TMCD Copolyester Composition Balancing Tg, Impact, and Melt Flow
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Solution Overview
Problem
Current polyester compositions based on terephthalic acid, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, and 1,4-cyclohexanedimethanol face challenges in achieving a balance of high impact strength, glass transition temperature, chemical resistance, hydrolytic stability, 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 0 to 10 mole % aliphatic dicarboxylic acid residues, combined with 1 to 99 mole % 2,2,4,4-tetramethyl-1,3-cyclobutanediol residues and 1 to 99 mole % 1,4-cyclohexanedimethanol residues, with specific inherent viscosity and glass transition temperature ranges, allowing for improved processability and retention of desired properties.
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 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) and adjusting the molar ratios of terephthalic acid, cyclohexanedimethanol, and TMCD to achieve the desired balance between crystallization half-time and impact strength
Solution Approach 2:
The patent creates a copolyester composite material containing three different glycol components (ethylene glycol, cyclohexanedimethanol, and TMCD) and two different diacid components (terephthalic acid and isophthalic acid) to achieve a synergistic effect that simultaneously provides long crystallization half-time and high impact strength
2Strength
If 2,2,4,4-tetramethyl-1,3-cyclobutanediol is used to improve impact strength and glass transition temperature, then mechanical properties are enhanced, but inherent viscosity and melt viscosity increase making processing difficult
Solution Approach 1:
The patent controls the inherent viscosity parameter by limiting TMCD content to a specific range (1-99 mole %) and adjusting the overall composition to achieve inherent viscosity between 0.35-1.20 dL/g, balancing mechanical properties with processability
Solution Approach 2:
The patent applies different glycol components in different proportions within the polymer structure, with TMCD providing local regions of high strength and Tg while other components maintain overall 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 becomes very difficult
Solution Approach 1:
The patent changes the crystallization kinetics by incorporating copolymer components (isophthalic acid and TMCD) that disrupt the regular crystal lattice formation, extending the crystallization half-time from seconds to minutes and enabling thermoforming processing
Solution Approach 2:
The patent uses copolymer components as intermediaries that interfere with the crystallization process, acting as kinetic inhibitors that allow sufficient time for thermoforming before crystallization begins
Data Source
AI summary
Described are polyester compositions comprising at least one polyester which comprises terephthalic acid residues, 2,2,4,4-tetramethyl-l,3-cyclobutanediol, and 1,4-cyclohexanedimethanol, wherein the inherent viscosity of said polyester is 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.; wherein said polyester has a Tg from 110 to 160° C.; wherein the polyester composition comprises no polycarbonate; wherein the melt viscosity of the polyester is less than 10,000 poise as measured at 1 radian/second on a rotary melt rheometer at 290° C.; and wherein the polyester has a notched Izod impact strength, of at least 7.5 ft-lb/in.ch at 23° C. according to ASTM D256 with a 10-mil notch in a ⅛ inch thick bar. The polyesters may be manufactured into articles of manufacture as fibers, films, bottles or sheets.