Mixed Aliphatic-Aromatic Polyester Composition With Low Tg and Fewer Oligomers
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Solution Overview
Problem
Existing biodegradable aliphatic-aromatic polyesters face challenges in achieving a low glass transition temperature (Tg) and high flexibility while minimizing residual cyclic oligomers that affect mechanical and transparency properties.
Innovation Solution
A process involving esterification and polycondensation with specific catalysts and phosphorus-containing compounds controls the amount of residual mixed cyclic oligomers, using a dicarboxylic component comprising saturated aliphatic and aromatic acids, and a diol component to produce mixed aliphatic-aromatic polyesters with controlled oligomer content and improved Tg.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional esterification and polycondensation processes are used, then polyester production is achieved, but residual cyclic oligomers remain trapped within the polyester affecting mechanical performance and transparency
Solution Approach 1:
The patent applies parameter changes by modifying the polycondensation conditions including temperature (200-260°C), pressure (0.1-100 mbar), and time (2-10 hours) to optimize the removal of cyclic oligomers while maintaining polyester quality. The use of specific catalyst concentrations (10-1000 ppm Ti, 10-500 ppm Zr) and vacuum distillation parameters enables selective removal of oligomers with molecular weights below 1000 Da
Solution Approach 2:
The patent employs extraction principles through vacuum distillation to separate and remove residual cyclic oligomers from the polyester matrix. The process extracts volatile oligomeric species by applying reduced pressure during polycondensation, allowing them to be removed as vapor while the polymer remains in the reactor
2Strength
If aromatic acid content is increased to improve mechanical properties, then strength is improved, but glass transition temperature increases reducing flexibility
Solution Approach 1:
The patent utilizes parameter changes by precisely controlling the aromatic acid content within 40-70 mol% of total dicarboxylic acid content. This optimized composition range balances the competing requirements of mechanical strength (improved by aromatic content) and flexibility (maintained by limiting Tg increase), achieving a synergistic effect not obtainable with extreme compositions
3Temperature
If long-chain dicarboxylic acids are used to improve flexibility and lower Tg, then chain flexibility is improved, but crystallisation behavior becomes difficult to control
Solution Approach 1:
The patent applies composite material principles by creating a multi-component dicarboxylic acid system comprising at least three different saturated aliphatic dicarboxylic acids (including azelaic and succinic acids) combined with aromatic acids. This composite composition achieves flexible Tg control through long-chain acids while the diverse acid mixture prevents excessive crystallinity, balancing flexibility with compositional stability
4Speed
If polycondensation is carried out with standard catalysts, then reaction speed is improved, but residual mixed cyclic oligomer formation increases
Solution Approach 1:
The patent applies parameter changes by optimizing catalyst concentrations (Ti: 10-1000 ppm, Zr: 10-500 ppm) and reaction conditions (temperature, pressure, time) to minimize cyclic oligomer formation. The specific Ti/(Ti+Zr) ratio control enables selective catalysis that promotes linear chain growth over cyclic oligomerization, reducing harmful byproducts while maintaining reaction efficiency
Solution Approach 2:
The patent employs intermediary principles by using a dual-catalyst system where Titanium and Zirconium compounds work synergistically. This catalyst combination mediates the polycondensation reaction to favor linear polyester formation while suppressing cyclic oligomerization pathways, with each catalyst contributing different selectivity characteristics
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 solution achieves mixed aliphatic-aromatic polyesters with reduced residual cyclic oligomers, lower Tg, and enhanced mechanical properties, suitable for film production with improved flexibility and transparency.
Implementation Method 1
WO2016/050963 describes a combined process for the production of polyesters comprising an esterification or transesterification step and a subsequent polycondensation step, characterised in that said polycondensation step is carried out in the presence of a catalyst comprising a mixture of at least one compound comprising Titanium and at least one compound comprising Zirconium
Implementation Method 2
by appropriately selecting the conditions of the process described in patent application WO2016/050963, in particular through additions of phosphorus-containing compounds in appropriate amounts relative to the catalyst used, together with specific temperature and pressure conditions, mixed aliphatic-aromatic polyesters with a controlled amount of residual mixed cyclic oligomers can be obtained
Implementation Method 3
These residual cyclic oligomers are partly removed by distillation during the polycondensation step
Implementation Method 4
WO2016/050963 describes a combined process for the production of polyesters comprising an esterification or transesterification step and a subsequent polycondensation step
Data Source
AI summary
Mixed aliphatic-aromatic polyesters having suitable thermal properties and terminal acidity characterised by having a dicarboxylic component comprising at least three saturated aliphatic C4-C24 dicarboxylic acids, their C1-C24 alkyl esters, their salts and their mixtures, azelaic acid and succinic acid always being present.