Multilayered Cup Container Refractive Index Matching
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Solution Overview
Problem
Multilayered containers with polyester and polyamide resins face issues with maintaining transparency and interlayer adhesiveness due to refractive index variations and poor stretching properties, leading to peeling and impaired gas-barrier performance.
Innovation Solution
A multilayered container structure featuring inner and outer layers of ethylene terephthalate polyester resin and an intermediate layer of lowly crystalline ethylene terephthalate polyester resin blended with a gas-barrier aromatic polyamide resin, where the refractive index difference between the two is controlled to maintain transparency and enhance interlayer adhesiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a blend of polyester resin and aromatic polyamide resin is used as the intermediate layer to improve gas-barrier property, then gas-barrier property is improved, but transparency is impaired due to refractive index mismatch
Solution Approach 1:
The invention changes the refractive index parameter of the polyester resin by controlling its crystallinity and composition to match the refractive index of the aromatic polyamide resin. Specifically, the polyester resin is formulated to have a refractive index of 1.56-1.62, which matches the polyamide resin's refractive index of 1.56-1.60, thereby eliminating the transparency issue while maintaining the gas-barrier property improvement.
Solution Approach 2:
The invention uses a composite material approach by creating a multilayered structure where the intermediate layer consists of a blend of polyester resin and aromatic polyamide resin. This composite structure combines the excellent gas-barrier properties of the polyamide with the formability and transparency of the polyester, achieving both objectives simultaneously.
2Illumination intensity
If the refractive indexes of polyester resin and polyamide resin are adjusted to be in agreement to improve transparency, then transparency is improved, but gas-barrier property deteriorates
Solution Approach 1:
The invention applies local quality by assigning different functions to different layers: the inner and outer polyester layers provide formability and baseline transparency, while the intermediate polyamide layer provides enhanced gas-barrier property. The refractive index matching is specifically applied to the intermediate layer to maintain transparency despite the polyamide's inherent opacity, thus achieving both transparency and gas-barrier improvement locally where needed.
3Reliability
If polyamide resin is used as the intermediate layer to improve gas-barrier property, then gas-barrier property is improved, but interlayer adhesiveness deteriorates causing peeling
Solution Approach 1:
The invention uses the polyester resin as an intermediary material in the intermediate layer, blending it with the aromatic polyamide resin. The polyester component acts as a mediator that maintains compatibility and adhesion with the inner and outer polyester layers, preventing peeling while the polyamide component provides the gas-barrier enhancement.
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 container achieves excellent transparency, mechanical strength, and interlayer adhesiveness, preventing peeling and maintaining a high gas-barrier property, with a haze of not more than 5% on the side surface and improved oxygen barrier performance.
Implementation Method 1
a difference of refractive index (ΔRI) between the lowly crystalline ethylene terephthalate type polyester resin and the gas-barrier aromatic polyamide resin... is not more than 0.03
Implementation Method 2
the multilayered container is obtainable by heat-forming the multilayered precursor such that a drawing ratio H/D (H: height of a container, D: diameter of a opening of the container) is not less than 1.0
Data Source
Figure 1~2
Figure 3(A)~3(C)
AI summary
A multilayered container obtained by heat-forming a multilayered sheet or a multilayered preform (hereinafter generally referred to as "multilayered precursor") that includes inner and outer layers of an ethylene terephthalate type polyester resin, and at least one intermediate layer of at least a lowly crystalline ethylene terephthalate type polyester resin and a gas-barrier aromatic polyamide resin, wherein a difference of refractive index (ΔRI) between the lowly crystalline ethylene terephthalate type polyester resin and the gas-barrier aromatic polyamide resin represented by the following formula (1), ΔRI=|RIE−RIA| wherein RIE and RIA are refractive indexes of injection-formed plates made, respectively, from the lowly crystalline ethylene terephthalate type polyester resin and the gas-barrier aromatic polyamide resin after they have been monoaxially stretched into 3 times, is not more than 0.03, and a haze in a side surface of the container is not more than 5%. The cup-type multilayered container has a multilayered structure that includes inner and outer layers of a polyester resin and an intermediate layer of a blend of a polyester resin and an aromatic polyamide resin, and fulfills all of excellent transparency, gas-barrier property and interlayer adhesiveness.