WO2024115160A1 - Procédé de production de particules superabsorbantes de couleur stable - Google Patents

Procédé de production de particules superabsorbantes de couleur stable Download PDF

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WO2024115160A1
WO2024115160A1 PCT/EP2023/082340 EP2023082340W WO2024115160A1 WO 2024115160 A1 WO2024115160 A1 WO 2024115160A1 EP 2023082340 W EP2023082340 W EP 2023082340W WO 2024115160 A1 WO2024115160 A1 WO 2024115160A1
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Prior art keywords
alkyl
arylalkyl
general formula
compound
pyrazole
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PCT/EP2023/082340
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German (de)
English (en)
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Christian HILS
Christophe Bauduin
Jan Niclas GORGES
Matthias Weismantel
Ruediger Funk
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Basf Se
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Publication of WO2024115160A1 publication Critical patent/WO2024115160A1/fr

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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J3/00—Processes of treating or compounding macromolecular substances
    • C08J3/24—Crosslinking, e.g. vulcanising, of macromolecules
    • C08J3/245—Differential crosslinking of one polymer with one crosslinking type, e.g. surface crosslinking
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/22—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising organic material
    • B01J20/26—Synthetic macromolecular compounds
    • B01J20/265—Synthetic macromolecular compounds modified or post-treated polymers
    • B01J20/267—Cross-linked polymers
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J3/00—Processes of treating or compounding macromolecular substances
    • C08J3/02—Making solutions, dispersions, lattices or gels by other methods than by solution, emulsion or suspension polymerisation techniques
    • C08J3/03—Making solutions, dispersions, lattices or gels by other methods than by solution, emulsion or suspension polymerisation techniques in aqueous media
    • C08J3/075—Macromolecular gels
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J3/00—Processes of treating or compounding macromolecular substances
    • C08J3/12—Powdering or granulating
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • 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
    • A61L15/00—Chemical aspects of, or use of materials for, bandages, dressings or absorbent pads
    • A61L15/16—Bandages, dressings or absorbent pads for physiological fluids such as urine or blood, e.g. sanitary towels, tampons
    • A61L15/42—Use of materials characterised by their function or physical properties
    • A61L15/60—Liquid-swellable gel-forming materials, e.g. super-absorbents
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2333/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Derivatives of such polymers
    • C08J2333/02—Homopolymers or copolymers of acids; Metal or ammonium salts thereof
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K5/00—Use of organic ingredients
    • C08K5/16—Nitrogen-containing compounds
    • C08K5/34—Heterocyclic compounds having nitrogen in the ring
    • C08K5/3442—Heterocyclic compounds having nitrogen in the ring having two nitrogen atoms in the ring
    • C08K5/3445—Five-membered rings

Definitions

  • the present invention relates to a process for producing color-stable superabsorbent particles, wherein an aqueous monomer solution or suspension is polymerized to form a polymer gel, the polymer gel obtained is optionally comminuted, the polymer gel is then dried, the dried polymer gel is optionally ground and classified, the dried polymer gel is then thermally surface-crosslinked and cooled, characterized in that after polymerization it is coated with a pyrazole.
  • Superabsorbents are used to produce diapers, tampons, sanitary napkins and other hygiene articles, but also as water-retaining agents in agricultural horticulture.
  • the superabsorbents are also referred to as water-absorbing polymers.
  • the production of superabsorbents is described in the monograph "Modern Superabsorbent Polymer Technology", FL Buchholz and AT Graham, Wiley-VCH, 1998, pages 71 to 103.
  • GBP gel bed permeability
  • AUL0.7psi absorption under a pressure of 49.2 g/cm2
  • superabsorbent particles are generally surface-crosslinked. This increases the degree of crosslinking of the particle surface, which means that the absorption under a pressure of 49.2 g/cm2 (AUL0.7psi) and the centrifuge retention capacity (CRC) can be at least partially decoupled.
  • This surface-crosslinking can be carried out in an aqueous gel phase.
  • dried, ground and sieved polymer particles base polymer
  • a surface-crosslinker for this purpose are compounds that can form covalent bonds with at least two carboxylate groups of the polymer particles.
  • WO 2021/105038 A1 and the older PCT application with the file number PCT/EP2022/059572 disclose pyrazoles as polymerization inhibitors.
