Superabsorbent complexed with aluminum ions

Abstract

In an improved superabsorbent complexed with aluminum ions, the aluminum ions are applied in the form of an aqueous solution comprising aluminum ions, which has the feature that it comprises aluminum ions in a proportion within the range of 0.5%-15% by weight (converted if appropriate to Al.sup.3+), based on the total mass of the solution, and further comprises anions of lactic acid (lactate ions) and phosphoric acid (phosphate ions), where the molar proportion of the lactate ions is within the range of 0.01-2.99 times the molar amount of Al.sup.3+ and the molar proportion of the phosphate ions is within the range of 0.01-2.99 times the molar amount of Al.sup.3+.

Claims

1. A superabsorbent complexed with aluminum ions, where the aluminum ions are applied in the form of an aqueous solution comprising aluminum ions in a proportion within a range of 0.5%-15% by weight (converted to Al.sup.3+), based on a total mass of the solution, and further comprises anions of lactic acid (lactate ions) and phosphoric acid (phosphate ions), where a molar proportion of the lactate ions is within the range of 0.01-2.99 times a molar amount of Al.sup.3+ and a molar proportion of the phosphate ions is within the range of 0.01-2.99 times the molar amount of Al.sup.3+.

2. The superabsorbent according to claim 1, wherein the aluminum ions are applied in the form of an aqueous solution further comprising an anion of at least one third acid, where the third acid is selected from the group consisting of amino acids, carboxylic acids, citric acid, tartaric acid, malic acid, oxalic acid, glycolic acid, succinic acid, gluconic acid, glycine, acetic acid, sulfuric acid, and combinations thereof.

3. The superabsorbent according to claim 1, wherein the aluminum ions are applied in the form of an aqueous solution further comprising an addition of at least one further cation, where the cation is selected from the group consisting of alkali metal ions, alkaline earth metal ions, ammonium ions, cations of one or more transition metals or rare earth metals, and combinations thereof.

4. The superabsorbent according to claim 1, wherein the solution includes clusters having the theoretical composition Al.sup.3+.sub.A(C.sub.3H.sub.5O.sub.3.sup.−).sub.x-AS.sub.y-A.sup.M−(H.sub.2PO.sub.4.sup.−).sub.Z-A(OH.sup.−).sub.(3A-x-A.Math.M-y.Math.A-Z.Math.A) where S is the anion of an optionally present third acid having charge M, x is a value within a range of 0.01-2.99, y is a value within a range of 0-2.8, and z is a value within a range of 0.05-2.9.

5. The superabsorbent according to claim 4, wherein the aluminum ions are applied in the form of an aqueous solution in which (3A-x.Math.A-M.Math.y.Math.A-z.Math.A)>0.

6. The superabsorbent according to claim 1 wherein the solution comprises not more than 5% by weight of sulfate ions.

7. The superabsorbent according to claim 1, which is surface postcrosslinked with postcrosslinkers that form covalent bonds with polar groups at a surface of the superabsorbent particles.

8. The superabsorbent according to claim 1, which has been complexed with at least 0.008% by weight and at most 0.15% by weight of aluminum, calculated in each case as the metal and based on the total amount of the anhydrous superabsorbent.

9. The superabsorbent according to claim 4, which has been complexed with at least 0.020% by weight and at most 0.05% by weight of aluminum, calculated in each case as the metal and based on the total amount of the anhydrous superabsorbent.

10. A process for producing a superabsorbent by polymerizing an aqueous monomer solution comprising a) at least one ethylenically unsaturated monomer which bears an acid group and is optionally at least partly in salt form, b) at least one crosslinker, c) at least one initiator, d) optionally one or more ethylenically unsaturated monomer copolymerizable with the monomer mentioned under a), e) optionally one or more water-soluble polymer, the process further comprising drying of the resulting polymer, optionally grinding of the dried polymer and sieving of the ground polymer, optionally surface postcrosslinking of the dried and optionally ground and sieved polymer, and adding an aqueous solution comprising aluminum ions, which comprises aluminum ions in a proportion within the range of 0.5%-15% by weight (converted to Al.sup.3+), based on the total mass of the solution, and further comprises anions of lactic acid (lactate ions) and phosphoric acid (phosphate ions), where a molar proportion of the lactate ions is within the range of 0.01-2.99 times a molar amount of Al.sup.3+ and a molar proportion of the phosphate ions is within the range of 0.01-2.99 times the molar amount of Al.sup.3+.

