EP1838463B1 - Method for grading a particulate water-absorbing resin - Google Patents

Method for grading a particulate water-absorbing resin Download PDF

Info

Publication number
EP1838463B1
EP1838463B1 EP05821876A EP05821876A EP1838463B1 EP 1838463 B1 EP1838463 B1 EP 1838463B1 EP 05821876 A EP05821876 A EP 05821876A EP 05821876 A EP05821876 A EP 05821876A EP 1838463 B1 EP1838463 B1 EP 1838463B1
Authority
EP
European Patent Office
Prior art keywords
process according
sieving apparatus
temperature
pressure
gas stream
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Active
Application number
EP05821876A
Other languages
German (de)
French (fr)
Other versions
EP1838463A1 (en
EP1838463B2 (en
Inventor
Matthias Weismantel
Rüdiger Funk
Thomas Daniel
Uwe Stueven
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
BASF SE
Original Assignee
BASF SE
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Family has litigation
First worldwide family litigation filed litigation Critical https://patents.darts-ip.com/?family=36011074&utm_source=***_patent&utm_medium=platform_link&utm_campaign=public_patent_search&patent=EP1838463(B1) "Global patent litigation dataset” by Darts-ip is licensed under a Creative Commons Attribution 4.0 International License.
Application filed by BASF SE filed Critical BASF SE
Publication of EP1838463A1 publication Critical patent/EP1838463A1/en
Application granted granted Critical
Publication of EP1838463B1 publication Critical patent/EP1838463B1/en
Publication of EP1838463B2 publication Critical patent/EP1838463B2/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B07—SEPARATING SOLIDS FROM SOLIDS; SORTING
    • B07B—SEPARATING SOLIDS FROM SOLIDS BY SIEVING, SCREENING, SIFTING OR BY USING GAS CURRENTS; SEPARATING BY OTHER DRY METHODS APPLICABLE TO BULK MATERIAL, e.g. LOOSE ARTICLES FIT TO BE HANDLED LIKE BULK MATERIAL
    • B07B1/00—Sieving, screening, sifting, or sorting solid materials using networks, gratings, grids, or the like
    • B07B1/46—Constructional details of screens in general; Cleaning or heating of screens
    • B07B1/56—Heated screens
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B07—SEPARATING SOLIDS FROM SOLIDS; SORTING
    • B07B—SEPARATING SOLIDS FROM SOLIDS BY SIEVING, SCREENING, SIFTING OR BY USING GAS CURRENTS; SEPARATING BY OTHER DRY METHODS APPLICABLE TO BULK MATERIAL, e.g. LOOSE ARTICLES FIT TO BE HANDLED LIKE BULK MATERIAL
    • B07B1/00—Sieving, screening, sifting, or sorting solid materials using networks, gratings, grids, or the like
    • B07B1/28—Moving screens not otherwise provided for, e.g. swinging, reciprocating, rocking, tilting or wobbling screens
    • B07B1/40—Resonant vibration screens
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B07—SEPARATING SOLIDS FROM SOLIDS; SORTING
    • B07B—SEPARATING SOLIDS FROM SOLIDS BY SIEVING, SCREENING, SIFTING OR BY USING GAS CURRENTS; SEPARATING BY OTHER DRY METHODS APPLICABLE TO BULK MATERIAL, e.g. LOOSE ARTICLES FIT TO BE HANDLED LIKE BULK MATERIAL
    • B07B1/00—Sieving, screening, sifting, or sorting solid materials using networks, gratings, grids, or the like
    • B07B1/46—Constructional details of screens in general; Cleaning or heating of screens

