WO2012107344A1 - Method for producing water-absorbing polymer particles - Google Patents

Method for producing water-absorbing polymer particles Download PDF

Info

Publication number
WO2012107344A1
WO2012107344A1 PCT/EP2012/051770 EP2012051770W WO2012107344A1 WO 2012107344 A1 WO2012107344 A1 WO 2012107344A1 EP 2012051770 W EP2012051770 W EP 2012051770W WO 2012107344 A1 WO2012107344 A1 WO 2012107344A1
Authority
WO
WIPO (PCT)
Prior art keywords
monomer
water
polymer particles
absorbing polymer
wt
Prior art date
Application number
PCT/EP2012/051770
Other languages
German (de)
French (fr)
Inventor
Norbert Herfert
Thomas Daniel
Klaus Dieter HÖRNER
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
Priority to EP11153540 priority Critical
Priority to EP11153540.7 priority
Application filed by Basf Se filed Critical Basf Se
Publication of WO2012107344A1 publication Critical patent/WO2012107344A1/en

Links

Classifications

    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08LCOMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L33/00Compositions 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; Compositions of derivatives of such polymers
    • C08L33/02Homopolymers or copolymers of acids; Metal or ammonium salts thereof
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08FMACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F220/00Copolymers 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 a salt, anhydride ester, amide, imide or nitrile thereof
    • C08F220/02Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
    • C08F220/04Acids; Metal salts or ammonium salts thereof
    • C08F220/06Acrylic acid; Methacrylic acid; Metal salts or ammonium salts thereof
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08FMACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F220/00Copolymers 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 a salt, anhydride ester, amide, imide or nitrile thereof
    • C08F220/02Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
    • C08F220/04Acids; Metal salts or ammonium salts thereof
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08FMACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F220/00Copolymers 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 a salt, anhydride ester, amide, imide or nitrile thereof
    • C08F220/02Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
    • C08F220/10Esters
    • C08F220/12Esters of monohydric alcohols or phenols
    • C08F220/14Methyl esters
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08FMACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F220/00Copolymers 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 a salt, anhydride ester, amide, imide or nitrile thereof
    • C08F220/02Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
    • C08F220/52Amides or imides
    • C08F220/54Amides
    • C08F220/58Amides containing oxygen in addition to the carbonamido oxygen
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08FMACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F222/00Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a carboxyl radical and containing at least one other carboxyl radical in the molecule; Salts, anhydrides, esters, amides, imides, or nitriles thereof
    • C08F222/10Esters
    • C08F222/1006Esters of polyhydric alcohols or polyhydric phenols, e.g. ethylene glycol dimethacrylat

Abstract

The invention relates to a method for producing water-absorbing polymer particles having improved swelling speed by polymerizing a monomer solution or monomer suspension containing an ethylenically unsaturated monomer bearing an acid group, an ethylenically unsaturated monomer, a cross-linking agent, and an initiator.

Description

A process for producing water-absorbing polymer particles

The present invention relates to a process for producing water-absorbing polymer particles with improved swell by polymerizing a monomer solution or suspension comprising one ethylenically unsaturated acid-functional monomer, an ethylenically unsaturated monomer, a crosslinking agent and an initiator. Water-absorbing polymer particles are used to produce diapers, tampons, sanitary napkins and other hygiene articles, but also used as water-retaining agents in market gardening. The water-absorbing polymer particles are also referred to as superabsorbents. The production of water-absorbing polymer particles is described in the monograph "Modern Supe- rabsorbent Polymer Technology", FL Buchholz and AT. Graham, Wiley-VCH, 1998, pages 71 to 103. described.

The properties of water-absorbing polymer particles can be adjusted, for example via the amount of crosslinker used. With increasing amount of crosslinker the cen- decreases rifugenretentionskapazität (CRC) and the absorption under a pressure of 21, 0 g / cm 2 (AUL0.3 psi) passes through a maximum.

To improve the application properties, such as permeability of the gel bed gequol- lenen (SFC) in the diaper and Absorbency under a pressure of 49.2 g / cm 2

(AULOJpsi), water-absorbing polymer particles are generally oberflächennach- be networked. Characterized the degree of crosslinking of the particle surface area increases, whereby the absorption under a pressure of 49.2 g / cm 2 (AULOJpsi) and the centrifuge retention capacity (CRC) can be at least partially decoupled. This surface can be performed in aqueous gel phase. Preferably, however, dried, ground and screened polymer particles (base polymer) are coated with a postcrosslinker on the surface and surface thermally surface postcrosslinked. Useful crosslinkers are compounds which can form covalent bonds with at least two carboxylate groups of the water-absorbing polymer particles.

Object of the present invention to provide an improved process for producing water-absorbing polymer particles, in particular of water-absorbing polymeric particles with high swell rate (FSR) and high absorption under pressure of 49.2 g / cm 2 (AULOJpsi).

The object is achieved by a process for producing water-absorbing polymer particles by polymerizing a monomer solution or suspension comprising a) an ethylenically unsaturated acid-functional monomer which may be at least partially neutralized,

b) at least one crosslinker,

c) at least one initiator,

d) at least one copolymerizable with the above-mentioned under a) monomers ethylenically unsaturated monomer and

e) optionally one or more water-soluble polymers, characterized in that the monomer solution or suspension of at least 0.5 equivalents by weight of a crosslinking agent b), with a weight equivalent to the weight percentages of the crosslinker b), based on the unneutralized monomer a), multiplied by (n -1) corresponds to n and the number of ethylenic double bonds in the crosslinker b), and from 7.5 to 50 wt .-% of monomer d), based on the unneutralized monomer a) contains.

The water-absorbing polymer particles are typically water-insoluble.

The monomer a) is preferably water soluble, ie the solubility in water at 23 ° C is typically at least 1 g / 100 g water, preferably at least 5 g / 100 g water, more preferably at least 25 g / 100 g of water, most preferably at least 35 g / 100 g water.

Suitable monomers a) are for example ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, and itaconic acid. Particularly preferred monomers a) are acrylic acid and methacrylic acid. Most particularly preferred is acrylic acid.

Further suitable monomers a) are, for example, ethylenically unsaturated sulfonic acids such as styrenesulfonic acid and 2-acrylamido-2-methylpropanesulfonic acid (AMPS). Impurities can have a considerable influence on the polymerization. Therefore, the raw materials used should have the highest possible purity. Therefore, it is often advantageous to purify the monomers a) specifically. Suitable purification methods are, for example, in WO 2002/055469 A1, WO 2003/078378 A1 and WO 2004/035514 A1. A suitable monomer a) is, for example, according to WO 2004/035514 A1 purified acrylic acid having 99.8460 wt .-% acrylic acid, 0.0950 wt .-% acetic acid,

0.0332 wt .-% water, 0.0203 wt .-% propionic acid, 0.0001 wt .-% furfurals,

0.0001 wt .-% of maleic anhydride, 0.0003 wt .-% diacrylic acid and 0.0050 wt .-% hydroquinone monomethyl ether. The monomer a) typically includes polymerization inhibitors, preferably hydroquinone monoethers, as storage stabilizers. The monomer solution comprises preferably up to 250 ppm by weight, preferably at most

130 ppm by weight, particularly preferably at most 70 ppm by weight, preferably at least

10 ppm by weight, particularly preferably at least 30 ppm by weight and especially about 50 ppm by weight of hydroquinone monoether, based in each case on the unneutralized monomer a). For example, for the preparation of an ethylenically unsaturated monomer, säuregruppentra- constricting monomer with a corresponding content can be of hydroquinone.

Preferred hydroquinone monoethers are hydroquinone monomethyl ether (MEHQ) and / or alpha-tocopherol (vitamin E).

Suitable crosslinkers b) are compounds having at least two groups suitable for crosslinking. Such groups are for example ethylenically unsaturated groups which can be free-radically interpolymerized into the polymer chain and functional groups which can form a) covalent bonds with the acid groups of the monomers. Also suitable are polyvalent metal salts which can form coordinate bonds with at least two acid groups of the monomer a), suitable crosslinkers b).

