Aliphatic Polyether Urethane Acrylate Composition UV Yellowing
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Solution Overview
Problem
Current photosensitive compositions used for making relief printing plates, such as hand stamps, suffer from yellowing when exposed to ultraviolet light or sunlight, affecting their clarity and stability over time.
Innovation Solution
A novel photosensitive resin composition comprising aliphatic polyether urethane (meth)acrylate oligomers, reactive diluents, and a specific photoinitiator, along with additives like stabilizers and antioxidants, is developed to reduce yellowing, maintaining clarity even after exposure to UV-light or sunlight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional photosensitive compositions are used to make relief printing plates, then the plates can be produced with adequate softness and chemical resistance, but the plates suffer from yellowing upon exposure to ultraviolet light and sunlight, affecting clarity
Solution Approach 1:
The patent changes the chemical parameters of the photosensitive composition by using aliphatic polyether urethane (meth)acrylate oligomers instead of conventional aromatic or vinyl-based oligomers. This parameter change in molecular structure eliminates the chromophoric groups that cause yellowing, while maintaining the desired softness and chemical resistance properties of the cured printing plates.
Solution Approach 2:
The patent employs a composite material system combining aliphatic polyether urethane (meth)acrylate oligomers with specific photoinitiators and stabilizers. This composite approach creates a synergistic effect where the aliphatic structure provides yellowing resistance, the polyether backbone maintains flexibility, and the urethane groups contribute to chemical resistance, collectively solving the contradiction between clarity stability and mechanical properties.
2Stability of the object's composition
If the composition maintains transparency for packaged life, then the hand stamp material should be substantially transparent, but current compositions yellow upon exposure to actinic light over time
Solution Approach 1:
The patent extracts and eliminates the harmful aromatic and vinyl groups from the oligomer structure, retaining only the beneficial aliphatic polyether urethane backbone. This extraction of problematic chromophoric components prevents yellowing during storage and extended exposure to actinic light, maintaining transparency stability throughout the packaged life and beyond.
Solution Approach 2:
The patent performs preliminary stabilization by incorporating UV absorbers and antioxidants into the composition formulation before curing. These additives are pre-positioned to protect the aliphatic polyether urethane oligomers from degradation during storage and initial exposure, ensuring transparency stability is maintained throughout the intended storage duration and early service life.
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 effectively minimizes yellowing in cured articles, ensuring the clarity and stability of printing plates and hand stamps, as demonstrated by reduced yellowness index values after exposure to UV-light and sunlight.
Implementation Method 1
a layer of polymerizable composition is supported on a suitable support, and exposure of the composition is continued until substantial polymerization of the composition has occurred in the exposed areas
Implementation Method 2
containing an addition polymerizable, ethylenically unsaturated monomer and an addition polymerization initiator activated by actinic light
Data Source
AI summary
This disclosure relates to a photosensitive composition useful in preparing water-developable, relief printing plates and other photosensitive articles. The compositions comprise an unsaturated polyurethane pre-polymer, which is the reaction product of at least one polyether diol, at least one aliphatic diisocyanate, at least one hydroxyl-functionalized mono-, di- and tri-(meth)acrylate, and a particular photoinitiator. The resulting photosensitive resin compositions have reduced rates and levels of yellowing if subjected to additional UV-light or sunlight after processing.