Water-absorbing polymer process using coarse blowing agent
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Solution Overview
Problem
Current methods for producing water-absorbing polymers with high absorption rates face challenges such as rapid conversion of azo compounds and dispersion issues, leading to suboptimal swelling rates and microporous structure formation, while existing blowing agents often escape or form larger bubbles, compromising the absorption properties of superabsorbent hydrogels.
Innovation Solution
A process involving the use of granulated sodium carbonate with a layered structure as a blowing agent in a kneading reactor, where the blowing agent is added before polymerization initiation, ensuring uniform distribution and controlled release of carbon dioxide, resulting in a higher swelling rate and improved absorption properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If azo compounds are used as blowing agents, then absorption capacity increases, but conversion is rapid and dispersion is poor leading to separation
Solution Approach 1:
The patent changes the particle size parameter of the blowing agent from fine (1-100 μm) to coarse (200-800 μm), which fundamentally alters the dispersion behavior and stability of the blowing agent in the monomer solution, preventing separation while maintaining absorption capacity
Solution Approach 2:
The patent creates local quality differences by using a layered structure of blowing agent granules with different densities, where heavier particles settle first and lighter particles remain suspended, ensuring uniform distribution throughout the reaction mixture
2Quantity of substance
If inorganic blowing agents are used, then absorption and absorption under pressure increase, but blowing agent escapes before or during gel formation
Solution Approach 1:
The patent changes the size parameter of the blowing agent particles to a large scale (200-800 μm), which slows down the release kinetics of carbon dioxide, allowing the blowing agent to remain trapped in the gel matrix longer and release gas gradually during and after gel formation
Solution Approach 2:
The patent performs preliminary action by adding the blowing agent before polymerization initiation, ensuring it is distributed throughout the monomer solution before the gel network forms, so that the blowing agent becomes trapped in the gel structure and releases gas at the appropriate time
3Speed
If blowing agents are added to monomer solution, then swelling rate increases, but larger bubbles form that do not ensure microporous structure
Solution Approach 1:
The patent changes the particle size parameter of the blowing agent to coarse granules (200-800 μm), which mechanically limits bubble coalescence and ensures formation of fine, uniform micropores throughout the hydrogel matrix, preventing large bubble formation
Solution Approach 2:
The patent uses the coarse blowing agent granules as a template to create a controlled microporous structure in the hydrogel, where the granule size directly determines the pore size distribution, ensuring uniform micropores rather than large irregular bubbles
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 process achieves a higher swelling rate and absorption efficiency of water-absorbing polymers, maintaining overall quality and ensuring uniform distribution of blowing agents, which enhances the polymer's ability to quickly absorb liquids without forming barrier layers.
Implementation Method 1
the blowing agent consists of granules made of soda particles
Implementation Method 2
ensuring uniform distribution and controlled release of carbon dioxide
Implementation Method 3
water-absorbing polymers with a high absorption rate
Data Source
AI summary
The invention relates to a process for producing a water-absorbing polymer composition, comprising the process steps of (i) mixing (a1) 0.1 to 99.999% by weight, preferably 20 to 98.99% by weight and more preferably 30 to 98.95% by weight of polymerized, ethylenically unsaturated monomers containing acid groups or salts thereof or polymerized, ethylenically unsaturated monomers including a protonated or quaternized nitrogen, or mixtures thereof, particular preference being given to mixtures including at least ethylenically unsaturated monomers containing acid groups, preferably acrylic acid, (a2) 0 to 70% by weight, preferably 1 to 60% by weight and more preferably 1 to 40% by weight of polymerized, ethylenically unsaturated monomers copolymerizable with (a1), (a3) 0.001 to 10% by weight, preferably 0.01 to 7% by weight and more preferably 0.05 to 5% by weight of one or more crosslinkers, (a4) 0 to 30% by weight, preferably 1 to 20% by weight and more preferably 5 to 10% by weight of water-soluble polymers, and (a5) 0 to 20% by weight, preferably 0.01 to 7% by weight and more preferably 0.05 to 5% by weight of one or more assistants, where the sum of their weights (a1) to (a5) is 100% by weight, (ii) free-radical polymerization with crosslinking to form a water-insoluble aqueous untreated hydrogel polymer, (iii) comminuting and drying the hydrogel polymer, (iv) optionally grinding and sieving the water-absorbing polymer, (v) surface postcrosslinking the ground hydrogel polymer and (vi) drying and finishing the water-absorbing polymer, wherein blowing agents having a particle size of 100 µm to 900 µm are added to the aqueous monomer solution prior to the addition of the initiator and the start of the free-radical polymerization.