Wash-Off Pressure-Sensitive Adhesive for Low-Temperature PET Recycling
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Solution Overview
Problem
Current pressure sensitive adhesives (PSAs) used on PET containers require high temperatures for removal, causing processing challenges and contamination, making it difficult to recycle PET containers with attached labels.
Innovation Solution
A pressure sensitive adhesive (PSA) layer composed of hydrophilic monomers, hydrophobic monomers, neutralizers, and surfactants, which can be washed off at low temperatures using an agitated bath at pH 7-14 and below 85°C, allowing easy label removal from PET substrates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional pressure sensitive adhesives are used on PET containers, then strong adhesion is achieved, but high temperature removal is required causing processing challenges and contamination
Solution Approach 1:
The patent modifies the chemical composition parameters of the adhesive by incorporating specific ratios of hydrophilic monomers (20-40%), hydrophobic monomers (50-70%), and functional monomers (10-30%), along with neutralizers and surfactants. This compositional parameter change enables the adhesive to maintain strong bonding during use while becoming water-soluble for easy removal at low temperatures, resolving the contradiction between adhesion strength and removal ease.
Solution Approach 2:
The patent creates a composite adhesive system combining hydrophilic and hydrophobic monomers in specific proportions, along with neutralizing agents and surfactants. This composite material structure provides dual functionality: the hydrophobic components ensure strong adhesion to PET substrates, while the hydrophilic components enable water solubility for easy removal, thus resolving the contradiction between strong bonding and easy removal.
2Ease of operation
If high temperature is used to remove PSA labels from PET, then label removal is achieved, but processing challenges and contamination increase
Solution Approach 1:
The patent changes the thermal and chemical parameters of the adhesive formulation to enable removal at temperatures below 85°C through water immersion. This parameter modification eliminates the need for high-temperature processing, thereby preventing contamination and processing challenges associated with thermal removal methods.
Solution Approach 2:
The patent replaces the thermal removal mechanism with a chemical dissolution mechanism. Instead of using heat to detach the label, the adhesive dissolves in water at low temperatures due to its hydrophilic monomer content and surfactant additives. This substitution of removal mechanism eliminates the harmful thermal effects and associated contamination.
3Reliability
If conventional PSAs are used, then permanent tackiness is achieved, but recyclability of PET containers is compromised
Solution Approach 1:
The patent introduces dynamic behavior to the adhesive system, where the adhesive properties change based on environmental conditions. During normal use, the adhesive maintains permanent tackiness for reliable bonding. However, when exposed to water during recycling processes, the hydrophilic monomers and surfactants activate, causing the adhesive to dissolve and detach. This dynamic response resolves the contradiction between reliable adhesion and recyclability.
Solution Approach 2:
The patent modifies the chemical parameters of the adhesive to include water-soluble components (hydrophilic monomers at 20-40% and surfactants at 1-5%). This parameter change enables the adhesive to transition from a permanent state during application to a soluble state during recycling, thereby maintaining both reliable performance and container recyclability.
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
Enables efficient and low-temperature removal of PSA labels from PET, reducing processing challenges and contamination, facilitating recyclability.
Implementation Method 1
a pressure sensitive adhesive (PSA) layer comprised of at least one hydrophilic monomer, at least one hydrophobic monomer, at least one neutralizer, and at least one surfactant... can be washed off at low temperatures using an agitated bath at pH 7-14 and below 85°C
Implementation Method 2
a pressure sensitive adhesive (PSA) layer comprised of at least one hydrophilic monomer, at least one hydrophobic monomer, at least one neutralizer, and at least one surfactant
Data Source
AI summary
A pressure sensitive adhesive (PSA) that can be washed of substrates is disclosed. The PSA can be comprised of at least one hydrophilic monomer, at least one hydrophobic monomer, at least one neutralizer and at least one surfactant. A label with an acrylic binder coasted substrate layer and a PSA layer wherein the PSA layer is comprised of at least one hydrophilic monomer, at least one hydrophobic monomer, at least one neutralizer, and at least one surfactant.