DE10249821A1 - A two-stage process for preparation of an absorbing polymer useful for foams, sealing materials, liquid absorbing hygiene articles, plant growth regulators, packaging materials, and floor covering additives - Google Patents

Abstract

A two-stage process for preparation of an absorbing polymer by mixing polymer particles with a liquid, distribution inside the polymer particles, where the polymer particles of the first process are mixed at such a rate that the energy of motion of the individual particles is on average higher than the adhesion energy between individual particles and the polymer particles in the second process are mixed at a slower rate than in the first process is new. A process for preparation of an absorbing polymer involving a first mixing process in which a number of absorbing polymer particles are mixed with a liquid and a second mixing process in which the liquid is distributed inside the polymer particles, where the polymer particles of the first process are mixed at such a rate that the energy of motion of the individual particles is on average higher than the adhesion energy between individual particles and the polymer particles in the second process are mixed at a slower rate than in the first process. Independent claims are included for: (1) an absorbing polymer obtained as above; (2) a composite involving an absorbing polymer and a substrate, (3) A chemical product involving the absorbing polymer; (4) a process for preparing a composite in which an absorbing polymer and a substrate and optionally an adjuvant are brought into contact.

Description

The invention relates to a method for the production of an absorbent polymer structure, one by this Procedure available absorbent polymer structure, an absorbent polymer structure, a composite, a method for producing a composite Composite available from this process, chemical products containing the absorbent Polymer structure or the composite, the use of the absorbent Polymeric structure or composite in chemical products, a aqueous Solution, a method of producing the aqueous solution, an aqueous solution obtainable by the process and the use of the aqueous solution to treat the outside area of an absorbent polymer structure.

Superabsorbents are water-insoluble, cross-linked polymers that are capable of swelling and formation of hydrogels great Amounts of watery Liquids, especially body fluids, preferably urine or blood, to take up and under a certain Hold back pressure. These characteristics find these polymers mainly Use in the incorporation into sanitary articles, such as Baby diapers, incontinence products or sanitary napkins.

In the superabsorbents currently commercially available are essentially cross-linked polyacrylic acids or cross-linked starch-acrylic acid graft polymers, where the carboxyl groups partially with sodium hydroxide solution or potassium hydroxide solution are neutralized.

For aesthetic reasons and from environmental aspects there is an increasing tendency to the sanitary articles getting smaller and thinner to design. To maintain a constant overall retention capacity sanitary ware to ensure, can only meet this requirement by reducing the proportion of large-volume Fluff to be met. This causes the superabsorbent to fall further Tasks related to the transportation and distribution of liquids too, which are called permeability properties summarize.

Permeability means superabsorbent materials the ability, transport liquids added when swollen and distribute in three dimensions. This process is swollen Superabsorbent gel over capillary transport through spaces between the gel particles from. A liquid transport by swollen superabsorbent particles themselves follow the laws the diffusion and is a very slow process in the usage situation of the sanitary ware doesn't matter in the distribution of the liquid. With superabsorbent materials, which do not have capillary transport due to a lack of gel stability can accomplish was made by embedding these materials in a fiber matrix Separation of the particles from each other is avoided while avoiding the gel blocking phenomenon. In new generation diaper constructions is located in the absorber layer little or nothing at all no fiber material to support of fluid transport. The superabsorbers used here must therefore be sufficient high stability in the swollen state so that the swollen gel has another has sufficient amount of capillary spaces through the liquid can be transported.

In order to obtain superabsorbent materials with high gel stability, on the one hand the degree of crosslinking of the polymer can be increased, which inevitably leads to a reduction in the swellability and the retention capacity. An optimized combination of different crosslinkers and comonomers, as in DE 196 46 484 described may improve the permeability properties, but not to a level that allows, for example, the incorporation of a layer, which may consist only of superabsorbers, into a diaper construction.

You can also use post-treatment methods the surface of polymer particles to improve the superabsorbent properties are used. As a surface treatment are, for example, post-crosslinking of the absorbent polymer structure on the surface, bringing the surface into contact with inorganic compounds or the post-crosslinking of the surface in the presence of inorganic Connections known from the prior art.

Describe like this EP-A-0 450 923 . EP-A-0 450 922 . DE-A-35 23 617 . U.S. 5,140,076 and U.S. 4,734,478 the treatment of the surface of absorbent polymers by contacting the surface with inorganic compounds, such as, for example, with finely divided silica, during or after the post-crosslinking of the surface. In addition to an increased absorption rate under pressure, this type of surface treatment also increases the permeability of the absorbent polymers.

U.S. 4,535,098 describes a method for increasing the gel strength of non-post-crosslinked superabsorbers by swelling absorbent polymers in the presence of a colloidally disperse, inorganic compound, such as a silica sol, or by producing an absorbent polymer in the presence of a colloidally disperse, inorganic compound.

DE 198 05 447 discloses a process for the post-crosslinking of polyacrylonitrile hydrolyzates with bifunctional compounds and a simultaneous immobilization of silica in the surface structure of the superabsorbent polymer. The silica was combined with the crosslinking agent in one Water / alcohol mixture brought into contact with the surface. Immobilization of the silica is said to improve absorption under load and reduce gel blocking.

DE 198 575 describes the addition of alkali salts of silica before, during or after the polymerization or for the partial neutralization of the superabsorbent. This surface treatment improves permeability, which is mainly due to the reduced retention of the polymers due to the non-swellable additive.

US 5,147,921 discloses the addition of a silica sol as an inert filler that can be dispersed in the monomer solution to be polymerized.

JP 1994-16822 describes the post-treatment of the surface of absorbent polymers with an inorganic sol. In order to avoid improved processability of the mixture which tends to form agglomerates, an organic solvent component is additionally added. Mono- and dimethyl ethers of diols or diols themselves are mentioned as organic solvent components. After drying, the absorbent polymers should have a higher gel stability, a lower tendency to gel blocking and an improved permeability for water in simple tests without pressure loading of the superabsorbers.

The state of the art describes Process in which inorganic particles are either dry with the superabsorbent are mixed or with the help of large quantities of organic solvents be introduced into the process of post-crosslinking in order to agglomerate to prevent the superabsorbent particles. These procedures point however, has the disadvantage that either large amounts of solvent are handled Need to become, what both from economic as well from ecological establish is undesirable. In addition, superabsorbent polymers tend to mix with large amounts of liquid to agglomeration what the processability within a continuous Manufacturing process can seriously affect. An easy one Mixing with inorganic, fine-particle substances, however, brings Disadvantages such as segregation or dusting with itself. The addition of inorganic additives in aqueous Solutions for Post-crosslinking itself is difficult because of the inorganic particles stop quickly. In addition, inorganic dispersions poor dosage.

Due to the presence of the finely divided, inorganic substances disclosed in the prior art there is an inhomogeneous distribution of the chemical postcrosslinker on the surface of the absorbent polymers and therefore also an inhomogeneous one Crosslinking. This in turn leads to that superabsorbent polymers with an unsatisfactory overall performance especially with regard to retention and permeability become. A homogeneous distribution is in the state of the art described methods for surface treatment at most by the use great Amounts of an aqueous or alcoholic solution containing the chemical crosslinker possible.

In general, the invention is the Task based on the disadvantages arising from the prior art to overcome.

There is also an object of the invention in providing superabsorbent polymers as a combination of properties not only a high absorption capacity under pressure, but also the usually opposite properties a high retention capacity and good permeability unite in order to meet the requirements of modern hygiene articles, especially diapers, incontinence products or sanitary napkins absorbent polymers.

There is also another object of the invention in creating a method by which such absorbent Polymers in a simple, continuous manner with the smallest possible amounts of organic solvent can be represented. This manufacturing process should added inorganic auxiliaries at most in small amounts from remove superabsorbent polymer, that do not adversely affect the polymer properties. The in this method of treating the surface of the absorbent polymer used solution should be able to be handled like a single phase system and dose yourself evenly to let. The coated superabsorbent should be in the course of the process in just minor Scope form agglomerates and should be continuous in a simple manner working annealing step can be supplied.

• – in Kontakt bringen des Aussenbereiches des unbehandelten absorbierenden Polymergebildes (Pu) mit einer wässrigen Lösung enthaltend mindestens einen chemischen Vernetzer und mindestens eine anorganische Verbindung in kolloiddisperser Form;
• – Erhitzen des absorbierenden Polymergebildes, dessen Aussenbereich mit der wässrigen Lösung in Kontakt gebracht wurde, auf eine Temperatur im Bereich von 40 bis 300°C, so dass, vorzugsweise wodurch, der Aussenbereich des absorbierenden Polymergebildes im Vergleich zum Innenbereich stärker vernetzt wird und die anorganischen Verbindung im Aussenbereich des absorbierenden Polymergebildes zumindest teilweise immobilisiert wird.

The above objects are achieved by a method for producing an absorbent polymer structure (Pa) by treating the outer region of an untreated absorbent polymer structure (Pu), comprising the steps:

• - bringing the outer area of the untreated absorbent polymer structure (Pu) into contact with an aqueous solution containing at least one chemical crosslinker and at least one inorganic compound in colloidal form;
• Heating the absorbent polymer structure, the outer region of which has been brought into contact with the aqueous solution, to a temperature in the range from 40 to 300 ° C., so that, preferably thereby, the outer region of the absorbent polymer structure is crosslinked more than the inner region and the inorganic compound is at least partially immobilized in the outer region of the absorbent polymer structure.

Absorbent polymer structures according to the invention (Pa) are fibers, foams or particles, with fibers and particles preferred and particles are particularly preferred.

Preferred absorbent according to the invention Polymer fibers are dimensioned so that they are in or as yarns for textiles and can also be incorporated directly into textiles. It is according to the invention preferred that the absorbent polymer fibers have a length in the range from 1 to 500, preferably 2 to 500 and particularly preferably 5 to 100 mm and a diameter in the range from 1 to 200, preferred 3 to 100 and particularly preferably 5 to 60 denier.

Absorbents particularly preferred according to the invention Polymer particles are dimensioned so that they have an average particle size according to ERT 420.1-99 in the range of 10 to 3000, preferably 20 to 2000 and especially preferably 150 to 850 μm exhibit.

• (α1) 20–99,999 Gew.-%, bevorzugt 55 bis 98,99 Gew.-% und besonders bevorzugt 70 bis 98,79 Gew.-% polymerisierten, ethylenisch ungesättigten, säuregruppenhaltigen Monomeren oder deren Salze oder polymerisierten, ethylenisch ungesättigten, einen protonierten oder quarternierten Stickstoff beinhaltenden Monomeren, oder deren Mischungen, wobei mindestens ethylenisch ungesättigte, säuregruppenhaltige Monomere, vorzugsweise Acrylsäure, beinhaltende Mischungen besonders bevorzugt sind,
• (α2) 0–80 Gew.-%, vorzugsweise 0–44,99 Gew.-% und besonders bevorzugt 0,1–44,89 Gew.-% polymerisierten, monoethylenisch ungesättigten, mit (α1) copolymerisierbaren Monomeren,
• (α3) 0,001–5 Gew.-%, vorzugsweise 0,01–3 Gew.-% und besonders bevorzugt 0,01–2,5 Gew.-% eines oder mehrerer Vernetzer,
• (α4) 0–30 Gew.-%, vorzugsweise 0–5 Gew.-% und besonders bevorzugt 0,1–5 Gew.-% eines wasserlöslichen Polymeren, sowie
• (α5) 0–20 Gew.-%, vorzugsweise 0 bis 10 Gew.-% und besonders bevorzugt 0,1–8 Gew.-% eines oder mehrerer Hilfsmittel basiert, wobei die Summe der Gewichtsmengen (α1) bis (α5) 100 Gew.-% beträgt.

