Expanded Microspheres via Solid-Suspending-Agent-Free Spray Drying
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Solution Overview
Problem
Existing methods for producing expanded microspheres require the use of solid suspending agents, which increase ash content and density, making them unsuitable for applications where low ash and low density are crucial, such as in pharmaceuticals and certain industrial uses.
Innovation Solution
A spray-drying process that eliminates the need for solid suspending agents by controlling the inlet temperature of the drying gas within specific ranges relative to the polymer's glass transition temperature, allowing for the production of expanded microspheres with a polymeric shell free from particulate deposits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If solid suspending agents are used to prevent coalescence and aggregation of microspheres, then the microspheres maintain stability during preparation and expansion, but the ash content and particle density of the expanded microspheres increase
Solution Approach 1:
The invention extracts and eliminates the solid suspending agent from the system by using a liquid suspending agent instead. This removes the source of inorganic ash deposits on the microsphere surface while maintaining the necessary suspension stability during preparation and expansion processes
Solution Approach 2:
The invention changes the physical state parameter of the suspending agent from solid to liquid form. This parameter change eliminates the inorganic ash content associated with solid agents while maintaining suspension functionality, directly resolving the contradiction between stability and ash content
2Stability of the object's composition
If solid suspending agents are used to prevent aggregation of unexpanded microspheres, then the microspheres remain dispersed during handling, but the weight and particle density of the expanded microspheres increase
Solution Approach 1:
The invention extracts the solid suspending agent that causes weight increase and replaces it with a liquid suspending agent. This eliminates the inorganic residue on the microsphere surface, reducing the particle density of the expanded microspheres while maintaining dispersion stability
Solution Approach 2:
The invention changes the suspending agent from solid to liquid phase, which fundamentally alters the weight characteristics. The liquid agent does not leave inorganic deposits, thereby reducing the particle density of the final expanded product while maintaining the necessary dispersion stability
3Stability of the object's composition
If solid suspending agents are used to prevent coalescence during preparation, then the microspheres maintain individual structure, but the exterior surface of expanded microspheres becomes coated with inorganic particles
Solution Approach 1:
The invention extracts and removes the solid suspending agent that creates harmful inorganic deposits on the microsphere surface. By replacing it with a liquid suspending agent, the source of surface contamination is eliminated while the protective function against coalescence is maintained
Solution Approach 2:
The invention changes the physical state of the suspending agent from solid to liquid, which eliminates the inorganic particulate matter that causes surface coating. This parameter change removes the harmful effect of inorganic deposits while preserving the structural integrity function
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 produces low-ash, low-density microspheres with high brightness, suitable for use as fillers and drug delivery vehicles, particularly when combined with pharmaceutically acceptable polymers like poly(lactic acid) or carboxymethyl cellulose, offering improved performance in applications where ash content is detrimental.
Implementation Method 1
spray-drying the composition of step a) in a spray dryer, the spray dryer comprising an inlet drying gas having an inlet temperature (Tinlet, ° C.)
Implementation Method 2
a) obtaining a composition comprising a polymer dissolved in a solvent, wherein the polymer has a glass transition temperature (Tg, ° C.)
Data Source
AI summary
Expanded microspheres include a polymeric shell surrounding a hollow core, wherein the exterior surface of the polymeric shell is free from particulate deposits originating from a solid suspending agent.