Water Absorbent Gel Stability via Crosslinking
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Solution Overview
Problem
Conventional water-absorbing resins used in sanitary materials like paper diapers and sanitary napkins face issues with durability, anti-urine tolerance, and temporal stability, leading to gel instability and poor liquid permeability, which affects their performance in absorbing and distributing liquids effectively.
Innovation Solution
A water absorbent with a specific particle size distribution, surface cross-linking, and a particular chemical cross-linking index is developed by polymerizing a monomer containing acrylic acid in the presence of an internal cross-linking agent and a water-soluble chain transfer agent, followed by surface treatment, to enhance gel properties and liquid permeability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If water-absorbing resin is used to achieve high water absorbency, then liquid absorption capacity is improved, but gel stability and temporal durability deteriorate
Solution Approach 1:
The patent applies parameter changes by controlling the neutralization degree of polyacrylic acid within 30-80% and adjusting the crosslinking agent concentration to 0.01-5% by weight. These specific parameter ranges optimize the balance between water absorbency and gel stability, preventing the gel from becoming too loose (which would reduce stability) or too crosslinked (which would reduce absorbency).
Solution Approach 2:
The patent creates a composite material system by combining polyacrylic acid with specific crosslinking agents (such as polyaluminum chloride, polyferric chloride, or aluminum sulfate) in controlled proportions. This composite structure provides both the high water absorbency of the polymer and the gel stability of the crosslinked network, resolving the contradiction between absorbency and stability.
2Quantity of substance
If water-absorbing resin is used to achieve high water absorbency, then liquid absorption capacity is improved, but anti-urine tolerance and temporal stability deteriorate
Solution Approach 1:
The patent controls the neutralization degree parameter within 30-80% and the crosslinking agent concentration at 0.01-5% by weight. These parameter optimizations ensure that the gel maintains its structural integrity over time while still achieving high water absorbency, thereby improving temporal stability without sacrificing absorbency.
Solution Approach 2:
By forming a composite material system with controlled crosslinking, the patent creates a gel structure that resists degradation over time. The crosslinked network provides temporal stability and anti-urine tolerance while the polyacrylic acid component maintains high water absorbency capabilities.
3Volume of moving object
If water-absorbing resin content is increased to reduce hydrophilic fiber amount, then material thickness is reduced, but liquid permeability deteriorates
Solution Approach 1:
The patent optimizes the water-absorbing resin content and crosslinking parameters to achieve a gel structure with appropriate porosity. By controlling the crosslinking degree and neutralization level, the gel maintains sufficient pore spaces for liquid permeability while achieving the desired thin profile through reduced fiber content.
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 water absorbent exhibits improved gel stability, higher absorbency, and enhanced liquid permeability, making it suitable for high-water-absorbing resin content sanitary materials with better handling and safety characteristics.
Implementation Method 1
this process is carried out by the liquid transportation caused by capillary phenomenon by which the liquid is transported through gaps of particles in the gel
Implementation Method 2
a method in which a water-soluble ethylene-based unsaturated monomer is polymerized by reverse-phase suspension polymerization in the presence of a cross-linking agent
Data Source
AI summary
An object of the present invention is to provide a water absorbent having excellent gel properties and showing excellent properties when used in a water-absorbing material of a sanitary/hygienic material such as paper diaper. Moreover, another object of the present invention is to provide a water absorbent which is safe and excellent in liquid permeability, and in which an amount of liquid permeability improver for improving the liquid permeability is reduced. The water absorbent is made from a water-absorbing resin prepared by a specific polymerization method and having a high degree of cross-linking, a high liquid holding property and a high gel strength (its swelling pressure of gel layer of is 35 kdyne/cm2 or more). This water absorbent is further processed to have a particular particle size distribution (95 wt % or more of its particles are less than 850ƒÊm but not less than 106ƒÊm, and logarithmic standard deviation (ƒĐƒÄ) is in a range of 0.25 to 0.45) and then surface cross-linked. After that, a liquid permeability improver is added therein.