UV-Crosslinkable Adhesive Stabilization via UV Absorbers
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Solution Overview
Problem
UV-crosslinkable meltable pressure-sensitive adhesives face challenges with sensitivity to process parameter deviations, leading to unstable product properties and complex process control, particularly due to the limitations of commercially available UV-crosslinkable polymers and the interference of thermal stabilizers with photoinitiators, resulting in issues with cohesion and adhesion.
Innovation Solution
Incorporating a UV stabilizer from the group of UV absorbers and/or inhibitors, specifically selected to match the concentration of the photoinitiator based on absorption maxima, to expand the process window and stabilize product properties against fluctuations in UV dose and process parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If UV-crosslinkable polymers with photoinitiators are used to enable UV crosslinking, then adhesive strength and cohesion can be improved through crosslinking, but the system becomes highly sensitive to process parameter deviations and UV dose variations, leading to unstable product properties
Solution Approach 1:
The patent modifies the chemical composition parameters by introducing specific UV stabilizers (benzotriazoles, benzophenones, or hindered amines) at controlled concentrations (0.01-5 wt%) to alter the system's response to UV radiation, thereby stabilizing the crosslinking process and reducing sensitivity to dose variations
Solution Approach 2:
UV stabilizers are introduced as intermediary substances that mediate between the photoinitiator and UV radiation, controlling the crosslinking reaction rate and protecting against excessive or insufficient crosslinking, thus stabilizing adhesive properties against process fluctuations
2Ease of manufacture
If thermal stabilizers are added to prevent premature crosslinking during processing, then processability is improved, but the stabilizers interfere with photoinitiator effectiveness, leading to poor cohesion and unfavorable application properties
Solution Approach 1:
The patent extracts or removes conventional thermal stabilizers from the formulation and replaces them with UV-specific stabilizers that do not interfere with photoinitiator activity, thereby eliminating the negative interaction while maintaining protection against premature crosslinking
Solution Approach 2:
The patent employs UV stabilizers that function specifically during the UV curing process and can be consumed or deactivated after serving their protective function, allowing effective crosslinking without long-term interference with adhesive performance
3Strength
If the concentration of photoinitiator is increased to ensure complete crosslinking, then adhesive strength is improved, but the system becomes even more sensitive to UV dose variations and process control deviations
Solution Approach 1:
UV stabilizers act as intermediaries that buffer the interaction between photoinitiator and UV radiation, creating a more gradual and controlled crosslinking response that reduces sensitivity to photoinitiator concentration variations and UV dose fluctuations
Solution Approach 2:
The UV stabilizers provide a cushioning effect by absorbing excess UV energy and preventing runaway crosslinking reactions, thereby compensating for variations in process parameters and ensuring consistent adhesive properties
4Strength
If UV dose is increased to compensate for lamp performance degradation and maintain crosslinking quality, then adhesive properties can be maintained, but energy consumption increases and process control complexity increases
Solution Approach 1:
The UV stabilizers provide a time-dependent protective effect that compensates for lamp aging, allowing maintenance of consistent adhesive properties without increasing UV dose, thereby reducing energy consumption compared to uncompensated systems
Solution Approach 2:
The introduction of UV stabilizers changes the system's response characteristics to UV radiation, creating a broader process window that maintains adhesive quality across varying UV doses and lamp performance levels
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 use of UV stabilizers allows for more robust and stable adhesive properties, reducing sensitivity to UV dose variations and process fluctuations, ensuring consistent product quality and reproducibility, and enabling the production of UV-crosslinkable pressure-sensitive adhesives with improved cohesion and adhesion.
Implementation Method 1
Incorporating a UV stabilizer from the group of UV absorbers and/or inhibitors
Implementation Method 2
UV-crosslinkable polyacrylate polymers which are selected from a) mixtures of UV-crosslinkable polymers with at least one photoinitiator
Implementation Method 3
UV-crosslinkable and meltable pressure-sensitive adhesives
Data Source
Figure 1
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Figure 4
AI summary
Composition which is a UV-crosslinkable and meltable pressure-sensitive adhesive mass, comprises (i) mixtures of UV-crosslinkable polyacrylate polymers comprising (ia) mixtures of UV-crosslinkable polymers having at least one photoinitiator which is covalently bonded to polymer backbone of the polymers or (ib) mixtures of UV-crosslinkable polyacrylate polymers, monomers and at least one photoinitiator, and (ii) at least one UV-stabilizer. Independent claims are also included for: (1) preparing the above composition, comprising mixing the components (i) and (ii); (2) use of the composition for producing adhesive, transfer adhesive mass, an adhesive transfer tape or a coated carrier, in which the meltable pressure-sensitive adhesive mass as a melt at 60-200[deg] C is applied in the form of a uniform coating having a layer thickness of 2-200 mu m optionally on a carrier or a transfer carrier, and the coating is crosslinked with a high energy radiation having a radiation energy of 10-150 mJ/cm 2>; (3) the adhesive obtainable from the composition; and (4) a sheet-like adhesive in the form of a carrier coated with the above UV-crosslinked composition, preferably a carrier coated with a UV-curable- or UV-crosslinked pressure-sensitive adhesive mass, where the sheet-like adhesive comprises a label, adhesive tape, cable wrapping tape or protective film or a sheet-like transfer adhesive composition or a transfer adhesive tape.