Polyester Resin Composition Gas Barrier and Transparency
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Solution Overview
Problem
Polyester-based packaging materials lack sufficient gas barrier properties and transparency, especially when stretched, due to poor compatibility with gas barrier resins like ethylene-vinyl alcohol copolymer, which also affects recyclability and mechanical properties.
Innovation Solution
A resin composition blending 80-98% polyester resin with 2-20% polyamide resin, specifically polymetaxylyleneadipamide, and 0.005-0.05% epoxy-functional polymer, processed through melt-kneading to enhance gas barrier and transparency, maintaining processability and recyclability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a polyester resin is blended with a gas barrier resin such as ethylene-vinyl alcohol copolymer to improve gas barrier property, then the gas barrier property is improved, but the compatibility between resins is poor resulting in turbid state and impaired transparency
Solution Approach 1:
An epoxy-functional polymer is introduced as a compatibilizer between the polyester resin and the gas barrier resin (nylon 6 or nylon 66). This intermediary substance improves the compatibility between the two resins, allowing them to mix homogeneously without forming a turbid state, thereby maintaining transparency while achieving improved gas barrier properties through the resin blend.
Solution Approach 2:
The invention creates a composite resin system consisting of polyester resin, gas barrier resin (nylon 6 or nylon 66), and epoxy-functional polymer. This composite material combines the advantages of each component: the polyester provides processability and clarity, the nylon provides gas barrier properties, and the epoxy-functional polymer ensures compatible mixing, resulting in a material that achieves both transparency and gas barrier performance.
2Reliability
If coating methods (vapor deposition of aluminum oxide or silicon oxide, or coating with high gas barrier resin) are used to improve gas barrier property of polyester, then the gas barrier property is improved, but the production process becomes more complex and recyclability is impaired
Solution Approach 1:
The invention merges the gas barrier function directly into the polyester resin matrix by blending it with nylon 6 or nylon 66 at the molecular level. This eliminates the need for separate coating steps or vapor deposition processes, as the gas barrier property is inherently provided by the blended resin itself, thereby simplifying the production process while maintaining recyclability.
3Temperature
If ethylene-vinyl alcohol copolymer resin is processed at temperature suitable for polyethylene terephthalate, then the processing temperature is appropriate, but the ethylene-vinyl alcohol copolymer resin rapidly deteriorates causing gelation and scorching
Solution Approach 1:
The invention changes the chemical composition parameters of the resin system by selecting nylon 6 or nylon 66 instead of ethylene-vinyl alcohol copolymer as the gas barrier resin. This parameter change allows the resin blend to be processed at temperatures suitable for polyester (typically 260-280°C) without the rapid deterioration, gelation, and scorching problems that occur with ethylene-vinyl alcohol copolymer at these temperatures.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The resulting resin composition exhibits excellent gas barrier properties and high transparency, even in stretched products, while maintaining mechanical properties and recyclability.
Implementation Method 1
0.005 to 0.05 parts by mass of epoxy-functional polymer (C) which contains styrene units and glycidyl (meth)acrylate units
Implementation Method 2
A resin composition blending 80-98% polyester resin with 2-20% polyamide resin, specifically polymetaxylyleneadipamide, and 0.005-0.05% epoxy-functional polymer, processed through melt-kneading
Data Source
AI summary
The present invention provides a polyester-based resin composition containing: a resin component which contains 80 to 98 mass% of polyester resin (A) including aromatic dicarboxylic acid units and diol units, and 20 to 2 mass% of polyamide resin (B) including diamine units and dicarboxylic acid units, the diamine units containing 70 mol% or more m-xylylenediamine units and the dicarboxylic acid units containing 70 mol% or more α,ω-aliphatic dicarboxylic acid units; and 0.005 to 0.1 parts by mass of a specific epoxy-functional polymer (C) with respect to 100 parts by mass of the resin component.