The untreated absorbent polymer structure (Pu) used in the process according to the invention is preferably a polymer structure based on

• (α1) 20-99.999% by weight, preferably 55 to 98.99% by weight and particularly preferably 70 to 98.79% by weight of polymerized, ethylenically unsaturated, acid group-containing monomers or their salts or polymerized, ethylenically unsaturated, one monomers containing protonated or quaternized nitrogen, or mixtures thereof, particular preference being given to mixtures containing at least ethylenically unsaturated monomers containing acid groups, preferably acrylic acid,
• (α2) 0-80% by weight, preferably 0-44.99% by weight and particularly preferably 0.1-44.89% by weight polymerized, monoethylenically unsaturated monomers copolymerizable with (α1),
• (α3) 0.001-5% by weight, preferably 0.01-3% by weight and particularly preferably 0.01-2.5% by weight of one or more crosslinking agents,
• (α4) 0-30% by weight, preferably 0-5% by weight and particularly preferably 0.1-5% by weight of a water-soluble polymer, and
• (α5) 0-20% by weight, preferably 0 to 10% by weight and particularly preferably 0.1-8% by weight, of one or more auxiliaries, the sum of the amounts by weight (α1) to (α5) 100 % By weight.

The monoethylenically unsaturated monomers (α1) containing acid groups can be partially or completely, preferably partially, neutralized. The monoethylenically unsaturated monomers containing acid groups are preferably neutralized to at least 25 mol%, particularly preferably to at least 50 mol% and moreover preferably to 50-80 mol%. The in this context is based on DE 195 29 348 referenced, the disclosure of which is hereby introduced as a reference. Some or all of the neutralization can also be carried out after the polymerization. Neutralization can also be carried out with alkali metal hydroxides, alkaline earth metal hydroxides, ammonia and carbonates and bicarbonates. In addition, any other base is conceivable that forms a water-soluble salt with the acid. Mixed neutralization with different bases is also conceivable. Neutralization with ammonia and alkali metal hydroxides is preferred, particularly preferably with sodium hydroxide and with ammonia.

In the case of a polymer, the free acid groups predominate, so this polymer has an acidic pH having. This acidic water-absorbent polymer can by a polymer with free basic groups, preferably amine groups, in comparison is basic to the acidic polymer, at least partially neutralized become. These polymers are known in the literature as “mixed bed ion exchange Absorbent Polymers "(MBIEA polymers) and are disclosed in WO 99/34843, among others. The revelation WO 99/34843 is hereby introduced as a reference and is therefore considered part of revelation. As a rule, MBIEA polymers constitute a composition represents, on the one hand, basic polymers that are able to form anions exchange, and on the other hand a compared to the basic Polymer acidic polymer that is able to exchange cations, include. The basic polymer has basic groups and is typically obtained by polymerizing monomers; the basic groups or groups that are converted to basic groups can be. Above all, these monomers are those the primary, secondary or tertiary Amines or the corresponding phosphines or at least two of the have the above functional groups. To this group of Monomers belong especially ethylene amine, allylamine, diallylamine, 4-aminobutene, alkyloxycyclines, Vinylformamide, 5-aminopentene, carbodiimide, formaldacin, melamine and the like, and their secondary or tertiary amine derivatives.

The monoethylenically unsaturated monomers (a1) containing acid groups can be partially or completely, preferably partially, neutralized. The monoethylenically unsaturated, acid group-containing monomers are preferably neutralized to at least 25 mol%, particularly preferably to at least 50 mol% and moreover preferably to 50-90 mol%. The neutralization of the monomers (α1) can also be carried out before the polymerization. Neutralization can also be carried out with alkali metal hydroxides, alkaline earth metal hydroxides, ammonia and carbonates and bicarbonates. In addition, any other base is conceivable that forms a water-soluble salt with the acid. Mixed neutralization with different bases is also conceivable. Neutralization with ammonia or with alkali metal hydroxides is preferred, particularly preferably with sodium hydroxide or with ammonia.

Preferred monoethylenically unsaturated, containing acid groups Monomers (α1) are acrylic acid, methacrylic acid, Ethacrylic acid, α-chloroacrylic acid, α-cyanoacrylic acid, β-methylacrylic acid (crotonic acid), α-phenylacrylic acid, β-acryloxypropionic acid, sorbic acid, α-chlorosorbic acid, 2'-methylisocrotonic acid, cinnamic acid, p-chlorocinnamic acid, β-stearyl acid, itaconic acid, citraconic acid Mesaconic acid, glutaconic acid, aconitic acid, maleic acid, fumaric acid, tricarboxyethylene and maleic anhydride, being acrylic acid as well as methacrylic acid especially and acrylic acid about that are also preferred.

In addition to those containing carboxylate groups Monomers are monoethylenically unsaturated monomers containing acid groups (α1) of Another ethylenically unsaturated sulfonic or ethylenically unsaturated phosphonic prefers.

Ethylenically unsaturated sulfonic acid monomers are allylsulfonic acid or aliphatic or aromatic vinyl sulfonic acids or acrylic or methacrylic sulfonic acids prefers. As aliphatic or aromatic vinyl sulfonic acids vinylsulfonic 4-vinylbenzyl, vinyltoluene and stryrenesulfonic acid prefers. As acrylic or methacrylic sulfonic acids are sulfoethyl (meth) acrylate, Sulfopropyl (meth) acrylate, 2-hydroxy-3-methacryloxypropylsulfonic acid and 2-Acrylamido-2-methylpropanesulfonic acid preferred.

Furthermore, ethylenically unsaturated phosphonic acid monomers, like vinylphosphonic acid, allylphosphonic, vinylbenzylphosphonic, (Meth) acrylamidoalkylphosphonsäuren, Acrylamidoalkyldiphosphonic acids, phosponomethylated Vinylamines and (meth) acrylic phosphonic acid derivatives are preferred.

As ethylenically unsaturated, monomers (α1) containing a protonated nitrogen are preferred Dialkylaminoalkyl (meth) acrylates in protonated form, for example Dimethylaminoethyl (meth) acrylate hydrochloride or dimethylaminoethyl (meth) acrylate hydrosulfate, and dialkylaminoalkyl (meth) acrylamides in protonated form, for example Dimethylaminoethyl (meth) acrylamide hydrochloride or dimethylaminoethyl (meth) acrylamide hydrosulfate prefers.

As ethylenically unsaturated, a quaternized nitrogen-containing monomer (α1) are dialkylammonium alkyl (meth) acrylates in quaternized form, for example trimethylammonium ethyl (meth) acrylate methosulfate or dimethylethylammonium ethyl (mefh) acrylate ethosulfate and (meth) acrylamidoalkyl dialkylamines in quaternized form, for example (meth) acrylamidopropyltrimethylammonium chloride and (meth) acrylamidopropyltrimethylammonium sulfate is preferred.

It is preferred according to the invention that component (α1) at least 50% by weight, preferably at least 70% by weight and about that in addition preferably at least 90% by weight on carboxylate groups Monomers. According to the invention, it is particularly preferred that the component (α1) at least 50% by weight, preferably at least 70% by weight acrylic acid consists, preferably at least 20 mol%, particularly preferred is neutralized to at least 50 mol%.

As monoethylenically unsaturated, with (α1) copolymerizable monomers (α2) acrylamides and methacrylamides are preferred.

Possible In addition to acrylamide and methacrylamide, (meth) acrylamides are alkyl-substituted (Meth) acrylamides or aminoalkyl-substituted derivatives of (meth) acrylamide, such as N-methylol (meth) acrylamide, N, N-dimethylamino (meth) acrylamide, Dimethyl (meth) acrylamide or diethyl (meth) acrylamide Possible vinyl amides Examples are N-vinylamides, N-vinylformamides, N-vinyl acetamides, N-vinyl-N-methylacetamides, N-vinyl-N-methylformamide, vinyl pyrrolidone. Among these monomers acrylamide is particularly preferred.

Furthermore, are considered monoethylenic unsaturated, with (α1) copolymerizable monomers (α2) monomers dispersible in water are preferred. As water dispersible Monomers are acrylic acid esters and methacrylic acid esters, such as methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate or butyl (meth) acrylate, and also methyl polyethylene glycol (meth) acrylate, Methyl polyethylene glycol allyl ether, vinyl acetate, styrene and isobutylene prefers.

Crosslinkers (α3) preferred according to the invention are compounds which have at least two ethylenically unsaturated groups within one molecule (crosslinker class I), compounds which have at least two functional groups which react with functional groups of the monomers (α1) or (α2) in a condensation reaction ( = Condensation crosslinker), in an addition reaction or in a ring opening reaction (crosslinker class II), compounds which have at least one ethylenically unsaturated group and at least one functional group which with functional groups of the monomers (α1) or (α2) in a condensation reaction, in can react in an addition reaction or in a ring opening reaction (crosslinker class III), or polyvalent metal cations (crosslinker class IV). The compounds of crosslinker class I are a crosslinking of the polymers by the radical polymerization of the ethylenically unsaturated groups of the crosslinker molecule with the monoethylenically unsaturated monomers ren (α1) or (α2), while in the case of the compounds of crosslinker class II and the polyvalent metal cations of crosslinker class IV, the polymers crosslink by condensation reaction of the functional groups (crosslinker class II) or by electrostatic interaction of the polyvalent metal cation (crosslinker class IV) the functional groups of the monomers (α1) or (α2) is achieved. In the case of the compounds of crosslinker class III, the polymer is accordingly crosslinked both by radical polymerization of the ethylenically unsaturated group and by a condensation reaction between the functional group of the crosslinker and the functional groups of the monomers (α1) or (α2).

Preferred compounds of crosslinker class I are poly (meth) acrylic esters or poly (meth) acrylamides, which, for example, by the reaction of a polyol, such as ethylene glycol, propylene glycol, trimethylolpropane, 1,6-hexanediol, glycerol, pentaerythritol, polyethylene glycol or polypropylene glycol, of an amino alcohol , a polyalkylene polyamine, such as diethylenetriamine or triethylenetetraamine, or an alkoxylated polyol with acrylic acid or methacrylic acid. Further preferred compounds of crosslinker class I are polyvinyl compounds, poly (meth) allyl compounds, (meth) acrylic acid esters of a monovinyl compound or (meth) acrylic acid esters of a mono (meth) allyl compound, preferably the mono (meth) allyl compounds of a polyol or an amino alcohol. In this regard, is on DE 195 43 366 and DE 195 43 368 directed. The disclosures are hereby introduced as a reference and are therefore considered part of the disclosure.

