One-Component PSA Composition with Reversible Metal Salt Crosslinking
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Solution Overview
Problem
Current aqueous pressure-sensitive adhesive (PSA) systems based on emulsion polymerization lack the adhesive properties and cohesion of solvent-based systems, primarily due to low branching and crosslinking, which impairs water resistance and interlooping of polymer chains across dispersion particle interfaces.
Innovation Solution
A one-component PSA composition is developed through emulsion polymerization using at least 60 wt% soft (meth)acrylic ester monomers, with 0.1-10 wt% methacrylic acid and 0-30 wt% styrene, featuring a gel content of at least 40 wt% with reversible crosslinking via metal salts, and optional covalent, irreversible crosslinking, to enhance cohesion and water resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If emulsion polymerization is used to produce aqueous PSA, then environmental friendliness is improved by avoiding organic solvents, but adhesive properties and cohesion deteriorate due to low crosslinking and branching
Solution Approach 1:
The patent changes the chemical parameters of the polymer by incorporating specific functional groups (carboxylic acid groups from methacrylic acid) and controlling gel content through reversible crosslinking with metal salts. This allows achieving high cohesion (gel content ≥40 wt%) in aqueous systems without organic solvents, resolving the contradiction between environmental friendliness and adhesive strength
Solution Approach 2:
The patent creates a composite system combining polymer chains with metal salt crosslinks. The reversible crosslinking through metal salts (such as aluminum, zinc, or calcium salts) forms a network structure that enhances cohesion while maintaining the aqueous nature of the system, thus improving strength without compromising environmental benefits
2Strength
If emulsion polymerization produces high gel content through crosslinking, then cohesion improves, but water resistance deteriorates due to impaired crosslinking across dispersion particle interfaces
Solution Approach 1:
The patent uses metal salts as intermediaries to bridge carboxylic acid groups on polymer chains from different dispersion particles. These metal salt crosslinks act as mediators that form reversible bonds across particle interfaces, enabling effective crosslinking that simultaneously improves cohesion and maintains water resistance by creating a continuous network structure
Solution Approach 2:
The patent employs reversible crosslinking through metal salts that can dynamically form and break bonds. This dynamic crosslinking allows the system to adapt to environmental conditions, maintaining cohesion while preserving water resistance through controlled reversibility of the crosslinking process
3Strength
If covalent irreversible crosslinking is used to increase gel content, then cohesion improves, but storage stability deteriorates due to coagulum formation
Solution Approach 1:
The patent inverts the conventional approach by using reversible crosslinking instead of irreversible crosslinking. The metal salt crosslinks can reversibly form and break, preventing permanent aggregation and coagulum formation during storage while still providing sufficient cohesion during use. This reversibility resolves the contradiction between cohesion and storage stability
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 composition achieves improved adhesive properties, including increased cohesion and heat stability, while maintaining storage stability and reducing coagulum formation, thereby surpassing the limitations of traditional aqueous PSA systems.
Implementation Method 1
the gel content is based at least partly on a reversible crosslinking by metal salts
Implementation Method 2
at least one pressure-sensitive adhesive polymer which is formed by emulsion polymerization of soft (meth)acrylic ester monomers, methacrylic acid, and optionally further monomers
Data Source
AI summary
A description is given of a one-component pressure-sensitive adhesive composition in the form of an aqueous polymer dispersion comprising at least one pressure-sensitive adhesive polymer which is formed by emulsion polymerization of soft (meth)acrylic ester monomers, methacrylic acid, and optionally further monomers, where the polymerization takes place in the presence of chain transfer agents or styrene. The pressure-sensitive adhesive polymer has a gel content which is based at least partly on a reversible crosslinking via metal salts. The one-component pressure-sensitive adhesive composition can be used for producing adhesive labels, adhesive tapes or adhesive foils.