11. The process according to claim 10, wherein the solution comprising aluminum ions comprises not more than 5% by weight of sulfate ions.

12. An article for absorption of fluids, comprising a superabsorbent defined in claim 1.

13. A process for producing articles for absorption of fluid, wherein the production of the articles comprises adding a superabsorbent defined in claim 1.

14. The superabsorbent according to claim 3 wherein the cation is selected from the group consisting of Na.sup.+, K.sup.+, Ca.sup.2+, Mg.sup.2+, Zr.sup.2+, NH.sub.4.sup.+, and combinations thereof.

15. The superabsorbent according to claim 4 wherein x is the value within the range of 0.75-2.0, y is the value within the range of 0-1.25, and z is the value within the range of 0.2-1.5.

Description

EXAMPLES

(1) Bruggolite® FF6 is a mixture of the disodium salt of 2-hydroxy-2-sulfinatoacetic acid, the disodium salt of 2-hydroxy-2-sulfonatoacetic acid and sodium bisulfite, available from L. Bruggemann KG, Salzstrasse 131, 74076 Heilbronn, Germany

(2) Laromer® LR 9015X is the triacrylate of fifteen-tuply ethoxylated trimethylolpropane, available from BASF SE, Ludwigshafen, Germany. DAROCUR® 1173 is 2-hydroxy-2-methyl-1-phenylpropan-1-one, available from BASF Schweiz AG, Basle, Switzerland. IRGACURE® 651 is 2,2-dimethoxy-1,2-diphenylethan-1-one, likewise available from BASF Schweiz AG, Basle, Switzerland.

(3) Lohtragon® ALA 200 is 20% by weight aqueous solution of aluminum dihydroxymonoacetate, available from Dr. Paul Lohmann GmbH KG, 31857 Emmerthal, Germany. Lohtragon® ACE is an aqueous solution, obtainable from the same source, of aluminum dihydroxymonoacetate having an aluminum content of 4.2% by weight. The aluminum salt solutions identified here by their batch numbers can likewise be purchased from that source.

(4) The mixer used in the examples for surface postcrosslinking and complexation was a Pflugschar® M5 plowshare mixer with a heating jacket from Gebr. Lödige Maschinenbau GmbH; Elsener Strasse 7-9, 33102 Paderborn, Germany. To measure the temperature of the product in the mixer, a thermocouple was introduced into the opening provided for the purpose in the mixer to such an extent that its tip was at a distance from the heated inner wall of the mixer and was within the product, but could not be impacted by the mixing tools.

(5) In the examples, the aluminum salt solutions in table 1 below were used. These were produced by initially charging the water in a reaction vessel, adding aluminum hydroxide hydrate while stirring, adding lactic acid, phosphoric acid and acids of the other anions mentioned in each case, and stirring the resulting mixture. The salt solutions mentioned are also obtainable from Dr. Paul Lohmann GmbH KG, Hauptstrasse 2, 31860 Emmerthal, Germany.

