Polyacetal Binder Composition for Thin Sintered Molding
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Solution Overview
Problem
Existing sintered molded body production methods using polyacetal resin binders face issues with low fluidity, leading to poor moldability, especially for thin sections, and risk cracking or swelling during degreasing due to rapid volatilization or reduced strength when fluidity is enhanced.
Innovation Solution
A composition comprising a polyacetal resin with a melt flow index of 70 to 200 g/10 min and a polyolefin resin with a melt flow index of 40 g/10 min or more, along with optional additives like fluidity imparting agents, nitrogen-containing compounds, and fatty acid metal salts, to maintain shape retention and prevent cracking or swelling during degreasing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a polyacetal resin is used as a binder to improve shape retention ability, then the rigidity and shape retention of green molded bodies are improved, but the fluidity of the feedstock decreases, resulting in poor moldability especially for thin portions
Solution Approach 1:
The patent changes the molecular weight parameter of the polyacetal resin by selecting a resin with a specific viscosity number range (2.0-4.0 dl/g) to achieve optimal balance between shape retention and fluidity. This parameter optimization allows the binder to maintain rigidity while improving feedstock flow characteristics for better moldability of thin portions
Solution Approach 2:
The patent creates a composite binder system by combining polyacetal resin with specific additives including polyethylene wax (5-20 parts by mass per 100 parts polyacetal resin) and poly-1,3-dioxepane (2-10 parts by mass per 100 parts polyacetal resin). This composite approach enhances fluidity while maintaining the shape retention properties of the polyacetal resin
2Ease of manufacture
If a flow aid such as wax is added in a large amount to increase the fluidity of the binder, then the moldability is improved, but rapid volatilization during degreasing occurs, causing cracking and swelling
Solution Approach 1:
The patent optimizes the concentration parameter of flow aids by limiting polyethylene wax to 5-20 parts by mass per 100 parts polyacetal resin and poly-1,3-dioxepane to 2-10 parts by mass per 100 parts polyacetal resin. This controlled dosing prevents rapid volatilization while maintaining adequate fluidity
Solution Approach 2:
The patent introduces poly-1,3-dioxepane as an intermediary substance that mediates between the polyacetal resin and polyethylene wax, controlling the degradation and volatilization behavior during degreasing to prevent cracking and swelling while maintaining fluidity
3Ease of manufacture
If the concentration of 1,3-dioxepane is increased to increase the fluidity of the polyacetal resin, then the fluidity is improved, but the strength of the polyacetal resin is lowered and the strength of the molded body is reduced
Solution Approach 1:
The patent optimizes the concentration parameter of 1,3-dioxepane by limiting it to 2-10 parts by mass per 100 parts polyacetal resin, achieving the optimal balance point where fluidity is sufficiently improved while the strength of the polyacetal resin and resulting molded body is maintained
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
The composition enables high fluidity and moldability, allowing for the production of thin sintered molded bodies with improved degreasability and high yield, while maintaining shape retention and preventing defects.
Implementation Method 1
This degreasing step employs either the method in which green molded bodies are heated to thermally decompose and gasify the binder
Implementation Method 2
the method in which green molded bodies are treated with a solvent to elute or remove a soluble binder component in the green molded bodies
Data Source
AI summary
An object of the present disclosure is to provide a composition for use in sintered molded bodies which does not impair the shape retention ability of a green molded body relying on the rigidity inherent to a polyacetal resin, has high fluidity, and is resistant to cracking or swelling during degreasing. The composition for use in sintered molded bodies contains a sinterable inorganic powder and an organic binder, the organic binder contains at least a polyacetal resin and a polyolefin resin, and the melt flow index of the polyacetal resin is 70 to 200 g/10 min.