Multilayer Container Two-Color Molding Viscosity Control
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Solution Overview
Problem
The challenge is to produce a multilayer container using two-color molding that maintains transparency, as existing methods often result in poor transparency due to interface unevenness between the polyester resin outer layer and the polyamide resin inner layer.
Innovation Solution
The solution involves adjusting the relative viscosity of the polyamide resin in the inner layer to a range of 1.8 to 2.8, using a xylylenediamine-based polyamide resin with specific structural units, and controlling the thickness ratio between the outer and inner layers to achieve optimal transparency and barrier properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If two-color molding is used to produce a multilayer container with polyester resin outer layer and polyamide resin inner layer, then the container can achieve good barrier properties, but the transparency is deteriorated due to interface unevenness
Solution Approach 1:
The patent applies parameter changes by controlling the relative viscosity of the polyamide resin within a specific range (1.8 to 2.8) to resolve the contradiction between barrier properties and transparency. This viscosity control ensures proper flow and bonding at the interface between layers, achieving both good barrier performance and high transparency without the interface unevenness that plagues conventional two-color molding processes.
2Reliability
If the polyamide resin relative viscosity is increased to improve barrier properties, then the oxygen and butyl acetate barrier properties are enhanced, but the interface unevenness increases and transparency deteriorates
Solution Approach 1:
The patent precisely controls the relative viscosity parameter of the polyamide resin within the range of 1.8 to 2.8, which is the optimal range that simultaneously achieves excellent barrier properties (oxygen transmission rate of 8.0×10^-3 cc/pkg·day or less and butyl acetate barrier properties of 0.015 g/bottle·day or less) while maintaining smooth interfaces and high transparency. This parameter optimization resolves the contradiction between barrier performance and manufacturing precision.
3Ease of manufacture
If a conventional polyamide resin is used in two-color molding, then the production process is simple, but the transparency and interface quality are poor
Solution Approach 1:
The patent maintains the simplicity of the two-color molding process while dramatically improving transparency by optimizing the relative viscosity parameter of the polyamide resin to 1.8-2.8. This parameter adjustment ensures proper flow characteristics during injection molding, enabling the resin to fill the mold cavity uniformly and bond smoothly with the polyester outer layer, thereby achieving high transparency and excellent interface quality without complicating the manufacturing process.
Data Source
AI summary
To provide a multilayer container including a two-color molding article e, a method for producing a two-layer preform, and a method for producing the multilayer container. The multilayer container including a two-color molding article, the two-color molding article including: an outer layer containing a polyester resin; and an inner layer containing a polyamide resin and being in contact with the outer layer, wherein the polyamide resin has a relative viscosity of 1.8 to 2.8.