HPMCAS Powder Particle Size Control for Coating Clogging
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Solution Overview
Problem
Conventional hypromellose acetate succinate (HPMCAS) powders exhibit low solubility and are prone to clogging issues during coating and spray-drying processes, leading to incomplete dissolution and uneven film formation, which affects the acid resistance and workability of enteric coatings.
Innovation Solution
HPMCAS powder with an adjusted average ratio of maximum to minimum particle diameters (L/D) between 2.0 and 3.0, produced through a method involving dissolution, esterification, and precipitation, demonstrates improved solubility and reduced undissolved residue when dissolved in solvents like acetone or aqueous ammonia solutions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional HPMCAS powder is used for coating or spray-drying, then the process can proceed, but filter clogging and nozzle clogging occur due to undissolved materials
Solution Approach 1:
The patent applies parameter changes by controlling the particle size distribution of HPMCAS powder, specifically setting the D90 value (90th percentile of particle size) to 45 μm or less. This parameter optimization ensures complete dissolution in coating solutions, preventing filter and nozzle clogging while maintaining reliable coating and spray-drying processes
2Object-affected harmful factors
If aqueous enteric coating method is used, then environmental safety is improved, but the enteric polymer aggregates and clogs spray nozzle
Solution Approach 1:
The patent resolves this contradiction by optimizing the particle size parameter of HPMCAS powder (D90 ≤ 45 μm). This fine particle size control enables the aqueous coating method to work effectively by preventing polymer aggregation, thus eliminating nozzle clogging while preserving the environmental benefits of using aqueous solutions instead of organic solvents
3Ease of manufacture
If ammonia-neutralized coating method is used, then HPMCAS dissolves, but undissolved materials remain and acid resistance is insufficient
Solution Approach 1:
The patent applies parameter changes by precisely controlling the particle size distribution (D90 ≤ 45 μm) of HPMCAS powder. This optimization ensures complete dissolution in ammonia-neutralized coating solutions, eliminating undissolved materials and achieving sufficient acid resistance for reliable enteric coating performance
4Productivity
If HPMCAS powder with low solubility is used, then production can proceed, but undissolved materials remain and film uniformity is poor
Solution Approach 1:
The patent resolves this contradiction by optimizing the particle size parameter of HPMCAS powder, setting D90 to 45 μm or less. This fine particle size control dramatically improves solubility and dissolution rate, ensuring complete dissolution during production while achieving uniform film formation, thus maintaining productivity without sacrificing manufacturing precision
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 optimized HPMCAS powder enhances solubility, reduces clogging, and facilitates faster preparation of coating solutions, ensuring uniformity and acid resistance in enteric coatings.
Implementation Method 1
dissolving a mixture of a drug and the polymer in a solvent
Implementation Method 2
mixing the reaction mixture with water to precipitate HPMCAS
Data Source
AI summary
Provided are HPMCAS powder having high solubility when dissolved in a solvent and being capable of suppressing generation of undissolved materials; and a method for producing the powder. More specifically, provided is hypromellose acetate succinate powder having an average ratio of L to D of from 2.0 to 3.0, wherein L and D mean maximum and minimum diameters of each particle, respectively. Also provided is a method for producing a hypromellose acetate succinate, comprising the steps of: dissolving hypromellose powder in a solvent, esterifying the dissolved hypromellose with succinic anhydride and acetic anhydride in the presence of a catalyst to obtain a reaction mixture, and mixing the reaction mixture with water to precipitate hypromellose acetate succinate, wherein the reaction mixture just before being mixed with the water has a viscosity of from 100 to 200 Pa·s.