Methods and compositions for direct print having improved recyclability
View Patent ↗The disclosure relates to ink compositions for digital printing on an external surface of a plastic article. The ink compositions comprise an ink removal-promoting additive. In some aspects, the ink removal-promoting additive can facilitate the separation or loosening of the image from the external surface of the article when the image is exposed to a liquid-based solution at an elevated temperature. Also disclosed are recyclable plastic articles having an external surface with an image printed thereon using the disclosed ink composition and methods for removing cured ink from a plastic container. This abstract is intended as a scanning tool for purposes of searching in the particular art and is not intended to be limiting of the present invention.
1. A recyclable plastic article comprising:
a curved external surface with a digitally-printed image printed directly on the curved external surface, the image comprising cured droplets of ink, and the droplets of ink comprising a composition, wherein the composition comprises:
(a) from about 65 to about 85 weight percent of a base ink;
(b) from about 5 to 20 weight percent of an ink removal-promoting additive having a glass transition temperature less than about 130° C.; and
(c) from about 5 to about 15 weight percent of a carrier capable of dissolving at least a portion of the ink removal-promoting additive;
wherein the digitally-printed image has an adhesion score of at least 6.0 and up through 9.0, and the removal-promoting additive is configured to cause the cured droplets of ink to separate or loosen from the curved external surface of the article when the digitally-printed image is exposed to the basic solution at an elevated temperature of at least about 70° C.
2. The plastic article of claim 1 , wherein the article comprises a plastic container.
3. The plastic article of claim 2 , wherein the plastic container is a bottle.
4. The plastic article of claim 1 , wherein the ink removal-promoting additive comprises a styrene maleic anhydride copolymer.
5. The plastic article of claim 1 , wherein the ink removal-promoting additive has a glass transition temperature (Tg) in the range of from about 50° C. to about 110° C.
6. The plastic article of claim 1 , wherein the ink removal-promoting additive has a glass transition temperature (Tg) in the range of from about 55° C. to about 85° C.
7. The plastic article of claim 1 , wherein the ink removal-promoting additive has a glass transition temperature (Tg) in the range of from about 55° C. to about 65° C.
8. The plastic article of claim 1 , wherein the ink removal-promoting additive has an acid number in the range of from about 150 mg KOH/gm to about 205 mg KOH/gm.
9. The plastic article of claim 1 , wherein the ink removal-promoting additive has an acid number in the range of from about 165 mg KOH/gm to about 205 mg KOH/gm.
10. The plastic article of claim 1 , wherein the article is comprised of one or more of the following materials: polyethylene, polyethylene terephthalate, high density polyethylene, and polypropylene.
11. The plastic article of claim 1 , wherein the removal-promoting additive is configured to cause the cured droplets of ink to separate or loosen from the curved external surface of the article when the digitally-printed image is exposed to a basic solution having a pH in the range of from about 12-13 at an elevated temperature in the range of from about 70 to 90° C.
12. The plastic article of claim 11 , wherein after an exposure to the basic solution at the elevated temperature, at least about 90 weight percent of the cured ink droplets separate from the curved external surface of the article.
13. The plastic article of claim 1 , wherein 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.