Super Absorbent Polymer Surface Cross-Linking Shape Rupture
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing super-absorbent polymers face challenges in achieving uniform internal cross-linking, leading to difficulties in maintaining shape integrity under pressure while maintaining excellent absorption abilities, due to high reactivity of internal cross-linking agents and low water solubility of acryl cross-linking agents.
Innovation Solution
A method involving polyfunctional nitroxide mediated radical polymerization, followed by surface cross-linking using alkylenediamine, to create a super-absorbent polymer with improved shape rupture resistance and absorption capabilities, characterized by specific water-retention and swollen gel rupture index criteria.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If an internal cross-linking agent is used to improve shape rupture resistance, then shape rupture resistance is improved, but the cross-linking agent is exhausted at an initial stage of the reaction due to higher reactivity, resulting in non-uniform cross-linking structure
Solution Approach 1:
The patent applies preliminary action by introducing a surface cross-linking step after polymerization. The polymer particles are first polymerized with internal cross-linking, then subjected to surface cross-linking treatment with silane coupling agents or other cross-linking agents under controlled conditions. This two-stage approach ensures uniform cross-linking structure by addressing the exhaustion problem of internal cross-linking agents through subsequent surface cross-linking, thereby improving shape rupture resistance while maintaining structural uniformity.
Solution Approach 2:
The patent utilizes parameter changes by controlling the timing and conditions of cross-linking reactions. The polymerization and cross-linking are conducted at different stages with different temperature, time, and reagent concentration parameters. This allows optimization of both uniformity and strength by adjusting reaction parameters at each stage, preventing premature exhaustion of cross-linking agents while achieving desired shape rupture resistance.
2Strength
If an acryl internal cross-linking agent is used to improve shape rupture resistance, then shape rupture resistance is improved, but the acryl internal cross-linking agent has low solubility in water, causing difficulty in producing a uniform polymer composition
Solution Approach 1:
The patent employs an intermediary approach by using water-soluble cross-linking agents or surfactants to facilitate the dissolution and uniform distribution of acryl cross-linking agents in the aqueous polymerization medium. This intermediary substance enables the hydrophobic cross-linking agent to be uniformly dispersed, ensuring homogeneous polymer composition while maintaining shape rupture resistance. The intermediary acts as a bridge between the incompatible phases, resolving the solubility issue.
3Device complexity
If conventional polymerization methods are used to simplify the process, then process simplicity is maintained, but uniform internal cross-linking cannot be achieved, leading to poor shape rupture resistance
Solution Approach 1:
The patent applies segmentation by dividing the polymerization process into distinct stages: polymerization stage and cross-linking stage. Each stage has specific objectives and controlled parameters. This segmented approach allows optimization of each stage independently, achieving uniform internal cross-linking and improved shape rupture resistance without excessive overall process complexity. The clear separation of stages makes the process manageable and controllable.
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 results in a super-absorbent polymer with enhanced shape rupture resistance under pressure and maintained absorption ability, preventing gel strength reduction and skin irritation in applications like disposable diapers.
Implementation Method 1
polymerizing a polymeric compound containing an acrylic monomer by using a polyfunctional nitroxide mediated radical polymerization initiator
Implementation Method 2
substituting a terminal of the polymer prepared in the polymerization step with maleic anhydride
Implementation Method 3
cross-linking each maleic anhydride terminal of different polymers prepared in the substitution step by using alkylenediamine having 2 to 8 carbon atoms
Implementation Method 4
A super-absorbent polymer is a functional resin having an ability of absorbing water of several tens to thousands of times the weight of the polymer and keeping the same therein
Implementation Method 5
polymerizing a polymer mixture including an ethylene unsaturated carboxyl containing monomer, a cross-linking agent, a comonomer copolymerisable with the carboxyl containing monomer, and a polymerization medium to form a cross-linked hydrogel
Data Source
AI summary
A super-absorbent polymer satisfying Equation 1 exhibits remarkably improved shape rupture under pressure while maintaining excellent absorption ability. The super-absorbent polymer may be prepared by preparing a base resin by polymerizing a polymeric compound containing an acrylic monomer by using a polyfunctional nitroxide mediated radical polymerization initiator, substituting a terminal of the polymer prepared in the polymerization step with maleic anhydride, cross-linking each maleic anhydride terminal of different polymers prepared in the substitution step by using alkylenediamine having 2 to 8 carbon atoms, drying and grinding the base resin, and surface cross-linking the ground base resin.