  • the object of the present invention was to provide an improved process for producing color-stable superabsorbent particles.
  • the object was achieved by a process for producing surface-postcrosslinked superabsorbent particles by polymerizing an aqueous monomer solution or suspension containing 221049 2 a) at least one ethylenically unsaturated, acid group-bearing monomer which is at least partially neutralized, b) at least one crosslinker and c) at least one initiator, wherein the aqueous monomer solution or suspension is polymerized to form a polymer gel, the polymer gel obtained is optionally comminuted, the polymer gel is then dried, the dried polymer gel is optionally ground and classified, the dried polymer gel is then thermally surface-postcrosslinked and cooled, characterized in that the polymer particles obtained are coated with at least one pyrazole before, during or after the thermal surface-postcrosslinking.
  • the pyrazole is usually a monomeric pyrazole.
  • the pyrazole used in the process according to the invention is preferably a compound of the general formula (I) where R 1 is C 1 or C 2 alkyl, R 2 is H, C 1 to C 20 alkyl or C 6 to C 20 arylalkyl and R 3 is H, C 1 to C 20 alkyl or C 6 to C 20 arylalkyl, or a compound of the general formula (II) 221049 3 where R 4 is C 1 or C 2 alkyl, R 5 is H, C 1 to C 20 alkyl or C 6 to C 20 arylalkyl and R 6 is H, C 1 to C 20 alkyl or C 6 to C 20 arylalkyl, or a compound of the general formula (III) where R 7 is C 1 or C 2 alkyl, R 8 is H, C 1 to C 20 alkyl or C 6 to C 20 arylalkyl and R 9 is H, C 1 to C 20 alkyl or
  • the alkyl groups can be straight, branched and/or cyclic.
  • the pyrazole used in the process according to the invention is particularly preferably a compound of the general formula (I) 221049 4 where R 1 is C 1 alkyl, R 2 is C 1 to C 3 alkyl or C 6 to C 8 arylalkyl and R 3 is H, C 1 to C 3 alkyl or C 6 to C 8 arylalkyl, or a compound of the general formula (II) where R 4 is C 1 alkyl, R 5 is C 1 to C 3 alkyl or C 6 to C 8 arylalkyl and R 6 is C 1 to C 3 alkyl or C 6 to C 8 arylalkyl, or a compound of the general formula (III) 221049 5 where R 7 is C 1 alkyl, R 8 is H, C 1 to C 3 alkyl or C 6 to C 8 arylalkyl and R 9 is C 1 to C 3 alkyl or C 6 to C 8 arylal
  • the alkyl groups can be straight, branched and/or cyclic.
  • the compounds of the general formula (I) are in equilibrium with their keto form.
  • 1,3-dimethyl-5-pyrazolone is the keto form of 1,3-dimethyl-5-hydroxypyrazole.
  • the pyrazole used in the process according to the invention is very particularly preferably 1,3-dimethyl-5-pyrazolone, 1,5-dimethyl-3-ethyl-4-hydroxypyrazole or 1,5-dimethyl-4-hydroxy-3-phenylpyrazole.
  • the polymer particles are coated with preferably 0.001 to 1% by weight, particularly preferably 0.005 to 0.2% by weight, very particularly preferably 0.01 to 0.1% by weight of the pyrazole, in each case based on the polymer particles.
  • the present invention is based on the finding that pyrazoles significantly improve the color stability of superabsorbents.
  • Acrylic acid is the preferred ethylenically unsaturated carboxylic acid.
  • Peroxodisulfate particularly ammonium peroxodisulfate, sodium peroxodisulfate and/or potassium peroxodisulfate, is the preferred initiator c).
  • the superabsorbents are produced by polymerizing a monomer solution and are usually insoluble in water.
  • the ethylenically unsaturated, acid group-bearing monomers a) are preferably water-soluble, ie the solubility in water at 23°C is typically at least 1 g/100 g. 221049 6 Water, preferably at least 5 g/100 g water, particularly preferably at least 25 g/100 g water, very particularly preferably at least 35 g/100 g water.
  • Suitable monomers are, for example, ethylenically unsaturated carboxylic acids, such as acrylic acid, methacrylic acid and itaconic acid.
  • Particularly preferred monomers are acrylic acid and methacrylic acid. Acrylic acid is very particularly preferred.
