Cellulose Ether Substituent Distribution for Extrusion Gel Strength
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Solution Overview
Problem
Existing cellulose ethers used in extrusion molding of inorganic masses, such as ceramic-forming materials, exhibit low gel strength and wet green modulus, which limits the production of thin-walled honeycomb structures and increases production failures due to their low storage modulus and thermal gelation properties.
Innovation Solution
Development of novel cellulose ethers with specific substituent distributions and substitution levels, including methyl, hydroxyalkyl, and optional alkyl groups, which provide higher gel strength and viscosity, allowing for improved wet green modulus and thermal stability, thereby enhancing the extrusion process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If methyl cellulose is used as a binder/plasticizer, then green strength is improved, but gelation temperature is too low causing extrusion pressure rise
Solution Approach 1:
The patent changes the chemical parameters of the cellulose ether by introducing hydroxyalkyl groups (such as hydroxypropyl) in addition to methyl groups, creating a composite substitution pattern that raises the gelation temperature from around 30°C to above 35°C while preserving green strength properties
Solution Approach 2:
The invention creates a composite cellulose ether molecule with multiple types of ether substituents (methyl and hydroxyalkyl groups) to combine the beneficial properties of different substituents, achieving both high green strength and elevated gelation temperature
2Temperature
If hydroxyalkyl methylcelluloses are used to raise gelation temperature, then working temperature can be increased, but storage modulus decreases
Solution Approach 1:
The patent optimizes the concentration of hydroxyalkyl substituents to a specific range (0.1-0.5 molar substitution) to minimize the negative impact on storage modulus while still achieving the desired gelation temperature elevation, rather than using high concentrations that would severely reduce gel strength
3Strength
If high concentration of hydroxyalkyl methylcellulose is used to form gels, then gel strength is improved, but more material is needed increasing cost
Solution Approach 1:
The patent modifies the chemical structure parameters by controlling the type and amount of ether substituents, which changes the gelation behavior to achieve adequate gel strength at lower concentrations compared to conventional hydroxyalkyl methylcelluloses
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 novel cellulose ethers demonstrate significantly higher storage modulus and gel strength compared to traditional hydroxyalkyl methylcelluloses, enabling the production of extrusion-molded bodies with improved green strength and thermal stability, suitable for applications like catalyst carriers, heat exchangers, and filters.
Implementation Method 1
Methyl cellulose in the extrusion molding of inorganic masses is desired for improving the wet green modulus and wet green strength of the extruded mass... the well-known low gelation temperature of methyl cellulose has disadvantages in some processes for extrusion-molded bodies
Implementation Method 2
Methyl cellulose in the extrusion molding of inorganic masses is desired for improving the wet green modulus and wet green strength of the extruded mass
Data Source
AI summary
Cellulose ethers are described which are useful in compositions for extrusion-molded bodies. In these cellulose ethers the ether substituents are methyl groups, hydroxyalkyl groups, and optionally alkyl groups being different from methyl, the cellulose ether has an MS (hydroxyalkyl) of 0.11 to 1.00, and hydroxy groups of anhydroglucose units are substituted with methyl groups such that [s23/s26−0.2*MS (hydroxyalkyl)] is 0.35 or less, wherein s23 is the molar fraction of anhydroglucose units wherein only the two hydroxy groups in the 2- and 3-positions of the anhydroglucose unit are substituted with methyl groups and wherein s26 is the molar fraction of anhydroglucose units wherein only the two hydroxy groups in the 2- and 6-positions of the anhydroglucose unit are substituted with methyl groups.