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WO2013144027A1 - Superabsorbant résistant à la décoloration - Google Patents

Superabsorbant résistant à la décoloration Download PDF

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Publication number
WO2013144027A1
WO2013144027A1 PCT/EP2013/056122 EP2013056122W WO2013144027A1 WO 2013144027 A1 WO2013144027 A1 WO 2013144027A1 EP 2013056122 W EP2013056122 W EP 2013056122W WO 2013144027 A1 WO2013144027 A1 WO 2013144027A1
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WO
WIPO (PCT)
Prior art keywords
acid
optionally
polymer
water
added
Prior art date
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PCT/EP2013/056122
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German (de)
English (en)
Inventor
Norbert Herfert
Thomas Daniel
Klaus Dieter HÖRNER
Original Assignee
Basf Se
Basf Schweiz Ag
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
Application filed by Basf Se, Basf Schweiz Ag filed Critical Basf Se
Priority to KR1020147030559A priority Critical patent/KR20140142740A/ko
Priority to CN201380018616.5A priority patent/CN104245760A/zh
Publication of WO2013144027A1 publication Critical patent/WO2013144027A1/fr

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F220/00—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 a salt, anhydride ester, amide, imide or nitrile thereof
    • C08F220/02—Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
    • C08F220/04—Acids; Metal salts or ammonium salts thereof
    • C08F220/06—Acrylic acid; Methacrylic acid; Metal salts or ammonium salts thereof
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
    • A61L15/00—Chemical aspects of, or use of materials for, bandages, dressings or absorbent pads
    • A61L15/16—Bandages, dressings or absorbent pads for physiological fluids such as urine or blood, e.g. sanitary towels, tampons
    • A61L15/42—Use of materials characterised by their function or physical properties
    • A61L15/56—Wetness-indicators or colourants
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
    • A61L15/00—Chemical aspects of, or use of materials for, bandages, dressings or absorbent pads
    • A61L15/16—Bandages, dressings or absorbent pads for physiological fluids such as urine or blood, e.g. sanitary towels, tampons
    • A61L15/42—Use of materials characterised by their function or physical properties
    • A61L15/60—Liquid-swellable gel-forming materials, e.g. super-absorbents
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K5/00—Use of organic ingredients
    • C08K5/0008—Organic ingredients according to more than one of the "one dot" groups of C08K5/01 - C08K5/59
    • C08K5/0025—Crosslinking or vulcanising agents; including accelerators
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K5/00—Use of organic ingredients
    • C08K5/36—Sulfur-, selenium-, or tellurium-containing compounds
    • C08K5/41—Compounds containing sulfur bound to oxygen
    • C08K5/42—Sulfonic acids; Derivatives thereof
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K5/00—Use of organic ingredients
    • C08K5/49—Phosphorus-containing compounds
    • C08K5/51—Phosphorus bound to oxygen
    • C08K5/53—Phosphorus bound to oxygen bound to oxygen and to carbon only
    • C08K5/5317—Phosphonic compounds, e.g. R—P(:O)(OR')2
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2220/00—Aspects relating to sorbent materials
    • B01J2220/50—Aspects relating to the use of sorbent or filter aid materials
    • B01J2220/68—Superabsorbents

Definitions

  • the present invention relates to a color-stable superabsorber, to a process for its preparation and to its use and to hygiene articles containing it.
  • a color-stable superabsorber is to be understood as meaning a superabsorber which does not discolor or only in a comparatively small extent when stored under elevated temperature and atmospheric humidity.
  • Superabsorbents are known. Also, for such materials, terms such as “high swellable polymer” “hydrogel” (often used for the dry form), “hydrogel-forming polymer”, “water-absorbent polymer”, “absorbent gelling material”, “swellable resin”, “water-absorbent resin”, These are crosslinked hydrophilic polymers, in particular polymers of (co) polymerized hydrophilic monomers, graft (co) polymers of one or more hydrophilic monomers on a suitable graft base, crosslinked cellulose or starch ethers, crosslinked carboxymethylcellulose partially cross-linked polyalkylene oxide or natural products swellable in aqueous liquids, such as guar derivatives, with water-absorbing polymers based on partially neutralized acrylic acid being the most widespread.
  • the essential properties of superabsorbents are their ability to multiply their own weight of aqueous liquid absorb the fluid and even under some pressure not to give the liquid again.
  • the superabsorber which is used in the form of a dry powder, transforms into a gel when it absorbs liquid, and accordingly turns into a hydrogel during normal water absorption.
  • Crosslinking is essential for synthetic superabsorbents and an important difference to conventional pure thickeners, as it leads to the insolubility of the polymers in water. Soluble substances would not be useful as superabsorbent.
  • the most important application of superabsorbents is the absorption of body fluids.
  • Superabsorbents are used, for example, in infant diapers, adult incontinence products or feminine hygiene products.
  • Other fields of application are, for example, the water-retaining agents in agricultural horticulture, as water storage for protection against fire, for liquid absorption in food packaging or, more generally, for the absorption of moisture.
  • Superabsorbents can absorb several times their own weight in water and retain them under some pressure.
  • such a superabsorbent has a CRC (Centrifuge Retention Capacity, see below for measurement method) of at least 5 g / g, preferably at least 10 g / g, and most preferably
  • a "superabsorber” may also be a mixture of materially different individual superabsorbers or a mixture of components that are only show in combination superabsorbent properties, it depends less on the material composition than on the superabsorbent properties.
  • Important for a superabsorbent is not only its absorption capacity, but also the ability to retain fluid under pressure (retention, usually expressed as "absorption under load”("AUL") or “absorption against pressure"("AAP”), measurement method, see below ) as well as the permeability, ie the ability to carry over the liquid in the swollen state (usually expressed as "Saline Flow Conductivity"("SFC”), measuring method see below).
  • Swollen gel can hinder the fluid transfer to yet unswollen superabsorbent ("gel blocking”) .
  • Gels with only low gel strength are under an applied pressure (body pressure) deformable, clog pores in the superabsorbent / cellulose fiber absorbent body and thereby prevent the fluid transfer to not yet or not fully swollen superabsorber and the fluid absorption by this not or not fully swollen superabsorber.
  • a higher gel strength is usually due to a higher degree of crosslinking
  • An elegant method for increasing the gel strength is compared to increasing the degree of crosslinking on the surface of the SAP particles
  • dried superabsorbent particles with average crosslinking density are usually subjected to additional crosslinking in a thin surface layer of their particles.
  • Acrylic acid-based superabsorbents which are most commonly used in the market, are prepared by free radical polymerization of acrylic acid in the presence of a crosslinker (the "internal crosslinker"), the acrylic acid before, after or partly before, partly after polymerization is neutralized to a certain extent, usually by adding alkali, usually an aqueous sodium hydroxide solution
  • the polymer gel thus obtained is comminuted (depending on the polymerization reactor used, this can take place simultaneously with the polymerization) and dried (the "base polymer” or “base polymer”) is usually postcrosslinked to the surface of the particles by reacting with other crosslinkers, such as organic crosslinkers or polyvalent cations, for example, aluminum (usually employed as aluminum sulfate) or both, to the particle interior to produce a more crosslinked surface layer.
  • crosslinkers such as organic crosslinkers or polyvalent cations, for example, aluminum (usually employed as aluminum sulfate) or both, to the particle interior to produce a more crosslinked
  • a common problem with superabsorbents is discoloration, which occurs when storing under higher temperature or higher humidity. Such conditions often occur during storage of superabsorbers in tropical or subtropical countries. Under such conditions, superabsorbents tend to yellow, they may even take on brown or almost black coloring. This discoloration of the actually colorless superabsorbent powder is unsightly and undesirable because it is particularly visible in the desired thin hygiene products and consumers reject unsightly hygiene products.
  • the cause of the discoloration is not fully understood, but reactive compounds such as residual monomers from the polymerization, the use of some initiators, impurities of the monomer or of the neutralizing agent, surface postcrosslinkers or stabilizers of the monomers used appear to play a role. Fredric L. Buchholz and Andrew T.
  • the inorganic reducing agent is typically a hypophosphite, phosphite, bisulfite or sulfite
  • the metal salt is typically a colorless (the property "colorless” is often simply called “white"), phosphate, acetate or lactate, but not a halide
  • WO 2006/058 682 A1 discoloration of superabsorbers is avoided if the drying and the postcrosslinking reaction in an atmosphere of you which is substantially free of oxidizing gases.
  • WO 2009/060 062 A1 or WO 2010/012 762 A2 teach the addition of sulfinic acid derivatives to superabsorbers in order to stabilize them against discoloration.
  • EP 1 199 315 A2 teaches the use of a redox initiator system for initiating a polymerization reaction, wherein the redox initiator system contains as reducing part a sulfinic acid or a sulfinate, in particular 2-hydroxysulfinatoacetic acid or a salt thereof.
  • WO 99/18 067 A1 discloses certain hydroxy or aminoalkyl or aryl-sulfinic acid derivatives or mixtures thereof and their use as reducing agents which do not cleave formaldehyde.
  • WO 2004/084 962 A1 relates to the use of these sulfinic acid derivatives as reducing part of a redox initiator for the polymerization of partially neutralized acrylic acid to give superabsorbents.
  • JP 05/086 251 teaches the use of phosphoric acid derivatives or salts thereof, in particular (1 -Hydroxiethan-1, 1-diyl) bisphosphonic acid (also “1 -Hydroxiethyliden-1, 1-diphosphonic acid", “1 -Hydroxiethan- (1 , 1-diphosphonic acid), trivial name "etidronic acid”), ethylenediaminetetra (methylenephosphonic acid), diethylenetriaminepenta (methylenephosphonic acid) or their alkali metal or ammonium salts as stabilizers of superabsorbers against discoloration
  • EP 781 804 A2 teaches the addition of (1 -Hydroxyalkyl-1,1-diyl) bisphosphonic acids, wherein the alkyl radical comprises from 5 up to 23 carbon atoms.
  • EP 668 080 A2 teaches the addition of inorganic acids, organic acids or polyamino acids to superabsorbers, wherein among the stated inorganic acids are also phosphorus-based acids.
  • US 2005/0 085 604 A1 discloses the addition of chelating agents as well as oxidizing or reducing agents to superabsorbents, wherein among the chelating agents are also phosphorus-containing.
  • US 2005/0 272 600 A1 relates to the addition of ion blockers to superabsorbents, which also include organic phosphorus compounds.
  • (1-Hydroxiethan-1, 1-diyl) bisphosphonic acid is one of the examples mentioned.
  • EP 2,112,172 A1 adds an organic phosphorus compound to the monomer solution which is polymerized to the superabsorber, (1-hydroxyethane-1,1-diyl) bisphosphonic acid is mentioned, ethylenediamine tetra (methylenephosphonic acid) is the most preferred compound.
