LDPE Composition for High Density Extrusion Coatings
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Solution Overview
Problem
There is a need for polyethylene homopolymer compositions that achieve a balance of processing, density, and end-use performance in extrusion coatings, particularly for higher density applications beyond what can be reached with single autoclave-based resins, while maintaining good coating performance and minimizing substrate delamination.
Innovation Solution
A composition comprising a first polyethylene homopolymer and a second polyethylene homopolymer, both formed by high-pressure free-radical polymerization, with specific melt index and density ranges, where the second polymer has a density greater than or equal to 0.924 g/cc and is present in 60-95 weight percent, and the first polymer has a melt index less than 2.5 dg/min, allowing for higher density and improved barrier properties without compromising coating performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If autoclave-based LDPE resins are used to achieve higher density, then density is improved, but coating performance and adhesion are compromised
Solution Approach 1:
The patent combines two different polyethylene homopolymers (autoclave-based and tubular reactor-based) into a composite composition. The autoclave-based polymer provides higher density while the tubular reactor-based polymer contributes broad MWD and high melt strength, achieving a balance that neither component could achieve alone.
Solution Approach 2:
The patent carefully controls the density parameter of the autoclave-based polymer within a specific range (0.915-0.925 g/cc) and the blend ratio parameters to achieve the desired overall density (0.920-0.930 g/cc) while maintaining coating performance.
2Reliability
If tubular reactor LDPE resins are used, then coating performance is improved, but density is limited to lower values
Solution Approach 1:
The patent creates a composite composition by blending tubular reactor LDPE (providing coating performance) with autoclave-based LDPE (providing higher density), achieving a synergistic effect where the final composition exceeds the density capability of tubular reactor resins alone.
Solution Approach 2:
The blended composition serves multiple functions simultaneously: it provides the broad MWD and high melt strength needed for coating performance from the tubular component, while the autoclave component contributes higher density and improved barrier properties, making the composition versatile for various applications.
3Quantity of substance
If blends of LDPE with LLDPE or HDPE are used to achieve higher density, then density is improved, but adhesion and delamination properties are compromised
Solution Approach 1:
The patent uses two polyethylene homopolymers that are chemically homogeneous (both are polyethylene) rather than blending with different polymer types like LLDPE or HDPE. This maintains the homogeneous chemical structure needed for good adhesion while achieving higher density through physical blending.
Solution Approach 2:
The patent creates a composite of two compatible polyethylene homopolymers with different density characteristics, avoiding the use of incompatible polymer types that would cause delamination issues while still achieving the desired density enhancement.
4Productivity
If higher melt index resins are used to improve processing, then processing is improved, but melt strength is reduced
Solution Approach 1:
The patent controls the melt index parameter of the autoclave-based polymer within a specific range (2.0-10.0 dg/min) and optimizes the blend ratio to achieve the desired overall melt index (2.0-5.0 dg/min) while maintaining adequate melt strength for coating performance.
Solution Approach 2:
The blended composition combines polymers with different melt indices to create a composite with balanced processing and melt strength properties, where the tubular reactor component contributes high melt strength and the autoclave component provides appropriate melt index for processing.
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 composition achieves higher achievable densities with balanced melt index and melt strength, leading to enhanced coating performance and reduced extractable levels, suitable for critical food contact applications, and allows for flexibility in component selection to achieve desired properties.
Implementation Method 1
a first polyethylene homopolymer formed by a high pressure, free-radical polymerization process, and a second polyethylene homopolymer formed by a high pressure, free-radical polymerization process
Data Source
Figure 1A~1B
Figure 2
Figure 3
AI summary
The present invention relates to a composition comprising a first ethylene-based polymer, formed by a high pressure, free-radical polymerization process, and a second ethylene-based polymer, formed by a high pressure, free-radical polymerization process, such composition comprising the following properties: a) a melt index (12) from 2.0 to 10 dg/min; b) a density from 0.922 to 0.935 g/cc; and wherein the second ethylene-based polymer is present in an amount from 60 to 95 weight percent, based on the sum of the weight of the first ethylene-based polymer and the second ethylene-based polymer; and wherein the second ethylene-based polymer has a density greater than, or equal to, 0.924 g/cc; wherein the first ethylene-based polymer has a melt index less than 2.5 dg/min; and wherein the ratio of the density of the second polymer to the density of the first polymer is greater than, or equal to 1.007.