Crosslinkers b) are preferably compounds having at least two polymerizable groups which can be free-radically interpolymerized into the polymer network. Suitable crosslinkers b) are, for example, ethylene glycol dimethacrylate, diethylene glycol diacrylate, Polyethylenglykoldi- acrylate, allyl methacrylate, trimethylolpropane triacrylate, triallylamine, tetraallylammonium chloride, tetraallyloxyethane as described in EP 0530438 A1, di- and triacrylates as described in

described EP 0547847 A1, EP 0559476 A1, EP 0632068 A1, WO 93/21237 A1, WO 2003/104299 A1, WO 2003/104300 A1, WO 2003/104301 A1 and DE 103 31 450 A1, mixed acrylates, which in addition to acrylate groups further ethylenically unsaturated groups, as described in DE 103 31 456 A1 and DE 103 55 401 A1, or crosslinker mixtures as described for example in DE 195 43 368 A1, DE 196 46 484 A1, WO 90/15830 A1 and WO 2002/032962 A2.

Preferred crosslinkers b) are pentaerythritol triallyl ether, tetraallyloxyethane, rylamid Methylenbismethac-, 15-tuply ethoxylated trimethylolpropane triacrylate, polyethylene glycol diacrylate, trimethylolpropane triacrylate, triallylamine, and tetra allyl ammonium chloride. Very particularly preferred crosslinkers b) are the acrylic acid or methacrylic acid to di- or triacrylates esterified multiply ethoxylated and / or propoxylated glycerols as described for example in WO 2003/104301 A1. Particularly advantageous are di- and / or triacrylates of 3- to 10-tuply ethoxylated glycerol. Very particularly preferably di- or triacrylates of 1- to 5-tuply ethoxylated and / or propoxylated glycerol. On master- th preferred are the triacrylates of 3- to 5-tuply ethoxylated and / or propoxylated glycerol, especially the triacrylate of 3-tuply ethoxylated glycerol. The amount of crosslinker b) is preferably from 0.6 to 2 weight equivalents, particularly preferably 0.65 to 1, 5 equivalents by weight, most preferably 0.7 to 1 equivalents by weight, based in each case on the unneutralized monomer a). With increasing crosslinker content, the centrifuge retention capacity (CRC) and absorbance drops below a pressure of 21, 0 g / cm 2 passes through a maximum.

One equivalent weight corresponds to the weight percent of the crosslinker b), based on the unneutralized monomer a) multiplied by (n-1), and n is the number of the ethylenic double bonds in the crosslinker b). For crosslinkers b) with two ethylenic double bonds, such as methylene bisacrylamide, or polyethylene glycol, one percent by weight corresponds to a weight equivalent of crosslinkers b) having three ethylenic double bonds, such as 15-tuply ethoxylated trimethylolpropane triacrylate or triallylamine, corresponds to a weight percent accordingly two weight equivalents. The initiators c) all generating radicals under the polymerization compounds can be used, 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. Preferably, mixtures of thermal initiators and redox initiators are used, such as sodium / hydrogen peroxide / ascorbic acid. The reducing component but is preferably a mixture of the disodium salt of 2-hydroxy-2-sulfinatoacetic acid, (the disodium salt of 2-hydroxy-2-sulfonatoacetic acid and sodium bisulfite available as Brüggolit® FF6 and FF7 Brüggolit® from Bruggemann Chemicals; Heilbronn; DE) or the disodium salt of 2-hydroxy-2-sulfinatoacetic acid in a pure form (Avail- borrowed as Blancolen® HP from Bruggemann Chemicals; Heilbronn, DE), are used.

The cash with the ethylenically unsaturated, acid groups-bearing monomers a) copolymerizable ethylenically unsaturated monomers d) are not limited. It is possible that the monomers d) itself ethylenically unsaturated, acid groups-bearing monomers and / or salts thereof. It is important only that the monomers d) from the monomer a) are different.

Suitable monomers d) are for example ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid and itaconic acid, and ethylenically unsaturated sulfonic acids such as styrenesulfonic rolsulfonsäure and 2-acrylamido-2-methylpropanesulfonic acid (AMPS). Particularly preferred monomers d) are methacrylic acid, itaconic acid and 2-acrylamido-2-methylpropanesulfonic acid. Very particular preference is methacrylic acid and 2-acrylamido-2-methyl propane sulfonic acid.

Other suitable monomers d) include acrylamide, methacrylamide, tert-Butylacryl- amide, hydroxyethyl acrylate, hydroxyethyl methacrylate, methyl methacrylate, methyl acrylate, ethyl methacrylate, ethyl acrylate, n-propyl methacrylate, n-propyl acrylate, n-butyl methacrylate, n-Butylacry- lat, tert-butyl methacrylate, tert-butyl acrylate, cyclohexyl methacrylate, cyclohexyl acrylate, dimethylaminoethyl laminoethylmethacrylat, dimethylaminoethyl acrylate, dimethylaminopropyl acrylate, diethylamino ethyl methacrylate, diethylaminopropyl acrylate, dimethylaminoethyl methacrylamide, dimethylaminoethyl noethylacrylamid, dimethylaminopropyl, diethylaminoethyl, Diethylami- nopropylacrylamid, Methylglykolmethacrylat, Methylglykolacrylat, Ethylglykolmethacrylat, ethyl glykolacrylat, n-Propylglykolmethacrylat, n-Propylglykolacrylat, n-Butylglykolmethacrylat, n-butyl tylglykolacrylat, thyldiglykolacrylat Methyldiglykolmethacrylat, Methyldiglykolacrylat, Ethyldiglykolmethacrylat, E, n-Propyldiglykolmethacrylat, n-Propyldiglykolacrylat, n-Butyldiglykolmeth- acrylate, n-Butyldiglykolacrylat, methoxypolyethylene glycol methacrylate, Methoxpolyethylenglyko- lacrylat, ethylene glycol methacrylate Ethoxypolyethylenglykolmethacrylat, Ethoxypolyethylenglykolacrylat, n-Propoxypoly-, n-Propoxypolyethylenglykolacrylat, n-Butoxypolyethylenglykol- methacrylate, n-Butoxypolyethylenglykolacrylat and vinylformamide. Particularly preferred monomers d) are acrylamide, tert-butylacrylamide, dimethylaminoethyl methacrylate, M ethyl methacrylate, methyl acrylate, tert-butyl methacrylate, cyclohexyl methacrylate, n-Butyldiglykolmethacrylat, Methoxypolyglykolmethacrylat and vinylformamide. Very particularly preferably methyl. Other suitable monomers d) include 2-Trimethylammoniumethylmethacrylat- chloride, 2-Triethylammoniumethylacrylat chloride, 3-Trimethylammoniumpropylacrylat chloride,

2- Triethylammoniumethylmethacrylat chloride, 3-Triethylammoniumpropylacrylat chloride, 2-tri- methylammoniumethylmethacrylamid chloride, 2-Trimethylammoiumethylacrylamid chloride,

3- Trimethylammoniumpropylacrylamid chloride, 2-Triethylammoniumethylmethacrylamid chloride and 3-Triethylammoniumpropylacrylamid chloride. Particularly preferred monomers d) are

2-Trimethylammoniumethylmethacrylamid chloride and 3-Trimethylammoniumpropylacrylamid- chloride.

The monomer solution or suspension contains from 7.5 to 50 wt .-%, preferably 9 to 44 wt .-%, particularly preferably from 10 to 30 wt .-%, most preferably from 15 to 25 wt .-%, of the monomers d), in each case based on the unneutralized monomer a).

By the copolymerization of the monomers a) with the monomers d) the polymer chains formed are disturbed. Thus, the swell rate may be increased (FSR). The decrease of the absorption under a pressure of 49.2 g / cm 2 (AULOJpsi) can be compensated by a corresponding increase of the amounts of crosslinker b).

As water-soluble polymers e) include polyvinyl alcohol, polyvinylpyrrolidone, starch, starch derivatives, modified cellulose, such as methylcellulose or hydroxyethylcellulose, gelatin, polyglycols or polyacrylic acids, preferably starch, starch derivatives and modified cellulose may be used.

Typically, an aqueous monomer solution is used. The water content of the monomer solution is preferably from 40 to 75 wt .-%, particularly preferably from 45 to 70% by weight, most preferably from 50 to 65 wt .-%. It is also possible Monomersuspensio- NEN, ie monomer solutions with excess monomer a), for example sodium use. With increasing water content, the energy consumption increases in the subsequent drying and, with falling water content, the heat of polymerization can only be removed inadequately.