As connections of the network class I cite as an example alkenyldi (meth) acrylates, for example Ethylene glycol di (meth) acrylate, 1,3-propylene glycol di (meth) acrylate, 1,4-butylene glycol di (meth) acrylate, 1,3-butylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1,10-decanediol di (meth) acrylate, 1,12-dodecanediol di (meth) acrylate, 1,18-octadecanediol di (meth) acrylate, cyclopentanediol di (meth) acrylate, Neopentyl glycol di (meth) acrylate, methylene di (meth) acrylate or pentaerythritol di (meth) acrylate, Alkenyldi (meth) acrylamides, for example N-methyldi (meth) acrylamide, N, N'-3-methylbutylidenebis (meth) acrylamide, N, N '- (1,2-di-hydroxyethylene) bis (meth) acrylamide, N, N'-hexamethylene-bis (meth) acrylamide or N, N'-methylenebis (meth) acrylamide, Polyalkoxy di (meth) acrylates, for example diethylene glycol di (meth) acrylate, Triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, Dipropylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate or tetrapropylene glycol di (meth) acrylate, bisphenol-A-di (meth) acrylate, ethoxylated bisphenol A di (meth) acrylate, Benzylidinedi (meth) acrylate, 1,3-di (meth) acryloyloxypropanol-2, hydroquinone di (meth) acrylate, Di (meth) acrylate ester of preferably with 1 to 30 moles of alkylene oxide per hydroxyl group oxyalkylated, preferably ethoxylated trimethylolpropane, Thioethylene glycol di (meth) acrylate, thiopropylene glycol di (meth) acrylate, Thiopolyethylene glycol di (meth) acrylate, thiopolypropylene glycol di (meth) acrylate, Divinyl ethers, for example 1,4-butanediol divinyl ether, divinyl esters, for example divinyl adipate, alkane dienes, for example butadiene or 1,6-hexadiene, divinylbenzene, di (meth) allyl compounds, for example Di (meth) allyl phthalate or di (meth) allyl succinate, homo- and copolymers of di (meth) allyldimethylammonium chloride and homo- and copolymers of diethyl (meth) allylaminnmethyl (meth) acrylate ammonium chloride, vinyl (meth) acrylic compounds, for example vinyl (meth) acrylate, (meth) allyl (meth) acrylic compounds, for example (Meth) allyl (meth) acrylate, with 1 to 30 moles of ethylene oxide per hydroxyl group ethoxylated (meth) allyl (meth) acrylate, di (meth) allyl esters of polycarboxylic acids, for example Di (meth) allyl maleate, di (meth) allyl fumarate, di (meth) allyl succinate or di (meth) allyl terephthalate, compounds with 3 or more ethylenic unsaturated, radical polymerizable groups such as glycerol tri (meth) acrylate, (Meth) acrylate ester of preferably 1 to 30 moles of ethylene oxide per hydroxyl group of oxyethylated glycerol, trimethylolpropane tri (meth) acrylate, Tri (meth) acrylate esters preferably with 1 to 30 moles of alkylene oxide per hydroxyl group oxyalkylated, preferably ethoxylated trimethylolpropane, Trimethacrylamide, (meth) allylidenedi (meth) acrylate, 3-allyloxy-l, 2-propanediol di (meth) acrylate, tri (meth) allylcyanurate, Tri (meth) allyl isocyanurate, pentaerythritol tetra (meth) acrylate, pentaerythritol tri (meth) acrylate, (meth) acrylic acid ester with preferably 1 to 30 moles of ethylene oxide per hydroxyl group oxyethylated pentaerythritol, tris (2-hydroxyethyl) isocyanurate tri (meth) acrylate, Trivinyl trimellitate, tri (meth) allylamine, di (meth) allylalkylamine, for example di (meth) allylmethylamine, tri (meth) allylphosphate tetra (meth) allylethylenediamine, Poly (meth) allyl ester, tetra (meth) allyloxyethane or tetra (meth) allylammonium halide.

As a connection of the network class II are preferred compounds that have at least two functional groups have in a condensation reaction (= condensation crosslinker), in an addition reaction or in a ring opening reaction with the functional Groups of the monomers (α1) or (α2), preferably with acid groups, the monomers (α1), can react. In these functional groups of the compounds of the crosslinking class II is preferably alcohol, amine, aldehyde, glycidyl, Isocyanate, carbonate or Epichloro.

Examples of compounds of crosslinker class II include polyols, for example ethylene glycol, polyethylene glycols such as diethylene glycol, triethylene glycol and tetraethylene glycol, propylene glycol, polypropylene glycols such as dipropylene glycol, tripropylene glycol or tetrapropylene glycol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 2,4-pentanediol, 1,6-hexanediol, 2,5-hexanediol, glycerol, polyglycerol, trimethylolpropane, polyoxypropylene, oxyethylene-oxypropylene block copolymers, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, pentaerythritol, polyvinyl alcohol and sorbitol, amino alcohols, for example ethanolamine, dietha ethanolamine, triethanolamine or propanolamine, polyamine compounds such as ethylenediamine, Diethylentriaamin, triethylenetetramine, tetraethylenepentamine or pentaethylenehexamine, polyglycidyl ether compounds such as ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerol diglycidyl ether, glycerol polyglycidyl ether, Pentareritritpolyglycidylether, propylene glycol polypropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, Hexandiolglycidylether, trimethylolpropane polyglycidyl ether, sorbitol polyglycidyl ether, Phtahlsäurediglycidylester, Adipinsäurediglycidylether, 1, 4-phenylene-bis (2-oxazoline), glycidol, polyisocyanates, preferably diisocyanates such as 2,4-toluenediisocyanate and hexamethylene diisocyanate, polyaziridine compounds such as 2,2-bishydroxymethylbutanol-tris [3- (1-aziridinyl) propionate], 1, 6-hexamethylene diethylene urea and diphenylmethane-bis-4,4'-N, N'-diethylene urea haloepoxides, for example epichlorohydrin and epibromohydrin and α-methylepich lorhydrin, alkylene carbonates such as 1,3-dioxolan-2-one (ethylene carbonate), 4-methyl-1,3-dioxolan-2-one (propylene carbonate), 4,5-dimethyl-1,3-dioxolan-2-one, 4,4-dimethyl-1,3-dioxolan-2-one, 4-ethyl-1,3-dioxolan-2-one, 4-hydroxymethyl-1,3-dioxolan-2-one, 1,3-dioxane 2-one, 4-methyl-1,3-dioxan-2-one, 4,6-dimethyl-1,3-dioxan-2-one, 1,3-dioxolan-2-one, poly-l, 3- dioxolan-2-one, polyquaternary amines such as condensation products of dimethylamines and epichlorohydrin. Other compounds of crosslinker class II are polyoxazolines such as 1,2-ethylene bisoxazoline, crosslinkers with silane groups such as γ-glycidoxypropyltrimethoxysilane and γ-aminopropyltrimethoxysilane, oxazolidinones such as 2-oxazolidinone, bis- and poly-2-oxazolidinones and diglycol silicates.

As class III compounds hydroxyl- or amino group-containing esters of (meth) acrylic acid, such as for example 2-hydroxyethyl (meth) acrylate, and hydroxyl or amino group-containing (meth) acrylamides, or mono (meth) allyl compounds preferred by diols.

The polyvalent metal cations of crosslinker class IV are preferably derived from mono- or polyvalent cations, the monovalent in particular from alkali metals such as potassium, sodium, lithium, lithium being preferred. Preferred divalent cations are derived from zinc, beryllium, alkaline earth metals, such as magnesium, calcium, strontium, magnesium being preferred. Other higher-value cations which can be used according to the invention are cations of aluminum, iron, chromium, manganese, titanium, zirconium and other transition metals, and also double salts of such cations or mixtures of the salts mentioned. Aluminum salts and alums and their different hydrates such as, for. B. AlCl ₃ × 6H ₂ O, NaAl (SO ₄ ) ₂ × 12 H ₂ O, KAl (SO ₄ ) ₂ × 12H ₂ O or Al ₂ (SO ₄ ) ₃ × 14-18H ₂ O.

Al ₂ (SO ₄ ) ₃ and its hydrates are particularly preferably used as crosslinking agents of crosslinking class IV.

Preferred untreated, absorbent Polymer structures (Pu) are polymer structures that are crosslinked by the following crosslinker classes or by crosslinkers of the following combinations crosslinker classes are networked: I, II, III, IV, I II, I III, I IV, I II III, I II IV, I III IV, II III IV, II IV or III IV. The above combinations of crosslinking classes represent each a preferred embodiment of crosslinkers of a polymer.

Further preferred embodiments the untreated, absorbent polymer structures (Pu) are polymer structures, by any of the aforementioned crosslinkers Networking classes I are networked. Among these are water-soluble crosslinkers prefers. In this context, N, N'-methylenebisacrylamide, polyethylene glycol di (meth) acrylates, Triallylmethylammonium chloride, tetraallylammonium chloride and with 9 moles of ethylene oxide per mole of acrylic acid Allylnonaethylenglykolacrylat prepared particularly preferred.

As water-soluble polymers (α4) can in the absorbent according to the invention, untreated polymer structures (Pu) water-soluble polymers, such as partially or fully saponified polyvinyl alcohol, polyvinyl pyrrolidone, starch or Starch derivatives, Polyglycols or polyacrylic acid contain, preferably be polymerized. The molecular weight this polymer is not critical as long as it is water soluble. Preferred water soluble Polymers are starch or starch derivatives or polyvinyl alcohol. The water-soluble polymers, preferably Synthetic ones like polyvinyl alcohol can also be used as a graft base for the serve to polymerize monomers.

As auxiliaries (α5) in the process according to the invention absorbent, untreated polymer structures (Pu) used preferably surface active agents Agents, odor control agents, fillers or antioxidants.

It is special according to the invention preferred that the untreated absorbent polymer structure (Pu) at least 50% by weight, preferably at least 75% by weight and beyond preferably based at least 90% by weight on acrylic acid, which is preferred at least 20 mol%, particularly preferably at least 50 mol% is neutralized.

The untreated, absorbent polymer structure (Pu) can be produced from the aforementioned monomers and crosslinkers by various polymerization methods. In this context, for example, bulk polymerization, which preferably takes place in kneading reactors such as extruders, solution polymerization, spray polymerization, inverse emulsion polymerization and inverse suspension polymerization. The solution polymerization is preferably carried out in water as the solvent. The solution polymerization can be carried out continuously or batchwise. A wide spectrum is from the state of the art To take a variety of possibilities with regard to reaction conditions such as temperatures, type and amount of initiators and the reaction solution. Typical processes are described in the following patents: US 4,286,082 . DE 27 06 135 . US 4,076,663 . DE 35 03 458 . DE 40 20 780 . DE 42 44 548 . DE 43 23 001 . DE 43 33 056 . DE 44 18 818 , The disclosures are hereby introduced as a reference and are therefore considered part of the disclosure.

Another way of making the untreated, absorbent polymer structure (Pu) consists in it; first uncrosslinked, especially linear polymers, preferably on radical ones To produce ways from the aforementioned monoethylenically unsaturated monomers (α1) or (α2) and then with cross-linking reagents (α3), preferably to implement those of classes II and IV. This variant is preferred used when the polymer structures are first used in shaping processes, for example to fibers, foils or other flat structures, such as fabrics, Knitted, spun or nonwovens processed and in this form to be networked.

