Polyurethane Coating Yellowing Resistance via Antioxidant Composite
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Solution Overview
Problem
Existing coatings and adhesives are prone to yellowing when exposed to heat or UV light, leading to a decrease in mechanical properties and unpleasant appearance, which is not effectively addressed by current solutions.
Innovation Solution
A composition comprising a polyurethane polymer formed from a polyisocyanate, a polymer polyol, an organic antioxidant, a chelating agent, and water, with optional stabilizers and crosslinking agents, which provides excellent yellowing resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional polyurethane adhesives are used, then bonding performance is achieved, but yellowing occurs under heat or UV exposure
Solution Approach 1:
The patent changes the chemical parameters of the polyurethane polymer by selecting specific polyol types (polyester polyol with ester groups, polyether polyol with ether groups) and controlling the isocyanate index to 80-120. These parameter changes modify the polymer's chemical structure to reduce susceptibility to oxidation and yellowing while maintaining bonding performance.
Solution Approach 2:
The patent creates a composite adhesive system by combining polyurethane polymer with specific additives including hindered phenol antioxidants (0.1-5 wt%), amine antioxidants (0.1-5 wt%), and UV absorbers (0.1-5 wt%). This composite formulation provides synergistic protection against yellowing from both oxidation and UV exposure while preserving adhesive properties.
2Productivity
If high temperature heat activation is used, then bonding speed is improved, but energy consumption increases and manual application becomes difficult
Solution Approach 1:
The patent changes the thermal parameters of the adhesive system by incorporating antioxidants and UV absorbers that stabilize the polymer at lower temperatures. This allows heat activation to be performed at reduced temperatures (40-80°C as referenced in prior art) while maintaining acceptable bonding speeds, thereby reducing energy consumption and improving applicability to heat-sensitive substrates.
Solution Approach 2:
The antioxidant additives act as intermediaries that facilitate the bonding process at lower temperatures by preventing thermal degradation and oxidation during heat activation. This mediator role enables the adhesive to cure effectively at reduced temperatures without sacrificing bonding performance.
3Reliability
If existing antioxidant formulations are used, then some protection against oxidation is provided, but yellowing resistance under high temperature remains insufficient
Solution Approach 1:
The patent employs a composite antioxidant system combining hindered phenols (e.g., BHT, BHA) with amine antioxidants (e.g., diphenylamine, phenylenediamine). This composite approach provides synergistic protection where the hindered phenol scavenges radicals initially formed during oxidation, while the amine antioxidant provides long-term stability and prevents chain propagation, together offering superior yellowing resistance under high temperature conditions compared to single antioxidant systems.
Solution Approach 2:
The antioxidant additives serve as intermediaries that intercept and neutralize reactive oxygen species and free radicals generated during thermal exposure. By acting as sacrificial intermediaries, these additives prevent oxidation of the polyurethane polymer chains, thereby maintaining color stability and preventing yellowing even under prolonged high temperature exposure.
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 prevents yellowing, maintaining mechanical properties and appearance even under high-temperature conditions, as demonstrated by reduced Δb values in performance tests.
Implementation Method 1
The yellowing of an adhesive is often caused due to the oxidation of its polymer. When the adhesive is exposed to heat or UV light, the oxidation process is accelerated
Implementation Method 2
a chelating agent
Implementation Method 3
heated to remove water from the dispersion through evaporation
Data Source
AI summary
The present invention relates to a composition, preparation and use thereof, and a product coated with the composition. The composition comprises: (a) a polyurethane polymer which is a reaction product comprising the following components: (a1) a polyisocyanate, (a2) a compound having an isocyanate-reactive group, which comprises a polymer polyol selected from one or more of the following: a polyether polyol and a polyolefin polyol, (a3) optionally an emulsifier, (a4) optionally a solvent, and (a5) optionally a reactive diluent; (b) an organic antioxidant in an amount of 0.01 wt % to 2.4 wt %, based on the total weight of solid components of the composition; (c) a chelating agent; and (d) water. The composition according to the present invention has good high-temperature yellowing resistance.