Search

EP-3822305-B1 - PREPARATION METHOD OF SUPER ABSORBENT POLYMER

EP3822305B1EP 3822305 B1EP3822305 B1EP 3822305B1EP-3822305-B1

Inventors

  • KIM, TAE YUN
  • PARK, SUNG SOO
  • KIM, Gicheul

Dates

Publication Date
20260506
Application Date
20200618

Claims (13)

  1. A preparation method of a super absorbent polymer, comprising a step of mixing and drying fines having a particle diameter of 150 µ m or less, as measured by standard sieve analysis, obtained in the preparation step of a super absorbent polymer, a surface-modified inorganic material having a reactive functional group, and water to prepare a fines reassembly, wherein the surface-modified inorganic material has at least one reactive functional group selected from the group consisting of an epoxy group, an oxetane group, and an isocyanate group.
  2. The preparation method of a super absorbent polymer of Claim 1, wherein the fines having a particle diameter of 150 µ m or less comprises fines obtained by a first step of forming a hydrogel polymer by polymerizing a monomer mixture containing a water-soluble ethylene-based unsaturated monomer and a polymerization initiator; and a second step of drying and pulverizing the hydrogel polymer, and then performing classification into normal particles having a particle diameter of more than 150 µ m and 850 µ m or less and fines having a particle diameter of 150 µ m or less.
  3. The preparation method of a super absorbent polymer of Claim 1, wherein the fines having a particle diameter of 150 µ m or less comprises fines obtained by a first step of forming a hydrogel polymer by polymerizing a monomer mixture containing a water-soluble ethylene-based unsaturated monomer and a polymerization initiator; a second step of drying and pulverizing the hydrogel polymer, and then performing classification into normal particles having a particle diameter of more than 150 µ m and 850 µ m or less and fines having a particle diameter of 150 µ m or less; and a third step of surface cross-linking the normal particles, and then performing classification into surface cross-linked normal particles having a particle diameter of more than 150 µ m and 850 µ m or less and surface cross-linked fines having a particle diameter of 150 µ m or less.
  4. The preparation method of a super absorbent polymer of Claim 1, wherein the surface-modified inorganic material comprises silica, alumina, or a mixture thereof as the inorganic material.
  5. The preparation method of a super absorbent polymer of Claim 1, wherein the surface-modified inorganic material has an average particle diameter of 1 to 20 nm.
  6. The preparation method of a super absorbent polymer of Claim 1, wherein the surface-modified inorganic material is used in an amount of 0.01 to 1 parts by weight based on 100 parts by weight of the fines.
  7. The preparation method of a super absorbent polymer of Claim 1, wherein the water is added in an amount of 80 to 120 parts by weight based on 100 parts by weight of the fines.
  8. The preparation method of a super absorbent polymer of Claim 1, wherein a temperature of the water added in the preparation step of fines reassembly is 40 °C to 90 °C.
  9. The preparation method of a super absorbent polymer of Claim 1, wherein the drying in the preparation step of fines reassembly is performed at 120 °C to 220 °C.
  10. The preparation method of a super absorbent polymer of Claim 1, further comprising a step of classifying the fines reassembly obtained in the preparation step of fines reassembly into reassembly normal particles having a particle diameter of more than 150 µ m and 850 µ m or less and re-fines having a particle diameter of 150 µ m or less.
  11. The preparation method of a super absorbent polymer of Claim 10, wherein the re-fines are added in the preparation step of fines reassembly.
  12. The preparation method of a super absorbent polymer of Claim 2, further comprising a step of surface cross-linking the fines reassembly, or the fines reassembly and normal particles.
  13. The preparation method of a super absorbent polymer of Claim 12, further comprising a step of classifying the surface cross-linked super absorbent polymer obtained in the surface cross-linking step into surface cross-linked normal particles having a particle diameter of more than 150 µ m and 850 µ m or less and surface cross-linked fines having a particle diameter of 150 µ m or less, wherein the surface cross-linked fines are added in the preparation step of fines reassembly.

