Carboxymethyl Starch Binder for Moulding Sand Strength
Solution Overview
Problem
Current moulding sand compositions with biopolymers often require multiple components, which complicates preparation, increases costs, and may have negative environmental impacts, while also failing to achieve optimal strength and durability parameters.
Innovation Solution
A single-component moulding sand using biodegradable sodium salt of carboxymethyl starch (CMS-Na) as both a binder and additive, combined with silica sand and water, simplifies the composition and enhances binding properties without the need for auxiliary substances, allowing for improved strength and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If native starch is used as a binder in moulding sand, then hardness and durability are improved, but liquidity and resistance to erosion and metal penetration deteriorate
Solution Approach 1:
The patent applies parameter changes by modifying the chemical structure of native starch through carboxymethylation. This chemical modification transforms the starch molecules by introducing carboxymethyl groups, which fundamentally alters the physical and chemical properties of the binder. The degree of substitution (DS) is controlled to optimize the balance between binding strength and erosion resistance, resolving the contradiction between improved hardness and maintained liquidity/erosion resistance.
Solution Approach 2:
The patent creates a composite material system by combining carboxymethyl starch with bentonite and other moulding sand components. This composite approach leverages the complementary properties of different materials: carboxymethyl starch provides enhanced binding strength and durability, while bentonite contributes to liquidity and erosion resistance. The synergistic interaction between these components resolves the technical contradiction by distributing functions across multiple materials.
2Reliability
If multiple components are used in moulding sand composition, then functional properties are improved, but preparation complexity and costs increase
Solution Approach 1:
The patent applies universality by designing carboxymethyl starch as a multi-functional binder that simultaneously provides binding strength, durability, and erosion resistance. This single modified biopolymer performs multiple functions that traditionally required several different additives and binders. By consolidating these functions into one material, the patent reduces preparation complexity while maintaining or improving functional properties.
Solution Approach 2:
The patent uses parameter changes to optimize the properties of carboxymethyl starch so that it can replace multiple components. By carefully controlling the degree of substitution and molecular weight parameters during starch modification, the binder achieves a optimal balance of properties that eliminates the need for several auxiliary substances, thereby simplifying the overall composition and preparation process.
3Strength
If synthetic additives are used to reduce mould friability, then strength is improved, but environmental impact increases
Solution Approach 1:
The patent applies this principle by using a biodegradable material (carboxymethyl starch) that can be easily broken down and returned to the environment. Unlike persistent synthetic additives, the modified starch serves its binding function and then degrades naturally, eliminating long-term environmental contamination. This approach maintains mould strength during use while ensuring environmental safety after disposal.
Solution Approach 2:
The patent converts the potential harm of using organic materials (which might be perceived as weaker than synthetics) into a benefit by selecting carboxymethyl starch that provides both the required strength and biodegradability. The organic nature of the modified starch, which could be seen as a disadvantage for strength, is transformed into an advantage for environmental compatibility, while chemical modification ensures adequate mechanical properties are achieved.
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 CMS-Na moulding sand exhibits superior binding properties, reduces friability, and supports the production of high-quality castings with improved tensile and bending strengths, while being environmentally friendly and cost-effective, with the ability to control properties through degree of substitution and viscosity.
Implementation Method 1
a binder for 'connecting' the grains of the matrix
Implementation Method 2
The moulding sand consists of a binder in the form of a biodegradable modified starch, in this case the sodium salt of carboxymethyl starch (CMS-Na), and a solvent, in this case water
Implementation Method 3
The moulded pieces were subjected to curing under the influence of microwave radiation with power of 800W and frequency of 2.45 GHz for 120s
Data Source
Figure 1
AI summary
A moulding sand comprising water, a binder and a silica sand matrix, characterised in that it further comprises sodium salt of carboxymethyl starch (CMS-Na) having a degree of substitution (DS) in the range of 0.2 to 0.9, in the amount of 0.2 to 2.5 parts by weight per 100 parts by weight of the matrix.