  • US 2009/0 275 470 A1 teaches to add to superabsorbers both chelating agents and preferably inorganic phosphorus compounds, where the chelating agent may also be a phosphorus compound such as, for example, (1-hydroxyhexane-1,1-diyl) bisphosphonic acid or ethylenediaminetetra (methylenephosphonic acid) , Such compounds are also added according to the teaching of WO 2006/109 882 A1 superabsorbers as chelating agents, in addition to phosphorus-containing compounds and sulfur-containing reducing agents are used in different process stages.
  • the chelating agent may also be a phosphorus compound such as, for example, (1-hydroxyhexane-1,1-diyl) bisphosphonic acid or ethylenediaminetetra (methylenephosphonic acid)
  • Such compounds are also added according to the teaching of WO 2006/109 882 A1 superabsorbers as chelating agents, in addition to phosphorus-containing compounds and sulfur-containing reducing agents
  • Another object is to find other or even better superabsorbents stabilized against discoloration, in particular against yellowing or browning when stored under elevated temperature and / or elevated atmospheric humidity, and processes for their preparation.
  • the performance characteristics of the superabsorber in particular its ability to absorb liquid, even under pressure, as well as its ability to transfer fluid, are not or at least not significantly impaired.
  • Further objects of the invention are uses of this superabsorbent, such as sanitary products containing this superabsorbent and processes for their preparation.
  • the object was achieved by a process for the preparation of superabsorbents by polymerization of a monomer solution, the a) at least one ethylenically unsaturated, acid group-carrying monomer which is optionally present at least partially as a salt,
  • the process further comprises drying the polymer obtained and optionally grinding the dried polymer and sieving the ground polymer and optionally surface postcrosslinking the dried and optionally ground and sieved polymer, characterized in that the monomer mixture and / or the Polymer before drying at least one sulfonic acid derivative and the polymer after drying or optionally after the surface postcrosslinking at least one phosphonic acid acid added.
  • the superabsorbers according to the invention show surprisingly good stability against discoloration without their use properties such as CRC, AUL or SFC being significantly impaired.
  • Sulfonic acid derivatives in the context of this invention are compounds of general formula (I) derived from sulfonic acid having the general formula R-SO 2 -OH:
  • R 1 is OH or NR 4 R 5 , where R 4 and R 5 independently of one another are H or C 1 -C 6 -alkyl;
  • alkyl represents straight-chain or branched alkyl groups which preferably have 1-6, in particular 1-4, carbon atoms.
  • alkyl groups are methyl, ethyl, n-propyl, isopropyl, n-butyl, t-butyl, n-hexyl, etc.
  • Alkenyl represents straight-chain or branched alkenyl groups which preferably have 3-8 carbon atoms, in particular 3-6 carbon atoms.
  • a preferred alkenyl group is the allyl group.
  • Cycloalkyl is in particular C 1 -C 6 -cycloalkyl, with cyclopentyl and cyclohexyl being particularly preferred.
  • Aryl also in aralkyl is preferably phenyl or naphthyl. When the aryl group is a phenyl group and is substituted, it preferably has two substituents. These are available in particular in the 2- and / or 4- position.
  • Halogen is F, Cl, Br and I, preferably Cl and Br.
  • M is preferably an ammonium, alkali metal or one equivalent of an alkaline earth metal or zinc ion.
  • Suitable alkali metal ions are in particular sodium and potassium ions, and suitable alkaline earth metal ions are, above all, magnesium, strontium and calcium ions.
  • R 1 is preferably a hydroxy or amino group.
  • R 2 is preferably a hydrogen atom or an alkyl or aryl group which may be substituted as above. It preferably has one or two hydroxyl and / or alkoxy substituents.
  • R 3 is preferably either COOM or COOR 4 (M and R 4 have the meanings given above) or, when R 2 is aryl, which may be substituted as indicated above, also for a hydrogen atom.
  • the superabsorbent contains compounds of the above formula (I) wherein M is an alkali metal ion or one equivalent of an alkaline earth metal or zinc ion; R 1 is a hydroxy or amino group; R 2 is H or alkyl and R 3 is COOM or COOR 4 , wherein when R 3 is COOM, M in this COOM moiety is H, an alkali metal ion or one equivalent of an alkaline earth metal ion, and when R 3 is COOR 4 R 4 is C 1 -C 6 -alkyl.
  • Particularly preferred compounds of the above formula (I) are 2-hydroxy-2-sulfonate acetic acid and its salts, in particular its sodium salts, including in particular its disodium salt.
  • the superabsorbent contains compounds of the above formula wherein M is an alkali metal ion or one equivalent of an alkaline earth metal or zinc ion; R 1 is a hydroxy or amino group; R 2 is aryl which is optionally substituted as indicated above, in particular hydroxyphenyl or C 1 -C 4 alkoxyphenyl; and R 3 is a hydrogen atom.
  • Groups 1 H, Li, Na, K, Rb, Cs, Fr
  • 2 Be, Mg, Ca, Sr, Ba, Ra
  • 8 Fe, Ru, Os
  • 9 Co, Rh, Ir
  • 10 Ni, Pd, Pt
  • 12 Zn, Cd, Hg
  • 14 C, Si, Ge, Sn, Pb
  • the international nomenclature body responsible for chemistry correspond to Groups Ia, IIa, IIb, IVa and VIIIb in the numbering used by CAS (Chemical Abstracts Service, 2540 Olentangy River Road, Columbus, OH 43202, USA, www.cas.org).
  • the sulfonic acid derivatives of the above formula can be used in pure form, but optionally also in admixture with the sulfite of the corresponding metal ion and the corresponding sulfinic acid derivative.
  • WO 99/18 067 A1 They are also common commercial products and, for example, in the form of mixtures of the sodium salt of 2-hydroxy-2-sulfinatoacetic acid, the disodium salt of 2-hydroxy-2-sulfonatoacetic acid and sodium bisulfite of L.
  • Brüggemann KG (Salz No 131, 74076 Heilbronn, Germany, www.brueggemann.com) under the names BRÜGGOLIT ® FF6M or
  • phosphonic acid derivative is added to the superabsorber.
  • phosphonic acid itself is to be understood as a phosphonic acid derivative.
  • Phosphonic acid derivatives are compounds of general formula (II) derived from phosphonic acid with the general formula (HP (O) (OH) 2):
  • Examples are monoalkylphosphonic acids and monoalkenylphosphonic acids such as laurylphosphonic acid and stearylphosphonic acid. Further examples are 1 -
  • Preferred phosphonic acid derivatives are those in which R 6 is a diyl radical bearing two phosphonic acid radicals, in particular a 1-amino-1, 1-diyl radical or a 1-hydroxy-1, 1-diyl radical, as in 1-hydroxyalkyl-1, 1 -diyl-bisphosphonic acid, wherein in these compounds alkyl is a Ci-C25 radical, with ethyl being particularly preferred.
  • the most preferred phosphonic acid derivative is (1-hydroxyethane-1,1-diyl) bisphosphonic acid or a salt with a metal M (as defined above) thereof, especially a sodium salt or disodium salt.
  • phosphonic acid derivatives are those in which R 6 is an amino-substituted alkyl radical, in particular an amino-substituted methylene radical, such as in ethylenediaminetetra (methylenephosphonic acid), diethylenetriaminepenta (methylenephosphonic acid) and [nitrilotris (methylene)] tris (phosphonic acid).
  • R 6 is an amino-substituted alkyl radical, in particular an amino-substituted methylene radical, such as in ethylenediaminetetra (methylenephosphonic acid), diethylenetriaminepenta (methylenephosphonic acid) and [nitrilotris (methylene)] tris (phosphonic acid).
  • Such phosphonic acid derivatives are known and are prepared in the usual way, for example by Michaelis-Arbusov reaction, quasi-Mannich reaction of the free phosphonic acid (tautomeric with phosphorous acid) with formaldehyde and oligo- ethyleneamines or by acylation of phosphonic acid with carboxylic anhydrides or nitriles.
  • Their main use is as phosphate substitutes in detergents. Therefore, they are also common commercial products and, for example, under the brand CUB len ® Zschimmer & Schwarz GmbH & Co KG Mohlsdorf, Chemnitztal Found 1, 09217 Burghot, Germany available.
  • the process according to the invention for the preparation of superabsorbents is a process for the aqueous solution polymerization of a monomer mixture comprising: a) at least one ethylenically unsaturated monomer bearing at least one acid group, which is optionally present at least partially as a salt,
  • the monomers a) are preferably water-soluble, ie the solubility in water at 23 ° C. is typically at least 1 g / 100 g of water, preferably at least 5 g / 100 g of water, more preferably at least 25 g / 100 g of water, most preferably at least 35 g / 100 g of water.
  • Suitable monomers a) are, for example, ethylenically unsaturated carboxylic acids or their salts, such as acrylic acid, methacrylic acid, maleic acid or its salts, maleic anhydride and itaconic acid or their salts. Particularly preferred monomers are acrylic acid and methacrylic acid. Very particular preference is given to acrylic acid.
  • Suitable monomers a) are, for example, ethylenically unsaturated sulfonic acids, such as styrenesulfonic acid and 2-acrylamido-2-methylpropanesulfonic acid (AMPS).
  • sulfonic acids such as styrenesulfonic acid and 2-acrylamido-2-methylpropanesulfonic acid (AMPS).
  • AMPS 2-acrylamido-2-methylpropanesulfonic acid
  • a suitable monomer a) is, for example, an acrylic acid purified according to WO 2004/035514 A1 with 99.8460% by weight of acrylic acid, 0.0950% by weight of acetic acid, 0.0332% by weight of water, 0.0203% by weight. %
  • Propionic acid 0.0001% by weight of furfurals, 0.0001% by weight of maleic anhydride, 0.0003% by weight of diacrylic acid and 0.0050% by weight of hydroquinone monomethyl ether.
  • the proportion of acrylic acid and / or salts thereof in the total amount of monomers a) is preferably at least 50 mol%, particularly preferably at least 90 mol%, very particularly preferably at least 95 mol%.
  • the monomer solution preferably contains at most 250 ppm by weight, preferably at most 130 ppm by weight, more preferably at most 70 ppm by weight and preferably at least 10 ppm by weight, more preferably at least 30 ppm by weight, in particular by 50% by weight.
  • ppm, hydroquinone half ethers based in each case on the unneutralized monomer a), where neutralized monomer a), ie a salt of the monomer a) is mathematically taken into account as unneutralized monomer.
  • an ethylenically unsaturated, acid group-carrying monomer having a corresponding content of hydroquinone half-ether can be used to prepare the monomer solution.
  • hydroquinone half ethers 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 radically copolymerized into the polymer chain and functional groups. nelle groups which can form covalent bonds with the acid groups of the monomer a). Furthermore, polyvalent metal salts which can form coordinative bonds with at least two acid groups of the monomer a) are also suitable as crosslinking agents b).
  • Crosslinkers b) are preferably compounds having at least two polymerizable groups which can be incorporated in the polymer network in free-radically polymerized form.
