UV Drum Reactor for SAP Surface Cross-Linking
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Solution Overview
Problem
Current surface cross-linking methods for superabsorbent polymer (SAP) particles are lengthy, often requiring high temperatures, leading to undesired side reactions and inhomogeneous cross-linking, which affects the stiffness and swelling capacity of SAPs, and result in reduced manufacturing efficiency.
Innovation Solution
A method using a drum reactor with UV radiation to apply radical former molecules onto SAP particles, allowing for rapid and controlled surface cross-linking at moderate temperatures, ensuring even distribution of cross-links on the surface while minimizing core modifications, thereby improving the homogeneity and efficiency of the process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional thermal surface cross-linking methods are used, then surface cross-linking is achieved, but the process time is long (at least 30 minutes) and temperature is high (150°C or above)
Solution Approach 1:
The patent replaces the thermal activation mechanism with photochemical activation using UV irradiation. Instead of using heat to initiate the cross-linking reaction between the surface cross-linking agent and carboxyl groups, the invention uses UV light to generate radicals that trigger the cross-linking process at room temperature, thereby dramatically reducing process time while maintaining cross-linking quality
Solution Approach 2:
The patent changes the activation parameter from thermal energy (temperature ≥150°C) to photochemical energy (UV irradiation). This parameter substitution allows the cross-linking reaction to proceed rapidly at room temperature, reducing process time from at least 30 minutes to a much shorter duration while achieving effective surface cross-linking
2Manufacturing precision
If prolonged surface cross-linking process is used, then cross-linking is achieved, but surface cross-linking agent penetrates into particles increasing core cross-linking and reducing capacity
Solution Approach 1:
The patent applies the surface cross-linking agent to the particle surface beforehand, then uses UV irradiation to initiate immediate cross-linking. This preliminary application followed by rapid photochemical activation ensures the agent reacts on the surface before it can penetrate into the particle core, maintaining high absorbent capacity while achieving uniform surface cross-linking
Solution Approach 2:
The patent uses UV irradiation to rush through the cross-linking process rapidly at room temperature. This fast photochemical reaction completes surface cross-linking in a short time, preventing the cross-linking agent from penetrating deeply into the particle core and thereby preserving the absorbent capacity while achieving the desired surface cross-linking effect
3Manufacturing precision
If high temperature thermal cross-linking is used, then cross-linking reaction is achieved, but side reactions occur and color degradation happens
Solution Approach 1:
The patent substitutes thermal activation with photochemical activation using UV irradiation. This replacement eliminates the need for high temperatures (≥150°C) that cause side reactions such as anhydride formation, dimer cleavage, and color degradation. The photochemical process proceeds at room temperature, maintaining cross-linking efficiency while avoiding harmful thermal side reactions
Solution Approach 2:
The patent changes the activation parameter from thermal energy to photochemical energy, enabling the cross-linking reaction to occur at room temperature under UV irradiation. This parameter change maintains sufficient cross-linking efficiency while eliminating the harmful effects associated with high-temperature processing, including side reactions and color degradation
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 enables faster and more uniform surface cross-linking of SAP particles, reducing gel-blocking and maintaining high swelling capacity, while minimizing energy costs and side reactions, resulting in improved manufacturing efficiency and product performance.
Implementation Method 1
The surface cross-linking reaction is achieved by heating to a temperature such that the peroxide radical initiator is decomposed while the polymer is not decomposed. Alternatively, the surface cross-linking reaction can also be achieved by a photo-irradiation treatment, preferably using ultraviolet rays.
Implementation Method 2
providing a reactor comprising a drum. The drum has a longitudinal axis and further has a cross-section. An irradiation source is provided such that the radiation emitted by the irradiation source is able to reach superabsorbent polymer particles within the drum and the irradiation source is able to emit UV radiation of a wavelength between 201 nm and 400 nm
Data Source
AI summary
The present invention relates to absorbent articles comprising superabsorbent polymer (SAP) particles, the SAP particles being made by a method of surface cross-linking superabsorbent polymer particles using UV irradiation. The method is carried out in a so-called drum reactor, which comprises a hollow drum and an irradiation source. The drum has a longitudinal axis and a cross-section. Radical former molecules are applied on the surface of superabsorbent polymer particles. These superabsorbent polymer particles are fed into the drum and are irradiated while they move within the drum, which is rotated around its longitudinal axis. The irradiation source is provided such that the radiation emitted by the irradiation source is able to reach superabsorbent polymer particles within said drum. The irradiation source for use in the method of the present invention is able to emit UV radiation of a wavelength between 201 nm and 400 nm.