  • the ethylenically unsaturated, acid group-bearing monomers a) are usually partially neutralized. The neutralization is carried out at the monomer stage. This is usually done by mixing in the neutralizing agent as an aqueous solution or preferably also as a solid.
  • the degree of neutralization is preferably from 40 to 85 mol%, particularly preferably from 50 to 80 mol%, very particularly preferably from 60 to 75 mol%, it being possible to use the usual neutralizing agents, preferably alkali metal hydroxides, alkali metal oxides, alkali metal carbonates or alkali metal hydrogen carbonates and mixtures thereof.
  • Ammonium salts can also be used instead of alkali metal salts.
  • Sodium and potassium are particularly preferred as alkali metals, but sodium hydroxide, sodium carbonate or sodium hydrogen carbonate and mixtures thereof, especially sodium hydroxide, are very particularly preferred.
  • the monomers usually contain polymerization inhibitors, preferably hydroquinone half ethers, as storage stabilizers.
  • Suitable crosslinkers b) are compounds with at least two groups suitable for crosslinking. Such groups are, for example, ethylenically unsaturated groups that can be radically polymerized into the polymer chain and functional groups that can form covalent bonds with the acid groups of the monomer.
  • polyvalent metal salts that can form coordinate bonds with at least two acid groups of the monomer are also suitable as crosslinking agents.
  • Suitable crosslinkers b) are, for example, ethylene glycol dimethacrylate, diethylene glycol diacrylate, polyethylene glycol diacrylate, allyl methacrylate, trimethylolpropane triacrylate, triallylamine, tetraallylammonium chloride, tetraallyloxyethane, as described in EP 0530438 A1, di- and triacrylates, as described in EP 0547847 A1, EP 0559476 A1, EP 0632068 A1, WO 93/21237 A1, WO 03/104299 A1, WO 03/104300 A1, WO 03/104301 A1 and DE 10331450 A1, mixed acrylates which, in addition to acrylate groups, contain further ethylenically unsaturated groups, as described in DE 10331456 A1 and DE 10355401 A1, or crosslinker mixtures, 221049 7 as described for example in DE 19543368 A1, DE 19646484 A1, WO 90/15830 A1 and WO
  • the amount of crosslinker b) is preferably 0.05 to 1.5 wt. %, particularly preferably 0.1 to 1 wt. %, very particularly preferably 0.15 to 0.6 wt. %, in each case calculated on the total amount of monomer used.
  • the centrifuge retention capacity (CRC) decreases and the absorption under a pressure of 21.0 g/cm2 (AUL0.3 psi) passes through a maximum.
  • All compounds which generate radicals under the polymerization conditions can be used as initiators c), for example thermal initiators, redox initiators, photoinitiators.
  • Suitable redox initiators are sodium peroxodisulfate/ascorbic acid, hydrogen peroxide/ascorbic acid, sodium peroxodisulfate/sodium bisulfite and hydrogen peroxide/sodium bisulfite.
  • mixtures of thermal initiators and redox initiators are used, such as sodium peroxodisulfate/hydrogen peroxide/ascorbic acid.
  • the disodium salt of 2-hydroxy-2-sulfonatoacetic acid or a mixture of the sodium salt of 2-hydroxy-2-sulfinatoacetic acid, the disodium salt of 2-hydroxy-2-sulfonatoacetic acid and sodium bisulfite is preferably used as the reducing component.
  • the water content of the monomer solution is preferably from 40 to 75% by weight, particularly preferably from 45 to 70% by weight, very particularly preferably from 50 to 65% by weight. As the water content increases, the energy required for the subsequent drying increases, and as the water content decreases, the heat of polymerization can only be dissipated insufficiently.
  • the temperature of the monomer solution is preferably from 10 to 90°C, particularly preferably from 20 to 70°C, very particularly preferably from 30 to 50°C.
  • the preferred polymerization inhibitors require dissolved oxygen for optimal effect.
  • the monomer solution can therefore be freed of dissolved oxygen before polymerization by inerting, ie by flowing an inert gas, preferably nitrogen or carbon dioxide, through it.
  • an inert gas preferably nitrogen or carbon dioxide
  • the oxygen content of the monomer solution before polymerization is reduced to less than 1 ppm by weight, more preferably to less than 0.5 ppm by weight, most preferably to less than 0.1 ppm by weight. 221049 8
  • Suitable reactors for polymerization are, for example, kneading reactors or belt reactors.
