Thermal Stabilization of MDOPE Outer Layer for Gusset Bag Welding
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Solution Overview
Problem
Existing methods for manufacturing flexible plastic packaging bags with gussets suffer from flatness defects due to deformation and degradation of the outer layer during welding, leading to inefficiencies in the packaging process.
Innovation Solution
The process involves stretching and thermally stabilizing the polyethylene outer layer before welding, ensuring that the welding operations do not soften or degrade the outer layer, while using a hot stamping device to melt the inner layer for bonding, and optionally employing a thermal insulation strip to prevent contact between longitudinal edges during welding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the thickness of the inner layer is increased to produce durable welds, then the welding strength is improved, but the welding temperature must be increased beyond the stability temperature of the outer MDOPE layer, causing shrinkage and flatness defects
Solution Approach 1:
The patent applies a preliminary thermal stabilization treatment to the outer MDOPE layer before welding. This pre-treatment modifies the thermal properties of the outer layer, raising its softening temperature and enabling it to withstand the high welding temperatures required for strong inner layer welds without deforming or creating flatness defects.
Solution Approach 2:
The patent changes the thermal parameters of the outer layer through thermal stabilization, specifically increasing its softening temperature. This parameter change allows the outer layer to maintain its dimensional stability during high-temperature welding operations, resolving the contradiction between weld strength and flatness.
2Strength
If the welding temperature is increased to ensure durable welds, then the welding strength is improved, but the outer MDOPE layer softens and degrades, creating deformations and flatness defects
Solution Approach 1:
The patent applies a preliminary thermal stabilization treatment to the outer MDOPE layer before welding. This pre-treatment modifies the thermal properties of the outer layer, raising its softening temperature and enabling it to withstand the high welding temperatures required for strong inner layer welds without deforming or creating flatness defects.
Solution Approach 2:
The patent changes the thermal parameters of the outer layer through thermal stabilization, specifically increasing its softening temperature. This parameter change allows the outer layer to maintain its dimensional stability during high-temperature welding operations, resolving the contradiction between weld strength and flatness.
3Productivity
If the outer layer is stretched in the production direction to improve bag efficiency, then the packaging efficiency is improved, but the polyethylene becomes more sensitive to thermal degradation during welding
Solution Approach 1:
The patent applies a preliminary thermal stabilization treatment to the stretched outer MDOPE layer before welding. This pre-treatment is crucial because it addresses the thermal instability introduced by the stretching process, enabling the stretched material to withstand subsequent high-temperature welding without degradation.
Solution Approach 2:
The patent changes the thermal parameters of the stretched outer layer through thermal stabilization, raising its softening temperature and improving its thermal stability. This allows the material to maintain both the efficiency benefits of stretching and the reliability needed for welding.
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
This approach eliminates flatness defects, enhances the rigidity, gloss, and transparency of the outer layer, and maintains the aesthetic integrity of the packaging bags by optimizing the welding process without degrading the outer layer, thus improving the manufacturing efficiency and quality of the bags.
Implementation Method 1
after stretching the polyethylene of the outer layer in the production direction and both in the transverse direction
Implementation Method 2
the thermal stability of the polyethylene is obtained by carrying out an annealing operation
Implementation Method 3
said polyethylene is thermally stabilized so that the welding operations are carried out without softening or degrading the outer layer
Implementation Method 4
the welding operations are carried out by means of a hot stamping device applied to the outer layer by melting the inner layer
Implementation Method 5
a strip of material with thermal insulation properties, for example polytetrafluoroethylene, can be arranged between the longitudinal edges of the folded gussets so that, during the welding operation, said longitudinal edges each rest on, and in particular on either side of, the strip
Data Source
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Figure 3~4
AI summary
The invention relates to a method for manufacturing a plurality of packaging bags (1) comprising at least a front wall (2) and a back wall (3), optionally connected by gussets (4), a bottom (5), and a filling opening (6), the bags (1) are manufactured from at least one plastic film (7) subjected to successive folding, welding and cutting operations to continuously form the packaging bags (1), the film (7) comprises at least two layers, including an inner layer (8) of polyethylene intended to be positioned inside the bag (1) and an outer layer (9) intended to be positioned outside the bag (1) and made of molten polyethylene of a density greater than 0.93g/cm3 extruded along one production direction and stretched in the fixed state in at least one direction in a ratio between 3:1 and 10:1,The welding operations are carried out by means of a hot-stamping device (10) applied to the outer layer (9) by melting the inner layer (8). According to the invention, after stretching the polyethylene of the outer layer (9) and before the welding operations, said polyethylene is thermally stabilized so that the welding operations are carried out without softening or degrading the outer layer (9).