High-Shrink Multilayer Packaging Film for Directional Tear
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Solution Overview
Problem
Existing heat-shrinkable packaging films for low abuse meat products require a balance of high shrinkability, easy openability, and toughness while minimizing polyamide content to reduce costs and environmental impact.
Innovation Solution
A multilayer film structure incorporating a crosslinked polymer network, incompatible polymer blends, and a heat-seal layer with a cross-linked polymer network, along with a polyester outer layer and an oxygen barrier layer, to achieve high shrinkability and easy manual tear in the machine direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If polyamide is used to provide high toughness and strength, then the film strength and toughness are improved, but the cost increases and environmental impact worsens
Solution Approach 1:
The patent removes polyamide from the film structure entirely, extracting the problematic component while maintaining film strength through alternative materials (polyester outer layer with EVOH barrier and polyolefin inner layer). This eliminates the need for expensive polyamide while reducing environmental impact.
Solution Approach 2:
The patent uses a composite multilayer structure combining polyester, EVOH, and polyolefin layers to achieve the required strength and barrier properties without polyamide. The composite structure provides synergistic benefits where each layer contributes specific properties.
2Loss of substance
If the film is made thinner to minimize cost and waste, then material cost and environmental impact are reduced, but the film strength and ability to withstand abuse decreases
Solution Approach 1:
The multilayer composite structure provides high strength-to-thickness ratio by combining materials with complementary properties. The polyester layer provides tensile strength, EVOH provides barrier properties, and polyolefin provides heat seal and flexibility, allowing thin film design that still withstands processing and shipping abuse.
Solution Approach 2:
Each layer is optimized for its specific function: polyester for outer strength and clarity, EVOH for oxygen barrier, polyolefin for heat seal and flexibility. This localized optimization allows the overall thin film to achieve required performance.
3Stability of the object's composition
If high shrinkability is achieved through film composition, then heat-shrink performance is improved, but the film may lose easy-openability and manual tear characteristics
Solution Approach 1:
The patent achieves high shrinkability (≥90% total free shrink) through specific polymer selection and blending ratios while controlling the crystalline structure and orientation of the film. The polyolefin/polyester/EVOH composition with specific weight ratios enables both high shrink and easy-open properties.
Solution Approach 2:
The film is divided into functional layers with the polyolefin inner layer providing heat seal and shrink, polyester outer layer providing strength and easy-open characteristics, and EVOH providing barrier. This segmentation allows each layer to optimize its specific function.
4Loss of substance
If the film structure is simplified to eliminate polyamide, then cost and environmental impact are improved, but achieving required strength and barrier properties becomes more difficult
Solution Approach 1:
The patent replaces polyamide with a composite of polyester, EVOH, and polyolefin that collectively provides equal or superior performance. The polyester-EVOH-polyolefin tri-layer structure achieves required strength, toughness, and barrier properties without polyamide.
Solution Approach 2:
The polyester outer layer performs multiple functions: provides tensile strength, optical clarity, gloss, and contributes to easy-openability. The EVOH layer provides oxygen barrier while the polyolefin provides heat seal and flexibility, creating a multi-functional system that replaces polyamide's roles.
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 film provides high shrinkability, easy manual tear, and sufficient strength to withstand processing and handling, while eliminating or reducing polyamide, thus minimizing waste and costs.
Implementation Method 1
the presence of a crosslinked polymer network is required in order to provide a high shrink, high energy-to-break film
Implementation Method 2
In an embodiment, the crosslinked polymer network is formed by irradiating a portion of the film
Implementation Method 3
heat-shrinkable packaging articles have become tougher and easier to seal, with improved oxygen and moisture barrier properties, and having higher total free shrink at lower temperatures
Data Source
AI summary
A packaging article comprises a heat-shrinkable film having a total free shrink at 85° C. of at least 90%. The film has an inside seal layer, an outside polyester layer, and an inner oxygen barrier layer. A portion of the film contains a crosslinked polymer network. At least one film layer comprises an incompatible polymer blend. The article has tear initiators. The package provides post-shrink, full-length tear from the tear initiators to the opposite edge of the article, for easy product removal. The film has an instrumented impact energy-to-break of at least 0.65 J/mil, and/or an instrumented impact peak load strength of at least 66 Newtons/mil, and/or Truburst strength of at least 8 psi/mil.