The preferred polymerization inhibitors require dissolved erstoff for optimum effect sow. Therefore, the monomer solution before the polymerization by inertization, ie flowing through with an inert gas, preferably nitrogen or carbon dioxide, be freed of dissolved oxygen. Preferably, the oxygen content of the monomer before the polymerization to less than 1 ppm by weight, particularly preferably to less than 0.5 ppm by weight, very particularly preferably lowered to less than 0.1 ppm by weight.

Suitable reactors are, for example, kneading or belt reactors. In the kneader, the resulting in the polymerization of an aqueous monomer solution or suspension is polyvinyl lymergel comminuted continuously by, for example, in opposite stirring shafts, as described in WO 2001/038402 A1. The polymerization on the belt is described for example in DE 38 25 366 A1 and US 6,241, 928th In the polymerization in a belt reactor a polymer gel which has to be comminuted in a further process step, for example in an extruder or kneader is produced.

For improving the drying properties of the decomposed kleinerte polymer gel obtained by means of a kneader, can also be extruded.

but it is also possible to aqueous monomer to dropletize and to polymerize the droplets obtained in a heated carrier gas stream. Here, the process steps of polymerization and drying can be summarized as described in WO 2008/040715 A2 and WO 2008/052971 A1.

The acid groups of the polymer gels are typically partly neutralized. The neutralization is preferably carried out at the stage of the monomers. This is usually done by mixing in the neutralizing agent as an aqueous solution or forthcoming is also given to as a solid. The degree of neutralization is preferably from 25 to 95 mol%, particularly preferably from 30 to 80 mol%, very particularly preferably from 40 to 75 mol%, for which 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 very particular preference is given to sodium hydroxide, sodium carbonate or sodium hydrogen carbonate and mixtures thereof.

However, it is also possible for the neutralization after the polymerization carried out at the stage of forming in the polymerization the polymer gel. Furthermore, it is possible to

to neutralize 40 mol%, preferably 10 to 30 mol%, particularly preferably 15 to 25 mol% of the acid groups before polymerization by already added to a portion of the neutralizing agent to the monomer solution and the desired final degree of neutralization of the only after polymerization, at the stage of polymer gel is set. When the polymer gel at least partially neutralized after the polymerization, the polymer gel is preferably comminuted mechanically, for example by means of an extruder, wherein the neutralizing agent is sprayed on, sprinkled or poured on and then be carefully mixed. The gel mass obtained can be repeatedly extruded for homogenization.

The polymer gel is then preferably with a belt dryer dried until the residual moisture content is preferably 0.5 to 15 wt .-%, particularly preferably 1 to 10 wt .-%, most preferably 2 to 8 wt .-%, by weight, wherein the residual moisture content in accordance with recommended by the EDA NA test method No. WSP 230.2-05. "Moisture content" is determined. At too high a residual moisture content, the dried polymer gel has too low a glass transition temperature T g and is difficult to process further. At too low a residual moisture content of the dried polymer gel is too brittle, and in the subsequent comminution steps, undesirably large amounts of polymer particles with too small a particle size ( "fines") in. The solids content of the gel before the drying is preferably from 25 to 90 wt .-% , more preferably from 35 to 70 wt .-%, most preferably from 40 to 60 wt .-%. Alternatively, a fluidized bed dryer or a paddle dryer for the drying may be used. The dried polymer is then ground and classified, useful grinding commonly single or multi-roll mills, preferably two- or three-stage roll mills, pin mills, hammer mills or vibratory mills are used.

The average particle size of the separated fraction as a product polymer particles is preferably at least 200 upstream μιη, particularly preferably μιη from 250 to 600, especially from 300 to 500 μιη. The average particle size of the product fraction can be found in "Particle Size Distribution" by the EDANA recommended test method No. WSP 220.2-05., The mass of the screen fractions are plotted in cumulated form and the mean particle size is determined graphically. The mean particle size here is the value of the mesh size which gives rise to a cumulative 50 wt .-%.

The proportion of particles having a particle size of at least 150 μιη is preferably at least 90 wt .-%, particularly preferably at least 95 wt .-%, most preferably at least 98 wt .-%.

Polymer particles with too small a particle size lower the permeability (SFC). The proportion of excessively small polymer particles ( "fines") should be low.

Excessively small polymer particles are therefore typically removed and transferred to the process rückge-. This is preferably done before, during or immediately after polymerization, ie, before the drying of the polymer gel. The small polymer particles can be wetted with water and / or aqueous surfactant before or during the recirculation. It is also possible in later process steps to separate excessively small polymer particles, for example, after the surface or another coating step. In this case, the recycled are surface to small polymer particles or otherwise coated, for example with fumed silica.

When a kneading reactor used for polymerization, the small polymer particles are preferably added during the last third of the polymerization.

If the added very early small polymer particles, for example, already merlösung to mono-, so characterized the centrifuge retention capacity (CRC) of the water absorbing polymer particles obtained is lowered. but this can be compensated, for example, by adjusting the use amount of crosslinker b).

If the added very late excessively small polymer particles, for example, only in a downstream of the polymerization reactor, for example, an extruder, then the excessively small polymer particles can become difficult to incorporate into the resulting polymer. Insufficiently incorporated, excessively small polymer particles dissolve during the grinding process again, are from the dried polymer in classifying therefore removed again and increase the amount of excessively small polymer particles.

The proportion of particles μιη with a particle size of at most 850, is preferably at least 90 wt .-%, particularly preferably at least 95 wt .-%, most preferably at least 98 wt .-%. The proportion of particles μιη with a particle size of at most 600, is preferably at least 90 wt .-%, particularly preferably at least 95 wt .-%, most preferably at least 98 wt .-%.

Polymer particles with too large particle size lower the swell rate. The proportion of excessively large polymer particles should also be low.

Excessively large polymer particles are therefore typically removed and recycled into the grinding of the dried polymer gel. The polymer particles may be surface to further improve the properties. Suitable surface postcrosslinkers are compounds containing groups which 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 describes di- or polyfunctional alcohols as described in DE 33 14 019 A1, DE 35 23 617 A1 describes and EP 0450922 A2, or .beta.-hydroxyalkylamides, such as in

DE 102 04 938 A1 and US 6,239,230 described. Further, in DE 40 20 780 C1 cyclic carbonates, by DE 198 07 502 A1 Dinon 2-Oxazoli- and its derivatives, such as 2-hydroxyethyl-2-oxazolidinone, in DE 198 07 992 C1 bis- and poly-2-oxazolidinones , in DE 198 54 573 A1 2-oxotetrahydro-1, 3-oxazine and its derivatives, by DE 198 54 574 A1 N-acyl-2-oxazolidinones in DE cyclic ureas 102 04 937 A1, bicyclic in DE 103 34 584 A1 Amidoacetale, in EP 1199327 A2 oxetanes and cyclic ureas and derivatives thereof described in WO 2003/031482 A1 berflächennachvernetzer morpholine-2,3-dione and as suitable O-.

Preferred surface are ethylene carbonate, ethylene glycol diglycidyl ether, conversion reduction products of polyamides with epichlorohydrin and mixtures of propylene glycol and 1, 4-butanediol.

Very particularly preferred surface postcrosslinkers are 2-hydroxyethyl-2-oxazolidinone, 2-oxazolidinone and 1, 3-propanediol.

Furthermore, surface postcrosslinkers which comprise additional polymerizable ethylenically unsaturated groups as described in DE 37 13 601 A1

The amount of surface postcrosslinker is preferably from 0.001 to 2 wt .-%, particularly preferably 0.02 to 1 wt .-%, most preferably from 0.05 to 0.2 wt .-%, each based on the polymer particles.

In a preferred embodiment of the present invention before, during or after the surface in addition to the Oberflächennachvernetzern polyvalen- te cations on the particle surface.

The usable in the inventive method polyvalent cations include for example divalent cations such as the cations of zinc, magnesium, calcium, iron 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. Possible counterions are hydroxide, chloride, bromide, sulfate, hydrogensulfate, carbonate, hydrogencarbonate, nitrate, phosphate, hydrogen phosphate, dihydrogen phosphate and carboxylate, such as acetate, citrate and lactate. There are also possible salts having different counter ions, for example, basic aluminum salts such as aluminum mono Aluminiummonoacetat or lactate. miniummonoacetat aluminum sulfate, aluminum lactate, and aluminum are preferred. Apart from metal salts poly- amines can be used as polyvalent cations.

