HMPSA Label Composition for Residue-Free Alkaline Debonding
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Solution Overview
Problem
Existing self-adhesive labels for packages and containers are difficult to completely debond during recycling processes without leaving adhesive residues, especially when subjected to hot alkaline solutions, which complicates the recycling and reprocessing of materials.
Innovation Solution
A hot-melt pressure-sensitive adhesive composition comprising 25-50% styrene block copolymers, 35-75% compatible tackifying resins with a softening temperature between 80-150°C and an acid number of less than 20, and 0.5-20% carboxylic acids, allowing for permanent adhesion at room temperature and easy debonding in a basic aqueous solution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional pressure-sensitive adhesives are used for self-adhesive labels, then strong bonding to substrates is achieved, but complete debonding without adhesive residues is difficult during recycling processes
Solution Approach 1:
The adhesive composition uses a specific formulation with styrene block copolymers (25-50%), compatible tackifying resins with softening temperature 80-150°C and acid number <20 (35-75%), and carboxylic acids (0.5-20%). This parameter optimization enables the adhesive to maintain strong bonding at room temperature while allowing complete debonding in hot alkaline solutions during recycling, resolving the contradiction between bonding strength and ease of debonding.
Solution Approach 2:
The invention employs a composite adhesive system combining styrene block copolymers, tackifying resins, and carboxylic acids. This composite formulation creates an adhesive that exhibits dual behavior: strong adhesion to substrates under normal conditions and complete solubility/detachment in hot alkaline environments, thereby achieving both strong bonding and easy debonding without residues.
2Ease of operation
If hot alkaline solutions are used for debonding labels during recycling, then label separation is achieved, but adhesive residues remain on the substrate surface
Solution Approach 1:
The adhesive is formulated with tackifying resins having softening temperature 80-150°C and acid number <20, combined with carboxylic acids. These parameter choices ensure that the adhesive becomes completely soluble and detachable in hot alkaline solutions (60-100°C), achieving complete label separation without leaving any adhesive residues on the substrate, thus eliminating the harmful effect of residues.
3Ease of operation
If aqueous emulsion PSAs are used for label adhesives, then debonding in hot alkaline solutions is facilitated, but the adhesive passes into solution or suspension requiring additional reprocessing
Solution Approach 1:
The invention uses a hot-melt pressure-sensitive adhesive based on styrene block copolymers with specific molecular architecture and composition, rather than aqueous emulsions. This parameter change ensures that while the adhesive debonds easily in hot alkaline solutions, it does so by detaching as an intact film rather than dissolving, thereby minimizing adhesive loss and eliminating the need for additional reprocessing of the washing solution.
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 adhesive composition provides strong and permanent bonding to substrates while ensuring complete debonding without leaving residues, reducing the need for additional washing treatments and minimizing environmental contamination during recycling.
Implementation Method 1
Pressure-sensitive adhesives or PSAs are substances giving the support coated therewith a tack at room temperature, which allows its instantaneous adhesion to a substrate under the effect of brief slight pressure
Implementation Method 2
These recycling processes, such as the one used for cleaning spent glass bottles, for example beer bottles, generally include a step of immersing the article to be cleaned in basic aqueous compositions maintained at temperatures between 60 and 100° C. The purpose of such a step is to debond the label fastened to the article
Implementation Method 3
A hot-melt pressure-sensitive adhesive composition comprising 25-50% styrene block copolymers, 35-75% compatible tackifying resins with a softening temperature between 80-150°C and an acid number of less than 20, and 0.5-20% carboxylic acids, allowing for permanent adhesion at room temperature and easy debonding in a basic aqueous solution
Data Source
AI summary
The present invention relates to a hot-melt pressure-sensitive adhesive (HMPSA) composition. The composition includes: a) 25 to 50% of a styrene block copolymer chosen from the group comprising SIS, SIBS, SEBS and SEPS block copolymers; b) 35 to 75% of a compatible tackifying resin having a softening temperature of between 80 and 150° C. and an acid number of less than 20; and c) 0.5 to 20% of one or more carboxylic acids, the hydrocarbon chain of which includes 6 to 22 carbon atoms. The present invention also relates to a multilayer system including an HMPSA layer, a printable support layer, and an adjacent protective layer. Further, the present invention also includes a corresponding self-adhesive label and process for recycling a labeled article which entails debonding of the label by immersing the article in a hot basic aqueous solution.