Superabsorbent Production via Multi-Step Neutralization
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Solution Overview
Problem
The production of superabsorbents often results in high levels of residual monomers, which is a challenge in achieving consistent quality and performance in applications such as hygiene products and market gardening.
Innovation Solution
A process involving the preparation of partly neutralized acrylic acid through a multi-step neutralization process, where over-neutralized acrylic acid with a degree of neutralization of at least 100.1 mol-% is mixed with neutralized acrylic acid having a degree of neutralization from 50 to 85 mol-%, with specific control over dimeric acrylic acid content, followed by polymerization, drying, grinding, and classification, to produce superabsorbents with a constant low level of residual monomers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional neutralization process is used to prepare acrylic acid for superabsorbent production, then the process is simple and quick, but the residual monomer content in the resulting superabsorbents is high
Solution Approach 1:
The neutralization process is divided into multiple sequential steps with different neutralization degrees. First, acrylic acid is neutralized to a degree of 100-105% to form over-neutralized acrylic acid. Then, this over-neutralized acrylic acid is mixed with additional acrylic acid and neutralized again to achieve the final neutralization degree of 50-85%. This segmentation allows each step to serve a specific function in controlling residual monomer content.
Solution Approach 2:
The first neutralization step creates over-neutralized acrylic acid in advance, which is then used in the second neutralization step. This preliminary action of creating over-neutralized acrylic acid allows for better control of the final neutralization process and results in lower residual monomer content in the superabsorbents.
2Manufacturing precision
If the dimeric acrylic acid content is not controlled in the monomer solution, then the polymerization process is simpler, but the quality consistency of superabsorbents deteriorates
Solution Approach 1:
The content of dimeric acrylic acid is monitored and controlled within specific ranges (0.1-0.5% in acrylic acid 1, 0.05-0.2% in acrylic acid 2). This feedback control ensures that the polymerization process produces superabsorbents with consistent quality and performance characteristics.
3Productivity
If a single-step neutralization is used, then the production time is shorter, but the centrifuge retention capacity and absorption performance of superabsorbents are reduced
Solution Approach 1:
The neutralization process is divided into multiple sequential steps with different neutralization degrees. First, acrylic acid is neutralized to a degree of 100-105% to form over-neutralized acrylic acid. Then, this over-neutralized acrylic acid is mixed with additional acrylic acid and neutralized again to achieve the final neutralization degree of 50-85%. This segmentation allows each step to serve a specific function in controlling residual monomer content.
Solution Approach 2:
The first neutralization step creates over-neutralized acrylic acid in advance, which is then used in the second neutralization step. This preliminary action of creating over-neutralized acrylic acid allows for better control of the final neutralization process and results in lower residual monomer 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 process effectively reduces residual monomer content in superabsorbents, enhancing their centrifuge retention capacity, absorption under high load, and saline flow conductivity, thereby improving their performance and processing characteristics.
Implementation Method 1
preparing an over-neutralized acrylic acid having a degree of neutralization of at least 100.1 mol-% by mixing an acrylic acid 1 and a base and preparing a neutralized acrylic acid having a degree of neutralization from 50 to 85 mol-% by mixing the over-neutralized acrylic acid and an acrylic acid 2
Implementation Method 2
polymerization of a monomer solution, comprising a) partly neutralized acrylic acid, b) at least one crosslinker, c) at least one initiator
Implementation Method 3
drying, grinding and classifying the resulting polymer gel
Data Source
AI summary
The invention relates to a process for producing superabsorbents, comprising the preparation of partly neutralized acrylic acid by the steps (i) preparing an over-neutralized acrylic acid having a degree of neutralization of at least 100.1 mol-% by mixing of an acrylic acid 1 and a base and (ii) preparing a neutralized acrylic acid having a degree of neutralization from 50 to 85 mol-% by mixing of the over-neutralized acrylic acid and an acrylic acid 2, wherein the content of dimeric acrylic acid in the acrylic acid 2 is lower than the content of dimeric acrylic acid in the acrylic acid 1.