The polymerization is carried out as usual triggered an initiator. All can be used as initiators for initiating the polymerization initiators which form free radicals under the polymerization conditions are used, which is usually be used in the manufacture of superabsorbents. Also one Initiation of polymerization by exposure to electron beams on the polymerizable, aqueous Mixing is possible. However, the polymerization can also take place in the absence of initiators of the type mentioned above by exposure to high-energy radiation are triggered in the presence of photoinitiators. polymerization can in a solution monomers according to the invention solved or be dispersed. Everyone comes as initiators Compounds which decompose into radicals and are known to the person skilled in the art. This includes in particular peroxides, hydroperoxides, hydrogen peroxide, Persulfates, azo compounds and the so-called redox catalysts. The use of water-soluble catalysts is preferred. In some make it is advantageous to use mixtures of different polymerization initiators to use. Among these mixtures are those of hydrogen peroxide and sodium or potassium peroxodisulfate preferred, which is in every conceivable ratio can be used. Suitable organic peroxides are preferably acetylacetone peroxide, Methyl ethyl ketone peroxide, t-butylbydroperoxide, cumene hydroperoxide, t-amyl perpivalate, t-butyl perpivalate, t-butyl perneohexonate, t-butyl isobutyrate, t-butyl per-2-ethylhexenoate, t-butyl perisononanoate, t-butyl permaleate, t-butyl perbenzoate, t-butyl 3,5,5-tri-methylhexanoate and amyl perneodecanoate. Furthermore, as polymerization initiators preferred: azo compounds, such as 2,2'-azobis- (2-amidinopropane) dihydrochloride, Azo-bis-amidinopropane dihydrochloride, 2,2'-azobis (N, N-dimethylene) isobutyramidine dihydrochloride, 2- (carbamoylazo) isobutyronitrile and 4,4'-azobis (4-cyanovaleric acid). The the compounds mentioned are used in customary amounts, preferably in a range from 0.01 to 5, preferably from 0.1 up to 2 mol%, each based on the amount of the polymerized Monomers.

The redox catalysts contain at least one of the above-mentioned per compounds as the oxidic component and preferably ascorbic acid, glucose, sorbose, manose, ammonium or alkali metal hydrogen sulfite, sulfate, sulfate, thiosulfate, hyposulfite or sulfide, metal salts such as iron II as the reducing component -ions or silver ions or sodium hydroxymethyl sulfoxylate. Ascorbic acid or sodium pyrosulfite is preferably used as the reducing component of the redox catalyst. Based on the amount of monomers used in the polymerization, 1 × 10 ^-5 to 1 mol% of the reducing component of the redox catalyst and 1 × 10 ^-5 to 5 mol% of the oxidizing component of the redox catalyst are used. Instead of, or in addition to, the oxidizing component of the redox catalyst, one or more, preferably water-soluble, azo compounds can be used.

If you go through the polymerization Exposure to high-energy radiation is usually used so-called photoinitiators as initiators. It can be for example so-called α-splitters, H-abstracting systems or also azides. Examples of such Initiators are benzophenone derivatives such as Michler's ketone, phenanthrene derivatives, fluorene derivatives, anthraquinone derivatives, Thioxanone derivatives, coumarin derivatives, benzoin ethers and their derivatives, Azo compounds such as the radical formers mentioned above, substituted Hexaarylbisimidazole or acylphosphine oxides. Examples of azides are: 2- (N, N-dimethylamino) ethyl 4-azidocinnamate, 2- (N, N-dimethylamino) ethyl 4-azidonaphthyl ketone, 2- (N, N-dimethylamino) ethyl 4-azidobenzoate, 5-azido-lnaphthyl-2 '- (N, N-dimethylamino) ethyl sulfone, N- (4-sulfonyl azidophenyl) maleimide, N-acetyl-4-sulfonyl azidoaniline, 4-sulfonylazidoaniline, 4-azidoaniline, 4-azidophenacyl bromide, p-azidobenzoic acid, 2,6-bis (p-azidobenzylidene) cyclohexanone and 2,6-bis (p-azidobenzylidene) -4-methylcyclohexanone. The photoinitiators are, if used, usually in amounts of 0.01 to 5 wt .-%, based on the monomers to be polymerized applied.

A redox system is preferred according to the invention consisting of hydrogen peroxide, sodium peroxodisulfate and ascorbic acid. According to the invention, it is generally azo compounds as initiators preferred, with azo-bis-amidinopropane dihydrochloride being particularly preferred is.

Usually the polymerization initiated with the initiators in a temperature range of 30 to 90 ° C.

The polymer gel is dried up to a water content of 0.5 to 25% by weight preferably from 1 to 10% by weight at temperatures which are usually in the range from 100 to 200.degree.

• (A) die maximale Aufnahme von 0,9 Gew.-%er NaCl-Lösung gemäß ERT 440.1-99 liegt in einem Bereich von mindestens 10 bis 1000, bevorzugt von 15 bis 500 und besonders bevorzugt von 20 bis 300 g/g,
• (B) der mit 0,9 Gew.-%er wässriger NaCl-Lösung extrahierbare Anteil gemäß ERT 470.1-99 beträgt weniger als 30, bevorzugt weniger als 20 und besonders bevorzugt weniger als 10 Gew.-%, bezogen auf das unbehandelte, absorbierende Polymergebilde,
• (C) die Schüttdichte gemäß ERT 460.1-99 liegt im Bereich von 300 bis 1000, bevorzugt 310 bis 800 und besonders bevorzugt 320 bis 700 g/l,
• (D) der pH-Wert gemäß ERT 400.1-99 von 1 g des unbehandelten, absorbierenden Polymergebildes (Pu) in 1 l Wasser liegt im Bereich von 4 bis 10, bevorzugt von 5 bis 9 und besonders bevorzugt von 5,5 bis 7,5,
• (E) der CRC-Wert nach ERT 441.1-99 liegt im Bereich von 10 bis 100, bevorzugt 15 bis 80 und besonders bevorzugt 20 bis 60 g/g.

In a preferred embodiment, the untreated absorbent polymer structure (Pu) used in the method according to the invention exhibits at least one of the following properties (ERT = EDANA Recommended Test):

• (A) the maximum absorption of 0.9% by weight of NaCl solution according to ERT 440.1-99 is in a range from at least 10 to 1000, preferably from 15 to 500 and particularly preferably from 20 to 300 g / g,
• (B) the extractable content according to ERT 470.1-99 with 0.9% by weight of aqueous NaCl solution is less than 30, preferably less than 20 and particularly preferably less than 10% by weight, based on the untreated, absorbent polymer structure,
• (C) the bulk density according to ERT 460.1-99 is in the range from 300 to 1000, preferably 310 to 800 and particularly preferably 320 to 700 g / l,
• (D) the pH according to ERT 400.1-99 of 1 g of the untreated, absorbent polymer structure (Pu) in 1 l of water is in the range from 4 to 10, preferably from 5 to 9 and particularly preferably from 5.5 to 7, 5,
• (E) the CRC value according to ERT 441.1-99 is in the range from 10 to 100, preferably 15 to 80 and particularly preferably 20 to 60 g / g.

Derived from the above properties resulting combinations of properties of two or more of these properties each represent preferred embodiments of the invention Procedure.

Furthermore, as embodiments according to the invention particularly preferred. are procedures in which the untreated absorbent Polymer structures (Pu) as letters or combinations of letters below shown properties or combinations of properties shows: A, B, C, D, E, AB, AC, AD, AE, ABC, ABD, ABE, ACD, ACE, ADE, ABCD, ABCE, ABDE, ACDE, ABCDE.

Bringing the untreated, Absorbent polymer structure (Pu) with the aqueous solution takes place in the method according to the invention preferably by mixing the aqueous solution well. with the untreated absorbent polymer structure (Pu). The aqueous solution is preferably essentially free of organic solvents, especially free of polyhydric alcohols and polyalkylene glycol ethers, particularly preferably free of diethylene glycol monomethyl ether and 1,3-butanediol. The chemical crosslinker can do this from the start in the watery solution containing the inorganic compound in colloidal form be included. However, it is also possible that the chemical crosslinker and the colloidally disperse, inorganic compound separately, preferably however at the same time as the untreated, absorbent polymer structure (Pu) are brought into contact. In this case, preferably two separate solutions, one of which is the chemical crosslinker and the other the inorganic Contains compound in colloidally disperse form, preferably simultaneously mixed with the untreated absorbent polymer structure (Pu), but with a homogeneous distribution of the chemical crosslinker and the inorganic compound in colloidal dispersed form guaranteed have to be.

Suitable mixing units for spreading the components are e.g. B. the Patterson-Kelley mixer, DRAIS turbulence mixer, Lödige, Ruberg mixer, Screw mixer, plate mixer and fluidized bed mixer as well as continuously working vertical mixer in which the polymer structure by means of rotating knife is mixed in rapid frequency (Schugi mixer).

The untreated, absorbent polymer structure is in the inventive method preferably with at most 20% by weight, particularly preferably at most 15% by weight, in addition preferably with at most 10% by weight and most preferably with a maximum of 5% by weight of water on the weight of the untreated absorbent polymer structure (Pu) brought into contact.

It is in the method according to the invention further preferred that at least 30 wt .-%; particularly preferred at least 60% by weight and above in addition, preferably at least 90% by weight of the colloidally disperse inorganic Compound a particle size in the range from 1 to 100, preferably from 5 to 80 and more preferably from 6 up to 50 nm.

The inorganic compound is according to the inventive method preferably in an amount of 0.001 to 10% by weight, particularly preferably from 0.01 to 5% by weight and above also preferably from 0.05 to 1.5% by weight, based on the untreated absorbent polymer structure (Pu), with the untreated, absorbent Polymer structures (Pu) brought into contact.

As an inorganic compound, all water-insoluble, inorganic compounds are used, from which stable, Colloidally disperse, preferably single-phase, aqueous solutions can be obtained at 20 ° C and normal pressure above a period of at least 6h, preferably at least 24h and especially preferably no phase separation for at least 72 hours up to 6 months, such as settling a solid, inorganic precipitate, demonstrate.

A colloidally disperse solution is preferably understood to mean a solution which contains particles with a particle diameter in a range from 100-1000 Å (10 ^-4 to 10 ^-5 cm). These solutions have the property of scattering a light beam sent through the solution in all directions, so that the The path of the light beam through the colloid-disperse solution can be followed (Tyndall effect, see also Hollemann · Wiberg, Textbook of inorganic chemistry, 91st – 100th edition, de Gruyter-Verlag, page 765).

As a particularly preferred colloidal dispersion Inorganic compounds containing polysilicic acid are used in the process according to the invention Particles used. A colloidally disperse solution containing such particles (Silica sol) can, for example, by careful acidification due to hydrolysis alkaline reacting sodium silicate solutions can be obtained or but by loosening molecular silica in water and any subsequent stabilization of the resulting colloidally dispersed solution. The exact preparation of such silica sols is known to the person skilled in the art and is, for example, in Jander · Blasius, “Textbook the analytical and preparative inorganic chemistry "S. Hirzel Verlag, Stuttgart.

Under chemical. Networkers who in the method according to the invention in the watery solution are included, compounds are preferably understood that have at least two functional groups with functional Groups of a polymer in a condensation reaction (= condensation crosslinker), can react in an addition reaction or in a ring opening reaction or but polyvalent metal cations by means of electrostatic interaction between the polyvalent metal cation and the functional groups of a polymer enable crosslinking of the polymer. As a chemical crosslinker for Post-crosslinking the outside of the untreated, absorbent Polymer structure (Pu) - also called "postcrosslinker" - are in the method according to the invention preferred those in connection with the crosslinkers (α3) as crosslinkers of classes II and IV.

Among these connections are as Postcrosslinker particularly preferably condensation crosslinker such as Diethylene glycol, triethylene glycol, polyethylene glycol, glycerin, Polyglycerol, propylene glycol, diethanolamine, triethanolamine, polyoxypropylene, Oxyethylene-oxypropylene block copolymers, sorbitan fatty acid esters, polyoxyethylene, Trimethylolpropane, pentaerytrite, polyvinyl alcohol; Sorbitol, 1,3-dioxoan-2-one (Ethylene carbonate), 4-methyl-1,3-dioxolan-2-one (Propylene carbonate), 4,5-dimethyl-1,3-dioxolan-2-one, 4,4-dimethyl-1,3-dioxolan-2-one, 4-ethyl-1,3-dioxolan-2-one, 4-hydroxymethyl-1,3-dioxolan-2-one, 1,3-dioxan-2-one, 4-methyl-1,3-dioxan-2-one, 4,6-dimethyl-1,3-dioxan-2-one, 1,3-dioxo1an-2-one, Poly-1,3-dioxolan-2-one.

