TMCD Polyester Composition for Amorphous Tough Heat-Resistant Articles
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Solution Overview
Problem
Current polyester compositions, such as poly(1,4-cyclohexylenedimethylene terephthalate) and ethylene glycol-modified copolyesters, face challenges in achieving a balance of high impact strength, moderate glass transition temperature, and long crystallization half-times while maintaining processability and chemical resistance, with existing polymers like bisphenol A polycarbonate exhibiting poor melt processability and chemical resistance.
Innovation Solution
A polyester composition comprising terephthalic acid, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, and 1,4-cyclohexanedimethanol with specific mole percentages and inherent viscosities, which allows for the production of films and molded articles with improved toughness, heat resistance, and reduced ductile-to-brittle transition temperatures, while being processable on standard equipment.
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 replacing ethylene glycol with 2,2,4,4-tetramethyl-1,3-cyclobutanediol (TMCD) in the polyester formulation. This substitution fundamentally alters the polymer's glass transition temperature and crystallization behavior, achieving long crystallization half-times without the detrimental effects on impact strength and Tg observed with ethylene glycol modification.
Solution Approach 2:
The patent uses a copolymer composition that combines PCT segments with TMCD-containing segments to create a material that achieves the desired amorphous properties and processing characteristics without requiring the harmful levels of ethylene glycol modification. The copolymer structure allows short PCT segments to provide chemical resistance while TMCD segments provide the necessary amorphous character.
2Strength
If 2,2,4,4-tetramethyl-1,3-cyclobutanediol is used to achieve moderate glass transition temperature and long crystallization half-times, then impact strength improves, but inherent viscosity and melt viscosity increase excessively
Solution Approach 1:
The patent optimizes the TMCD content parameter within a specific range (1-50 mole percent of total diol content) to balance the competing requirements. At these controlled levels, the TMCD provides improved impact strength and crystallization half-time while keeping the inherent viscosity and melt viscosity within acceptable ranges for standard processing equipment.
Solution Approach 2:
The patent creates a composite polyester structure combining PCT segments with TMCD-modified segments. This composite approach allows the material to exhibit both the high impact strength and long crystallization half-times associated with TMCD while maintaining processability through the balanced copolymer composition and controlled inherent viscosity.
3Reliability
If PCT crystallizes rapidly upon cooling from the melt, then high chemical resistance is achieved, but it becomes very difficult to form amorphous articles
Solution Approach 1:
The patent segments the polyester chain into alternating PCT units and TMCD-containing units. The PCT segments provide chemical resistance through their crystalline character, while the TMCD segments introduce irregularities that slow crystallization and enable amorphous formation. This segmentation allows both properties to coexist in the final material.
Solution Approach 2:
The TMCD units act as intermediaries that modify the crystallization behavior of the PCT backbone. They interfere with the rapid crystallization of pure PCT, providing a kinetic barrier that allows amorphous articles to be formed while the PCT segments maintain the chemical resistance properties.
4Strength
If bisphenol A polycarbonate is used to achieve high impact strength and heat resistance, then good physical properties are obtained, but melt viscosity becomes too high for standard processing equipment
Solution Approach 1:
The patent uses a polyester copolymer with controlled TMCD content as a substitute for bisphenol A polycarbonate. This polyester composition achieves comparable impact strength and heat resistance but with significantly lower melt viscosity, making it suitable for standard processing equipment without requiring specialized high-viscosity processing systems.
Data Source
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AI summary
Described are polyesters comprising (a) a dicarboxylic acid component comprising terephthalic acid residues; optionally, aromatic dicarboxylic acid residues or aliphatic dicarboxylic acid residues; 2,2,4,4-tetramethyl-1,3-cyclobutanediol residues; and 1,4-cyclohexanedimethanol residues. The polyesters may be manufactured into articles such as fibers, films, bottles or sheets.