Definitions

  • the present invention relates to a method for classifying a particulate water-absorbent resin by means of a sieving apparatus at a pressure reduced from the ambient pressure and a sieve apparatus for classifying a particulate water-absorbent resin at a pressure reduced from the ambient pressure.
  • Water-absorbent resins typically have a centrifuge retention capacity of 15 to 60 g / g, preferably at least 20 g / g, preferably at least 25 g / g, more preferably at least 30 g / g, most preferably at least 35 g / g.
  • Centrifuge retention capacity is determined according to the EDANA (European Disposables and Nonwovens Association) recommended test method no. 441.2-02 "Centrifuge retention capacity".
  • the preparation of water-absorbing resins usually comprises the steps of polymerization, drying, comminution, classification, postcrosslinking and, if appropriate, renewed classification.
  • the object of the present invention was to find a simplified method for the classification of water-absorbing resins, which allows high screening performance and long equipment runtimes.
  • this object is achieved by classifying water-absorbing resins at reduced pressure relative to the ambient pressure, preferably at a pressure of at most 950 mbar, preferably at a pressure of at most 900 mbar, more preferably at a pressure of at most 800 mbar, most preferably at a pressure of at most 700 mbar, the resin being dissolved during classifying with a gas is flowed over, and wherein the gas stream before the screening device has a temperature of at least 40 ° C.
  • the pressure is usually at least 10 mbar, preferably at least 50 mbar, preferably at least 100 mbar, more preferably at least 200 mbar, most preferably at least 300 mbar.
  • Another aspect of the present invention is the screening device for carrying out the classification method according to the invention.
  • the screening devices which are suitable for the classification method according to the invention are not subject to any restrictions; plane sieve methods are preferred, tumble screening machines are very particularly preferred.
  • the screening device is typically shaken to aid classification. This is preferably done so that the material to be classified is spirally guided over the sieve.
  • This forced vibration typically has an amplitude of 0.7 to 40 mm, preferably 1.5 to 25 mm, and a frequency of 1 to 100 Hz, preferably of 5 to 10 Hz.
  • the water-absorbent resin is overflowed during the classifying with a gas stream, particularly preferably air.
  • the amount of gas is typically from 0.1 to 10 m 3 / h per m 2 screen area, preferably from 0.5 to 5 m 3 / h per m 2 screen area, particularly preferably from 1 to 3 m 3 / h per m 2 screen area, the gas volume being measured under standard conditions (25 ° C and 1 bar).
  • the gas stream is before entering the screening device to a temperature of at least 40 ° C, preferably to a temperature of at least 50 ° C, preferably to a temperature of at least 60 ° C, more preferably to a temperature of at least 65 ° C, all more preferably at a temperature of at least 70 ° C.
  • the temperature of the gas stream is usually less than 120 ° C, preferably less than 110 ° C, preferably less than 100 ° C, more preferably less than 90 ° C, most preferably less than 80 ° C.
  • the water content of the gas stream is typically not more than 5 g / kg, preferably not more than 4.5 g / kg, preferably not more than 4 g / kg, more preferably not more than 3.5 g / kg, most preferably not more than 3 g / kg.
  • a gas stream with a low water content can be generated, for example, by condensing a corresponding amount of water from the gas stream having a higher water content by cooling.
  • the screening device can still be heated and / or thermally insulated, such as in EP-A-0 855 232 described.
  • the screening device is operated at a temperature of 40 to 80 ° C.
  • Suitable monomers i) are, for example, ethylenically unsaturated carboxylic acids, such as acrylic acid, methacrylic acid, maleic acid, fumaric acid and itaconic acid, or derivatives thereof, such as acrylamide, methacrylamide, acrylic esters and methacrylic acid esters. Particularly preferred monomers are acrylic acid and methacrylic acid. Very particular preference is given to acrylic acid.
  • Preferred hydroquinone half ethers are hydroquinone monomethyl ether (MEHQ) and / or tocopherols.
  • Tocopherol is understood as meaning compounds of the following formula wherein R 1 is hydrogen or methyl, R 2 is hydrogen or methyl, R 3 is hydrogen or methyl and R 4 is hydrogen or an acid radical having 1 to 20 carbon atoms.
  • Preferred radicals for R 4 are acetyl, ascorbyl, succinyl, nicotinyl and other physiologically acceptable carboxylic acids.
  • the carboxylic acids may be mono-, di- or tricarboxylic acids.
  • R 4 is particularly preferably hydrogen or acetyl. Especially preferred is RRR-alpha-tocopherol.
  • the monomer solution preferably contains at most 130 ppm by weight, more preferably at most 70 ppm by weight, preferably at least 10 ppm by weight, more preferably at least 30 ppm by weight, particularly preferably around 50 ppm by weight, hydroquinone hemether, in each case on acrylic acid, wherein acrylic acid salts are mathematically taken into account as acrylic acid.
  • an acrylic acid having a corresponding content of hydroquinone half-ether may be used to prepare the monomer solution.
  • the water-absorbing polymers are crosslinked, ie the polymerization is carried out in the presence of compounds having at least two polymerisable groups which can be radically copolymerized into the polymer network.
  • Suitable crosslinkers ii) are, for example, ethylene glycol dimethacrylate, diethylene glycol diacrylate, allyl methacrylate, trimethylolpropane triacrylate, triallylamine, tetraallyloxyethane, as in EP-A-0 530 438 described, di- and triacrylates, as in EP-A-0 547 847 . EP-A-0 559 476 . EP-A-0 632 068 . WO-A-93/21237 .
  • WO-A-03/104299 WO-A-03/104300 .
  • WO-A-03/104301 and in the German patent application with the file number 10331450.4 described, mixed acrylates containing in addition to acrylate groups further ethylenically unsaturated groups, as in the German patent applications with the file reference 10331456.3 and 10355401.7 or crosslinker mixtures, such as in DE-A-195 43 368 .
  • DE-A-196 46 484 WO 90/15830 and WO-A-02/32962 described.
  • Suitable crosslinkers ii) are, in particular, N, N'-methylenebisacrylamide and N, N'-methylenebismethacrylamide, esters of unsaturated monocarboxylic or polycarboxylic acids of polyols, such as diacrylate or triacrylate, for example butanediol or ethylene glycol diacrylate or methacrylate, and trimethylolpropane triacrylate and allyl compounds, such as allyl (meth) acrylate, triallyl cyanurate, maleic acid diallyl esters, polyallyl esters, tetraallyloxyethane, triallylamine, tetraallylethylenediamine, allyl esters of phosphoric acid and vinylphosphonic acid derivatives, as described, for example, in US Pat EP-A-0 343 427 are described.
  • crosslinkers ii) are pentaerythritol di-, pentaerythritol tri- and pentaerythritol tetraallyl ethers, polyethylene glycol diallyl ether, ethylene glycol diallyl ether, glycerol and glycerol triallyl ethers, polyallyl ethers based on sorbitol, and ethoxylated variants thereof.
  • Useful in the process according to the invention are di (meth) acrylates of polyethylene glycols, wherein the polyethylene glycol used has a molecular weight between 300 and 1000.
  • crosslinkers ii) are di- and triacrylates of 3 to 20 times ethoxylated glycerol, of 3 to 20 times ethoxylated trimethylolpropane, of 3 to 20-times ethoxylated trimethylolethane, in particular di- and triacrylates of 2- to 6-times ethoxylated glycerol or trimethylolpropane, 3-fold propoxylated glycerol or trimethylolpropane, and the 3-fold mixed ethoxylated or propoxylated glycerol or trimethylolpropane, the 15-fold ethoxylated Glycerol or trimethylolpropane, as well as at least 40-times ethoxylated glycerol, trimethylolethane or trimethylolpropane.
  • Very particularly preferred crosslinkers ii) are the polyethoxylated and / or propoxylated glycerols esterified with acrylic acid or methacrylic acid to form di- or triacrylates, as described, for example, in the earlier German application with file reference DE 10319462.2 are described.
  • Particularly advantageous are di- and / or triacrylates of 3- to 10-fold ethoxylated glycerol.
  • Most preferred are the triacrylates of 3 to 5 times ethoxylated and / or propoxylated glycerin.
  • acrylamide, methacrylamide, crotonic acid amide, dimethylaminoethyl methacrylate, dimethylaminoethyl acrylate, dimethylaminopropyl acrylate, diethylaminopropyl acrylate, dimethylaminobutyl acrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, dimethylaminoneopentyl acrylate, and dimethylaminoneopentyl methacrylate are exemplified by ethylenically unsaturated monomers iii) copolymerizable with monomers i).
  • water-soluble polymers iv) it is possible to use polyvinyl alcohol, polyvinylpyrrolidone, starch, starch derivatives, polyglycols or polyacrylic acids, preferably polyvinyl alcohol and starch.
  • the reaction is preferably carried out in a kneader, such as in WO-A-01/38402 described, or on a belt reactor, such as in EP-A-0 955 086 described, performed.
  • the acid groups of the resulting hydrogels are usually partially neutralized, preferably from 25 to 95 mol%, preferably from 27 to 80 mol%, particularly preferably from 27 to 30 mol% or from 40 to 75 mol%
  • the customary neutralizing agents can be used, preferably alkali metal hydroxides, alkali metal oxides, alkali metal carbonates or alkali metal hydrogencarbonates and mixtures thereof.
  • alkali metal salts and ammonium salts can be used.
  • Sodium and potassium are particularly preferred as alkali metals, but most preferred are sodium hydroxide, sodium carbonate or sodium bicarbonate and mixtures thereof.
  • the neutralization is achieved by mixing the neutralizing agent as an aqueous solution, as a melt, or preferably as a solid.
  • sodium hydroxide with a water content well below 50 wt .-% may be present as a waxy mass with a melting point above 23 ° C. In this case, a dosage as general cargo or melt at elevated temperature is possible.
  • the neutralization can be carried out after the polymerization at the hydrogel stage. However, it is also possible to neutralize up to 40 mol%, preferably 10 to 30 mol%, particularly preferably 15 to 25 mol%, of the acid groups before the polymerization by adding a part of the neutralizing agent already to the monomer solution and the desired final degree of neutralization only after the polymerization is adjusted at the level of the hydrogel.
  • the monomer solution can be neutralized by mixing in the neutralizing agent.
  • the hydrogel can be mechanically comminuted, for example by means of a meat grinder, wherein the neutralizing agent can be sprayed, sprinkled or poured over and then thoroughly mixed. For this purpose, the gel mass obtained can be further gewolfft for homogenization. Neutralization of the monomer solution directly to the final degree of neutralization is preferred.
  • the neutralized hydrogel is then dried with a belt or drum dryer until the residual moisture content is preferably below 15 wt .-%, in particular below 10 wt .-%, wherein the water content according to the recommended by the EDANA (European Disposables and Nonwovens Association) Test Method no 430.2-02 "Moisture content" is determined.
  • a fluidized bed dryer or a heated ploughshare mixer can be used for drying.
  • it is advantageous in the drying of this gel to ensure rapid removal of the evaporating water.
  • the dryer temperature must be optimized, the air supply and removal must be controlled, and it is in any case to ensure adequate ventilation.
  • the drying is naturally simpler and the product is the whiter, if the solids content of the gel is as high as possible.
  • the solids content of the gel before drying is therefore preferably between 30 and 80% by weight.
  • Particularly advantageous is the ventilation of the dryer with nitrogen or other non-oxidizing inert gas.
  • Advantageous in terms of color and product quality is usually the shortest possible drying time.
  • drying of the gel Another important function of the drying of the gel is the here still occurring reduction of the residual monomer content in the superabsorber. During drying, possibly remaining residues of the initiators decompose and lead to a copolymerization of residual monomers remaining. In addition, the vaporizing amounts of water still tear free free steam-volatile monomers, such as acrylic acid with, and thus also reduce the residual monomer content in the superabsorbent.
  • the dried hydrogel is thereafter ground and classified, wherein for grinding usually one- or multi-stage roller mills, preferably two- or three-stage roller mills, pin mills, hammer mills or vibratory mills can be used.
  • water-absorbent polymer particles are generally postcrosslinked. This postcrosslinking can be carried out in aqueous gel phase.
  • ground and sieved polymer particles base polymer
  • crosslinkers suitable for this purpose are compounds which contain at least two groups which can form covalent bonds with the carboxylate groups of the hydrophilic polymer or which can crosslink at least two carboxyl groups or other functional groups of at least two different polymer chains of the base polymer.
  • Suitable postcrosslinkers v) are compounds which contain at least two groups which can form covalent bonds with the carboxylate groups of the polymers.
  • Suitable compounds are, for example, alkoxysilyl compounds, polyaziridines, polyamines, polyamidoamines, di- or polyglycidyl compounds, as in EP-A-0 083 022 .
  • EP-A-543,303 and EP-A-937 736 described polyhydric alcohols, as in DE-C-33 14 019 .
  • mixed functionality such as glycidol, 3-ethyl-3-oxetanemethanol (trimethylolpropane oxetane), as in EP-A-1 199 327 described, aminoethanol, diethanolamine, triethanolamine or compounds which form a further functionality after the first reaction, such as ethylene oxide, propylene oxide, isobutylene oxide, aziridine, azetidine or oxetane.
  • the post-crosslinking is usually carried out so that a solution of the postcrosslinker is sprayed onto the hydrogel or the dry base polymer particles. Subsequent to the spraying, it is thermally dried, whereby the postcrosslinking reaction can take place both before and during the drying.
  • the spraying of a solution of the crosslinker is preferably carried out in mixers with agitated mixing tools, such as screw mixers, paddle mixers, disk mixers, plowshare mixers and paddle mixers.
  • agitated mixing tools such as screw mixers, paddle mixers, disk mixers, plowshare mixers and paddle mixers.
  • Vertical mixers are particularly preferred, plowshare mixers and paddle mixers are very particularly preferred.
  • Suitable mixers are, for example, Lödige® mixers, Bepex® mixers, Nauta® mixers, Processall® mixers and Schugi® mixers.
  • the thermal drying is preferably carried out in contact dryers, more preferably paddle dryers, very particularly preferably disk dryers.
  • Suitable dryers include Bepex® dryers and, Nara® dryers.
  • fluidized bed dryers can also be used.
  • the drying can take place in the mixer itself, by heating the jacket or blowing hot air. Also suitable is a downstream dryer, such as a hopper dryer, a rotary kiln or a heatable screw. However, it is also possible, for example, to use an azeotropic distillation as the drying process.
  • Preferred drying temperatures are in the range 50 to 250 ° C, preferably at 50 to 200 ° C, and particularly preferably at 50 to 150 ° C.
  • the preferred residence time at this temperature in the reaction mixer or dryer is less than 30 minutes, more preferably less than 10 minutes.
  • the classification method according to the invention is preferably carried out after the drying of the base polymer, before the post-crosslinking and / or after the post-crosslinking.
  • the water content of the water-absorbing resin after drying of the base polymer or before the post-crosslinking is typically from 2 to 10% by weight. and after postcrosslinking, typically below 1% by weight, preferably below 0.1% by weight.
  • Thermal insulation is an additional layer of material on the screen which reduces the heat loss of the screen to the outside.
  • the temperature of the heating mantle was adjusted to the reaction temperature in the reactor by means of control.
  • the crumbly gel finally obtained was then dried at 160 ° C for 3 hours in a convection oven. It was then ground and sieved to 250 to 850 microns.
  • the water content was 2.7% by weight.
  • the ground base polymer was added to the sieve at the indicated temperature.
  • the sieve could be operated at reduced pressure.
  • the screen was covered with preheated air with defined water vapor content. The amount of air was 2 m 3 / h per m 2 screen area.

Abstract

Process for classifying a particulate water-absorbing resin using a sieving apparatus at a reduced pressure compared with the ambient pressure and a sieving apparatus for classifying a particulate water-absorbing resin at a reduced pressure compared with the ambient pressure.

Description

Die vorliegende Erfindung betrifft ein Verfahren zum Klassieren eines teilchenförmigen wasserabsorbierenden Harzes mittels einer Siebvorrichtung bei einem gegenüber dem Umgebungsdruck vermindertem Druck sowie eine Siebvorrichtung zum Klassieren eines teilchenförmigen wasserabsorbierenden Harzes bei einem gegenüber dem Umgebungsdruck vermindertem Druck.The present invention relates to a method for classifying a particulate water-absorbent resin by means of a sieving apparatus at a pressure reduced from the ambient pressure and a sieve apparatus for classifying a particulate water-absorbent resin at a pressure reduced from the ambient pressure.

Die Herstellung wasserabsorbierender Harze ist vielfach beschrieben, siehe beispielsweise " Modern Superabsorbent Polymer Technology", F.L. Buchholz and A.T. Graham, Wiley-VCH, 1998, Seiten .69 bis 117 .The preparation of water-absorbent resins has been described many times, see for example " Modern Superabsorbent Polymer Technology ", FL Buchholz and AT Graham, Wiley-VCH, 1998, pp. 69-177 ,

Wasserabsorbierende Harze haben typischerweise eine Zentrifugenretentionskapazität von 15 bis 60 g/g, vorzugsweise von mindestens 20 g/g, bevorzugt von mindestens 25 g/g, besonders bevorzugt von mindestens 30 g/g, ganz besonders bevorzugt von mindestens 35 g/g. Die Zentrifugenretentionskapazität (CRC) wird gemäß der von der EDANA (European Disposables and Nonwovens Association) empfohlenen Testmethode Nr. 441.2-02 "Centrifuge retention capacity" bestimmt.Water-absorbent resins typically have a centrifuge retention capacity of 15 to 60 g / g, preferably at least 20 g / g, preferably at least 25 g / g, more preferably at least 30 g / g, most preferably at least 35 g / g. Centrifuge retention capacity (CRC) is determined according to the EDANA (European Disposables and Nonwovens Association) recommended test method no. 441.2-02 "Centrifuge retention capacity".

