Thermoplastic Polyester Composition for Injection Molding
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Solution Overview
Problem
Current thermoplastic polyesters, such as those based on isosorbide, face challenges with insufficient impact resistance and glass transition temperature, making them unsuitable for certain applications, particularly in the manufacture of injected parts where improved thermal and mechanical properties are required.
Innovation Solution
A thermoplastic polyester composition comprising 1,4:3,6-dianhydrohexitol units, alicyclic diol units, and terephthalic acid units, with a specific molar ratio and reduced viscosity, is developed, eliminating the need for non-cyclic aliphatic diol units like ethylene glycol, thereby enhancing mechanical and thermal properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If isosorbide-based polyesters are used to improve glass transition temperature, then thermal resistance is improved, but impact resistance becomes insufficient
Solution Approach 1:
The patent changes the chemical composition parameters by introducing 1,4:3,6-dianhydrohexitol motifs (specifically isosorbide) at controlled molar ratios (5-60%) into the polyester structure. This parameter change simultaneously achieves higher glass transition temperatures (improving thermal resistance) while maintaining adequate impact resistance through optimal composition control, resolving the contradiction between thermal and mechanical properties.
Solution Approach 2:
The patent creates a composite polyester structure by combining multiple diol components (ethylene glycol, 1,4-cyclohexanedimethanol, and isosorbide) with terephthalic acid units. This composite approach allows the material to exhibit both the high thermal resistance from isosorbide units and the mechanical toughness from the synergistic combination of diol components, overcoming the limitation of single-component polyesters.
2Strength
If 1,4-cyclohexanedimethanol is added to eliminate crystallinity and improve impact resistance, then impact resistance is improved, but glass transition temperature becomes too low for certain applications
Solution Approach 1:
The patent adjusts the molar ratio parameters of diol components, specifically limiting 1,4-cyclohexanedimethanol to 40-95% of total diols while incorporating 5-60% isosorbide. This parameter optimization ensures the polyester remains amorphous (maintaining impact resistance) while achieving sufficient glass transition temperature through the thermal contribution of isosorbide units, thus resolving the temperature-strength trade-off.
3Ease of manufacture
If ethylene glycol is used as chain linker to facilitate polymerization, then manufacturing is simplified, but thermal properties and mechanical properties are compromised
Solution Approach 1:
The patent applies local quality by using ethylene glycol selectively as a chain linker (5-40% of total diols) rather than as the primary diol component. This localized use maintains polymerization processability and molecular weight buildup while limiting the overall impact on thermal properties. The bulk of the polyester structure consists of other diols (1,4-cyclohexanedimethanol and isosorbide) that provide the desired thermal and mechanical properties, thus resolving the contradiction between manufacturability and performance.
Data Source
AI summary
Use of a thermoplastic polyester for producing injected parts, said polyester having at least one 1,4:3,6-dianhydrohexitol unit (A), at least one alicyclic diol unit (B) other than the 1,4:3,6-dianhydrohexitol units (A), and at least one terephthalic acid unit (C), wherein the molar ratio (A)/[(A)+(B)] is at least 0.05 and at most 0.75, said polyester being free of non-cyclic aliphatic diol units or comprising a molar amount of non-cyclic aliphatic diol units, relative to the totality of monomeric units in the polyester, of less than 5%, and with a reduced viscosity in solution (25°C; phenol (50 wt.%): ortho-dichlorobenzene (50 wt.%); 5 g/L of polyester) greater than 50 mL/g.