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US-12616956-B2 - Super absorbent polymer based on polyacrylic acid or its salts

US12616956B2US 12616956 B2US12616956 B2US 12616956B2US-12616956-B2

Abstract

A super absorbent polymer may have a capillary constant of 0.4 mm 5 or more as derived using n-hexane. The super absorbent polymer may be a polyacrylic acid (salt)-based super absorbent polymer. The super absorbent polymer may have a fast absorption rate and an improved absorption capacity, resulting in improved performance.

Inventors

  • Taewan Kim
  • Seokhyeon Baek
  • Sung Soo Park
  • Kwangin Shin
  • Kyung Inn KIM
  • Jung Eun SONG
  • Minhwa Shin

Assignees

  • LG CHEM, LTD.

Dates

Publication Date
20260505
Application Date
20241218
Priority Date
20240516

Claims (11)

  1. 1 . A polyacrylic acid (salt)-based super absorbent polymer, wherein the polyacrylic acid (salt)-based super absorbent polymer has a capillary constant of 0.4 mm 5 or more as derived using n-hexane, and wherein when the polyacrylic acid (salt)-based super absorbent polymer is swelled in water having an electrical conductivity value of 100 to 130 μS/cm for 1 minute, a maximum capacity of water that the polyacrylic acid (salt)-based super absorbent polymer is able to hold (free swelling capacity) is 130 g/g or more.
  2. 2 . The polyacrylic acid (salt)-based super absorbent polymer of claim 1 , wherein the capillary constant is 1.5 mm 5 or less.
  3. 3 . The polyacrylic acid (salt)-based super absorbent polymer of claim 1 , wherein a surface area to volume ratio of the super absorbent polymer is 43 mm −1 or more.
  4. 4 . The polyacrylic acid (salt)-based super absorbent polymer of claim 1 , wherein a surface area to volume ratio of the super absorbent polymer is 65 mm −1 or less.
  5. 5 . The polyacrylic acid (salt)-based super absorbent polymer of claim 1 , wherein the polyacrylic acid (salt)-based super absorbent polymer has an average convexity value of 0.94 or less for all particles, calculated using Equation 1: M c = L s / L [ Equation ⁢ 1 ] wherein, in Equation 1, M c is convexity, L s is a length of a perimeter of a polygon of minimal perimeter that surrounds a two-dimensional (2D) image of a three-dimensional (3D) particle to be measured, and L is an actual perimeter length of the 2D image of the 3D particle to be measured.
  6. 6 . The polyacrylic acid (salt)-based super absorbent polymer of claim 1 , wherein the polyacrylic acid (salt)-based super absorbent polymer has an average circle equivalent (CE) diameter of 220 μm to 400 μm.
  7. 7 . The polyacrylic acid (salt)-based super absorbent polymer of claim 1 , wherein the polyacrylic acid (salt)-based super absorbent polymer has an extractable component content of 10 wt % or less based on a total weight of the polyacrylic acid (salt)-based super absorbent polymer, measured after free swelling in water having an electrical conductivity of 100 to 130 μS/cm for 30 minutes.
  8. 8 . The polyacrylic acid (salt)-based super absorbent polymer of claim 1 , wherein the polyacrylic acid (salt)-based super absorbent polymer has an extractable component content of 17 wt % or less based on a total weight of the super absorbent polymer, measured after free swelling in water having an electrical conductivity of 100 to 130 μS/cm for 3 hours.
  9. 9 . The polyacrylic acid (salt)-based super absorbent polymer of claim 1 , wherein the polyacrylic acid (salt)-based super absorbent polymer has an absorbency under pressure (AUP) of 28 g/g or more measured under 0.3 psi according to EDANA method WSP 242.3.
  10. 10 . The polyacrylic acid (salt)-based super absorbent polymer of claim 1 , wherein the polyacrylic acid (salt)-based super absorbent polymer has a centrifuge retention capacity (CRC) of 33 g/g or more measured according to EDANA method WSP 241.3.
  11. 11 . The polyacrylic acid (salt)-based super absorbent polymer of claim 1 , wherein the polyacrylic acid (salt)-based super absorbent polymer has an effective absorption capacity (EFFC) of 30 g/g or more, calculated by Equation 2: EFFC = ( C ⁢ R ⁢ C + A ⁢ UP ) / 2 [ Equation ⁢ 2 ] wherein, in Equation 2, CRC is a centrifuge retention capacity (units: g/g) measured according to EDANA method WSP 241.3, and AUP is an absorbency under pressure (units: g/g) measured under 0.3 psi according to EDANA method WSP 242.3.

