-pyrrolidone (NMP), or acetone, or other acceptable solvents.

  As described herein, a recyclable plastic article comprising a digitally printed image printed directly on a curved outer surface is disclosed, wherein the image is a cured droplet of an ink composition as described herein above. including. In a further aspect, an exemplary recyclable plastic article includes a curved outer surface with a digitally printed image printed directly on the curved outer surface, an image containing cured droplets of ink, and an ink removal having a glass transition temperature of less than about 100 degrees Celsius. Ink droplets comprising a composition comprising an accelerating additive. In yet another aspect, the digitally printed image has an adhesion score of at least 6.0 and up to 9.0, and the removal promoting additive is exposed to the basic solution at an elevated temperature of at least about 70 ° C. When the ink droplets are separated or released from the curved outer surface of the article.

  In a further aspect, the article includes a plastic container. In a further aspect, the plastic container is a bottle. In yet another aspect, the plastic container is composed of one or more of the following materials: polyethylene, polyethylene terephthalate, high density polyethylene, and polypropylene.

  In a further aspect, the removal facilitating additive present in the ink composition cures the ink when the digitally printed image is exposed to a liquid based solution, such as an aqueous or water based solution, at a predetermined elevated temperature. The droplet is configured to be separated or released from the curved outer surface of the article. For example, a cured droplet of ink can be applied to the curved outer surface of an article when the digitally printed image is exposed to a basic solution having a pH of at least about 10, 11, 12, or 13 at an elevated temperature in the range of about 70-90 ° C. Can be separated or released from. In a further aspect, the basic solution has a pH in the range of about 12-13. According to an aspect, after exposure to a basic solution at an elevated temperature for a sufficient period of time, at least about 90 weight percent of the cured ink droplets separate from the curved outer surface of the article. In yet another aspect, the digitally printed image includes a basecoat that includes a plurality of cured basecoat ink droplets, and a secondary coat that includes a plurality of cured secondarycoat ink droplets, wherein the secondary coat is at least a portion of the basecoat. To be applied.

  By way of example and not limitation, an embodiment of a polyethylene terephthalate (PET) container comprising a UV curable printing ink with a blended removal promoting additive has been subjected to an ink removal test. The blended removal-promoting additive of the tested containers contained acidic monomers of the type described above, i.e., acidic acrylate oligomers and / or monofunctional acid esters. The container may be subjected to a bath solution containing a pH level of at least 9.0, which may aid in label removal as is generally known in the plastic container recycling field, where the solution is heated to about 85 ° C. Good. Various samples were exposed to such conditions for 12 minutes and evaluated on a scale of 0-5 as follows.

  0-no removal improvement compared to control sample

  1—Minimum improvement was observed, removal was only obtained in some areas by abrasion with metal objects.

  2- Some improvement was observed, and the entire film could be removed by scraping with a metal object.

  The 3-cured ink film could be removed by scraping with a nail.

  The 4-cured ink film could be easily removed by simply wiping with a clean wipe.

  The 5-cured ink film peeled off during the cleaning test.

  The test identified, among other things, solutions that exhibited a removal performance level of 4 or 5. However, a level of at least 4 is not necessary, and in some applications a lower removal level may be acceptable. The results of the tests showed that inclusion of blended removal promoting (acidic) additives in the ink composition resulted in a significant improvement in the removal of cured ink from plastic (PET) material. Both forms of acidic additives show an improvement in promoting ink removal, and in this test configuration, a slightly lower composition percentage of acidic acrylic acid as opposed to monofunctional acid esters (10% vs. 15%, respectively). Lat oligomers were used to obtain removal levels of at least level 4.