  • the polymer gel formed during the polymerization of an aqueous monomer solution or suspension is continuously comminuted by, for example, counter-rotating agitator shafts, as described in WO 2001/038402 A1.
  • Polymerization on the belt is described, for example, in DE 3825366 A1 and US 6,241,928.
  • Polymerization in a belt reactor produces a polymer gel that must be comminuted, for example in an extruder or kneader.
  • the comminuted polymer gel obtained by means of a kneader can also be extruded.
  • the polymer gel is then usually dried using a circulating air belt dryer until the residual moisture content is preferably 0.5 to 10% by weight, particularly preferably 1 to 7% by weight, very particularly preferably 2 to 5% by weight, the residual moisture content being determined according to test method no. WSP 230.2-05 "Mass Loss Upon Heating" recommended by EDANA. If the residual moisture is too high, the dried polymer gel has a glass transition temperature T g that is too low and is difficult to process further. If the residual moisture is too low, the dried polymer gel is too brittle and undesirably large amounts of polymer particles with too small a particle size ("fines") are produced in the subsequent comminution steps.
  • the solids content of the polymer gel before drying is preferably between 25 and 90% by weight, particularly preferably between 35 and 70% by weight, very particularly preferably between 40 and 60% by weight.
  • the dried polymer gel is then broken and optionally coarsely crushed.
  • the dried polymer gel is then usually ground and classified, whereby single or multi-stage roller mills, preferably two or three-stage roller mills, pin mills, hammer mills or vibrating mills can usually be used for grinding.
  • the average particle size of the polymer particles separated as a product fraction is preferably from 150 to 850 ⁇ m, particularly preferably from 250 to 600 ⁇ m, very particularly from 300 to 500 ⁇ m.
  • the average particle size of the product fraction can be determined using the test method No.
  • WSP 220.2 (05) "Particle Size Distribution” recommended by EDANA, whereby the mass fractions of the sieve fractions are plotted cumulatively and the average particle size is determined graphically.
  • the average particle size is the value of the mesh size that results for a cumulative 50 wt.%. 221049 9
  • the polymer particles are thermally surface-crosslinked to further improve their properties. Suitable surface-crosslinkers are compounds that contain groups that can form covalent bonds with at least two carboxylate groups of the polymer particles.
  • Suitable compounds are, for example, polyfunctional amines, polyfunctional amidoamines, polyfunctional epoxides, as described in EP 0083022 A2, EP 0543303 A1 and EP 0937736 A2, di- or polyfunctional alcohols, as described in DE 3314019 A1, DE 35 23617 A1 and EP 0450922 A2, or ß-hydroxyalkylamides, as described in DE 10204938 A1 and US 6,239,230.
  • the amount of surface post-crosslinker is preferably 0.001 to 2% by weight, particularly preferably 0.01 to 1% by weight, very particularly preferably 0.03 to 0.7% by weight, based in each case on the polymer particles.
  • polyvalent cations are applied to the particle surface in addition to the surface post-crosslinkers.
  • the polyvalent cations that can be used in the process according to the invention are, for example, divalent cations, such as the cations of zinc, magnesium, calcium and strontium, trivalent cations, such as the cations of aluminum, iron, chromium, rare earths and manganese, tetravalent cations, such as the cations of titanium and zirconium.
  • Chloride, bromide, hydroxide, sulfate, hydrogen sulfate, carbonate, hydrogen carbonate, nitrate, phosphate, hydrogen phosphate, dihydrogen phosphate and carboxylate, such as acetate and lactate, are possible as counterions.
  • Aluminum hydroxide, aluminum sulfate and aluminum lactate are preferred.
  • the amount of polyvalent cation used is, for example, 0.001 to 1.5% by weight, preferably 0.005 to 1% by weight, particularly preferably 0.02 to 0.8% by weight, based in each case on the polymer.
  • the surface post-crosslinking is usually carried out by spraying a solution of the surface post-crosslinker onto the dried polymer particles.
  • the polymer particles coated with surface post-crosslinker are thermally treated.
  • the spraying of a solution of the surface post-crosslinker is preferably carried out in mixers with moving mixing tools, such as screw mixers, disk mixers and paddle mixers.
  • Horizontal mixers, such as paddle mixers, are particularly preferred, and vertical mixers are very particularly preferred.
