Polyester Film Dimensional Stability via Copolymer Composition
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Solution Overview
Problem
Existing polyester films struggle with dimensional stability, particularly in response to changes in humidity and temperature, due to limitations in Young's modulus and coefficient of expansion, which can lead to uneven coating during magnetic layer application.
Innovation Solution
A polyester film composition is developed with specific relative amounts of long-chain dicarboxylic acid and diol components copolymerized with aromatic dicarboxylic acid and ethylene glycol, optimizing Young's modulus and coefficient of expansion to achieve low elongation at 110°C and improved dimensional stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If polyethylene-2,6-naphthalate is used to improve mechanical properties and heat resistance, then strength and rigidity are improved, but dimensional stability with respect to humidity changes deteriorates
Solution Approach 1:
The patent employs a composite polyester composition combining polyethylene-2,6-naphthalenedicarboxylate (providing strength and heat resistance) with polyethylene terephthalate containing a specific copolymer component (providing dimensional stability). This composite approach allows simultaneous achievement of mechanical strength and dimensional stability that cannot be obtained with single polymers alone.
Solution Approach 2:
The patent modifies the chemical composition parameters of the polyester by incorporating a specific copolymer component (0.1-10 mol% of a dicarboxylic acid component with specific molecular structure) into the polyethylene terephthalate. This parameter change in composition enables the polyester to exhibit improved dimensional stability with respect to humidity while maintaining compatibility with the high-strength polyethylene-2,6-naphthalenedicarboxylate.
2Stability of the object's composition
If Young's modulus is increased to reduce coefficient of expansion, then dimensional stability is improved, but film formability deteriorates
Solution Approach 1:
The patent optimizes the compositional parameters of the polyester, specifically controlling the ratio of polyethylene-2,6-naphthalenedicarboxylate to polyethylene terephthalate copolymer, and adjusting the copolymer component content (0.1-10 mol%). This parameter optimization achieves the right balance between Young's modulus (for dimensional stability) and processability (for film formability).
Solution Approach 2:
The patent introduces a specific copolymer component with particular molecular characteristics into the polyethylene terephthalate structure. This local modification of polymer chain structure provides regions with different properties: segments that contribute to dimensional stability and segments that maintain film formability, achieving both requirements simultaneously.
Data Source
AI summary
The invention provides a polyester composition in which the primary repeating units contain an aromatic dicarboxylic acid component (Component A) and an ethylene glycol component (Component C) and a long-chain alkyl dicarboxylic acid component having not less than 6 carbons (Component B) or a long-chain alkyl diol component having not less than 6 carbons (Component D), wherein a sum (WB+WD) of a relative amount (WB) of Component B as calculated based on a total number of moles of Component A and Component B plus a relative amount (WD) of Component D as calculated based on a total number of moles of Component C and Component D are within a range of 2-13 mol %. The invention also provides a polyester film prepared from the polyester composition and having excellent dimensional stability, as well as a magnetic recording medium utilizing the polyester film.