Polyester Film Composition Balancing Tg, Impact, and Processability
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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, toughness, low ductile-to-brittle transition temperatures, good color and clarity, low densities, and thermoformability while maintaining processability on standard industry equipment.
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, allowing for the production of films and sheets with enhanced properties without requiring specialized equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
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's crystallization kinetics and thermal properties, achieving long crystallization half-times (greater than 30 seconds) while maintaining high impact strength and appropriate glass transition temperatures (85-120°C), thereby resolving the contradiction between crystallization control and mechanical properties
Solution Approach 2:
The patent creates a composite polyester material combining terephthalic acid, 1,4-cyclohexanedimethanol, and 2,2,4,4-tetramethyl-1,3-cyclobutanediol in specific ratios. This composite approach leverages the complementary properties of each component: terephthalic acid provides structural rigidity, 1,4-cyclohexanedimethanol contributes to flexibility and impact resistance, and TMCD enables slow crystallization while maintaining mechanical strength, thus resolving the property trade-offs
2Stability of the object's composition
If polymers containing 2,2,4,4-tetramethyl-1,3-cyclobutanediol are used to achieve moderate glass transition temperature and long crystallization half-times, then high inherent viscosities and high melt viscosities result, making manufacturing and post-polymerization difficult with standard equipment
Solution Approach 1:
The patent optimizes the molar ratio parameters of the polyester components, specifically limiting TMCD to 1-50 moles percent and 1,4-cyclohexanedimethanol to 50-99 moles percent. This parameter control balances the glass transition temperature (achieving 85-120°C) and crystallization half-time while keeping inherent viscosity below 1.0 dL/g and melt viscosity at manageable levels, enabling processability on standard industry equipment
Solution Approach 2:
The patent introduces optional additives (0-10 moles percent) such as isophthalic acid, ethylene glycol, or other modifiers to locally adjust specific properties of the polyester. These localized compositional adjustments fine-tune the balance between viscosity, crystallization rate, and mechanical properties without compromising the overall processability or requiring specialized equipment
3Speed
If PCT crystallizes rapidly upon cooling from the melt, then crystallization occurs quickly, but it becomes very difficult to form amorphous articles by extrusion, injection molding, and similar methods
Solution Approach 1:
The patent modifies the crystallization kinetics by incorporating 2,2,4,4-tetramethyl-1,3-cyclobutanediol into the polyester structure. This compositional change extends the crystallization half-time from seconds (in PCT) to greater than 30 seconds, providing sufficient time window for mold filling and processing before crystallization begins, thereby enabling successful formation of amorphous articles through extrusion, injection molding, and other conventional methods
Solution Approach 2:
The patent performs preliminary compositional design by selecting specific monomer ratios before polymerization to pre-determine the crystallization behavior. By incorporating TMCD at 1-50 moles percent in the formulation stage, the polymer is pre-configured with slow crystallization kinetics, ensuring that during subsequent processing operations, the material remains processable and can be formed into amorphous articles before crystallization occurs
Data Source
AI summary
Described are film or sheet, comprising polyester based composition, comprising dicarboxylic acid component as terephthalic acid residues and optionally, aromatic dicarboxylic acid residues or aliphatic dicarboxylic acid residues and glycol component, comprising 2,2,4,4-tetramethyl-1,3-cyclobutanediol residues and cyclohexanedimethanol residues. The polyester composition has the inherent viscosity from 0.55 to 0.68 dL/g as determined in 60/40 (wt/wt) phenol/tetrachloroethane at a concentration of 0.5 g/100 ml at 25° C., glass transition temperature Tg of 110° C. to 160° C., notched Izod impact strength of at least 7.5 ft-lb/inch at 23° C. according to ASTM D256 with a 10-mil notch in a ⅛-inch thick bar, melt viscosity is less than 10,000 poise as measured at 1 radian/second on a rotary melt rheometer at 290° C. and does not contain polycarbonate.