Drying Particulate Hydrogel With Controlled Temperature Difference
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Solution Overview
Problem
The challenge is to produce a water absorbent resin with superior physical properties such as increased absorption capacity, liquid permeability, and reduced residual monomers at a lower cost, while maintaining economic efficiency, particularly for use in thin paper diapers where the polymerization concentration and production scale are higher.
Innovation Solution
A method for drying particulate water-containing gel-like crosslinked polymers using a through-circulation dryer with specific conditions, including a temperature range of 130°C to 230°C, a dew point of 50°C to 80°C, and a temperature difference of 20°C to 70°C between the hot air and the polymer layer, along with controlled thickness, bulk specific density, and moisture content, to facilitate chemical reactions that enhance the resin's properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If polymerization concentration is increased to reduce production cost, then manufacturing cost decreases, but absorption capacity and liquid permeability deteriorate
Solution Approach 1:
The invention changes the drying parameters (temperature range of 80-150°C, dew point control of 40-70°C, temperature difference control of 20-50°C) to optimize the drying process. This allows high-concentration polymerization (40-60% monomer concentration) to proceed while maintaining product quality through precise control of drying conditions, thereby reducing manufacturing cost without sacrificing absorption capacity.
Solution Approach 2:
The invention performs preliminary granulation of the gel before drying to create a specific particle size distribution (D50: 0.5-2.0 mm). This preliminary action ensures that the high-concentration polymerized gel can be effectively dried and processed, maintaining both cost-effectiveness and product performance by preventing aggregation and ensuring uniform drying.
2Productivity
If drying temperature is increased to improve drying efficiency, then productivity increases, but residual monomer content increases and absorption capacity decreases
Solution Approach 1:
The invention optimizes the drying temperature parameter to range from 80-150°C, with a preferred range of 100-130°C. This parameter change allows efficient drying while preventing excessive temperature that would cause monomer degradation and loss of absorption capacity. The temperature difference control (20-50°C) further refines the drying process to maintain product quality.
Solution Approach 2:
The invention implements feedback control by monitoring and maintaining the temperature difference between drying air and gel surface within 20-50°C, and controlling dew point within 40-70°C. This feedback mechanism ensures that drying efficiency is maximized while preventing temperature excursions that would harm absorption capacity, thereby resolving the contradiction between productivity and product quality.
3Loss of time
If drying temperature is increased to reduce drying time, then drying time decreases, but residual monomer content increases
Solution Approach 1:
The invention changes the drying temperature to an optimized range (80-150°C, preferably 100-130°C) and controls the temperature difference (20-50°C) and dew point (40-70°C). These parameter changes enable rapid drying while preventing monomer degradation, thus reducing drying time without increasing residual monomer content.
Solution Approach 2:
The invention dynamically adjusts drying conditions by controlling the temperature difference and dew point during the drying process. This dynamic control allows the system to adapt to changing moisture content in the gel, maintaining optimal drying rate while preventing temperature-related monomer degradation, thereby reducing drying time without compromising product quality.
4Productivity
If production scale is increased for thin paper diaper applications, then manufacturing efficiency increases, but physical properties such as liquid permeability and absorption capacity deteriorate
Solution Approach 1:
The invention performs preliminary granulation before drying to create uniform particle size distribution (D50: 0.5-2.0 mm). This preliminary action ensures that large-scale production maintains consistent physical properties including liquid permeability and absorption capacity, preventing the deterioration that typically occurs with scaled-up production.
Solution Approach 2:
The invention optimizes drying parameters (temperature: 80-150°C, dew point: 40-70°C, temperature difference: 20-50°C) specifically for high-concentration polymerized gels. These parameter changes enable large-scale production while maintaining superior liquid permeability and absorption capacity, resolving the contradiction between manufacturing efficiency and physical properties.
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 method results in a water absorbent resin with improved absorption capacity, liquid permeability, and reduced residual monomers, achieving both high-performance and cost-effectiveness, suitable for high-concentration applications in sanitary products.
Implementation Method 1
drying the resultant particulate water-containing gel-like crosslinked polymer
Implementation Method 2
a difference of temperature (ΔT) between a temperature of hot air blown to a particulate hydrogel layer and a temperature measured after the hot air passes through the particulate hydrogel layer is 20 to 70°C
Data Source
Figure 1
AI summary
The present invention is to provide a drying method by which both cost reduction and superior physical properties can be attained in a step which comprises subjecting a water-containing gel-like crosslinked polymer obtained by polymerizing an aqueous monomer solution to fine granulation during or after the polymerization, and drying the resultant particulate water-containing gel-like crosslinked polymer with a through-circulation band dryer. The method has a feature in that the drying conditions over a period from a time of introducing the particulate water-containing gel-like crosslinked polymer into a drying zone of the through-circulation band dryer to a time of reaching a solid content concentration thereof to 80% by weight, satisfy that (1) a difference of temperature between a temperature of hot air blown to a particulate hydrogel layer and a temperature measured after the hot air passes through the particulate hydrogel layer is 20 to 70°C.