  • Suitable crosslinkers b) are, for example, ethylene glycol dimethacrylate, diethylene glycol diacrylate, polyethylene glycol diacrylate, allyl methacrylate, trimethylolpropane triacrylate, triallylamine, tetraallylammonium chloride, tetraallyloxyethane, as described in EP 530 438 A1, di- and triacrylates, as in EP 547 847 A1, EP 559 476 A1 , EP 632 068 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, contain further ethylenically unsaturated groups, such as in DE 103 31 456 A1 and DE 103 55
  • Preferred crosslinkers b) are pentaerythritol triallyl ether, tetraallyloxyethane, methylene bismethacrylamide, trimethylolpropane triacrylate 15 to 20 times ethoxylated, 15-20 times ethoxylated glycerol triacrylate, polyethylene glycol diacrylate having between 4 and 45 - Ch Ch O units in the molecular chain, trimethylolpropane triacrylate and triallylamine.
  • Very particularly preferred crosslinkers b) are the polyethoxylated and / or propoxylated glycerols esterified with acrylic acid or methacrylic acid to form di- or triacrylates, as described, for example, in WO 2003/104301 A1.
  • Particularly advantageous are di- and / or triacrylates of 3- to 10-fold ethoxylated glycerol.
  • 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 glycerol, in particular the triacrylate of 3-times ethoxylated glycerol.
  • the amount of crosslinker b) is preferably from 0.05 to 1, 5 wt .-%, particularly preferably 0.1 to 1 wt .-%, most preferably 0.3 to 0.6 wt .-%, each based on Monomer a).
  • the centrifuge retention capacity (CRC) decreases and the absorption increases under a pressure of 0.3 psi
  • initiators c) it is possible to use all compounds which generate radicals under the polymerization conditions, for example thermal initiators, redox initiators and / or photoinitiators.
  • Suitable redox initiators are sodium peroxodisulfate / ascorbic acid, hydrogen peroxide / ascorbic acid, sodium peroxodisulfate / sodium bisulfite and hydrogen peroxide / sodium bisulfite.
  • thermal initiators and redox initiators are used, such as sodium peroxodisulfate hydrogen peroxide / ascorbic acid.
  • the sulfonic acid derivative of the formula (I) is preferably used as the reducing component.
  • the initiators are used in conventional amounts.
  • the usual amount of the reducing component of a redox initiator is generally at least 0.00001 wt .-%, preferably at least 0.0001 wt .-% and particularly preferably at least 0.001 wt .-% and generally of at most 0.2 wt. % and preferably at most 0.1 wt .-%, each based on the amount of the monomers a) and d).
  • the amount added thereof is generally at least 0.001% by weight, preferably at least 0.01% by weight and particularly preferably at least 0.03% by weight.
  • the usual amount of the oxidizing component of a redox initiator is generally 0.0001% by weight and more preferably at least 0.001% by weight and generally at most 2% by weight and preferably at most 1.0% by weight, respectively based on the amount of monomers a) and d).
  • the usual amount of the thermal initiators is generally 0.01% by weight and more preferably at least 0.1% by weight and generally at most 2% by weight and preferably at most 1.0% by weight, respectively based on the amount of monomers a) and d).
  • the usual amount of the photoinitiators is generally 0.001% by weight and more preferably at least 0.01% by weight and generally of at most 1.10% by weight and preferably not more than 0.2% by weight, based in each case on the amount of monomers a) and d).
  • Suitable ethylenically unsaturated monomers d) which can be copolymerized with the ethylenically unsaturated monomers having acid groups are acrylamide, methacrylamide, hydroxyethyl acrylate, hydroxyethyl methacrylate, dimethylaminoethyl methacrylate, dimethylaminoethyl acrylate, dimethylaminopropyl acrylate, diethylaminopropyl acrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, maleic acid or its salts and maleic anhydride.
  • water-soluble polymers e it is possible to use 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.
  • 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 wt .-%, most preferably from 50 to 65 wt .-%. It is also possible to use monomer suspensions, ie supersaturated monomer solutions. As the water content increases, the energy expenditure in the subsequent drying tion and with decreasing water content, the heat of polymerization can only be dissipated insufficiently.
  • the monomer solution may be polymerized prior to polymerization by inerting, i. Flow through with an inert gas, preferably nitrogen or carbon dioxide, are freed of dissolved oxygen.
  • an inert gas preferably nitrogen or carbon dioxide
  • the oxygen content of the monomer solution before polymerization is reduced to less than 1 ppm by weight, more preferably less than 0.5 ppm by weight, most preferably less than 0.1 ppm by weight.
  • the monomer mixture may contain other components.
  • further components used in such monomer mixtures include chelating agents in order to keep metal ions in solution or inorganic powders in order to increase the rigidity of the superabsorber in the swollen state, or recycled undersize from a later grinding.
  • all known additives to the monomer mixture can be used. Even if only “solution” is mentioned here in connection with the monomer mixture, this also means the polymerization of a suspension, for example if insoluble constituents are added to the monomer mixture.
  • the acid groups of the polymer gels obtained from the polymerization are usually partially neutralized.
  • the neutralization is preferably carried out at the stage of the monomers, in other words salts of the acid group-carrying monomers or, strictly speaking, a mixture of acid group-carrying monomers and salts of the acid group-carrying monomers ("partially neutralized acid") as component a) in the polymerization
  • This is usually done by mixing the neutralizing agent as an aqueous solution or preferably also as a solid in the monomer mixture intended for the polymerization or preferably in the acid group-carrying monomer or a solution thereof
  • the degree of neutralization is preferably from 25 to 95 mol%, particularly preferably 50 up to 80 mol%, very particularly preferably from 65 to 72 mol%, it being possible to use the customary neutralizing agents, preferably alkali metal hydroxides, alkali metal oxides, alkali metal carbonates or alkali metal bicarbonates and mixtures thereof Alzenes can also be used
  • the polymer gel is 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 can be sprayed, sprinkled or poured on and then thoroughly mixed in. For this purpose, the gel mass obtained can be extruded several times for homogenization.
  • the monomer a) used is a mixture of from 25 to 95 mol%, particularly preferably from 50 to 80 mol%, very particularly preferably from 65 to 75 mol% salt of the acid group carrier Monomers and the remainder used to 100 mol% acid group-carrying monomer.
  • This mixture is, for example, a mixture of sodium acrylate and acrylic acid or a mixture of potassium acrylate and acrylic acid.
  • a neutralizing agent is used for neutralization, the content of iron is generally below 10 ppm by weight, preferably below 2 ppm by weight and most preferably below 1 ppm by weight. Similarly, a low content of chloride and anions of oxygen acids of the chlorine is desired.
  • a suitable neutralizing agent is, for example, the 50% strength by weight sodium hydroxide solution or potassium hydroxide solution, which is usually sold as "membrane grade", even purer and equally suitable, but also more expensive is the 50% by weight conventionally sold as "amalgam grade" or "mercury process".
  • Polymerization in a belt reactor is the same as in the case of polymerization known pole ymerization in the batch operation or in the tubular reactor, as described for example in EP 445 619 A2 and DE 19 846 413 A1, a polymer gel, which must be comminuted in a further process step, for example in a meat grinder, extruder or kneader.
  • WO 2009/027 356 A1 Also known are methods in which the Monomer mixture is applied to a substrate such as a nonwoven web and polymerized, as described for example in WO 02/94 328 A2 and WO 02/94 329 A1.
  • the Sulfonsaurederivat of formula (I) is added in the process according to the invention prior to drying.
  • the addition may be carried out at any time prior to drying, for example sulfonic acid derivative can be added to the monomer solution before polymerization, added during the polymerization and added after polymerisation to the polymer gel obtained.
  • sulfonic acid derivative can be added to the monomer solution before polymerization, added during the polymerization and added after polymerisation to the polymer gel obtained.
  • homogeneous mixing of the sulfonic acid derivative is technically most straightforward, therefore its addition to the monomer solution is preferred. Addition during the polymerization is in particular easily possible if the polymerization takes place in a kneading reactor, since then can also be mixed without a separate process step.
  • the sulfonic acid derivative in the swollen polymer gel it is also possible to mix the sulfonic acid derivative in the swollen polymer gel. If the polymerization is carried out in a kneading reactor, the addition can take place towards the end of the polymerization in the kneading reactor (in the case of continuously conveying kneading reactors corresponding closer to the outlet than at the entry) or in a separate process step between polymerization and drying. In principle, any apparatus which can mix the sulfonic acid derivative sufficiently homogeneously into the gel is suitable for this, above all kneaders, screw mixers and extruders are suitable for this purpose.
  • the sulfonic acid derivative is necessarily added to the monomer mixture.
  • the sulfonic acid derivative of the formula (I) is generally used in an amount of at least 0.001 wt .-%, preferably at least 0.01 wt .-% and particularly preferably at least 0.03 wt .-% and generally of at most 1, 0 wt .-%, preferably at most 0.3 wt .-% and particularly preferably at most 0.2 wt .-%, in each case based on the amount of the monomers a) and d) added.
  • the polymer gel obtained from the aqueous solution polymerization and optionally subsequent neutralization is then preferably dried with a belt dryer until the residual moisture content is preferably 0.5 to 15 wt .-%, particularly preferably 1 to 10 wt .-%, most preferably 2 to 8 wt .-%, is
  • the solids content of the gel before drying is generally from 25 to 90% by weight .-%, preferably from 30 to 80 wt .-%, particularly preferably from 35 to 70 wt .-%, most preferably from 40 to 60 Wt .-%.
  • a fluidized bed dryer or a heatable mixer with mechanical mixing element such as a paddle dryer or a similar dryer can be used with differently shaped mixing tools.
  • the dryer may be operated under nitrogen or other non-oxidizing inert gas, or at least a reduced partial pressure of oxygen, to prevent oxidative yellowing.
  • nitrogen or other non-oxidizing inert gas or at least a reduced partial pressure of oxygen, to prevent oxidative yellowing.
  • sufficient ventilation and removal of the water vapor also leads to an acceptable product.
  • Advantageous in terms of color and product quality is usually the shortest possible drying time.
  • the residual monomer content in the polymer particles also decreases and the last residues of the initiator are destroyed.
  • the dried polymer gel is then 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.
  • Oversized gel lumps which are often not dried in the interior, are rubber-elastic, lead to grinding problems and are preferably separated before grinding, which can easily be achieved by air classification or a sieve ("protective sieve" for the mill) the sieve is to be chosen in view of the mill used so that as possible no interference from oversized, rubbery particles occur.
  • coarse-grained polymer particles are separated from the product. This is carried out by customary classification methods, for example air classification or sieving through a sieve with a mesh size of at most 1000 ⁇ m, preferably at most 900 ⁇ m, more preferably at most 850 ⁇ m and very particularly preferably at most 800 ⁇ m. For example, screens are used with 700 ⁇ , 650 ⁇ or 600 ⁇ mesh size.
  • the separated coarse-grained polymer particles (“oversize") can be fed back to the grinding and screening circuit for cost optimization or further processed separately.