Die Herstellung wasserabsorbierender Harze umfasst üblicherweise die Schritte Polymerisation, Trocknung, Zerkleinerung, Klassierung, Nachvernetzung und ggf. erneute Klassierung.The preparation of water-absorbing resins usually comprises the steps of polymerization, drying, comminution, classification, postcrosslinking and, if appropriate, renewed classification.

Ein allgemeine Übersicht zur Klassierung ist beispielsweise in Ullmanns Encyklopädie der technischen Chemie, 4. Auflage, Band 2, Seiten 43 bis 56, Verlag Chemie, Weinheim, 1972 , zu finden.A general overview of the classification is, for example, in Ullmann's Encyclopedia of Industrial Chemistry, 4th Edition, Volume 2, pages 43 to 56, Verlag Chemie, Weinheim, 1972 , to find.

Speziell bei der Klassierung wasserabsorbierender Harze besteht aber das Problem, dass sich die Siebleistung durch Agglomeration vermindert. So lehrt EP-A-0 855 232 , dass die verwendeten Siebe im erwärmten Zustand gehalten oder thermisch isoliert werden müssen.Especially in the classification of water-absorbing resins, however, there is the problem that the screening performance is reduced by agglomeration. So teaches EP-A-0 855 232 in that the sieves used must be kept in the heated state or thermally insulated.

US 2003/87983 lehrt, dass beim Sieben bei erhöhter Temperatur der Metallabrieb und damit der Verschleiß an der Siebvorrichtung stark zunimmt. US 2003/87983 teaches that when sieving at elevated temperature of the metal abrasion and thus the wear on the screening device greatly increases.

Die Aufgabe der vorliegenden Erfindung war ein vereinfachtes Verfahren zur Klassierung von wasserabsobierenden Harzen zu finden, dass hohe Siebleistungen und lange Apparatelaufzeiten ermöglicht.The object of the present invention was to find a simplified method for the classification of water-absorbing resins, which allows high screening performance and long equipment runtimes.

Es wurde nun gefunden, dass diese Aufgabe durch Klassieren von wasserabsorbierenden Harzen bei gegenüber dem Umgebungsdruck vermindertem Druck, vorzugsweise bei einem Druck von höchstens 950 mbar, bevorzugt bei einem Druck von höchstens 900 mbar, besonders bevorzugt bei einem Druck von höchstens 800 mbar, ganz besonders bevorzugt bei einem Druck von höchstens 700 mbar, gelöst wird, wobei das Harz während des Klassierens mit einem Gas überströmt wird, und wobei der Gasstrom vor der Siebvorrichtung eine Temperatur von mindestens 40°C aufweist. Üblicherweise beträgt der Druck mindestens 10 mbar, vorzugsweise mindestens 50 mbar, bevorzugt mindestens 100 mbar, besonders bevorzugt mindestens 200 mbar, ganz besonders bevorzugt mindestens 300 mbar. Ein weiterer Aspekt der vorliegenden Erfindung ist die Siebvorrichtung zur Durchführung des erfindungsgemäßen Klassierverfahren.It has now been found that this object is achieved by classifying water-absorbing resins at reduced pressure relative to the ambient pressure, preferably at a pressure of at most 950 mbar, preferably at a pressure of at most 900 mbar, more preferably at a pressure of at most 800 mbar, most preferably at a pressure of at most 700 mbar, the resin being dissolved during classifying with a gas is flowed over, and wherein the gas stream before the screening device has a temperature of at least 40 ° C. The pressure is usually at least 10 mbar, preferably at least 50 mbar, preferably at least 100 mbar, more preferably at least 200 mbar, most preferably at least 300 mbar. Another aspect of the present invention is the screening device for carrying out the classification method according to the invention.

Die für das erfindungsgemäße Klassierverfahren geeigneten Siebvorrichtungen unterliegen keiner Beschränkung, bevorzugt sind Plansiebverfahren, ganz besonders bevorzugt sind Taumelsiebmaschinen. Die Siebvorrichtung wird zur Unterstützung der Klassierung typischerweise gerüttelt. Dies geschieht vorzugsweise so, dass das zu klassierende Gut spiralförmig über das Sieb geführt wird. Diese erzwungene Vibration hat typischerweise eine Amplitude von 0,7 bis 40 mm, vorzugsweise von 1,5 bis 25 mm, und eine Frequenz von 1 bis 100 Hz, vorzugsweise von 5 bis 10 Hz.The screening devices which are suitable for the classification method according to the invention are not subject to any restrictions; plane sieve methods are preferred, tumble screening machines are very particularly preferred. The screening device is typically shaken to aid classification. This is preferably done so that the material to be classified is spirally guided over the sieve. This forced vibration typically has an amplitude of 0.7 to 40 mm, preferably 1.5 to 25 mm, and a frequency of 1 to 100 Hz, preferably of 5 to 10 Hz.

Das wasserabsorbierende Harz wird während des Klassierens mit einem Gasstrom, besonders bevorzugt Luft, überströmt. Die Gasmenge beträgt typischerweise von 0,1 bis 10 m3/h pro m2 Siebfläche, vorzugsweise von 0,5 bis 5 m3/h pro m2 Siebfläche, besonders bevorzugt von 1 bis 3 m3/h pro m2 Siebfläche, wobei das Gasvolumen unter Standardbedingungen gemessen wird (25°C und 1 bar). Der Gasstrom wird vor dem Eintritt in die Siebvorrichtung auf eine Temperatur von mindestens 40°C, vorzugsweise auf eine Temperatur von mindestens 50°C, bevorzugt auf eine Temperatur von mindestens 60°C, besonders bevorzugt auf eine Temperatur von mindestens 65°C, ganz besonders bevorzugt auf eine Temperatur von mindestens 70°C. angewärmt. Die Temperatur des Gasstroms beträgt üblicherweise weniger als 120°C, vorzugsweise weniger als 110°C, bevorzugt weniger als 100°C, besonders bevorzugt weniger als 90°C, ganz besonders bevorzugt weniger als 80°C. Der Wassergehalt des Gasstroms beträgt typischerweise nicht mehr als 5 g/kg, vorzugsweise nicht mehr als 4,5 g/kg, bevorzugt nicht mehr als 4 g/kg, besonders bevorzugt nicht mehr 3,5 g/kg, ganz besonders bevorzugt nicht mehr als 3 g/kg. Ein Gasstrom mit geringem Wassergehalt kann beispielsweise erzeugt werden, indem aus einem Gasstrom mit höherem Wassergehalt eine entsprechende Wassermenge durch Abkühlung auskondensiert wird.The water-absorbent resin is overflowed during the classifying with a gas stream, particularly preferably air. The amount of gas is typically from 0.1 to 10 m 3 / h per m 2 screen area, preferably from 0.5 to 5 m 3 / h per m 2 screen area, particularly preferably from 1 to 3 m 3 / h per m 2 screen area, the gas volume being measured under standard conditions (25 ° C and 1 bar). The gas stream is before entering the screening device to a temperature of at least 40 ° C, preferably to a temperature of at least 50 ° C, preferably to a temperature of at least 60 ° C, more preferably to a temperature of at least 65 ° C, all more preferably at a temperature of at least 70 ° C. warmed up. The temperature of the gas stream is usually less than 120 ° C, preferably less than 110 ° C, preferably less than 100 ° C, more preferably less than 90 ° C, most preferably less than 80 ° C. The water content of the gas stream is typically not more than 5 g / kg, preferably not more than 4.5 g / kg, preferably not more than 4 g / kg, more preferably not more than 3.5 g / kg, most preferably not more than 3 g / kg. A gas stream with a low water content can be generated, for example, by condensing a corresponding amount of water from the gas stream having a higher water content by cooling.

Zusätzlich kann die Siebvorrichtung noch erwärmt und/oder thermisch isoliert werden, wie beispielsweise in EP-A-0 855 232 beschrieben. Typischerweise wird die Siebvorrichtung bei einer Temperatur von 40 bis 80°C betrieben.In addition, the screening device can still be heated and / or thermally insulated, such as in EP-A-0 855 232 described. Typically, the screening device is operated at a temperature of 40 to 80 ° C.

Die im erfindungsgemäßen Verfahren einsetzbaren wasserabsorbierenden Harze können durch Polymerisation einer Monomerlösung, enthaltend

  • i) mindestens ein ethylenisch ungesättigtes, säuregruppentragendes Monomer,
  • ii) mindestens eines Vernetzer,
  • iii) gegebenenfalls ein oder mehrere mit i) copolymerisierbare ethylenisch und/oder allylisch ungesättigte Monomere und
  • iv) gegebenenfalls ein oder mehrere wasserlösliche Polymere, auf die die Monomere i), ii) und ggf. iii) zumindest teilweise aufgepfropft werden können,
    wobei das dabei erhaltene Grundpolymer getrocknet, klassiert,
  • v) gegebenenfalls mit mindestens einem Nachvernetzer nachbehandelt, getrocknet und thermisch nachvernetzt
wird, hergestellt werden.The water-absorbing resins which can be used in the process according to the invention can be obtained by polymerization of a monomer solution comprising
  • i) at least one ethylenically unsaturated, acid group-carrying monomer,
  • ii) at least one crosslinker,
  • iii) optionally one or more ethylenically and / or allylically unsaturated monomers copolymerizable with i) and
  • iv) optionally one or more water-soluble polymers to which the monomers i), ii) and optionally iii) can be at least partially grafted,
    wherein the base polymer thereby obtained dried, classified,
  • v) optionally post-treated with at least one postcrosslinker, dried and thermally postcrosslinked
will be produced.

Geeignete Monomere i) sind beispielsweise ethylenisch ungesättigte Carbonsäuren, wie Acrylsäure, Methacrylsäure, Maleinsäure, Fumarsäure und Itaconsäure, oder deren Derivate, wie Acrylamid, Methacrylamid, Acrylsäureester und Methacrylsäureester. Besonders bevorzugte Monomere sind Acrylsäure und Methacrylsäure. Ganz besonders bevorzugt ist Acrylsäure.Suitable monomers i) are, for example, ethylenically unsaturated carboxylic acids, such as acrylic acid, methacrylic acid, maleic acid, fumaric acid and itaconic acid, or derivatives thereof, such as acrylamide, methacrylamide, acrylic esters and methacrylic acid esters. Particularly preferred monomers are acrylic acid and methacrylic acid. Very particular preference is given to acrylic acid.

Die Monomere i), insbesondere Acrylsäure, enthalten vorzugsweise bis zu 0,025 Gew.-% eines Hydrochinonhalbethers. Bevorzugte Hydrochinonhalbether sind Hydrochinonmonomethylether (MEHQ) und/oder Tocopherole.The monomers i), in particular acrylic acid, preferably contain up to 0.025 wt .-% of a Hydrochinonhalbethers. Preferred hydroquinone half ethers are hydroquinone monomethyl ether (MEHQ) and / or tocopherols.