The amount of polyvalent cation used is, for example, 0.001 to 1, 5 wt .-%, preferably 0.005 to 1 wt .-%, particularly preferably 0.02 to 0.8 wt .-%. based in each case on the polymer particles.

The surface postcrosslinking is typically performed such that a solution of the surface postcrosslinker is sprayed onto the dried polymer particles. After the spraying, the polymer particles are coated with surface thermal drying, wherein the surface postcrosslinking can take place both before and during drying. The spraying of a solution of the surface postcrosslinker is preferably performed in mixers with moving mixing tools, such as screw mixers, disk mixers and shovel mixers. Particular preference is given to horizontal mixers such as paddle mixers, very particular preference to vertical mixers. The distinction in the horizontal mixer and vertical mixer via the bearing of the mixing shaft, ie horizontal mixer having a horizontally mounted mixing shaft and vertical mixers have a vertically mounted mixing shaft. Suitable mixers horizontal Ploughshare® mixers include for example (Gebr Lödige Maschinenbau GmbH;. Paderborn; DE), Vrieco-Nauta Continuous Mixer (Hosokawa Micron BV; Doetinchem; NL), Processall Mixmill Mixer (Processall Incorporated; Cincinnati, US) and Schugi Flexomix® (Hosokawa Micron BV; Doetinchem; NL). but it is also possible the surface postcrosslinker spraying in a fluidized bed.

The surface postcrosslinkers are typically used as an aqueous solution. the penetration depth of the surface postcrosslinker can be adjusted in the polymer particles on the content of nonaqueous solvent and total amount of solvent.

If only water is used as solvent, a surfactant is advantageously added. Characterized the wetting behavior is improved and reduces the tendency to agglomerate. Preferably, however, solvent mixtures are used, for example, isopropanol / water, 1, 3-propanediol / water and propylene glycol / water wherein the Mischungsmas- senverhältnis preferably from 20:80 to 40:60.

The thermal drying is preferably in contact dryers, more preferably paddle dryers, most preferably disk dryers. Suitable dryers include for example Bepex Hosokawa Horizontal Paddle Dryer (Hosokawa Micron GmbH; Leingarten; DE), Hosokawa Bepex disc Dryer (Hosokawa Micron GmbH; Leingarten; DE),

Holo-Flite® dryers (Metso Minerals Industries Inc .; Danville; US) and Nara Paddle Dryer (NARA Machinery Europe; Frechen; DE). Moreover, fluidized bed dryers can be used. Drying may take place in the mixer itself, by heating the jacket or blowing in warm air. Equally suitable is a downstream dryer, for example a tray dryer, a rotary tube oven or a heatable screw. Particularly advantageous is mixed in a fluid bed dryer and dried. Preferred drying temperatures are in the range 100 to 250 ° C, preferably 120 to

220 ° C, particularly preferably 130 to 210 ° C, most preferably 150 to 200 ° C. The preferred residence time at this temperature in the reaction mixer or dryer is preferably upstream at least 10 minutes, more preferably at least 20 minutes, most preferably at least 30 minutes and usually at most 60 minutes.

In a preferred embodiment of the present invention, the wasserabsorbie- leaders polymer particles are cooled after the thermal drying. The cooling is preferably in contact coolers, more preferably paddle coolers, disk coolers very particularly preferably carried out. Suitable coolers include, for example Hosokawa Bepex Horizontal Paddle Cooler (Hosokawa Micron GmbH; Leingarten; DE), Hosokawa Bepex Disc Cooler (Hosokawa Micron GmbH; Leingarten; DE), holo-Flite® coolers (Metso Minerals Industries Inc .; Danville; US ) and Nara paddle cooler (NARA Machinery Europe; Frechen; DE). Moreover, fluidized bed coolers can be used.

In the cooler, the water absorbing polymer particles to 20 to 150 ° C, preferably, particularly preferred, very particularly preferred, cooled off from 40 to 120 ° C 60 to 100 ° C 70 to 90 ° C.

Subsequently, the surface polymer particles can be classified again, be excessively small and / or separated into large polymer particles and recycled to the process.

The surface postcrosslinked polymer particles can be coated or to further improve the properties moistened.

The subsequent moistening is preferably carried out at 30 to 80 ° C, particularly preferably at 35 to 70 ° C, very particularly preferably at 40 to 60 ° C. At excessively low temperatures, the water-absorbing polymer particles tend to agglomerate and at higher temperatures, water already evaporates appreciably. The amount of water used for remoisturizing is preferably from 1 to 10 wt .-%, more preferably from 2 to 8 wt .-%, most preferably from 3 to 5 wt .-%. Through the subsequent moistening the mechanical stability of the polymer particles is increased, and reduces their tendency to static charge. the subsequent moistening is advantageously carried out in the cooler by thermal drying.

Suitable coatings for improving the swell rate and the permeability (SFC) are, for example, inorganic inert substances, such as water-insoluble Metallsal- ze, organic polymers, cationic polymers and di- or polyvalent metal cations. Suitable coatings for dust binding are, for example, polyols. Suitable coatings against the undesired caking tendency of the polymer particles include for example fumed silica such as Aerosil® 200, and surfactants, such as Span® 20. A further object of the present invention are obtainable according to the process of this invention water-absorbing polymer particles. The water-absorbing polymeric particles of the invention have a Zentrifugenretenti- onskapazität (CRC) of typically at least 15 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 , on. The centrifuge retention capacity (CRC) of the wasserabsorbieren- the polymer particles less than 60 is usually g / g.

The water-absorbing polymeric particles of the invention have an absorption under a pressure of 49.2 g / cm 2 (AUL0.7 psi) of typically at least 10 g / g, preferably at least 15 g / g, preferably at least 20 g / g, more preferably at least 22 g / g, most preferably at least 23 g / g. The absorption under a pressure of

49.2 g / cm 2 (AULOJpsi) of the water-absorbing polymer particles is typically less than 30 g / g.

The water-absorbing polymeric particles of the invention have a Flüssigkeitsweiter- conductivity (SFC) of typically at least 50 x 10 -7 cm 3 s / g, preferably at least 80 x 10 -7 cm 3 s / g, preferably at least 100 x 10 -7 cm 3 s / g, particularly preferably at least 120 x 10 -7 cm 3 s / g, most preferably at least 130 x 10 -7 cm 3 s / g. The saline flow conductivity (SFC) of the water-absorbing polymer particles is typically less than 250 x 10 -7 cm 3 s / g.

Another object of the present invention are sanitary articles, water-absorbing polymer particles comprising the present invention, in particular hygiene articles for feminine hygiene, hygiene products for light and heavy incontinence or small animal litter. The production of the hygiene article is in the monograph "Modern Superabsorbent Polymer Technology", FL Buchholz and AT. Graham, Wiley-VCH, 1998, pages 252-258 describes.

The hygiene articles usually comprise a water-impermeable back side, a water pervious topsheet and an absorbent core therebetween from the inventive water-absorbing polymer particles and fibers, preferably cellulose. The proportion of the water-absorbing polymer particles in the absorbent core according to the invention is preferably 20 to 100 wt .-%, preferably 50 to 100 wt .-%. methods:

The standard test methods described below, labeled "WSP" described in "Standard Test Methods for the Nonwovens Industry", 2005 edition, published jointly by the "Worldwide Strategy Partners" EDANA (Avenue Eugene Plasky 157, 1030 Brussels, Belgium ,) and INDA www.edana.org (1100 Crescent Green, Suite 115, Cary,

North Carolina 27518, USA, www.inda.org). This publication is available both from EDANA and from INDA. The measurements should, unless stated otherwise, be carried out at an ambient temperature of 23 ± 2 ° C and a relative humidity of 50 ± 10%. The water-absorbing polymer particles are mixed thoroughly before the measurement. Swell rate (Free Swell Rate)

To determine the swell rate (FSR) 00 g (= W1) of the water-absorbing polymer particles are 1, is weighed into a 25 ml beaker and spread evenly on the bottom thereof. Then, 20 ml of a 0.9 wt .-% saline solution are metered by means of a dispenser in a second beaker and the contents of this beaker are rapidly added to the first and a stopwatch is started. As soon as the last drop is absorbed saline, which confirmed by the disappearance of the reflection on the liquid surface, the stopwatch is stopped. The exact amount of liquid which has been poured from the second beaker and absorbed by the polymer in the first beaker is accurately determined by weighing back the second beaker (= W2). The time required for the absorption, which was measured with the stopwatch, is denoted t. The disappearance of the last drop of liquid on the surface is determined as time t.

