Core-Shell Copolymers Redispersibility in Organic Media
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Solution Overview
Problem
Existing methods for producing core-shell polymers with elastomeric properties result in powders that are not redispersible in organic media, leading to inhomogeneous distributions and reduced impact strength when used as impact modifiers, due to particle agglomerates formed during spray drying or precipitation processes.
Innovation Solution
Development of elastomeric particulate core-shell copolymers with a core organopolysiloxane polymer, a polydialkylsiloxane shell, and an organopolymer shell, produced through an emulsion polymerization process that allows for redispersion in organic media without complex mechanical emulsification, achieving a monomodal particle size distribution and improved phase binding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If precipitation reactions are used to produce graft copolymers, then the powders can be isolated and produced, but the powders have increased salt load and are not redispersible in organic media
Solution Approach 1:
The invention changes the chemical composition parameters of the shell by incorporating specific organopolymer components (polyester, poly carbonate, polyurethane) with defined functional groups that provide both processability and redispersibility in organic media, resolving the contradiction between ease of manufacture and adaptability
Solution Approach 2:
The invention creates a composite core-shell structure where the organosilicon polymer core is combined with an organopolymer shell containing specific functional groups, achieving both easy isolation and redispersibility in organic media through the synergistic combination of materials
2Length of moving object
If homogenization is used to produce graft copolymers, then the particle size can be reduced, but a polydisperse particle size distribution is obtained
Solution Approach 1:
The invention performs preliminary stabilization of particle size during the emulsion polymerization process by controlling the nucleation and growth stages, preventing polydispersity before homogenization is applied, thus achieving both small particle size and narrow size distribution
Solution Approach 2:
The invention maintains continuous control over particle size during the entire polymerization process through controlled monomer addition and emulsifier presence, ensuring monomodal distribution while achieving the desired small particle size
3Ease of manufacture
If spray drying or precipitation is used to produce powders from aqueous dispersion, then the powders can be obtained, but particle agglomerates are formed that cannot be completely redispersed
Solution Approach 1:
The invention changes the surface chemical parameters of the particles by incorporating organopolymer components with functional groups that provide steric stabilization and prevent agglomeration during spray drying, enabling complete redispersion while maintaining ease of powder production
Solution Approach 2:
The organopolymer shell acts as an intermediary between the organosilicon core and the organic medium, providing a compatible interface that prevents agglomeration during processing and enables redispersion, resolving the contradiction between ease of manufacture and ease of operation
4Length of moving object
If complex mechanical emulsification is used to produce core-shell polymers, then particle size can be controlled, but the process becomes complex and redispersion requires additional emulsification
Solution Approach 1:
The invention replaces complex mechanical emulsification with chemical emulsion polymerization, where surfactants and controlled polymerization kinetics naturally stabilize particles at the desired size without requiring complex mechanical equipment or subsequent emulsification steps
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 resulting copolymers are easily redispersible in organic media, improving impact resistance, processing behavior, and mechanical properties such as weather stability and notched impact strength, with a high redispersibility of over 80% and optimal particle size control.
Implementation Method 1
The resulting copolymers are easily redispersible in organic media, improving impact resistance, processing behavior, and mechanical properties
Implementation Method 2
produced through an emulsion polymerization process that allows for redispersion in organic media without complex mechanical emulsification, achieving a monomodal particle size distribution
Data Source
AI summary
The invention provides elastomeric, particulate core-shell copolymers which are composed of a) 10% to 95% by weight, based on the total weight of the copolymer, of a core organopolysiloxane polymer A, b) 0.5% to 30% by weight, based on the total weight of the copolymers, of a polydialkylsiloxane shell B comprising units of the formula (R3SiO1/2)w(R2SiO2/2)x.(R1SiO3/2)y..(SiO4/2)z, in which w = 0 to 20 mol%, x = 0 to 99.5 mol%, y = 0.5 to 100 mol%, and z = 0 to 50 mol%, c) 0 to 89.45% by weight, based on the total weight of the copolymers, of a shell C of organic polymer of monoolefinically or polyolefinically unsaturated monomers, and d) 0.05% to 89.5% by weight, based on the total weight of the copolymers, of a shell D of organopolymer of monoolefinically unsaturated monomers, where R radicals have the definitions stated in claim 1, and the particles have an average size of 10 to 300 nm and a monomodal size distribution, with the proviso that at least 5% of the radicals R in the polydialkylsiloxane shell B have definitions selected from alkenyl radicals, acyloxyalkyl radicals, and mercaptoalkyl radicals, and a process for preparing them.