Description

CROSS-REFERENCE TO RELATED APPLICATION This application claims priority to Korean Patent Application No. 10-2024-0064067, filed on May 16, 2024, the disclosure of which is incorporated herein by reference in its entirety. TECHNICAL FIELD The present disclosure relates to a super absorbent polymer exhibiting an improved absorption rate and improved absorption performance. BACKGROUND A super absorbent polymer (SAP) is a synthetic polymer material that can absorb 500 to 1,000 times its own weight in moisture, and is named differently by each developer, such as super absorbent material (SAM) and absorbent gel material (AGM). The super absorbent polymers described above began to be put to practical use as sanitary products, and are now widely used as soil water retainers for horticulture, water-retaining materials for civil engineering and construction, sheets for raising seedlings, and freshness-preserving agents and materials for steaming in the food distribution industry. In particular, since super absorbent polymers are widely used in the field of sanitary products such as diapers and sanitary pads, they need to exhibit not only high absorption performance but also a fast absorption rate. In addition, the development of so-called pulpless products, in which the pulp content is reduced or even no pulp is used at all, is being actively pursued in order to provide thinner products. As a result, the product includes a relatively high proportion of a super absorbent polymer, and super absorbent polymer particles are inevitably included in multiple layers within the product. Accordingly, the importance of the absorption rate of super absorbent polymers is increasing. To this end, a method is commonly used in which a foaming agent is included in the monomer composition to form a porous structure within the base resin powder as crosslinking polymerization progresses, thereby increasing the surface area of the super absorbent polymer. However, a problem occurred in which overall properties of the super absorbent polymer, such as surface tension, liquid permeability, or bulk density, were reduced depending on the use of the foaming agent. Conversely, when the crosslinking density of the super absorbent polymer is controlled to be high in order to improve the overall properties of the super absorbent polymer, there is a problem in that the centrifuge retention capacity, which is a basic property of the super absorbent polymer, is reduced because it is difficult to absorb moisture between the dense crosslinked structures. Accordingly, there is a continuous demand for the development of super absorbent polymers that improve the absorption rate of super absorbent polymers while maintaining the basic properties of super absorbent polymers. SUMMARY The present disclosure is directed to providing a super absorbent polymer (SAP) having excellent fluid absorption capacity due to capillary action, thereby having a fast absorption rate and excellent absorption capacity. The present disclosure relates to a polyacrylic acid (salt)-based super absorbent polymer, wherein the super absorbent polymer has a capillary constant of 0.4 mm5 or more as derived using n-hexane. BRIEF DESCRIPTION OF THE DRAWINGS The above and other objects, features and advantages of the present disclosure will become more apparent to those of ordinary skill in the art by describing exemplary aspects thereof in detail with reference to the accompanying drawings, in which: FIG. 1 shows the setting values of a sample dispersion unit in Morphologi 4 from Malvern Panalytical; FIG. 2 shows the illumination setting values in Morphologi 4 from Malvern Panalytical; FIG. 3 shows the optics selection setting values in Morphologi 4 from Malvern Panalytical; and FIG. 4 shows the scan area setting values in Morphologi 4 from Malvern Panalytical. DETAILED DESCRIPTION Unless otherwise defined herein, all technical and scientific terms used herein are used for the purpose of describing exemplary aspects only and are not intended to be limiting on the disclosure. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this disclosure, the terms “comprises,” “includes,” or “has” and the like are intended to designate the presence of the features, numbers, steps, components, or combinations thereof that are implemented, and are not to be understood as precluding the possibility of the presence or addition of one or more other features or numbers, steps, components or combinations thereof. While aspects of the disclosure are susceptible to various modifications and forms, specific aspects thereof will be exemplified and described in detail below. However, this is not intended to limit the present disclosure to specific aspects, and it should be understood to include all modifications, equivalents and substitutes included in the spirit and scope of the present disclosure. The terminology used herein is for the purpose of describing particu