microspheres
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Solution Overview
Problem
Commercially available thermally expandable microspheres with low Tstart suffer from high residual monomers, discolouration, and poor chemical resistance, making them unsuitable for applications requiring high expansion capability and chemical resistance without halogen-containing monomers.
Innovation Solution
Thermally expandable thermoplastic microspheres are produced using a monomer composition comprising 40-70 wt% acrylonitrile, 5-40 wt% methacrylonitrile, and 10-50 wt% esters of acrylic or methacrylic acid, with a propellant of methane, ethane, propane, isobutane, or neo-pentane, minimizing halogen-containing monomers and optimizing the polymer shell's glass transition temperature for low Tstart and high expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If halogen-containing monomers like vinylidene chloride are used to achieve low Tstart and high expansion capability, then the expansion performance is improved, but residual monomers increase, discolouration occurs, and chemical resistance deteriorates
Solution Approach 1:
The patent changes the chemical composition parameters of the polymer shell by replacing halogen-containing monomers with a specific combination of acrylonitrile (40-70 wt%), methacrylonitrile (5-40 wt%), and acrylic/methacrylic acid esters (10-50 wt%). This parameter change maintains the desired low Tstart and high expansion capability while eliminating the harmful effects of halogen monomers, thereby improving chemical resistance and reducing residual monomers
Solution Approach 2:
The patent creates a composite polymer shell structure using multiple monomers with different properties. The combination of acrylonitrile (providing chemical resistance), methacrylonitrile (adjusting Tg), and acrylic/methacrylic acid esters (controlling expansion characteristics) forms a composite material that achieves both low Tstart and high chemical resistance simultaneously, resolving the contradiction between expansion performance and reliability
2Temperature
If halogen-containing monomers are used to achieve low Tstart, then expansion capability is improved, but discolouration occurs
Solution Approach 1:
The patent changes the monomer composition to exclude halogen-containing monomers entirely, using instead acrylonitrile, methacrylonitrile, and acrylic/methacrylic acid esters. This parameter change eliminates the discolouration problem while maintaining low Tstart through the synergistic effect of the alternative monomer combination, particularly the glass transition temperature adjustment provided by methacrylonitrile and the esters
3Productivity
If halogen-containing monomers are used to achieve high expansion capability, then Tstart is reduced, but residual monomers increase
Solution Approach 1:
The patent employs a composite monomer system where acrylonitrile (40-70 wt%) provides the base polymer structure, methacrylonitrile (5-40 wt%) adjusts the glass transition temperature for low Tstart, and acrylic/methacrylic acid esters (10-50 wt%) control the expansion characteristics. This composite approach achieves high expansion capability while the stable polymer structure minimizes residual monomers, resolving the contradiction between productivity and substance loss
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 microspheres achieve high expansion capability with low Tstart and improved chemical resistance, suitable for paper making and printing inks, while reducing residual monomers and maintaining brightness.
Implementation Method 1
Upon heating, the propellant evaporates to increase the internal pressure at the same time as the shell softens, resulting in significant expansion of the microspheres
Implementation Method 2
the temperature at which the expansion starts is called T start , while the temperature at which maximum expansion is reached is called T max
Data Source
AI summary
The invention relates to thermally expandable thermoplastic microspheres comprising a polymer shell made from ethylenically unsaturated monomers encapsulating a propellant, said ethylenically unsaturated monomers comprising from 40 to 70 wt% of acrylonitrile, from 5 to 40 wt% of methacrylonitrile, from 10 to 50 wt% of monomers selected from the group consisting of esters of acrylic acid, esters of methacrylic acid and mixtures thereof, and said propellant comprising at least one of methane, ethane, propane, isobutane, n-butane and neo-pentane. The invention further relates to the production and use of the microspheres.