Heat-Expandable Microspheres via Functional Shell Polymerization
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Solution Overview
Problem
Existing methods for producing heat-expandable microspheres result in agglomeration and poor dispersibility due to a plasticized thermoplastic resin shell, leading to increased ash content and viscosity issues in applications like paints, and fail to produce microspheres with a mean particle size of 10 μm or less efficiently.
Innovation Solution
A process involving polymerization in an aqueous dispersion medium with a specific ratio of fine-particle metal compounds, such as colloidal silica, to produce heat-expandable microspheres with a mean particle size ranging from 0.01 to 10 μm and minimal ash content, ensuring good dispersibility and thermal expansion performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If reactive surfactants are used to produce small heat-expandable microspheres, then particle size is reduced to 10 μm or less, but the microspheres agglomerate and exhibit poor dispersibility due to plasticization of the thermoplastic resin shell
Solution Approach 1:
The invention changes the chemical composition parameters of the shell by incorporating specific functional groups (carboxyl, hydroxyl, or amine groups) that can form crosslinks or hydrogen bonds, fundamentally altering the shell's resistance to plasticization and its ability to maintain structural integrity during thermal expansion
Solution Approach 2:
The invention creates a composite shell structure combining thermoplastic resin with polymers containing specific functional groups (carboxyl, hydroxyl, or amine groups), forming a multi-component system that resists plasticization by reactive surfactants while maintaining small particle size and good dispersibility
2Reliability
If colloidal silica is used as a dispersion stabilizer to control agglomeration, then dispersibility is improved, but ash content increases to more than 10 wt % which cannot be decreased by washing
Solution Approach 1:
The invention extracts and eliminates the need for colloidal silica as a dispersion stabilizer by incorporating dispersibility-enhancing functional groups directly into the shell polymer structure, thereby removing the source of high ash content while maintaining good dispersibility
Solution Approach 2:
The functional groups (carboxyl, hydroxyl, or amine groups) in the shell polymer act as intermediaries that provide both structural integrity and dispersibility, replacing the need for external dispersants like colloidal silica and thereby reducing ash content
3Length of moving object
If the thermoplastic resin shell is plasticized by reactive surfactants, then small particle size is achieved, but the shell becomes weaker and requires large amounts of colloidal silica to control agglomeration
Solution Approach 1:
The invention changes the mechanical properties of the shell by incorporating functional groups that form crosslinks or hydrogen bonds, fundamentally altering the shell's strength characteristics and its resistance to plasticization by surfactants
Solution Approach 2:
The invention creates a composite shell structure where the combination of thermoplastic resin and polymers with specific functional groups produces synergistic effects, enhancing shell strength while maintaining small particle size without requiring excessive colloidal silica
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 efficiently produces heat-expandable microspheres that thermally expand into lightweight, hollow particles with improved dispersibility and physical properties, reducing ash content and viscosity issues in applications like paints and lithium-ion battery electrodes.
Implementation Method 1
polymerizing the polymerizable component
Implementation Method 2
containing a fine-particle metal compound having a mean particle size ranging from 1.0 to 10 nm
Implementation Method 3
heat-expandable microspheres which encapsulate a volatile blowing agent
Data Source
AI summary
A process for producing heat-expandable microspheres including a thermoplastic resin shell and a blowing agent encapsulated therein. The process includes the steps of dispersing a polymerizable component and the blowing agent in an aqueous dispersion medium having a pH of 7 or less and containing a fine-particle metal compound having a mean particle size ranging from 1.0 to 10 nm, and polymerizing the polymerizable component. The amount of the fine-particle metal compound ranges from 0.15 to 20 parts by weight to 100 parts by weight of the total amount of the polymerizable component and the blowing agent. Also disclosed are heat-expandable microspheres produced by dispersing a polymerizable component and a blowing agent in an aqueous dispersion medium containing colloidal silica and polymerizing the polymerizable component. Also disclosed is a composition containing the heat-expandable microspheres and a base component, a formed product, a slurry composition for use in forming a negative electrode of a lithium-ion secondary battery and a negative electrode.