  In embodiments, the ink composition may optionally include a hydrophobic component. That is, the ink composition may include, for example, a hydrophilic component and a hydrophobic component. The hydrophobic component may include a hydrophobic (water hate) monomer. Hydrophobicity is generally related to polarity. Many hydrophobic monomers are characterized as having an organic backbone structure consisting primarily of hydrogen and carbon; thus, such monomers tend to be non-polar and polar solvents (eg, water and alcohols) As well as resistance to acids and bases. In such a two component embodiment, the ink composition should balance between a hydrophilic component and a hydrophobic component (eg, a hydrophilic monomer and a hydrophobic monomer). Hydrophobic monomers can help keep the ink drops from adhering to the article substrate. Hydrophilic monomers can help soften (and further separate) when the image is exposed to a recycling process / bath (eg, water stirred at an elevated temperature).

In imaged container embodiments, at least a first basecoat 30 (which may include a hydrophilic component) may be applied to the surface of the container at an initial time t ₁ and an initial temperature T ₁ . Temperatures T ₁ would be in the range of temperature suitable for the application of the relevant base coat. In one embodiment, the base coat 30 may be curable (eg, ultraviolet (UV) curable) and may be cured prior to application of the secondary coat.

  In some embodiments, the secondary coat 40 may comprise a plurality of secondary coat ink droplets 42 distributed over at least a portion of the base coat 30. Furthermore, if desired, additional layers of “secondary” coats (eg, tertiary layers, etc.) may also be applied to the secondary coat 40. In an embodiment of the present disclosure, the secondary coated ink droplet 42 may also consist of an ink composition that includes a hydrophilic component.

The plurality of secondary coat ink droplets 42 may collectively form portions of the coating pattern, and the coating pattern may then form all or part of the image. Further, as generally illustrated in FIG. 1, some of the one or more adjacent secondary coat ink droplets 42 may overlap or intermix with each other. The secondary coat 40 and secondary coat ink droplets 42 of the configuration may include various known colors including, but not limited to, primary print colors such as cyan, magenta, and yellow. Furthermore, additional “process” colors can be provided by controlling the overlap or combination of specific colors in specific areas. Further, the secondary coat ink droplet 42 may be curable. For example, the UV curable secondary coat ink droplet may include all or part of the intended image. If curing is achieved by radiation, the ink composition may include a photoinitiator. In addition, the cured ink on the container surface is a machine that results from two bonds-a polar bond between the ink polymer and the plastic, and a plastic surface that has a non-uniform surface at a microscopic level (eg, microstructure). Note that it can be mainly retained by the mechanical coupling. In many embodiments of the present disclosure, it is best to attack both combinations. In some applications, the hydrophilic component can work better on mechanical bonds, while the acidic component can work better on polar bonds. Depending on the application, the secondary coated ink droplets can vary in diameter, which can range, for example, from about 10 microns to about 200 microns. Secondary coating 40, at the second time t ₂ and the second temperature T _2, may be applied to the surface 10 of the container, the second temperature T ₂ is typically the secondary coating 40 is applied, the base coat the first is lower than the temperature T ₁ of the 30 is applied.

In embodiments of the present invention, the time between application of the base coat and application of the secondary coat (eg, t ₂ minus t ₁ ) can be reduced to, for example, only 10 seconds or less. In some embodiments, the application time difference will be within 2-6 seconds. Further, in an embodiment, the application temperature difference between the temperature at which the base coat 30 is applied and the temperature at which the secondary coat 40 is applied to a portion of the base coat 30, ie, T ₁ minus T ₂ is about 10 ° F. It can be controlled to be: In some embodiments, the application temperature difference will be within about 5 ° F to about 10 ° F. Further, in some applications, associated with the application of the base coat 30 and the secondary coat 40 such that the respective application temperatures approach each other—ie, the temperature difference between the applied coats is reduced or minimized. It may be desirable to correct the temperature. This, for example, can be achieved by a combination of reduction / decrease in _{(a) T 1, (b} ) T 2 increase / increases, or (c) (a) and (b). Such a time and / or temperature control as described above for the base coat and secondary coat can provide better adhesion of the printed image to the article.

