Thermoplastic Polyurethane UV Stabilization
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Solution Overview
Problem
Existing thermoplastic polyurethanes used in eyewear applications suffer from high initial yellowness index and instability when exposed to UV light, which affects their optical clarity and longevity.
Innovation Solution
A method of converting a polymerizable composition into thermoplastic polyurethane using a specific combination of antioxidants and light stabilizers, including benzenepropanoic acid, bis(1,2,2,6,6-pentamethyl-4-piperidinyl)-[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]butylmalonate, and phenol derivatives, which are incorporated during the polymerization process to enhance UV stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional thermoplastic polyurethane is used in eyewear applications, then high toughness and chemical resistance are achieved, but high initial yellowness index and UV light instability occur
Solution Approach 1:
The patent applies composite materials by combining thermoplastic polyurethane with specific stabilizer compounds (Irganox 245, Tinuvin 144, and Tinuvin 326 or 360) to create a composite polymer system. This combination provides both the mechanical properties of TPU and the UV protection of the stabilizer blend, resolving the contradiction between toughness and UV stability.
Solution Approach 2:
The patent changes the chemical composition parameters of the polyurethane by incorporating specific stabilizers at defined concentrations (0.05-1.0 wt% for Irganox 245, 0.05-1.0 wt% for Tinuvin 144, and 0.05-1.0 wt% for Tinuvin 326 or 360). This parameter modification transforms the material's UV resistance properties while maintaining its mechanical integrity.
2Stability of the object's composition
If thermoplastic polyurethane is used for eyewear lenses, then optical clarity is required, but color stability under UV exposure deteriorates
Solution Approach 1:
The stabilizer compounds act as intermediary substances between the UV light and the polyurethane matrix. These intermediaries (Irganox 245, Tinuvin 144, Tinuvin 326/360) absorb or scavenge UV radiation before it can degrade the polyurethane, thereby protecting the material's color stability while allowing optical clarity to be maintained.
3Reliability
If existing UV stabilizing additive blends are used, then some UV protection is achieved, but insufficient protection against yellowing over time occurs
Solution Approach 1:
The patent merges multiple stabilizer mechanisms into a single blend system: Irganox 245 (hindered phenolic antioxidant), Tinuvin 144 (HALS), and Tinuvin 326/360 (UVA absorbers). This combination provides synergistic protection that addresses both immediate UV protection and long-term color stability, overcoming the limitations of single-additive systems.
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 method results in thermoplastic polyurethane with improved UV stability, maintaining a low yellowness index and preventing significant color change over time, even after 200 hours of simulated sunlight exposure, outperforming other commercially available UV stabilizing additive blends.
Implementation Method 1
the antioxidant is benzenepropanoic acid, 3(1,1-dimethylethyl)-4-hydroxy-5-methyl-1,1′-[1,2-ethanediylbis(oxy-2,1-ethanediyl)]ester
Implementation Method 2
the light stabilizer is bis(1,2,2,6,6-pentamethyl-4-piperidinyl)-[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]butylmalonate together with at least one component selected from the group of phenol, 2-(5-chloro-2H-benzotriazole-2-yl)-6-(1,1-dimethylethyl)-4-methyl and 2,2′-methylenebis(6-(2H-benzotriazol-2-yl)-4-1,1,3,3-tetramethylbutyl)phenol)
Data Source
AI summary
Method of producing a thermoplastic polyurethane having a light stabilization useful for ophthalmic applications, comprising combining precursors of a polyurethane and at least one antioxidant, and incorporating therein, either before, during or after polymerization, at least one light stabilizer, said method being characterized in that the antioxidant is benzenepropanoic acid, 3(1,1-dimethylethyl)-4-hydroxy-5-methyl-1,1′-[1,2-ethanediylbis(oxy-2,1-ethanediyl)]ester and the light stabilizer is bis(1,2,2,6,6-pentamethyl-4-piperidinyl)-[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]butylmalonate together with at least one additional component chosen from among phenol, 2-(5-chloro-2H-benzotriazole-2-yl)-6-(1,1-dimethylethyl)-4-methyl and 2,2′-methylenebis(6-(2H-benzotriazol-2-yl)-4-1,1,3,3-tetramethylbutyl)phenol).