Polyester Multilayer Film Composition for Tough, Controlled Shrinkage
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Solution Overview
Problem
Current shrinkable polyester films, such as those made from poly(vinyl chloride) and oriented polystyrene, have performance issues such as slow shrink rates, low shrink force, and low ultimate shrinkage, making them unsuitable for applications requiring controlled shrinkage and toughness, and they cannot be easily recycled or reused due to their heterogeneous structure.
Innovation Solution
Development of multilayer polyester films comprising specific combinations of glycols and diacids in particular proportions, which provide improved toughness and aging performance, with controlled shrinkage properties and a low shrink force, allowing for use in existing hot air shrink tunnel equipment and potential recycling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multilayer films are made with adhesive interlayers to bond outer and inner layers, then delamination is minimized and film integrity is improved, but manufacturing complexity increases and recyclability is lost
Solution Approach 1:
The patent merges the bonding function directly into the polyester resin composition itself, eliminating the need for separate adhesive interlayers. The resin composition contains components that provide both structural integrity and bonding capability within a single homogeneous material system, thereby reducing manufacturing complexity while maintaining film integrity.
Solution Approach 2:
The invention uses a homogeneous polyester resin composition throughout the film structure, avoiding heterogeneous multilayer constructions with adhesive tie-layers. This homogeneity enables the film to be both structurally sound and recyclable, as the entire film can be processed together without requiring separation of different material layers.
2Productivity
If shrink force is increased to improve shrinkage performance, then ultimate shrinkage is improved, but risk of crushing underlying container increases
Solution Approach 1:
The patent modifies the physical and chemical parameters of the polyester resin composition, specifically incorporating plasticizers and adjusting molecular weight distribution, to achieve an optimal balance between shrink force and film toughness. This allows the film to exert sufficient shrink force for high ultimate shrinkage while maintaining enough flexibility to prevent container crushing.
Solution Approach 2:
The resin composition is designed to exhibit dynamic mechanical properties that adapt during the shrinkage process. The film provides high shrink force when needed for contraction but can yield slightly to prevent container damage, creating a dynamic response rather than a fixed rigid behavior.
3Reliability
If film toughness is increased to prevent tearing and splitting, then film reliability is improved, but shrink force may be reduced
Solution Approach 1:
The patent creates a composite polyester resin system combining multiple components including base polyester, plasticizers, and other additives in specific proportions. This composite structure provides both enhanced toughness to prevent tearing and sufficient shrink force through the synergistic interaction of components, resolving the trade-off between these two properties.
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 multilayer polyester films exhibit controlled shrinkage, high ultimate shrinkage, and improved toughness, meeting the requirements for packaging applications while being recyclable and environmentally friendly.
Implementation Method 1
thermoshrinkable films are used as coverings, to hold objects together, and as an outer wrapping for bottles, cans and other kinds of containers... take advantage of the shrinkability created by the internal shrink stress of the film
Data Source
AI summary
Heat shrinkable films comprised of polyesters comprising certain combinations of glycols and diacids in particular proportions. These polyesters afford certain advantageous properties in the resulting shrinkable films including toughness and/or ageing, and thus are suitable as replacements for commercially available shrink films made using poly(vinyl chloride).