Water Absorbent Resin Drying via Peroxide Control
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Solution Overview
Problem
The challenge of maintaining physical properties of water absorbent resins during high concentration polymerization and drying, particularly the deterioration of water absorption capacity and increased water extractables, is significant when scaling up production, leading to additional costs and complex operations due to issues like non-dried products and the use of additives which can further degrade properties.
Innovation Solution
The method involves reducing the amount of water-soluble peroxides in the hydrogel to 1-100 ppm before drying at high temperatures using a through-circulation belt dryer, which helps maintain the physical properties of the water absorbent resin by controlling the persulfate salt content and performing a heat treatment before the drying step.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high concentration polymerization is used to improve productivity, then production efficiency increases, but physical properties of the water absorbent resin deteriorate (water absorption capacity decreases, water extractables increase)
Solution Approach 1:
The patent applies preliminary action by performing a heat treatment step before the drying step to reduce peroxide content in the hydrogel. This preliminary reduction of peroxide prevents deterioration of physical properties during subsequent high-temperature drying, enabling high concentration polymerization to proceed while maintaining product quality.
Solution Approach 2:
The patent changes the parameter of peroxide content by controlling it to be 1-100 ppm in the hydrogel before drying. This parameter control allows the use of high concentration polymerization (improving productivity) while preventing physical property deterioration through optimized peroxide levels.
2Productivity
If high temperature drying is used to improve drying efficiency, then drying speed increases, but physical properties of the water absorbent resin deteriorate
Solution Approach 1:
The patent performs a preliminary heat treatment step before the main drying step to reduce peroxide content. This preliminary action protects the hydrogel from peroxide-induced deterioration during high-temperature drying, allowing fast drying without sacrificing physical properties.
Solution Approach 2:
The patent extracts and removes peroxide from the hydrogel through heat treatment before drying. By taking out the harmful peroxide component, the patent enables high-temperature drying to proceed efficiently without causing physical property deterioration.
3Reliability
If peroxide is reduced in the hydrogel to maintain physical properties, then water absorption capacity is improved, but drying time increases
Solution Approach 1:
The patent segments the drying process into two distinct steps: a preliminary heat treatment step to reduce peroxide content, and a main high-temperature drying step to remove water. This segmentation allows peroxide reduction without significantly extending total drying time, as the main drying step can proceed efficiently at high temperature once peroxide is reduced.
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
This approach effectively suppresses the deterioration of physical properties, achieving a water absorbent resin with improved water absorption capacity, reduced water extractables, and enhanced liquid permeability without requiring expensive facilities or additional steps, thus improving productivity and maintaining high concentration polymerization benefits.
Implementation Method 1
a drying step in a drying apparatus to dry a particulate hydrogel crosslinked polymer
Implementation Method 2
through-circulation belt dryer
Implementation Method 3
a step of reducing peroxide to perform a heat treatment of the particulate hydrogel crosslinked polymer at the temperature of less than 160°C before the drying step
Data Source
Figure 1
AI summary
In a method for producing a water absorbent resin by drying a particulate hydrogel having a high solid content concentration (of 45% by weight or more, preferably 50% by weight or more, and more preferably 55% by weight or more), a method for efficient drying water absorbent resin having maintained/improved physical properties is provided. Disclosed is a method for producing a water absorbent resin, comprising: a polymerization step to polymerize an unsaturated monomer, and; a drying step to dry a particulate hydrogel crosslinked polymer, which is obtained by micronization of a hydrogel polymer during or after the polymerization and which has a solid content concentration of 45% by weight or more, wherein, an amount of a peroxide in the particulate hydrogel crosslinked polymer to be dried in the drying step is 1 to 100 ppm relative to the weight of the solid content of the particulate hydrogel crosslinked polymer, and a drying temperature of the particulate hydrogel crosslinked polymer in the drying step is 160°C or more.