Unter Tocopherol werden Verbindungen der folgenden Formel verstanden

Figure imgb0001
wobei R1 Wasserstoff oder Methyl, R2 Wasserstoff oder Methyl, R3 Wasserstoff oder Methyl und R4 Wasserstoff oder ein Säurerest mit 1 bis 20 Kohlenstoffatomen bedeutet.Tocopherol is understood as meaning compounds of the following formula
Figure imgb0001
 wherein R 1 is hydrogen or methyl, R 2 is hydrogen or methyl, R 3 is hydrogen or methyl and R 4 is hydrogen or an acid radical having 1 to 20 carbon atoms.

Bevorzugte Reste für R4 sind Acetyl, Ascorbyl, Succinyl, Nicotinyl und andere physiologisch verträgliche Carbonsäuren. Die Carbonsäuren können Mono-, Di- oder Tricarbonsäuren sein.Preferred radicals for R 4 are acetyl, ascorbyl, succinyl, nicotinyl and other physiologically acceptable carboxylic acids. The carboxylic acids may be mono-, di- or tricarboxylic acids.

Bevorzugt ist alpha-Tocopherol mit R1 = R2 = R3 = Methyl, insbesondere racemisches alpha-Tocopherol. R4 ist besonders bevorzugt Wasserstoff oder Acetyl. Insbesondere bevorzugt ist RRR-alpha-Tocopherol.Preference is given to alpha-tocopherol with R 1 = R 2 = R 3 = methyl, in particular racemic alpha-tocopherol. R 4 is particularly preferably hydrogen or acetyl. Especially preferred is RRR-alpha-tocopherol.

Die Monomerlösung enthält bevorzugt höchstens 130 Gew.-ppm, besonders bevorzugt höchstens 70 Gew.-ppm, bevorzugt mindestens 10 Gew.-ppm, besonders bevorzugt mindestens 30 Gew.-ppm, insbesondere bevorzugt um 50 Gew.-ppm, Hydrochinonhalbether, jeweils bezogen auf Acrylsäure, wobei Acrylsäuresalze rechnerisch als Acrylsäure mit berücksichtigt werden. Beispielsweise kann zur Herstellung der Monomerlösung eine Acrylsäure mit einem entsprechenen Gehalt an Hydrochinonhalbether verwendet werden.The monomer solution preferably contains at most 130 ppm by weight, more preferably at most 70 ppm by weight, preferably at least 10 ppm by weight, more preferably at least 30 ppm by weight, particularly preferably around 50 ppm by weight, hydroquinone hemether, in each case on acrylic acid, wherein acrylic acid salts are mathematically taken into account as acrylic acid. For example, an acrylic acid having a corresponding content of hydroquinone half-ether may be used to prepare the monomer solution.

Die wasserabsorbierenden Polymere sind vernetzt, d.h. die Polymerisation wird in Gegenwart von Verbindungen mit mindestens zwei polymerisierbaren Gruppen, die in das Polymernetzwerk radikalisch einpolymerisiert werden können, durchgeführt. Geeignete Vernetzer ii) sind beispielsweise Ethylenglykoldimethacrylat, Diethylenglykoldiacrylat, Allylmethacrylat, Trimethylolpropantriacrylat, Triallylamin, Tetraallyloxyethan, wie in EP-A-0 530 438 beschrieben, Di- und Triacrylate, wie in EP-A-0 547 847 , EP-A-0 559 476 , EP-A-0 632 068 , WO-A-93/21237 , WO-A-03/104299 , WO-A-03/104300 , WO-A-03/104301 und in der deutschen Patentanmeldung mit dem Aktenzeichen 10331450.4 beschrieben, gemischte Acrylate, die neben Acrylatgruppen weitere ethylenisch ungesättigte Gruppen enthalten, wie in den deutschen Patentanmeldungen mit den Aktenzeichen 10331456.3 und 10355401.7 beschrieben, oder Vernetzermischungen, wie beispielsweise in DE-A-195 43 368 , DE-A-196 46 484 , WO-A-90/15830 und WO-A-02/32962 beschrieben.The water-absorbing polymers are crosslinked, ie the polymerization is carried out in the presence of compounds having at least two polymerisable groups which can be radically copolymerized into the polymer network. Suitable crosslinkers ii) are, for example, ethylene glycol dimethacrylate, diethylene glycol diacrylate, allyl methacrylate, trimethylolpropane triacrylate, triallylamine, tetraallyloxyethane, as in EP-A-0 530 438 described, di- and triacrylates, as in EP-A-0 547 847 . EP-A-0 559 476 . EP-A-0 632 068 . WO-A-93/21237 . WO-A-03/104299 . WO-A-03/104300 . WO-A-03/104301 and in the German patent application with the file number 10331450.4 described, mixed acrylates containing in addition to acrylate groups further ethylenically unsaturated groups, as in the German patent applications with the file reference 10331456.3 and 10355401.7 or crosslinker mixtures, such as in DE-A-195 43 368 . DE-A-196 46 484 . WO 90/15830 and WO-A-02/32962 described.

Geeignete Vernetzer ii) sind insbesondere N,N'-Methylenbisacrylamid und N,N'-Methylenbismethacrylamid, Ester ungesättigter Mono- oder Polycarbonsäuren von Polyolen, wie Diacrylat oder Triacrylat, beispielsweise Butandiol- oder Ethylenglykoldiacrylat bzw. -methacrylat sowie Trimethylolpropantriacrylat und Allylverbindungen, wie Allyl(meth)acrylat, Triallylcyanurat, Maleinsäurediallylester, Polyallylester, Tetraallyloxyethan, Triallylamin, Tetraallylethylendiamin, Allylester der Phosphorsäure sowie Vinylphosphonsäurederivate, wie sie beispielsweise in EP-A-0 343 427 beschrieben sind. Weiterhin geeignete Vernetzer ii) sind Pentaerythritoldi-, Pentaerythritoltri- und Pentaerythritoltetraallylether, Polyethylenglykoldiallylether, Ethylenglykoldiallylether, Glyzerindi- und Glyzerintriallylether, Polyallylether auf Basis Sorbitol, sowie ethoxylierte Varianten davon. Im erfindungsgemäßen Verfahren einsetzbar sind Di(meth)acrylate von Polyethylenglykolen, wobei das eingesetzte Polyethylenglykol ein Molekulargewicht zwischen 300 und 1000 aufweist.Suitable crosslinkers ii) are, in particular, N, N'-methylenebisacrylamide and N, N'-methylenebismethacrylamide, esters of unsaturated monocarboxylic or polycarboxylic acids of polyols, such as diacrylate or triacrylate, for example butanediol or ethylene glycol diacrylate or methacrylate, and trimethylolpropane triacrylate and allyl compounds, such as allyl (meth) acrylate, triallyl cyanurate, maleic acid diallyl esters, polyallyl esters, tetraallyloxyethane, triallylamine, tetraallylethylenediamine, allyl esters of phosphoric acid and vinylphosphonic acid derivatives, as described, for example, in US Pat EP-A-0 343 427 are described. Further suitable crosslinkers ii) are pentaerythritol di-, pentaerythritol tri- and pentaerythritol tetraallyl ethers, polyethylene glycol diallyl ether, ethylene glycol diallyl ether, glycerol and glycerol triallyl ethers, polyallyl ethers based on sorbitol, and ethoxylated variants thereof. Useful in the process according to the invention are di (meth) acrylates of polyethylene glycols, wherein the polyethylene glycol used has a molecular weight between 300 and 1000.

Besonders vorteilhafte Vernetzer ii) sind jedoch Di- und Triacrylate des 3- bis 20-fach ethoxylierten Glyzerins, des 3- bis 20-fach ethoxylierten Trimethylolpropans, des 3- bis 20-fach ethoxylierten Trimethylolethans, inbesondere Di- und Triacrylate des 2- bis 6-fach ethoxylierten Glyzerins oder Trimethylolpropans, des 3-fach propoxylierten Glyzerins oder Trimethylolpropans, sowie des 3-fach gemischt ethoxylierten oder propoxylierten Glyzerins oder Trimethylolpropans, des 15-fach ethoxylierten Glyzerins oder Trimethylolpropans, sowie des mindestens 40-fach ethoxylierten Glyzerins, Trimethylolethans oder Trimethylolpropans.However, particularly advantageous crosslinkers ii) are di- and triacrylates of 3 to 20 times ethoxylated glycerol, of 3 to 20 times ethoxylated trimethylolpropane, of 3 to 20-times ethoxylated trimethylolethane, in particular di- and triacrylates of 2- to 6-times ethoxylated glycerol or trimethylolpropane, 3-fold propoxylated glycerol or trimethylolpropane, and the 3-fold mixed ethoxylated or propoxylated glycerol or trimethylolpropane, the 15-fold ethoxylated Glycerol or trimethylolpropane, as well as at least 40-times ethoxylated glycerol, trimethylolethane or trimethylolpropane.

Ganz besonders bevorzugte Vernetzer ii) sind die mit Acrylsäure oder Methacrylsäure zu Di- oder Triacrylaten veresterten mehrfach ethoxylierten und/oder propoxylierten Glyzerine wie sie beispielsweise in der älteren deutschen Anmeldung mit Aktenzeichen DE 10319462.2 beschrieben sind. Besonders vorteilhaft sind Di- und/oder Triacrylate des 3- bis 10-fach ethoxylierten Glyzerins. Ganz besonders bevorzugt sind Di- oder Triacrylate des 1- bis 5- fach ethoxylierten und/oder propoxylierten Glyzerins. Am meisten bevorzugt sind die Triacrylate des 3- bis 5-fach ethoxylierten und/oder propoxylierten Glyzerins. Diese zeichnen sich durch besonders niedrige Restgehalte (typischerweise unter 10 Gew.-ppm) im wasseraborbierenden Polymer aus und die wässrigen Extrakte der damit hergestellten wasserabsorbierenden Polymere weisen eine fast unveränderte Oberflächenspannung (typischerweise mindestens 0,068 N/m) im Vergleich zu Wasser gleicher Temperatur auf.Very particularly preferred crosslinkers ii) are the polyethoxylated and / or propoxylated glycerols esterified with acrylic acid or methacrylic acid to form di- or triacrylates, as described, for example, in the earlier German application with file reference DE 10319462.2 are described. Particularly advantageous are di- and / or triacrylates of 3- to 10-fold ethoxylated glycerol. Very particular preference is given to diacrylates or triacrylates of 1 to 5 times ethoxylated and / or propoxylated glycerol. Most preferred are the triacrylates of 3 to 5 times ethoxylated and / or propoxylated glycerin. These are characterized by particularly low residual contents (typically below 10 ppm by weight) in the water-absorbent polymer and the aqueous extracts of the water-absorbing polymers produced therewith have an almost unchanged surface tension (typically at least 0.068 N / m) compared to water of the same temperature.

