TMCD Polyester Film Composition for Tough Amorphous Sheets
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Solution Overview
Problem
Current polyester films and sheets face challenges in achieving a combination of high impact strength, moderate glass transition temperature, chemical resistance, hydrolytic stability, and processability on standard industry equipment, while also maintaining low densities and thermoformability.
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 sheets with improved properties such as toughness, heat resistance, and clarity, 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 with higher ductile-to-brittle transition temperatures and lower glass transition temperatures are achieved, but impact strength and glass transition temperature properties deteriorate
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 chain structure and intermolecular forces, achieving long crystallization half-times (greater than 30 minutes at 25°C) while simultaneously improving impact strength and maintaining appropriate glass transition temperatures, thus resolving the contradiction between crystallization rate and mechanical properties
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 in specific ratios. This composite approach leverages the rigid aromatic terephthalic acid units for structural integrity, the flexible cycloaliphatic 1,4-cyclohexanedimethanol for toughness, and the bulky TMCD units for slow crystallization and enhanced impact resistance, achieving synergistic improvement of all desired properties
2Strength
If 2,2,4,4-tetramethyl-1,3-cyclobutanediol is used in polymers, then high inherent viscosities and high glass transition temperatures are achieved, but processability on standard equipment deteriorates
Solution Approach 1:
The patent optimizes the TMCD content parameter within a specific range (10-40 mole percent, preferably 15-30 mole percent) to balance inherent viscosity and processability. By controlling the TMCD concentration and resulting inherent viscosity (0.60-0.85 dL/g), the patent achieves high mechanical strength while maintaining melt flow properties suitable for standard extrusion and injection molding equipment, thus resolving the contradiction between viscosity and processability
3Stability of the object's composition
If PCT crystallizes rapidly upon cooling from the melt, then high crystallinity is achieved, but formation of amorphous articles by extrusion and injection molding becomes very difficult
Solution Approach 1:
The patent introduces 2,2,4,4-tetramethyl-1,3-cyclobutanediol as an intermediary component that disrupts the rapid crystallization kinetics of pure PCT. The bulky TMCD units act as spacing groups that interfere with chain packing and crystal nucleation, extending the crystallization half-time to greater than 30 minutes at 25°C. This intermediary substitution enables the formation of amorphous articles through conventional processing while maintaining controlled crystallinity when desired
Solution Approach 2:
The patent modifies the compositional parameters by incorporating 10-40 mole percent TMCD into the PCT structure, which fundamentally changes the crystallization kinetics. This parameter change extends the processing window by slowing crystallization rate, allowing sufficient time for mold filling and article formation before crystallization begins, thus enabling manufacturing of amorphous and semi-crystalline articles on standard equipment
4Strength
If bisphenol A polycarbonate is used to achieve high heat resistance and good impact strength, then physical properties are improved, but melt viscosity becomes relatively high leading to poor melt processability
Solution Approach 1:
The patent changes the chemical composition by substituting the polycarbonate backbone with a polyester backbone containing TMCD units. This parameter change in molecular structure reduces melt viscosity significantly compared to bisphenol A polycarbonate, while the rigid aromatic terephthalic acid units and bulky TMCD groups maintain high heat resistance and impact strength. The resulting polyester processes more easily on standard equipment while achieving comparable or superior mechanical properties
Data Source
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AI summary
Described are film(s) and/or sheet(s) comprising polyesters comprising (a) a dicarboxylic acid component having terephthalic acid residues; optionally, aromatic dicarboxylic acid residues or aliphatic dicarboxylic residues; 2,2,4,4- tetramethyl-1 ,3-cyclobutanediol residues; and 1 ,4-cyclohexanedimethanol residues.