Extrusion Coating Polyethylene Composition for High Line Speed Stability
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Solution Overview
Problem
Current polyethylene compositions for extrusion coating face challenges in achieving both good mechanical properties and processability, particularly at high line speeds, with issues such as excessive neck-in, instability, and reduced adhesion to certain substrates like OPP films.
Innovation Solution
A polyethylene composition blend comprising a long-chain branched low-density polyethylene and a bimodal metallocene-based linear low-density polyethylene terpolymer, combined with a non-thermoplastic filler, which optimizes rheological properties for improved processability and adhesion at high line speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If LDPE content is increased to improve processability, then processability is improved, but mechanical properties such as toughness and abrasion resistance are reduced
Solution Approach 1:
The patent applies parameter changes by precisely controlling the LDPE content within 5-30 wt% range and adjusting the MFR2 value to 6.5-10.0 g/10min, along with controlling density and phase shift parameters. This optimized parameter combination resolves the contradiction by achieving sufficient processability while preserving mechanical properties through precise parameter optimization rather than extreme values.
Solution Approach 2:
The patent creates a composite polymer system by blending LDPE with LLDPE, where each component contributes its strengths. The LLDPE provides mechanical strength and barrier properties while the LDPE contributes processability. This composite approach resolves the contradiction by combining materials with complementary properties rather than relying on a single polymer type.
2Strength
If LDPE content is decreased to preserve mechanical properties, then mechanical properties are improved, but processability deteriorates with excessive neck-in and instability
Solution Approach 1:
The patent resolves this contradiction by changing multiple parameters simultaneously: controlling LDPE content (5-30 wt%), MFR2 (6.5-10.0 g/10min), density (920 kg/m³), and phase shift relationships. This multi-parameter optimization ensures that even with low LDPE content, the blend achieves sufficient processability while maintaining mechanical properties.
Solution Approach 2:
The patent uses the LLDPE component as an intermediary that bridges the gap between mechanical properties and processability. The LLDPE provides a matrix that maintains mechanical strength while the controlled amount of LDPE acts as a processability enhancer, mediating between the two opposing requirements.
3Productivity
If high line speed is used to increase productivity, then productivity is improved, but coating quality deteriorates with neck-in and draw down issues
Solution Approach 1:
The patent applies parameter changes by optimizing the rheological properties through controlled LDPE content and MFR2 values. This creates a melt flow characteristics that remains stable across a wide range of line speeds, allowing high productivity while maintaining coating quality with minimal neck-in and consistent draw down.
Solution Approach 2:
The patent creates a dynamically adaptable polymer blend that responds appropriately to varying processing conditions. The controlled composition allows the melt to maintain stability at low line speeds while adapting to high line speeds without breaking or excessive neck-in, enabling flexible production at optimal productivity levels.
Data Source
AI summary
Extrusion coating polyethylene compositions A), comprising B) a polymer blend comprising a) 5 wt% - 60 wt% of a long chain branched, low-density polyethylene, having - a melt index MFR2 of 2.5 to 10.0 g/10 min, according to ISO 1133, - a density of 910 to 935 kg/m3, according to ISO 1183-1987, and - a dynamic viscosity η0.05 (190°C) at a shear rate of 0.05 rad/s and a dynamic viscosity η300 rad/s (190°C) which satisfy the following relationship: η300≤108Pa*s+0.0253*η0.05 and/or - a phase shift δ0.5 (190°C) at a frequency of 0.5 rad/s and a phase shift δ300 (190°C) at a frequency of 300 rad/s, which satisfy the following relationship: tan δ300≥0.45+0.164*tan δ0.05 and b) 95 wt% - 40 wt% of a bimodal metallocene-based linear low density polyethylene terpolymer having a melt index MFR2 of from 3 to 40 g/10 min, according to ISO 1133, and a density of from 900 to 935 kg/m3, according to ISO 1183-1987, which has been produced by polymerising ethylene and two alpha-olefin comonomers having from 4 to 10 carbon atoms in at least two polymerisation stages in the presence of a metallocene catalyst. and C) 1wt% - 50wt% based on the total weight of the polymer blend B) of a non-thermoplastic filler and extrusion coating polyethylene compositions D, comprising 40 - 60 wt% of the polyethylene composition A), and 60 - 40 wt% of polymer blend B and their use.