Hence the swell rate (FSR) is calculated as follows:

FSR [g / (g * s)] = W2 / (W1xt)

However, when the moisture content of the water absorbing polymer particles is more than 3 wt .-%, the weight should be corrected for this moisture content W1.

Centrifuge Retention Capacity (Centrifuge Retention Capacity)

The centrifuge retention capacity (CRC) of the water-absorbing polymeric particles is determined according to the EDANA recommended test method No. WSP 241.2-05. "Centrifuge Retention Capacity".

Absorption under a pressure of 49.2 g / cm 2 (under absorption Pressure)

The absorption under pressure of 49.2 g / cm 2 (AULOJpsi) of the water is polyvinyl lymerpartikel analogously to the EDANA recommended test method No.. WSP 242.2-05

Determined "Absorption under Pressure", 0 g / cm 2 (AUL0.3 psi), a pressure of 49.2 g / cm 2 (AULOJpsi) is set instead of a pressure of 21. Examples

Preparing the base polymers: Example 1 (Comparative Example)

In a Ploughshare® kneader VT 5R-MK (Gebr. Lödige Maschinenbau GmbH, Paderborn, Germany) were 250.9 g of water, 268.8 g of acrylic acid, 2094.3 g of a

37.3 wt .-% aqueous sodium acrylate solution, and 3.1 g triply ethoxylated glycerol triesters acrylate (0.71 weight equivalents) were charged and made inert by bubbling nitrogen for 20 minutes. Subsequently, the polymerization was conducted at about 25 ° C by addition of 5.1 g of a 15% aqueous sodium persulfate solution .-, 2.2 g of a 0.5% strength aqueous ascorbic .- binsäurelösung and 0.6 g of a 3 wt. -% aqueous hydrogen peroxide solution started. The temperature of the heating mantle was tracked the reaction temperature to complete the reaction adiabatically as possible to an end. The resulting gel was cooled and discharged, and 90 minutes in a convection oven at 175 ° C dried. The product was then ground and screened μιη to 150 to 710th

The resulting water-absorbing polymer particles were analyzed. The results are summarized in Table 1 below.

example 2

In a Ploughshare® kneader VT 5R-MK (Gebr. Lödige Maschinenbau GmbH, Paderborn, Germany) were 250.1 g of water, 254.9 g of acrylic acid, 1887.4 g of a

37.3 wt .-% aqueous sodium acrylate solution, 182.1 g of a 50 .-% aqueous solution of the sodium salt of 2-acrylamido-2-methylpropanesulfonic acid (AMPS) and 3.0 g of triply ethoxylated glycerol triacrylate (0.76 weight equivalents ) are initially introduced and made inert by bubbling nitrogen for 20 minutes. Subsequently, the polymerization was conducted at about 25 ° C by addition of 4.9 g of a 15% aqueous sodium persulfate solution .-, 2.1 g of a 0.5 .-% strength aqueous ascorbic acid and 0.6 g of a 3 wt .-% aqueous hydrogen peroxide solution started. The temperature of the heating mantle was tracked the reaction temperature to complete the reaction adiabatically as possible to an end. The resulting gel was cooled and discharged, and 90 minutes in a convection oven at 175 ° C dried. The product was then ground and screened μιη to 150 to 710th

The resulting water-absorbing polymer particles were analyzed. The results are summarized in Table 1 below. example 3

In a Ploughshare® kneader VT 5R-MK (Gebr. Lödige Maschinenbau GmbH, Paderborn, Germany) were 326.1 g of water, 242.5 g acrylic acid, 1700.1 g of a 37.3 wt .-% aqueous solution of sodium acrylate, 346.4 g of a 50 .-% aqueous solution of the sodium salt of 2-acrylamido-2-methylpropanesulfonic acid (AMPS) and 2.8 g of triply ethoxylated glycerol triacrylate (0.77 weight equivalents) were charged and by bubbling nitrogen for 20 min rendered inert. Subsequently, the polymerization was conducted at about 25 ° C by adding 4.6 g of a 15% aqueous sodium persulfate solution .-, 2.0 g of a 0.5 .-% strength aqueous ascorbic acid solution and 0.5g of a 3 wt .-% aqueous hydrogen peroxide solution started. The temperature of the heating mantle was tracked the reaction temperature to complete the reaction adiabatically as possible to an end. The resulting gel was cooled and discharged, and 90 minutes in a convection oven at 175 ° C dried. The product was then ground and screened μιη to 150 to 710th

The resulting water-absorbing polymer particles were analyzed. The results are summarized in Table 1 below. example 4

In a Ploughshare® kneader VT 5R-MK (Gebr. Lödige Maschinenbau GmbH, Paderborn, Germany) were 318.3 g of water, 226.3 g of acrylic acid, 1987.7 g of a

37.3 wt .-% aqueous sodium acrylate solution, 82.3 g of 2-acrylamido-2-methylpropanesulfonic acid (AMPS) and 3.0 g of triply ethoxylated glycerol triacrylate (0.76 weight equivalents) were charged and by bubbling nitrogen for 20 min rendered inert. Subsequently, the polymerization was conducted at about 25 ° C by addition of 4.9 g of a 15% aqueous sodium persulfate solution .-, 2.1 g of a 0.5 .-% strength aqueous ascorbic acid and 0.6 g of a 3 wt .-% aqueous hydrogen peroxide solution started. The temperature of the heating mantle was tracked the reaction temperature to complete the reaction adiabatically as possible to an end. The resulting gel was cooled and discharged, and 90 minutes in a convection oven at 175 ° C dried. The product was then ground and screened μιη to 150 to 710th The resulting water-absorbing polymer particles were analyzed. The results are summarized in Table 1 below.

Example 5 In a kneader Ploughshare® VT 5R-MK (Gebr. Lödige Maschinenbau GmbH, Paderborn, Germany) were 373.3 g of water, 183.6 g acrylic acid, 1900.8 g of a

37.3 wt .-% aqueous sodium acrylate solution, 183.6 g of a 50 .-% aqueous solution of the sodium salt of 2-acrylamido-2-methylpropanesulfonic acid (AMPS) and 2.8 g of triply ethoxylated glycerol triacrylate (0.77 weight equivalents ) and adding, with Durchper- len of nitrogen for 20 min rendered inert. Subsequently, the polymerization was conducted at about 25 ° C by adding 4.6 g of a 15% aqueous sodium persulfate solution .-, 2.0 g of a 0.5 .-% strength aqueous ascorbic acid solution and 0.5g of a 3 wt .-% aqueous hydrogen peroxide solution started. The temperature of the heating mantle was tracked the Reaktionstempera- structure to carry out the reaction adiabatically as possible to an end. The resulting gel was cooled and discharged, and 90 minutes in a convection oven at 175 ° C dried. The product was then ground and screened μιη to 150 to 710th The resulting water-absorbing polymer particles were analyzed. The results are summarized in Table 1 below.

Example 6 (Comparative Example) In a 2 I stainless steel beaker, 326.7 g of 50 wt .-% sodium hydroxide solution introduced and 849.0 g of frozen, deionized water. With stirring, 392.0 g of acrylic acid were added, the rate of addition was adjusted so that the temperature was 35 ° C is not exceeded. The mixture was then cooled with stirring by means of a cooling bath at 20 ° C. Subsequently, 0.80 g of triply ethoxylated glycerol triacrylate (0.41 wt equivalent) was 0.041 g of 2-hydroxy-2-methyl-1-phenylpropane-1-one (DAROCUR® 1173, Ciba Spe- cialty Chemicals Inc., Basel, Switzerland) and 0.014 g of 2,2-dimethoxy-1, 2-diphenylethane-1-one (IR GACURE® 651, Ciba Specialty Chemicals Inc., Basel, Switzerland) was added. Cooling was continued, and, on reaching 15 ° C the mixture by passing nitrogen was liberated by means of a glass frit of oxygen. On reaching 0 ° C, 0.51 g of sodium persulfate were (dissolved in 5 ml water) and 0.06 g of hydrogen peroxide (dissolved in 6 ml of water) was added and the monomer solution was transferred into a glass dish. The glass dish was dimensioned such that a layer thickness of the monomer solution of 5 cm was established. Subsequently, 0.047 g of mixture of the sodium salt of 2-hydroxy-2-sulfinatoacetic acid, the disodium salt of 2-hydroxy-2-sulfonatoacetic acid and sodium bisulfite (Brüggolit® FF7, L. Brüg- GemAnn KG, Heilbronn, Germany) dissolved in 5 ml water was added and the monomer solution stirred briefly with a glass rod. The glass dish with the monomer solution was placed under a UV lamp (UV intensity = 25 mW / cm 2), wherein the polymerization began. After 16 minutes, the gel was extruded three times using a commercial meat grinder with 6-mm well plate and dried in a laboratory oven at 160 ° C for one hour. The product was then ground and screened to 150 μιη to 600 bar.

