Water Absorbing Agent Surface Crosslinking Temperature and Dew Point Control
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Solution Overview
Problem
Current methods for producing water absorbing agents in sanitary materials face challenges such as gel blocking, reduced productivity, and residual surface crosslinking agents, which affect the absorption capacity and industrial scalability, especially in thin sanitary products with high water absorbing agent content.
Innovation Solution
A method involving a polyacrylic acid (salt)-based water absorbing agent production process that includes a surface crosslinking step with a maximum temperature of 100 °C to 300 °C and a minimum dew point below 45 °C, along with a liquid permeability enhancer addition step, and recycling of fine particles to enhance productivity and reduce residual agents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the water absorbing agent content is increased to reduce sanitary material thickness, then the water absorption capacity is improved, but gel blocking occurs which reduces liquid diffusibility
Solution Approach 1:
The patent applies surface treatment to change the physical and chemical parameters of the water absorbing agent surface, specifically modifying surface crosslinking density and surface hydrophilicity. This allows the bulk material to maintain high absorption capacity while the surface maintains appropriate wettability and prevents gel blocking, enabling higher water absorbing agent content without proportionally increasing gel blocking effects.
Solution Approach 2:
The patent combines water absorbing agents with hydrophilic tissue in a composite structure where the hydrophilic tissue acts as a matrix or scaffold. This composite approach allows the water absorbing agent particles to be distributed within a hydrophilic network, preventing excessive gel formation and maintaining liquid pathways even at high water absorbing agent concentrations.
2Object-generated harmful factors
If surface crosslinking treatment is performed to prevent gel blocking, then liquid diffusibility is improved, but productivity decreases due to slow reaction speed
Solution Approach 1:
The patent optimizes surface crosslinking parameters including temperature, humidity, and crosslinking agent concentration to achieve effective surface treatment within shorter timeframes. By controlling environmental parameters and reaction conditions, the patent accelerates the surface crosslinking process while maintaining its effectiveness in preventing gel blocking.
Solution Approach 2:
The patent replaces traditional lengthy chemical crosslinking processes with alternative surface treatment methods that achieve similar or equivalent effects more rapidly. This may include using pre-crosslinked particles, spray coating with crosslinking agents, or other accelerated surface modification techniques that reduce processing time while maintaining functional benefits.
3Object-generated harmful factors
If surface crosslinking treatment is performed to improve liquid diffusibility, then absorption performance is enhanced, but residual crosslinking agent remains on the surface
Solution Approach 1:
The patent incorporates washing or extraction steps that remove residual crosslinking agents from the water absorbing agent surface after crosslinking treatment. This may involve rinsing with solvents, water, or other appropriate media that selectively remove unreacted crosslinking agent while preserving the crosslinked surface structure and its functional benefits.
Solution Approach 2:
The patent optimizes crosslinking reaction parameters such as temperature, time, and crosslinking agent dosage to maximize reaction completion and minimize residual agent. By carefully controlling these parameters, the patent achieves sufficient surface crosslinking for gel blocking prevention while reducing the amount of unreacted crosslinking agent that would require removal.
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 efficiently produces a water absorbing agent with high liquid permeability and antiblocking properties, reducing residual surface crosslinking agents and improving productivity, making it suitable for high-functionality, thin sanitary materials.
Implementation Method 1
a maximum temperature in an atmosphere within a heating section of a heating apparatus used in the surface crosslinking step is in a range from 100 °C to 300 °C
Implementation Method 2
a minimum dew point in the atmosphere is lower than 45 °C, and (1) an airflow rate in the heating apparatus is more than 0 but not more than 10,000 Nm3 /hr
Implementation Method 3
a water absorbing agent with high liquid permeability
Implementation Method 4
liquid permeability enhancer addition step
Data Source
AI summary
An object of the present invention is to provide a method for producing a water absorbing agent, whereby the ability to produce the water absorbing agent is enhanced or the amount of a residual surface crosslinking agent is reduced (or Anti-Caking property are enhanced) in the production of a water absorbing agent having high physical properties (particularly, high liquid permeability and Anti-Caking property), whereas the surface crosslinking step tends to be a rate-determining step in the current state of the art. In this method for producing a water absorbing agent, an additive selected from a polyvalent metal cation-containing compound, water-insoluble inorganic fine particles, and a cationic polymer compound is used, and surface crosslinking, particularly surface crosslinking with an alkylene carbonate compound, is performed under conditions where a temperature in a heat treatment system is controlled to be in a range from 100 °C to 300 °C, and a dew point in the heat treatment system is controlled to be lower than 45 °C.