Polyester Blood Therapy Containers With Slower Crystallization
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Solution Overview
Problem
Current blood therapy containers face challenges in achieving a combination of high impact strength, glass transition temperature, hydrolytic stability, chemical resistance, and processability while maintaining clarity and low density, as existing materials like polycarbonate suffer from poor melt processability and chemical resistance.
Innovation Solution
Development of polyester compositions comprising terephthalic acid, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, and 1,4-cyclohexanedimethanol with specific monomer ratios and additives, which offer improved mechanical properties and processability, allowing for the production of blood therapy containers with enhanced performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PCT polyester is used to produce blood therapy containers, then hydrolytic stability and chemical resistance are improved, but crystallization rate is too rapid allowing formation of amorphous articles
Solution Approach 1:
The patent modifies the crystallization kinetics of PCT by changing compositional parameters - specifically incorporating copolymer units from ethylene glycol and/or isophthalic acid modifications. This alters the molecular structure to slow crystallization rate while preserving the hydrolytic stability of the PCT backbone, enabling amorphous molding processes.
Solution Approach 2:
The invention creates a composite polyester system combining PCT segments with copolymer segments (ethylene glycol-modified or isophthalic acid-modified units). This composite structure integrates the hydrolytic stability of PCT with the slower crystallization characteristics of the copolymer components, achieving both reliability and manufacturability.
2Ease of manufacture
If ethylene glycol or isophthalic acid modifiers are added to PCT to slow crystallization, then processability is improved, but glass transition temperature and impact strength decrease
Solution Approach 1:
The patent optimizes the concentration parameters of modifying agents, limiting ethylene glycol to 0.1-10 mole% and isophthalic acid to 0.1-10 mole% of total dicarboxylic acid content. This controlled parameter change slows crystallization sufficiently for processing while minimizing the degradation of impact strength and Tg that occurs with higher modifier concentrations.
3Ease of manufacture
If sufficient ethylene glycol is included to provide long crystallization half-times, then amorphous product formation is enabled, but ductile-to-brittle transition temperature increases and glass transition temperature decreases
Solution Approach 1:
The patent precisely controls the ethylene glycol content parameter at 0.1-10 mole% of total glycol content, which is sufficient to extend crystallization half-time for amorphous molding but limited enough to avoid excessive reduction in glass transition temperature. This parameter optimization balances processability with thermal properties.
Solution Approach 2:
The invention introduces localized copolymer segments within the PCT structure rather than uniform modification throughout. The ethylene glycol and isophthalic acid units are distributed as discrete copolymer sequences, creating local regions that slow crystallization without globally compromising the thermal transitions of the bulk material.
Data Source
AI summary
Described are blood therapy containers comprising polyester compositions comprising polyesters which comprise (a) a dicarboxylic acid component having terephthalic acid residues; optionally, aromatic dicarboxylic acid residues or aliphatic dicarboxylic acid residues or ester residues thereof; 2,2,4,4-tetramethyl-1,3-cyclobutanediol residues; and 1,4-cyclohexanedimethanol residues.