High water-absorbent resin having crush resistance and method for manufacturing same

Abstract

Disclosed are a surface-modified superabsorbent polymer and a method of preparing the same, wherein a superabsorbent polymer is surface-modified with the addition of a water-soluble salt having a multivalent cation and superhydrophobic microparticles, thereby improving attrition resistance, permeability and absorption speed without significantly deteriorating the other properties thereof.

Claims

1. A surface-modified superabsorbent polymer, which is obtained using a water-soluble salt having a multivalent cation and particles having i) a BET specific surface area of 300 to 1500 m.sup.2/g and ii) a porosity of 50% or more.

2. The surface-modified superabsorbent polymer of claim 1, wherein the water-soluble salt having a multivalent cation is used in an amount of 0.001 to 5.0 parts by weight based on 100 parts by weight of the superabsorbent polymer.

3. The surface-modified superabsorbent polymer of claim 1, wherein the cation of the water-soluble salt having a multivalent cation comprises any one or more selected from the group consisting of Al.sup.3+, Zr.sup.4+, Sc.sup.3+, Ti.sup.4+, V.sup.5+, Cr.sup.3+, Mn.sup.2+, Fe.sup.3+, Ni.sup.2+, Cu.sup.2+, Zn.sup.2+, Ag.sup.+, Pt.sup.4+, and Au.sup.+, and an anion thereof comprises any one or more selected from the group consisting of a sulfuric acid group (SO.sub.4.sup.2), a sulfurous acid group (SO.sub.3.sup.2), a nitric acid group (NO.sub.3.sup.), a metaphosphoric acid group (PO.sub.3.sup.), and a phosphoric acid group (PO.sub.4.sup.3).

4. The surface-modified superabsorbent polymer of claim 3, wherein the water-soluble salt having a multivalent cation is aluminum sulfate (Al.sub.2(SO.sub.4).sub.3) or zirconium sulfate (Zr(SO.sub.4).sub.2).

5. The surface-modified superabsorbent polymer of claim 1, wherein the particles have a particle size ranging from 2 nm to 50 m.

6. The surface-modified superabsorbent polymer of claim 1, wherein the particles have superhydrophobicity with a water contact angle of 125 or more.

7. The surface-modified superabsorbent polymer of claim 1, wherein the particles have a particle size ranging from 2 nm to 50 m and superhydrophobicity with a water contact angle of 125 or more.

8. The surface-modified superabsorbent polymer of claim 1, wherein the particles have a BET specific surface area of 500 to 1500 m.sup.2/g.

9. The surface-modified superabsorbent polymer of claim 1, wherein the particles have a BET specific surface area of 700 to 1500 m.sup.2/g.

10. The surface-modified superabsorbent polymer of claim 6, wherein the particles have superhydrophobicity with a water contact angle of 140 or more.

11. The surface-modified superabsorbent polymer of claim 6, wherein the particles have superhydrophobicity with a water contact angle of 145 or more.

12. The surface-modified superabsorbent polymer of claim 1, wherein the particles have a porosity of 90% or more.

13. A method of preparing a surface-modified superabsorbent polymer, comprising: a) providing a superabsorbent polymer; b) adding the superabsorbent polymer provided in a) with particles having i) a BET specific surface area of 300 to 1500 m.sup.2/g and ii) a porosity of 50% or more; and c) adding the superabsorbent polymer pre-treated in b) with a water-soluble salt having a multivalent cation and mixing them together to thereby modify a surface of the superabsorbent polymer.

14. The method of claim 13, further comprising milling the surface-modified superabsorbent polymer so that the milled superabsorbent polymer is sorted into particles having a size of less than 150 m, particles having a size from 150 m to less than 300 m, particles having a size from 300 m to less than 600 m, particles having a size from 600 m to less than 850 m, and particles having a size of 850 m or more.

