Copolyesterimide Tg Enhancement via BTDI Comonomer
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Solution Overview
Problem
Current polyesters face challenges in increasing glass transition temperature (Tg) without significantly raising crystalline melting point (Tm) or decreasing crystallinity, which affects their melt-processability and thermo-mechanical stability, especially for semi-crystalline materials like PET and PEN.
Innovation Solution
Incorporating N,N′-bis-(hydroxyalkyl)-benzophenone-3,3′,4,4′-tetracarboxylic diimide (BTDI) as a comonomer into polyesters, specifically in the glycol fraction, to enhance Tg while maintaining Tm and crystallinity, allowing for high molecular weight and melt-processability below 320°C.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If more rigid comonomers are introduced to enhance Tg, then Tg increases, but Tm and degree of crystallinity decrease
Solution Approach 1:
The patent applies parameter changes by carefully controlling the comonomer content within specific ranges (0.1-10 mol% for comonomer A, 0.1-5 mol% for comonomer B) to achieve the desired balance between Tg enhancement and crystallinity retention. By adjusting these compositional parameters, the invention optimizes the polymer structure to simultaneously improve heat resistance and maintain crystalline stability.
Solution Approach 2:
The invention uses composite material principles by creating copolymer compositions containing multiple comonomers (comonomer A and comonomer B) with different functionalities. This multi-component system allows the rigid comonomers to enhance Tg while the specific combination and ratios maintain adequate crystallinity, achieving properties that neither single-component system could provide alone.
2Temperature
If Tm is increased to improve heat resistance, then heat resistance improves, but melt-processability deteriorates
Solution Approach 1:
The patent applies parameter changes by controlling the comonomer composition and content to achieve an optimal balance between Tm and processability. The specific compositional ranges defined in the invention allow the polymer to maintain adequate heat resistance while ensuring melt-processability at economically viable temperatures below 320°C.
3Temperature
If comonomers are introduced to increase Tg while retaining Tm, then Tg increases and Tm is retained, but decomposition temperature converges with Tm leading to degradation products
Solution Approach 1:
The patent applies parameter changes by carefully controlling the types and amounts of comonomers to achieve the desired Tg enhancement while maintaining a safe margin between Tm and decomposition temperature. The specific compositional parameters defined in the invention prevent the convergence of Tm and decomposition temperature that would lead to degradation.
Data Source
AI summary
A copolyester includes repeating units derived from an aliphatic glycol, terephthalic acid, and the monomer of formula (I):wherein n=2, 3 or 4; Z is C═O; comonomer (I) constitutes a proportion of the glycol fraction of the copolyester and is present in a range of from about 5 to about 15 mol % of the glycol fraction of the copolyester; wherein said copolyester is semi-crystalline. A process tor making the copolyester includes annealing a copolyester of formula (I) at 20-80° C. below the crystalline melting point (Tm) and above the glass transition temperature (Tg).