Ethylene carbonate is particularly preferred used as a post-crosslinker.

The postcrosslinker is used in the process according to the invention preferably in an amount in the range of 0.01 to 30, especially preferably 0.1 to 20 and above in addition, preferably from 0.3 to 5% by weight, based on the untreated absorbent polymer structures (Pu) used.

After the chemical crosslinker and the watery solution containing the inorganic compound with the untreated absorbent Polymer structures (Pu) have been brought into contact in the process according to the invention the post-crosslinking reaction by heating the absorbent polymer structure Temperatures in the range from 40 to 300 ° C, preferably from 80 to 250 ° C and particularly preferably from 150 to 220 ° C. The optimal duration of the reheating can be for the individual types of crosslinkers and colloidally disperse inorganic compounds easily determined become. It is limited if the desired property profile of the Superabsorbers due to heat damage destroyed again becomes. The thermal treatment can be carried out in conventional dryers or ovens, examples are rotary kilns, Fluid bed dryer, plate dryer, paddle dryer or infrared dryer called.

It is preferred according to the invention that due to the thermal treatment the exterior of the absorbent Polymer structure stronger is networked as the interior and that through the thermal At least treat the inorganic compound in the outside area is partially immobilized. Furthermore, in this context preferred that the radius of the outer region is smaller than that triple the radius of the interior.

In another embodiment of the method according to the invention, the outer region of the absorbent polymer structures is brought into contact with a compound containing Al ³⁺ ions before or after, preferably after, contacting the aqueous solution containing the chemical crosslinking agent and the inorganic compound in colloidally disperse form brought. It is preferred that the compound containing Al ³⁺ ions in an amount in a range from 0.01 to 30 wt .-%, particularly preferably in an amount in a range from 0.1 to 20 wt .-% and moreover, preferably in an amount in a range from 0.3 to 5% by weight, based in each case on the weight of the absorbent polymer structures, are brought into contact with the polymer structures.

The contacting of the outer region of the absorbent polymer structure with the Al ³⁺ ion-containing compound is preferably carried out by mixing the absorbent polymer structure (Pa) with the compound under dry conditions or by having the absorbent polymer structure (Pa) with a Fluid comprising a solvent, preferably water, water-miscible organic solvents such as methanol or ethanol or mixtures of at least two of them, and the compound containing Al ³⁺ ions are brought into contact, the contacting preferably by spraying the polymer particles with the fluid and mixing takes place. In this context, it is further preferred that contacting the absorbent polymer structures (Pa) ent with the fluid holding the compound containing Al ³⁺ ions is carried out in a two-stage process. The two-stage process comprises a first mixing process, in which a multiplicity of absorbent polymer structures are mixed with the fluid, and a second mixing process, in which the fluid is homogenized inside the polymer particles, the polymer particles being mixed at a rate in the first mixing process, that the kinetic energy of the individual polymer particles is on average greater than the adhesive energy between the individual polymer particles, and the polymer particles in the second mixing process are mixed at a lower speed than in the first mixing process.

By treating the absorbent polymer structures (Pa) with the fluid containing the Al ³⁺ ion-containing compound by the two-step process described above, absorbent polymer structures with improved absorption properties can be obtained.

The compound containing Al ³⁺ ions is preferably in each case without consideration of water of crystallization in an amount in a range from 0.1 to 50% by weight, particularly preferably in an amount in a range from 1 to 30% by weight based on the total weight of the fluid contained in the fluid. It is further preferred that the fluid in an amount in a range from 0.01 to 15 wt .-%, particularly preferably in an amount in a range from 0.05 to 6 wt .-%, each based on the weight of the absorbent polymer structure (Pa), is brought into contact with the absorbent polymer structure (Pa).

Compounds containing Al ³⁺ ions are preferably AlCl ₃ × 6H ₂ O, NaAl (SO ₄ ) ₂ × 12 H ₂ O, KAl (SO ₄ ) ₂ × 12H ₂ O or Al ₂ (SO ₄ ) × 14-18H ₂ O.

The present invention relates to furthermore absorbent polymer structures (Pa), which are characterized by the above described inventive method available are.

• (β1) bei einer CRC < 26 g/g eine SFC von mindestens 80·10^–7, bevorzugt von mindestens 100 10^–7 und besonders bevorzugt von mindestens 120·10^–7 cm³·s·g^–1,
• (β2) bei einer CRC nach ERT 441.1-99 im Bereich ≥ 26 bis < 27 g/g eine SFC von mindestens 70·10^–7, bevorzugt von mindestens 90·10^–7 und besonders bevorzugt von mindestens 110·10^–7 cm³·s·g^–1,
• (β3) bei einer CRC nach ERT 441.1-99 im Bereich ≥ 27 bis < 28 g/g eine SFC von mindestens 60·10^–7, bevorzugt von mindestens 8010^–7 und besonders bevorzugt von mindestens 100 10^–7 cm³·s·g^–1,
• (β4) bei einer CRC nach ERT 441.1-99- im Bereich ≥ 28 bis < 29 g/g eine SFC von mindestens 45·10^–7, bevorzugt von mindestens 6510^–7 und besonders bevorzugt von mindestens 85·10^–7 cm³·s·g^–1,
• (β5) bei einer CRC nach ERT 441.1-99 im Bereich ≥ 29 bis < 30 eine SFC von mindestens 30·10^–7, bevorzugt von mindestens 50·10^–7 und besonders bevorzugt von mindestens 70·10^–7 cm³·s·g^–1,
• (β6) bei einer CRC nach ERT 441.1-99 im Bereich ≥ 30 bis < 31 eine SFC von mindestens 20·10^–7, bevorzugt von mindestens 40·10^–7 und besonders bevorzugt von mindestens 60·10^–7 cm³·s·g^–1,
• (β7) bei einer CRC nach ERT 441.1-99 im Bereich ≥ 31 eine SFC von mindestens 10·10^–7, bevorzugt von mindestens 20·10^–7 und besonders bevorzugt von mindestens 30·10^–7 cm³·s·g^–1.

In addition, the invention relates to an absorbent polymer structure (Pa) comprising an inner region and an outer region surrounding the inner region, the outer region being more cross-linked than the inner region, an inorganic compound being at least partially immobilized in the outer region and the absorbent polymer structure (Pa) being at least one of the has the following properties:

• (β1) at a CRC <26 g / g, an SFC of at least 80 · 10 ⁻⁷ , preferably of at least 100 10 ⁻⁷ and particularly preferably of at least 120 · 10 ⁻⁷ cm ³ · s · g ^-1 ,
• (β2) with a CRC according to ERT 441.1-99 in the range ≥ 26 to <27 g / g, an SFC of at least 70 · 10 ^-7 , preferably of at least 90 · 10 ^-7 and particularly preferably of at least 110 · 10 ^-7 cm ³ · s · g ^-1 ,
• (β3) in the case of a CRC according to ERT 441.1-99 in the range ≥ 27 to <28 g / g, an SFC of at least 60 · 10 ⁻⁷ , preferably of at least 8010 ⁻⁷ and particularly preferably of at least 100 10 ⁻⁷ cm ³ · s · G ^-1 ,
• (β4) with a CRC according to ERT 441.1-99- in the range ≥ 28 to <29 g / g, an SFC of at least 45 · 10 ⁻⁷ , preferably of at least 6510 ^–7 and particularly preferably of at least 85 · 10 ^–7 cm ³ · S · g ^-1 ,
• (β5) for a CRC according to ERT 441.1-99 in the range ≥ 29 to <30, an SFC of at least 30 · 10 ^-7 , preferably of at least 50 · 10 ^-7 and particularly preferably of at least 70 · 10 ^-7 cm ³ · s · G ^-1 ,
• (β6) with a CRC according to ERT 441.1-99 in the range ≥ 30 to <31, an SFC of at least 20 · 10 ^-7 , preferably of at least 40 · 10 ^-7 and particularly preferably of at least 60 · 10 ^-7 cm ³ · s · G ^-1 ,
• (β7) with a CRC according to ERT 441.1-99 in the range ≥ 31 an SFC of at least 10 · 10 ^–7 , preferably of at least 20 · 10 ^–7 and particularly preferably of at least 30 · 10 ^–7 cm ³ · s · g ^{- 1st}

Derived from the above properties resulting combinations of properties of two or more of these properties each represent preferred embodiments of the invention absorbent polymer structure (Pa). Furthermore, as embodiments according to the invention an absorbent polymer structure (Pa) is particularly preferred, which the following as letters or letter combinations shown properties or combinations of properties shows: β1, β2, β3, β4, β5, β6, β7, with β2, β3, β4, β5 and β6 particularly are preferred.

It is further preferred according to the invention that the absorbent polymer structure (Pa) has an absorbance against pressure (AAP) according to ERT 442.1-99 at a pressure of 50 g / cm ² of at least 18 g / g, particularly preferably at least 20 g / g and above furthermore particularly preferably has at least 22 g / g.

It is with the absorbent according to the invention Polymer structures further preferred that the radius of the outer region is less than twice the radius of the interior.

The inorganic compound that in the outer region of the absorbent polymer structure according to the invention (Pa) is at least partially immobilized, any water-insoluble, be an inorganic compound from which stable, colloidally disperse aqueous solutions are obtained can be.

A particularly preferred inorganic Connection in the outer area of the absorbent according to the invention Polymer structure (Pa) is at least partially immobilized a condensate of polysilicic acids.

It is further preferred that the aforementioned features of the absorbent according to the invention Polymer structures (Pa) also for those obtainable by the inventive method mentioned at the outset absorbent polymer structures (Pa) apply.

According to an embodiment of the invention of the method according to the invention and the absorbent according to the invention Polymer structures (Pa), it is preferred that the specified only with a lower limit Values of features according to the invention have an upper limit that is 20 times, preferably 10 times and particularly preferably 5 times the most preferred value the lower limit.

The invention further relates to a composite, including a previously defined absorbent Polymer structure (Pa) and a substrate. The polymer structures according to the invention are preferably (Pa) and the substrate firmly connected. As substrates are films made of polymers, such as polyethylene, polypropylene or polyamide, metals, fleeces, fluff tissues, fabrics, natural or synthetic fibers, or other foams preferred.

According to the invention, as a composite, sealing materials Cables, absorbent cores and diapers and hygiene articles containing them prefers.

The sealing materials are preferably water-absorbent films, in which the absorbent polymer structure (Pa) is incorporated as a substrate in a polymer matrix or fiber matrix. This is preferably done in that the absorbent polymer structure (Pa) is mixed with a polymer (Pm) forming the polymer or fiber matrix and then connected by optionally thermal treatment. In the event that the absorbent structure is used as a fiber, yarns can be obtained therefrom which are spun with further fibers made of another material as the substrate and then connected to one another for example by weaving or knitting or directly, ie without being spun with further fibers to be connected. Typical procedures for this are in H. Savano et al., International Wire & Cabel Symposium Proceedings 40, 333 to 338 (1991); M. Fukuma et al., International Wire & Cabel Symposium Proceedings, 36, 350 to 355 (1987) and in US 4,703,132 described. These disclosures are hereby introduced as a reference and are therefore considered part of the disclosure.