15. The method of claim 13, wherein the cation of the water-soluble salt having a multivalent cation comprises any one or more selected from the group consisting of Al.sup.3+, Zr.sup.4+, Sc.sup.3+, Ti.sup.4+, V.sup.5+, Cr.sup.3+, Mn.sup.2+, Fe.sup.3+, Ni.sup.2+, Cu.sup.2+, Zn.sup.2+, Ag.sup.+, Pt.sup.4+, and Au.sup.+, and an anion thereof comprises any one or more selected from the group consisting of a sulfuric acid group (SO.sub.4.sup.2), a sulfurous acid group (SO.sub.3.sup.2), a nitric acid group (NO.sub.3.sup.), a metaphosphoric acid group (PO.sub.3.sup.), and a phosphoric acid group (PO.sub.4.sup.3).

16. The method of claim 13, wherein the water-soluble salt having a multivalent cation is aluminum sulfate (Al.sub.2(SO.sub.4).sub.3) or zirconium sulfate (Zr(SO.sub.4).sub.2).

17. The method of claim 13, wherein the particles have a particle size ranging from 2 nm to 50 m.

18. The method of claim 13, wherein the particles have superhydrophobicity with a water contact angle of 125 or more.

19. The method of claim 13, wherein the particles have a particle size ranging from 2 nm to 50 m and superhydrophobicity with a water contact angle of 125 or more.

20. The method of claim 13, wherein the particles have a BET specific surface area of 500 to 1500 m.sup.2/g.

21. The method of claim 13, wherein the particles have a BET specific surface area of 700 to 1500 m.sup.2/g.

22. The method of claim 18, wherein the particles have superhydrophobicity with a water contact angle of 140 or more.

23. The method of claim 18, wherein the particles have superhydrophobicity with a water contact angle of 145 or more.

24. The method of claim 18, wherein the particles have a porosity of 90% or more.

25. The method of claim 13, wherein the particles having i) a BET specific surface area of 300 to 1500 m.sup.2/g and ii) a porosity of 50% or more are used in an amount of 0.001 to 5.0 parts by weight based on 100 parts by weight of the superabsorbent polymer.

26. The method of claim 13, wherein the water-soluble salt having a multivalent cation is used in an amount of 0.001 to 5.0 parts by weight based on 100 parts by weight of the superabsorbent polymer.

Description

EXAMPLES

Preparation Example: Preparation of Superabsorbent Polymer

(1) 100 g of acrylic acid, 0.3 g of polyethyleneglycol diacrylate as a crosslinking agent, 0.033 g of diphenyl(2,4,6-trimethylbenzoyl)-phosphine oxide as an initiator, 38.9 g of sodium hydroxide (NaOH), and 103.9 g of water were mixed, thus preparing a monomer mixture having a monomer concentration of 50 wt %. The monomer mixture was then placed on a continuously moving conveyor belt and irradiated with UV light (at 2 mW/cm.sup.2) so that UV polymerization was carried out for 2 min, thus obtaining a hydrogel polymer.

(2) The hydrogel polymer thus obtained was cut to a size of 55 mm, dried in a hot air oven at 170 C. for 2 hr, ground using a pin mill, and then sorted using a sieve, thereby obtaining a superabsorbent polymer having a particle size of 150 to 850 m. Thereafter, the superabsorbent polymer was surface-crosslinked using 3.5% ethyleneglycol diglycidyl ether, reacted at 120 C. for 1 hr, ground, and then sorted using a sieve, yielding a surface-treated superabsorbent polymer having a particle size of 150 to 850 m.

Examples: Preparation of Surface-Modified Superabsorbent Polymer

Example 1

(3) 250 g of the superabsorbent polymer obtained in the Preparation Example described above and 0.15 g of porous superhydrophobic microparticles, namely, silica Aerogel (AeroZel, JIOS), were placed in a stirrer and stirred at 1000 rpm for 60 sec.

(4) Thereafter, an aqueous solution of 1.6 g of zirconium sulfate.4H.sub.2O dissolved in 6.25 g of water was added, followed by stirring for 180 sec. The resulting mixture was then aged for 30 min and sorted using a sieve, thus obtaining a superabsorbent polymer having a particle size of 150 to 850 m.

(5) The Aerogel used had a particle size of 5 m, a BET specific surface area of 700 m.sup.2/g, a water contact angle of 144, and a porosity of 95%.

