Powder Injection Molding Binder Removal via Solvent Extraction
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Solution Overview
Problem
Current methods for producing metallic moldings through powder injection molding are slow and prone to deformation due to the lengthy binder removal processes, which can lead to oxidation of metal powders and compromised part quality.
Innovation Solution
A method combining solvent debinding with subsequent thermal debinding in an oxygen-containing atmosphere using a thermoplastic mass containing sinterable metal powder and a polyoxymethylene-based binder system, where the binder components are extracted with a solvent and then thermally treated at 140-200°C to remove at least 20% of the binder by weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If complete thermal debinding is used to remove the binder, then the binder is completely removed, but the process takes 1 to 3 days and causes deformation of the molded parts
Solution Approach 1:
The binder removal process is divided into two distinct stages: first, solvent extraction removes the soluble binder component (30-70% by volume) to create channels and reduce binder content; second, thermal debinding removes the remaining insoluble binder component. This segmentation allows each stage to be optimized independently, reducing total process time from 1-3 days to 0.5-1 day while maintaining complete binder removal.
Solution Approach 2:
A solvent is introduced as an intermediary substance to selectively extract the soluble binder component from the green body before thermal debinding. This intermediary step creates a porous structure that facilitates faster subsequent thermal debinding and prevents deformation by reducing binder content prior to the thermal process.
2Strength
If the green parts are stored in a powder bed for melting to maintain green strength, then the green strength is maintained, but the process becomes more complex and time-consuming
Solution Approach 1:
The soluble binder component is extracted from the green body using a solvent, removing the need for powder bed storage during melting. This extraction approach maintains green strength by selectively removing only the soluble portion while preserving the structural integrity provided by the insoluble binder component.
3Reliability
If a multi-component binder system is used for thermal debinding, then the binder components are gradually released during heating, but the process is still slow and deformation is unavoidable
Solution Approach 1:
The binder system is segmented into soluble and insoluble components that are removed in sequence rather than simultaneously. The soluble component is extracted first by solvent, creating channels and reducing overall binder content, which accelerates the subsequent thermal debinding of the insoluble component and prevents deformation.
Solution Approach 2:
The removal mechanism is changed from purely thermal decomposition to a combination of solvent extraction followed by thermal debinding. This parameter change in the removal process allows for faster binder elimination while maintaining control over the debinding sequence.
4Loss of time
If solvent extraction is used to remove the soluble binder component, then the residual debinding time is reduced to 0.5 to 1 day, but the binder system must contain 30 to 70% by volume of the soluble polymer
Solution Approach 1:
The binder system composition is optimized to contain a specific range (30-70% by volume) of soluble binder component that can be effectively extracted by solvent. This parameter optimization ensures sufficient soluble content for effective solvent extraction while maintaining adequate insoluble content to preserve green strength and structural integrity during processing.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach results in metallic moldings with improved quality and integrity, reducing oxidation and deformation, and allowing for faster binder removal without compromising the structural integrity of the sintered parts.
Implementation Method 1
the molded part is treated with a solvent which extracts the binder components B 2 ) and optionally C) from the molded part and in which the binder component B 1) is insoluble
Implementation Method 2
then the solvent is removed from the molded part by drying
Implementation Method 3
the molding is thermally treated at 140 - 200 ° C, preferably 140 - 170 ° C in an oxygen-containing atmosphere, whereby the binder component B 1) is at least 20% by weight, preferably at least 50% by weight, very preferably at least 85% by weight, is removed from the molded part
Data Source
Figure 1
AI summary
Process for producing a shaped metallic body from a thermoplastic composition by injection molding or extrusion to form a shaped part, removal of the binder and sintering, wherein a thermoplastic composition composed of a metal powder and a polymer mixture B1) and B2) based on a polyoxymethylene homopolymer or copolymer B1) is used as binder and to remove the binder a) the shaped part is treated with a solvent which extracts the binder component B2) from the shaped part and in which the binder component B1) is insoluble, b) the solvent is then removed from the shaped part by drying and c) the shaped part is treated thermally at from 140 to 200°C in an oxygen- comprising atmosphere, as a result of which the binder component B1) is removed from the shaped part; and also a shaped metallic body which can be obtained in this way.