Super absorbent polymer
A polyacrylic acid (salt)-based super absorbent polymer has a T2 relaxation time of 1.85×10 −5 seconds or less, as derived by exponential fitting of the TD-NMR measurement results of the super absorbent polymer through regression analysis using the following Equation 1: y = y 0 + A × e - ( x t ) wherein, y represents a signal intensity obtained through TD-NMR analysis, x represents an echo time determined from specified experimental parameters: first duration; last duration; and a data point, t represents a T2 relaxation time derived by exponential fitting, A represents a signal intensity value derived by exponential fitting, and y0 represents an offset constant derived through regression analysis.
1 . A polyacrylic acid (salt)-based super absorbent polymer,
wherein a T2 relaxation time is 1.85×10 −5 seconds or less, as derived by exponential fitting of the TD-NMR measurement results of the super absorbent polymer through regression analysis using the following Equation 1:
y
=
y
0
+
A
×
e
-
(
x
t
)
[
Equation
l
]
wherein,
y represents a signal intensity obtained through TD-NMR analysis,
x represents an echo time,
t represents a T2 relaxation time derived by exponential fitting,
A represents a signal intensity value derived by exponential fitting, and
y0 represents an offset constant derived through regression analysis.
2 . The super absorbent polymer of claim 1 , wherein the T2 relaxation time is 1.60×10 −5 seconds or more.
3 . The super absorbent polymer of claim 1 , wherein the super absorbent polymer has an average convexity value of 0.94 or less for all particles of the super absorbent polymer, as calculated using the following Equation 2:
M
c
=
L
s
/
L
[
Equation
2
]
wherein,
M c represents convexity,
L s represents a length of an elastic band assuming that an image obtained by capturing, as a 2D image, a 3D image of the 3D particle to be measured is surrounded by an imaginary elastic band that stretches around the contour, and
L represents an actual circumferential length of an image obtained by capturing, as a 2D image, a 3D image of the 3D particle to be measured.
4 . The super absorbent polymer of claim 1 , wherein the super absorbent polymer has an extractable component content of 10 wt % or less based on a total weight of the super absorbent polymer, as measured after free swelling in water having an electrical conductivity of 100 to 130 μS/cm for 30 minutes.
5 . The super absorbent polymer of claim 1 , wherein the super absorbent polymer has an extractable component content of 17 wt % or less based on a total weight of the super absorbent polymer, as measured after free swelling in water having an electrical conductivity of 100 to 130 μS/cm for 3 hours.
6 . The super absorbent polymer of claim 1 , wherein the super absorbent polymer has an absorbency under pressure (AUP) of 28 g/g or more, as measured under 0.3 psi according to the EDANA method WSP 242.3.
7 . The super absorbent polymer of claim 1 , wherein the super absorbent polymer has a centrifuge retention capacity (CRC) of 30.8 g/g or more, as measured according to EDANA method WSP 241.3.
8 . The super absorbent polymer of claim 1 , wherein the super absorbent polymer has an effective absorption capacity (EFFC) of 30 g/g or more, as calculated by the following Equation 3:
EFFC
=
(
C
R
C
+
AUP
)
/
2
[
Equation
3
]
wherein,
CRC represents a centrifuge retention capacity (units: g/g) as measured according to EDANA method WSP 241.3, and
AUP represents an absorbency under pressure (units: g/g) as measured under 0.3 psi according to EDANA method WSP 242.3.
9 . The super absorbent polymer of claim 1 , wherein the super absorbent polymer has an absorption rate (vortex time) of 40 seconds or less, as measured by a vortex measurement method at 24.0° C.
10 . The super absorbent polymer of claim 1 , wherein when the super absorbent polymer is swollen in water having an electrical conductivity value of 100 to 130 μS/cm for 1 minute, a maximum capacity of water that the super absorbent polymer is able to hold (free swelling capacity) is 138 g/g or more.
11 . The super absorbent polymer of claim 1 , wherein the super absorbent polymer has a liquid permeability of 65 ml or more, as calculated by the following Equation 4:
Perm
=
[
20
mL
/
T
1
(
sec
)
]
×
60
sec
[
Equation
4
]
wherein,
Perm represents liquid permeability, and
T1 represents the time (seconds) taken for 20 mL of saline to pass through a swollen super absorbent polymer under a pressure of 0.3 psi after placing 0.2 g of a super absorbent polymer in a cylinder, the swollen super absorbent polymer is prepared by pouring saline (0.9 wt % sodium chloride aqueous solution) so that the super absorbent polymer is completely submerged, and allowing the super absorbent polymer to swell for 30 minutes.