(6) The particle size of the Aerogel was measured through Laser Diffraction using a HELOS (Helium-Neon Laser Optical System) based on ISO 13320. The BET specific surface area and porosity thereof were measured using a BET analyzer. The water contact angle was measured using a contact angle analyzer (KRUSS DSA100), and was specifically determined in a manner in which a piece of double-sided tape was attached to a flat glass plate, microparticles were applied in a monolayer thereon, and then 5 L of ultrapure water was placed in the form of a drop on the monolayer, and the angle between the water drop and the glass plate was measured four times and averaged.

Example 2

(7) A surface-modified superabsorbent polymer was obtained in the same manner as in Example 1, with the exception that 1.6 g of aluminum sulfate.14-18H.sub.2O was used, instead of the zirconium sulfate.4H.sub.2O.

Comparative Example 1

(8) 250 g of the superabsorbent polymer prepared in the Preparation Example described above was used.

(9) The conditions of Examples 1 and 2 and Comparative Example 1 are summarized in Table 1 below.

(10) TABLE-US-00001 TABLE 1 Superhydrophobic Microparticles (g) Multivalent ions (g) Water (g) Ex. 1 0.15 1.6 (zirconium sulfate4H.sub.2O) 6.25 Ex. 2 0.15 1.6 (aluminum sulfate14-18H.sub.2O) 6.25 C. Ex. 1 0 0 0

Test Examples: Evaluation of Properties

(11) In order to evaluate the properties of the surface-modified superabsorbent polymers, the following tests were performed.

Test Example 1: Particle Size of Superabsorbent Polymer

(12) The superabsorbent polymers of Examples 1 and 2 and Comparative Example 1 were measured for particle size. The particle size of the superabsorbent polymer was measured using the EDANA method WSP 240.3. 100 g of the superabsorbent polymer was vibrated for 10 min under conditions of amplitude of 1.44 mm and a vibration frequency of 50 Hz using 850 m, 600 m, 300 m, and 150 m mesh sieves from Pan, after which the amount remaining on each sieve was determined. The results are shown in Table 2 below.

(13) TABLE-US-00002 TABLE 2 Particle size distribution (%) 150 m 150 to 300 300 to 600 600 to 850 850 m or less m m m or more Ex. 1 0.5 20.6 68.2 10.8 0.0 Ex. 2 1.5 26.3 64.1 8.1 0.0 C. Ex. 1 0.4 22.4 67.5 9.5 0.0

(14) As is apparent from Table 2, showing the particle size distribution of the superabsorbent polymers of Examples 1 and 2 and Comparative Example 1, even when 3.5% of water was added to the superabsorbent polymer in Examples 1 and 2, compared to Comparative Example 1, the similar particle size distribution resulted. This is because agglomeration by water was reduced due to the effects of the superhydrophobic microparticles used in the examples.

Test Example 2: Centrifugal Retention Capacity (CRC)

(15) The superabsorbent polymers of Examples 1 and 2 and Comparative Example 1 were measured for CRC before and after ball milling. CRC was measured using the EDANA method WSP 241.3. Specifically, 0.2 g of a sample of the prepared superabsorbent polymer, having a particle size of 300 to 600 m, was placed in a teabag and then immersed in a 0.9% saline solution for 30 min. Thereafter, dehydration was performed for 3 min by centrifugal force of 250 G (gravity), and the amount of saline solution that was absorbed was measured. The results are shown in Table 3 below.

Test Example 3: Absorption Under Pressure (AUP)

(16) The superabsorbent polymers of Examples 1 and 2 and Comparative Example 1 were measured for AUP before and after ball milling Specifically, 0.16 g of a sample of the prepared superabsorbent polymer, having a particle size of 300 to 600 m, was placed in a cylinder, and a pressure of 0.9 psi was applied using a piston and a weight. Thereafter, the amount of 0.9% saline solution that was absorbed in 60 min was measured. The results are shown in Table 3 below.

