Multimodal HDPE Composition with Saturated Amide Slip Agent
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Solution Overview
Problem
Existing HDPE compositions for moulded articles, such as caps and closures, face challenges in achieving a balance between low coefficient of friction for easy unscrewing and desirable mechanical properties like stiffness and impact resistance. Common slip agents like erucamide suffer from oxidation issues, while alternatives like PDMS require high amounts, affecting other properties and sustainability goals.
Innovation Solution
A polymer composition comprising 95.0 to 99.95 wt% of a multimodal high density polyethylene (HDPE) with specific density and MFR ranges, combined with 0.08 to 0.4 wt% of a saturated amide slip agent, which together provide an attractive low coefficient of friction and improved mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If erucamide slip agent is used to achieve low coefficient of friction, then ease of operation is improved, but reliability deteriorates due to oxidation causing unpleasant taste and odour
Solution Approach 1:
The patent changes the chemical parameters of the slip agent from unsaturated (erucamide) to saturated amides, fundamentally altering the molecular structure to eliminate oxidation susceptibility while maintaining slip functionality
Solution Approach 2:
The patent uses small amounts (0.01-0.5 wt%) of saturated amide slip agents that provide sufficient slip effect without requiring large quantities, making the solution economically viable and environmentally friendly
2Reliability
If saturated amide slip agent is used to avoid oxidation, then reliability is improved, but ease of operation worsens due to poorer slip effect and longer time to achieve desired friction
Solution Approach 1:
The patent optimizes the molecular weight and structure of saturated amides, selecting specific compounds (C16-C22 fatty acid amides) that provide both oxidation resistance and adequate slip effect
Solution Approach 2:
The patent creates a composite system combining multimodal HDPE with saturated amide slip agents, where the polymer matrix and slip agent work synergistically to achieve both mechanical properties and slip functionality
3Ease of operation
If PDMS is used as permanent slip agent for instant slip effect, then ease of operation is improved, but device complexity worsens due to high amounts required affecting other properties
Solution Approach 1:
The patent uses minimal quantities (0.01-0.5 wt%) of saturated amide slip agents that provide sufficient slip effect without requiring the high concentrations needed for PDMS, simplifying the overall composition
Solution Approach 2:
The patent changes the slip mechanism from permanent (PDMS) to time-dependent release of saturated amides, which provides adequate slip effect without compromising other material properties
4Strength
If HDPE density is increased to improve stiffness, then strength is improved, but ease of operation worsens due to increased weight affecting impact properties
Solution Approach 1:
The patent uses multimodal HDPE combining different molecular weight fractions (low, medium, high) that work synergistically to achieve both stiffness and impact resistance, creating a composite-like structure within a single polymer system
Solution Approach 2:
The patent optimizes the density range (955-975 kg/m³) and molecular weight distribution to achieve the optimal balance between stiffness and impact properties, avoiding both too low and too high density extremes
Data Source
AI summary
The invention provides a polymer composition comprising: (i) 95.0 to 99.95 wt%, relative to the total weight of the polymer composition, of a multimodal high density polyethylene (HDPE) with a density of 945 to 980 kg/m3 measured according to ISO 1183, and an MFR2 of 0.1 to 1.3 g/lOmin measured according to ISO 1133 at 190 °C and a load of 2.16 kg; and wherein the multimodal HDPE comprises at least two fractions: (A) 30 to 70 wt%, relative to the total weight of the multimodal HDPE, of a lower molecular weight fraction being a polyethylene with a density in the range of 955 to 980 kg/m3 measured according to ISO 1183 and an MFR2 of 100 to 600 g/10 min measured according to ISO 1133 at 190 °C and a load of 2.16 kg; and (B) 30 to 70 wt%, relative to the total weight of the multimodal HDPE, of a higher molecular weight fraction being a polyethylene with a density in the range of 930 to 960 kg/m3 measured according to ISO 1183 and an MFR2 of 0.0001 to 1.0 g/10 min measured according to ISO 1133 at 190 °C and a load of 2.16 kg; and (ii) 0.05 to 0.5 wt%, relative to the total weight of the polymer composition, of at least one saturated amide slip agent.