Co-injection Multilayer EVOH Polypropylene Adhesion
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Solution Overview
Problem
Existing co-injection-molded multilayer structures with EVOH layers and polypropylene resin layers face challenges in achieving sufficient adhesiveness without using adhesive resin layers, leading to delamination issues during deformation.
Innovation Solution
A co-injection-molded multilayer structure with a barrier layer made of an ethylene-vinyl alcohol copolymer and an alkali metal salt of a higher fatty acid, combined with outer layers of unmodified and maleic anhydride-modified polypropylene, where the alkali metal salt is concentrated at the interface to enhance adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If an adhesive resin layer is used between EVOH layer and hydrophobic resin layer, then interlayer adhesion is improved, but production cost increases and layer structure becomes complex
Solution Approach 1:
The invention extracts and eliminates the adhesive resin layer from the multilayer structure. By directly bonding the EVOH layer to the hydrophobic resin layer without an intermediate adhesive layer, the patent simplifies the layer structure while maintaining adequate adhesion through optimized resin composition and processing conditions.
Solution Approach 2:
The invention merges the functions of the adhesive layer into the EVOH layer and hydrophobic resin layer themselves. By adjusting the composition and processing parameters of these layers, they directly provide the adhesion function that previously required a separate adhesive layer, thereby reducing structural complexity.
2Productivity
If multiple resin layers are co-injected to form multilayer structure, then production efficiency is improved, but achieving uniform adhesive layer formation becomes technically difficult
Solution Approach 1:
The invention removes the adhesive resin layer from the co-injection process, eliminating the technical difficulty of forming a uniform adhesive layer. The EVOH layer and hydrophobic resin layer are directly co-injected and bonded without requiring precise control of adhesive layer formation.
Solution Approach 2:
The invention optimizes processing parameters such as injection temperature, injection sequence, and resin composition to enable direct bonding between layers during co-injection. By controlling these parameters, uniform adhesion is achieved without the complexity of forming a separate adhesive layer.
3Ease of manufacture
If EVOH is used as barrier layer without adhesive resin layer, then production cost is reduced, but delamination occurs during deformation
Solution Approach 1:
The invention optimizes the composition and processing parameters of the EVOH layer and hydrophobic resin layer to achieve sufficient adhesion without an adhesive layer. By controlling resin composition, molecular weight, and processing conditions, the direct bond between layers resists delamination during deformation while maintaining cost effectiveness.
Solution Approach 2:
The invention uses composite resin compositions in the EVOH layer and hydrophobic resin layer that enhance interfacial bonding. By incorporating specific additives or modifying the resin composition, the direct interface between layers achieves adhesion strength sufficient to prevent delamination during deformation.
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 solution achieves high adhesiveness between the EVOH barrier layer and polypropylene outer layers, preventing delamination and improving the overall interlayer adhesion without the need for an adhesive resin layer, thus reducing production costs.
Implementation Method 1
the alkali metal salt is concentrated at the interface to enhance adhesion
Data Source
AI summary
There is provided a co-injection-molded multilayer structure having a barrier layer and outer layers laminated on both sides of the barrier layer, wherein the barrier layer is made of a resin composition comprising an ethylene-vinyl alcohol copolymer (A) and an alkali metal salt (B) of a higher fatty acid having a melting point of 250° C. or lower; a content of the alkali metal salt (B) in the barrier layer is 50 to 1500 ppm in terms of metal atoms; and the outer layers are made of a resin composition comprising an unmodified polypropylene (E) and a maleic anhydride-modified polypropylene (F) having a lower melt viscosity than that of the unmodified polypropylene (E). Although it has no adhesive layers, the co-injection-molded multilayer structure exhibits excellent adhesiveness between the barrier layer made of an EVOH resin composition and the outer layer made of a polypropylene resin composition.