Superabsorbent Copolymer with Covalently Bonded Optical Brightener
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Solution Overview
Problem
Existing superabsorbent polymers used in sanitary articles face challenges in maintaining a white color, as they tend to develop a yellowish hue, which is aesthetically undesirable and affects consumer preference, despite the use of optical brighteners that are physically mixed with or coated onto the polymers, as these methods are inadequate in ensuring long-term color stability and bonding with the polymer.
Innovation Solution
A superabsorbent copolymer is developed by incorporating a reactive optical brightener comonomer that reacts with the first monomer during polymerization, forming covalent bonds within the polymer network, thereby enhancing the optical brightener's bonding and reducing leaching, and using pyrene derivatives as reactive optical brightener comonomers to improve color stability and whiteness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If optical brighteners are physically mixed with or coated onto superabsorbent polymer, then the polymer appears whiter, but the optical brighteners leach out over time causing color instability
Solution Approach 1:
The patent combines the optical brightener comonomer with the polymer network through covalent bonding during polymerization, merging the two previously separate components (optical brightener and polymer) into a single integrated structure where the optical brightener becomes an inherent part of the polymer chain
Solution Approach 2:
The reactive optical brightener comonomer acts as an intermediary that bridges the gap between the desired optical effect and the polymer structure, containing both the optical brightening functionality and the polymerizable group that enables covalent attachment to the polymer network
2Volume of moving object
If more particulate superabsorbent polymer is used to maintain retention capacity in thinner sanitary articles, then the articles become smaller and thinner, but the yellowing becomes more noticeable affecting aesthetics
Solution Approach 1:
The patent changes the chemical parameter of the optical brightener attachment method from physical mixing/coating to covalent bonding, which fundamentally alters the stability and effectiveness of the optical brightening function, allowing for better color appearance even at higher polymer concentrations required in thinner articles
3Ease of manufacture
If conventional optical brighteners are used that are not chemically bonded, then the manufacturing process is simpler, but the bonding and retention of optical brighteners is inadequate
Solution Approach 1:
The patent applies local quality by incorporating the optical brightening function specifically at the molecular level within the polymer structure, where the reactive comonomer units are distributed throughout the polymer network, providing localized optical brightening exactly where needed rather than as a surface coating
Solution Approach 2:
The patent creates a composite material system where the optical brightener comonomer and polymer monomers are combined into a single copolymer material, integrating multiple functions (polymer structure and optical brightening) into one unified material rather than combining separate materials
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 approach results in a superabsorbent copolymer that maintains a whiter appearance, reducing yellowness and enhancing consumer perception by ensuring better bonding and retention of optical brighteners, thus addressing the aesthetic concerns in sanitary products.
Implementation Method 1
a reactive optical brightener comonomer that reacts with the first monomer during polymerization, forming covalent bonds within the polymer network
Implementation Method 2
optical brighteners can thus compensate for the esthetically undesirable yellowish cast found in otherwise white (or colorless) polymers such as superabsorbent polymers
Data Source
AI summary
The invention relates to a superabsorbent copolymer comprising a reaction product of a reactive optical brightener comonomer. In another embodiment, the superabsorbent copolymer comprises a reaction product of a first monomer and a reactive optical brightener comonomer. The reactive optical brightener comonomer may be selected from various pyrene optical brighteners listed herein. The invention also relates to superabsorbent copolymer having from about 0.1 to 10,000 ppm of a reactive optical brightener comonomer based on the superabsorbent copolymer.