  • SFC permeability
  • fine-grained polymer particles are separated in this classification. This can, if sieved, conveniently by a sieve with a mesh size of at most 300 ⁇ , preferably at most 200 ⁇ , more preferably used at most 150 ⁇ and most preferably not more than 100 ⁇ .
  • the separated fine-grained polymer particles ("undersize” or "fine") can be used in any desired way to optimize the cost of the monomer stream, the polymerized polymer. gel, or the polymerized gel can be recycled before drying the gel.
  • the mean particle size of the polymer particles separated off as product fraction is generally at least 200 ⁇ m, preferably at least 250 ⁇ m, and preferably at least 300 ⁇ m, and generally at most 600 ⁇ m, and more preferably at most 500 ⁇ m.
  • the proportion of particles having a particle size of at least 150 ⁇ m is generally at least 90% by weight, more preferably at least 95% by weight and most preferably at least 98% by weight.
  • the proportion of particles with a particle size of at most 850 ⁇ m is generally at least 90% by weight, preferably at least 95% by weight and more preferably at least 98% by weight.
  • the particle size distribution is predetermined by the choice of process parameters.
  • particulate superabsorbents of the desired particle size are formed directly, so that milling and screening steps can often be omitted.
  • a separate drying step can often be dispensed with.
  • the polymer produced in this way has superabsorbent properties and is referred to as "superabsorbent.” Its CRC is typically comparatively high, while its AUL or SFC is comparatively low. Called base polymer “or" base polymer ".
  • the base polymer is optionally surface postcrosslinked.
  • Suitable postcrosslinkers are compounds which contain groups which can form bonds with at least two functional groups of the superabsorbent particles.
  • Acrylic acid / sodium acrylate-based superabsorbents which are prevalent on the market are suitable surface postcrosslinker compounds which contain groups which can form bonds with at least two carboxylate groups.
  • Preferred postcrosslinkers are amide acetals or carbamates of the general formula (III)
  • R 7 Ci-Ci2 alkyl, C2 -Ci2-hydroxyalkyl, C 2 -C 2 -alkenyl or C 6 -Ci2-aryl, R 8 or OR 12 X '
  • R 9 is hydrogen, Ci-Ci 2 -alkyl, C 2 -C 2 -Hydroxialkyl, C 2 -C 2 -alkenyl or C 6 -C 2 aryl, or X,
  • R 10 Ci-Ci 2 -alkyl, C 2 -C 2 -Hydroxialkyl, C 2 -C 2 -alkenyl or C 6 -C 2 aryl,
  • R 11 is hydrogen, Ci-Ci 2 -alkyl, C 2 -C 2 -Hydroxialkyl, C 2 -C 2 -alkenyl, Ci-Ci2 acyl or
  • R 12 Ci-Ci 2 -alkyl, C 2 -C 2 -Hydroxialkyl, C 2 -C 2 -alkenyl or C 6 -C 2 aryl, and
  • X is a carbonyl oxygen common to the radicals R 8 and R 9 , where R 7 and R 10 and / or R 11 and R 12 may be a bridged C 2 -C 6 alkanediyl, and where the abovementioned radicals R 7 to R 12 are still may have at least one to two free valences and may be connected to these free valencies with at least one suitable base, or polyhydric alcohols, wherein the polyhydric alcohol preferably has a molecular weight of less than 100 g / mol, preferably less than 90 g / mol , particularly preferably less than 80 g / mol, very particularly preferably less than 70 g / mol, per hydroxyl group and no vicinal, geminal, secondary or tertiary hydroxyl groups, and polyhydric alcohols either diols of the general formula (IVa)
  • R 13 is either an unbranched alkylene radical of the formula - (CH 2 ) n -, where n is an integer from 3 to 20, preferably 3 to 12, and both hydroxy groups are terminal, or R 13 is an unbranched, branched or cyclic alkylene radical, or polyols of the general formula (IVb)
  • radicals R 14 , R 15 , R 16 , R 17 independently of one another are hydrogen, hydroxyl, hydroxymethyl, hydroxiethyloxymethyl, 1-hydroxiprop-2-yloximethyl, 2-hydroxipropyloximethyl, methyl, ethyl, n-propyl, isopropyl, n- Butyl, n-pentyl, n-hexyl, 1, 2-dihydroxiethyl, 2-hydroxyethyl, 3-hydroxypropyl or 4-hydroxibutyl and a total of 2, 3, or 4, preferably 2 or 3, Hydroxi phenomenon are present, and not more than one of the radicals R 14 , R 15 , R 16 , or R 17 is hydroxy, or cyclic carbonates of the general formula (V)
  • R 18 , R 19 , R 20 , R 21 , R 22 and R 23 are independently hydrogen, methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl or isobutyl, and n is either 0 or 1 , or bisoxazolines of the general formula (VI)
  • R 24 , R 25 , R 26 , R 27 , R 28 , R 29 , R 30 and R 31 are independently hydrogen, methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl or isobutyl
  • R 32 represents a single bond, a linear, branched or cyclic C 2 -C 12 -alkylene radical, or a polyalkoxydiyl radical which is composed of one to ten ethylene oxide and / or propylene oxide units, such as, for example, polyglycol dicarboxylic acids.
  • Preferred postcrosslinkers of the general formula (III) are 2-oxazolidones, such as 2-oxazolidone and N- (2-hydroxyethyl) -2-oxazolidone, N-methyl-2-oxazolidone, N-acyl-2-oxazolidones, such as N-acetyl -2-oxazolidone, 2-oxotetrahydro-1,3-oxazine, bicyclic Amide acetals such as 5-methyl-1 -aza-4,6-dioxa-bicyclo [3.3.0] octane, 1-aza-4,6-dioxabicyclo [3.3.0] octane and 5-isopropyl-1-aza 4,6-dioxa-bicyclo [3.3.0] octane, bis-2-oxazolidones and poly-2-oxazolidones.
  • 2-oxazolidones such as 2-oxazolidone and N- (2-hydroxye
  • Particularly preferred postcrosslinkers of the general formula (III) are 2-oxazolidone, N-methyl-2-oxazolidone, N- (2-hydroxyethyl) -2-oxazolidone and N-hydroxypropyl-2-oxazolidone.
  • Preferred postcrosslinkers of the general formula (IVa) are 1, 3-propanediol, 1, 5-pentanediol, 1, 6-hexanediol and 1, 7-heptanediol. Further examples of postcrosslinkers of the formula (IVa) are 1,3-butanediol, 1,8-octanediol, 1,9-nonanediol and 1,10-decanediol.
  • the diols are preferably water-soluble, with the diols of the general formula (IVa) at 23 ° C to at least 30 wt .-%, preferably at least 40 wt .-%, particularly preferably at least 50 wt .-%, most preferably at least 60 wt .-%, in water, such as 1, 3-propanediol and 1, 7-heptanediol. Even more preferred are those postcrosslinkers which are liquid at 25 ° C.
  • Preferred secondary crosslinkers of the general formula (IVb) are butane-1, 2,3-triol, butane-1, 2,4-triol, glycerol, trimethylolpropane, trimethylolethane, pentaerythritol, per molecule 1 to 3 times ethoxylated glycerol, trimethylolethane or Trimethylolpropane and per molecule 1 - to 3-fold propoxylated glycerol, trimethylolethane or trimethylolpropane.
  • 2-fold ethoxylated or propoxylated neopentyl glycol Particularly preferred are 2-fold and 3-fold ethoxylated glycerin, neopentyl glycol, 2-methyl-1, 3-propanediol and trimethylolpropane.
  • Preferred polyhydric alcohols (IVa) and (IVb) have at 23 ° C. a viscosity of less than 3000 mPas, preferably less than 1500 mPas, preferably less than 1000 mPas, more preferably less than 500 mPas, very particularly preferably less than 300 mPas, on.
  • Particularly preferred postcrosslinkers of the general formula (V) are ethylene carbonate and propylene carbonate.
  • a particularly preferred postcrosslinker of the general formula (VI) is 2,2'-bis (2-oxazoline).
  • the preferred postcrosslinkers minimize side reactions and subsequent reactions which lead to volatile and thus malodorous compounds.
  • the superabsorbers produced with the preferred postcrosslinkers are therefore odorless even when moistened. It is possible to use a single postcrosslinker from the above selection or any mixtures of different postcrosslinkers.
  • the postcrosslinker is generally used in an amount of at least 0.001% by weight, preferably at least 0.02% by weight, more preferably at least 0.05% by weight, and generally at most 2% by weight, preferably at most 1% by weight, in a particularly preferred form at most 0.3% by weight, for example at most 0.15% by weight or at most 0.095% by weight, in each case based on the mass of the base polymer (eg the one concerned) - fenden sieve fraction).
  • the postcrosslinking is usually carried out by spraying a solution of the postcrosslinker onto the dried base polymer particles. Subsequent to the spraying, the polymer particles coated with postcrosslinker are thermally dried, wherein the postcrosslinking reaction can take place both before and during the drying. If surface postcrosslinkers with polymerizable groups are used, the surface postcrosslinking can also be carried out by free-radically induced polymerization of such groups by means of common free-radical formers or else by means of high-energy radiation such as UV light. This may be done in parallel or instead of using postcrosslinkers that form covalent or ionic bonds to functional groups on the surface of the base polymer particles.
  • the spraying of Nachvernetzeraims is preferably carried out in mixers with moving mixing tools, such as screw mixers, disc, paddle or paddle mixers or mixers with other mixing tools.
  • moving mixing tools such as screw mixers, disc, paddle or paddle mixers or mixers with other mixing tools.
  • vertical mixers particularly preferred are vertical mixers.
  • Suitable mixers are flocking for example as a plow mixer ® Gebr Lödige Maschinenbau GmbH, Elsener Street. 7 - 9, 33102 Paderborn, Germany, or ® as Schugi ® Flexomix mixer, Vrieco-Nauta ® mixer or blender Turbulizer® ® from Hosokawa Micron BV, Gildenstraat 26, 7000 AB Doetinchem, The Netherlands.
  • the applicable spray nozzles are subject to no restriction. Suitable nozzles and atomization systems are described, for example, in the following references: Atomization of Liquids, Expert-Verlag, Vol. 660, series Kunststoff & Meeting, Thomas Richter (2004) and in atomization technology, Springer-Verlag, VDI series, Günter Wozniak (2002 ). Applicable are mono- and polydisperse spray systems. Among the polydisperse systems are single-fluid pressure nozzles (jet or lamella-forming), rotary atomizers, two-component atomizers, ultrasonic atomizers and impact nozzles.
  • the mixture of the liquid phase and the gas phase can take place both internally and externally.
  • the spray pattern of the nozzles is not critical and can take any shape, such as omnidirectional, Flat-jet, wide-angle omnidirectional or circular ring spray pattern. It is advantageous to use a non-oxidizing gas, if two-component atomizers are used, particularly preferably nitrogen, argon or carbon dioxide.
