US 12,351,719 B2
Water-based washable printing inks for recycled plastics
Alexander Lahr, Charlotte, NC (US); and Bruce Marshall, Charlotte, NC (US)
Assigned to Sun Chemical Corporation, Parsippany, NJ (US)
Appl. No. 18/572,151
Filed by SUN CHEMICAL CORPORATION, Parsippany, NJ (US)
PCT Filed Jun. 28, 2022, PCT No. PCT/US2022/035309
§ 371(c)(1), (2) Date Dec. 19, 2023,
PCT Pub. No. WO2023/278440, PCT Pub. Date Jan. 5, 2023.
Claims priority of provisional application 63/216,598, filed on Jun. 30, 2021.
Prior Publication US 2024/0301224 A1, Sep. 12, 2024
Int. Cl. C09D 11/107 (2014.01); C09D 11/033 (2014.01); C09D 11/037 (2014.01)
CPC C09D 11/107 (2013.01) [C09D 11/033 (2013.01); C09D 11/037 (2013.01)] 18 Claims
 
1. A method for recycling plastic material from a container, wherein the container comprises said plastic material, and wherein a water based ink is applied either directly to the container or to a label attached to the container, the method comprising
a) providing a plastic container comprising
a surface which has been printed on with a water based ink, or
a label which has been printed on with a water based ink;
wherein the water based ink comprises i) water and ii) a polymer selected from a self-crosslinking acrylic copolymer resin or an aliphatic, non-ionic, polyester polyurethane based resin dispersion in water,
wherein the self-crosslinking acrylic copolymer resin comprises a polymer backbone,
wherein the self-crosslinking acrylic copolymer resin comprises a crosslinking agent attached to the polymer backbone in the resin,
which ink is removable in the form of solid particles but are not dissolvable in hot caustic wash; and
wherein the majority of any water/organic solvent mixture present in the ink is water;
b) immersing the container in a hot caustic wash to remove the inks as a particulate precipitate that is essentially insoluble in the caustic wash;
c) separating the plastic material of the container from the ink precipitate and the hot caustic wash;
d) grinding the recyclable container into clear recycled plastic flake;
wherein the clear recycled plastic flake has Δ values when compared to virgin flake of:
ΔL: <10
Δa: <2.5
Δb: <2.5;
wherein the plastic material is not stained or contaminated by the water based ink during recycling; and
wherein the hot caustic wash is an aqueous solution of from 1 wt % to 3 wt % NaOH and/or non-ionic surfactant, at from 70° C. to 95° C.