Multilayer Oriented Film Low Crystallinity Tie Layer
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Solution Overview
Problem
The bond strength between polyester or co-polyester layers of high crystallinity and conventional adhesive layers in oriented structures is sometimes not sufficiently high, leading to delamination issues in heat-shrinkable or heat-set films.
Innovation Solution
Incorporating a layer of co-polyester with a relatively low crystallinity between the high crystallinity polyester or co-polyester layer and the polyolefin-based adhesive layer to enhance the bond strength and prevent delamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a polyester layer with high crystallinity (>15%) is used in the outer layer, then abuse resistance, printability, and optical properties are improved, but bond strength to adhesive layers deteriorates leading to delamination
Solution Approach 1:
A tie layer comprising a copolyester with low crystallinity (<15%) is introduced as an intermediary between the high crystallinity polyester outer layer and the polyolefin-based adhesive layer. This tie layer acts as a mediator that provides both crystallinity for structural integrity and sufficient adhesion to the adhesive layer, preventing delamination while maintaining the benefits of high crystallinity polyester.
Solution Approach 2:
The invention creates a composite multilayer structure where different polyester materials with complementary properties are combined. The outer layer uses high crystallinity polyester for mechanical strength and optical properties, while the tie layer uses low crystallinity copolyester for adhesion, creating a composite system that achieves both durability and bond strength.
2Illumination intensity
If a polyester layer with high crystallinity (>15%) is used in the outer layer, then optical properties and gloss are improved, but bond strength to adhesive layers deteriorates
Solution Approach 1:
The low crystallinity copolyester tie layer serves as an intermediary that decouples the optical performance requirements from the adhesion requirements. It allows the high crystallinity outer layer to provide gloss and optical properties while the tie layer provides the necessary bond to the adhesive layer.
Solution Approach 2:
Different regions of the film structure are assigned different crystallinity levels appropriate to their function: the outer layer has high crystallinity for optical properties, while the tie layer has low crystallinity for adhesion. This local differentiation of material properties resolves the contradiction between gloss and bond strength.
3Reliability
If adhesive layers are used to bind polyester layers, then bond between layers is improved, but delamination occurs when polyester has high crystallinity
Solution Approach 1:
The low crystallinity copolyester tie layer acts as a mediator between the high crystallinity polyester and the polyolefin adhesive. It provides a compatible interface that ensures stable bonding, preventing the delamination that would otherwise occur due to the incompatibility between high crystallinity polyester and conventional adhesives.
4Ease of manufacture
If conventional adhesive layers are used with high crystallinity polyester, then manufacturing process is simple, but structural integrity deteriorates due to delamination
Solution Approach 1:
The invention maintains manufacturing simplicity by using a coextrusion process to create a multilayer composite structure. The composite includes high crystallinity polyester for structural integrity, low crystallinity copolyester for adhesion, and polyolefin for bonding, all integrated in a single manufacturing step that preserves both ease of production and structural strength.
Data Source
Figure 1(a)~3(d)
Figure 4(a)~5(g)
AI summary
A multilayer oriented film comprising at least one layer (a) comprising one or more polyesters and/or copolyesters characterized by a % of crystallinity higher than 15, an adjacent layer (b) comprising one or more polyolefin-based adhesive resins, and a layer (c) comprising one or more co-polyesters characterized by a % of crystallinity lower than 15, is positioned between said two layers (a) and (b) in such a way that one of the two principal surfaces of layer (c) is directly adhered to layer (a) and the other is directly adhered to layer (b). The presence of a co-polyester layer (c) of relatively low % crystallinity positioned between (co)polyester layer (a) and adhesive layer (b) remarkably increases the bond between the two layers (a) and (b) and prevents delamination problems in the oriented structure.