  • the liquid to be sprayed can be supplied under pressure. The division of the liquid to be sprayed can take place in that it is relaxed after reaching a certain minimum speed in the nozzle bore.
  • single-substance nozzles such as, for example, slot nozzles or twist chambers (full-cone nozzles) can also be used for the purpose according to the invention (for example, by Düsen-Schlick GmbH, DE, or by Spraying Systems GmbH, DE).
  • Such nozzles are also described in EP 0 534 228 A1 and EP 1 191 051 A2.
  • the postcrosslinkers are typically used as an aqueous solution. If only water is used as the solvent, the postcrosslinker solution or the base polymer is advantageously added with a surfactant or deagglomerization aid. This improves the wetting behavior and reduces the tendency to clog.
  • anionic, cationic, nonionic and amphoteric surfactants are suitable as deagglomeration aids, but non-ionic and amphoteric surfactants are preferred for skin compatibility reasons.
  • the surfactant may also contain nitrogen.
  • sorbitan monoesters such as sorbitan monococoate and sorbitan monolaurate, or ethoxylated variants thereof, such as polysorbate 20® , are added.
  • deagglomerating agents are the ethoxylated and alko xyl faced derivatives of 2-propylheptanols, which are sold under the brands Lutensol XL ® and Lutensol XP ® (BASF SE, Carl-Bosch-Strckee 38, 67056 Ludwigshafen, Germany).
  • the deagglomerating assistant can be metered separately or added to the postcrosslinker solution.
  • the deagglomerating aid is simply added to the postcrosslinker solution.
  • the amount used of the deagglomerating assistant based on the base polymer is, for example, 0 to 0.1% by weight, preferably 0 to 0.01% by weight, particularly preferably 0 to 0.002% by weight.
  • the deagglomerating aid is metered so that the surface tension of an aqueous extract of the swollen base polymer and / or the swollen postcrosslinked water-absorbing polymer at 23 ° C at least 0.060 N / m, preferably at least 0.062 N / m, more preferably at least 0.065 N / m, and advantageously at most 0.072 N / m.
  • the aqueous postcrosslinker solution may also contain a cosolvent in addition to the at least one postcrosslinker.
  • a cosolvent in addition to the at least one postcrosslinker.
  • the penetration depth of the postcrosslinker can be adjusted in the polymer particles.
  • cosolvents are C1-C6 alcohols, such as methanol, ethanol, n-propanol, isopropanol, n-butanol, sec-butanol, tert-butanol or 2-methyl-1-propanol, C2-C5-diols, such as Ethylene glycol, 1, 2-propylene glycol or 1, 4-butanediol, ketones, such as acetone, or carboxylic acid esters, such as ethyl acetate.
  • a disadvantage of some of these cosolvents is that they have typical odors.
  • the cosolvent itself is ideally not a post-crosslinker under the reaction conditions. However, in the limiting case and depending on residence time and temperature, it may happen that the cosolvent partially contributes to crosslinking. This is the case in particular when the postcrosslinker is relatively inert and therefore can itself form its cosolvent, as for example when using cyclic carbonates of the general formula (V), diols of the general formula (IVa) or polyols of the general formula ( IVb).
  • Such postcrosslinkers can also be used as cosolvents in a mixture with more reactive secondary crosslinkers since the actual postcrosslinking reaction can then be carried out at lower temperatures and / or shorter residence times than in the absence of the more reactive crosslinker. Since co-solvent is used in relatively large amounts and also remains partially in the product, it must not be toxic.
  • the diols of the general formula (IVa), the polyols of the general formula (IVb) and the cyclic carbonates of the general formula (V) are also suitable as cosolvents. They fulfill this function in the presence of a reactive postcrosslinker of the general formula (III) and / or (VI) and / or a di- or triglycidyl compound.
  • preferred cosolvents in the process according to the invention are, in particular, the diols of the general formula (IVa), especially when the hydroxyl groups are hindered sterically by neighboring groups on a reaction.
  • diols are in principle also suitable as postcrosslinkers, they require, however, significantly higher reaction temperatures or optionally higher amounts of use than sterically unhindered diols.
  • Particularly preferred combinations of less reactive postcrosslinker as cosolvent and reactive postcrosslinker are combinations of preferred polyhydric alcohols, diols of general formula (IVa) and polyols of general formula (IVb), with amide acetals or carbamates of general formula (III).
  • Suitable combinations are, for example, 2-oxazolidone / 1, 2-propanediol and N- (2-hydroxyethyl) -2-oxazolidone / 1, 2-propanediol and ethylene glycol diglycidyl ether / 1, 2-propanediol.
  • Very particularly preferred combinations are 2-oxazolidone / 1,3-propanediol and N- (2-hydroxyethyl) -2-oxazolidone / 1,3-propanediol.
  • Further preferred combinations are those with ethylene glycol diglycidyl ether or glycerol or triglycidyl ether with the following solvents, cosolvents or co-crosslinkers: isopropanol, 1,3-propanediol, 1,2-propylene glycol or mixtures thereof.
  • 2-oxazolidone or (2-hydroxyethyl) -2-oxazolidone in the following solvents, cosolvents or co-crosslinkers: isopropanol, 1, 3-propanediol, 1, 2-propylene glycol, ethylene carbonate, propylene carbonate or mixtures thereof.
  • the concentration of the cosolvent in the aqueous postcrosslinker solution is from 15 to 50% by weight, preferably from 15 to 40% by weight, particularly preferably from 20 to 35% by weight, based on the postcrosslinker solution.
  • concentration of the cosolvent in the aqueous postcrosslinker solution is from 15 to 50% by weight, preferably from 15 to 40% by weight, particularly preferably from 20 to 35% by weight, based on the postcrosslinker solution.
  • no cosolvent is used.
  • the post-crosslinker is then used only as a solution in water, optionally with the addition of a deagglomerating auxiliary.
  • the concentration of the at least one postcrosslinker in the aqueous postcrosslinker solution is typically from 1 to 20% by weight, preferably from 1 to 5% by weight, more preferably from 2 to 5% by weight, based on the postcrosslinker solution.
  • the total amount of Nachvernetzerates based on the base polymer is usually from 0.3 to 15 wt .-%, preferably from 2 to 6 wt .-%.
  • the actual surface postcrosslinking by reaction of the surface postcrosslinker with functional groups on the surface of the base polymer particles is usually carried out by heating the base polymer wetted with surface postcrosslinker solution, usually called “drying" (but not to be confused with the above-described drying of the polymer gel from the polymerization)
  • drying can be carried out in the mixer itself, by heating the jacket, by heat exchange surfaces or by blowing warm gases in.
  • Simultaneous addition of the superabsorbent with surface postcrosslinker and drying can take place, for example, in a fluidized bed dryer However, it is usually carried out in a downstream dryer, such as a hopper dryer, a rotary kiln, a paddle or disc dryer or a heatable screw example as Solidair ® or Torusdisc ® -T Rockner from Bepex International LLC, 333 NE Taft Street, Minneapolis, MN 55413, USA, or as a paddle or shovel or also as a fluid bed dryer from Nara Machinery Co., Ltd., branch office Europe, Europaallee 46, 50226 Frechen, Germany available.
  • a downstream dryer such as a hopper dryer, a rotary kiln, a paddle or disc dryer or a heatable screw example as Solidair ® or Torusdisc ® -T Rockner from Bepex International LLC, 333 NE Taft Street, Minneapolis, MN 55413, USA, or as a paddle or shovel or also as
  • the polymer particles can already be heated in the post-crosslinking mixer with steam.
  • the base polymer used may still have a temperature of 10 to 120 ° C from previous process steps, the Nachvernetzerlosung may have a temperature of 0 to 70 ° C.
  • the postcrosslinker solution can be heated to reduce the viscosity.
  • Preferred drying temperatures are in the range 100 to 250 ° C, preferably 120 to 220 ° C, more 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 at least 10 minutes, more preferably at least 20 minutes, most preferably at least 30 minutes, and usually at most 60 minutes.
  • the drying is conducted in such a way that the superabsorber has a residual moisture content of generally at least 0.1% by weight, preferably at least 0.2% by weight and in a particularly preferred form at least 0.5% by weight, and also Generally at most 15% by weight, preferably at most 10% by weight and in a particularly preferred form at most 8% by weight.
  • Postcrosslinking can take place under normal atmospheric conditions. Normal atmospheric conditions means that no technical precautions are taken to reduce the partial pressure of oxidizing gases such as atmospheric oxygen in the apparatus in which the postcrosslinking reaction predominantly takes place (the "postcrosslinking reactor", typically the dryer), but it is preferred Oxidizing gases are substances which have a vapor pressure of at least 1013 mbar at 23 ° C.
  • oxygen, nitrogen oxide and nitrogen dioxide in particular oxygen less than 140 mbar, preferably less than 100 mbar, particularly preferably less than 50 mbar, very particularly preferably less than 10 mbar
  • oxygen less than 140 mbar preferably less than 100 mbar, particularly preferably less than 50 mbar, very particularly preferably less than 10 mbar
  • the total partial pressure of the oxidizing gases is determined by their volume fraction.
  • the proportion of oxidizing gases is preferably less than 14% by volume, preferably less than 10% by volume, particularly preferably less than 5% by volume, very particularly preferably less than 1% by volume.
  • the post-crosslinking can be carried out under reduced pressure, ie at a total pressure of less than 1013 mbar.
  • the total pressure is typically less than 670 mbar, preferably less than 480 mbar, more preferably less than 300 mbar, even more preferably less than 200 mbar. If drying and postcrosslinking are carried out under air with an oxygen content of 20.8% by volume, the oxygen partial pressures corresponding to the abovementioned total pressures are 139 mbar (670 mbar), 100 mbar (480 mbar), 62 mbar (300 mbar) and 42 m mbar (200 mbar), with the respective total pressures in the parentheses.
  • Suitable inert gases at the post-crosslinking temperature and given pressure in the post-crosslinking dryer are gaseous substances which do not oxidize under these conditions to the constituents of the drying polymer particles, for example nitrogen, carbon dioxide, argon, water vapor, nitrogen being preferred.
  • the amount of inert gas is generally from 0.0001 to 10 m 3 , preferably from 0.001 to 5 m 3 , more preferably from 0.005 to 1 m 3 , and most preferably from 0.005 to 0.1 m 3 , based on 1 kg of superabsorbent.
  • the inert gas if it does not contain water vapor, can be injected via nozzles into the postcrosslinking dryer, more preferably the inert gas is already added to the polymer particle stream via nozzles in or just before the mixer by adding surface postcrosslinker to the superabsorber.
  • vapors of cosolvents removed from the dryer can be condensed outside the dryer again and, if necessary, recycled.
  • polyvalent cations are applied to the particle surface in addition to the postcrosslinkers before, during or after the postcrosslinking. This is in principle a further surface postcrosslinking by ionic, noncovalent bonds, but is sometimes also referred to as "complexing” with the metal ions in question or simply as a “coating” with the relevant substances (the “complexing agent").
