Multimodal Polyethylene Pipe Composition Pressure Resistance

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Solution Overview

Problem

Current polyethylene compositions for pressure pipes face challenges in achieving improved pressure resistance and preventing sagging, particularly in large diameter pipes, due to compatibility issues with ultrahigh molecular weight polyethylene (UHMWPE) and limitations in maintaining uniform dimensions during manufacturing.

Innovation Solution

A multimodal ethylene polymer composition comprising a high density multimodal polyethylene component, optionally blended with UHMWPE, with specific density and molecular weight distribution characteristics, and a process for producing pipes using this composition to enhance pressure resistance and prevent sagging.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If UHMW polyethylene is added to improve mechanical properties and pressure resistance, then strength and pressure resistance are improved, but compatibility problems arise and long blending times are required

Engineering Contradiction:

Improvepressure resistanceVSAvoidblending time

Core Design Contradiction:

StrengthVSEase of manufacture

Solution Approach 1:

The UHMW polyethylene is pre-granulated before blending with the HDPE matrix. This preliminary granulation step prepares the UHMW particles in advance, enabling better distribution and compatibility during the extrusion process without requiring excessively long blending times

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent specifies controlling the molecular weight of UHMW polyethylene within a particular range and limiting its content to 5-50 wt% of the total composition. These parameter optimizations balance the improvement in pressure resistance with acceptable processing characteristics and blending efficiency

Inventive Principle:

Principle #35Parameter changes

2Strength

If molecular weight is increased to improve mechanical properties, then strength is improved, but viscosity ratio increases and homogeneity is lost

Engineering Contradiction:

Improvemechanical propertiesVSAvoidhomogeneity

Core Design Contradiction:

StrengthVSStability of the object's composition

Solution Approach 1:

The patent optimizes the molecular weight of UHMW polyethylene within a specific range and controls its content at 5-50 wt% of the total composition. This parameter optimization ensures that the high molecular weight component provides improved mechanical strength while maintaining acceptable homogeneity and viscosity ratio in the multimodal polyethylene composition

Inventive Principle:

Principle #35Parameter changes

3Strength

If UHMW polyethylene content is increased to improve pressure resistance, then strength is improved, but UHMW particles remain in large separate domains without melting into the matrix

Engineering Contradiction:

Improvepressure resistanceVSAvoidparticle distribution

Core Design Contradiction:

StrengthVSShape

Solution Approach 1:

The UHMW polyethylene is pre-granulated before blending, which prepares the particles for better distribution during extrusion. This preliminary preparation helps achieve more uniform dispersion in the HDPE matrix while maintaining the pressure resistance benefits of UHMW

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent limits UHMW polyethylene content to 5-50 wt% and specifies a particular molecular weight range. These parameter controls ensure sufficient UHMW content for improved pressure resistance while preventing excessive particle aggregation and maintaining adequate melting and distribution in the matrix

Inventive Principle:

Principle #35Parameter changes

4Stability of the object's composition

If pipe wall thickness is increased to prevent sagging, then sagging resistance is improved, but manufacturing complexity and dimensional uniformity become problematic

Engineering Contradiction:

Improvesagging resistanceVSAvoiddimensional uniformity

Core Design Contradiction:

Stability of the object's compositionVSManufacturing precision

Solution Approach 1:

The patent optimizes the molecular weight and content of UHMW polyethylene to achieve improved sagging resistance through material properties rather than simply increasing wall thickness. This approach maintains dimensional uniformity while providing adequate sagging resistance

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite multimodal polyethylene system combining HDPE and UHMW polyethylene. This composite material provides enhanced sagging resistance through the high molecular weight component's viscosity characteristics, allowing thinner walls with uniform dimensions compared to conventional single-component polyethylene pipes

Inventive Principle:

Principle #40Composite materials

Data Source

PatentUS9920190B2Multimodal polyethylene composition with high pressure resistance

Publication Date: 2018.03.20 BOREALIS AG

AI summary

The present invention relates to a multimodal polyethylene composition which can be manufactured into pipes showing improved pressure resistance comprising a high density multimodal ethylene polymer component (A) having a density of at least 930 kg/m3, and a MFR21 of not more than 15 g/10 min, wherein said composition exhibits a LAOS-NLF defined asL⁢⁢A⁢⁢O⁢⁢S-N⁢⁢L⁢⁢F=G1′G3′where G1′—first order Fourier CoefficientG3′—third order Fourier Coefficientof at least 1.7. Such a polyethylene composition is useful for the manufacture of pressure pipes that exhibit improved pressure resistance and creep resistance and do not undergo sagging. Further disclosed is a process for the production of a pipe using such a multimodal polyethylene composition and a pipe comprising such a multimodal polyethylene composition.