  • the distinction between horizontal mixers and Vertical mixers are based on the bearing of the mixing shaft, i.e. horizontal mixers have a horizontally mounted mixing shaft and vertical mixers have a vertically mounted mixing shaft. Suitable mixers are, for example, horizontal Pflugschar® mixers (Gebr.
  • Suitable dryers include Hosokawa Bepex® Horizontal Paddle Dryer (Hosokawa Micron GmbH; Leingart; Germany), Hosokawa Bepex® Disc Dryer (Hosokawa Micron GmbH; Leingart; Germany), Holo-Flite® dryers (Metso Minerals Industries Inc.; Danville; USA) and Nara Paddle Dryer (NARA Machinery Europe; Frechen; Germany). Fluidized bed dryers can also be used. Surface post-crosslinking can take place in the mixer itself by heating the jacket or blowing in warm air. A downstream dryer, such as a tray dryer, a rotary kiln or a heatable screw, is also suitable. Mixing and thermal surface post-crosslinking are particularly advantageous in a fluidized bed dryer.
  • Preferred reaction temperatures are in the range 100 to 250°C, preferably 110 to 220°C, particularly preferably 120 to 210°C, very particularly preferably 130 to 200°C.
  • the preferred residence time at this temperature is preferably at least 10 minutes, particularly preferably at least 20 minutes, very particularly preferably at least 30 minutes, and usually at most 60 minutes.
  • the surface-crosslinked polymer particles can then be classified again, with polymer particles that are too small and/or too large being separated off and returned to the process.
  • the surface-crosslinked polymer particles can be coated or remoistened to further improve their properties. 11
  • the remoistening is preferably carried out at 30 to 80°C, particularly preferably at 35 to 70°C, very particularly preferably at 40 to 60°C.
  • the amount of water used for remoistening is preferably from 1 to 10% by weight, particularly preferably from 2 to 8% by weight, very particularly preferably from 3 to 5% by weight.
  • the remoistening increases the mechanical stability of the polymer particles and reduces their tendency to become statically charged.
  • the remoistening is advantageously carried out in the cooler after the thermal surface post-crosslinking.
  • Suitable coatings for improving the swelling rate and the gel bed permeability (GBP) are, for example, inorganic inert substances such as water-insoluble metal salts, organic polymers, cationic polymers and divalent or polyvalent metal cations.
  • Suitable coatings for binding dust are, for example, polyols.
  • Suitable coatings against the undesirable tendency of the polymer particles to cake are, for example, pyrogenic silica, such as Aerosil® 200, precipitated silica, such as Sipernat® D17, and surfactants, such as Span® 20.
  • the present invention also relates to superabsorbent particles coated with at least one pyrazole.
  • the pyrazole is usually a monomeric pyrazole.
  • the pyrazole is preferably a compound of the general formula (I) where R 1 is C 1 or C 2 alkyl, R 2 is H, C 1 to C 20 alkyl or C 6 to C 20 arylalkyl and R 3 is H, C 1 to C 20 alkyl or C 6 to C 20 arylalkyl, 221049 12 or a compound of general formula (II) where R 4 is C 1 or C 2 alkyl, R 5 is H, C 1 to C 20 alkyl or C 6 to C 20 arylalkyl and R 6 is H, C 1 to C 20 alkyl or C 6 to C 20 arylalkyl, or a compound of the general formula (III) where R 7 is C 1 or C 2 alkyl, R 8 is H, C 1 to C 20 alkyl or C 6 to C 20 arylalkyl and R 9 is H, C 1 to C 20 alkyl or C 6 to C 20 arylalkyl.
  • R 1 is C 1 or C 2 alkyl
  • the pyrazole is particularly preferably a compound of the general formula (I) 221049 13 where R 1 is C 1 alkyl, R 2 is C 1 to C 3 alkyl or C 6 to C 8 arylalkyl and R 3 is H, C 1 to C 3 alkyl or C 6 to C 8 arylalkyl, or a compound of the general formula (II) where R 4 is C 1 alkyl, R 5 is C 1 to C 3 alkyl or C 6 to C 8 arylalkyl and R 6 is C 1 to C 3 alkyl or C 6 to C 8 arylalkyl, or a compound of the general formula (III) 221049 14 where R 7 is C 1 alkyl, R 8 is C 1 to C 3 alkyl or C 6 to C 8 arylalkyl and R 9 is H, C 1 to C 3 alkyl or C 6 to C 8 arylalkyl.