Note that in addition to time and temperature, irradiance is a factor that can also affect the effective cure rate of the printed image. That is, at a particular time (eg, t ₁ and t ₂ ) and temperature (eg, T ₁ and T ₂ ), there can be associated irradiance, ie _, ε ₁ and ε ₂ . For example, in embodiments, the base coat may be cured with an irradiance ε ₁ and the associated secondary coat may be cured with an irradiance ε ₂ . Further, in embodiments, the effective cure rate may be based on a combination of time, temperature, and irradiance, which is generally expressed by the following formula:
Irradiance (ε) = (dΦ / dA)
(Where Φ = irradiation flux (measured in watts) and A = area (cm ² )).

For example, but not by way of limitation, the range of irradiance for some embodiments will be between about 0.1 watts / cm ² and about 10.0 watts / cm ² .

  For example, in some applications where a curable ink is used (eg, UV curable or radiation curable ink), the associated coat or ink may be cured after each printing station. For example, without limitation, process embodiments may include, at least in part, applying a base coat; curing step; applying a secondary coat; and curing step. Alternatively, by way of example and not limitation, the process may include, at least in part, a base coat application; a curing step; a base coat application; a curing step; a secondary coat application; and a curing step.

  Further, in embodiments of the present invention, it may be desirable that the container / bottle manufacturing / subsequent handling speed match or substantially match the flow / process speed of the associated printing machine (s).

Furthermore, it has been found that the quality of the printed image can be controlled and / or improved at least in part by one or more of the following techniques.
(A) Ink set selection and / or calibration;
(B) control of substrate (ie, container surface) temperature; and / or (c) timing control.

  With respect to ink set selection and / or calibration, this is accomplished, at least in part, by ink selection and / or calibration including a base and secondary coat. It has been discovered that the ink used can be selected to provide the desired time and / or temperature characteristics, including those associated with each other. For example, the selection of a particular ink having a given viscosity can indicate or provide a particular desired temperature related effect.

  With regard to controlling the substrate (ie, container surface) temperature, the temperature of the relevant part of the sidewall (or other part of the container) can be treated or controlled to a certain degree. For example, a given portion of the container can be pretreated. Such pretreatment can be facilitated using various known techniques that can include, but are not limited to, flame, corona, and plasma treatment. However, the present invention is not limited to these specific pretreatment techniques.

  With respect to timing control, it is possible to control, for example, the time associated with the movement of the container through the manufacturing machine, and the timing of application of the base coat and / or secondary coat. It may be desirable for the container / bottle manufacturing / subsequent handling speed to match or substantially match the flow / process speed of the associated printing machine (s).

The present disclosure may also include a system for assessing or assessing “acceptability”, such as the commercial acceptability of a container having a printed image, such as a digital printed label. That is, in an embodiment of the present invention, a system for assessing or evaluating can provide an “adhesion score”. FIG. 2 generally represents a quality review table / matrix that can be used to assess or assess the acceptability of a printed image into a container. As generally indicated, the Y-axis may include numbers associated with the overall pass or fail score. In the illustrated embodiment, numbers 1-5 indicate that the container is not receptive, while numbers 6-9 indicate that the associated container is receptive. At least 6 will be “passed” as acceptable for the table / matrix, but the invention is not limited to the specific table / matrix shown, or a higher score is provided. It is important to note that and / or the passing score could have increased or decreased as desired or necessary. Tests that may include various standard tests, including those described above, are represented in the column provided on the X axis. For example, without limitation, Test 1 may include a “Superland Friction Test”, Test 2 may include a “3M # 610 Tape Test”, and Test 3 may be a “Simulated Ship Test”. Test 4 may include a “3M # 810 tape test”. As generally shown in the table, various pass or fail notations can be represented in the table in conjunction with each listed test. For some of the “standard” tests described above, the tests may be modified to be suitable for use in connection with printed images as opposed to conventionally applied labels. For example, in various “tape” tests that may follow the ASTM D 3359-08 standard, the test associated with the table / matrix may also include cutting the image portion with a cutting tool prior to applying the adhesive tape. It does not have to be. That is, in one embodiment, “Test 2” is a “modified” 3M # 610 tape test unless a portion of the image portion of the container subjected to the test is cross-cut or otherwise separated from the container. May be included. In addition, in the table described in FIG. 2, the “pass” indication for tape tests that directly implement the modified ASTM standard (ie, tests without cross-cut / separation) is generally removed arbitrarily below 2.0 mm ^2. It will be represented by a part. For tape tests that directly implement the ASTM standard, the “pass” indication is generally classified as “4B” or “5B” (according to the ASTM standard, the classification of the adhesion test results in FIG. 1), or of the printed area that has been removed. It will contain less than 5%.

