Removable PSA Composition for Filmic Label Separation
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Solution Overview
Problem
The existing polymeric packaging systems face challenges in recycling due to the resistance of pressure-sensitive filmic labels, which fail to release during the recycling process, leading to contamination and reduced clarity of recycled PET, necessitating a pressure-sensitive adhesive (PSA) that facilitates separation while maintaining performance properties.
Innovation Solution
A PSA composition comprising a monomer mixture with specific acrylic acid esters, mono-olefinically unsaturated monomers, and a polyhydrazide crosslinker, designed to achieve a peel adhesion value between 70N/m and 700N/m, allowing for 0% to 8% film remaining on PET after sink-float testing, ensuring efficient separation during recycling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional pressure-sensitive adhesives are used in filmic labels, then the labels maintain strong adhesion to polymeric packaging during use, but the labels resist separation during the recycling process, leading to contamination and reduced clarity of recycled PET
Solution Approach 1:
The adhesive composition uses a specific monomer mixture including acrylic acid esters with controlled glass transition temperatures, aldehyde/ketone functional monomers, and polyhydrazide crosslinkers to achieve optimal balance between adhesion and recyclability. The crosslink density and monomer ratios are precisely controlled to enable adhesive failure at recycling temperatures while maintaining strong bond during use.
Solution Approach 2:
The invention creates a composite adhesive system combining multiple monomer types (acrylic acid esters, aldehyde/ketone monomers, polyhydrazide crosslinkers) that work synergistically. This composite composition provides both the required adhesion strength for application and the controlled release properties for recycling, resolving the contradiction between strong bonding and easy separation.
2Strength
If filmic labels are made more resistant to recycling conditions, then the labels maintain integrity during handling and application, but a portion of the label remains attached after the recycling process, contaminating the recycled material
Solution Approach 1:
The adhesive's glass transition temperature and crosslink density are optimized to create a threshold effect: the adhesive maintains strong bonding at ambient and application temperatures (preserving label integrity) but undergoes controlled failure at the elevated temperatures and chemical conditions of the recycling process (preventing contamination).
Solution Approach 2:
The invention converts the potential harm of strong adhesion (which prevents label removal) into a benefit by designing the adhesive to fail in a controlled manner during recycling. The strong initial bond ensures proper application, while the controlled failure at recycling conditions ensures clean separation, turning the adhesion strength from a problem into a solution.
3Ease of manufacture
If the adhesive is designed to release easily during recycling, then the label separates from the packaging, but the adhesion performance during the article's life cycle is compromised
Solution Approach 1:
The monomer composition and crosslinking density are precisely controlled to create an adhesive with temperature-dependent adhesion characteristics. The adhesive maintains high strength at service temperatures but exhibits controlled reduction in adhesion at recycling temperatures, achieving both requirements through parameter optimization.
Solution Approach 2:
The adhesive's bonding characteristics are made dynamic rather than static. The crosslinked polymer network provides stable adhesion under normal conditions but undergoes controlled structural changes at recycling conditions, enabling the adhesive to transition from a strong bond state to a release state in response to environmental changes during the recycling process.
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 PSA composition effectively separates filmic labels from PET, maintaining desired performance properties and ensuring efficient recycling by achieving low film remaining on PET, thus enhancing the recyclability and clarity of PET materials.
Implementation Method 1
a monomer mixture comprises (a) at least one monomer which may undergo free radical polymerization
Implementation Method 2
whose homopolymer has a glass transition temperature of less than or equal to 10°C
Implementation Method 3
the plastic flake is separated in a sink-float process from the removed label
Data Source
Figure 1
AI summary
Disclosed are removable pressure sensitive adhesive compositions (PSAs) useful with facestocks and/or packaging labels designed to be removed in the recycling of polymeric packaging. The PSAs of the invention include (a) at least one monomer which may undergo free radical polymerization and whose homopolymer has a glass transition temperature of less than or equal to 10°C, (b) at least one mono-olefinically unsaturated monomer having aldehyde or ketone functionality, and (c) an effective amount of at least one polyhydrazide crosslinker having hydrazine functionality. The PSA composition of the invention exhibits a peel adhesion value of between about 0.4 lbs/in (70N/m) and about 4 lbs/in (700N/m), and the percent film remaining on the polymeric packaging after a sink-float testing is 0% to about 8%.