  • the alkyl groups can be straight, branched and/or cyclic.
  • the compounds of the general formula (I) are in equilibrium with their keto form.
  • 1,3-dimethyl-5-pyrazolone is the keto form of 1,3-dimethyl-5-hydroxypyrazole.
  • the pyrazole is very particularly preferably 1,3-dimethyl-5-pyrazolone, 1,5-dimethyl-3-ethyl-4-hydroxypyrazole or 1,5-dimethyl-4-hydroxy-3-phenylpyrazole.
  • the superabsorbent particles were coated with preferably 0.001 to 1% by weight, particularly preferably 0.005 to 0.2% by weight, very particularly preferably 0.01 to 0.1% by weight of the pyrazole, based in each case on the polymer particles.
  • Acrylic acid is the preferred ethylenically unsaturated carboxylic acid.
  • Peroxodisulfate particularly ammonium peroxodisulfate, sodium peroxodisulfate and/or potassium peroxodisulfate, is the preferred initiator c).
  • the present invention further relates to hygiene articles containing superabsorbent particles according to the invention. Methods: Unless otherwise stated, the measurements should be carried out at an ambient temperature of 23 ⁇ 2°C and a relative humidity of 50 ⁇ 10%. The superabsorbent particles are mixed well before the measurement.
  • the Hunter 60 value is a measure of the whiteness of surfaces and is defined as L-3b, i.e. the lower the value, the darker and yellower the color.
  • the test was carried out using a tissue culture dish (diameter of 35 mm and height of 10 mm) and a port plate opening of 0.5 inch. The color value is measured in accordance with the tristimulus method according to DIN 5033-6.
  • Yellowness Index YI
  • the Yellowness Index (YI) is measured according to ASTM D1925 or according to ASTM E313. The higher the value, the darker and yellower the color.
  • Example 1 A monomer solution was prepared by continuously mixing deionized water, 50 wt.% sodium hydroxide solution and acrylic acid so that the degree of neutralization was 74.0 mol%. The water content of the monomer solution was 59.0 wt.%. Triple ethoxylated glycerol triacrylate (approx. 85% by weight) was used as crosslinker. The amount used was 1.34 kg per t of monomer solution. 221049 16 To initiate the radical polymerization, 2.14 kg of a 0.25 wt. % aqueous hydrogen peroxide solution, 2.91 kg of a 15 wt. % aqueous sodium peroxodisulfate solution and 1.97 kg of a 1 wt.
  • % aqueous ascorbic acid solution were used per t of monomer solution.
  • the monomer solution was dosed into a List Contikneter reactor with a volume of 6.3 m3 (LIST AG, Arisdorf, Switzerland). The throughput of the monomer solution was approximately 20 t/h.
  • the reaction solution had a temperature of 23.5°C at the inlet.
  • the monomer solution was rendered inert with nitrogen between the addition point for the crosslinker and the addition points for the hydrogen peroxide and sodium peroxodisulfate solutions.
  • Ascorbic acid was dosed directly into the reactor.
  • the residence time of the reaction mixture in the reactor was about 15 minutes.
  • the polymer gel obtained was fed onto the conveyor belt of a circulating air belt dryer using an oscillating conveyor belt.
  • the circulating air belt dryer was 48 m long.
  • the conveyor belt of the circulating air belt dryer had an effective width of 4.4 m.
  • the aqueous polymer gel was continuously blown around with an air/gas mixture (about 175°C) and dried.
  • the residence time in the circulating air belt dryer was 37 minutes.
  • the dried polymer gel was crushed using a three-stage roller mill and sieved to a particle size of 150 to 700 ⁇ m. Polymer particles with a particle size of less than 150 ⁇ m were separated. Polymer particles with a particle size of greater than 700 ⁇ m were returned to the shredding process. Polymer particles with a particle size in the range of 150 to 700 ⁇ m were thermally surface-crosslinked.
  • the polymer particles were coated with a surface-crosslinking solution in a Schugi Flexomix® (Hosokawa Micron BV, Doetinchem, Netherlands) and then dried in a NARA Paddle Dryer (GMF Gouda, Waddinxveen, Netherlands) for 45 minutes at 175°C.