  • divalent metal cations are, in particular, the divalent cations of metals of groups 2 (in particular Mg, Ca, Sr, Ba), 7 (in particular Mn), 8 (in particular Fe), 9 (in particular Co), 10 (in particular Ni), 1 1 (
  • Examples of usable trivalent metal cations are in particular the trivalent cations of metals of groups 3 including the lanthanides (in particular Sc, Y, La, Ce), 8 (in particular Fe), 11 (in particular Au) and 13 (in particular Al) of the Periodic Table of the Elements
  • tetravalent cations such as formally wholly or partly vinylamine monomers, such as partially or completely hydrolyzed polyvinylamide (so-called "polyvinylamine”), whose amine groups are always partially protonated to ammonium groups, even at very high pH values
  • divalent metal cations are, in particular, the divalent cations of metals of groups 2 (in particular Mg, Ca, Sr, Ba), 7 (in particular M
  • metal salts are suitable which have sufficient solubility in the solvent to be used.
  • metal salts with weakly complexing anions such as chloride, nitrate and sulfate, hydrogen sulfate, carbonate, bicarbonate, nitrate, phosphate, hydrogen phosphate, or dihydrogen phosphate.
  • Preferred are salts of mono- and dicarboxylic acids, hydroxy acids, keto acids and amino acids or basic salts. Examples are acetates, propionates, tartrates, maleates, citrates, lactates, malates and succinates. Also preferred is the use of hydroxides.
  • 2-hydroxycarboxylic acid salts such as citrates and lactates.
  • particularly preferred metal salts are alkali metal and alkaline earth metal aluminates and their hydrates, such as sodium aluminate and its hydrates, aluminum acetate, aluminum propionate, aluminum citrate and aluminum lactate.
  • the cations and salts mentioned can be used in pure form or as a mixture of different cations or salts.
  • the salts of the two and / or trivalent metal cation used may contain further secondary constituents such as unneutralized carboxylic acid and / or alkali metal salts of the neutralized carboxylic acid.
  • Preferred alkali metal salts are those of sodium, potassium and ammonium. They are typically used as an aqueous solution, which is obtained by dissolving the solid salts in water, or is preferably produced directly as such, whereby optionally drying and purification steps are avoided.
  • the hydrates of said salts can be used, which often dissolve faster in water than the anhydrous salts.
  • the amount of metal salt used is generally at least 0.001 wt .-%, preferably at least 0.01 wt .-% and in a particularly preferred form at least 0.1 wt .-%, for example at least 0.4 wt .-% and generally at most 5 wt .-%, preferably at most 2.5 wt .-% and in a particularly preferred form at most 1 wt .-%, for example at most 0.7 wt .-% in each case based on the mass of the base polymer.
  • the salt of the polyvalent metal cation can be used as a solution or suspension.
  • solvents for the metal salts water, alcohols, DMF, DMSO and mixtures of these components can be used. Particularly preferred are water and water / alcohol mixtures such as water / methanol, water / 1, 2-propanediol and water / 1, 3-propanediol.
  • the treatment of the base polymer with solution of a polyvalent cation is carried out in the same way as with surface postcrosslinkers, including the drying step.
  • Surface postcrosslinker and polyvalent cation can be sprayed in a common solution or as separate solutions.
  • the spraying of the metal salt solution onto the superabsorbent particles can be carried out both before and after the surface postcrosslinking.
  • the spraying of the metal salt solution is carried out in the same step by spraying the crosslinker solution, wherein both solutions are sprayed separately successively or simultaneously via two nozzles, or sprayed crosslinker and metal salt solution together via a nozzle can be.
  • a drying step is carried out after the surface postcrosslinking and / or treatment with complexing agent, it is advantageous, but not absolutely necessary, to cool the product after drying.
  • the cooling can be continuous or discontinuous, conveniently the product is continuously conveyed to a dryer downstream cooler.
  • Any apparatus known for removing heat from powdered solids may be used for this purpose, in particular any apparatus mentioned above as a drying apparatus, unless it is supplied with a heating medium but with a cooling medium, such as cooling water, so that over the walls and depending on the construction no heat is also introduced into the superabsorber via the stirring elements or other heat exchange surfaces, but is removed therefrom.
  • coolers in which the product is moved ie cooled mixers, for example blade coolers, disk coolers or paddle coolers.
  • the superabsorbent can also be cooled in the fluidized bed by blowing in a cooled gas such as cold air. The conditions of the cooling are adjusted so that a superabsorber is obtained with the desired temperature for further processing.
  • an average residence time in the condenser of generally at least 1 minute, preferably at least 3 minutes and more preferably at least 5 minutes, and generally at most 6 hours, preferably not more than 2 hours and more preferably not more than 1 hour and the cooling capacity is such that the product obtained has a temperature of generally at least 0 ° C, preferably at least 10 ° C and more preferably at least 20 ° C and generally at most 100 ° C, preferably at most 80 ° C and in a particularly preferred form at most 60 ° C.
  • the surface postcrosslinked superabsorbent is optionally ground and / or sieved in the usual way. Milling is typically not required here, but most often, the setting of the desired particle size distribution of the product, the screening of formed agglomerates or fine grain is appropriate. Agglomerates and fines are either discarded or preferably recycled to the process in a known manner and at a suitable location; Agglomerates after comminution.
  • the particle sizes desired for surface postcrosslinked superabsorbents are the same as for base polymers.
  • Phosphonic acid derivative of the formula (II) is added in the process according to the invention after drying or, if a surface postcrosslinking is carried out after this.
  • any apparatus which can mix the phosphonic acid derivative sufficiently homogeneously into the superabsorber is suitable for this purpose.
  • Especially convenient and therefore preferred is the addition of the phosphonic acid derivative in the cooler.
  • the phosphonic acid derivative of the formula (II) is generally used in an amount of at least 0.01% by weight, preferably at least 0.1% by weight and more preferably at least 0.2% by weight, and generally at most 2.0 wt .-%, preferably at most 1, 0 wt .-% and particularly preferably at most 0.7 wt .-%, in each case based on the total amount of the superabsorber added.
  • the superabsorbents according to the invention are obtainable by the process according to the invention.
  • the superabsorbers according to the invention produced by the process according to the invention are provided with further additives which stabilize against discoloration.
  • all known additives can be used in the manner known to them in each case in the method according to the invention.
  • the superabsorber according to the invention is also mixed with at least one inorganic water-insoluble particulate solid.
  • any inorganic water-insoluble powder is suitable for this purpose.
  • examples are generally solid, chemically inert (ie, non-interfering in the superabsorbent) such as oxides, oxide hydroxides, hydroxides, sulfates, carbonates, zeolites, inorganic pigments, minerals or clays.
  • Examples are sulfates such as magnesium sulfate or barium sulfate, carbonates such as calcium carbonate, magnesium carbonate, zinc carbonate or dolomite, silicates such as calcium silicate or magnesium silicate, carbides such as perlite or silicon carbide, diatomaceous earth or fly ash.
  • sulfates such as magnesium sulfate or barium sulfate
  • carbonates such as calcium carbonate, magnesium carbonate, zinc carbonate or dolomite
  • silicates such as calcium silicate or magnesium silicate
  • carbides such as perlite or silicon carbide, diatomaceous earth or fly ash.
  • Suitable oxides are the metal oxides of Groups 2 to 14 of the Periodic Table of the Elements, including the lanthanides and actinides.
  • particularly suitable oxides are magnesium oxide, calcium oxide, strontium oxide, barium oxide, titanium dioxide, zirconium dioxide, vanadium oxide, chromium oxide, molybdenum oxide, tungsten oxide, manganese dioxide, iron oxide, cobalt oxide, nickel oxide, copper oxide, zinc oxide, boron oxide, aluminum oxide (boehmite and others), silicon dioxide, Tin oxide, lead oxide, lanthanum oxide or cerium oxide.
  • the use of a trivial name for metal oxides should not be a statement about the valence of the metal and the stoichiometry of the oxide.
  • one element forms multiple oxides, generally all are suitable.
  • the oxide is selected according to considerations specific to the individual case, for example by price, toxicity, stability or color.
  • particularly suitable oxides are titanium dioxide, in particular in the anatase or rutile modifications, precipitated or pyrolysis-produced silica.
  • Clays are silicates or aluminosilicates which are usually obtained by mining of natural sediments and occasionally also their further processing. However, some clays are made synthetically.
  • the inorganic water-insoluble solid is particulate, it is in powder form.
  • the average particle size is typically in the range of at least 0.001 ⁇ , preferably at least 0.002 ⁇ , more preferably at least 0.005, and most preferably at least 0.01 ⁇ , and generally at most 500 ⁇ , preferably at most 200 ⁇ , most preferably Form at most 100 ⁇ and in a very particularly preferred form of at most 50 ⁇ .
  • the particles themselves may be aggregates or agglomerates of smaller primary particles.
  • the particle size can be determined by means of sieve analysis, but it is simpler and therefore preferred to determine the particle size by means of laser diffraction technology. These methods are well known and routinely performed on suitable and commercially available equipment.
  • the above-mentioned optional further anti-discoloration stabilizers and the inorganic water-insoluble particulate solid, when added, are generally in amounts of at least 0.0001% by weight, preferably at least 0.001% by weight and more preferably at least 0.025 Wt .-% and generally at most 3 wt .-%, in a preferred form at most 2 wt .-% and in a particularly preferred form at most 0.5 wt .-% added, in each case based on the total weight of the superabsorbent according to the invention.
  • a smaller amount of known stabilizers against discoloration necessary than without alkaline earth metal salt are generally in amounts of at least 0.0001% by weight, preferably at least 0.001% by weight and more preferably at least 0.025 Wt .-% and generally at most 3 wt .-%, in a preferred form at most 2 wt .-% and in a particularly preferred form at most 0.5 wt .-% added, in each case
  • the blending of superabsorbents with the optional anti-discoloration stabilizers and the optional inorganic water-insoluble particulate solid can be accomplished by any known mixing method.
  • Stabilizers against discoloration, if in solid form, and the inorganic water-insoluble particulate solid are mixed in bulk or as a suspension in a solvent or suspending agent, if in dissolved or liquid form, optionally also in solution or liquid form.
  • the stabilizers are blended into the superabsorber as a powder or suspension because of the easier homogeneous distribution. It does not necessarily produce a physical mixture that can be easily separated by mechanical means.
  • the additives may well enter into a firmer connection with the superabsorber, for example as a comparatively firmly adhering surface layer or as particles firmly adhering to the surface of the superabsorber particles.
  • the interference of the additives in the known superabsorber can certainly also be understood and referred to as a "coating".
  • a solvent or suspending agent which is chemically compatible both with the superabsorber and with the additive, that is to say without undesired chemical reactions, is used as the solvent or suspending agent.
  • water or an organic solvent is used, for example an alcohol or polyol, or mixtures thereof.
  • suitable solvents or suspending agents are water, isopropanol / water, 1,3-propanediol / water and propylene glycol / water, the mixing mass ratio preferably being from 20:80 to 40:60.
