Long-Chain Aliphatic Polyester Coatings for UV Stability and Hardness
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Solution Overview
Problem
Conventional polyester-based coating compositions often lack sufficient UV stability, gloss retention, hardness, adhesion, chemical resistance, and impact resistance, particularly when using aromatic carboxylic acids, which can compromise these properties while trying to maintain coating hardness.
Innovation Solution
Incorporating a linear aliphatic dicarboxylic acid with 16 to 30 carbon atoms as a replacement for aromatic carboxylic acids or anhydrides in the polyester composition, enhancing UV resistance and stability without significantly reducing the hardness of the cured coating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If aromatic carboxylic acids are used in polyester to maintain coating hardness, then coating hardness is improved, but UV stability and resistance deteriorate
Solution Approach 1:
The patent changes the chemical structure parameter of the dicarboxylic acid from aromatic (e.g., isophthalic acid) to aliphatic with long carbon chain (C16-C30). This structural parameter change maintains the rigidity needed for hardness while eliminating the UV instability of aromatic rings, achieving both hardness and UV resistance simultaneously
Solution Approach 2:
The patent creates a composite polyester structure by combining long-chain aliphatic dicarboxylic acid (for UV stability) with aromatic dicarboxylic acid (for hardness) in specific ratios. This composite approach allows the polyester to exhibit both UV resistance and coating hardness properties that neither component alone could achieve optimally
2Strength
If aromatic carboxylic acids are used in polyester, then coating hardness is maintained, but gloss retention deteriorates
Solution Approach 1:
The patent modifies the chemical composition parameter by replacing aromatic dicarboxylic acid with long-chain aliphatic dicarboxylic acid (C16-C30). This change preserves the molecular rigidity necessary for hardness while eliminating the yellowing and gloss loss associated with aromatic ring degradation under UV exposure, thereby maintaining gloss retention
3Strength
If aromatic carboxylic acids are used in polyester, then coating hardness is improved, but adhesion deteriorates
Solution Approach 1:
The patent formulates a composite polyester system where long-chain aliphatic dicarboxylic acid provides flexibility and adhesion through its aliphatic structure, while controlled amounts of aromatic dicarboxylic acid contribute to hardness. This composite structure achieves both good adhesion and coating hardness that cannot be obtained with purely aromatic polyesters
4Strength
If aromatic carboxylic acids are used in polyester, then coating hardness is maintained, but chemical resistance deteriorates
Solution Approach 1:
The patent changes the chemical composition parameter by substituting aromatic dicarboxylic acid with long-chain aliphatic dicarboxylic acid (C16-C30). This structural change provides enhanced chemical resistance through the saturated aliphatic chain structure that is more resistant to chemical attack, while maintaining coating hardness through the long-chain molecular rigidity
Data Source
AI summary
The present invention provides a polyester which is the reaction product of reactants comprising: (A) an aliphatic dicarboxylic acid comprising from 16 to 30 carbon atoms; (B) an aromatic carboxylic acid and/or anhydride; and (C) a polyol. The invention also provides a coating composition comprising the polyester, a method of making the coating composition and the use of at least 2 wt% of a linear aliphatic dicarboxylic acid comprising from 16 to 30 carbon atoms as a replacement for at least 2 wt% of an aromatic carboxylic acid and/or anhydride in a polyester composition. This use may improve the UV resistance and/or stability of the polyester composition.