Cyclobutanediol Polyester Composition for Slower Crystallization
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Solution Overview
Problem
Current polyester compositions based on terephthalic acid and 1,4-cyclohexanedimethanol crystallize rapidly, making it difficult to form amorphous articles, and existing modifications to slow crystallization, such as adding ethylene glycol, result in undesirable properties like higher ductile-to-brittle transition temperatures and lower glass transition temperatures.
Innovation Solution
A polyester composition comprising 70-100 mole % terephthalic acid residues, 10-30 mole % aromatic dicarboxylic acid residues, and 10-30 mole % 2,2,4,4-tetramethyl-1,3-cyclobutanediol residues, with 70-90 mole % 1,4-cyclohexanedimethanol, achieving a balance of high impact strength, moderate glass transition temperature, and long crystallization half-times while maintaining processability on standard equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If sufficient ethylene glycol is included to provide long crystallization half-times, then amorphous products can be formed, but glass transition temperature decreases and ductile-to-brittle transition temperature increases
Solution Approach 1:
The patent changes the chemical composition parameters by introducing 2,2,4,4-tetramethyl-1,3-cyclobutanediol residues (10-30 mole %) as a alternative modifying agent instead of ethylene glycol. This compositional parameter change achieves long crystallization half-times while maintaining higher glass transition temperatures (95-115°C) and lower ductile-to-brittle transition temperatures, resolving the trade-off between crystallization rate control and thermal properties
Solution Approach 2:
The patent creates a composite polyester composition containing multiple components: terephthalic acid residues (70-100 mole %), aromatic dicarboxylic acid residues (0-30 mole %), and a glycol component comprising 2,2,4,4-tetramethyl-1,3-cyclobutanediol residues (10-30 mole %) and 1,4-cyclohexanedimethanol residues (70-90 mole %). This composite structure combines the benefits of slowed crystallization with maintained thermal properties
2Loss of time
If 2,2,4,4-tetramethyl-1,3-cyclobutanediol is used to slow crystallization, then crystallization half-time increases, but inherent viscosity and melt viscosity become too high for standard equipment
Solution Approach 1:
The patent optimizes the concentration parameter of 2,2,4,4-tetramethyl-1,3-cyclobutanediol residues to 10-30 mole %, which is sufficient to achieve long crystallization half-times (greater than 5 minutes at 170°C) while keeping inherent viscosity in the range of 0.50 to less than 0.75 dL/g. This parameter optimization ensures the polyester can be processed on standard industry equipment without requiring specialized high-viscosity processing equipment
Solution Approach 2:
The patent introduces aromatic dicarboxylic acid residues (0-30 mole %) as a additional modifying component that locally adjusts the polymer structure to further reduce melt viscosity and improve processability while maintaining the crystallization modification effects of the cyclobutanediol component
3Strength
If PCT crystallizes rapidly, then high strength and stiffness are achieved, but it is very difficult to form amorphous articles by extrusion or injection molding
Solution Approach 1:
The patent uses 2,2,4,4-tetramethyl-1,3-cyclobutanediol residues and aromatic dicarboxylic acid residues as intermediary components that intervene in the crystallization process of PCT. These intermediaries slow down the crystallization rate by disrupting the regular packing of polymer chains, allowing sufficient time for amorphous article formation through extrusion or injection molding while still achieving eventual crystallization for strength
Data Source
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AI summary
Described are polyesters comprising (a) a dicarboxylic acid component comprising terephthalic acid residues; optionally, aromatic dicarboxylic acid residues or aliphatic dicarboxylic acid residues; 2,2,4,4-tetramethyl-1,3-cyclobutanediol residues; and 1,4-cyclohexanedimethanol residues. The polyesters may be manufactured into articles such as fibers, films, bottles or sheets.