Polyester Composition With Cyclobutanediol For Amorphous Articles
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Solution Overview
Problem
Current polyester compositions based on terephthalic acid, cyclohexanedimethanol, and 2,2,4,4-tetramethyl-1,3-cyclobutanediol face challenges such as rapid crystallization, poor processability, and deficiencies in properties like impact strength, glass transition temperature, and chemical resistance, making them difficult to form into amorphous articles and limiting their industrial applications.
Innovation Solution
A polyester composition with specific mole percentages of terephthalic acid, aromatic and aliphatic dicarboxylic acid residues, and 2,2,4,4-tetramethyl-1,3-cyclobutanediol and cyclohexanedimethanol, optimized for inherent viscosity and glass transition temperature, which allows for improved processability and enhanced properties like impact strength, chemical resistance, and thermoformability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If sufficient modifying 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) and adjusting the molar ratios of components. This substitution maintains long crystallization half-times while preserving higher glass transition temperatures and impact strengths that were lost with ethylene glycol modification.
Solution Approach 2:
The patent creates a composite polyester formulation combining terephthalic acid, cyclohexanedimethanol, and TMCD in specific proportions. This composite approach achieves synergistic effects where the combination of components provides both slow crystallization kinetics and maintained mechanical properties, particularly impact strength and glass transition temperature.
2Strength
If polymers containing 2,2,4,4-tetramethyl-1,3-cyclobutanediol are used to achieve moderate glass transition temperatures and good impact strength, then inherent viscosity increases and melt processability deteriorates
Solution Approach 1:
The patent optimizes the inherent viscosity parameter by controlling the TMCD content within specific ranges (5-50 mol%) and adjusting the overall molecular weight through controlled polymerization. This parameter optimization ensures moderate glass transition temperatures and good impact strength while maintaining inherent viscosity levels that allow standard industry equipment to process the material effectively.
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 introduces copolymer components (TMCD and cyclohexanedimethanol units) as intermediaries that disrupt the regular crystalline structure formation. These intermediary units interfere with the rapid crystallization kinetics of pure PCT, allowing the material to be formed into amorphous articles while maintaining the strength and stiffness characteristics of the polyester backbone structure.
Data Source
AI summary
A molded article comprising at least one polyester which comprises: (a) a dicarboxylic acid component comprising: i) 95 to 99.99 mole % of terephthalic acid residues; and ii) 0.01 to 5 mole % of isophthalic acid; and (b) a glycol component comprising: i) 5 to 15 mole % of 2,2,4,4-tetramethyl-1,3-cyclobutanediol residues; ii) 85 to 95 mole % of 1,4-cyclohexanedimethanol residues; and iii) 5 mole % or less of modifying glycols which are not 2,2,4,4-tetramethyl-1,3-cyclobutanediol or cyclohexanedimethanol, wherein the polyester has an inherent viscosity from 0.80 to 1.0 dL/g and a glass transition temperature (Tg) of 90 to 110° C., and wherein the molded article does not contain polycarbonate.