Polyester Film Composition for Impact Strength and Thermoformability

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Solution Overview

Problem

Current polyester films and sheets made from terephthalic acid, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, and 1,4-cyclohexanedimethanol face challenges in achieving a balance of high impact strength, moderate glass transition temperatures, chemical resistance, hydrolytic stability, and thermoformability while maintaining low densities and long crystallization half-times, which are essential for easy formation and processing.

Innovation Solution

A polyester composition comprising 70 to 100 mole % terephthalic acid residues, 0 to 30 mole % aromatic dicarboxylic acid residues, 0 to 10 mole % aliphatic dicarboxylic acid residues, 10 to 25 mole % 2,2,4,4-tetramethyl-1,3-cyclobutanediol residues, and 75 to 90 mole % 1,4-cyclohexanedimethanol residues, with inherent viscosities between 0.60 to 1.2 dL/g, allowing for improved processability and properties such as high impact strength, chemical resistance, and low ductile-to-brittle transition temperatures.

Engineering Contradictions & Design Principles

VSEngineering 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 formed, but glass transition temperature and impact strength deteriorate

Engineering Contradiction:

Improvecrystallization half-timeVSAvoidimpact strength

Core Design Contradiction:

Loss of timeVSStrength

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 maintains long crystallization half-times while preserving glass transition temperature and impact strength, resolving the contradiction between crystallization control and mechanical property maintenance.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite polyester system combining terephthalic acid, 1,4-cyclohexanedimethanol, and TMCD in specific ratios. This composite material achieves synergistic effects where the TMCD component provides both slow crystallization kinetics and maintains high impact strength, eliminating the need to sacrifice mechanical properties for crystallization control.

Inventive Principle:

Principle #40Composite materials

2Strength

If 2,2,4,4-tetramethyl-1,3-cyclobutanediol is used in high amounts, then impact strength and toughness improve, but inherent viscosity and melt viscosity increase excessively

Engineering Contradiction:

Improveimpact strengthVSAvoidmelt processability

Core Design Contradiction:

StrengthVSEase of manufacture

Solution Approach 1:

The patent optimizes the concentration parameter of TMCD to a specific range (10-30 mole %) rather than using high amounts. This parameter optimization achieves high impact strength and toughness while keeping inherent viscosity and melt viscosity at acceptable levels for industrial processing, resolving the contradiction between mechanical enhancement and processability.

Inventive Principle:

Principle #35Parameter changes

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 becomes very difficult

Engineering Contradiction:

ImprovecrystallinityVSAvoidformability of amorphous articles

Core Design Contradiction:

Stability of the object's compositionVSEase of manufacture

Solution Approach 1:

The patent introduces TMCD as an intermediary component that modifies the crystallization kinetics of the PCT system. TMCD acts as a kinetic inhibitor that slows down crystallization without preventing it entirely, allowing sufficient time for amorphous article formation while still achieving eventual crystallization, thus resolving the contradiction between crystallinity and formability.

Inventive Principle:

Principle #24Intermediary (Mediator)

4Temperature

If bisphenol A polycarbonate is used as an alternative, then high heat resistance and dimensional stability are achieved, but melt viscosity becomes too high for good processability

Engineering Contradiction:

Improveheat resistanceVSAvoidmelt processability

Core Design Contradiction:

TemperatureVSEase of manufacture

Solution Approach 1:

The patent uses a polyester composition with TMCD as a substitute for bisphenol A polycarbonate. While the polyester has different properties, it achieves sufficient heat resistance and dimensional stability for many applications at lower cost and with significantly better melt processability, providing a practical alternative that resolves the processability limitation.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Data Source

PatentUS8063172B2Film(s) and/or sheet(s) made using polyester compositions containing low amounts of cyclobutanediol

Publication Date: 2011.11.22 EASTMAN CHEM CO

AI summary

Described are film(s) and/or sheet(s) made using polyester compositions comprising polyesters comprising (a) a dicarboxylic acid component comprising 70 to 100 mole % of terephthalic acid residues, and up to 30 mole % of aromatic dicarboxylic acid residues or aliphatic dicarboxylic acid residues; and (b) a glycol component comprising 2,2,4,4-tetramethyl-1,3-cyclobutanediol residues, and 1,4-cyclohexanedimethanol residues.