Mit den Monomeren i) copolymerisierbare ethylenisch ungesättigte Monomere iii) sind beispielsweise Acrylamid, Methacrylamid, Crotonsäureämid, Dimethylaminoethylmethacrylat, Dimethylaminoethylacrylat, Dimethylaminopropylacrylat, Diethylaminopropylacrylat, Dimethylaminobutylacrylat, Dimethylaminoethylmethaaylat, Diethylaminoethylmethacrylat, Dimethylaminoneopentylacrylat und Dimethylaminoneopentylmethacrylat.For example, acrylamide, methacrylamide, crotonic acid amide, dimethylaminoethyl methacrylate, dimethylaminoethyl acrylate, dimethylaminopropyl acrylate, diethylaminopropyl acrylate, dimethylaminobutyl acrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, dimethylaminoneopentyl acrylate, and dimethylaminoneopentyl methacrylate are exemplified by ethylenically unsaturated monomers iii) copolymerizable with monomers i).

Als wasserlösliche Polymere iv) können Polyvinylalkohol, Polyvinylpyrrolidon, Stärke, Stärkederivate, Polyglykole oder Polyacrylsäuren, vorzugsweise Polyvinylalkohol und Stärke, eingesetzt werden.As water-soluble polymers iv) it is possible to use polyvinyl alcohol, polyvinylpyrrolidone, starch, starch derivatives, polyglycols or polyacrylic acids, preferably polyvinyl alcohol and starch.

Die Herstellung eines geeigneten Grundpolymers sowie weitere geeignete hydrophile ethylenisch ungesättigte Monomere i) werden in DE-A-199 41 423 , EP-A-0 686 650 , WO-A-01/45758 und WO-A-03/104300 beschrieben.The preparation of a suitable base polymer as well as other suitable hydrophilic ethylenically unsaturated monomers i) are described in DE-A-199 41 423 . EP-A-0 686 650 . WO-A-01/45758 and WO-A-03/104300 described.

Die Umsetzung wird vorzugsweise in einem Kneter, wie beispielsweise in WO-A-01/38402 beschrieben, oder auf einem Bandreaktor, wie beispielsweise in EP-A-0 955 086 beschrieben, durchgeführt.The reaction is preferably carried out in a kneader, such as in WO-A-01/38402 described, or on a belt reactor, such as in EP-A-0 955 086 described, performed.

Die Säuregruppen der erhaltenen Hydrogele sind üblicherweise teilweise neutralisiert, vorzugsweise zu 25 bis 95 mol%, bevorzugt zu 27 bis 80 mol-%, besonders bevorzugt zu 27 bis 30 mol-% oder 40 bis 75 mol-%, wobei die üblichen Neutralisationsmittel verwendet werden können, vorzugsweise Alkalimetallhydroxide, Alkalimetalloxide, Alkalimetallcarbonate oder Alkalimetallhydrogencarbonate sowie deren Mischungen. Statt Alkalimetallsalzen können auch Ammoniumsalze verwendet werden. Natrium und Kalium sind als Alkalimetalle besonders bevorzugt, ganz besonders bevorzugt sind jedoch Natriumhydroxid, Natriumcarbonat oder Natriumhydrogencarbonat sowie deren Mischungen. Üblicherweise wird die Neutralisation durch Einmischung des Neutralisationsmittels als wässrige Lösung, als Schmelze, oder bevorzugt auch als Feststoff erreicht. Beispielsweise kann Natriumhydroxid mit einem Wasseranteil deutlich unter 50 Gew.-% als wachsartige Masse mit einem Schmelzpunkt oberhalb 23°C vorliegen. In diesem Fall ist eine Dosierung als Stückgut oder Schmelze bei erhöhter Temperatur möglich.The acid groups of the resulting hydrogels are usually partially neutralized, preferably from 25 to 95 mol%, preferably from 27 to 80 mol%, particularly preferably from 27 to 30 mol% or from 40 to 75 mol%, the customary neutralizing agents can be used, preferably alkali metal hydroxides, alkali metal oxides, alkali metal carbonates or alkali metal hydrogencarbonates and mixtures thereof. Instead of alkali metal salts and ammonium salts can be used. Sodium and potassium are particularly preferred as alkali metals, but most preferred are sodium hydroxide, sodium carbonate or sodium bicarbonate and mixtures thereof. Usually, the neutralization is achieved by mixing the neutralizing agent as an aqueous solution, as a melt, or preferably as a solid. For example, sodium hydroxide with a water content well below 50 wt .-% may be present as a waxy mass with a melting point above 23 ° C. In this case, a dosage as general cargo or melt at elevated temperature is possible.

Die Neutralisation kann nach der Polymerisation auf der Stufe des Hydrogels durchgeführt werden. Es ist aber auch möglich bis zu 40 mol-%, vorzugsweise 10 bis 30 mol-%, besonders bevorzugt 15 bis 25 mol%, der Säureguppen vor der Polymerisation zu neutralisieren indem ein Teil des Neutralisationsmittels bereits der Monomerlösung zugesetzt und der gewünschte Endneutralisationsgrad erst nach der Polymerisation auf der Stufe des Hydrogels eingestellt wird. Die Monomerlösung kann durch Einmischen des Neutralisationsmittels neutralisiert werden. Das Hydrogel, kann mechanisch zerkleinert werden, beispielsweise mittels eines Fleischwolfes, wobei das Neutralisationsmittel aufgesprüht, übergestreut oder aufgegossen und dann sorgfältig untergemischt werden kann. Dazu kann die erhaltene Gelmasse noch mehrmals zur Homogenisierung gewolft werden. Die Neutralisation der Monomerlösung direkt auf den Endneutralisationsgrad ist bevorzugt.The neutralization can be carried out after the polymerization at the hydrogel stage. However, it is also possible to neutralize up to 40 mol%, preferably 10 to 30 mol%, particularly preferably 15 to 25 mol%, of the acid groups before the polymerization by adding a part of the neutralizing agent already to the monomer solution and the desired final degree of neutralization only after the polymerization is adjusted at the level of the hydrogel. The monomer solution can be neutralized by mixing in the neutralizing agent. The hydrogel can be mechanically comminuted, for example by means of a meat grinder, wherein the neutralizing agent can be sprayed, sprinkled or poured over and then thoroughly mixed. For this purpose, the gel mass obtained can be further gewolfft for homogenization. Neutralization of the monomer solution directly to the final degree of neutralization is preferred.

Das neutralisierte Hydrogel wird dann mit einem Band- oder Walzentrockner getrocknet bis der Restfeuchtegehalt vorzugsweise unter 15 Gew.-%, insbesondere unter 10 Gew.-% liegt, wobei der Wassergehalt gemäß der von der EDANA (European Disposables and Nonwovens Association) empfohlenen Testmethode Nr. 430.2-02 "Moisture content" bestimmt wird. Wahlweise kann zur Trocknung aber auch ein Wirbelbetttrockner oder ein beheizter Pflugscharmischer verwendet werden. Um besonders weiße Produkte zu erhalten, ist es vorteilhaft bei der Trocknung dieses Gels einen schnellen Abtransport des verdampfenden Wassers sicherzustellen. Dazu ist die Trocknertemperatur zu optimieren, die Luftzu- und -abführung muss kontrolliert erfolgen, und es ist in jedem Fall auf ausreichende Belüftung zu achten. Die Trocknung ist naturgemäß umso einfacher und das Produkt umso weißer, wenn der Feststoffgehalt des Gels möglichst hoch ist. Bevorzugt liegt der Feststoffgehalt des Geles vor der Trocknung daher zwischen 30 und 80 Gew.%. Besonders vorteilhaft ist die Belüftung des Trockners mit Stickstoff oder einem anderen nicht-oxidierenden Inertgas. Wahlweise kann aber auch einfach nur der Partialdruck des Sauerstoffs während der Trocknung abgesenkt werden, um oxidative Vergilbungsvorgänge zu verhindern. Im Regelfall führt aber auch eine ausreichende Belüftung und Abführung des Wasserdampfes zu einem noch akzeptablen Produkt. Vorteilhaft hinsichtlich Farbe und Produktqualität ist in der Regel eine möglichst kurze Trocknungszeit.The neutralized hydrogel is then dried with a belt or drum dryer until the residual moisture content is preferably below 15 wt .-%, in particular below 10 wt .-%, wherein the water content according to the recommended by the EDANA (European Disposables and Nonwovens Association) Test Method no 430.2-02 "Moisture content" is determined. Alternatively, a fluidized bed dryer or a heated ploughshare mixer can be used for drying. To obtain particularly white products, it is advantageous in the drying of this gel to ensure rapid removal of the evaporating water. For this purpose, the dryer temperature must be optimized, the air supply and removal must be controlled, and it is in any case to ensure adequate ventilation. The drying is naturally simpler and the product is the whiter, if the solids content of the gel is as high as possible. The solids content of the gel before drying is therefore preferably between 30 and 80% by weight. Particularly advantageous is the ventilation of the dryer with nitrogen or other non-oxidizing inert gas. Optionally, however, it is also possible simply to lower only the partial pressure of the oxygen during the drying in order to prevent oxidative yellowing processes. As a rule, but also leads to a sufficient ventilation and removal of water vapor to a still acceptable product. Advantageous in terms of color and product quality is usually the shortest possible drying time.

Eine weitere wichtige Funktion der Trocknung des Geles ist die hier noch stattfindende Verringerung des Restmonomerengehaltes im Superabsorber. Bei der Trocknung zerfallen nämlich eventuell noch vorhandende Reste der Initiatoren und führen zu einer Einpolymerisation von noch vorhandenen Restmonomeren. Außerdem reißen die verdampfenden Wassermengen noch vorhandene freie wasserdampfflüchtige Monomere, wie beispielsweise Acrylsäure mit, und verringern so ebenfalls den Restmonomerengehalt im Superabsorber.Another important function of the drying of the gel is the here still occurring reduction of the residual monomer content in the superabsorber. During drying, possibly remaining residues of the initiators decompose and lead to a copolymerization of residual monomers remaining. In addition, the vaporizing amounts of water still tear free free steam-volatile monomers, such as acrylic acid with, and thus also reduce the residual monomer content in the superabsorbent.

Das getrocknete Hydrogel wird hiernach gemahlen und klassiert, wobei zur Mahlung üblicherweise ein- oder mehrstufige Walzenstühle, bevorzugt zwei- oder dreistufige Walzenstühle, Stiftmühlen, Hammermühlen oder Schwingmühlen eingesetzt werden können.The dried hydrogel is thereafter ground and classified, wherein for grinding usually one- or multi-stage roller mills, preferably two- or three-stage roller mills, pin mills, hammer mills or vibratory mills can be used.