In the embodiment in which the composite is a cable, the absorbent polymer structure (Pa) as particles used directly, preferably under the insulation of the cable become. In another embodiment of the cable, the absorbent polymer structure (Pa) can be in the form of swellable, tensile yarns are used. According to one another embodiment of the cable, the absorbent polymer structure (Pa) can be swellable Film are used. Yet another embodiment of the cable, the absorbent polymer structure (Pa) can be used as a moisture absorbent Core can be used in the middle of the cable. The substrate forms in the case of the cable all components of the cable that are not absorbent Contain polymer structures (Pa). This includes those in the cable built-in conductors, such as electrical conductors or optical fibers, optical or electrical insulation and components of the cable that ensure the mechanical strength of the cable, such as braids, fabrics or knitted fabrics made of tensile materials such as plastics and insulation made of rubber or other materials that destroy the Prevent the outer skin of the cable.

If the composite is an absorbent core, the absorbent polymer structure (Pa) is incorporated into a substrate. This substrate is preferably fiber materials. Fibrous materials that can be used in the present invention include naturally occurring fibers (modified or unmodified) as well as synthetic fibers. Examples of suitable unmodified and modified naturally occurring fibers include cotton, esparto grass, sugar cane, awn hair, flax, silk, wool, pulp, chemically modified pulp, jute, rayon, ethyl cellulose and cellulose acetate. Suitable synthetic fibers can be made from polyvinyl chloride, polyvinyl fluoride, polytetrafluoroethylene, polyvinylidene chloride, polyacrylate such as Orion ^®, polyvinyl acetate, polyethylvinyl acetate, non-soluble or soluble polyvinyl alcohol, polyolefins such as polyethylene (e.g., PULPEX ^®) and polypropylenes, polyamides, such Ny1on, polyesters such as DACRON ^® or Kodel ^® , polyurethanes, polystyrene and the like can be produced. The fibers used can include only naturally occurring fibers, only synthetic fibers, or any compatible combination of naturally occurring and synthetic fibers.

The in the. Fibers used in the present invention can be hydrophilic or hydrophobic, or they can be a combination of hydrophilic and hydrophobic fibers. The term "hydrophilic" as used herein describes fibers or surfaces of fibers that are wettable by aqueous fluids (e.g. aqueous body fluids) deposited on these fibers. Hydrophilicity and wettability are typically defined in terms of the contact angle and surface tension of the liquids and solids involved. This is discussed in detail in a publication by the American Chemical Society entitled "Contact Angle, Wettability and Adhesion", published by Robert F. Gould (Copyright 1964). A fiber or the surface of a fiber is wetted by a liquid (i.e. it is hydrophilic) if either the contact angle between the liquid and the fiber or its surface is less than 90 °, or if the liquid tends to spontaneously over the Distribute surface, where both conditions are usually present simultaneously. Conversely, a fiber or the surface of a fiber is considered to be hydrophobic if the contact angle is greater than 90 ° and the liquid does not spontaneously spread on the surface of the fiber.

Fibers preferred according to the invention are hydrophilic fibers. Suitable hydrophilic fibers include cellulose fibers, modified cellulose fibers, rayon, polyester fibers such as polyethylene terephthalate (e.g. DACRON ^® ), hydrophilic nylon (HYDROFIL ^® ) and the like. Suitable hydrophilic fibers can also be obtained by hydrophilizing hydrophobic fibers, such as surfactant-treated or silica-treated thermoplastic fibers based, for example, on polyolefins such as polyethylene or polypropylene or on polyacrylates, polyamides, polystyrenes, polyurethanes and the like. For reasons of availability and cost, cellulose fibers, particularly cellulose fibers, are preferred for use in the present invention. Further preferred hydrophilic fibers for use in the present invention are chemically stiffened cellulose fibers. The term “chemically stripped cellulose fibers” here means cellulose fibers which are stiffened by means of chemical agents in order to increase the steepness of the fibers under both dry and aqueous conditions. Such agents can be chemical stiffening agents which, for example, cover and / or impregnate the fibers However, they can also be those chemical stiffening agents which cause stiffening by changing the chemical structure of the fibers, for example caused by the crosslinking of polymer chains, polymer stiffening agents which can cover or impregnate the cellulose fibers include: cationic starches which are nitrogen containing groups (eg, amino groups) such as they, NJ, USA are available from the National Starch and Chemical Corp., Bridgewater, latexes, wet strength resins such as polyamide epichlorohydrin resin (eg, Kymene ^® 557H, Hercules, Inc., Wilmington, Delaware, USA ) , Polyacrylamide resins, as described, for example, in US 3,556,932 describes commercially available polyacrylamides such as Parez ^® 631 NZ American Cyanamid Co., Stanford, CT, USA, urea formaldehydes and melamine-formaldehyde resins. Fibers that have been stiffened in individual forms by crosslink bonds (that is, the individual stiffened fibers as well as the processes for their manufacture) are described, for example, in US 3,224,926 . US 3,440,135 . US 3,932,209 as in US 4,035,147 , Preferred crosslinking agents are glutaraldehyde, glyoxal, formaldehyde, glyoxalic acid, oxydisuccinic acid and citric acid. The stiffened cellulose fibers obtained by crosslinking or coating, impregnation or crosslinking can be twisted or crimped, preferably the fibers are twisted and additionally crimped.

In addition to the fiber materials mentioned above, the core can also contain thermoplastic materials. During melting, at least a portion of this thermoplastic material, typically caused by the capillary gradients, travels between the fibers to the intersections of the fibers. These crossings become connection points for the thermoplastic material. When the element is cooled, the thermoplastic material solidifies at these junctions to form junctions that hold the matrix or fabric of the fibers together in each of the respective layers. The thermoplastic materials can be in various forms, such as particles, fibers or combinations of particles and fibers. These materials can be prepared from a variety of thermoplastic polymers selected from polyolefins such as polyethylene (e.g., PULPEX ^®) and polypropylene, polyesters, copolyesters, polyvinyl acetates, Polyethylvinylacetaten, polyvinyl chlorides, polyvinylidene chlorides, polyacrylates, polyamides, copolyamides, polystyrenes, polyurethanes and copolymers of the foregoing materials, such as vinyl chloride / vinyl acetate and the like. For cores, preferably fibrous materials consisting predominantly of cellulose come into consideration as the substrate.

In another embodiment of the core comprises this in addition to the substrate and the absorbent Polymer structures (Pa) other powdery substances, such as odor-binding substances such as cyclodextrins, zeolites, inorganic or organic salts and the like Materials.

In one embodiment of the absorbent Cores is the absorbent polymer structure (Pa) in an amount in Range from 10 to 90, preferably from 20 to 80 and particularly preferred from 40 to 70% by weight, based on the core, incorporated. In a embodiment of the core is the absorbent polymer structure (Pa) as particles incorporated into the core. The absorbent polymer structures can (Pa) homogeneously distributed in the fiber materials, they can be layered the concentration must be introduced between the fiber material the absorbent polymer structure (Pa) can be inside the fiber material have a gradient. In another embodiment of the core is the absorbent polymer structure (Pa) as fiber in incorporated the core.

Optionally, several different ones can also be used absorbent polymer particles, which differ for example in the suction speed, permeability, the storage capacity, absorption against pressure, grain distribution or chemical Differentiate composition, be used simultaneously. These different Polymer particles can mixed with each other or introduced to be placed locally differentiated in the core. Such a differentiated Placement can be in the direction of the thickness of the core or the length or Width of the core.

The core can be produced by conventional methods known to the person skilled in the art, such as those generally described by the person skilled in the art under drumforming with the aid of shaped wheels, pockets and product forms and the like dosing devices for the raw materials. In addition, modern, established processes such as the so-called airlaid process (e.g. EP 850 615 . US 4,640,810 ) with all forms of dosing, depositing the fibers and strengthening such as hydrogen bonding (e.g. DE 197 50 890 ), Thermobonding, latex bonding (e.g. EP 850 615 ) and hybrid bonding, the so-called wetlaid process (e.g. WO 99/49905), carding, meltblown, spunblown processes and similar processes for producing superabsorbent non-wovens (as defined by EDANA, Brussels) In combinations of these processes, methods for producing the cores which are customary with and among one another. The production of laminates in the broadest sense as well as of extruded and coextruded, wet and dry and subsequently solidified structures can be considered as further processes.

In another embodiment of the absorbent core comprises this in addition to the substrate and the absorbent polymer structure (Pa) incorporated into the substrate, which together serve as a storage layer for the body fluids, an absorption layer, preferably for the quick absorption and distribution of the liquid serves in the core. The recording layer can be directly above the Storage layer may be arranged, however, it is also possible that the receiving layer by a preferably liquid-stable intermediate layer is separated from the storage layer. This intermediate layer serves then primarily as a support substrate for the Recording layer and the storage layer. Preferred materials for this intermediate layer are polyester spunbonded fabrics, or nonwovens made of polypropylene, polyethylene or nylon.

In one embodiment of the core according to the invention the receiving layer is free of the absorbent polymer. The recording layer can be of any suitable size and doesn't have to worry about the entire length or width of the storage layer. The recording layer can, for example, be in the form of a strip or stain his. The entire recording layer is preferably hydrophilic, however it can also have hydrophobic components. The recording layer can be a woven material, a non-woven material or another suitable type of material. Preferably the Recording layer on hydrophobic polyethylene terephthalate fibers (PET fibers), chemical stiffened cellulose fibers or from mixtures of these fibers. Further suitable materials are polypropylene, polyethylene, nylon or biological fibers. If the receiving layer comprises a nonwoven material, so it can be made by a variety of different processes become. These include wet laying, airflow application, application in the melt, training as spunbond, carding (this includes thermal joining, joining with solvents or joining with the melt spinning process). The latter processes (training as spunbond and carding) are preferred, if desired align the fibers in the receiving layer as it is in such Processes is easier to align the fibers in a single direction. A particularly preferred material for the recording layer is a PET spunbond.

In the embodiment in which the composite is a diaper, the constituents of the diaper, which differ from the absorbent polymer structure (Pa), constitute the substrate of the composite. In a preferred embodiment, the diaper contains a previously described core. In this case, the constituent parts of the diaper, which are different from the core, constitute the substrate of the composite. In general, a composite used as a diaper comprises a water-impermeable lower layer, a water-permeable, preferably hydrophobic, upper layer and a layer containing the absorbent polymer structure (Pa), between the lower layer and the upper layer is arranged. This layer containing the absorbent polymer structure (Pa) is preferably a previously described core. The lower layer can have all materials known to the person skilled in the art, with polyethylene or polypropylene being preferred. The top layer can likewise contain all suitable materials known to the person skilled in the art, polyester, polyolefins, viscose and the like being preferred which result in a layer which is so porous that sufficient liquid passage of the top layer is ensured. In this regard, the revelation in US 5,061,295 . US Re. 26,151 . US 3,592,194 . US 3,489,148 such as US 3,860,003 directed. These disclosures are hereby introduced as a reference and are therefore considered part of the disclosure.

The invention further relates to a method for producing a composite, wherein an inventive absorbent Polymer structures and a substrate and, if necessary, a suitable auxiliary be brought into contact with each other. The contact is done preferably by wetlaid and airlaid processes, compacting, Extrude and mix.

The invention also relates to a Composite that can be obtained by the above method.

