Aqueous PU Dispersion with Sulfonate Reactive Emulsifier
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Solution Overview
Problem
Current methods for achieving low-gloss and transparent coatings using waterborne polyurethane (PU) dispersions face challenges with matting agents, such as incompatibility and instability, leading to flaking and poor redispersibility, while organic polymer particles offer limited scratch resistance but poor matting effects.
Innovation Solution
A method for preparing an aqueous PU dispersion using non-ionic reactive emulsifiers and sulfonate groups, comprising specific weight ratios of polymer polyol, isocyanate monomer, trimethylolpropane, monofunctional alkoxy PEG or PPG, diaminosulphonate chain extender, non-ionic organic amine chain extender, catalyst, organic solvent, deionized water, and thickener, which results in a stable and redispersible emulsion with a low-gloss coating film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If inorganic silica matting agents are added to achieve low gloss, then the gloss is reduced, but the matting agents flake off easily and the surface finish increases over time
Solution Approach 1:
The patent uses reactive emulsifiers containing sulfonate groups as intermediaries that chemically bond to the polymer chains during emulsion polymerization. This creates a stable interface between the matting effect and the polymer matrix, preventing flaking while maintaining low gloss. The sulfonate groups act as a bonding mediator that anchors the matting structure within the coating.
Solution Approach 2:
The patent creates a composite structure by incorporating sulfonate-containing reactive emulsifiers into the polymer chains during synthesis. This forms a hybrid system where the sulfonate groups provide both matting functionality and chemical bonding capability, combining the benefits of low gloss with improved storage stability and resistance to flaking.
2Illumination intensity
If organic polymer particles are added to obtain low-gloss finish, then the matting effect is achieved, but the transparency of the coating film deteriorates
Solution Approach 1:
The patent changes the chemical parameters of the emulsifier by introducing sulfonate groups, which alter the refractive index and optical properties of the coating system. This chemical modification allows the matting effect to be achieved through molecular-level changes rather than adding opaque particles, thereby maintaining coating transparency while reducing gloss.
Solution Approach 2:
The patent applies matting functionality at the molecular level within the polymer chains through sulfonate groups, rather than adding bulk organic polymer particles. This localized approach to matting preserves the overall transparency of the coating film while achieving the desired low-gloss effect at specific sites within the coating structure.
3Illumination intensity
If polymer particles with large particle size and wide particle size distribution are used to obtain low-gloss coating surface, then the matting effect is achieved, but the emulsion shows agglomeration and poor redispersibility
Solution Approach 1:
The patent changes the charge parameter of the emulsion system by using sulfonate-containing reactive emulsifiers, which provide consistent negative charge density on the polymer chains. This electrostatic stabilization prevents agglomeration of particles during storage and maintains redispersibility, while the controlled polymerization process ensures uniform particle size distribution for consistent matting effect.
4Manufacturing precision
If diaminosulphonate is used as chain extender to introduce sulfonate groups, then sulfonate groups are incorporated into the polymer structure, but the anionic PU agglomerates easily during chain extension reaction
Solution Approach 1:
The patent uses non-ionic organic amine chain extenders as intermediaries during the chain extension reaction. These non-ionic extenders temporarily stabilize the emulsion during the reaction process, preventing premature agglomeration of the anionic PU. After the reaction, the sulfonate groups are successfully incorporated into the polymer structure, and the emulsion stability is restored through the sulfonate-containing emulsifier system.
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 method produces a coating film with a 60° gloss of <1.0, excellent redispersibility, and storage stability, overcoming the limitations of previous technologies by providing a stable and effective matting effect.
Implementation Method 1
One of the effective ways to solve the above problem is to introduce sulfonate groups into a macromolecular structure of a polymer
Implementation Method 2
an aqueous PU dispersion with non-ionic reactive emulsifiers and sulfonate groups
Data Source
AI summary
The present invention relates to a method for preparing an aqueous polyurethane (PU) dispersion with non-ionic reactive emulsifiers and sulfonate groups. The aqueous PU dispersion includes the following components: 10-40 parts by weight of polymer polyol, 5-20 parts by weight of isocyanate monomer, 0.1-1.5 parts by weight of trimethylolpropane, 3-15 parts by weight of monofunctional alkoxy polyethylene glycol or propylene glycol, 0.5-2.0 parts by weight of diaminosulphonate chain extender, 0.5-3.0 parts by weight of non-ionic organic amine chain extender, 0.01-0.05 parts by weight of catalyst, 0-8 parts by weight of organic solvent, 50-80 parts by weight of deionized water, and 0.1-5 parts by weight of thickener. In the presence of non-ionic reactive emulsifiers, introduction of sulfonate groups at late chain extension stage of the aqueous PU dispersion obtain stable large-size polymer particles. A coating film thereof has a 60° gloss of <1.0; the emulsion has excellent storage stability and redispersibility.