Test Example 4: Permeability (Sec)

(17) The superabsorbent polymers of Examples 1 and 2 and Comparative Example 1 were measured for permeability before and after ball milling. In order to prevent the generation of bubbles between a cock and a glass filter in the lower portion of a chromatography column, about 10 mL of water was added in the opposite direction into the column, and the column was washed two or three times with saline and then filled with at least 40 mL of 0.9% saline. A piston was placed in the chromatography column, the lower valve was opened, and the period of time (B: sec) required for the liquid surface to move from 40 mL to 20 mL was recorded, thus completing blank testing. 0.2 g of a sample of the prepared superabsorbent polymer, having a particle size ranging from 300 to 600 m, was placed in the column, and then saline was added such that the total amount of saline that resulted was 50 mL, after which the sample was allowed to stand for 30 min so that the superabsorbent polymer was sufficiently swollen. Thereafter, the piston with a weight (0.3 psi) was placed in the chromatography column and then allowed to stand for 1 min. The cock at the bottom of the chromatography column was opened, and the period of time (T1: sec) required for the liquid surface to move from 40 mL to 20 mL was recorded. The permeability was determined based on the following Equation 1. The results are shown in Table 3 below.
Permeability=T1B[Equation 1]

Test Example 5: Speed of Absorption

(18) The superabsorbent polymers of Examples 1 and 2 and Comparative Example 1 were measured for the speed of absorption before and after ball milling 50 mL of 0.9% saline was placed in a 100 mL beaker using a precision divider, magnetic bars were also placed therein, and the 100 mL beaker was placed on a magnetic stirrer preset at a rate of 600 rpm, followed by stirring. Thereafter, 2.00.05 g of a sample having a size of 300 to 600 m was added to a vortex, and the period of time required until the vortex disappeared was measured. The results are shown in Table 3 below.

Test Example 6: Ball Milling

(19) In order to evaluate attrition resistance of the superabsorbent polymers of Examples 1 and 2 and Comparative Example 1, a ball milling test was performed. To this end, a ball mill, a jar, and alumina balls were used. The maximum rotational speed of the ball mill was 350 rpm, and was set to 300 rpm in this test example. The jar had an inner diameter of about 10 cm, with a total volume of 1 L. Also, ten alumina balls having a diameter of 2.5 cm were used. 20 g of the superabsorbent polymer having a particle size of 300 to 600 m was placed in the jar, and ball milling was performed for 20 min. After ball milling, a superabsorbent polymer having a particle size of 300 to 600 m was separated again from among the milled superabsorbent polymer particles, and thus the percentage value was determined by diving the difference in weight between the superabsorbent polymer having a particle size of 300 to 600 m before ball milling and the superabsorbent polymer having a particle size of 300 to 600 m after ball milling by the weight of the superabsorbent polymer having a particle size of 300 to 600 m before ball milling ((the weight of the superabsorbent polymer having a particle size of 300 to 600 m before ball millingthe weight of the superabsorbent polymer having a particle size of 300 to 600 m after ball milling)/the weight of the superabsorbent polymer having a particle size of 300 to 600 m before ball milling) The results are shown in Table 3 below.

(20) TABLE-US-00003 TABLE 3 300 to Speed 600 m Perme- of Ab- *Moisture Particle Ball CRC AUP ability sorption Content Size Milling (g/g) (g/g) (sec) (sec) (%) Variation Ex. 1 Before 32.7 13.8 15 67 3.53 8.3 After 33.4 12.5 18 68 Ex. 2 Before 32.6 14.4 18 65 3.52 7.5 After 33.6 13.5 23 63 C. Before 33.9 16.1 32 81 1.26 11.5 Ex. 1 After 34.9 13.6 64 83 *Moisture content was measured in the last step for treating the superabsorbent polymer with Aerogel, water-soluble salt and water during the preparation of the superabsorbent polymers of Examples 1 and 2 and Comparative Example 1.

(21) As is apparent from Table 3, the superabsorbent polymers of Examples 1 and 2, which were treated with the superhydrophobic microparticles and the water-soluble salt aqueous solution having a multivalent cation according to the present invention, were improved in permeability, compared to the conventional superabsorbent polymer. In particular, the speed of absorption was much higher in Examples 1 and 2 than in Comparative Example 1.

(22) Based on the results of generation of fine powder after ball milling of Table 3, the amount of fine powder was low in Examples 1 and 2. This is because the superhydrophobic microparticles and the multivalent ions (zirconium sulfate or aluminum sulfate) are introduced to the surface of the superabsorbent polymer, and thus 3.5% of water is in the polymer as is apparent from the results of moisture content, thus increasing attrition resistance to thereby reduce the generation of fine powder.