Multilayer Bottle Barrier Layer Scorch Prevention
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Solution Overview
Problem
Multilayer bottles face issues with delamination between layers and scorch generation during molding, which affects their commercial value and production stability, particularly when using polyamide MXD6 as a gas barrier layer, leading to reduced heat stability and contamination in molding machines.
Innovation Solution
A multilayer bottle design with a barrier layer composed of a resin blend containing 40-99 parts polyamide with a m-xylylenediamine unit and 1-60 parts polyester, along with an alkali compound, where the phosphorus concentration and alkali metal concentration are optimized within specific ranges to prevent scorch formation and enhance delamination resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polyamide MXD6 is used as a gas barrier layer to improve gas barrier properties, then gas barrier properties are enhanced, but heat stability is reduced and scorch generation occurs during molding
Solution Approach 1:
A polyol compound is introduced as an intermediary substance between the polyamide MXD6 and polyester layers. This polyol compound acts as a heat stabilizer that prevents scorch generation during molding while maintaining the gas barrier properties of the polyamide layer. The polyol compound with specific hydroxyl value range (10-50 mg KOH/g) mediates the thermal interaction, reducing harmful thermal degradation.
Solution Approach 2:
The invention changes the chemical composition parameters of the barrier layer by incorporating polyol compounds with specific molecular weight and hydroxyl value ranges. This parameter modification transforms the thermal behavior of the polyamide MXD6, suppressing scorch formation while preserving barrier functionality. The specific parameter ranges (molecular weight 500-5000, hydroxyl value 10-50 mg KOH/g) are critical for achieving the desired effect.
2Reliability
If the barrier layer is made of 100% polyamide to maximize gas barrier properties, then gas barrier performance is optimized, but delamination resistance between layers deteriorates
Solution Approach 1:
The barrier layer is designed as a composite material system consisting of polyamide MXD6 combined with polyol compounds. This composite structure integrates the gas barrier properties of polyamide with the adhesion-enhancing characteristics of polyol compounds. The composite formulation creates synergistic effects that simultaneously improve gas barrier performance and delamination resistance without requiring layer blending.
Solution Approach 2:
The polyol compound serves as a chemical intermediary that enhances the interfacial adhesion between the polyamide barrier layer and polyester contact layers. This intermediary substance improves wetting and bonding at the interfaces, preventing delamination while allowing the polyamide layer to maintain its full gas barrier functionality.
3Productivity
If resin remains in the molding machine for a long period to maintain production continuity, then productivity is maintained, but resin deterioration occurs and contaminates the product
Solution Approach 1:
The polyol compound is incorporated into the polyamide MXD6 resin composition before molding, providing preliminary heat stabilization. This pre-added stabilizer prevents resin deterioration during storage and prolonged residence in the molding machine, eliminating the need for frequent purging operations and maintaining production continuity without contamination risks.
Data Source
AI summary
In the multilayer bottle of the present invention, an outermost layer and an innermost layer are each composed of a polyester (Z1); a barrier layer is composed of a resin composition containing 40 to 99 parts by mass of a polyamide (X) and 1 to 60 parts by mass of a polyester (Z2); an alkali compound (A) is blended in the resin composition; and furthermore, the resin composition satisfies the following formulae (1) to (3). 0.01≤P≤6.5 3.2≤M≤73.1 M≥29.2-0.218α In the formulae, P represents a molar concentration (µmol/g) of phosphorus atoms; M represents a molar concentration (µmol/g) of alkali (earth) metal atoms; and α represents the parts by mass of the polyamide (X) contained in the resin composition.