Optically Brightened Latexes via Copolymerization
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Solution Overview
Problem
The paper industry faces challenges with optical brighteners bleeding out of coated papers over time, leading to yellowing, and achieving high whiteness without using expensive carriers or untested toxicological substances during the emulsion polymerization process.
Innovation Solution
A method for preparing an aqueous composition by emulsion polymerization of ethylenically unsaturated monomers in the presence of water-soluble diaminostilbene disulphonic optical brighteners, ensuring over 90% of the brightener is entrapped within the polymer matrix, preventing bleed and achieving high whiteness without additional carriers or toxic substances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If water-soluble diaminostilbene disulphonic optical brighteners are used in coated papers, then whiteness and brightness are improved, but the optical brightener bleeds out of the coated paper over time through the action of solvents, leading to yellowing
Solution Approach 1:
The patent combines the optical brightener molecule with the polymer binder through copolymerization, merging two previously separate components (brightener and binder) into a single integrated polymer structure. This ensures the brightener remains permanently fixed within the binder matrix and cannot bleed out, while still providing the desired whiteness enhancement.
Solution Approach 2:
The patent uses ethylenically unsaturated substituents (acrylic, methacrylic, or allylic groups) as intermediaries to connect the diaminostilbene disulphonic core to the polymer chain. These intermediary groups enable covalent bonding between the brightener and polymer, creating a stable connection that prevents migration and bleeding.
2Illumination intensity
If large concentrations of carriers (polyethylene glycol or polyvinyl alcohol) are introduced to overcome saturation, then whiteness ceiling is improved, but device complexity and formulation complexity increase
Solution Approach 1:
The patent eliminates the need for separate carrier substances by integrating the optical brightener functionality directly into the polymer binder structure. This merging of functions removes the complexity of managing multiple components (binder + carrier + brightener) and simplifies the formulation to just the copolymerized brightener-binder system.
3Reliability
If acrylic-, methacrylic- or allylic-substituted diaminostilbene disulphonic optical brighteners are copolymerized, then bleedfastness is improved, but production cost increases due to expensive production and untested toxicological profile
Solution Approach 1:
The patent changes the chemical parameters of the optical brightener by introducing ethylenically unsaturated substituents (acrylic, methacrylic, or allylic groups) at specific positions on the diaminostilbene disulphonic core. This parameter change enables the brightener to participate in copolymerization reactions, providing permanent fixation and bleedfastness while maintaining compatibility with standard polymerization processes.
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 provides a stable, water-based latex binder that effectively prevents optical brightener bleed and achieves a high whiteness ceiling without the need for carriers, ensuring the brightener remains within the polymer matrix, enhancing the durability and appearance of coated papers.
Implementation Method 1
a method for the preparation of an aqueous composition, preferably of a water-based latex binder, by emulsion polymerization of at least one ethylenically unsaturated monomer in the presence of at least one water-soluble diaminostilbene disulphonic optical brightener
Implementation Method 2
emulsion polymerization of at least one ethylenically unsaturated monomer
Data Source
AI summary
The present invention relates to a method of preparing an aqueous composition by emulsion polymerization of at least one ethylenically unsaturated monomer in the presence of at least one water-soluble diaminostilbene disulphonic optical brightener, as well as to the aqueous composition obtainable by said method, the use of said aqueous composition for optically brightening of a cellulosic substrate and the cellulosic substrate treated with the aqueous composition.