Freeze-Drying Outgassing Phase for Uniform Crystal Structure
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Solution Overview
Problem
Existing freeze-drying methods often result in inconsistent drying due to varying ice crystal structures and moisture differences within and between containers, leading to unreliable product quality.
Innovation Solution
A method that minimizes gas escape during the freezing phase by reducing pressure to just above the solvent's partial pressure, allowing for uniform freezing and synchronous freezing across all containers, using existing freeze-drying systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If pressure is reduced during the freezing phase, then gas escape is minimized and uniform freezing is achieved, but the freezing process takes longer
Solution Approach 1:
The patent applies preliminary action by conducting an outgassing phase before the freezing phase. During this outgassing phase, pressure is reduced to allow gases to escape from the product while temperature remains constant. This preliminary removal of gases prevents interference with subsequent freezing, enabling uniform crystal structure formation without time loss during the freezing phase itself.
Solution Approach 2:
The patent segments the traditional combined freezing-drying process into distinct phases: outgassing phase (pressure reduction at constant temperature), freezing phase (temperature reduction at constant pressure), and drying phase (sublimation at reduced pressure). This segmentation allows each phase to be optimized independently, with the outgassing phase preparing the product for uniform freezing without extending the freezing time.
2Productivity
If temperature is raised during outgassing to accelerate gas removal, then outgassing efficiency increases, but product quality may be impaired
Solution Approach 1:
The patent applies parameter changes by carefully controlling temperature and pressure parameters during the outgassing phase. Pressure is reduced to just above the partial pressure of the solvent at the freezing point, creating optimal conditions for gas removal. Temperature is maintained constant or only slightly increased, ensuring accelerated outgassing while preserving product quality for temperature-sensitive pharmaceuticals.
3Loss of substance
If pressure is reduced to outgassing pressure during the outgassing phase, then gas removal is enhanced, but the pressure gradient increases process complexity
Solution Approach 1:
The patent applies parameter changes by setting the outgassing pressure to a specific value: just above the partial pressure of the solvent corresponding to the freezing point. This precise pressure setting optimizes gas removal efficiency while maintaining simplicity in pressure control. The pressure is held constant during outgassing, then adjusted during subsequent phases, avoiding complex continuous pressure modulation.
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
This approach ensures uniform crystal structures and consistent product quality throughout the batch, accelerating the freeze-drying process while maintaining product integrity, especially for temperature-sensitive medicines.
Implementation Method 1
the product is first cooled to the product-specific freezing temperature and held at this temperature (freezing phase) until it is completely frozen
Implementation Method 2
the drying chamber is evacuated to dry the product (drying phase)
Implementation Method 3
the freeze-drying system's ice condenser is cooled
Implementation Method 4
freeze-drying system... to dry the product
Data Source
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AI summary
The invention relates to a method for freeze-drying a moist product containing a solvent, particularly when the product is contained in a number of vials, injection bottles, or product trays, wherein the moist product is introduced in a loading phase (A) in a liquid state, advantageously at ambient temperature (1) and/or ambient pressure (2), into a drying chamber of a freeze-drying system, wherein the product is frozen out in a freezing phase (D) at freezing temperature (6) and freezing pressure (7), and wherein the product is subsequently dried to the desired degree in a drying phase (E). A freeze-drying method in which the escape of gases during the freezing phase is prevented, or at least reduced to a minimum, is achieved by preceding the freezing phase (D) with a degassing phase (B) in which gases are removed from the moist product.