Metallocene Polyethylene Resin for Injection-Molded Fuel Tanks
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Solution Overview
Problem
Current injection-molded polyethylene fuel tanks lack the necessary mechanical properties such as environmental stress cracking resistance, creep resistance, and impact resistance to meet safety standards like ECE34, and existing polyethylene grades for injection molding do not fulfill these requirements.
Innovation Solution
The development of injection-molded articles using a metallocene-catalyzed polyethylene resin comprising two fractions with specific melt indices and densities, which are injection-molded to achieve improved mechanical properties and processability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional polyethylene grades are used for injection molding, then the manufacturing process is simple and cost-effective, but the mechanical properties (ESCR, impact resistance, creep resistance) do not meet safety standards
Solution Approach 1:
The patent changes the molecular weight distribution parameters of polyethylene by using metallocene catalysts to produce multimodal distributions. This creates specific fractions with different melt indices (MI2 ≥ 100.0 g/10 min and MI105 ≥ 13.0 g/10 min) and density (≥ 0.940 g/cm³), which simultaneously improve mechanical properties and maintain processability for injection molding
Solution Approach 2:
The patent creates a composite polyethylene resin composition comprising multiple fractions (A and B) with different molecular weights and properties. Fraction A has higher melt index while fraction B has lower melt index, creating a composite material that combines the advantages of both fractions to achieve both good mechanical properties and processability
2Reliability
If wall thickness is increased to meet impact and creep resistance, then safety performance improves, but the tank volume to wall thickness ratio decreases and manufacturing complexity increases
Solution Approach 1:
The patent changes the material parameters (melt index, density, molecular weight distribution) to achieve superior mechanical properties, allowing thinner walls to meet safety standards. This enables complex geometric structures to be manufactured with adequate wall thickness that maintains both safety performance and manufacturing feasibility
3Adaptability or versatility
If injection molding is used instead of blow molding, then geometric complexity increases, but the physical properties (warpage, shrinkage control) become problematic
Solution Approach 1:
The patent optimizes the resin parameters (melt index MI2 ≥ 100.0 g/10 min, density ≥ 0.940 g/cm³, multimodal molecular weight distribution) specifically for injection molding. These parameter changes enable the material to flow and cool uniformly, producing complex geometries with low warpage and shrinkage while maintaining high manufacturing precision
Data Source
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AI summary
The present invention relates to an injection-molded article, comprising at least one metallocene-catalyzed polyethylene resin comprising at least two metallocene-catalyzed polyethylene fractions A and B, wherein the at least one metallocene-catalyzed polyethylene resin comprises: at least 40 % to at most 50 % by weight of polyethylene fraction A based on the total weight of the at least one metallocene-catalyzed polyethylene resin, wherein fraction A has a melt index MI2 of at least 100.0 g/10 min as determined according to ISO 1133, condition D, at 190 °C and under a load of 2.16 kg; and wherein the at least one metallocene-catalyzed polyethylene resin has a density of at least 0.940 g/cm3 to at most 0.950 g/cm3 as measured on pellets according to ISO 1183 at 23 °C; a melt index MI2 of at least 1.4 g/10 min to at most 2.5 g/10 min as measured on pellets according to ISO 1133, condition D, at 190 °C and under a load of 2.16 kg. The present invention also relates to a process for preparing said injection-molded article, comprising the steps of a) providing at least one metallocene-catalyzed polyethylene resin as described herein; and b) injection-molding said polyethylene resin into an article.