  In one embodiment, it is desirable to provide a container that, at a minimum, passes a modified 3M # 610 tape test and nevertheless has a printed image (eg, a digitally printed image) that is “recyclable”. A digital image printed on a container is considered “recyclable” if it achieves a “4B” classification (ie, more than 5% of the area is removed) using the ASTM D 3359 standard # 810 tape test. It is done. Containers with digital images that pass Test 2 (Modified 3M # 610 Tape Test) and Test 3 (Simulation Shipment Test) and fail Test 4 (3M # 810 Tape Test) are 6.0 or 7. Any adhesion score of 0 will be achieved. Such a container with a printed image having an adhesion score of 6.0 or 7.0 is sufficient for normal / intended use but is preferably separable for subsequent recycling It is commercially suitable for shipping (ie, passing a mock shipping test) while providing the adhesion associated with the. In other words, the adhesive force associated with the constructed digital image is strong enough for the intended use, but does not prevent separation during recycling.

  For such a table / matrix, each test may be performed at an appropriate (eg, statistically significant or representative) sampling of the container. After all tests are complete, the results may be tabulated and tabulated to provide an “adhesion” score. The related score results can then be correlated.

  Among other things, the teachings of the present disclosure can provide improved recyclability. Recycling ink printed on various articles in an effective manner can provide many cost and efficiency benefits in addition to providing benefits to the environment. For example, but not limited to, a container having a digitally printed image (which may be formed from a cured UV ink or a radiation curable ink) consisting at least in part of an ink composition comprising a hydrophilic component and / or an acidic component. It can be conveniently removed in connection with conventional plastic recycling processes. The industry standard recycling process for plastic containers has traditionally been for grinding containers into granular plastic flakes, subjecting these flakes to a hot caustic cleaning process, drying the cleaned flakes, sorting, and resale. Extruding into resin pellets. In embodiments embodying aspects of the disclosed teachings, the digital image on the container may remain in the resin flake after the grinding process, and the digital image is substantially from the resin flake during the high heat caustic cleaning process that may be agitated. Will be separated, thereby not contaminating clean resin flakes to be formed into resin pellets.

  In separation techniques, there are at least four methodologies that can be used alone or in various combinations to attack polarity and / or mechanical coupling to facilitate removal of the ink from the article. This technique involves (1) a water or liquid based solution (eg, for an additive having a hydrophilic component or having a desired Tg and acid number as described herein); ) Caustic component (ie, for an acidic component or additive having a desired combination of Tg and acid number as described herein)-ie a chemical reaction is used to release the polar bond. Including: using (3) heat or temperature; and / or (4) mechanical force (eg, high pressure spray (psi)); or any combination thereof.

  The present disclosure envisions a number of recycling processes that can be used to remove ink from an article. For example, one embodiment of a method for recycling plastic containers includes providing a plastic container with a digital image, and the ink composition includes a removal promoting additive (eg, a hydrophilic or acidic component); One embodiment of the method further includes exposing the digital image to a liquid-based solution (eg, water with or without a caustic component) at an elevated temperature; optionally, stirring the solution. Before or after exposure, the container may be subjected to a grinding operation. Similar embodiments may be said to be along a line that includes dry grinding, cleaning, cleaning, drying, and cleaning.

