Water-Soluble UV Adhesive for Hydrophobic Label Removal
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Solution Overview
Problem
Existing methods for adhering labels to substrates, particularly water-repellent ones, face challenges in achieving strong adhesion in humid environments and easy removal with aqueous alkaline solutions, often requiring complex application processes and expensive hot-melt adhesives that can decompose or leave residue.
Innovation Solution
A radiation-curable pressure-sensitive adhesive is applied to a label material with high water permeability, allowing for cross-linking and strong adhesion to hydrophobic substrates, which can be completely removed in an alkaline aqueous solution by enhancing water solubility and using perforations to facilitate quick water penetration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If hot-melt adhesives are used for labeling, then strong adhesion is achieved, but the adhesive can decompose during processing and leave residue on substrates
Solution Approach 1:
The patent changes the chemical composition parameters of the adhesive by incorporating water-soluble polymers (polyvinyl alcohol, carboxymethyl cellulose, starch derivatives) and making the adhesive solvent-free and water-based, which prevents thermal decomposition while maintaining adhesion strength
Solution Approach 2:
The adhesive is designed to be water-soluble and removable, effectively making it a temporary bonding agent that can be easily eliminated after serving its purpose, preventing permanent residue issues
2Reliability
If labels are made from impermeable or difficult-to-permeable foils, then label durability is improved, but aqueous washing solution cannot penetrate to detach the adhesive completely
Solution Approach 1:
The patent specifies that labels should be made from water-permeable materials or materials with sufficient porosity to allow washing solution penetration, balancing durability with removability capabilities
Solution Approach 2:
The water-soluble adhesive acts as an intermediary that facilitates complete removal by allowing washing solution to penetrate through the label material and dissolve the adhesive uniformly across the bonding interface
3Productivity
If liquid or aqueous adhesives are applied to labels on-line and immediately stuck to substrates, then production efficiency is improved, but time-delayed work steps occur when changing labels and production interruptions happen upon errors
Solution Approach 1:
The adhesive is pre-applied to labels in advance during label production, allowing labels to be stored and ready for application without requiring on-line adhesive application, thus eliminating production interruptions when changing labels or correcting errors
4Strength
If radiation-curable pressure-sensitive adhesive is used, then strong adhesion to hydrophobic substrates is achieved, but the adhesive must be completely soluble in alkaline solution for removal
Solution Approach 1:
The patent creates a composite adhesive system combining radiation-curable components (for strong adhesion) with water-soluble polymers (for alkaline solubility), achieving both strong bonding and easy removal properties simultaneously
Solution Approach 2:
The adhesive exhibits different properties in different conditions: it forms strong crosslinked bonds under UV radiation for adhesion, but dissolves completely in alkaline solutions for removal, with the label material also having specific water absorption characteristics to facilitate removal
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 solution ensures strong, durable adhesion to substrates in humid conditions and easy removal with minimal residue, reducing production interruptions and environmental impact, while avoiding the costs and issues associated with hot-melt adhesives.
Implementation Method 1
a radiation-curable pressure-sensitive adhesive which has been cross-linked by actinic radiation
Implementation Method 2
the adhesive being a radiation-curable pressure-sensitive adhesive which can be detached from the substrate surface by aqueous alkaline solutions
Data Source
AI summary
The invention relates to a method for gluing labels on hydrophobic substrates, wherein a radiation cross-linking, pressure-sensitive adhesive is applied on the label or on the substrate on a surface opposite to the label and irradiated with UV or electron radiation, and label and substrate are then brought together and glued to one another. The pressure-sensitive adhesive is soluble in aqueous solutions. The label is selected from i) water permeable labels with a water uptake (Cobb value) greater than 0.2 g/m2 per 20 sec, and ii) perforated labels which have perforations or cut-outs of less than 10% on the glued surfaces. Furthermore, the invention describes a label, coated with a water-soluble, radiation curable, pressure sensitive adhesive, which has a high water uptake and/or optionally perforations or cut-outs on the glued surface.