Wash-off Label Adhesive Crosslinking for Alkaline Detachment
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Solution Overview
Problem
Existing water-based pressure sensitive adhesives used in wash-off labels suffer from limitations in adhesive strength, poor wet anchorage, and contamination of washing solutions and recyclable materials during alkaline washing processes.
Innovation Solution
A wash-off label comprising a water-borne pressure sensitive adhesive with a specific composition including an acrylic polymer and a crosslinking agent with dihydrazide functionality, which remains attached to the face material during alkaline washing, preventing contamination and enabling reuse of washing solutions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If water-borne pressure sensitive adhesive is used in wash-off labels, then environmental compliance and cost-efficiency are improved, but adhesive strength and wet anchorage deteriorate
Solution Approach 1:
The patent modifies the chemical composition parameters of the water-borne adhesive by incorporating specific polymer types (acrylic, vinyl acetate, ethyl hexyl acrylate) and crosslinking agents (adipic dihydrazide, glutaric dihydrazide) in controlled ratios. The crosslinking density and polymer chain structure are adjusted to achieve optimal balance between water-based formulation and adhesive performance, enabling the adhesive to maintain strength while remaining environmentally compliant
Solution Approach 2:
The patent creates a composite adhesive system combining multiple polymer components (acrylic polymer, vinyl acetate, ethyl hexyl acrylate) with crosslinking agents and optional additives. This composite formulation synergistically combines the benefits of water-based adhesives (environmental compliance) with enhanced adhesive properties through polymer-polymer and polymer-crosslinker interactions, resolving the contradiction between eco-friendliness and performance
2Ease of manufacture
If water-based pressure sensitive adhesive is used in wash-off labels, then production cost is reduced, but wet anchorage and adhesive stability deteriorate
Solution Approach 1:
The patent applies crosslinking agents to the adhesive formulation in advance, creating pre-crosslinked or partially crosslinked polymer structures before the adhesive is applied to the substrate. This preliminary crosslinking action enhances the adhesive's resistance to water and alkaline conditions, ensuring stable wet anchorage during washing processes while maintaining the cost benefits of water-based formulations
Solution Approach 2:
The patent introduces crosslinking agents as intermediary substances that mediate between the hydrophilic water-based adhesive and the hydrophobic label substrate. These crosslinkers form bridging structures that improve interfacial adhesion and prevent adhesive disintegration in wet conditions, thereby enhancing reliability without compromising the economical water-based formulation
3Strength
If conventional adhesive is used in wash-off labels, then label attachment is achieved, but washing solution contamination and recyclable material contamination occur
Solution Approach 1:
The patent converts the typically harmful effect of strong adhesive bonding into a beneficial feature by designing the adhesive to preferentially bond to the label face material rather than to the washing solution or recyclable substrates. The crosslinked adhesive structure and optimized composition cause the adhesive to remain attached to the label during washing, transforming what would be contamination into a clean separation process that protects washing solution quality and recyclable material integrity
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 provides a detachable wash-off label that maintains adhesive strength while preventing contamination, allowing for the reuse of washing solutions and improving the quality of recyclable materials.
Implementation Method 1
The face comprises corona discharged filmic material, an adhesive receiving surface of the face being corona discharge treated
Implementation Method 2
at least one acrylic polymer comprising acrylic monomer(s) and/or non-acrylic comonomer(s) having a carbonyl group capable of undergoing a crosslinking reaction, and a crosslinking agent with dihydrazide functionality
Data Source
AI summary
The specification relates to a wash-off label (100, 200) comprising a face (101, 301) and a pressure sensitive adhesive (102, 302) adjoined to the face, wherein the face (101, 301) comprises corona discharged filmic material and the pressure sensitive adhesive (102, 302) has a composition including at least one acrylic polymer comprising acrylic monomer(s) and/or non-acrylic comonomer(s) having a carbonyl group capable of undergoing a crosslinking reaction, amount of the acrylic monomer(s) and/or non-acrylic comonomer(s) having a carbonyl group capable of undergoing a crosslinking reaction being from 0.1 to 5 wt. % of monomer composition, and a crosslinking agent with dihydrazide functionality, amount of the crosslinking agent being from 20 to 150% with respect to the amount of the carbonyl groups capable of undergoing a crosslinking reaction. The wash-off label (100, 200) is detachable from a surface when exposed to an alkaline washing solution at a temperature of 85 degrees C. the detachability being such that the pressure sensitive adhesive (102, 302) remains attached to the face (101, 301). Further, the specification relates to a labelled item and use of the wash-off label for labelling an item. Still further, the specification relates to a label laminate web and a method of manufacturing the wash-off label as well as to a pressure sensitive adhesive composition for a wash-off label.