Cyclobutanediol Copolyester Composition for Amorphous Thermoforming
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Solution Overview
Problem
Current polyester compositions based on terephthalic acid, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, and cyclohexanedimethanol face challenges in achieving a balance of high impact strength, moderate glass transition temperature, chemical resistance, and processability while maintaining thermoformability and avoiding rapid crystallization, which limits their application in forming amorphous articles.
Innovation Solution
A polyester composition comprising 70 to 100 mole % terephthalic acid residues, 0 to 30 mole % aromatic dicarboxylic acid residues, and 1 to 99 mole % 2,2,4,4-tetramethyl-1,3-cyclobutanediol residues, with cyclohexanedimethanol as the glycol component, having inherent viscosities between 0.35 to 1.2 dL/g and glass transition temperatures ranging from 85 to 120°C, allowing for improved processability and thermoformability on standard equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sufficient ethylene glycol is included in the formulation to provide long crystallization half-times, then amorphous products can be formed, but glass transition temperature and impact strength decrease
Solution Approach 1:
The patent changes the chemical composition parameters by replacing ethylene glycol with 2,2,4,4-tetramethyl-1,3-cyclobutanediol (CBT) and adjusting the molar ratios of terephthalic acid, CBT, and cyclohexanedimethanol to achieve the desired balance between crystallization half-time and impact strength
Solution Approach 2:
The patent creates a copolyester composite material combining multiple glycol components (CBT and cyclohexanedimethanol) with terephthalic acid to achieve synergistic effects that simultaneously improve impact strength and control crystallization behavior
2Strength
If 2,2,4,4-tetramethyl-1,3-cyclobutanediol is used to improve impact strength and moderate glass transition temperature, then processability improves, but inherent viscosity and melt viscosity increase
Solution Approach 1:
The patent optimizes the inherent viscosity parameter by controlling the CBT content within specific ranges (1-99 mol%, preferably 10-50 mol%) and adjusting processing temperatures to maintain processability while achieving improved impact strength
Solution Approach 2:
The patent introduces CBT at specific molecular locations within the polyester chain to provide localized improvements in impact strength and glass transition temperature while maintaining overall processability through controlled distribution
3Strength
If PCT crystallizes rapidly upon cooling from the melt, then high strength and stiffness are achieved, but it becomes very difficult to form amorphous articles
Solution Approach 1:
The patent changes the crystallization kinetics parameters by incorporating CBT and cyclohexanedimethanol in specific ratios to slow down the crystallization rate, enabling sufficient time for thermoforming operations while maintaining adequate strength properties
Solution Approach 2:
The patent creates a dynamic balance between crystallization and processing by controlling the copolymer composition to achieve moderate crystallization half-times that allow flexibility during forming operations while providing strength in the final product
Data Source
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 cyclohexanedimethanol residues. The polyesters have a desirable combination of inherent viscosity and glass transition temperature (“Tg”). The polyesters can have an inherent viscosity from 0.35 to 1.2 dL/g as determined in 60/40 (wt/wt) phenol/tetrachloroethane at a concentration of 0.5 g/100 ml at 25° C. and a Tg of 85 to 115° C. The polyesters may be manufactured into articles such as fibers, films, bottles or sheets.