Core/Shell Polymer Dispersion for Low-Temperature Film Formation
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Solution Overview
Problem
Current aqueous polymer dispersions for coatings face challenges in achieving a stable film formation at low temperatures while maintaining resistance to blocking and flexibility, with issues of gelling or flocculation under emulsion polymerization conditions and during storage, and high VOC emissions.
Innovation Solution
An aqueous polymer dispersion with core/shell structured particles obtained by emulsion polymerization using specific monomer compositions and a surfactant system comprising phosphated anionic surfactants, which controls the glass transition temperatures and stability, reducing VOC emissions and improving coating performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If emulsion polymerization is used to create stable dispersion, then stability is improved, but gelling or flocculation occurs under polymerization conditions and during storage
Solution Approach 1:
The patent applies parameter changes by carefully controlling the glass transition temperatures (Tg) of the core and shell polymers, adjusting monomer compositions, and optimizing surfactant levels to achieve stable dispersion that prevents gelling and flocculation while maintaining low TMF
Solution Approach 2:
The patent uses composite materials by creating core/shell structured particles with different polymer compositions - a soft core phase and a harder shell phase - which work together to provide both stability and prevent unwanted gelation or flocculation
2Temperature
If low TMF is achieved for good film formation, then flexibility is improved, but resistance to blocking deteriorates
Solution Approach 1:
The patent applies local quality by creating distinct core and shell regions with different Tg values - the core provides low temperature film formation and flexibility, while the shell provides blocking resistance, allowing each region to perform its specific function optimally
Solution Approach 2:
The patent uses segmentation by dividing the particle structure into separate core and shell phases with different functional properties, enabling independent optimization of film formation temperature and blocking resistance without compromise
3Ease of manufacture
If conventional surfactants are used, then ease of manufacture is improved, but coagulum rate and sticking rate increase
Solution Approach 1:
The patent applies parameter changes by selecting specific phosphate-based surfactants with particular HLB values and molecular structures, and optimizing their concentration levels to reduce coagulum and sticking rates while maintaining ease of manufacture
4Object-affected harmful factors
If aqueous system is used to reduce VOC emissions, then environmental performance is improved, but film formation and blocking resistance deteriorate
Solution Approach 1:
The patent uses composite materials by formulating aqueous dispersions with core/shell structured particles that combine low-Tg and high-Tg polymers, enabling effective film formation and blocking resistance in VOC-free aqueous systems
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 dispersion achieves a minimum film formation temperature below 0°C, excellent resistance to blocking and cracking, good gloss, and stability, with low coagulum and sticking rates, ensuring industrial feasibility and low VOC emissions.
Implementation Method 1
the use of a surfactant system comprising at least one phosphated anionic surfactant at particular levels in each of the polymer phases constituting said structured particle
Implementation Method 2
obtained by emulsion polymerization of at least two monomer compositions, in at least two stages
Data Source
AI summary
The invention relates to an aqueous dispersion of a polymer, including polymer particles having a core/skin structure, that can be obtained by the emulsion polymerisation of at least two monomer compositions 1 and 2 in at least two steps, said at least two monomer compositions 1 and 2 yielding polymers P1 and P2 having respective glass-transition temperatures Tg1 and Tg2, with Tg1 being lower than or equal to 30°C and Tg2 being higher than or equal to 80°C, the difference Tg2-Tg1 ranging from 50 to 200°C, wherein said polymerisation is carried out in the presence of at least one anionic phosphated surfactant that is present: a) either in the P1 polymer phase only; or b) in the P1 and P2 polymer phases provided that the weight ratio (anionic phosphated surfactant in P1/ anionic phosphated surfactant in P2) is higher than 1, the weight ratio of said anionic phosphated surfactant ranging from 0.5 t 5 wt %, preferably from 0.5 to 3 wt % and more preferably from 1 to 3 wt % relative to the total weight of the monomers in the dispersion, said phase P1 representing a ratio from 70 to 90 wt % of the total of P1+P2, and P2 representing a ratio from 10 to 30 wt % of the total of P1+P2. The invention also relates to a method for preparing said dispersion, to a composition of polymer aqueous dispersions including said dispersion, to a method for preparing said composition, to a coating or treatment composition containing said dispersion, to the use thereof in coatings or for treating natural or synthetic fibres, to the coating thus obtained and to a substrate coated with such a coating.