The resulting water-absorbing polymer particles were analyzed. The results are summarized in Table 1 below. Example 7 (Comparative Example)

Example 6 was repeated, except that the monomer solution after the neutralization step was additionally 78.4 g of a 50 .-% aqueous solution of the sodium salt of 2-acrylamido-2-methylpropanesulfonic acid (AMPS) was added.

The resulting water-absorbing polymer particles were analyzed. The results are summarized in Table 1 below. Tab. 1: Basic polymers

Figure imgf000018_0001

*) Comparative examples

Na-AMPS: sodium salt of 2-acrylamido-2-methylpropane

AMPS: 2-acrylamido-2-methylpropane

surface post:

Examples 8 to 12

In a Ploughshare® mixer with heating jacket type M5 (Gebr. Lödige Maschinenbau GmbH, Paderborn, Germany) were each 1, 2 kg of basic polymer of Examples 1 to 5 at 185 ° C and a shaft speed of 250 revolutions per minute by means of a two-substance spray nozzle (0.5 bar nitrogen) with the following solution is coated (based on the base polymer):

0.14 wt .-% of N- (2-hydroxyethyl) -2-oxazolidinone

0.7 wt .-% 1, 2-propanediol

2.42 wt .-% water

1, 04 wt .-% isopropanol

0.25 wt .-% of a 2 .-% aqueous solution of sorbitan monooleate After spraying the reaction mixture was maintained at 185 ° C and a shaft speed of 200 revolutions per minute for 40 minutes. The obtained products were allowed to cool again to 23 ° C and sieved to remove agglomerates μιη at 710th

The resulting water-absorbing polymer particles were analyzed. The results are summarized in Table 2 below. Examples 13 and 14

The base polymers of Examples 6 and 7 were for surface postcrosslinking in a Ploughshare® mixer with heating jacket type M5 (Gebr. Lödige Maschinenbau GmbH, Paderborn, Germany) at 23 ° C and a shaft speed of 250 revolutions per minute by means of a two-substance spray coated with the following solution (in each case based on the base polymer):

1, 00 wt .-% 1, 3-propanediol

0.04 wt .-% of N- (2-hydroxyethyl) -2-oxazolidinone

2.0 wt .-% water

0.6 wt .-% of a 22gew .-% aqueous aluminum lactate solution

After spraying, the product temperature was raised to 170 ° C and the reaction rate maintained at this temperature and a shaft speed of 60 rpm mixing for 45 minutes. The obtained products were allowed to cool again to 23 ° C and screened μιη to 150 to 600 bar.

The resulting water-absorbing polymer particles were analyzed. The results are summarized in Table 2 below.

Tab. 2: surface post base polymers

Figure imgf000019_0001

*) Comparative examples

Na-AMPS: sodium salt of 2-acrylamido-2-methylpropane

AMPS: 2-acrylamido-2-methylpropane

Claims

claims
A process for producing water-absorbing polymer particles by polymerizing a monomer solution or suspension comprising a) one ethylenically unsaturated monomer bearing acid groups, which may be at least partially neutralized,
b) at least one crosslinker,
c) at least one initiator,
d) at least one copolymerizable with the above-mentioned under a) monomers ethylenically unsaturated monomer and
e) optionally one or more water-soluble polymers, characterized in that the monomer solution or suspension of at least 0.5 equivalents by weight of a crosslinking agent b), with a weight equivalent to the weight percentages of the crosslinker b), based on the unneutralized monomer a), multiplied by (n -1) corresponds to n and the number of ethylenic double bonds in the crosslinker b), and from 7.5 to 50 wt .-% of monomer d), based on the unneutralized monomer a) contains.
A method according to claim 1, characterized in that the monomer a) is from 25 to 95 mole% neutralized acrylic acid.
A method according to claim 1 or 2, characterized in that the monomer solution or suspension 10 to 30 wt .-% of monomer d), based on the unneutralized monomer a) contains.
A method according to any one of claims 1 to 3, characterized in that the monomer d) 2-acrylamido-2-methylpropanesulfonic acid, methyl acrylate and / or methacrylic Re.
A method according to any one of claims 1 to 4, characterized in that the water-absorbing polymeric particles are post-crosslinked surface by the formation of covalent bonds.
A method according to claim 5, characterized in that before, during or polyvalent cations are applied to the particle surface after the surface.
Water-absorbing polymer particles obtainable by polymerizing a monomer solution or suspension comprising a) one ethylenically unsaturated monomer bearing acid groups, which may be at least partially neutralized,
b) at least one crosslinker,
c) at least one initiator,
d) at least one copolymerizable with the above-mentioned under a) monomers ethylenically unsaturated monomer and
e) optionally one or more water soluble polymers, wherein the monomer solution or suspension of at least 0.5 equivalents by weight of a crosslinking agent b), with a weight equivalent to the weight percentages of the crosslinker b), based on the unneutralized monomer a), multiplied by (n-1) and n corresponds to the number of ethylenic double bonds in the crosslinker b), and from 7.5 to 50% by weight of monomer d), based on the unneutralized monomer a), contained.
Water-absorbing polymer particles according to claim 7, wherein the monomer a) was 25 to 95 mole% neutralized acrylic acid.
Water-absorbing polymer particles according to claim 7 or 8, wherein the monomer solution or suspension 10 to 30 wt .-% of monomer d), based on the unneutrali- catalyzed monomer a) contained.
10. Water-absorbing polymer particles according to one of claims 7 to 9, wherein the monomer d) 2-acrylamido-2-methylpropanesulfonic acid, methyl acrylate and / or methacrylic acid was.
1. 1 Water-absorbing polymer particles according to one of claims 7 to 10, wherein the water-absorbing polymer particles were flächennachvernetzt above by formation of covalent bonds.
12. Water-absorbing polymer particles according to claim 1 1, wherein before, during or after the surface polyvalent cations are applied to the particle surface.
13. Water-absorbing polymer particles according to one of claims 7 to 12, wherein the water absorbing polymer particles have a centrifuge retention capacity of at least 15 g / g.
14. A hygiene article comprising water-absorbing polymeric particles according to any one of claims 7 to. 13
PCT/EP2012/051770 2011-02-07 2012-02-02 Method for producing water-absorbing polymer particles WO2012107344A1 (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
EP11153540 2011-02-07
EP11153540.7 2011-02-07

Publications (1)

Publication Number Publication Date
WO2012107344A1 true WO2012107344A1 (en) 2012-08-16

Family

ID=45592354

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/EP2012/051770 WO2012107344A1 (en) 2011-02-07 2012-02-02 Method for producing water-absorbing polymer particles

Country Status (1)

Country Link
WO (1) WO2012107344A1 (en)