  Another process that may be more similar to conventional industrial recycling and is commercially available (eg, SOREMA (Italy)) is said to include single wash, wet grinding, centrifugation, sorting, and float tank / separation. obtain. “Single wash” can be used, for example, by transporting the bottle (eg, by a set screw or multi-screw system) through high pressure wash (eg, caustic high temperature wash). This can add a mechanical force component to aid in label removal. Usually, the bottle as a whole is not crushed before it is washed. The material containing the polymerized ink can be washed away and fall into a collection or grating system under the transport mechanism.

  In a further aspect, the present disclosure provides a method for removing cured ink from a plastic container, the method comprising: (a) a curved outer surface in which a digital image is printed directly on the curved outer surface of a plastic container by a drop-on-demand ink jet printing process. An ink containing cured droplets of ink applied directly to the curved outer surface of the plastic container and having an adhesion score of at least 6.0 and up to about 9.0, and an ink removal enhancement having a glass transition temperature of less than about 100 ° C. Providing a plastic container having an ink droplet comprising a composition comprising an additive; (b) exposing at least a portion of the digitally printed image of the plastic container to a basic solution at an elevated temperature of at least about 70 ° C. And (c) at least part of the digitally printed image is a curved outer surface on which the image is printed. It is removed, including.

  In a further aspect, the plastic container is a bottle. In yet another aspect, the plastic container is composed of one or more of the following materials: polyethylene, polyethylene terephthalate, high density polyethylene, and polypropylene.

  In a further aspect, the ink removal promoting additive comprises a styrene maleic anhydride copolymer. In a further aspect, the ink removal promoting additive has a glass transition temperature (Tg) in the range of about 50C to about 130C. In yet another aspect, the ink removal promoting additive has a glass transition temperature (Tg) in the range of about 65 ° C to about 110 ° C. In yet another aspect, the ink removal promoting additive has a glass transition temperature (Tg) in the range of about 55 ° C to about 65 ° C. In yet another aspect, the ink removal promoting additive has an acid number ranging from about 150 mg KOH / gram to about 205 mg KOH / gram. In yet another aspect, the ink removal promoting additive has an acid number ranging from about 165 mg KOH / gram to about 205 mg KOH / gram.

  In a further aspect, the basic solution is an aqueous solution having a pH in the range of about 12-13 and the elevated temperature is in the range of about 70-90 ° C. In yet another aspect, the removing step includes scraping or wiping the ink from the container after exposure of the image to the basic solution. In yet another aspect, the ink is mechanically removed in the form of flakes or films.

  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 form disclosed, and various modifications and variations are possible in light of the above teachings. The embodiments illustrate the principles of the invention and its practical application so that one skilled in the art can utilize the invention and various embodiments with various modifications as appropriate for the particular use under consideration. Was selected and described to enable It is intended that the scope of the invention be defined by the appended claims and their equivalents.

A. Experimental The following examples provide those skilled in the art with a complete disclosure and description of how the compounds, compositions, articles, devices, and / or methods claimed herein are made and evaluated. And is purely exemplary and is not intended to limit the present disclosure. Efforts have been made to ensure accuracy with respect to numbers (eg, amounts, temperature, etc.) but some errors and deviations should be accounted for. Unless indicated otherwise, parts are parts by weight, temperature is in ° C., or is ambient temperature, and pressure is at or near atmospheric.

  In the following illustrative examples, various ink compositions according to the present disclosure were prepared and tested for use in direct printing on the outer surface of a plastic article. The ink composition can be prepared by first dissolving the ink removal promoting additive in a carrier and then adding the carrier solution to the base ink. The prepared ink composition can then be used to print directly on the outer surface of a plastic article.