Zur Verbesserung der Anwendungseigenschaften, wie beispielsweise Flüssigkeitsleitfähigkeit (SFC) in der Windel und Absorption unter Druck (AUL), werden wasserabsorbierende Polymerpartikel im allgemeinen nachvernetzt. Diese Nachvernetzung kann in wässriger Gelphase durchgeführt werden. Vorzugsweise werden aber gemahlene und abgesiebte Polymerpartikel (Grundpolymer) an der Oberfläche mit einem Nachvernetzer beschichtet, getrocknet und thermisch nachvernetzt. Dazu geeignete Vernetzer sind Verbindungen, die mindestens zwei Gruppen enthalten, die mit den Carboxylatgruppen des hydrophilen Polymeren kovalente Bindungen bilden können oder die mindestens zwei Carboxylgruppen oder andere funktionelle Gruppen mindestens zweier verschiedener Polymerketten des Grundpolymers miteinander vernetzen können.To improve application properties, such as diaper fluid conductivity (SFC) and absorption under pressure (AUL), water-absorbent polymer particles are generally postcrosslinked. This postcrosslinking can be carried out in aqueous gel phase. Preferably, however, ground and sieved polymer particles (base polymer) are coated on the surface with a postcrosslinker, dried and thermally postcrosslinked. Crosslinkers suitable for this purpose are compounds which contain at least two groups which can form covalent bonds with the carboxylate groups of the hydrophilic polymer or which can crosslink at least two carboxyl groups or other functional groups of at least two different polymer chains of the base polymer.

Hierzu geeignete Nachvernetzer v) sind Verbindungen, die mindestens zwei Gruppen enthalten, die mit den Carboxylatgruppen der Polymere kovalente Bindungen bilden können. Geeignete Verbindungen sind beispielsweise Alkoxysiliylverbindungen, Polyaziridine, Polyamine, Polyamidoamine, Di- oder Polyglycidylverbindungen, wie in EP-A-0 083 022 , EP-A-543 303 und EP-A-937 736 beschrieben, mehrwertige Alkohole, wie in DE-C-33 14 019 , DE-C-35 23 617 und EP-A-450 922 beschrieben, oder β-Hydroxyalkylamide, wie in DE-A-102 04 938 und US-6,239,230 beschrieben. Geeignet sind ferner Verbindungen mit gemischter Funktionalität, wie Glycidol, 3-Ethyl-3-Oxetanmethanol (Trimethylolpropanoxetan), wie in EP-A-1 199 327 beschrieben, Aminoethanol, Diethanolamin, Triethanolamin oder Verbindungen, die nach der ersten Reaktion eine weitere Funktionalität ausbilden, wie Ethylenoxid, Propylenoxid, Isobutylenoxid, Aziridin, Azetidin oder Oxetan.Suitable postcrosslinkers v) are compounds which contain at least two groups which can form covalent bonds with the carboxylate groups of the polymers. Suitable compounds are, for example, alkoxysilyl compounds, polyaziridines, polyamines, polyamidoamines, di- or polyglycidyl compounds, as in EP-A-0 083 022 . EP-A-543,303 and EP-A-937 736 described, polyhydric alcohols, as in DE-C-33 14 019 . DE-C-35 23 617 and EP-A-450 922 described, or β-hydroxyalkylamides, as in DE-A-102 04 938 and US 6,239,230 described. Also suitable are compounds having mixed functionality, such as glycidol, 3-ethyl-3-oxetanemethanol (trimethylolpropane oxetane), as in EP-A-1 199 327 described, aminoethanol, diethanolamine, triethanolamine or compounds which form a further functionality after the first reaction, such as ethylene oxide, propylene oxide, isobutylene oxide, aziridine, azetidine or oxetane.

Desweiteren sind in DE-A-40 20 780 zyclische Karbonate, in DE-A-198 07 502 2- Oxazolidon und dessen Derivate, wie N-(2-Hydroxyethyl)-2-oxazolidon, in DE-A-198 07 992 Bis- und Poly-2-oxazolidinone, in DE-A-198 54 573 2 -Oxotetrahydro-1,3-oxazin und dessen Derivate, in DE-A-198 54 574 N-Acyl-2-Oxazolidone, in DE-A-102 04 937 zyklische Harnstoffe, in der deutschen Patentanmeldung mit dem Aktenzeichen 10334584.1 bizyklische Amidacetale, in EP-A-1 199 327 Oxetane und zyklische Harnstoffe und in WO-A-03/031482 Morpholin-2,3-dion und dessen Derivate als geeignete Nachvernetzer v) beschrieben.Furthermore are in DE-A-40 20 780 cyclic carbonates, in DE-A-198 07 502 2- Oxazolidone and its derivatives, such as N- (2-hydroxyethyl) -2-oxazolidone, in DE-A-198 07 992 Bis- and poly-2-oxazolidinone, in DE-A-198 54 573 2 Oxotetrahydro-1,3-oxazine and its derivatives, in DE-A-198 54 574 N-acyl-2-oxazolidones, in DE-A-102 04 937 cyclic ureas, in the German patent application with the file number 10334584.1 bicyclic amide acetals, in EP-A-1 199 327 Oxetane and cyclic ureas and in WO-A-03/031482 Morpholine-2,3-dione and its derivatives are described as suitable post-crosslinkers v).

Die Nachvernetzung wird üblicherweise so durchgeführt, dass eine Lösung des Nachvernetzers auf das Hydrogel oder die trockenen Grundpolymerpartikel aufgesprüht wird. Im Anschluss an das Aufsprühen wird thermisch getrocknet, wobei die Nachvernetzungsreaktion sowohl vor als auch während der Trocknung stattfinden kann.The post-crosslinking is usually carried out so that a solution of the postcrosslinker is sprayed onto the hydrogel or the dry base polymer particles. Subsequent to the spraying, it is thermally dried, whereby the postcrosslinking reaction can take place both before and during the drying.

Das Aufsprühen einer Lösung des Vernetzers wird vorzugsweise in Mischern mit bewegten Mischwerkzeugen, wie Schneckenmischer, Paddelmischer, Scheibenmischer, Pflugscharmischer und Schaufelmischer, durchgeführt werden. Besonders bevorzugt sind Vertikalmischer, ganz besonders bevorzugt sind Pflugscharmischer und Schaufelmischer. Geeignete Mischer sind beispielsweise Lödige®-Mischer, Bepex®-Mischer, Nauta®-Mischer, Processall®-Mischer und Schugi®-Mischer.The spraying of a solution of the crosslinker is preferably carried out in mixers with agitated mixing tools, such as screw mixers, paddle mixers, disk mixers, plowshare mixers and paddle mixers. Vertical mixers are particularly preferred, plowshare mixers and paddle mixers are very particularly preferred. Suitable mixers are, for example, Lödige® mixers, Bepex® mixers, Nauta® mixers, Processall® mixers and Schugi® mixers.

Die thermische Trocknung wird vorzugsweise in Kontakttrocknern, besonders bevorzugt Schaufeltrocknern, ganz besonders bevorzugt Scheibentrocknern, durchgeführt. Geeignete Trockner sind beispielsweise Bepex®-Trockner und, Nara®-Trockner. Überdies können auch Wirbelschichttrockner eingesetzt werden.The thermal drying is preferably carried out in contact dryers, more preferably paddle dryers, very particularly preferably disk dryers. Suitable dryers include Bepex® dryers and, Nara® dryers. Moreover, fluidized bed dryers can also be used.

Die Trocknung kann im Mischer selbst erfolgen, durch Beheizung des Mantels oder Einblasen von Warmluft. Ebenso geeignet ist ein nachgeschalteter Trockner, wie beispielsweise ein Hordentrockner, ein Drehrohrofen oder eine beheizbare Schnecke. Es kann aber auch beispielsweise eine azeotrope Destillation als Trocknungsverfahren benutzt werden.The drying can take place in the mixer itself, by heating the jacket or blowing hot air. Also suitable is a downstream dryer, such as a hopper dryer, a rotary kiln or a heatable screw. However, it is also possible, for example, to use an azeotropic distillation as the drying process.

Bevorzugte Trocknungstemperaturen liegen im Bereich 50 bis 250°C, bevorzugt bei 50 bis 200°C, und besonders bevorzugt bei 50 bis 150°C. Die bevorzugte Verweilzeit bei dieser Temperatur im Reaktionsmischer oder Trockner beträgt unter 30 Minuten, besonders bevorzugt unter 10 Minuten.Preferred drying temperatures are in the range 50 to 250 ° C, preferably at 50 to 200 ° C, and particularly preferably at 50 to 150 ° C. The preferred residence time at this temperature in the reaction mixer or dryer is less than 30 minutes, more preferably less than 10 minutes.

Das erfindungsgemäße Klassierverfahren wird vorzugsweise nach der Trocknung des Grundpolymers, vor der Nachvernetzung und/oder nach der Nachvernetzung durchgeführt. Der Wassergehalt des wasserabsorbierenden Harzes beträgt nach der Trocknung des Grundpolymers bzw. vor der Nachvernetzung typischerweise 2 bis 10 Gew.-% und nach der Nachvernetzung typischerweise unter 1 Gew.-%, vorzugsweise unter 0,1 Gew.-%.The classification method according to the invention is preferably carried out after the drying of the base polymer, before the post-crosslinking and / or after the post-crosslinking. The water content of the water-absorbing resin after drying of the base polymer or before the post-crosslinking is typically from 2 to 10% by weight. and after postcrosslinking, typically below 1% by weight, preferably below 0.1% by weight.

Die Vorrichtung zur Durchführung des erfindungsgemäßen Verfahrens umfasst

  1. a) ein Gehäuse,
  2. b) eine Zuführung für das zu klassierende Gut,
  3. c) mindestens ein Sieb,
  4. d) mindestens zwei Abführungen für das klassierte Gut,
  5. e) eine Vorrichtung zur Druckregelung,
  6. f) gegebenenfalls eine Gaszufuhr und
  7. g) gegebenenfalls eine thermische Isolierung.
The device for carrying out the method according to the invention comprises
  1. a) a housing,
  2. b) a feed for the material to be classified,
  3. c) at least one sieve,
  4. d) at least two discharges for the classified good,
  5. e) a pressure regulating device,
  6. f) optionally a gas supply and
  7. g) optionally a thermal insulation.

Eine thermische Isolierung ist eine zusätzliche Materialschicht auf der Siebvorrichtung, die die Wärmeverluste die Siebvorrichtung nach Außen veringert.Thermal insulation is an additional layer of material on the screen which reduces the heat loss of the screen to the outside.

