Oriented Multi-Layer Shrink Film for ROSO Labels
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Solution Overview
Problem
Current shrink label films, particularly roll-on shrink-on (ROSO) labels, face limitations in shrinkage extent and durability due to the use of crystalline polymers like oriented polypropylene, which restricts their ability to conform to containers effectively and hinders recyclability, while sleeve labels offer better shrinkage but at higher production costs and equipment costs for orientation.
Innovation Solution
Development of an oriented multi-layer shrink film with at least one skin layer comprising an amorphous glassy polymer such as polystyrene and a core layer of polyolefin, allowing for preferential orientation in either the machine or cross direction, and optionally including tie layers to enhance adhesion and control shrink tension, aiming for a density less than 1.0 g/cm³ to facilitate recycling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If oriented polypropylene (OPP) is used for ROSO labels, then production cost and processing are reduced, but shrinkage extent is limited to 20% and durability is poor
Solution Approach 1:
The patent uses a composite structure combining amorphous glassy polymer skin layers (providing high shrinkage and durability) with polyolefin core layers (providing flexibility and processability). This composite material approach enables ROSO labels to achieve sleeve-label-level shrinkage (up to 70%) while maintaining the cost-effectiveness and processing advantages of traditional polypropylene-based ROSO labels.
2Ease of manufacture
If oriented polypropylene (OPP) is used for ROSO labels, then production is simplified, but glue seam stress tolerance is low causing label shift or unwrap
Solution Approach 1:
The patent changes the material parameters by replacing crystalline polypropylene with amorphous glassy polymers that have different thermal and mechanical properties. The amorphous structure allows for controlled shrinkage and reduced shrink tension, enabling the glue seam to withstand the stresses during shrinkage without causing label shift or unwrap, while maintaining processing simplicity.
3Reliability
If sleeve labels are used, then shrinkage extent increases to 70%, but production cost and equipment cost increase
Solution Approach 1:
The patent segments the label structure into multiple functional layers: amorphous glassy polymer skin layers for high shrinkage, polyolefin core layers for flexibility, and optional tie layers for adhesion. This segmentation allows each layer to contribute specific properties, enabling sleeve-label-level shrinkage (70%) to be achieved in a ROSO format without requiring the complex manufacturing and expensive equipment needed for traditional sleeve labels.
4Reliability
If amorphous glassy polymer is used, then shrinkage increases, but shrink tension increases causing glue joint failure
Solution Approach 1:
The patent applies local quality by creating different layers with distinct properties: the amorphous glassy polymer skin layers provide high shrinkage capability, while the polyolefin core layers provide flexibility and stress distribution. The optional tie layers with adhesive properties locally manage the stress at critical interfaces. This local differentiation allows the film to achieve high shrinkage (comparable to sleeve labels) while maintaining reduced shrink tension that protects the glue joint from failure.
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 achieves higher shrinkage comparable to sleeve labels with reduced shrink tension, improved durability, and lower production costs, while maintaining clarity and printability, and allows for effective recycling through aqueous floatation separation techniques.
Implementation Method 1
The oriented multi-layer shrink film has been subjected to preferential orientation in either the machine or cross direction
Implementation Method 2
Application of heat to a shrink label that is around a container causes the label to shrink and conform to the container
Implementation Method 3
allows for effective recycling through aqueous floatation separation techniques
Data Source
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AI summary
The present invention relates to a multi-layer oriented shrink film comprising at least one skin layer comprising a polystyrene material and at least one core layer comprising a polyolefin layer. The films are preferably primarily oriented in either the machine or the cross direction. These films are ideally suited for use as a shrink label which can be applied either as a CD shrink sleeve or applied using a continuous roll process. The films ideally have an overall density of less than 1.0 g/cm3, to facilitate recycling efforts.