Multifunctional Halogenated Thioxanthone Photosensitizer for UV Curing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing UV-curable compositions using monofunctional thioxanthones as photosensitizers face issues with reproductive toxicity and migration out of cured formulations, particularly in food packaging applications. Additionally, these compositions require higher loading to achieve comparable curing speeds, and they can result in post-cure yellowing.
Innovation Solution
The use of multifunctional halogenated thioxanthones as photosensitizers in UV-curable compositions, in combination with cationically polymerizable components and iodonium salt photoinitiators, allows for comparable curing speeds to monofunctional CPTX at the same weight percentage, while reducing post-cure yellowing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If monofunctional thioxanthones are used as photosensitizers, then curing speed can be achieved, but reproductive toxicity and migration occur
Solution Approach 1:
The patent changes the chemical parameters of the thioxanthone photosensitizer by introducing multiple functional groups and halogen atoms. This transforms the molecular structure from monofunctional to multifunctional, which fundamentally alters the compound's properties including reduced toxicity and migration while maintaining or improving photosensitizing efficiency.
Solution Approach 2:
The patent creates a composite photosensitizer system by combining multiple thioxanthone functional groups and halogen atoms within a single molecular structure. This composite approach at the molecular level achieves both the desired safety profile (reduced toxicity and migration) and the required performance (curing speed).
2Object-affected harmful factors
If multifunctional thioxanthones are used as photosensitizers, then toxicity and migration are reduced, but curing speed decreases
Solution Approach 1:
The patent optimizes the photosensitizing parameters by introducing halogen atoms (such as chlorine or bromine) at specific positions on the thioxanthone core. This parameter change enhances the compound's ability to absorb light and transfer energy to the photoinitiator, thereby increasing curing speed while maintaining the safety benefits of the multifunctional structure.
Solution Approach 2:
The patent applies local quality enhancement by strategically placing halogen atoms at specific positions on the thioxanthone molecule. This localized modification optimizes the photosensitizing activity at key sites while preserving the overall multifunctional structure that provides reduced toxicity and migration.
3Productivity
If monofunctional thioxanthones are used as photosensitizers, then curing can be achieved, but post-cure yellowing occurs
Solution Approach 1:
The patent modifies the chemical parameters of the thioxanthone photosensitizer by adding multiple functional groups and halogen atoms, which changes the photostability and chemical reactivity of the compound. This parameter change reduces the tendency for post-cure yellowing while maintaining effective curing capability.
Solution Approach 2:
The patent converts the potential harm of yellowing into a benefit by designing a multifunctional halogenated thioxanthone structure that is inherently more photostable. The additional functional groups and halogen atoms provide alternative pathways for energy dissipation that prevent the formation of yellowing byproducts.
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
Multifunctional halogenated thioxanthones enable faster curing speeds and reduced yellowing in UV-curable compositions, addressing toxicity and migration concerns and optimizing formulation efficiency.
Implementation Method 1
Photo-induced polymerization has been widely used for about 50 years... cationically UV-initiated photo-polymerization was preferred to free-radical photo-polymerization
Implementation Method 2
onium salts initiators have poor absorption at wavelengths above 350 nm. It was thus necessary to use photosensitizers such as anthracene compounds, benzophenones or thioxanthones (TX) to expand the spectra region
Data Source
Figure 1~2
Figure 3~4
AI summary
The present invention relates to a curable composition comprising: a) a cationically polymerizable component, b) a cationic photoinitiator component comprising at least one iodonium salt, c) a photosensitizer component comprising at least one multifunctional halogenated thioxanthone. It further relates to processes for curing such compositions, cured products thus obtained and uses of such products.