(6) TABLE-US-00001 TABLE 1 (all amounts stated in % by weight based on the solution) Batch No. Al Lactate PO.sub.4.sup.3− Others OH.sup.− H.sub.2O 1085250 3.3 5.5 5.9 maleate, 8.1 3.0 74.2 1085251 2.7 8.9 4.8 — 2.3 80.1 1085252 3.7 10.2 6.5 citrate, 1.4 3.1 75.1 1086562 3.4 9.8 1.8 sulfate, 5.3 7.3 72.4 1086563 3.3 4.9 7.0 sulfate, 5.3 5.9 73.6 1099550 3.0 13.2 9.9 — 1.6 72.3 1099551 4.1 — 16.7 sulfate, 12.7 2.5 64.0 1099552 3.0 — 11.4 sulfate, 17.3 1.6 66.7

Example 1

(7) 1 kg of superabsorbent base polymer (HySorb® T 9600 base polymer, surface nonpostcrosslinked crosslinked polymer of acrylic acid and sodium acrylate with neutralization level 72 mol %, available from BASF SE, Ludwigshafen, Germany) was initially charged in a mixer. At 40° C. and a shaft speed of 200 revolutions per minute, by means of a two-phase spray nozzle, a solution of 10 g of propane-1,2-diol, 1 g of a mixture of equal parts by weight of 2-hydroxyethyloxazolidinone (HEONON) and propane-1,3-diol, and 40 g of the aluminum salt solution batch #1085250 were sprayed on. Subsequently, the shaft speed was reduced to 70 revolutions per minute, and the product temperature was increased to 180° C. within 5 to 10 minutes and then maintained for 80 minutes.

(8) Over this period, after 20, 30, 40, 50, 60 and 70 minutes, the mixer was stopped briefly and a sample of about 10 g of product was taken each time. All samples and the remaining amount of the product after 80 minutes were left to cool down to room temperature. The finished product was obtained by sieving to the particle size range from 150 μm to 710 μm. The measurements reported in table 2 were measured on the samples and on the finished product thus obtained by sieving.

Example 2

(9) Example 1 was repeated, except that the solution of batch #1085250 was replaced with solution of batch #1085251. The measurements obtained are reported in table 2.

Example 3

(10) Example 1 was repeated, except that the solution of batch #1085250 was replaced with solution of batch #1085252. The measurements obtained are reported in table 2.

Example 4

(11) Example 1 was repeated, except that the solution of batch #1085250 was replaced with solution of batch #1085262. The measurements obtained are reported in table 2.

Example 5

(12) Example 1 was repeated, except that the solution of batch #1085250 was replaced with solution of batch #1085263. The measurements obtained are reported in table 2.

(13) Evaluation

(14) Examples 1 to 5 show how the gel stiffness rises over the reaction time of the complexation, recognizable by the AUL value. Good to excellent GBP values are achieved with only slightly impaired CRC values.

Example 6

(15) 1 kg of superabsorbent base polymer (HySorb® T 9600 base polymer, surface nonpostcrosslinked crosslinked polymer of acrylic acid and sodium acrylate with neutralization level 72 mol %, available from BASF SE, Ludwigshafen, Germany) was initially charged in a mixer. At 40° C. and a shaft speed of 200 revolutions per minute, by means of a two-phase spray nozzle, a solution of 10 g of propane-1,2-diol, 1 g of a mixture of equal parts by weight of 2-hydroxyethyloxazolidinone (HEONON) and propane-1,3-diol, and 26.7 g of the aluminum salt solution batch #1099550 were sprayed on. Subsequently, the shaft speed was reduced to 70 revolutions per minute, and the product temperature was increased to 190° C. within 5 to 10 minutes and then maintained for 80 minutes. Over this period, after 20, 30, 40, 50, 60 and 70 minutes, the mixer was stopped briefly and a sample of about 10 g of product was taken each time. All samples and the remaining amount of the product after 80 minutes were left to cool down to room temperature. Thereafter, the product was left to cool down to room temperature. The finished product was obtained by sieving to the particle size range from 150 μm to 710 μm. The measurements reported in table 3 were measured on the samples and on the product thus obtained by sieving.

Example 6a

(16) Example 6 was repeated, but kept at 190° C. for only 45 min and without taking of samples. The measurements are reported in table 4.