  The performance and recyclability of various ink compositions on plastic articles was also evaluated. Ink compositions comprising UV curable inks with removal accelerating additives and carriers were printed directly on the surface of polyethylene terephthalate (PET), polyethylene (PE) and / or high density polyethylene (HDPE) samples and cured. .

  The cured ink of the sample was then subjected to an ink removal test that can include one or more of adhesion, scratch resistance, and solvent resistance tests. Samples include various bath solutions that can assist in label removal as is generally known in the art of plastic container recycling, eg, a pH level of at least 9.0 and the solution is heated to about 75 ° C. or 85 ° C. Can be applied to the bath solution. The test was conducted in a period including immediately after the treatment (immediately after) and 1 hour after the treatment (1 hour).

The compositions shown and evaluated herein were prepared using the materials shown in Table 1.

1. Example 1
In the following examples, the test sample removal facilitating additives were waxes and resins. The carrier was acetone or N-methyl-2-pyrrolidone (NMP) (commercially available from Sigma Aldrich). The ink formulations and performance data of the present invention are presented in Tables 2-5 below. In the following data, “pass” indicates that no ink removal was observed, and “fail” indicates that significant and / or complete ink removal was observed. Any% value listed corresponds to the observed% ink removal.

  As the data shows, the SMA 3840 and SMA 1440F ink formulation samples showed improved performance. The SMA 3840 ink formulation showed some signs of improvement. This shows improved ink removal when compared to the control. The SMA 1440F ink formulation did not demonstrate significant signs during normal use testing ("in use"), but demonstrated strong removal during the caustic cleaning test. The test was repeated several times with PET, EPET, and PE and all showed good removal in the caustic test.

2. Example 2
In this example, an ink composition comprising a white UV curable ink having a removal promoting additive and a carrier was printed and cured directly on the surface of polyethylene terephthalate (PET) and high density polyethylene (HDPE) samples. The sample removal enhancement additive tested was a styrene maleic anhydride copolymer (SMA 1440F, commercially available from Cray Valley USA, LLC) and the carrier was N-methyl-2-pyrrolidone (NMP, commercially available from Sigma Aldrich). Has been). Ink formulations and performance data are presented in Table 6 below.

  As the data indicate, nearly 100% removal of the ink composition of the present invention was observed compared to only 50-60% removal of the standard ink control. In the HDPE sample, the ink composition of the present invention showed greater than 50% ink removal compared to about 10% ink removal for the standard ink control. The results of the ink composition of the present invention meet the current recycling guidelines published by Association of Postconsumer Plastic Recyclers.

  It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the scope or spirit of the invention. Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the appended claims.

Claims (55)