BeispieleExamples Beispiel 1example 1

In einen Lödige-Pflugscharkneter Typ VT 5R-MK (5 I Volumen) wurden 388 g entionisiertes Wasser, 173,5 g Acrylsäure, 2033,2 g einer 37,3 gew.-%igen Natriumacrylatlösung (100 mol% neutralisiert) sowie 4,50 g 15-fach ethoxiliertes Trimethylolpropantriacrylat (beispielsweise Sartomer® SR9035) vorgelegt und unter Durchperlen von Stickstoff 20 Minuten inertisiert. Dann wurde durch Zusatz (verdünnte wässrige Lösungen) von 2,112 g Natriumpersulfat, 0,045 g Ascorbinsäure sowie 0,126 g Wasserstoffperoxid bei 23°C gestartet. Nach dem Start wurde die Temperatur des Heizmantels der Reaktionstemperatur im Reaktor mittels Regelung nachgeführt. Das letztlich erhaltene krümelige Gel wurde dann bei 160 °C für 3 Stunden im Umlufttrockenschrank getrocknet. Anschließend wurde gemahlen und auf 250 bis 850 µm abgesiebt. Der Wassergehalt betrug 2,7 Gew.-%.In a Lödige ploughshare kneader type VT 5R-MK (5 l volume), 388 g of deionized water, 173.5 g of acrylic acid, 2033.2 g of a 37.3% strength by weight sodium acrylate solution (100 mol% neutralized) and 4, 50 g of 15-fold ethoxylated trimethylolpropane triacrylate (for example, Sartomer® SR9035) and rendered inert under bubbling nitrogen for 20 minutes. It was then started by addition (dilute aqueous solutions) of 2.121 g of sodium persulfate, 0.045 g of ascorbic acid and 0.126 g of hydrogen peroxide at 23 ° C. After the start, the temperature of the heating mantle was adjusted to the reaction temperature in the reactor by means of control. The crumbly gel finally obtained was then dried at 160 ° C for 3 hours in a convection oven. It was then ground and sieved to 250 to 850 microns. The water content was 2.7% by weight.

Das gemahlene Grundpolymer wurde mit der angegebenen Temperatur auf das Sieb gegeben. Das Sieb konnte bei vermindertem Druck betrieben werden. Zusätzlich wurde das Sieb mit vorgewärmter Luft mit definiertem Wasserdampfgehalt überdeckt. Die Luftmenge betrug 2 m3/h pro m2 Siebfläche. Bsp. Temperatur des Grundpolymers [°C] Druck [mbar] Temperatur des Gasstroms [°C] Wasserdampfgehalt des Gasstroms [g/kg] Siebverhalten 1 60 500 55 4 1 2 60 500 75 4 1 3 60 500 35 4 2 4 60 500 25 4 3 5 50 500 50 2 1 6 50 1013 50 2 2 7 60 500 60 2 1 8 60 500 60 4 2 9 60 500 60 6 3 Siebverhalten:
1 geringe Anbackungen an Sieb und Wandung, keine Verbackungen im gesiebten Produkt
2 geringe Anbackungen an Sieb und Wandung, geringe Verbackungen im gesiebten Produkt
3 Anbackungen an Sieb und Wandung, Verbackungen im gesiebten Produkt The ground base polymer was added to the sieve at the indicated temperature. The sieve could be operated at reduced pressure. In addition, the screen was covered with preheated air with defined water vapor content. The amount of air was 2 m 3 / h per m 2 screen area. Ex. Temperature of the base polymer [° C] Pressure [mbar] Temperature of gas flow [° C] Water vapor content of the gas stream [g / kg] sieving 1 60 500 55 4 1 2 60 500 75 4 1 3 60 500 35 4 2 4 60 500 25 4 3 5 50 500 50 2 1 6 50 1013 50 2 2 7 60 500 60 2 1 8th 60 500 60 4 2 9 60 500 60 6 3 sieving:
1 slight caking on sieve and wall, no caking in the sieved product
2 low caking on sieve and wall, low caking in the sieved product
3 caking on sieve and wall, caking in sieved product

Claims (15)

  1. A process for classifying a particulate water-absorbing resin using a sieving apparatus, which process comprises operating the sieving apparatus at a reduced pressure compared with the ambient pressure and a gas stream passing over the resin during the classifying process, the gas stream having a temperature of not less than 40°C upstream of the sieving apparatus.
  2. The process according to claim 1 wherein the sieving apparatus is operated at a pressure of not more than 950 mbar.
  3. The process according to claim 2 wherein the sieving apparatus is operated at a pressure in the range from 300 to 700 mbar.
  4. The process according to any one of claims 1 to 3 wherein the gas rate is in the range from 0.1 to 10 m3/h per m2 of sieve area.
  5. The process according to claim 4 wherein the gas stream is air.
  6. The process according to any one of claims 1 to 5 wherein the gas stream has a temperature in the range from 40 to 120°C.
  7. The process according to any one of claims 4 to 6 wherein the water content of the gas stream is less than 5 g/kg.
  8. The process according to any one of claims 4 to 7 wherein the gas volume stream is in the range from 1 to 10 m3/h per m2 sieve area, the gas volume being measured at a temperature of 25°C and a pressure of 1 bar.
  9. The process according to any one of claims 1 to 8 wherein the sieving apparatus is partly or wholly thermally insulated.
  10. The process according to any one of claims 1 to 9 wherein the temperature of the sieving apparatus is in the range from 40 to 80°C.
  11. The process according to any one of claims 1 to 10 wherein the sieving apparatus vibrates.
  12. The process according to claim 11 wherein the frequency of vibration is in the range from 1 to 100 Hz.
  13. The process according to any one of claims 1 to 12 wherein the particulate water-absorbing resin is obtained by addition polymerization of a solution comprising acrylic acid and/or methacrylic acid.
  14. The process according to claim 13 wherein the acrylic acid and/or methacrylic acid is at least 40o neutralized.
  15. Sieving apparatus for carrying out a process according to any one of claims 1 to 14, comprising
    a) a housing,
    b) a feed line for the material to be classified,
    c) at least one sieve,
    d) at least two exit lines for the classified material,
    e) an apparatus for pressure closed loop control,
    f) a gas feed,
    wherein the sieving apparatus is operated at a reduced pressure compared with the ambient pressure and the gas stream is heated to a temperature of not less than 40°C upstream of the sieving apparatus.
EP05821876.9A 2005-01-13 2005-12-31 Method for grading a particulate water-absorbing resin Active EP1838463B2 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE102005001789A DE102005001789A1 (en) 2005-01-13 2005-01-13 A method of classifying a particulate water-absorbent resin
PCT/EP2005/014163 WO2006074816A1 (en) 2005-01-13 2005-12-31 Method for grading a particulate water-absorbing resin

Publications (3)

Publication Number Publication Date
EP1838463A1 EP1838463A1 (en) 2007-10-03
EP1838463B1 true EP1838463B1 (en) 2011-06-22
EP1838463B2 EP1838463B2 (en) 2019-08-14

Family

ID=36011074

Family Applications (1)

Application Number Title Priority Date Filing Date
EP05821876.9A Active EP1838463B2 (en) 2005-01-13 2005-12-31 Method for grading a particulate water-absorbing resin

Country Status (8)

Country Link
US (1) US8104621B2 (en)
EP (1) EP1838463B2 (en)
JP (1) JP2008526498A (en)
CN (1) CN101102854B (en)
AT (1) ATE513627T1 (en)
DE (1) DE102005001789A1 (en)
TW (1) TW200631676A (en)
WO (1) WO2006074816A1 (en)

Families Citing this family (28)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20090261023A1 (en) * 2006-09-25 2009-10-22 Basf Se Method for the Classification of Water Absorbent Polymer Particles
US7967148B2 (en) 2006-09-25 2011-06-28 Basf Se Method for grading water-absorbent polymer particles
EP2076338B2 (en) † 2006-09-25 2022-01-26 Basf Se Method for grading water-absorbent polymer particles
JP5308344B2 (en) * 2007-03-26 2013-10-09 株式会社日本触媒 Method for classifying particulate water-absorbing resin
US8148485B2 (en) 2008-03-13 2012-04-03 Nippon Shokubai Co., Ltd. Production method for water-absorbing resin
CN101980936B (en) 2008-03-28 2014-07-23 株式会社日本触媒 Transport method for absorbend resin powder
JP5390511B2 (en) 2008-04-11 2014-01-15 株式会社日本触媒 Surface treatment method for water absorbent resin and method for producing water absorbent resin
SG194348A1 (en) 2008-09-16 2013-11-29 Nippon Catalytic Chem Ind Production method and method for enhancing liquid permeability of water-absorbing resin
EP2398597B1 (en) 2009-02-18 2018-01-24 Basf Se Method for the production of water-absorbing polymer particles
EP2415822B1 (en) 2009-03-31 2019-03-20 Nippon Shokubai Co., Ltd. Process for producing particulate water-absorbing resin
WO2011034146A1 (en) 2009-09-16 2011-03-24 株式会社日本触媒 Method for producing water absorbent resin powder
WO2011042468A2 (en) 2009-10-09 2011-04-14 Basf Se Method for re-wetting surface post-cross-linked, water-absorbent polymer particles
WO2011090130A1 (en) 2010-01-20 2011-07-28 株式会社日本触媒 Method for producing water absorbent resin
EP2535369B1 (en) 2010-02-10 2021-03-24 Nippon Shokubai Co., Ltd. Process for producing water-absorbing resin powder
US9233186B2 (en) 2010-03-12 2016-01-12 Nippon Shokubai Co., Ltd. Process for producing water-absorbing resin
JP5744840B2 (en) 2010-03-17 2015-07-08 株式会社日本触媒 Method for producing water absorbent resin
CN104212105B (en) 2010-04-07 2017-08-01 株式会社日本触媒 The manufacture method of polyacrylic acid (salt) water-absorbent resin powder, polyacrylic acid (salt) water-absorbent resin powder
US8765906B2 (en) 2010-04-27 2014-07-01 Nippon Shokubai, Co., Ltd. Method for producing polyacrylic acid (salt) type water absorbent resin powder
US9580519B2 (en) 2011-04-20 2017-02-28 Nippon Shokubai Co., Ltd. Method and apparatus for producing polyacrylic acid (salt)-based water absorbent resin
EP2727953B1 (en) 2011-06-29 2017-03-08 Nippon Shokubai Co., Ltd. Polyacrylic acid (salt) water-absorbent resin powder, and method for producing same
CN103946248B (en) * 2011-11-16 2016-08-24 株式会社日本触媒 The manufacture method of polyacrylic acid (salt) water-absorbent resin
JP5996651B2 (en) 2012-08-01 2016-09-21 株式会社日本触媒 Method for producing polyacrylic acid (salt) water-absorbing resin
US9550843B2 (en) 2012-11-27 2017-01-24 Nippon Shokubai Co., Ltd. Method for producing polyacrylic acid (salt)-based water absorbent resin
KR102357517B1 (en) 2013-09-30 2022-02-04 가부시키가이샤 닛폰 쇼쿠바이 Granular water-absorbent filling method and granular water-absorbent sampling method
EP3263607B1 (en) * 2015-02-24 2019-06-05 Sumitomo Seika Chemicals CO. LTD. Water-absorbent resin production apparatus
US10537874B2 (en) 2015-04-02 2020-01-21 Nippon Shokubai Co., Ltd. Method for producing particulate water-absorbing agent
EP3464427B1 (en) 2016-05-31 2021-01-06 Basf Se Method for the production of superabsorbers
CN110799275A (en) * 2017-07-31 2020-02-14 巴斯夫欧洲公司 Method for classifying superabsorbent polymer particles

