TMCD Polyester Composition Balancing Tg, Impact, and Processability
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Solution Overview
Problem
Current polyester compositions based on terephthalic acid, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, and 1,4-cyclohexanedimethanol face challenges in achieving a balance of high impact strength, hydrolytic stability, chemical resistance, and processability while maintaining low ductile-to-brittle transition temperatures and good color and clarity, with existing polymers like polycarbonate offering poor chemical resistance and melt processability.
Innovation Solution
A polyester composition comprising 70 to 100 mole % terephthalic acid residues, 0 to 30 mole % aromatic dicarboxylic acid residues, and 0 to 10 mole % aliphatic dicarboxylic acid residues, combined with 1 to 99 mole % 2,2,4,4-tetramethyl-1,3-cyclobutanediol residues and 1 to 99 mole % 1,4-cyclohexanedimethanol residues, with specific inherent viscosity and glass transition temperature ranges, allowing for improved processability and performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If sufficient ethylene glycol is included in the formulation to provide long crystallization half-times, then amorphous products can be obtained, but the glass transition temperature decreases and impact strength deteriorates
Solution Approach 1:
The patent changes the chemical composition parameters by substituting ethylene glycol with 2,2,4,4-tetramethyl-1,3-cyclobutanediol (TMCD). This substitution fundamentally alters the polymer's glass transition temperature and crystallization behavior, allowing long crystallization half-times to be achieved without the detrimental effects of low Tg and poor impact strength that occur with ethylene glycol modification.
Solution Approach 2:
The patent creates a composite polyester system combining terephthalic acid, 1,4-cyclohexanedimethanol, and 2,2,4,4-tetramethyl-1,3-cyclobutanediol. This composite approach leverages the complementary properties of each component: TPA provides structural rigidity, CHDM contributes to chemical resistance and hydrolytic stability, and TMCD extends crystallization half-time while maintaining high impact strength and appropriate Tg.
2Loss of time
If 2,2,4,4-tetramethyl-1,3-cyclobutanediol is used to extend crystallization half-time, then high inherent viscosity and high Tg are achieved, but melt processability deteriorates
Solution Approach 1:
The patent optimizes the TMCD content parameter within a specific range (1-99 mole %) to balance the competing requirements. By controlling the concentration of TMCD alongside CHDM, the formulation achieves sufficient crystallization half-time extension and high Tg while maintaining melt viscosity at levels acceptable for standard industrial processing equipment.
3Temperature
If polycarbonate is used as an alternative to polyester, then high heat resistance and impact strength are achieved, but chemical resistance and melt processability deteriorate
Solution Approach 1:
The patent develops a polyester composite system that combines the heat resistance and impact strength typically associated with polycarbonate with the superior chemical resistance and hydrolytic stability inherent to polyester structures. The specific combination of TPA, CHDM, and TMCD creates a material that matches or exceeds polycarbonate performance in mechanical properties while maintaining excellent chemical resistance.
Data Source
AI summary
Described are polyester compositions comprising at least one polyester which comprises terephthalic acid residues, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, and 1,4-cyclohexanedimethanol, wherein the inherent viscosity and the Tg of the polyester provides for certain polyester properties. The polyesters may be manufactured into articles such as fibers, films, bottles or sheets.