  • the surface crosslinker solution contained 1.35 wt.% ethylene glycol diglycidyl ether, 44.84 wt.% 1,2-propanediol and 53.81 wt.% water. After drying, the surface crosslinked polymer particles were cooled to approx. 60°C in a NARA paddle cooler (GMF Gouda, Waddinxveen, Netherlands).
  • the surface-crosslinked polymer particles were coated with 7.5 kg/h of a 50 wt.% aqueous polyethylene glycol solution (polyethylene glycol with an average molecular weight of 400 g/mol), 375 kg/h of water, 22.5 kg/h of aluminum trihydroxide ("aluminum hydroxide dry gel", article number 511066100, Dr. Paul Lohmann GmbH KG, Haupt No 2, 31860 Emmerthal, Germany) and 18.75 kg/h of a 1 wt.% aqueous solution of sorbitan monolaurate.
  • Example 2 20 g of superabsorbent from Example 1 were mixed with 200 ppm by weight of a pyrazole and stored for 14 days in a climate cabinet at 70°C and 80% relative humidity.

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  • Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)

Abstract

La présente invention concerne un procédé de production de particules superabsorbantes de couleur stable, selon lequel une solution aqueuse de monomère ou une suspension de monomère est polymérisée pour former un gel polymère, le gel polymère obtenu est éventuellement broyé, le gel polymère est ensuite séché, le gel polymère séché est éventuellement broyé et classifié, le gel polymère séché est par la suite réticulé thermiquement en surface et refroidi, le revêtement étant caractérisé en ce qu'il est réalisé avec un pyrazole après polymérisation.
PCT/EP2023/082340 2022-11-29 2023-11-20 Procédé de production de particules superabsorbantes de couleur stable WO2024115160A1 (fr)

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DE3314019A1 (de) 1982-04-19 1984-01-12 Nippon Shokubai Kagaku Kogyo Co. Ltd., Osaka Absorbierender gegenstand
DE3523617A1 (de) 1984-07-02 1986-01-23 Nippon Shokubai Kagaku Kogyo Co. Ltd., Osaka Wasserabsorbierendes mittel
DE3825366A1 (de) 1987-07-28 1989-02-09 Dai Ichi Kogyo Seiyaku Co Ltd Verfahren zur kontinuierlichen herstellung eines acrylpolymergels
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EP0450922A2 (fr) 1990-04-02 1991-10-09 Nippon Shokubai Kagaku Kogyo Co. Ltd. Procédé de préparation d'un agrégat stable à la fluidité
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WO2001038402A1 (fr) 1999-11-20 2001-05-31 Basf Aktiengesellschaft Procede de preparation continue de polymerisats geliformes reticules a fines particules
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WO2003104299A1 (fr) 2002-06-11 2003-12-18 Basf Aktiengesellschaft Procede de production d'esters de polyalcools
WO2003104301A1 (fr) 2002-06-11 2003-12-18 Basf Aktiengesellschaft (meth)acrylesters de glycerine polyalcoxy
DE10331450A1 (de) 2003-07-10 2005-01-27 Basf Ag (Meth)acrylsäureester monoalkoxilierter Polyole und deren Herstellung
DE10331456A1 (de) 2003-07-10 2005-02-24 Basf Ag (Meth)acrylsäureester alkoxilierter ungesättigter Polyolether und deren Herstellung
DE10355401A1 (de) 2003-11-25 2005-06-30 Basf Ag (Meth)acrylsäureester ungesättigter Aminoalkohole und deren Herstellung
WO2011157656A2 (fr) * 2010-06-14 2011-12-22 Basf Se Particules polymères hydroabsorbantes présentant une stabilité de couleur améliorée
US20130260988A1 (en) * 2012-03-30 2013-10-03 Basf Se Color-Stable Superabsorbent
WO2019011793A1 (fr) * 2017-07-12 2019-01-17 Basf Se Procédé de production de particules polymères superabsorbantes
EP3828159A1 (fr) * 2019-11-28 2021-06-02 Basf Se Stabilisateurs de stockage et de transport pour composés polymérisables
WO2021105038A1 (fr) 2019-11-28 2021-06-03 Basf Se Stabilisateurs de conservation et de transport pour composés polymérisables
WO2022223336A1 (fr) * 2021-04-20 2022-10-27 Basf Se Inhibiteurs de polymérisation

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