Injection-Moldable HMW Polyethylene for Medical Implants

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Solution Overview

Problem

There is a need for a high molecular weight polyethylene polymer that is capable of being injection molded for producing medical products while retaining its superior properties, such as biocompatibility and mechanical strength, to enable the production of smaller medical devices or more efficiently produce various medical products.

Innovation Solution

A high molecular weight polyethylene polymer with a melt flow index of greater than about 0.8 g/10 min and a Viscosity Number of greater than about 400 cm³/g is formulated to be biocompatible and suitable for injection molding, allowing the production of medical devices like implants and drug delivery devices.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If high molecular weight polyethylene polymer is used to achieve superior mechanical properties and biocompatibility, then the polymer exhibits improved abrasion resistance, impact strength, and wear resistance, but the polymer displays poor melt flow properties with a melt flow index of 0 grams per 10 mins, requiring special processing methods like pressure sintering and ram extrusion

Engineering Contradiction:

Improveimpact strengthVSAvoidmelt flow properties

Core Design Contradiction:

StrengthVSEase of manufacture

Solution Approach 1:

The patent modifies the molecular weight distribution parameters of polyethylene to create a bimodal distribution with both high and low molecular weight components. This parameter change allows the polymer to maintain high impact strength from the high molecular weight fraction while the low molecular weight fraction provides adequate melt flow for injection molding processes.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite polymer system by blending high molecular weight polyethylene (providing mechanical strength and biocompatibility) with low molecular weight polyethylene or polyethylene copolymers (providing processability). This composite approach combines the superior properties of high molecular weight polyethylene with the injection molding capabilities of lower molecular weight variants.

Inventive Principle:

Principle #40Composite materials

2Reliability

If high molecular weight polyethylene polymer is used to produce medical devices, then the polymer provides excellent biocompatibility and mechanical strength, but the special processing methods required reduce manufacturing efficiency and increase device complexity

Engineering Contradiction:

ImprovebiocompatibilityVSAvoidmanufacturing efficiency

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent adjusts the molecular weight distribution parameters to enable injection molding while maintaining biocompatibility. The bimodal distribution with controlled ratios of high and low molecular weight components allows standard injection molding processes to be used, significantly improving manufacturing efficiency over pressure sintering methods.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces complex special processing mechanical systems (pressure sintering equipment, ram extrusion machinery) with standard injection molding equipment. This substitution simplifies the manufacturing system while maintaining the ability to produce high molecular weight polyethylene medical devices with excellent biocompatibility.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Volume of moving object

If high molecular weight polyethylene polymer is used to create smaller medical devices, then the superior mechanical properties are maintained, but the difficulty of injection molding currently prevents this application

Engineering Contradiction:

Improvedevice sizeVSAvoidinjection molding capability

Core Design Contradiction:

Volume of moving objectVSEase of manufacture

Solution Approach 1:

The patent modifies the molecular weight distribution parameters to enable injection molding of small-scale devices. The bimodal distribution provides adequate melt flow for filling small mold cavities while maintaining the high molecular weight fraction necessary for mechanical strength and biocompatibility in the final small device.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentEP3949005B1Injection molded medical devices made from a high molecular weight polyethylene

Publication Date: 2025.07.16 CELANESE INTERNATIONAL CORP

AI summary

A high molecular weight polyethylene polymer is formulated so that the polymer is capable of being injection molded. The polyethylene polymer has a Viscosity Number of greater than about 400 ml/g and has a melt flow rate of greater than about 0.9 g/10 min. The polyethylene polymer is of high purity and is particularly well suited for producing medical products.