Thermally Expanding Microcapsule Shell Cross-Linking
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Solution Overview
Problem
Thermally expandable microcapsules used in foam molding face challenges with low expansion ratios and durability at high temperatures, along with potential discoloration and odor issues.
Innovation Solution
A thermally expandable microcapsule with a polymer shell formed from a monomer composition containing a nitrile monomer and a compound with a glycidyl group, exhibiting specific gel fractions and cross-linkage properties to enhance gas barrier and thermal expansion properties, ensuring high durability and expansion ratios without discoloration or odor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thermally expandable microcapsule is heated at high temperatures or for a long time, then the microcapsule structure becomes more stable, but gas escapes from the expanded microcapsule leading to reduction in expansion ratio
Solution Approach 1:
The patent changes the chemical composition parameters of the shell polymer by incorporating specific monomers (carboxy group-containing monomer and monomer with reactive group) that form cross-linked structures. This modifies the thermal and mechanical properties of the shell to simultaneously achieve high-temperature stability and gas retention capability.
Solution Approach 2:
The patent creates a composite shell structure through cross-linking of polymer chains with specific functional groups. The cross-linked network combines the thermal stability of the polymer matrix with the gas barrier properties of the cross-linked structure, preventing gas escape while maintaining structural integrity at high temperatures.
2Reliability
If strong three-dimensional cross-links are formed during polymerization, then heat resistance is significantly improved, but expansion in foaming is inhibited resulting in insufficient expansion ratio
Solution Approach 1:
The patent introduces local cross-linking through specific reactive groups (carboxy groups reacting with monomers having reactive groups) rather than uniform dense cross-linking. This creates localized cross-linked structures that provide heat resistance while leaving sufficient regions for thermal expansion and foaming, thus achieving both heat resistance and adequate expansion ratio.
3Weight of stationary object
If the shell is expanded to be very thin, then weight reduction is achieved, but the microcapsule becomes susceptible to deflation and breakage at high temperatures
Solution Approach 1:
The patent creates a composite shell structure through cross-linking of polymer chains with specific functional groups. The cross-linked network combines the thermal stability of the polymer matrix with the gas barrier properties of the cross-linked structure, preventing gas escape while maintaining structural integrity at high temperatures.
Solution Approach 2:
The patent changes the chemical composition parameters of the shell polymer by incorporating specific monomers (carboxy group-containing monomer and monomer with reactive group) that form cross-linked structures. This modifies the thermal and mechanical properties of the shell to simultaneously achieve high-temperature stability and gas retention capability.
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 microcapsule achieves high expansion ratios and durability at high temperatures, preventing discoloration and odor, and maintaining shape retention, thus improving foam molding performance.
Implementation Method 1
the shell obtained by polymerizing a monomer composition that contains a nitrile monomer and a compound having a glycidyl group in a molecule, the shell exhibiting a value y of 50% or higher and a ratio y/x of 1.1 or higher, in which x represents a gel fraction at ordinary temperature, and y represents a gel fraction upon heating at 180° C. for 30 minutes
Implementation Method 2
a volatile expansion agent as a core agent encapsulated by the shell
Data Source
AI summary
The present invention provides a thermally expandable microcapsule that has a high expansion ratio and durability at high temperatures, and is not likely to cause discoloration and odor when used for foam molding. The thermally expandable microcapsule of the present invention includes: a shell formed from a polymer; and a volatile expansion agent as a core agent encapsulated by the shell, the shell obtained by polymerizing a monomer composition that contains a nitrile monomer and a compound having a glycidyl group in a molecule, the shell exhibiting a value y of 50% or higher and a ratio y/x of 1.1 or higher, in which x represents a gel fraction at ordinary temperature, and y represents a gel fraction upon heating at 180° C. for 30 minutes.