An ink composition for digital printing on a plastic article,
(A) base ink;
(B) an ink removal promoting additive having a glass transition temperature of less than about 130 ° C .; and (c) the ink composition comprising a carrier capable of dissolving at least a portion of the ink removal promoting additive.   The ink composition of claim 1, wherein the ink removal promoting additive comprises a styrene maleic anhydride copolymer.   The ink composition of claim 1, wherein the ink removal promoting additive has a glass transition temperature (Tg) in the range of about 50C to about 110C.   The ink composition of claim 1, wherein the ink removal promoting additive has a glass transition temperature (Tg) in the range of about 55C to about 85C.   The ink composition of claim 1, wherein the ink removal promoting additive has a glass transition temperature (Tg) in the range of about 55C to about 65C.   The ink composition of claim 1, wherein the ink removal promoting additive has an acid number ranging from about 150 mg KOH / gram to about 205 mg KOH / gram.   The ink composition of claim 1, wherein the ink removal promoting additive has an acid number ranging from about 165 mg KOH / gram to about 205 mg KOH / gram.   The ink composition according to claim 1, wherein the carrier comprises a solvent, a monomer, or a combination thereof.   The ink composition according to claim 8, wherein the solvent comprises at least one aprotic solvent.   The ink composition according to claim 8, wherein the solvent comprises N-methyl-2-pyrrolidone (NMP), acetone, or a combination thereof.   The ink composition of claim 8, wherein the monomer comprises at least one acrylic monomer.   The acrylic monomer is 1,3-butylene glycol diacrylate, 1,6-hexanediol diacrylate, 1,3-butylene glycol dimethacrylate, isobornyl acrylate, or isodecyl methacrylate, or their 12. A composition according to claim 11 comprising a combination.   The ink composition according to claim 1, wherein the base ink comprises a UV curable ink.   The ink composition according to claim 1, wherein the ink composition is UV curable. (A) about 65 to about 85 weight percent of the base ink;
(B) from about 5 to about 20 weight percent of the ink removal promoting additive having a glass transition temperature of less than about 130 ° C .; and (c) about at least a portion of the ink removal promoting additive can be dissolved. The ink composition of claim 1 comprising from 5 to about 15 weight percent of the carrier. An ink composition for digital printing on a plastic article,
(A) base ink;
(B) an ink removal promoting additive having an acid number ranging from about 100 mg KOH / gram to about 250 mg KOH / gram; and (c) a carrier capable of dissolving at least a portion of the ink removal promoting additive. The ink composition.   The ink composition of claim 16, wherein the ink removal promoting additive comprises a styrene maleic anhydride copolymer.   The ink composition of claim 16, wherein the ink removal promoting additive has a glass transition temperature (Tg) in the range of about 50C to about 130C.   The ink composition of claim 16, wherein the ink removal promoting additive has a glass transition temperature (Tg) in the range of about 55 ° C. to about 85 ° C.   The ink composition of claim 16, wherein the ink removal promoting additive has a glass transition temperature (Tg) in the range of about 55 ° C. to about 65 ° C.   The ink composition of claim 16, wherein the ink removal promoting additive has an acid number ranging from about 150 mg KOH / gram to about 205 mg KOH / gram.   The ink composition of claim 16, wherein the ink removal promoting additive has an acid number ranging from about 165 mg KOH / gram to about 205 mg KOH / gram.   The ink composition according to claim 16, wherein the carrier comprises a solvent, a monomer, or a combination thereof.   24. The ink composition of claim 23, wherein the solvent comprises at least one aprotic solvent.   The ink composition according to claim 23, wherein the solvent comprises N-methyl-2-pyrrolidone (NMP), acetone, or a combination thereof.   24. The ink composition of claim 23, wherein the monomer comprises at least one acrylic monomer.   The acrylic monomer is 1,3-butylene glycol diacrylate, 1,6-hexanediol diacrylate, 1,3-butylene glycol dimethacrylate, isobornyl acrylate, or isodecyl methacrylate, or their 27. The composition of claim 26, comprising a combination.   The ink composition according to claim 16, wherein the base ink comprises a UV curable ink.   The ink composition according to claim 16, wherein the ink composition is UV curable. (A) about 65 to about 85 weight percent of the base ink;
(B) from about 5 to about 20 weight percent of the ink removal promoting additive having an acid number ranging from about 150 mg KOH / gram to about 205 mg KOH / gram; and (c) at least a portion of the ink removal promotion additive. The ink composition of claim 16, comprising from about 5 to about 15 weight percent of the carrier capable of dissolving water. A recyclable plastic article,
The ink comprising a composition comprising: the curved outer surface having a digitally printed image printed directly on the curved outer surface; the image comprising cured droplets of ink; and an ink removal promoting additive having a glass transition temperature of less than about 130 ° C. Droplets, including
