Sulfo-Modified Copolyester Blend for CO2 Barrier and Clarity
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Solution Overview
Problem
Current polyester blends, such as those involving polyethylene terephthalate (PET) and polyglycolic acid, suffer from hazy articles and inadequate gas barrier properties, particularly in carbonated soft drink containers, which require improved carbon dioxide permeability and clarity.
Innovation Solution
A sulfo-modified copolyester blend with polyglycolic acid, comprising at least 75 mole % of PET or polyethylene naphthalate, 2.5 to 15 mole % isophthalate units, and 0.1 to 5.0 mole % of specific sulfo-modified units, is developed to enhance gas barrier properties and clarity by adjusting the monomer composition and processing conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polyethylene terephthalate (PET) is used to make containers, then wide acceptance and good mechanical properties are achieved, but gas barrier properties especially carbon dioxide permeability are inadequate
Solution Approach 1:
The patent applies composite materials by blending PET with polyglycolic acid (PGA) to create a new material system that combines the mechanical properties of PET with the gas barrier properties of PGA. The specific composition range (5-50 wt% PGA) creates a composite that simultaneously achieves improved CO2 barrier performance while maintaining container structural integrity and mechanical strength.
2Object-generated harmful factors
If polyglycolic acid is blended with PET to improve gas barrier, then carbon dioxide permeability is reduced, but the article becomes hazy
Solution Approach 1:
The patent applies parameter changes by precisely controlling the PGA content within the 5-50 wt% range and optimizing processing parameters (temperature, shear rate) to achieve a balance between gas barrier improvement and optical clarity. The sulfo-modified copolyester composition with specific isophthalate units (2.5-15 mole %) and sulfo-modified units (0.1-5.0 mole %) further refines the material properties to reduce haze while maintaining barrier performance.
Solution Approach 2:
The patent applies local quality by creating a heterogeneous blend structure where PGA domains are distributed within the PET matrix. This localized distribution allows regions with high PGA concentration to provide gas barrier function while regions with lower PGA concentration maintain optical clarity, thus achieving both improved CO2 permeability and acceptable transparency in different local areas of the material.
3Reliability
If higher concentration of polyglycolic acid is used to improve barrier, then gas barrier properties are enhanced, but manufacturing complexity and processing difficulty increase
Solution Approach 1:
The patent applies partial action by using moderate concentrations of PGA (5-50 wt%) rather than high concentrations, which provides sufficient gas barrier improvement while avoiding the severe processing difficulties and manufacturing complexity that would arise with higher PGA content. This partial implementation achieves the necessary barrier performance without excessive action that would complicate manufacturing.
Data Source
AI summary
The present invention relates to a blend of sulfo-modified copolyester wherein the diacid is aromatic or cyclic and polyglycolic acid. The blend of sulfo-modified copolyester and polyglycolic acid can be used to prepare containers with good transparency and high gas barrier properties. The preferred sulfo-modified copolyester composition comprises terephthalic acid, isophthalic acid and 5-sulfoisophthalic acid. A method of preparing a blend of sulfo-modified copolyester and polyglycolic acid is disclosed, as well as master batch processes. The present invention also relates to a method of making a container wherein the sulfo-modified copolyester is blended with the polyglycolic acid at an injection molding machine used to make preforms, which are then blown into bottles.