Cryogenic Grinding Superabsorbent Polymers
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Solution Overview
Problem
Current methods for producing superabsorbent polymers face challenges in achieving high swelling rates while maintaining quality, and require complex and energy-intensive processes for comminuting hydrogels, often necessitating the use of foaming agents and resulting in a higher proportion of fine particles.
Innovation Solution
A process involving radical polymerization of ethylenically unsaturated acid group-containing monomers, followed by coarse crushing, cooling, and cryogenic grinding before drying, which allows for improved swelling rates and simpler comminution without the disadvantages of prior art methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the hydrogel is frozen and then comminuted using a system consisting of rotating blades, then the pore structure is preserved, but a foaming agent must be used to maintain the surface pore structure and higher energy consumption is required
Solution Approach 1:
The patent changes the physical state parameter of the hydrogel from solid to frozen state before comminution. By freezing the hydrogel, the pore structure is preserved and maintained during the grinding process, eliminating the need for foaming agents and reducing energy consumption compared to comminuting the hydrogel in a frozen state using conventional methods
2Stability of the object's composition
If the hydrogel is frozen and then comminuted using a system consisting of rotating blades, then the pore structure is preserved, but a higher proportion of fine particles is obtained
Solution Approach 1:
The patent segments the comminution process into multiple stages using different grinding media. First, a coarse grinding stage is performed to break the hydrogel into larger fragments, followed by a finer grinding stage to achieve the desired particle size. This segmentation allows for better control over particle size distribution while preserving the pore structure
3Ease of manufacture
If drying is carried out first, followed by cryogenic grinding, then the process is simpler, but the swelling rate is reduced
Solution Approach 1:
The patent performs comminution of the hydrogel before drying and before freezing. By performing the comminution action in advance while the hydrogel is still in its gel state, the particle size is reduced and the surface area is increased, which enhances the swelling rate in subsequent applications. The hydrogel is then dried and packaged as usual
4Reliability
If the polymer particles are modified after drying and comminution, then surface modification can improve absorption properties, but the process becomes more complex and energy-intensive
Solution Approach 1:
The patent performs comminution and surface area enhancement before drying and packaging. By reducing the particle size and increasing the surface area in advance, the absorption properties are improved without requiring additional surface modification steps after drying. This preliminary action simplifies the overall process while maintaining or enhancing absorption performance
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 simpler comminution of superabsorbent polymers, maintaining quality and reducing energy expenditure, with the ability to adjust particle size before drying, enhancing absorption capacity and permeability.
Implementation Method 1
cooling the pre-comminuted untreated hydrogel polymer in the cooling area with at least one cooling zone for a period of 30 seconds to 3600 seconds, wherein the cooling area has a temperature gradient
Implementation Method 2
radical polymerization of acid-group-bearing monomers in the presence of crosslinking agents
Data Source
AI summary
The invention relates to a method for producing a water-absorbing polymer, comprising the following steps: (i) mixing (a1) 0.1 to 99.99 wt.%, preferably 20 to 98.99 wt.%, and particularly preferably 30 to 98.95 wt.% of polymerized, ethylenically unsaturated, acid-group-containing monomers or the salts thereof, or polymerized, ethylenically unsaturated monomers containing a protonated or quarternized nitrogen, or the mixtures thereof, wherein mixtures containing at least ethylenically unsaturated, acid-group-containing monomers, preferably acrylic acid, are particularly preferred, optionally partially neutralized, (a2) 0 to 70 wt.%, preferably 1 to 60 wt.%, and particularly preferably 1 to 40 wt.% of polymerized, ethylenically unsaturated monomers that can be copolymerized with (a1), (a3) 0.001 to 10 wt.%, preferably 0.01 to 7 wt.%, and particularly preferably 0.05 to 5 wt.% of one or more cross-linking agents, (a4) 0 to 30 wt.%, preferably 1 to 20 wt.%, and particularly preferably 5 to 10 wt.% of water-soluble polymers, and (a5) 0 to 20 wt.%, preferably 0.01 to 7 wt.%, and particularly preferably 0.05 to 5 wt.% of one or more auxiliary substances, wherein the sum of the weights (a1) to (a5) is 100 wt.%; (ii) radically polymerizing, with cross-linking, so as to form a water-insoluble, aqueous untreated hydrogel polymer; (iii) coarsely comminuting the untreated hydrogel polymer into pieces having a diameter in the range of 0.1 mm to 5.0 cm; (iv) cooling the pre-comminuted untreated hydrogel polymer and grinding the cooled untreated hydrogel polymer; (v) drying the comminuted untreated hydrogel polymer after grinding at a temperature in the range of 85ºC to 260ºC and sifting the dried pieces in the range of 150 µm to 850 µm; (vi) post-crosslinking the hydrogel polymer; and (vii) drying and packaging the water-absorbing polymer. The invention further relates to the use thereof.