Recyclable Ink Formulations for PET Shrink Sleeve Labels

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Solution Overview

Problem

Shrink sleeve labels on PET containers pose challenges during recycling due to ink solubility in hot caustic solutions, leading to contamination and degradation of recycled PET flake, which affects its quality and commercial value.

Innovation Solution

Development of ink compositions resistant to dissolving in hot caustic solutions, comprising specific resins like polyvinyl chloride-polyvinyl acetate copolymer, semi-aliphatic polyurethane, and polymethyl methacrylate copolymer, along with solvent and colorants such as Diarylide Yellow AAMX and Copper Phthalocyanine, that form insoluble precipitates, allowing easy separation and minimizing contamination.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If conventional inks are used on shrink sleeve labels, then the labels can be printed with diverse colors and designs, but the inks dissolve in hot caustic solutions during recycling, causing contamination and staining of PET flake

Engineering Contradiction:

Improvecolor diversityVSAvoidink contamination

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

The patent changes the chemical parameters of the ink composition by using water-insoluble pigments and specific resin systems that resist dissolution in hot caustic solutions, thereby maintaining color diversity while eliminating contamination during recycling

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite ink system combining specific resins (acrylic, vinyl, or polyurethane) with water-insoluble pigments and solvents, forming a composition that provides both printing versatility and resistance to caustic solution dissolution during recycling

Inventive Principle:

Principle #40Composite materials

2Manufacturing precision

If inks are removed completely during hot caustic wash cycle, then the PET flake quality is maintained, but the inks recontaminate the commingled polyester materials

Engineering Contradiction:

Improveflake qualityVSAvoidrecontamination

Core Design Contradiction:

Manufacturing precisionVSObject-generated harmful factors

Solution Approach 1:

The patent applies preliminary anti-action by formulating inks that are resistant to dissolution in hot caustic solutions from the outset, preventing the harmful effect of recontamination before it can occur during the recycling process

Inventive Principle:

Principle #9Preliminary anti-action

Solution Approach 2:

The patent changes the solubility parameters of the ink composition to be insoluble in hot caustic solutions, thereby preventing both initial contamination and subsequent recontamination of the PET flake during recycling

Inventive Principle:

Principle #35Parameter changes

3Ease of operation

If shrink sleeve labels are used on PET containers, then the labels can be easily applied by heat shrinking, but the labels and inks are difficult to separate downstream during recycling

Engineering Contradiction:

Improvelabel applicationVSAvoidseparation difficulty

Core Design Contradiction:

Ease of operationVSDevice complexity

Solution Approach 1:

The patent extracts the harmful ink component from the recycling stream by using water-insoluble formulations that do not dissolve in hot caustic solutions, allowing the label to be removed while the ink remains on the label material and does not contaminate the PET flake

Inventive Principle:

Principle #2Taking out (Extraction)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The ink compositions effectively prevent staining and contamination of recycled PET, enabling simultaneous recycling of PET bottles and labels without compromising the quality of the recycled polymer flake, as demonstrated by minimal color change and contamination in caustic wash solutions.

Implementation Method 1

ink compositions that are resistant to dissolving in a hot caustic solution

Methodology Applied

Scientific EffectInsolubility:

Implementation Method 2

form insoluble precipitates, allowing easy separation

Methodology Applied

Scientific EffectPrecipitation: Precipitation

Data Source

PatentUS20240101837A1Removable printing inks for recyclable plastics

Publication Date: 2024.03.28 SUN CHEMICAL CORP

AI summary

Described herein are ink compositions that will not contaminate recycled plastic materials that come in contact with the inks; labels printed with such inks; and plastic articles having labels printed with such inks; and methods for printing with such inks, and recycled plastic material, such as recycled PET, that has little to no contamination from such inks. For example, during recycling, plastic containers that have been labelled with such inks are subjected to hot caustic wash solutions that cause the ink to separate the labels, When the inks described herein are removed from the label, they form a solid or precipitate, as opposed to dissolving in the hot caustic wash solution. The solid or precipitate is easily separated from the recycled plastic and wash solution, such as by filtration. The separated ink does not contaminate or stain the recycled plastic, or does so to a degree that is tolerable.