TMCD-Modified Polyester Composition for Slower Crystallization
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Solution Overview
Problem
Current polyester compositions based on terephthalic acid and 1,4-cyclohexanedimethanol exhibit rapid crystallization, leading to difficulties in forming amorphous articles, and have limitations in impact strength, glass transition temperature, and chemical resistance, while polymers with 2,2,4,4-tetramethyl-1,3-cyclobutanediol face high melt viscosities and processing challenges.
Innovation Solution
A polyester composition comprising 70-100 mole % terephthalic acid, 0-30 mole % aromatic dicarboxylic acid residues, 0-10 mole % aliphatic dicarboxylic acid residues, 10-25 mole % 2,2,4,4-tetramethyl-1,3-cyclobutanediol, and 75-90 mole % 1,4-cyclohexanedimethanol, with inherent viscosities between 0.60 to 1.2 dL/g, offering improved impact strength, hydrolytic stability, and processability 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 can be formed, but the glass transition temperature decreases and impact strength is reduced
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 improving impact strength and glass transition temperature, as TMCD provides both steric hindrance to crystallization and enhances polymer chain flexibility and intermolecular interactions.
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. This composite approach leverages the synergistic effects of different monomers: PCT provides the base polymer structure, while TMCD acts as a comonomer that simultaneously extends crystallization time and enhances mechanical properties.
2Strength
If 2,2,4,4-tetramethyl-1,3-cyclobutanediol is used to extend crystallization half-time, then impact strength and chemical resistance improve, but inherent viscosity and melt viscosity increase leading to processing difficulties
Solution Approach 1:
The patent optimizes the concentration parameter of TMCD in the polyester formulation, maintaining it within 5-50 mole% of the total glycol component. This parameter control balances the competing effects: sufficient TMCD content to improve impact strength and extend crystallization half-time, while limiting content to prevent excessive viscosity that would impair processability on standard equipment.
Solution Approach 2:
The patent introduces local structural features through the cyclic structure and methyl groups of TMCD units within the polyester chain. These localized structural modifications provide steric hindrance to crystallization (extending half-time) and enhance chain flexibility (improving impact strength) without uniformly increasing the overall polymer viscosity to unmanageable levels.
3Stability of the object's composition
If PCT is used to achieve rapid crystallization, then structural stability is improved, but difficulty in forming amorphous articles increases
Solution Approach 1:
The patent introduces 2,2,4,4-tetramethyl-1,3-cyclobutanediol as an intermediary comonomer that mediates between the rapid crystallization tendency of PCT and the need to form amorphous articles. TMCD units act as spacacers that disrupt crystalline packing while maintaining polymer stability, allowing sufficient time for processing before crystallization occurs.
Data Source
AI summary
Described as one aspect of the invention are polyesters containing (a) a dicarboxylic acid component having from 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 having from 11 to 25 mole % of 2,2,4,4-tetramethyl-1,3-cyclobutanediol residues, and 75 to 89 mole % of 1,4-cyclohexanedimethanol residues; wherein the total mole % of the dicarboxylic acid component is 100 mole %, and the total mole % of the glycol component is 100 mole %. The polyesters may be manufactured into articles.