The invention further relates to chemical Products, especially foams, Moldings, Fibers, foils, films, cables, sealing materials, liquid absorbing Toiletries, carriers for plant or fungal growth regulators or crop protection agents, additions for building materials, Packaging materials or soil additives that absorb the inventive Include polymeric structures (Pa) or the substrate described above.

In addition, the invention relates to the use of the absorbent polymer structure (Pa) according to the invention or the substrate described above in chemical products, in particular in foams, moldings, fibers, films, films, cables, sealing materials, liquid-absorbent hygiene articles, carriers for agents which regulate plant or fungal growth or crop protection agents , Additives for building materials, packaging materials or floor additives.

When used as carriers for plant or fungal growth regulators or crop protection agents, it is preferred that the plant or fungal growth regulating Agents or crop protection agents via a controlled by the carrier Period can be submitted The invention further relates to an aqueous solution containing at least a chemical crosslinker and at least one inorganic compound in colloidal form, the chemical crosslinker and the inorganic compound those chemical crosslinkers or inorganic Connections correspond to those already described in connection with the above method according to the invention for the production of absorbent polymeric structures (Pa).

The chemical crosslinker is in the aqueous according to the invention solution preferably in one. Amount of 5 to 70 wt .-%, particularly preferred from 20 to 60% by weight and above also preferably from 30 to 50 wt .-%, based on the amount of Water, in the watery solution in front.

The inorganic compound lies in the aqueous according to the invention solution preferably in an amount of 1 to 40% by weight, particularly preferably from 1.5 to 35% by weight and above in addition, preferably from 2.5 to 32% by weight, based on the amount of Water, in the watery solution in front.

The present invention relates to also a method for producing this aqueous solution, wherein an aqueous solution containing at least one inorganic compound in colloidal form is mixed with at least one chemical crosslinker. With this method according to the invention can the chemical crosslinker as such or in the form of a aqueous solution with the watery solution containing the inorganic compound in colloidal form be mixed.

The invention also relates to a aqueous Solution, which is obtainable by the above procedure.

The invention further relates to the use of an aqueous solution containing at least one chemical crosslinker and at least an inorganic compound in colloidal form or use an aqueous Solution, obtainable by the above process for the preparation of an aqueous solution, to treat the exterior of an untreated absorbent Polymer structure (Pu). The treatment already takes place in the initially in connection with the method for treatment according to the invention the outside of an untreated absorbent polymer structure (Pu) outlined way. The untreated absorbent polymer structure (Pu) corresponds to that untreated absorbent polymer structure (Pu), which is also already in connection with the method according to the invention for treating the outside of an untreated absorbent polymer structure (Pu) has been described.

• (γ1) Saline Flow Conductivity (SFC),
• (γ2) Centrifugation Retention Capacity (CRC) oder
• (γ3) Absorbency against Pressure (AAP).

Finally, the invention relates to the use of an aqueous solution containing at least one chemical crosslinking agent and at least one inorganic compound in colloidally disperse form, or to the use of an aqueous solution which is obtainable by the above process for preparing an aqueous solution for adjusting at least one of the following properties in one untreated absorbent polymer structures (Pu):

• (γ1) Saline Flow Conductivity (SFC),
• (γ2) Centrifugation Retention Capacity (CRC) or
• (γ3) Absorbency against Pressure (AAP).

Derived from the above properties resulting combinations of properties of two or more of these properties each represent preferred forms of use according to the invention the inventive aqueous solution represents. Furthermore as according to the invention embodiments use of the aqueous solution to adjust the following is particularly preferred Properties or combinations of properties: γ1, γ2; γ3, γ1γ2, γ1γ3, γ2γ3, γ1γ2γ3.

The invention is now based on limiting examples closer explained.

MANUFACTURE OF THE UNTREATED ABSORBENT POLYMERS (PU)

Powder A

A monomer solution consisting of 280 g of acrylic acid, 70 mol% of which was neutralized with sodium hydroxide solution, 466.8 g of water, 1.4 g of polyethylene glycol 300 diacrylate and 1.68 g of allyloxypolyethylene glycol acrylic acid ester is freed from the dissolved oxygen by flushing with nitrogen and dissolved the start temperature cooled from 4 ° C. After the start temperature had been reached, the initiator solution (0.1 g of 2,2'-azobis-2-amidinepropane dihydrochloride in 10 g of H ₂ O, 0.3 g of sodium peroxydisulfate in 10 g of H ₂ O, 0.07 g of 30% ge Hydrogen peroxide solution in 1 g of H ₂ O and 0.015 g of ascorbic acid in 2 g of H ₂ O. After the final temperature had reached about 100 ° C., the resulting gel was crushed and dried at 150 ° C. for 90 minutes Lymerisat was roughly crushed, ground and sieved onto a powder with a particle size of 150 to 850 μm.

Powder A has a retention capacity of 28.8 g / g.

Powder B

A monomer solution consisting of 280 g of acrylic acid, 70% of which was neutralized with sodium hydroxide solution, 467.6 g of water, 0.98 g of polyethylene glycol 300 diacrylate and 1.26 g of allyloxypolyethylene glycol acrylic acid ester is freed from the dissolved oxygen by flushing with nitrogen and dissolved the start temperature cooled from 4 ° C. After the start temperature had been reached, the initiator solution (0.1 g of 2,2'-azobis-2-amidinepropane dihydrochloride in 10 g of H ₂ O, 0.3 g of sodium peroxydisulfate in 10 g of H ₂ O, 0.07 g of 30% ge Hydrogen peroxide solution in 1 g of H ₂ O and 0.015 g of ascorbic acid in 2 g of H ₂ O. After the final temperature had reached about 100 ° C., the resulting gel was comminuted and dried at 150 ° C. for 90 minutes roughly crushed, ground and sieved to a powder with a particle size of 150 to 850 μm.

The powder R has a retention capacity of 31.2 g / g.

Powder C

A monomer solution consisting of 280 g of acrylic acid, 70 mol% of which was neutralized with sodium hydroxide solution, 468.6 g of water, 0.42 g of polyethylene glycol 300 diacrylate and 0.84 g of allyloxypolyethylene glycol acrylic acid ester is freed from the dissolved oxygen by flushing with nitrogen and dissolved the start temperature cooled from 4 ° C. After the start temperature had been reached, the initiator solution (0.1 g of 2,2'-azobis-2-amidinepropane dihydrochloride in 10 g of H ₂ O, 0.3 g of sodium peroxydisulfate in 10 g of H ₂ O, 0.07 g of 30% ge Hydrogen peroxide solution in 1 g of H ₂ O and 0.015 g of ascorbic acid in 2 g of H ₂ O. After the final temperature had reached about 100 ° C., the resulting gel was comminuted and dried at 150 ° C. for 90 minutes roughly crushed, ground and sieved to a powder with a particle size of 150 to 850 μm.

Powder C has a retention capacity of 37.1 g / g.

The ones in the examples below specified amounts in which the individual components, such as the postcrosslinker, water or silica sol, during treatment the outside of the untreated, absorbent polymer structure (Pu) are used as quantities based on weight to understand the untreated, absorbent polymer structure (Pu).

INFLUENCE OF TREATMENT THE EXTERIOR OF THE UNTREATED ABSORBENT POLYMERS (PU) ON RETENTION, PERMEABILITY AND ABSORPTION UNDER PRESSURE

Example 1:

A 50 g powder by means of a Krups cake mixer with a solution of 0.5 g of ethylene carbonate, 0.42 g silica sol (Levasil ^® 200 product of Bayer AG, solids content: about 30 wt .-%) and 1.08 g of water with mixed vigorously and then for 30 min. heated in an oven heated to 180 ° C.

Example 2:

50 g of powder A is below by means of a Krups cake mixer with a solution of 0.5 g of ethylene carbonate, 0.84 g silica sol (Levasil ^® 200 product of Bayer AG, solids content: about 30 wt .-%) and 0.66 g of water mixed vigorously and then for 30 min. heated in an oven heated to 180 ° C.

Example 3:

50 g powder B is mixed in with a Krups kitchen mixer with a solution of 0.5 g ethylene carbonate, 0.42 g silica sol (product Levasil ^® 200 from Bayer AG, solids content approx. 30% by weight) and 1.08 g water mixed vigorously and then for 30 min. heated in an oven heated to 180 ° C.

Example 4:

50 g powder B is mixed with a Krups kitchen mixer with a solution of 0.5 g ethylene carbonate, 0.84 g silica sol (product Levasil ^® 200 from Bayer AG, solids content approx. 30% by weight) and 0.66 g water mixed vigorously and then for 30 min. heated in an oven heated to 180 ° C.

Example 5:

50 g of powder C is mixed in with a Krups kitchen mixer with a solution of 0.5 g of ethylene carbonate, 0.42 g of silica sol (product Levasil ^® 200 from Bayer AG, solids content approx. 30% by weight) and 1.08 g of water mixed vigorously and then for 30 min. heated in an oven heated to 180 ° C.

Comparative Example 1:

50 g powder A is by means of a Krups cake mixer with a solution mixed from 0.5 g ethylene carbonate and 1.5 g water with vigorous stirring and subsequently for 30 minute in an oven heated to 180 ° C was heated.

Comparative Example 2:

50 g powder B is by means of a Krups cake mixer with a solution mixed from 0.5 g ethylene carbonate and 1.5 g water with vigorous stirring and subsequently for 30 minute in an oven heated to 180 ° C was heated.

Comparative Example 3:

The post-crosslinked polymer structure obtained in Comparative Example 2 (Bayer AG, about 30 wt .-% product Levasil ^® 200 solids) and 0.16 g of water, mixed with 0.84 g of silica sol with vigorous stirring. The product is then not subjected to any tempering step.

Comparative Example 4:

The post-crosslinked polymer structure obtained in Comparative Example 2 (Levasil ^® from Bayer 200, solids content: about 30 wt .-% product AG) and 0.16 g of water, mixed with 0.84 g silica sol under vigorous stirring and then for 60 min. heated in an oven heated to 100 ° C.

Comparative Example 5:

50 g powder B is mixed using a Krups kitchen mixer with a solution of 0.5 g ethylene carbonate, 0.125 g Aerosil ^® (pyrogenic silica sol from Degussa AG) and 2 g water with vigorous stirring and then for 30 min. heated in an oven heated to 180 ° C. Increased amounts of water were required to prepare the suspension of Aerosih in water. However, no easily metered suspension could be obtained, since the Aerosil ^® that was added settled back very quickly and homogeneous metering onto powder B was not possible. The coated polymer tends to form lumps and is inhomogeneous.

Comparative Example 6:

50 g powder C is by means of a Krups cake mixer with a solution mixed from 0.5 g ethylene carbonate and 1.5 g water with vigorous stirring and subsequently for 30 minute in an oven heated to 180 ° C was heated.

Comparative Example 7:

50 g powder B is mixed with a Krups kitchen mixer with a solution of 0.2.5 g diethylene glycol monomethyl ether, 0.25 g silica sol (product Levasil ^® 200 from Bayer AG, solids content approx. 30% by weight) and 1.25 g water with vigorous Stirring mixed and then for 3 min. heated in an oven heated to 120 ° C. This treatment corresponds to the treatment according to Example 1 of the JP 1994/16822 ,

Comparative Example 8:

50 g powder B is mixed with a Krups kitchen mixer with a solution of 0.25 g 1,3-butanediol, 0.25 g silica sol (product Levasil ^® 200 from Bayer AG, solids content approx. 30% by weight) and 1. 25 g of water mixed with vigorous stirring and then for 3 min. heated in an oven heated to 120 ° C. This treatment corresponds to the treatment according to Example 2 of the JP 1994/16822 ,

The properties of those in the examples 1 to 4 and absorbent obtained in Comparative Examples 1 to 8 Polymer structures are listed in Table 1 below.