The removal promoting additive when the digitally printed image has an adhesion score of at least 6.0 and 9.0, and when the digitally printed image is exposed to the basic solution at an elevated temperature of at least about 70 ° C The recyclable plastic article configured to separate or release the cured droplet of ink from the curved outer surface of the article.   32. The plastic article of claim 31, wherein the article comprises a plastic container.   The plastic article of claim 32, wherein the plastic container is a bottle.   32. The plastic article of claim 31, wherein the ink removal promoting additive comprises a styrene maleic anhydride copolymer.   32. The plastic article of claim 31, wherein the ink removal promoting additive has a glass transition temperature (Tg) in the range of about 50 <0> C to about 110 <0> C.   The plastic article of claim 31, wherein the ink removal promoting additive has a glass transition temperature (Tg) in the range of about 55 ° C. to about 85 ° C.   32. The plastic article of claim 31, wherein the ink removal promoting additive has a glass transition temperature (Tg) in the range of about 55 [deg.] C to about 65 [deg.] C.   32. The ink composition of claim 31, wherein the ink removal promoting additive has an acid number ranging from about 150 mg KOH / gram to about 205 mg KOH / gram.   32. The ink composition of claim 31, wherein the ink removal promoting additive has an acid number ranging from about 165 mg KOH / gram to about 205 mg KOH / gram.   32. The plastic article of claim 31, wherein the article comprises one or more of the following materials: polyethylene, polyethylene terephthalate, high density polyethylene, and polypropylene.   When the digitally printed image is exposed to a basic solution having a pH in the range of about 12-13 at an elevated temperature in the range of about 70-90 ° C., the removal-promoting additive causes the cured droplets of ink to flow into the article. 32. The plastic article of claim 31, wherein the plastic article is configured to separate or release from the curved outer surface of the.   42. The plastic article of claim 41, wherein after exposure to the basic solution at the elevated temperature, at least about 90 weight percent of the cured ink droplets separate from the curved outer surface of the article.   The digitally printed image includes a base coat including a plurality of cured base coat ink droplets and a secondary coat including a plurality of cured secondary coat ink droplets, the secondary coat being applied to at least a portion of the base coat. 32. The plastic article of claim 31. A method for removing cured ink from a plastic container, the method comprising:
(A) the curved outer surface in which a digital image is printed directly on the curved outer surface of the plastic container by a drop-on-demand ink jet printing process, and includes at least 6 cured droplets of ink applied directly to the curved outer surface of the plastic container; A plastic container having the image having an adhesion score of 0.0 and about 9.0, and the droplet of ink comprising a composition comprising an ink removal promoting additive having a glass transition temperature of less than about 130 ° C. To do;
(B) exposing at least a portion of the digitally printed image of the plastic container to a basic solution at an elevated temperature of at least about 70 ° C .; and (c) printing at least a portion of the digitally printed image with the image. Removing from the curved outer surface.   45. The method of claim 44, wherein the container is a bottle.   45. The method of claim 44, wherein the ink removal promoting additive comprises a styrene maleic anhydride copolymer.   45. The method of claim 44, wherein the ink removal promoting additive has a glass transition temperature (Tg) in the range of about 50C to about 110C.   45. The method of claim 44, wherein the ink removal promoting additive has a glass transition temperature (Tg) in the range of about 55C to about 85C.   45. The method of claim 44, wherein the ink removal promoting additive has a glass transition temperature (Tg) in the range of about 55C to about 65C.   45. The method of claim 44, wherein the ink removal promoting additive has an acid number ranging from about 150 mg KOH / gram to about 205 mg KOH / gram.   45. The method of claim 44, wherein the ink removal promoting additive has an acid number ranging from about 165 mg KOH / gram to about 205 mg KOH / gram.   45. The method of claim 44, wherein the basic solution is an aqueous solution having a pH in the range of about 12-13, and the elevated temperature is in the range of about 70-90 ° C.   45. The method of claim 44, wherein the plastic container comprises one or more of the following materials: polyethylene, polyethylene terephthalate, high density polyethylene, and polypropylene.   45. The method of claim 44, wherein the removing step comprises scraping or wiping the ink from the container after exposure of the image to the basic solution.   45. The method of claim 44, wherein the ink is mechanically removed in the form of flakes or films.

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