LDPE Extrusion Coating Thermal Stability
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Solution Overview
Problem
Low density polyethylene (LDPE) degrades at high processing temperatures during extrusion coating, leading to cross-linking, reduced melt flow rate, and compromised adhesion and sealing performance, which limits high-speed processing and heat sealing efficiency.
Innovation Solution
A low density polyethylene composition produced in a tubular reactor without additives, maintaining a high melt flow rate and vinylidene content, ensuring minimal degradation and improved adhesion and sealing properties at high processing speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If high processing temperatures are used in extrusion coating, then the polymer melts properly for coating, but degradation and cross-linking of LDPE occurs
Solution Approach 1:
The patent changes the molecular structure parameters of LDPE by controlling the vinylidene content to at least 15/100 kC and maintaining a broad molecular weight distribution (Mw/Mn > 10). These parameter changes enable the polymer to withstand extrusion temperatures without degradation, as the specific molecular architecture provides thermal stability while maintaining processability.
2Reliability
If antioxidants are added to prevent cross-linking, then polymer degradation is reduced, but adhesion performance deteriorates
Solution Approach 1:
The patent extracts antioxidants from the composition entirely, using a pure LDPE formulation without any additive packages. The invention relies on the inherent molecular properties of the LDPE (vinylidene content and molecular weight distribution) to provide stability, eliminating the need for antioxidants that would compromise adhesion.
Solution Approach 2:
The patent changes the molecular structure parameters of LDPE by controlling the vinylidene content to at least 15/100 kC and maintaining a broad molecular weight distribution (Mw/Mn > 10). These parameter changes enable the polymer to withstand extrusion temperatures without degradation, as the specific molecular architecture provides thermal stability while maintaining processability.
3Reliability
If cross-linking occurs during extrusion, then polymer stability increases, but melt flow rate decreases drastically
Solution Approach 1:
The patent changes the molecular structure parameters of LDPE by controlling the vinylidene content to at least 15/100 kC and maintaining a broad molecular weight distribution (Mw/Mn > 10). These parameter changes enable the polymer to withstand extrusion temperatures without degradation, as the specific molecular architecture provides thermal stability while maintaining processability.
4Productivity
If high line speeds are used in extrusion coating, then productivity increases, but polymer degradation occurs
Solution Approach 1:
The patent changes the molecular structure parameters of LDPE by controlling the vinylidene content to at least 15/100 kC and maintaining a broad molecular weight distribution (Mw/Mn > 10). These parameter changes enable the polymer to withstand extrusion temperatures without degradation, as the specific molecular architecture provides thermal stability while maintaining processability.
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 LDPE composition retains its original melt flow rate and enhances adhesion and hot tack strength, allowing for high-speed extrusion coating and heat sealing with a low sealing initiation temperature, improving processing efficiency and product quality.
Implementation Method 1
maintaining a high melt flow rate and vinylidene content, ensuring minimal degradation
Implementation Method 2
enhances adhesion and hot tack strength
Implementation Method 3
applying heat to the surfaces to be joined to soften or melt them
Implementation Method 4
applying heat to the surfaces to be joined to soften or melt them
Implementation Method 5
applying some pressure to the place where they need to be joined
Implementation Method 6
The polymer is extruded onto the moving substrate through a flat die
Data Source
AI summary
The present invention relates to the use of a at least a part of a polymer layer comprising a composition (Co), the composition comprising a low density polyethylene (LDPE) produced in a tubular reactor which composition is free of additives as a thermoplastic surface of an extrusion coated structure comprising the polymer layer and a first substrate for preparing heat-sealed articles by heat-sealing of said thermoplastic surface with a second substrate; and The use of a at least a part of a polymer layer comprising a composition (Co), the composition comprising a low density polyethylene (LDPE) havinga melt flow rate (MFR) according to ISO 1133 (190° C., 2.16 kg) higher than 3.0 g/10 min;a molecular weight distribution Mw/Mn which is greater than 10; anda vinylidene content which is at least 15/100 k C; which composition is free of additives as a thermoplastic surface of an extrusion coated structure comprising the polymer layer and a first substrate for preparing heat-sealed articles by heat-sealing of said thermoplastic surface with a second substrate.