  • a suspension agent is used for the stabilizers to be used according to the invention or the inorganic particulate solid, water is preferred.
  • a surfactant may be added to the solution or suspension.
  • Optional stabilizers and other additives are generally mixed with the superabsorbent in exactly the same way as the surface postcrosslinking superabsorbent-applied solution or surface postcrosslinker Suspension.
  • the additive can be applied to a (not) postcrosslinked superabsorber (a "base polymer” or “base polymer”) as a constituent of the solution applied to the surface postcrosslinking or one of its components, ie added to the solution of the surface postcrosslinker or one of its components.
  • the superabsorber coated with surface postcrosslinking agent and additives then passes through the further process steps required for surface postcrosslinking, for example a thermally induced reaction of the surface postcrosslinker with the superabsorber.
  • This process is comparatively simple and economical. If the highest stability against discoloration is essential, phosphonic acid derivative as well as optional stabilizers and additives are applied after the surface postcrosslinking in a separate process step, conveniently in the cooler. If phosphonic acid derivative, stabilizers and additives are applied as a solution or suspension, application to the already surface-post-crosslinked superabsorbent in the same mixing apparatus as described for the application of the surface postcrosslinking agent to the base polymer can take place.
  • heating is then carried out just as in the case of surface postcrosslinking in order to dry the superabsorber again.
  • the temperature set in this drying is then generally at most 1 10 ° C, preferably at most 100 ° C, and most preferably at most 90 ° C to avoid undesirable reactions of the additive.
  • the temperature is adjusted so that, in view of the residence time in the drying unit, the desired water content of the superabsorber is achieved.
  • other conventional auxiliaries for example dust binders, anti-caking agents or water for rewetting the superabsorber.
  • the temperature of the polymer particles in this case is between 0 ° C and 190 ° C, preferably less than 160 ° C, more preferably less than 130 ° C, even more preferably less than 100 ° C, and most preferably less than 70 ° C ,
  • the polymer particles are optionally rapidly cooled to temperatures below a possible decomposition temperature of the additive after coating.
  • any known coatings such as film-forming polymers, thermoplastic polymers, dendrimers, polycationic polymers (such as polyvinylamine, polyethylene enimine or polyallylamine), or all of them, may be applied to the surface of the superabsorbent particles, whether postcrosslinked or postcrosslinked, in the manufacturing process in any process step the water-soluble mono- or polyvalent metal salts known to those skilled in the art, such as aluminum sulfate, sodium, potassium, zirconium or iron salts are additionally applied.
  • useful alkali metal salts are sodium and potassium sulfate, sodium and potassium lactates, citrates, sorbates.
  • additives are used and sprayed in the form of dispersions, then they are preferably used as aqueous dispersions, and it is preferably additionally applied a dedusting agent for fixing the additive on the surface of the superabsorbent.
  • the dedusting agent is then added either directly to the dispersion of the inorganic powder additive, optionally it may also be added as a separate solution before, during, or after the inorganic powdery additive has been applied by spraying.
  • the simultaneous spraying postcrosslinking agent, dedusting agent and powdery inorganic additive in postcrosslinking is added separately in the cooler, for example by spraying from above, below or from the side.
  • Particularly suitable dedusting agents which can also serve to fix powdery inorganic additives on the surface of the water-absorbing polymer particles, are polyethylene glycols having a molecular weight of 400 to 20,000 g / mol, polyglycerol, 3 to 100-fold ethoxylated polyols, such as trimethylolpropane, glycerol, sorbitol and neopentyl glycol.
  • Particularly suitable are 7 to 20 times ethoxylated glycerol or trimethylolpropane, such as, for example, polyol TP 70® (Perstorp, SE).
  • polyol TP 70® Perstorp, SE.
  • the latter have the particular advantage that they only insignificantly reduce the surface tension of an aqueous extract of the water-absorbing polymer particles.
  • the superabsorbents according to the invention generally have a centrifuge retention capacity (CRC, measuring method see below) of at least 5 g / g, preferably of at least 10 g / g and in a particularly preferred form of at least 20 g / g. Usually, it is not more than 40 g / g for surface-postcrosslinked superabsorbents, but it is often higher for base polymers.
  • CRC centrifuge retention capacity
  • the superabsorbents according to the invention typically have an absorption under pressure (AUL0.7 psi, method of measurement see below) of at least 10 g / g, preferably at least 14 g / g, preferably at least 18 g / g and very particularly preferably at least 22 g / g and usually not more than 30 g / g.
  • AUL0.7 psi absorption under pressure
  • the L value of the superabsorber (CIE color number) in the non-stored state is typically at least 75, preferably at least 80, particularly preferably at least 85 and at most 100.
  • the a-value of the superabsorbent (CIE color number) in the non-stored state is typically from -2.5 to +2.5, preferably from -2.0 to +2.0, more preferably from -1.5 to +1 ; 5.
  • the b-value of the superabsorbent (CIE color number) in the non-stored state is typically from 0 to 12, preferably from 2 to 1.
  • the superabsorber according to the invention after measurement for the L and a values, has only relatively little deteriorated results compared to the non-stored state, in particular b values of preferably not more than 13, particularly preferably not more than 12, up.
  • a b-value above 12 is critical in feminine hygiene articles and ultrathin diapers; a b-value of more than 15 is already critical in conventional diapers, as this discoloration can be perceived by the consumer in use.
  • a further subject of the present invention are hygiene articles comprising superabsorbers according to the invention, preferably ultrathin diapers, containing an absorbent layer consisting of 50 to 100 wt.%, Preferably 60 to 100
  • Wt .-% preferably 70 to 100 wt .-%, particularly preferably 80 to 100 wt .-%, most preferably 90 to 100 wt .-%, inventive superabsorber, wherein the envelope of the absorbent layer is of course not taken into account.
  • inventive superabsorber preferably 90 to 100 wt .-%, inventive superabsorber, wherein the envelope of the absorbent layer is of course not taken into account.
  • inventive superabsorber wherein the envelope of the absorbent layer is of course not taken into account.
  • inventive superabsorber wherein the envelope of the absorbent layer is of course not taken into account.
  • inventive superabsorber wherein the envelope of the absorbent layer is of course not taken into account.
  • the superabsorbents according to the invention are also very particularly advantageous for the production of laminates and composite structures, as described, for example, in US 2003/0181115 and US 2004/0019342.
  • the superabsorbers according to the invention are also suitable for the preparation of completely analogous fibers described in US 2003/0181115 Structures using UV-crosslinkable hotmelt adhesives, which are sold, for example, as AC-Resin® (BASF SE, Germany).
  • UV-crosslinkable hot-melt adhesives which are sold, for example, as AC-Resin® (BASF SE, Germany).
  • AC-Resin® AC-Resin®
  • UV-crosslinkable hot-melt adhesives have the advantage of being processable at as low as 120 to 140 ° C, so they are better compatible with many thermoplastic substrates.
  • Another significant advantage is that UV-crosslinkable hot melt adhesives are toxicologically very harmless and also cause no exhalations in the toiletries.
  • the combination of the superabsorbents according to the invention with UV-crosslinkable hotmelt adhesives is therefore particularly advantageous.
  • Suitable UV-crosslinkable hot-melt adhesives are described, for example, in EP 0 377 199 A2, EP 0 445 641 A1, US Pat. No. 5,026,806, EP 0 655 465 A1 and EP 0 377 191 A2.
  • the superabsorber according to the invention can also be used in other fields of technology in which liquids, in particular water or aqueous Solutions are absorbed.
  • These areas are for example storage, packaging, transport (as components of packaging material for water or moisture sensitive articles, such as flower transport, as well as protection against mechanical effects); Animal hygiene (in cat litter); Food packaging (transport of fish, fresh meat, absorption of water, blood in fresh fish or meat packaging); Medicine (wound plaster, water-absorbing material for burn dressings or for other weeping wounds), cosmetics (carrier material for pharmaceutical chemicals and medicaments, rheumatism plaster, ultrasound gel, cooling gel, cosmetic thickener, sunscreen); Thickener for oil / water or water / oil emulsions; Textiles (moisture regulation in textiles, shoe inserts, for evaporative cooling, for example in protective clothing, gloves, headbands); chemical-technical applications (as a catalyst for organic reactions, for the immobilization of large functional molecules such as enzymes, as adhesives in agglomer
  • thermoplastic polymers eg for the hydrophilization of multilayer films
  • Production of films and thermoplastic moldings capable of absorbing water eg rainwater and condensation water-storing films for agriculture; Superabsorber-containing films for keeping fruit and vegetables fresh, which are packed in moist films; Superabsorbent polystyrene coextrudates, for example for food packaging such as meat, fish, poultry, fruits and vegetables); or as a carrier substance in active ingredient formulations (pharmaceuticals, crop protection).
  • liquid absorption articles according to the invention differ from those known in that they contain the superabsorber according to the invention.
  • a process has also been found for the preparation of articles for the absorption of liquid, in particular hygiene articles, which is characterized in that at least one superabsorber according to the invention is used in the production of the article in question.
  • methods for producing such articles using superabsorbents are known. test methods
  • the superabsorbent is tested using the test methods described below.
  • the "WSP” standard test methods described below are described in: “Standard Test Methods for the Nonwovens Industry", 2005 edition, co-edited by the Worldwide Strategy Partners EDANA (European Disposables and Nonwovens Association, Avenue Eugene Plasky). 157, 1030 Brussels, Belgium, www.edana.org) and INDA (Association of the Nonwoven Fabrics Industry, 1 100 Crescent Green, Suite 1 15, Cary, North Carolina 27518, USA, www.inda.org). This publication is available from both EDANA and INDA. All measurements described below should be performed at an ambient temperature of 23 ⁇ 2 ° C and a relative humidity of 50 ⁇ 10% unless otherwise specified. The superabsorbent particles are thoroughly mixed before measurement, unless stated otherwise. Centrifuge Retention Capacity (CRC)
  • the centrifuge retention capacity of the superabsorbent is determined according to the standard test method no. WSP 241.5-05 "Centrifuge retention capacity". Absorption under pressure (AUL0.7psi, "Absorbency Under Load of 0.7 psi)
  • the absorption under a pressure of 4826 Pa (0.7 psi) of the superabsorbent is determined analogously to the standard test method no. WSP 242.2-05 "absorption under pressure", but with a weight of 49 g / cm 2 (leads to a pressure of 0.7 psi) instead of a weight of 21 g / cm 2 (leading to a pressure of 0.3 psi) is used.
  • the proportion of extractables of the superabsorbent is determined according to the standard test method no. WSP 270.2-05 "Determination of Extractable Polymer Content by Potentiometry Titration".
  • Moisture content of the superabsorber (residual moisture, water content)
  • the water content of the superabsorbent particles is determined in accordance with the standard test method no. WSP 230.2-05 "Moisture content”.
  • SFC fluid transfer
  • CIE color number (L, a, b)
  • the formula HC60 L-3b, the HC60 becomes Value calculated.
