Yellowing Resistant Pressure Sensitive Adhesive Formulation
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Solution Overview
Problem
Conventional pressure-sensitive adhesives (PSAs) exhibit inadequate yellowing resistance when exposed to heat and UV radiation, which is undesirable in applications requiring transparency and visibility, such as automotive windows.
Innovation Solution
A PSA comprising a polyacrylate base polymer, a crosslinker that does not include metal acetylacetonate, metal alkoxide, or alkoxy-metal acetylacetonate, and a fluorescer with less than 0.1 wt.% metal oxide, specifically using benzoxazole or biphenyl derivatives with vinyl groups, which enhances yellowing resistance while maintaining mechanical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional PSAs are used, then they provide good mechanical features and adhesiveness, but they exhibit poor yellowing resistance when exposed to heat and UV radiation
Solution Approach 1:
The patent changes the chemical composition parameters of the PSA by incorporating specific antioxidants (e.g., hindered phenols, hindered amine light stabilizers) and UV absorbers (e.g., benzotriazoles, benzophenones) into the adhesive formulation. These additives modify the chemical stability parameters of the PSA, enabling it to resist yellowing when exposed to heat and UV radiation while maintaining its mechanical properties and adhesiveness.
2Reliability
If special polyacrylate base polymer is used to improve yellowing resistance, then yellowing resistance is enhanced, but the cost increases and the result is often not satisfactory
Solution Approach 1:
The patent creates a composite adhesive system by combining a standard polyacrylate base polymer with specific concentrations of antioxidants and UV absorbers. This composite formulation achieves superior yellowing resistance without requiring expensive special polyacrylate base polymers. The synergistic effect of the additive package with the conventional polymer provides cost-effective protection against heat and UV-induced yellowing.
3Strength
If PSAs are used in automotive applications, then they provide excellent mechanical features, but they change color under high temperature and UV radiation conditions
Solution Approach 1:
The patent introduces antioxidants and UV absorbers as intermediary substances that mediate between the PSA and harmful environmental factors (heat and UV radiation). These intermediaries absorb or neutralize the damaging effects of UV radiation and heat before they can cause yellowing of the adhesive, while allowing the PSA to maintain its mechanical strength and bonding properties in automotive applications.
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 PSA demonstrates superior yellowing resistance with Δb values less than 1.3 and Δe values less than 2.1 when exposed to high temperatures or UV light, along with high peel strength, effectively preventing color change and maintaining transparency.
Implementation Method 1
a fluorescer, wherein the fluorescer comprises less than 0.1 wt. % metal oxide based on the solid weight of the adhesive
Data Source
AI summary
Provided herein is a pressure sensitive adhesive (PSA) comprising a polycrylate base polymer, a crosslinker and a fluorescer. The crosslinker does not comprise a metal acetylacetonate, a metal alkoxide, or an alkoxy-metal acetylacetonate, and the fluorescer comprises less than 0.1 wt. % metal oxide based on the solid weight of the adhesive. The adhesive is resistant to yellowing under adverse conditions such as high temperature treatment and/or exposure to UV.