Spray-Dried Expanded Microspheres for Low-Ash, Low-Density Output
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Solution Overview
Problem
Existing methods for producing expanded microspheres require the use of solid suspending agents, which coat the exterior surface and increase ash content and density, making them unsuitable for applications where low ash and low density are essential.
Innovation Solution
A spray-drying process at specific temperature ranges, without the need for solid suspending agents, allows for the production of expanded microspheres with a polymeric shell surrounding a hollow core, using polymers like polyvinyl alcohol and carboxymethyl cellulose, and optionally with a blowing agent, to achieve low ash and low density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If solid suspending agents are used to prevent coalescence and aggregation of microspheres, then the microspheres maintain stable dispersion during preparation and expansion, but the ash content and particle density of the expanded microspheres increase significantly
Solution Approach 1:
The invention extracts and eliminates the solid suspending agent component from the microsphere preparation system. By using a polymer-solvent composition without any solid suspending agents, the process removes the source of ash content while maintaining dispersion stability through the polymer matrix itself, which prevents coalescence during spray-drying and expansion.
Solution Approach 2:
The invention changes the compositional parameters of the microsphere system by replacing solid suspending agents with a polymer-solvent system. The polymer concentration (1-50 wt%) and solvent type are optimized to provide sufficient viscosity and steric stabilization, preventing aggregation without introducing inorganic ash-forming materials.
2Stability of the object's composition
If solid suspending agents are used to prevent coalescence and aggregation of microspheres, then the microspheres maintain stable dispersion during preparation and expansion, but the particle density of the expanded microspheres increases
Solution Approach 1:
The invention extracts and eliminates the solid suspending agent component from the microsphere preparation system. By using a polymer-solvent composition without any solid suspending agents, the process removes the source of ash content while maintaining dispersion stability through the polymer matrix itself, which prevents coalescence during spray-drying and expansion.
Solution Approach 2:
The invention changes the compositional parameters of the microsphere system by replacing solid suspending agents with a polymer-solvent system. The polymer concentration (1-50 wt%) and solvent type are optimized to provide sufficient viscosity and steric stabilization, preventing aggregation without introducing inorganic ash-forming materials.
3Ease of manufacture
If conventional spray-drying temperatures are used, then the polymer solution can be processed, but the expansion ratio and microsphere quality are insufficient
Solution Approach 1:
The invention applies parameter changes by optimizing the spray-drying inlet temperature to a specific range (80-200°C) based on the polymer's glass transition temperature. This temperature optimization enables simultaneous achievement of complete solvent evaporation, polymer shell formation, and internal void creation through controlled expansion, producing high-quality microspheres with expansion ratios of 5-50x.
Solution Approach 2:
The invention utilizes phase transitions of the polymer and solvent during spray-drying. The rapid heating causes the solvent to evaporate and the polymer to transition from a liquid solution to a solid shell, while trapped vapor or blowing agent expands to create the hollow interior. This controlled phase transition is key to achieving both processability and high expansion ratio.
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 expanded microspheres with a clean exterior surface, low ash content, and controlled density, suitable for applications in ceramics, pharmaceuticals, and other fields, while maintaining a high ISO brightness value.
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
wherein the polymer has a glass transition temperature (Tg, °C)
Data Source
Figure 1A~1B
Figure 2
Figure 3
AI summary
The present disclosure relates to expanded microspheres comprising 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, and processes for preparing said expanded microspheres.