  • the color measurement corresponds to the tristimulus method according to DIN 5033-6.
  • Measurement 1 (initial color): A 9 cm inner diameter plastic dish is filled with superabsorbent particles and then smoothed over the edge with a knife and the CIE color numbers and HC60 value are determined.
  • Measurement 2 (after aging): A 9 cm inner diameter plastic dish is filled with superabsorbent particles and then smoothed over the edge with a knife painted. The dish is then placed open in a controlled at 60 ° C cabinet with a constant relative humidity of 86%. The peel is taken out after 21 days. After cooling to room temperature, the CIE color numbers are determined.
  • the instrument used as a mixer was a ploughshare ® mixer with heating jacket, type M5, Gebr Lödige Maschinenbau GmbH, Elsener Street. 7 - 9, 33102 Paderborn, Germany.
  • the device used as a kneader was a Pflugschar ® kneader with heating jacket, type VT 5R-MK from the same manufacturer.
  • Cublen ® K 2012 is 20 wt .-% aqueous solution of 1 -Hydroxiethan-1, 1 - diphosphonic acid, disodium salt.
  • Cublen ® K 3014 is a 20 wt .-% aqueous solu- strength solution of 1 -Hydroxiethan-1, 1-diphosphonic acid, tetrasodium salt.
  • Cublen ® K60 is a 60 wt .-% aqueous solution of 1 -Hydroxiethan-1, 1-diphosphonic acid.
  • Cublen ® K 4023 is a 26 wt .-% aqueous solution of 1 -Hydroxiethan-1, 1 - diphosphonic acid, tripotassium salt. These substances are available from Zschimmer & Schwarz Mohlsdorf GmbH & Co. KG, Chemnitztalstrasse 1, 09217 Burgroom, Germany. Laromer® ® PO 9044V is the triacrylate of triply ethoxylated glycerol and available from BASF SE, Ludwigshafen, Germany.
  • DAROCUR ® 1173 is 2-hydroxy- 2-methyl-1-phenylpropane-1-one and available from BASF Switzerland AG, Basel, Switzerland.
  • IRGACURE ® 651 is 2,2-dimethoxy-1 -one 2-diphenylethane-1 and also available from BASF Switzerland AG, Basel, Switzerland.
  • the base polymer thus prepared had the properties mentioned in Table 1.
  • Example 1 was repeated except that 3.9 g of an aqueous, 10 wt .-% solution of sodium bisulfite instead of the 0.39 g of the disodium salt of 2-hydroxy-2-sulfonatoacetic acid, dissolved in 7.5 ml of water were added , The proportion of finally separated agglomerates was 15.2 g.
  • Base polymer, surface postcrosslinked polymer and post-treated polymer had the properties mentioned in Table 1.
  • Example 3 (comparison)
  • Example 1 was repeated, except that 3.9 g of an aqueous, 10 wt .-% solution of sodium thiosulfate instead of the 0.39 g of the disodium salt of 2-hydroxy-2-sulfonatoacetic acid, dissolved in 7.5 ml of water were added , The proportion of finally separated agglomerates was 15.0 g.
  • Base polymer, surface postcrosslinked polymer and post-treated polymer had the properties mentioned in Table 1.
  • Example 4 (comparison)
  • Example 1 was repeated except that 0.047 g of ascorbic acid dissolved in 7.5 ml of water was added instead of the 0.39 g of the disodium salt of 2-hydroxy-2-sulfonatoacetic acid dissolved in 7.5 ml of water. The proportion of finally separated agglomerates was 14.0 g.
  • Base polymer, surface-postcrosslinked polymer and post-treated polymer had the properties mentioned in Table 1.
  • Example 5 (comparative) Example 1 An attempt was made to repeat, but using 19.6 g Cublen ® K were 2012 instead of 0.39 g of the disodium salt of 2-hydroxy-2-sulfonatoacetic acid dissolved in 7.5 ml of water was added. The polymerization started very hesitantly. After 16 minutes, the mass in the glass dish was still a viscous slime that could not be worked up further.
  • Example 4 was repeated, except for the aftertreatment of a mixture of 12.5 g acetic acid Cublen ® K 2012, and 1 g of the disodium salt of 2-hydroxy-2-sulfonato, water was used dissolved in 19 ml. The proportion of finally separated agglomerates was 56.8 g.
  • Base polymer, surface-postcrosslinked polymer and post-treated polymer had the properties mentioned in Table 1.
  • Example 1 was repeated, but initially only once instead of three times was gewolft and then the once-wound gel with a mixture of 2.5 g Cublen K 2012 and 20 ml of water was added and then again twice gewolft. Further, post-treatment was not carried out after the surface postcrosslinking. Base polymer and surface postcrosslinked polymer had the properties mentioned in Table 1.
  • Example 8
  • Example 4 was repeated, but initially only once, instead of three times, and then the once-wound gel with 0.39 g of the disodium salt of the 2-
  • Base polymer and surface postcrosslinked polymer had the properties mentioned in Table 1.
  • Example 4 was repeated, but initially only once instead of three times was gewolft and then added the once-wound gel with 19.5 g of an aqueous, 2 wt .-% solution of potassium hydrogen sulfite and then again twice gewolft. The proportion of finally separated agglomerates was 15.2 g.
  • Base polymer and surface postcrosslinked polymer had the properties mentioned in Table 1.
  • Initiator 1 was an aqueous solution containing 5% by weight of the disodium salt of 2-hydroxy-2-sulfonatoacetic acid
  • initiator 2 was a 10% strength by weight solution of sodium peroxodisulfate in deionized water
  • initiator 3 was an aqueous solution containing 2, 5 wt .-% of 2,2'-azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride used.
  • the metering rate of the initiator solution 1 was 0.33 kg / h
  • the metering rate of the initiator solution 2 was 0.27 kg / h
  • the metering rate of the initiator solution 3 was 0.22 kg / h.
  • the superabsorber was obtained as a sieve fraction with particle sizes between 150 ⁇ and 850 ⁇ . Separate surface postcrosslinking was not performed. He had the properties listed in Table 1.
  • the base polymer produced in this way had the properties mentioned in Table 1.
  • the surface postcrosslinking was carried out as in Example 1, except that instead of the mixture of 0.84 g of N- (2-hydroxyethyl) -2-oxazolidinone, 10.8 g of 1,2-propanediol and 25.2 g of water, a mixture of 0.84 g of N- (2-hydroxyethyl) -2-oxazolidinone, 4.8 g of 1,2-propanediol, 12.0 g of 2-propanol, 4.8 g of water and 27.3 g of a 22% by weight aqueous aluminum lactate solution was used and after spraying the temperature instead of 185 ° C to 189 ° C was increased.
  • the sieve fraction of 150-710 ⁇ m was obtained.
  • the surface-postcrosslinked superabsorbents thus fabricated had a SFC of 125 ⁇ 10 -7 cm 3 s / g and beyond those mentioned in Table 1 properties. aftercare
  • Example 12 The after-treatment was carried out as in Example 1 except that 60 and 20 g of water was coated instead ® 12.5 g Cublen K 2012 ® with a mixture of 1, 67 g Cublen K and agglomerates place by means of a sieve of mesh width 850 ⁇ means of a sieve were separated with 710 ⁇ mesh size. The proportion of finally separated agglomerates was 9.3 g.
  • the polymer thus obtained had a SFC of 108 ⁇ 10 "7 cm 3 s / g and beyond those mentioned in Table 1 properties.
  • Example 12 Example 12
  • Example 1 1 was repeated, except that only 2.14 g were used in the preparation of the base polymer instead of 2.75 g Laromer ® PO 9044V. Furthermore, instead of the sieve fraction of 150-710 ⁇ m, the sieve fraction of 150-850 ⁇ m was obtained there.
  • the surface-postcrosslinked superabsorbent thus prepared had a GBP of 56 Darcy and moreover had the properties listed in Table 1.
  • 67 g Cublen ® K 60, and 20 g of water were instead of the mixture of 1, 15.4 g Cublen applied ® K 4023 and agglomerates separated instead by means of a sieve of 710 mesh size ⁇ means of a sieve of 850 mesh size ⁇ .
  • the proportion of finally separated agglomerates was 16.9 g.
  • the polymer thus obtained had a GBP of 48 Darcy and moreover had the properties mentioned in Table 1.

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Abstract

L'invention concerne un superabsorbant pouvant être obtenu à l'aide d'un procédé de fabrication de superabsorbants, par polymérisation d'une solution monomère contenant a) au moins un monomère éthyléniquement insaturé qui se présente sélectivement au moins partiellement sous forme de sel, b) au moins un agent de réticulation, c) au moins un amorceur, d) sélectivement un ou plusieurs monomères éthyléniquement insaturés pouvant être copolymérisés avec les monomères cités en a), et e) sélectivement un ou plusieurs polymères hydrosolubles. Le procédé selon l'invention consiste ensuite à sécher le polymère obtenu, sélectivement à broyer le polymère séché et à tamiser le polymère broyé, sélectivement à soumettre le polymère séché et éventuellement broyé et tamisé à une post-réticulation de surface, au moins un dérivé d'acide sulfonique étant ajouté au mélange monomère et/ou au polymère avant le séchage, et au moins un dérivé d'acide phosphonique étant ajouté au polymère après le séchage ou éventuellement après la post-réticulation de surface. Ledit superabsorbant présente une stabilité améliorée par rapport à la décoloration lors de son stockage à températures élevées ou avec une taux d'humidité élevé dans l'air.
PCT/EP2013/056122 2012-03-30 2013-03-22 Superabsorbant résistant à la décoloration WO2013144027A1 (fr)

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CN201380018616.5A CN104245760A (zh) 2012-03-30 2013-03-22 颜色稳定的超吸收剂

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Cited By (4)

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WO2018029045A1 (fr) * 2016-08-10 2018-02-15 Basf Se Procédé de fabrication de superabsorbants
EP3415550A4 (fr) * 2016-12-13 2019-04-03 LG Chem, Ltd. Polymère superabsorbant et son procédé de préparation
WO2019201669A1 (fr) 2018-04-20 2019-10-24 Basf Se Procédé de production de superabsorbants
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WO2018029045A1 (fr) * 2016-08-10 2018-02-15 Basf Se Procédé de fabrication de superabsorbants
US11325990B2 (en) 2016-08-10 2022-05-10 Basf Se Method for the production of superabsorbers
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US11319246B2 (en) 2017-11-03 2022-05-03 Covestro (Netherlands) B.V. Water-blocking systems including fibers coated with liquid radiation curable SAP compositions
US11731903B2 (en) 2017-11-03 2023-08-22 Covestro (Netherlands) B.V. Water-blocking systems including fibers coated with liquid radiation curable SAP compositions
WO2019201669A1 (fr) 2018-04-20 2019-10-24 Basf Se Procédé de production de superabsorbants
US12083496B2 (en) 2018-04-20 2024-09-10 Basf Se Process for producing superabsorbents

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