Recycling-Compatible PSA Label with Water-Dispersible Acrylate Polymer
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Solution Overview
Problem
The challenge in the label industry is to create a pressure-sensitive adhesive (PSA) label that is both user-friendly for various surfaces and environmentally sustainable, particularly recyclable, as existing labels with water-based PSA compositions containing alkyl phenol ethoxylates are toxic and hinder the paper recycling process due to adhesive residue contamination.
Innovation Solution
A PSA label with a water-dispersible acrylate polymer composition without vinyl acetate, featuring high shear and storage moduli, and a non-ionic copolymer based on polyethylene glycol and polypropylene glycol, which adheres well to paper surfaces and disintegrates into larger fragments under aqueous conditions, facilitating easy separation during paper recycling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If water-based PSA containing alkyl phenol ethoxylates is used, then adhesion performance is improved, but environmental toxicity and recycling compatibility deteriorate
Solution Approach 1:
The patent changes the chemical composition parameters of the PSA by replacing APEO surfactants with alternative surfactant systems (such as alkyl polyglucosides or other non-ionic surfactants) and adjusting the polymer composition to achieve comparable adhesion performance without the toxic effects of APEO, thereby resolving the contradiction between adhesion performance and environmental toxicity
Solution Approach 2:
The patent employs a water-based PSA formulation that is specifically designed to be removable and compatible with recycling processes, accepting that the adhesive will leave some residue or require removal, rather than pursuing permanent bonding that would hinder recycling. This approach prioritizes environmental sustainability over complete adhesion permanence
2Strength
If water-based PSA containing alkyl phenol ethoxylates is used, then adhesion performance is improved, but paper recycling compatibility deteriorates due to adhesive residue contamination
Solution Approach 1:
The patent modifies the PSA composition parameters by eliminating APEO and adjusting the polymer-surfactant ratio to create a formulation that maintains adequate adhesion while being more readily removable during paper recycling, thus improving recycling compatibility without completely sacrificing adhesion performance
Solution Approach 2:
The patent accepts that some adhesive residue may remain on the paper after recycling, employing a formulation that provides sufficient adhesion for its intended use but is designed to allow partial removal or degradation during the recycling process, rather than attempting to achieve complete removal which would compromise adhesion performance
3Ease of operation
If removable PSA characteristics are enhanced, then paper surface damage is avoided, but adhesion strength deteriorates
Solution Approach 1:
The patent carefully balances the compositional parameters of the PSA, including polymer molecular weight, surfactant concentration, and cross-linking density, to achieve an optimal range where the adhesive is strong enough for its intended application but weak enough to be removable without damaging the paper substrate, thus resolving the contradiction between adhesion strength and removability
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 label achieves effective adhesion to paper surfaces while remaining compatible with paper recycling processes, reducing adhesive residue contamination and enhancing the recyclability of paper products, as demonstrated by high Removal Scores and S2000 values in industrial-scale testing.
Implementation Method 1
a pressure sensitive adhesive layer, the adhesive layer having a coat weight equal to or higher than 10 g/m2
Implementation Method 2
the composition has been selected to comprise water-dispersible acrylate polymer formed of monomers without vinyl acetate
Implementation Method 3
the pressure sensitive adhesive layer is configured to disintegrate into large fragments under aqueous conditions which simulate unit operations of a deinking plant
Data Source
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AI summary
The invention relates to a label which is attachable to object surfaces and to a manufacturing method thereof, the label comprising a pressure sensitive adhesive layer having a coat weight equal to or higher than 10 g/m2 and wherein the adhesive layer has a composition which is free of alkylphenol ethoxylate and has been selected to comprise emulsion polymerized, water-dispersible acrylate polymer and non-ionic copolymer based on polyethylene glycol and polypropylene glycol such that when the adhesive layer is subjected to paper recycling process conditions, the adhesive layer resists disintegration into small fragments.