Family Cites Families (20)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1241774A (en) * 1969-05-28 1971-08-04 Simon Ltd Henry Improvements in or relating to sieving
US3948764A (en) * 1974-09-23 1976-04-06 Browning-Ferris Industries, Inc. Catalyst screening unit
US4261817A (en) * 1978-05-26 1981-04-14 Philip Edwards Sieving
US5122262A (en) * 1990-01-12 1992-06-16 Summers Thomas W Separator screen with intermittent vacuum
JP3077988B2 (en) * 1990-02-13 2000-08-21 株式会社日立製作所 Wet grinding / mixing and drying equipment
DE69108804T2 (en) * 1990-07-17 1995-08-24 Sanyo Chemical Ind Ltd Process for the production of water-absorbent resins.
JPH06126252A (en) † 1992-10-16 1994-05-10 Ube Ind Ltd Method for improving quality of fly ash
USRE38444E1 (en) * 1994-06-13 2004-02-24 Nippon Shokubai Co., Ltd. Absorbing agent, process of manufacturing same, and absorbent product containing same
US5981070A (en) † 1995-07-07 1999-11-09 Nippon Shokubai Co., Ltd Water-absorbent agent powders and manufacturing method of the same
JP3875757B2 (en) * 1997-01-27 2007-01-31 株式会社日本触媒 Method for classifying particulate hydrophilic polymer and sieving device
JPH11179187A (en) * 1997-12-24 1999-07-06 Terunaito:Kk Powder supplying apparatus equipped with dispersing mechanism, production of aqueous polymer solution by employing thereof, and treatment of wastewater or mud containing water in high content
US6124391A (en) † 1998-08-18 2000-09-26 Stockhausen Gmbh & Co. Kg Superabsorbent polymers having anti-caking characteristics
US6906159B2 (en) † 2000-08-03 2005-06-14 Nippon Shokubai Co., Ltd. Water-absorbent resin, hydropolymer, process for producing them, and uses of them
JP3822812B2 (en) * 2000-10-23 2006-09-20 株式会社日本触媒 Water absorbing agent and method for producing the same
US6716894B2 (en) † 2001-07-06 2004-04-06 Nippon Shokubai Co., Ltd. Water-absorbent resin powder and its production process and uses
JP2003320308A (en) † 2002-04-30 2003-11-11 Sumitomo Chem Co Ltd Sieving method for granulated matter of hydraulic powder and apparatus therefor
US6875511B2 (en) † 2002-05-30 2005-04-05 Nippon Shokubai Co., Ltd. Production process for particulate water-absorbent resin
US7378453B2 (en) † 2003-03-14 2008-05-27 Nippon Shokubai Co., Ltd. Surface crosslinking treatment method of water-absorbing resin powder
DE102005062929A1 (en) * 2005-12-29 2007-07-05 Basf Ag Preparation of water-absorbing resin, useful in sanitary articles e.g. diapers, comprises polymerizing a reaction mixture comprising hydrophilic monomer and cross-linker
EP2013251B1 (en) * 2006-03-27 2011-09-14 Nippon Shokubai Co.,Ltd. Water absorbing resin with improved internal structure and manufacturing method therefor

Also Published As

Publication number Publication date
US8104621B2 (en) 2012-01-31
EP1838463A1 (en) 2007-10-03
CN101102854A (en) 2008-01-09
JP2008526498A (en) 2008-07-24
EP1838463B2 (en) 2019-08-14
TW200631676A (en) 2006-09-16
CN101102854B (en) 2013-04-17
DE102005001789A1 (en) 2006-07-27
US20080202987A1 (en) 2008-08-28
ATE513627T1 (en) 2011-07-15
WO2006074816A1 (en) 2006-07-20

Similar Documents

Publication Publication Date Title
EP1838463B1 (en) Method for grading a particulate water-absorbing resin
EP1949011B2 (en) Process for preparing water-absorbing polymer particles
EP1919609B1 (en) Method for producing water-absorbing polymer particles
EP2069409B1 (en) Method for the continuous production of water absorbent polymer particles
EP2073943B1 (en) Method for grading water-absorbent polymer particles
EP2076338B1 (en) Method for grading water-absorbent polymer particles
EP2074153B1 (en) Process for preparing color-stable water-absorbing polymer particles with a low degree of neutralization
EP1926758B1 (en) Polymerization method
EP1924609B1 (en) Method for producing water-absorbing polymers
EP2238181B1 (en) Method for the production of water-absorbing polymer particles
EP2225284B1 (en) Method for producing water-absorbing polymer particles
EP1965905B1 (en) Method for the continuous mixing of polymer particles
EP2222398B1 (en) Method for producing water-absorbent polymer particles
EP2129706A1 (en) Method for coating water-absorbent polymer particles
EP2215128B1 (en) Method for the continuous production of water-absorbent polymer particles
EP2225021A1 (en) Device for producing water-absorbent polymer articles
DE102005058631A1 (en) Continuous mixing of water-absorbent polymer with liquid, e.g. to make crosslinkable material for hygiene articles, involves using a rotating stirrer to give the particles an impetus against the product flow direction

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

17P Request for examination filed

Effective date: 20070813

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HU IE IS IT LI LT LU LV MC NL PL PT RO SE SI SK TR

RAP1 Party data changed (applicant data changed or rights of an application transferred)

Owner name: BASF SE

DAX Request for extension of the european patent (deleted)
17Q First examination report despatched

Effective date: 20090213

GRAP Despatch of communication of intention to grant a patent

Free format text: ORIGINAL CODE: EPIDOSNIGR1

GRAS Grant fee paid

Free format text: ORIGINAL CODE: EPIDOSNIGR3

GRAA (expected) grant

Free format text: ORIGINAL CODE: 0009210

AK Designated contracting states

Kind code of ref document: B1

Designated state(s): AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HU IE IS IT LI LT LU LV MC NL PL PT RO SE SI SK TR

REG Reference to a national code

Ref country code: GB

Ref legal event code: FG4D

Free format text: NOT ENGLISH

REG Reference to a national code

Ref country code: CH

Ref legal event code: EP

REG Reference to a national code

Ref country code: IE

Ref legal event code: FG4D

Free format text: LANGUAGE OF EP DOCUMENT: GERMAN

REG Reference to a national code

Ref country code: DE

Ref legal event code: R096

Ref document number: 502005011544

Country of ref document: DE

Effective date: 20110811

REG Reference to a national code

Ref country code: NL

Ref legal event code: VDEP

Effective date: 20110622

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: SE

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20110622

Ref country code: LT

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20110622

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: FI

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20110622

Ref country code: SI

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20110622

Ref country code: LV

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20110622

Ref country code: CY

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20110622

Ref country code: GR

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20110923

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: NL

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20110622

REG Reference to a national code

Ref country code: IE

Ref legal event code: FD4D

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: EE

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20110622

Ref country code: CZ

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20110622

Ref country code: IE

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20110622

Ref country code: PT

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20111024

Ref country code: IS

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20111022

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: SK

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20110622

Ref country code: RO

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20110622

Ref country code: PL

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20110622

PLBI Opposition filed

Free format text: ORIGINAL CODE: 0009260

PLBI Opposition filed

Free format text: ORIGINAL CODE: 0009260

26 Opposition filed

Opponent name: EVONIK STOCKHAUSEN GMBH

Effective date: 20120321

PLAX Notice of opposition and request to file observation + time limit sent

Free format text: ORIGINAL CODE: EPIDOSNOBS2

26 Opposition filed

Opponent name: EVONIK STOCKHAUSEN GMBH

Effective date: 20120321

Opponent name: NIPPON SHOKUBAI CO., LTD.

Effective date: 20120321

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: IT

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20110622

REG Reference to a national code

Ref country code: DE

Ref legal event code: R026

Ref document number: 502005011544

Country of ref document: DE

Effective date: 20120321

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: DK

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20110622

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: MC

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20111231

REG Reference to a national code

Ref country code: CH

Ref legal event code: PL

GBPC Gb: european patent ceased through non-payment of renewal fee

Effective date: 20111231

PLBB Reply of patent proprietor to notice(s) of opposition received

Free format text: ORIGINAL CODE: EPIDOSNOBS3

REG Reference to a national code

Ref country code: FR

Ref legal event code: ST

Effective date: 20120831

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: GB

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20111231

Ref country code: CH

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20111231

Ref country code: LI

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20111231

REG Reference to a national code

Ref country code: AT

Ref legal event code: MM01

Ref document number: 513627

Country of ref document: AT

Kind code of ref document: T

Effective date: 20111231

PLAB Opposition data, opponent's data or that of the opponent's representative modified

Free format text: ORIGINAL CODE: 0009299OPPO

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: FR

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20120102

Ref country code: ES

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20111003

R26 Opposition filed (corrected)

Opponent name: EVONIK DEGUSSA GMBH

Effective date: 20120321

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: LU

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20111231

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: AT

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20111231

Ref country code: BG

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20110922

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: TR

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20110622

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: HU

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20110622

APAH Appeal reference modified

Free format text: ORIGINAL CODE: EPIDOSCREFNO

APBM Appeal reference recorded

Free format text: ORIGINAL CODE: EPIDOSNREFNO

APBP Date of receipt of notice of appeal recorded

Free format text: ORIGINAL CODE: EPIDOSNNOA2O

APBQ Date of receipt of statement of grounds of appeal recorded

Free format text: ORIGINAL CODE: EPIDOSNNOA3O

PLAB Opposition data, opponent's data or that of the opponent's representative modified

Free format text: ORIGINAL CODE: 0009299OPPO

R26 Opposition filed (corrected)

Opponent name: NIPPON SHOKUBAI CO., LTD.

Effective date: 20120321

APBU Appeal procedure closed

Free format text: ORIGINAL CODE: EPIDOSNNOA9O

PUAH Patent maintained in amended form

Free format text: ORIGINAL CODE: 0009272

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: PATENT MAINTAINED AS AMENDED

27A Patent maintained in amended form

Effective date: 20190814

AK Designated contracting states

Kind code of ref document: B2

Designated state(s): AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HU IE IS IT LI LT LU LV MC NL PL PT RO SE SI SK TR

REG Reference to a national code

Ref country code: DE

Ref legal event code: R102

Ref document number: 502005011544

Country of ref document: DE

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: BE

Payment date: 20231226

Year of fee payment: 19

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: DE

Payment date: 20231227

Year of fee payment: 19