Expanded Microspheres Without Suspending Agent Deposits
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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 desired.
Innovation Solution
A spray-drying process at elevated temperatures, without the need for solid suspending agents, where the minimum inlet temperature of the drying gas is set to T inlet ≥ T g *0.75 for polymers without a blowing agent, and T inlet ≥ T g *0.60 with a blowing agent, ensuring the boiling point of the blowing agent is ≤ T inlet + 20°C.
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 unexpanded microspheres, then the stability and dispersibility of microspheres are improved, but the ash content and density of expanded microspheres increase
Solution Approach 1:
The patent removes solid suspending agents from the microsphere preparation process entirely. Instead of using inorganic suspending agents like colloidal silica or alumina sol, the invention employs a surfactant-based system that allows microspheres to be prepared and processed without any solid additives, thereby eliminating the source of ash content in the final product.
Solution Approach 2:
The patent changes the chemical parameters of the suspension system by replacing inorganic solid suspending agents with organic surfactants. This parameter change allows the microspheres to maintain stability during preparation without introducing inorganic residues, achieving low-ash-content expanded microspheres suitable for applications like porous ceramic production and pharmaceutical drug delivery.
2Stability of the object's composition
If solid suspending agents are used to prevent aggregation of unexpanded microspheres, then the dispersibility is improved, but the particle density increases
Solution Approach 1:
The patent extracts and eliminates solid suspending agents from the process, replacing them with a surfactant system that provides adequate dispersion without adding significant mass to the microspheres. This results in expanded microspheres with lower particle density, making them more effective as lightweight fillers and reducing the weight burden in applications like coatings and mortars.
3Use of energy by stationary object
If conventional spray-drying is used at lower temperatures, then energy consumption is reduced, but the polymer shell does not form properly and microspheres do not expand
Solution Approach 1:
The patent identifies and optimizes the critical temperature parameter for spray-drying, establishing that the inlet temperature must be at least 0.75 times the glass transition temperature of the polymer (Tg). This parameter change ensures proper polymer shell formation and microsphere expansion while maintaining energy efficiency. The invention provides a clear temperature guideline that balances energy consumption with reliable microsphere formation.
Solution Approach 2:
The patent incorporates a blowing agent into the polymer solution before spray-drying, which prepares the system in advance for expansion. The blowing agent is dissolved or dispersed in the polymer solution, and upon contact with the hot drying gas during spray-drying, it generates gas bubbles that expand the microspheres as the polymer shell forms, ensuring both proper shell formation and expansion in a single step.
4Volume of moving object
If a blowing agent is used to enhance expansion, then the expansion ratio is improved, but the process complexity increases due to additional temperature constraints
Solution Approach 1:
The patent establishes a straightforward temperature constraint for using blowing agents: the inlet temperature should be at least 0.60 times the glass transition temperature of the polymer (Tg), and the blowing agent's boiling point should be within 20°C of the inlet temperature. These clear parameter guidelines simplify the process design and operation, making it easier to select appropriate blowing agents and set processing conditions without excessive complexity.
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 polymeric shell free from solid suspending agent deposits, achieving low ash and low density, suitable for applications such as low-density fillers and drug delivery vehicles.
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 (T inlet, °C)
Implementation Method 2
wherein the composition further comprises a blowing agent, b) spray-drying the composition of step a) in a spray dryer... wherein the blowing agent boiling point temperature (T BABP, °C) is ≤ T inlet + 20°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.