Polyethylene Bag Intermediate Layer for Heat Sealing
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Solution Overview
Problem
Polyethylene-based plastic bags face challenges in heat-sealing due to poor printability and increased difficulty in forming seams on pre-treated surfaces, especially with thin films, which can lead to thermal and mechanical overload, making production of thin-walled packaging more complex and prone to errors.
Innovation Solution
Incorporating an intermediate layer of unmodified polyethylene with a lower melting point, such as polybutene, between pre-printed or printed surfaces to facilitate easier sealing and improve robustness, allowing for reduced film thickness while maintaining machinability and reducing material usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If polyethylene surface is pre-treated with corona treatment to improve printability, then printability is improved, but heat-sealing ability deteriorates
Solution Approach 1:
The plastic bag is divided into multiple functional layers: printed outer layers for aesthetics and protection, and an unprinted intermediate layer for reliable heat-sealing. This segmentation allows each layer to perform its specific function without interfering with others.
Solution Approach 2:
An unprinted intermediate layer of polyethylene is introduced between the pre-treated printed surfaces to act as a mediator that provides reliable heat-sealing properties. This intermediate layer compensates for the loss of sealability caused by corona treatment of the outer layers.
2Manufacturing precision
If sealing temperature and pressure are increased to improve seam formation on pre-treated surfaces, then seam formation is improved, but thermal and mechanical overload of thin films increases
Solution Approach 1:
The invention changes the material parameters of the intermediate layer (using unprinted polyethylene with appropriate melting point) to enable effective sealing at lower temperatures and pressures, thereby avoiding thermal and mechanical overload of thin films while maintaining good seam formation.
3Loss of substance
If film thickness is reduced to save material and reduce packaging waste, then material efficiency is improved, but processing difficulty and seam formation problems increase
Solution Approach 1:
The intermediate layer is applied locally only in the seam areas where heat-sealing is required, rather than throughout the entire film. This localized application provides enhanced sealability and processing ease exactly where needed, while minimizing additional material usage.
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 intermediate layer simplifies seam formation by providing a well-sealable surface and additional material strength, reducing the risk of thermal and mechanical stress during sealing, enabling the use of even thinner film materials and improving the production efficiency of plastic bags.
Implementation Method 1
The polyethylene of the intermediate layer can advantageously have a crystallite melting point of below 120°C. The intermediate layer can then be melted all the more easily on the surface that is decisive for the formation of the seam, especially since it has to be heated from the outside through the wall-forming film in the case of heat sealing.
Implementation Method 2
it has to be heated from the outside through the wall-forming film in the case of heat sealing
Data Source
Figure 1~2
AI summary
The invention relates to a plastic bag (1) with at least two walls (2, 3) which are connected by seams (4, 12) and which are made of a polyethylene monofilm or a layered film with a polyethylene layer on the inner face of the bag (1). The inner face is modified by a corona treatment or a similar printing pretreatment of the surface in order to improve the printability. The bag is designed to be usable with respect to the problematic heat sealability of printing-pretreated polyethylene surfaces to one another for the purpose of a machine-adapted processing with quick work cycles, such as the processing which is already used for unpretreated surfaces, by forming at least one seam between the pressure-pretreated inner faces of the walls (2, 3) as a sealing seam (12) with an intermediate layer (14) as a film made of a polyolefin which is not modified in the surface and the melting point of which does not lie above the melting point of the film of the plastic bag.