Citations (44)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0083022A2 (en) 1981-12-30 1983-07-06 Seitetsu Kagaku Co., Ltd. Water-absorbent resin having improved water-absorbency and improved water-dispersibility and process for producing same
DE3314019A1 (en) 1982-04-19 1984-01-12 Nippon Catalytic Chem Ind absorbent object
DE3523617A1 (en) 1984-07-02 1986-01-23 Nippon Catalytic Chem Ind water-absorbing medium
DE3713601A1 (en) 1987-04-23 1988-11-10 Stockhausen Chem Fab Gmbh A process for producing a highly water absorbent polymer
DE3825366A1 (en) 1987-07-28 1989-02-09 Dai Ichi Kogyo Seiyaku Co Ltd A process for the continuous production of a acrylpolymergels
WO1990015826A1 (en) * 1989-06-12 1990-12-27 Weyerhaeuser Company Hydrocolloid polymer with improved sorption
WO1990015830A1 (en) 1989-06-12 1990-12-27 Weyerhaeuser Company Hydrocolloid polymer
DE4020780C1 (en) 1990-06-29 1991-08-29 Chemische Fabrik Stockhausen Gmbh, 4150 Krefeld, De
EP0450922A2 (en) 1990-04-02 1991-10-09 Nippon Shokubai Kagaku Kogyo Co. Ltd. Method for production of fluid stable aggregate
EP0530438A1 (en) 1991-09-03 1993-03-10 Hoechst Celanese Corporation A superabsorbent polymer having improved absorbency properties
EP0543303A1 (en) 1991-11-22 1993-05-26 Hoechst Aktiengesellschaft Hydrophilic hydrogels having a high swelling capacity
EP0547847A1 (en) 1991-12-18 1993-06-23 Nippon Shokubai Co., Ltd. Process for producing water-absorbent resin
EP0559476A1 (en) 1992-03-05 1993-09-08 Nippon Shokubai Co., Ltd. Method for the production of absorbent resin
WO1993021237A1 (en) 1992-04-16 1993-10-28 The Dow Chemical Company Crosslinked hydrophilic resins and method of preparation
EP0632068A1 (en) 1993-06-18 1995-01-04 Nippon Shokubai Co., Ltd. Process for preparing absorbent resin
US5484865A (en) * 1992-05-20 1996-01-16 Phillips Petroleum Company Copolymers of ampholytic ion pairs containing vinylic tertiary amine
DE19646484A1 (en) 1995-11-21 1997-05-22 Stockhausen Chem Fab Gmbh The liquid-absorbing polymers, processes for their preparation and their use
DE19543368A1 (en) 1995-11-21 1997-05-22 Stockhausen Chem Fab Gmbh Water-absorbing polymers with improved properties, process for their preparation and their use
DE19807992C1 (en) 1998-02-26 1999-07-15 Clariant Gmbh Water absorbent polymers, surface crosslinked using bis-2-oxazolidinone and/or poly-2-oxazolidinones
EP0937736A2 (en) 1998-02-24 1999-08-25 Nippon Shokubai Co., Ltd. Crosslinking a water-absorbing agent
DE19807502A1 (en) 1998-02-21 1999-09-16 Basf Ag Postcrosslinking process of hydrogels with 2-oxazolidinones
DE19854573A1 (en) 1998-11-26 2000-05-31 Basf Ag Postcrosslinking process of hydrogels with 2-oxo-tetrahydro-1,3-oxazines
DE19854574A1 (en) 1998-11-26 2000-05-31 Basf Ag Postcrosslinking process of hydrogels with N-acyl-2-oxazolidinones
US6239230B1 (en) 1999-09-07 2001-05-29 Bask Aktiengesellschaft Surface-treated superabsorbent polymer particles
WO2001038402A1 (en) 1999-11-20 2001-05-31 Basf Aktiengesellschaft Method for continuously producing cross-linked fine-particle geleous polymerizates
US6241928B1 (en) 1998-04-28 2001-06-05 Nippon Shokubai Co., Ltd. Method for production of shaped hydrogel of absorbent resin
EP1199327A2 (en) 2000-10-20 2002-04-24 Nippon Shokubai Co., Ltd. Water-absorbing agent and process for producing the same
WO2002032962A2 (en) 2000-10-20 2002-04-25 Millennium Pharmaceuticals, Inc. Compositions of human proteins and method of use thereof
WO2002055469A1 (en) 2001-01-12 2002-07-18 Degussa Ag Continuous method for the production and purification of (meth)acrylic acid
WO2003031482A1 (en) 2001-10-05 2003-04-17 Basf Aktiengesellschaft Method for crosslinking hydrogels with morpholine-2,3-diones
DE10204938A1 (en) 2002-02-07 2003-08-21 Stockhausen Chem Fab Gmbh Process for post-crosslinking of a water absorbing polymer surface with a cyclic urea useful in foams, fibers, films, cables, especially sealing materials, liquid absorbing hygiene articles, packaging materials, and soil additives
DE10204937A1 (en) 2002-02-07 2003-08-21 Stockhausen Chem Fab Gmbh Process for post-crosslinking of a water absorbing polymer surface with a cyclic urea useful in foams, fibers, films, cables, especially sealing materials and liquid absorbing hygiene articles
WO2003078378A1 (en) 2002-03-15 2003-09-25 Stockhausen Gmbh (meth)acrylic acid crystal and method for the production and purification of aqueous (meth)acrylic acid
WO2003104300A1 (en) 2002-06-01 2003-12-18 Basf Aktiengesellschaft (meth)acrylic esters of polyalkoxylated trimethylolpropane
WO2003104301A1 (en) 2002-06-11 2003-12-18 Basf Aktiengesellschaft (meth)acrylic esters of polyalkoxylated glycerine
WO2003104299A1 (en) 2002-06-11 2003-12-18 Basf Aktiengesellschaft Method for the production of esters of polyalcohols
WO2004035514A1 (en) 2002-10-10 2004-04-29 Basf Aktiengesellschaft Method for the production of acrylic acid
DE10331450A1 (en) 2003-07-10 2005-01-27 Basf Ag (Meth) acrylate of monoalkoxylated polyols and their preparation
DE10334584A1 (en) 2003-07-28 2005-02-24 Basf Ag Post crosslinking of water absorbing polymers, useful for hygiene articles and packaging, comprises treatment with a bicyclic amideacetal crosslinking agent with simultaneous or subsequent heating
DE10331456A1 (en) 2003-07-10 2005-02-24 Basf Ag (Meth) acrylate alkoxylated unsaturated polyol ethers and their preparation
DE10355401A1 (en) 2003-11-25 2005-06-30 Basf Ag (Meth) acrylate unsaturated amino alcohols and their preparation
WO2008040715A2 (en) 2006-10-05 2008-04-10 Basf Se Method for the production of water absorbent polymer particles by polymerizing drops of a monomer solution
WO2008052971A1 (en) 2006-10-31 2008-05-08 Basf Se Regulation of a process for producing water-absorbing polymer particles in a heated gas phase
WO2011131526A1 (en) * 2010-04-19 2011-10-27 Basf Se Method for producing water-absorbing polymer particles