(17) TABLE-US-00002 TABLE 2 (in all tables “—” means not determined) 1 2 3 4 5 Ex. AUL AUL AUL AUL AUL Time CRC 0.7 psi GBP CRC 0.7 psi GBP CRC 0.7 psi GBP CRC 0.7 psi GBP CRC 0.7 psi GBP [min] [g/g] [g/g] [Da] [g/g] [g/g] [Da] [g/g] [g/g] [Da] [g/g] [g/g] [Da] [g/g] [g/g] [Da] 20 40.9 8.4 — 33.2 22.4 — 33.3 21.0 — 31.2 21.9 — 31.2 21.7 — 30 38.8 13.7 — 31.5 22.1 — 30.2 21.4 — 29.4 21.8 — 29.8 22.0 — 40 35.9 19.1 — 31.1 21.7 — 31.0 20.9 — 28.9 21.5 — 30.7 21.7 — 50 35.1 21.7 — 29.7 21.5 — 30.2 21 — 29.2 20.9 — 28.7 21.1 — 60 36.1 22.7 — 28.4 21.2 — 28.8 20.6 — 26.5 20.6 — 26.8 20.4 — 70 34.9 22.9 — 26.5 20.8 — 27.5 20.4 — 26.8 20.3 — 28.3 20.3 — 80 33.2 23.2 29.4 27.8 20.4 77.6 28.4 20.4 64.6 28.8 20.2 76.8 27.0 20.4 52.2

(18) TABLE-US-00003 TABLE 3 6 7 8 AUL AUL AUL Ex. 0.7 0.7 0.7 Time CRC psi GBP CRC psi GBP CRC psi GBP [min] [g/g] [g/g] [Da] [g/g] [g/g] [Da] [g/g] [g/g] [Da] 20 39.5 9.3 — 41.1 8.4 — 41.6 7.3 — 30 36.2 15.8 — 37.1 17.5 — 39.2 10.7 — 40 34.2 18.4 — 34.6 20.5 — 37.7 15.8 — 50 34.2 19.2 52.4 33.1 20.8 3.9 36.6 19.0 — 60 32.6 19.2 — 35.4 20.5 — 36.0 20.9 — 70 32.2 18.9 — 31.7 20.3 — 34.6 20.9 — 80 31.0 19.4 60.3 30.9 20.0 8.0 34.0 21.0 7.3

(19) TABLE-US-00004 TABLE 4 AUL Time CRC 0.7 psi GBP Initial color Color after 7 days Color after 14 days Example [min] [g/g] [g/g] [Da] L a b L a b L a b 6a 45 34.4 18.7 44.2 93.7 −0.8 4.9 68.5 6.3 17.4 45 11 19 7a 45 35.0 20.6 3.6 90.9 −0.6 4.1 59.4 8.2 20.6 31 11 13 8 80 34.0 21.0 7.3 93.1 −0.6 4.4 60.7 7.9 19.9 33 11 14

Example 7 (Comparative)

(20) Example 6 was repeated, except that the 26.7 g of solution of batch #1099550 were replaced with 19.5 g of solution of batch #1099551. The measurements obtained are reported in table 3.

Example 7a (Comparative)

(21) Example 7 was repeated, but kept at 190° C. for only 45 min and without taking of samples. The measurements are reported in table 4.

Example 8 (Comparative)

(22) Example 6 was repeated, except that the solution of batch #1099550 was replaced by solution of batch #1099552 and the temperature after application of the surface postcrosslinking solution was increased to 180° C. rather than 190° C.

(23) The measurements show that neither in the case of the equivalent replacement of lactate with sulfate (3 mol of sulfate rather than 6 mol of lactate, i.e. replacement taking account of valency) in examples 7 and 7a nor in the case of equimolar replacement (1 mol of sulfate rather than 1 mol of lactate) in example 8 is the permeability or the color stability of the superabsorbents of the invention attained. This shows that solubility of aluminum phosphate can be achieved via addition of sulfate, but the use of this combination of salts in superabsorbents brings disadvantages compared to the superabsorbents of the invention.