# US 12,110,351 B2 · Method for the production of superabsorbers

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- Number: US 12,110,351 B2
- Document ID: US12110351B2
- Status: Granted
- Kind: B2
- Application number: 17/717,598
- Filed: 2022-04-11
- Published: 2022-07-28
- Granted: 2024-10-08
- Earliest claimed: 2016-08-10
- Assignees: BASF SE
- Applicants: BASF SE
- Inventors: Kristine Hartnagel; Thomas Gieger; Thomas Daniel; Marcus Schroeder; Michelle Morano; Nathaniel Troy Greene
- Web page: https://patentgrep.com/patent/US12110351B2

## CPC

- C08F 2/22: Emulsion polymerisation
- A61L 15/60: Liquid-swellable gel-forming materials, e.g. super-absorbents
- B01J 20/261: {obtained by reactions only involving carbon to carbon unsaturated bonds (macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds per se C08F)}
- B01J 20/28047: {Gels}
- C08F 2/01: characterised by special features of the polymerisation apparatus used
- C08F 2/44: Polymerisation in the presence of compounding ingredients, e.g. plasticisers, dyestuffs, fillers
- C08F 6/14: Treatment of polymer emulsions {(C08F6/001, C08F6/006, C08F6/008, C08F6/02, C08F6/04 take precedence)}
- C08F 220/06: Acrylic acid; Methacrylic acid; Metal salts or ammonium salts thereof
- C08J 3/075: Macromolecular gels
- C08J 3/12: Powdering or granulating
- C08J 3/245: {Differential crosslinking of one polymer with one crosslinking type, e.g. surface crosslinking}
- C08K 3/011: Crosslinking or vulcanising agents, e.g. accelerators
- C08K 3/30: Sulfur-, selenium- or tellurium-containing compounds
- C08K 5/5317: Phosphonic compounds, e.g. R—P(:O)(OR')2
- B01J 2220/68: Superabsorbents
- C08J 2333/02: Homopolymers or copolymers of acids; Metal or ammonium salts thereof
- C08K 2003/3081: {Aluminum sulfate}
- C08F: MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- A61L: METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES (preservation of bodies or disinfecting characterised by the agents employed A01N; preserving, e.g. sterilising, food or foodstuffs A23; preparations for medical, dental or toiletry purposes A61K)
- B01J: CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- C08J: WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H (working, e.g. shaping, of plastics B29)
- C08K: Use of inorganic or non-macromolecular organic substances as compounding ingredients (paints, inks, varnishes, dyes, polishes, adhesives C09)

## Abstract

A process for producing superabsorbents, comprising polymerization of a monomer solution and thermal surface postcrosslinking, wherein the monomer solution comprises at least 0.75% by weight of a hydroxyphosphonic acid or salts thereof, calculated on the basis of the total amount of monomer used, and at least 0.09% by weight of aluminum cations, calculated on the basis of the total amount of polymer particles used, is added to the polymer particles before, during or after the thermal surface postcrosslinking.

## Claims

### Claim 1

Superabsorbent particles having a centrifuge retention capacity of at least 25 g/g, an absorption under a pressure of 49.2 g/cm2 of at least 15 g/g, a gel bed permeability of at least 60 darcies, and the superabsorbent particles, after storage at a temperature of 70° C. and a relative humidity of 80% for 14 days, have an L value of at least 67, an a value of less than 7.0 and a b value of less than 14.5, wherein the particles are prepared by polymerizing a monomer solution or suspension comprising
a) at least one ethylenically unsaturated monomer which bears an acid group and optionally is at least partly neutralized,
b) at least one crosslinker,
c) at least one initiator,
d) optionally one or more ethylenically unsaturated monomer copolymerizable with the monomer a) and
e) optionally one or more water-soluble polymer, comprising
i) polymerizing the monomer solution to give a polymer gel,
ii) optionally comminuting the resulting polymer gel,
iii) drying the polymer gel,
iv) grinding and classifying the dried polymer gel to give polymer particles,
v) thermally surface postcrosslinking the classified polymer particles,
vi) optionally reclassifying the surface postcrosslinked polymer particles,
vii) optionally recycling polymer particles removed in step iv) upstream of step iii) and
viii) optionally recycling polymer particles removed in step vi) upstream of step iii),
which comprises adding to the monomer solution prior to step i) at least 0.75% by weight of a hydroxyphosphonic acid or salts thereof, calculated on the basis of the total amount of monomer a) used, and adding to the polymer particles between step iv) and step vi) at least 0.09% by weight of aluminum cations, calculated on the basis of the total amount of polymer particles used.

### Claim 2 (depends on 1)

Superabsorbent particles according to claim 1, wherein the centrifuge retention capacity is at least 28 g/g.

### Claim 3 (depends on 1)

Superabsorbent particles according to claim 1, wherein the absorption under a pressure of 49.2 g/cm2 is at least 18 g/g.

### Claim 4 (depends on 1)

Superabsorbent particles according to claim 1, wherein the gel bed permeability is at least 75 darcies.

### Claim 5 (depends on 1)

Superabsorbent particles according to claim 1, wherein the superabsorbent particles after storage at a temperature of 70° C. and a relative humidity of 80% for 14 days, have an L value of at least 70.

### Claim 6 (depends on 1)

Superabsorbent particles according to claim 1, wherein the superabsorbent particles after storage at a temperature of 70° C. and a relative humidity of 80% for 14 days, have an a value of less than 5.8 and a b value of less than 13.0.

### Claim 7 (depends on 2)

Superabsorbent particles according to claim 2, wherein the absorption under a pressure of 49.2 g/cm2 is at least 18 g/g.

### Claim 8 (depends on 7)

Superabsorbent particles according to claim 7, wherein the gel bed permeability is at least 75 darcies.

### Claim 9 (depends on 8)

Superabsorbent particles according to claim 8, wherein the superabsorbent particles after storage at a temperature of 70° C. and a relative humidity of 80% for 14 days, have an L value of at least 70.

### Claim 10 (depends on 9)

Superabsorbent particles according to claim 9, wherein the superabsorbent particles after storage at a temperature of 70° C. and a relative humidity of 80% for 14 days, have an a value of less than 5.8 and a b value of less than 13.0.

### Claim 11 (depends on 1)

Superabsorbent particles according to claim 1, wherein the polymer particles removed in step vi) and recycled upstream of step iii) have a particle size of less than 150 μm.

### Claim 12 (depends on 1)

Superabsorbent particles according to claim 1, wherein the hydroxyphosphonic acid is 1-hydroxyethylidene-1,1′-diphosphonic acid.

### Claim 13 (depends on 1)

Superabsorbent particles according to claim 1, wherein the aluminum cations are added prior to step v).

### Claim 14 (depends on 1)

Superabsorbent particles according to claim 1, wherein the aluminum cation is used in the form of aluminum sulfate.

### Claim 15 (depends on 1)

Superabsorbent particles according to claim 1, wherein at least 0.8% by weight of a hydroxyphosphonic acid or salts thereof, calculated on the basis of the total amount of monomer a) used, is added to the monomer solution prior to step i).

### Claim 16 (depends on 1)

Superabsorbent particles according to claim 1, wherein at least 0.85% by weight of a hydroxyphosphonic acid or salts thereof, calculated on the basis of the total amount of monomer a) used, is added to the monomer solution prior to step i).

### Claim 17 (depends on 1)

Superabsorbent particles according to claim 1, wherein at least 0.1% by weight of aluminum cations, calculated on the basis of the total amount of polymer particles used, is added to the polymer particles after step iv).