Description

[TECHNICAL FIELD] The present disclosure relates to a preparation method of a super absorbent polymer. [BACKGROUND OF ART] A super absorbent polymer (SAP) is a type of synthetic polymeric material capable of absorbing 500 to 1000 times its own weight of moisture. Such super absorbent polymers started to be practically applied in sanitary products, and they are now being widely used not only for hygiene products such as disposable diapers for children, etc., but also for water retaining soil products for gardening, water stop materials for the civil engineering and construction, sheets for raising seedling, fresh-keeping agents for food distribution fields, materials for poultices, or the like. An absorption mechanism of the super absorbent polymer is governed by interaction of penetration pressure due to the difference in electrical attraction caused by charges of a polymer electrolyte, affinity between water and a polymer electrolyte, molecular expansion due to repulsion between polymer electrolyte ions, and inhibition of expansion due to cross-linking. In other words, water absorbency of the super absorbent polymer depends on the affinity and molecular expansion, and an absorption rate is largely dependent on the osmotic pressure of the absorbent polymer itself. Meanwhile, particles having a particle diameter of 150 µm or less, which are inevitably generated in the preparation of a super absorbent polymer, are called fines, and it is known that the fines are generated in an amount of about 20 to 30% in the pulverization or transfer process during the preparation of a super absorbent polymer. When such fines are included in the super absorbent polymer, they may cause a reduction in main physical properties of the super absorbent polymer such as absorbency under pressure or water permeability. For this reason, during the preparation of a super absorbent polymer, particularly in a classification process, the fines are separated to produce the super absorbent polymer only with the remaining polymer particles. In addition, the separated fines are produced again into large particles by a reassembly process, and a preparation method of a super absorbent polymer using these reassembled particles is known. As a representative method of the reassembly method, a preparation method of a fine powder reassembly and a super absorbent polymer by mixing the fines with water is known. In the reassembly process, if the amount of water used is increased, cohesive strength of the fines increases, but a reassembled mass may be generated in the reassembly process, which may cause problems during operation of the process, and the amount of energy used during a drying process increases, resulting in high costs. Furthermore, if moisture is not properly removed by drying after reassembly, problems such as an increase in the load on the device for preparing a super absorbent polymer, and the like, may occur. Conversely, if the amount of water used in the reassembly process is reduced, there are disadvantages in that cohesive strength of the assembly is not sufficient, a generation amount of re-fines which are reduced into the fines without properly performing the reassembly process is greatly increased, and physical properties such as absorbency of the super absorbent polymer produced by the reassembly process are not sufficient. Accordingly, the development of a reassembly process of fines capable of solving the above-mentioned problems is continuously required. [DETAILED DESCRIPTION OF THE INVENTION] [Technical Problem] There is provided a preparation method of a super absorbent polymer that can solve the above-mentioned problems by mixing fines obtained inevitably in the process of preparing a super absorbent polymer with a surface-modified inorganic material having a reactive functional group. [Technical Solution] According to the present invention, there is provided a preparation method of a super absorbent polymer, comprising a step of mixing and drying fines having a particle diameter of 150 µm or less obtained in the preparation step of a super absorbent polymer, a surface-modified inorganic material having a reactive functional group, and water to prepare a fines reassembly, wherein the surface-modified inorganic material has at least one reactive functional group selected from the group consisting of an epoxy group, an oxetane group, and an isocyanate group. [ADVANTAGEOUS EFFECTS] According to an embodiment of the present disclosure, there is provided a preparation method of a super absorbent polymer exhibiting excellent absorption properties and mechanical properties such as crushing strength while having uniform particle size distribution by effectively reassembling fines obtained inevitably in the preparation of a super absorbent polymer. [DETAILED DESCRIPTION OF THE EMBODIMENTS] Hereinafter, a preparation method of a super absorbent polymer according to a specific embodiment of the present disclosure will be described.