The absorbent manufactured according to the invention Polymer structures show a significant increase in permeability (SFC) with constant or even increased retention towards products, whose exterior was crosslinked in the absence of a silica sol (example 1 to 4, comparative examples 1 and 2). A post-treatment of the already post-crosslinking polymer structures with silica sol leads independently of the following thermal treatment did not achieve the desired result (comparative example 3, 4 and 6).

The addition of Aerosil 200 in the Post-crosslinking leads not too good super absorber characteristics (comparative example 5). Furthermore, are increased Amounts of Aerosil no longer dispersed in an acceptable amount of water and are therefore no longer dispersible.

Comparative examples 7 and 8 show that in the examples according to the invention the untested JP 1994/16822 the polymers cannot perform well in terms of their permeability and retention.

Table 1

INFLUENCE OF TREATMENT THE EXTERIOR OF THE UNTREATED ABSORBENT POLYMERS (PU) ON THE AGGLOMERATION TENDENCY OF THE POLYMER AREAS.

Example 5:

50 g powder B by means of a Krups cake mixer with a solution of 0.5 g of ethylene carbonate, 0,125 g of silica sol (Levasil ^® product 20C of Bayer AG, solids content: about 30 wt .-%) and 1.38 g of water with vigorous stirring mixed. A compact is then produced from the absorbent polymer structure brought into contact with the aqueous solution, and its density and the pressure to be used to destroy the compact are determined.

Example 6:

50 g of powder B are mixed with a Krups kitchen mixer with a solution of 0.5 g of ethylene carbonate, 0.125 g of silica sol (product Levasil ^® 200 from Bayer AG, solids content approx. 30% by weight) and 1.25 g of water with vigorous stirring mixed. A compact is then produced from the absorbent polymer structure brought into contact with the aqueous solution, and its density and the pressure to be used to destroy the compact are determined.

Comparative Example 9:

50 g powder B is by means of a Krups cake mixer with a solution mixed from 0.5 g ethylene carbonate and 1.5 g water with vigorous stirring. Subsequently becomes a pellet from that brought into contact with the aqueous solution absorbent polymer structures are produced and its density and the one for destruction pressure to be applied to the compact.

The properties of the absorbent polymer structures brought into contact with the aqueous solution in Examples 5 and 6 and in Comparative Example 9 are summarized in the following Table 2: Table 2

The results show that education stable agglomerates significantly through the addition of silica sol is pushed back. This addition ensures that the untreated, absorbent Polymer structures (Pu) with increased amounts of liquid can be applied without clumping the processability impaired becomes.

TEST METHODS

PERMEABILITY IN THE SOUL CONDITION (SFC TEST)

wobei F_s(t = 0) die Fließrate in g/s,
L_o die Dicke der Gelschicht in cm,
r die Dichte der NaCl-Lösung (1,003 g/cm³),
A die Fläche der Oberseite der Gelschicht im Messzylinder (28,27 cm²),
ΔP der hydrostatische Druck, der auf der Gelschicht lastet (4.920 dyne/cm²), und
K der SFC-Wert ist.The permeability in the swollen state (saline flow conductivity - SFC) is determined by a method described in WO 95/22356. Approx. 0.9 g superabsorbent material is weighed into a cylinder with a sieve bottom and carefully distributed on the sieve surface. The superabsorbent material is allowed to swell in JAYCO synthetic urine for 1 hour against a pressure of 20 g / cm2. After determining the swelling height of the super absorber, 0.118 M NaCl solution is run through the swollen gel layer from a leveled storage vessel at a constant hydrostatic pressure. The swollen gel layer is covered during the measurement with a special sieve cylinder, which ensures an even distribution of the 0.118 M NaCl solution above the gel and constant conditions (measuring temperature 20-25 ° C) during the measurement with regard to the gel bed properties. The pressure acting on the swollen superabsorbent is still 20 g / cm ² . With the help of a computer and a balance, the amount of liquid that passes through the gel layer as a function of time is recorded at intervals of 20 seconds within a time period of 10 minutes.The flow rate g / s through the swollen gel layer is determined by means of regression analysis with extrapolation of the slope and Determination of the center point at the point in time t = 0 of the flow quantity determined within minutes 2-10. The SFC value (K) was given in cm ³ · s · g ^–1 and calculated as follows:

where F _s (t = 0) is the flow rate in g / s,
L _o the thickness of the gel layer in cm,
r the density of the NaCl solution (1.003 g / cm ³ ),
A the area of the top of the gel layer in the measuring cylinder (28.27 cm ² ),
ΔP is the hydrostatic pressure on the gel layer (4,920 dyne / cm ² ), and
K is the SFC value.

DETERMINATION OF AGGLOMERATION TENDENCY

The tendency of liquid-coated Superabsorbers for the formation of agglomerates is used with an indicator from J. R. Johanson Inc. This becomes the super absorber coated with the postcrosslinker solution to be examined and then 50 g of the powder for investigation. The device manufactures with a defined pressure of 160,000 Pa using a press ram in a hollow metal cylinder with an inside diameter of 5.23 cm has a compact with a height from about 2 cm. This compact will then by passing through a second cylinder, which has a diameter of 4.2 cm, destroyed again, the force applied is measured.

Claims (25)

Method of making an absorbent Polymer structure (Pa) by treating the outside of an untreated Absorbent polymer structure (Pu), comprising the steps: - in contact bring the outside of the untreated, absorbent polymer structure (Pu) with an aqueous solution containing at least one chemical crosslinker and at least an inorganic compound in colloidal form; - heating of the absorbent polymer structure, the outer area with the aqueous solution has been brought into contact at a temperature in the range of 40 up to 300 ° C, so that the outer area of the absorbent polymer structure in the Compared to the interior stronger is cross-linked and the inorganic compound in the outer area of the absorbent polymer structure at least partially immobilized becomes. The method of claim 1, wherein the untreated, absorbent polymer structures (Pu) on: (α1) 20-99.999% by weight polymerized, ethylenically unsaturated, containing acid groups Monomers or their salts or polymerized, ethylenically unsaturated, containing a protonated or quaternized nitrogen Monomers, or mixtures thereof, (α2) 0-80% by weight polymerized, monoethylenically unsaturated, with (α1) copolymerizable monomers, (α3) 0.001-5% by weight of one or more crosslinkers, (Α4) 0-30% by weight of a water soluble Polymers, as well (Α5) 0-20% by weight one or more aids based, the sum of the amounts by weight (α1) to (α5) 100 % By weight. Method according to one of the preceding claims, wherein the untreated, absorbent polymer structure (Pu) at least one has the following characteristics: (A) the maximum intake of 0.9% by weight of NaCl solution lies in a range of at least 10 to 1000 g / g, (B) the 0.9 wt: -% he more watery NaC1 solution extractable portion less than 30% by weight, based on the untreated, absorbent Polymer structure, (C) the bulk density lies in the range from 300 to 1000 g / l, (D) the pH of 1 g of the untreated, absorbent polymer structure (Pu) in 1 1 water is in the range of 4 to 10, (E) the CRC value is in the range of 10 to 100 g / g. Method according to one of the preceding claims, wherein the untreated, absorbent polymer structure (Pu) with at most 20% by weight aqueous Solution, based on the weight of the untreated, absorbent polymer structure (Pu} is brought into contact. Method according to one of the preceding claims, wherein two separate watery ones Solutions, one of which is the chemical crosslinker and the other the inorganic Contains compound in colloidal disperse form, at the same time as the untreated absorbent polymer structures are brought into contact. Method according to one of the preceding claims, wherein at least 30% by weight of the inorganic compound in the aqueous Solution, with which the outside of the untreated absorbent polymer structure (Pu) is brought into contact as particles with a particle size in the range from 1 to 100 nm. Method according to one of the preceding claims, wherein the inorganic compound in one Amount of 0.001 to 10 wt .-%, based on the untreated absorbent polymer structure (Pu), is used to treat the outside of an untreated, absorbent polymer structure (Pu}. Method according to one of the preceding claims, wherein particles containing polysilicic acid are used as the inorganic compound become. Method according to one of the preceding claims, wherein a condensation crosslinker is used as the chemical crosslinker. Absorbent polymer structure (Pa), available after according to a procedure one of claims 1 till 9. Absorbent polymer building (Pa) comprising an inner region and an outer region surrounding the inner region, the outer region being more cross-linked than the inner region, an inorganic compound being at least partially immobilized in the outer region and the absorbent polymer structure (Pa) having at least one of the following properties: ( β1) with a CRC <26 g / g an SFC of at least 80 · 10 ^–7 cm ³ · s · g ^–1 , (β2) with a CRC in the range ≥ 26 to <27 g / g an SFC of at least 70 · 10 ^-7 cm ³ · s · g ^-1 , (β3) with a CRC in the range ≥ 27 to <28 g / g an SFC of at least 60 · 10 ^-7 cm ³ · s · g ^-1 , (β4) a CRC in the range ≥ 28 to <29 g / g an SFC of at least 45 · 10 ^–7 cm ³ · s · g ^–1 , (β5) with a CRC in the range ≥ 29 to <30 an SFC of at least 30 · 10 ^–7 cm ³ · s · g ^-1 , (β6) with a CRC in the range ≥ 30 to <31 an SFC of at least 20 · 10 ^–7 cm ³ · s · g ^-1 . (β7) with a CRC in the range ≥ 31, an SFC of at least 10 · 10 ⁻⁷ cm ³ · s · g ^-1 . Absorbent polymer structure (Pa) according to claim 11, wherein the absorbent polymer structure has an Absorbency against Pressure (AAP) at a pressure of 50 g / cm ² of at least 18 g / g. Absorbent polymer structure (Pa) according to one of the Expectations 11 to 12, wherein the inorganic compound is a condensate of polysilicic acids. Composite, including an absorbent polymer structure (Pa) according to claim 10 or 11 and a substrate. Method for producing a composite, wherein an absorbent polymer structure (Pa) according to claim 10 or 11 and a substrate and optionally an auxiliary with each other be brought into contact. Composite available according to a method according to claim 15th Chemical products, including the absorbent Polymer structure (Pa) according to claim 10 or 11 or the composite according to Claim 14 or 16. Use of the absorbent polymer structure (Pa) according to claim 10 or 11 or the composite according to claim 14 or 16 in chemical products. aqueous solution containing at least one chemical crosslinker and at least an inorganic compound in colloidal form. Process for producing an aqueous solution of claim 19, wherein an aqueous solution containing at least one inorganic compound in colloidal dispersion Form is mixed with at least one chemical crosslinker. The method of claim 20, wherein the chemical Crosslinker in the form of an aqueous solution is used. A watery one solution available according to a method according to claim 20 or 21. A watery one solution The claim 19 or 22, wherein the inorganic compound contains polysilicic acid Particles are. Use of the aqueous solution according to claim 19 or 22 for treating the outside area an untreated, absorbent polymer structure (Pu). Use of the aqueous solution according to claim 19 or 22 for adjusting at least one of the following Properties in an untreated, absorbent polymer structure (Pu): (Γ1) Saline Flow Conductivity (SFC), (γ2) centrifugation retention Capacity (CRC) or (Γ3) Absorbency against Pressure (AAP).