Patent Citations (44)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0083022A2 (en) 1981-12-30 1983-07-06 Seitetsu Kagaku Co., Ltd. Water-absorbent resin having improved water-absorbency and improved water-dispersibility and process for producing same
DE3314019A1 (en) 1982-04-19 1984-01-12 Nippon Catalytic Chem Ind absorbent object
DE3523617A1 (en) 1984-07-02 1986-01-23 Nippon Catalytic Chem Ind water-absorbing medium
DE3713601A1 (en) 1987-04-23 1988-11-10 Stockhausen Chem Fab Gmbh A process for producing a highly water absorbent polymer
DE3825366A1 (en) 1987-07-28 1989-02-09 Dai Ichi Kogyo Seiyaku Co Ltd A process for the continuous production of a acrylpolymergels
WO1990015826A1 (en) * 1989-06-12 1990-12-27 Weyerhaeuser Company Hydrocolloid polymer with improved sorption
WO1990015830A1 (en) 1989-06-12 1990-12-27 Weyerhaeuser Company Hydrocolloid polymer
EP0450922A2 (en) 1990-04-02 1991-10-09 Nippon Shokubai Kagaku Kogyo Co. Ltd. Method for production of fluid stable aggregate
DE4020780C1 (en) 1990-06-29 1991-08-29 Chemische Fabrik Stockhausen Gmbh, 4150 Krefeld, De
EP0530438A1 (en) 1991-09-03 1993-03-10 Hoechst Celanese Corporation A superabsorbent polymer having improved absorbency properties
EP0543303A1 (en) 1991-11-22 1993-05-26 Hoechst Aktiengesellschaft Hydrophilic hydrogels having a high swelling capacity
EP0547847A1 (en) 1991-12-18 1993-06-23 Nippon Shokubai Co., Ltd. Process for producing water-absorbent resin
EP0559476A1 (en) 1992-03-05 1993-09-08 Nippon Shokubai Co., Ltd. Method for the production of absorbent resin
WO1993021237A1 (en) 1992-04-16 1993-10-28 The Dow Chemical Company Crosslinked hydrophilic resins and method of preparation
US5484865A (en) * 1992-05-20 1996-01-16 Phillips Petroleum Company Copolymers of ampholytic ion pairs containing vinylic tertiary amine
EP0632068A1 (en) 1993-06-18 1995-01-04 Nippon Shokubai Co., Ltd. Process for preparing absorbent resin
DE19646484A1 (en) 1995-11-21 1997-05-22 Stockhausen Chem Fab Gmbh The liquid-absorbing polymers, processes for their preparation and their use
DE19543368A1 (en) 1995-11-21 1997-05-22 Stockhausen Chem Fab Gmbh Water-absorbing polymers with improved properties, process for their preparation and their use
DE19807502A1 (en) 1998-02-21 1999-09-16 Basf Ag Postcrosslinking process of hydrogels with 2-oxazolidinones
EP0937736A2 (en) 1998-02-24 1999-08-25 Nippon Shokubai Co., Ltd. Crosslinking a water-absorbing agent
DE19807992C1 (en) 1998-02-26 1999-07-15 Clariant Gmbh Water absorbent polymers, surface crosslinked using bis-2-oxazolidinone and/or poly-2-oxazolidinones
US6241928B1 (en) 1998-04-28 2001-06-05 Nippon Shokubai Co., Ltd. Method for production of shaped hydrogel of absorbent resin
DE19854573A1 (en) 1998-11-26 2000-05-31 Basf Ag Postcrosslinking process of hydrogels with 2-oxo-tetrahydro-1,3-oxazines
DE19854574A1 (en) 1998-11-26 2000-05-31 Basf Ag Postcrosslinking process of hydrogels with N-acyl-2-oxazolidinones
US6239230B1 (en) 1999-09-07 2001-05-29 Bask Aktiengesellschaft Surface-treated superabsorbent polymer particles
WO2001038402A1 (en) 1999-11-20 2001-05-31 Basf Aktiengesellschaft Method for continuously producing cross-linked fine-particle geleous polymerizates
EP1199327A2 (en) 2000-10-20 2002-04-24 Nippon Shokubai Co., Ltd. Water-absorbing agent and process for producing the same
WO2002032962A2 (en) 2000-10-20 2002-04-25 Millennium Pharmaceuticals, Inc. Compositions of human proteins and method of use thereof
WO2002055469A1 (en) 2001-01-12 2002-07-18 Degussa Ag Continuous method for the production and purification of (meth)acrylic acid
WO2003031482A1 (en) 2001-10-05 2003-04-17 Basf Aktiengesellschaft Method for crosslinking hydrogels with morpholine-2,3-diones
DE10204938A1 (en) 2002-02-07 2003-08-21 Stockhausen Chem Fab Gmbh Process for post-crosslinking of a water absorbing polymer surface with a cyclic urea useful in foams, fibers, films, cables, especially sealing materials, liquid absorbing hygiene articles, packaging materials, and soil additives
DE10204937A1 (en) 2002-02-07 2003-08-21 Stockhausen Chem Fab Gmbh Process for post-crosslinking of a water absorbing polymer surface with a cyclic urea useful in foams, fibers, films, cables, especially sealing materials and liquid absorbing hygiene articles
WO2003078378A1 (en) 2002-03-15 2003-09-25 Stockhausen Gmbh (meth)acrylic acid crystal and method for the production and purification of aqueous (meth)acrylic acid
WO2003104300A1 (en) 2002-06-01 2003-12-18 Basf Aktiengesellschaft (meth)acrylic esters of polyalkoxylated trimethylolpropane
WO2003104299A1 (en) 2002-06-11 2003-12-18 Basf Aktiengesellschaft Method for the production of esters of polyalcohols
WO2003104301A1 (en) 2002-06-11 2003-12-18 Basf Aktiengesellschaft (meth)acrylic esters of polyalkoxylated glycerine
WO2004035514A1 (en) 2002-10-10 2004-04-29 Basf Aktiengesellschaft Method for the production of acrylic acid
DE10331450A1 (en) 2003-07-10 2005-01-27 Basf Ag (Meth) acrylate of monoalkoxylated polyols and their preparation
DE10331456A1 (en) 2003-07-10 2005-02-24 Basf Ag (Meth) acrylate alkoxylated unsaturated polyol ethers and their preparation
DE10334584A1 (en) 2003-07-28 2005-02-24 Basf Ag Post crosslinking of water absorbing polymers, useful for hygiene articles and packaging, comprises treatment with a bicyclic amideacetal crosslinking agent with simultaneous or subsequent heating
DE10355401A1 (en) 2003-11-25 2005-06-30 Basf Ag (Meth) acrylate unsaturated amino alcohols and their preparation
WO2008040715A2 (en) 2006-10-05 2008-04-10 Basf Se Method for the production of water absorbent polymer particles by polymerizing drops of a monomer solution
WO2008052971A1 (en) 2006-10-31 2008-05-08 Basf Se Regulation of a process for producing water-absorbing polymer particles in a heated gas phase
WO2011131526A1 (en) * 2010-04-19 2011-10-27 Basf Se Method for producing water-absorbing polymer particles

Non-Patent Citations (3)

* Cited by examiner, † Cited by third party
Title
F.L. BUCHHOLZ; A.T. GRAHAM: 'Modern Superabsorbent Polymer Technology', 1998, WILEY-VCH Seiten 252 - 258
F.L. BUCHHOLZ; A.T. GRAHAM: 'Modern Superabsorbent Polymer Technology', 1998, WILEY-VCH Seiten 71 - 103
WEN-FU LEE ET AL: "Superabsorbent Polymeric Material V. Synthesis and Swelling Behavior of Sodium Acrylate and Sodium 2-Acrylamide-2-methylpropanesulfonate Copolymeric Gels", JOURNAL OF APPLIED POLYMER SCIENCE, JOHN WILEY & SONS, INC, US, Bd. 69, Nr. 2, 11. Juli 1998 (1998-07-11), Seiten 229-237, XP002637863, ISSN: 0021-8995, DOI: _ *

Similar Documents

Publication Publication Date Title
RU2480481C2 (en) Method of producing additionally cross-linked water-absorbing polymer particles with high absorption by polymerising droplets of solution
EP1130045A2 (en) Water-absorbent resin powder and production process therefor
US9585798B2 (en) Water absorbent storage layers
EP2550306B1 (en) A process for producing water-absorbent polymer particles by polymerizing droplets of a monomer solution
JP5290413B2 (en) Method for producing a water-absorbing polymer particles
JP5599513B2 (en) Polyacrylic acid (salt) -based water absorbent resin powder and its manufacturing method
WO2010057912A1 (en) Method for producing permeable water-absorbing polymer particles through polymerization of drops of a monomer solution
CN102361890B (en) Method for producing surface post-cross-linked, water absorbing polymer particles
JP5718817B2 (en) The method of producing water-absorbent resin powder
US20120085971A1 (en) Process for Producing Thermally Surface Postcrosslinked Water-Absorbing Polymer Particles
JP2011517703A (en) Method of manufacturing surface-crosslinked superabsorbent
US8080620B2 (en) Process for continuously producing water-absorbing polymer particles
JP5629688B2 (en) Polyacrylic acid (salt) -based water absorbent resin and a production method thereof
US10046304B2 (en) Water absorbing agent and method for producing the same
WO2011111855A1 (en) Method for manufacturing a water-absorbing resin
CN102083865B (en) Method for producing water-absorbing polymer particles by polymerizing droplets of a monomer solution
US20110015362A1 (en) Method for Manufacturing Water-Absorbing Polymer Particles with a Low Centrifuge Retention Capacity
EP2922882A1 (en) A process for producing surface-postcrosslinked water-absorbent polymer particles
US10066064B2 (en) Process for remoisturizing surface-postcrosslinked water-absorbing polymer particles
JP5730194B2 (en) Method for producing a water-absorbing polymer particles
EP2445942B1 (en) Process for producing water-absorbing polymer particles with low caking tendency and high absorption under pressure
US20110223413A1 (en) Process for Producing Water Absorbent Polymer Particles by Polymerizing Droplets of a Monomer Solution
WO2011111657A1 (en) Drying method for granular water-containing gel-like cross-linked polymer
US8608096B2 (en) Method for the production of water-absorbing polymer particles
EP2547703A1 (en) A process for producing water-absorbent polymer particles by polymerizing droplets of a monomer solution

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 12703752

Country of ref document: EP

Kind code of ref document: A1

NENP Non-entry into the national phase in:

Ref country code: DE

122 Ep: pct app. not ent. europ. phase

Ref document number: 12703752

Country of ref document: EP

Kind code of ref document: A1