Polyethylene Homopolymer Composition Barrier Properties
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Solution Overview
Problem
Current polyethylene homopolymer compositions for films and closures lack optimal barrier properties and molecular weight distribution for advanced end-use applications, particularly in high environmental resistance and processing efficiency.
Innovation Solution
A new polyethylene homopolymer composition comprising a first ethylene homopolymer with a low melt index and a second ethylene homopolymer with a high melt index, both made using single-site catalysts in solution polymerization, with a specific molecular weight distribution and density range, optionally nucleated with dicarboxylic acid salts, to enhance barrier properties and processing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a polyethylene homopolymer composition is used to achieve good barrier properties, then oxygen and water vapor transmission rates are reduced, but the composition requires precise control of molecular weight distribution and melt index ratios which increases manufacturing complexity
Solution Approach 1:
The patent applies parameter changes by precisely controlling the molecular weight distribution (Mw/Mn ratio between 2.0-5.0), melt index values (I21: 0.01-10 g/10 min, I22: 500-5000 g/10 min), and density ranges (d1: 0.943-0.975 g/cm³, d2: 0.950-0.985 g/cm³) of the two ethylene homopolymer components to achieve optimal barrier properties while maintaining manufacturability through defined specification ranges
2Object-affected harmful factors
If two ethylene homopolymer components with different melt indices are combined to improve barrier properties, then oxygen transmission rates are reduced, but the complexity of specifying and controlling multiple parameters increases
Solution Approach 1:
The patent segments the polyethylene composition into two distinct homopolymer components, each with specific melt index ranges (first component: I21 of 0.01-10 g/10 min, second component: I22 of 500-5000 g/10 min) and density ranges, allowing independent optimization of each component's properties while achieving synergistic barrier performance when combined
Solution Approach 2:
The patent controls multiple parameters including molecular weight distribution (Mw/Mn of 2.0-5.0 for each component), density (d1: 0.943-0.975 g/cm³, d2: 0.950-0.985 g/cm³), and melt index ratios (I22/I21 of 50-500) to optimize the balance between processing performance and barrier properties
3Productivity
If the weight average molecular weight is kept low (≤75,000) to improve processing efficiency, then manufacturing performance is enhanced, but the barrier properties may be compromised
Solution Approach 1:
The patent optimizes the weight average molecular weight (Mw ≤75,000) while simultaneously controlling the molecular weight distribution (Mw/Mn of 2.0-5.0) and melt index characteristics to achieve a balance where low molecular weight provides good processing efficiency while the controlled distribution and melt index ratio maintain adequate barrier properties
Data Source
AI summary
A polyethylene homopolymer composition comprises: a first ethylene homopolymer having a density, d1 of from 0.943 to 0.975 g/cm3, a melt index, I21 of from 0.01 to 10 g/10 min, and a molecular weight distribution, Mw/Mn of less than 3.0; and a second ethylene homopolymer having a density, d2 of from 0.950 to 0.985 g/cm3, a melt index, I22 of at least 500 g/10 min, and a molecular weight distribution, Mw/Mn of less than 3.0; wherein the ratio of the melt index, I22 of the second ethylene homopolymer to the melt index, I21 of the first ethylene homopolymer is at least 50. The polyethylene homopolymer compositions which may be nucleated have a weight average molecular weight, Mw of ≤75,000, a high load melt index, I21 of at least 200 g/10 min, a molecular weight distribution, Mw/Mn of from 4.0 to 12.0 and may be usefully employed in molding applications, such as, for example, in compression molded closures.