Esterified Cellulose Ether Viscosity Control via Diluent Feeding
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Solution Overview
Problem
Esterified cellulose ethers with high molecular weight exhibit high viscosity when dissolved in organic solvents, making them inefficient for coating processes due to the need for high concentrations, which complicates spray-drying and coating applications.
Innovation Solution
Optimizing the ratio of molecular weight and viscosity by feeding a reaction diluent at different stages during the production of esterified cellulose ethers, allowing the esterification reaction to proceed while controlling viscosity and maintaining high molecular weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high molecular weight esterified cellulose ethers are produced, then resistance against gastric juice and bioavailability enhancement are improved, but viscosity in organic solvents increases making coating processes inefficient
Solution Approach 1:
The patent changes the chemical structure parameters of the cellulose ether by introducing aromatic carboxylic acid ester groups (such as phthalate, terephthalate, isophthalate esters) in addition to the usual aliphatic ester groups. This structural modification allows achieving high molecular weight ( Mw ≥ 200,000) while maintaining low viscosity in organic solvents like acetone, thus resolving the contradiction between reliability (gastric resistance) and ease of operation (coating efficiency).
Solution Approach 2:
The patent creates a composite esterified cellulose ether containing both aliphatic ester groups (acetate, propionate, butyrate) and aromatic ester groups (phthalate, terephthalate, isophthalate). This composite structure combines the benefits of high molecular weight for gastric resistance with the low viscosity characteristics of aromatic esters in organic solvents, enabling both enteric coating performance and efficient spray-drying application.
2Productivity
If high concentration solutions are used for coating, then coating efficiency is improved, but viscosity increases complicating spray-drying and coating applications
Solution Approach 1:
The patent modifies the chemical composition by incorporating aromatic carboxylic acid ester groups which fundamentally change the solvent interaction parameters. This allows the polymer to maintain low viscosity even at high concentrations in organic solvents, thus enabling both high coating efficiency and ease of spray-drying application without the usual viscosity penalty.
3Reliability
If molecular weight is increased to enhance bioavailability, then drug absorption is improved, but viscosity increases reducing processing efficiency
Solution Approach 1:
The patent produces a composite esterified cellulose ether with both aliphatic and aromatic ester groups. The aromatic ester components contribute to low viscosity in organic solvents, while the high molecular weight (achieved through controlled esterification) provides enhanced bioavailability. This composite structure allows simultaneous optimization of both drug absorption and processing efficiency.
Solution Approach 2:
The patent changes the esterification parameters by using aromatic carboxylic acids (phthalic, terephthalic, isophthalic acids) in addition to aliphatic acids. This chemical parameter change results in polymers with high molecular weight that surprisingly maintain low viscosity in organic solvents, thus improving bioavailability without sacrificing processing efficiency.
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 process results in esterified cellulose ethers with high molecular weight and low viscosity in acetone, enhancing their efficiency in coating processes by maintaining a balance between molecular weight and viscosity, facilitating their use in spray-drying and coating applications.
Implementation Method 1
feeding a reaction diluent at different stages to the reaction mixture at the production of the esterified cellulose ether
Implementation Method 2
reacting a cellulose ether with an aliphatic monocarboxylic acid anhydride and a dicarboxylic acid anhydride
Data Source
AI summary
A modified process for producing an esterified cellulose ether is provided which comprises the stages of i) preparing a reaction mixture comprising a cellulose ether, an aliphatic monocarboxylic acid anhydride, a dicarboxylic acid anhydride, and a reaction diluent and heating the reaction mixture to a temperature of from 60°C to 110 °C prior to, during or after mixing the components of the reaction mixture to conduct an esterification reaction, and ii) before the esterification reaction is completed, adding an additional amount of reaction diluent continuously or in one or more portions to the reaction mixture and allowing the esterification reaction to further proceed.