DE102005018923A1 - Water absorbing polymer product, useful in e.g. foams, molded articles, fibers, foils, films, cables and sealing materials, comprises a surface that is contacted with a combination of a metal salt and a metal oxide - Google Patents

Abstract

Water absorbing polymer product comprises a surface that is contacted with a combination of a metal salt and a metal oxide. Independent claims are included for: (1) a procedure to treat the surface of water-absorbing polymer product, comprising providing an untreated, water-absorbing polymer entity; and contacting the untreated surface of the water-absorbing polymer product with a combination of the metal salt and the metal oxide at 100-300[deg]C; (2) a combination comprising a water absorbing polymer product and a substrate; (3) the preparation of the combination comprising contacting the water absorbing polymer product, the substrate and optionally an auxiliary agent; and (4) a foam, molded article, fiber, foil, film, cable, sealing material, fluid absorbing sanitary article, carriers for plant- and fungus growth regulating agent, packing material, basic additive or a building material comprising water-absorbing polymer product.

Description

The The present invention relates to water-absorbing polymer structures, a method of treating the surface of water-absorbing polymer structures, those obtainable by this method surface-treated, water-absorbing polymer structure comprising a composite water-absorbing polymer structure and a substrate, a method for producing a composite obtainable by this process Composite comprising chemical products such as foams, shaped bodies and fibers water-absorbing polymer structures or a composite, the use water-absorbing polymer structure or a composite in chemical Products as well as the use of a combination of an oxide a metal and a metal salt for treating the surface of superabsorbent Polymer structure.

superabsorbent are water-insoluble, crosslinked polymers that are capable of swelling and forming of hydrogels great Amounts of aqueous Liquids, especially body fluids, preferably urine or blood, and take under a certain Withhold pressure. By these characteristic properties these polymers find mainly Application in the incorporation in sanitary articles, such as Baby diapers, incontinence products or sanitary napkins.

The Production of superabsorbents is usually carried out by the radical Polymerization acid bearing Monomers in the presence of crosslinkers. It can be through the Selection of the monomer composition, the crosslinker and the polymerization conditions and the processing conditions for after the polymerization obtained hydrogel polymers with different absorptive properties produce. More options offers the preparation of graft polymers, for example, under Use of chemically modified starch, cellulose and polyvinyl alcohol to DE-OS 26 12 846.

DE 40 20 780 C1 discloses the post-treatment of superabsorbent polymers by post-crosslinking the surfaces of the polymer particles. By the post-crosslinking of the surface of the water-absorbing polymer particles, in particular, the absorption capacity of the polymer particles is increased under the action of pressures.

DE 199 09 653 A1 and DE 199 09 838 A1 describe powdery, surface-postcrosslinked, water, aqueous or serous liquids or blood-absorbing polymers which are based on acid group-carrying monomers and which has been coated with a surface postcrosslinking agent and a cation in aqueous solution and postcrosslinked. The polymers disclosed in this prior art have advantageous absorption properties, in particular high permeability, over conventional polymers.

The Surface postcrosslinking disclosed in the prior art cited above the polymer structure leads though to an increase the absorption capacity under a compressive load, however, is with this surface postcrosslinking usually associated with a reduction in retention capacity. Conversely leads an increase, caused for example by low primary crosslinking, of the Retention capacity too a reduced absorption capacity of the polymer structures below a pressure load. A reduced retention capacity of the polymer structures However, it has the disadvantage that sanitary articles such as diapers, which These polymer structures include, by a reduced uptake and retention of body fluids are marked while a decreased absorption under pressure in particular causes the hygiene products liquids under a compressive load, such as a seated diaper carrier caused, can not absorb enough.

Polymer structure, which a good retention behavior and a good absorption capacity could be subject to a pressure load, could possibly be preserved be that from the outset only slightly cross-linked polymer particles, which due to the low degree of crosslinking a comparatively have high retention, subjected to surface postcrosslinking become. However, this has the disadvantage that in this way obtained superabsorbent by a high content of soluble Shares are characterized as the content of soluble fractions decreases Degree of crosslinking increases. An increasing content of soluble Proportions, however, is associated with a reduced skin tolerance connected so that sanitary articles containing polymer structures with a high content of soluble From a dermatological point of view are questionable. To the salary on soluble Shares in the polymer structures as low as possible, is therefore a minimum primary networking desirable in the polymer structure.

Of the Present invention was based on the object resulting from the Overcome prior art disadvantages.

Especially The object of the present invention was to provide superabsorbents provide, in addition to excellent retention properties also by good absorption properties under a pressure load and advantageously also by good skin compatibility Marked are.

Farther The object of the present invention was to provide methods with the superabsorber which is so advantageous as well as a composite comprising These superabsorbents can be produced. In particular, should be by this method, the retention and the absorption capacity of Superabsorbent under a pressure load independently improve can let.

Also The present invention was based on the object of hygiene articles to provide a high content of water-absorbing polymer structures, which by a particularly good skin compatibility and continue good Absorption properties, in particular a good absorption capacity for body fluids, Marked are.

a Contribution to the solution The above objects provide a water-absorbing Polymer structure whose surface with a combination of a metal salt and an oxide of a Metal has been brought into contact.

Completely surprising, However, no less favorable was found that the Retention properties of superabsorbent particles, for example by treating the surfaces water-absorbing polymer structure with a combination of a Metal salt and an oxide of a metal can be improved. Especially It was observed that the surface treatment of the water-absorbing polymer structures with the combination of a metal salt and the oxide of a metal in the case of surface postcrosslinking observed reduction of retention is significantly weaker than in surface postcrosslinked Polymeric structures whose surface not with this combination of a metal salt and an oxide a metal has been brought into contact. By the surface modification according to the invention is it possible, for example, Polymeric structure with a high degree of primary crosslinking, which by a corresponding low content of soluble fractions and a corresponding low retention capacity are characterized by taking place after the polymerization surface treatment in their retention capacity to improve, making polymer structures with an excellent R / LA ratio obtained can be.

According to the invention preferred Polymeric structures are fibers, foams or particles, with fibers and particles being preferred and particles are particularly preferred.

According to the invention preferred Polymer fibers are sized to be in or as yarns for textiles and can also be incorporated directly into textiles. It is preferred according to the invention, that the polymer fibers have a length in the range of 1 to 500 mm, preferably 2 to 500 mm and especially preferably 5 to 100 mm and a diameter in the range of 1 to 200 denier, preferably 3 to 100 denier and more preferably 5 own up to 60 deniers.

According to the invention preferred Polymer particles are sized to have an average particle size according to ERT 420.2-02 in the range from 10 to 3000 μm, preferably 20 to 2000 microns and more preferably 150 to 850 microns. It is in particular preferred that the proportion of the polymer particles having a particle size in one Range of 300 to 600 microns at least 30% by weight, more preferably at least 40% by weight, and most preferably at least 50% by weight, based on the total weight the postcrosslinked, water-absorbing polymer particles is.

• (α1) 20–99,999 Gew.-%, bevorzugt 55–98,99 Gew.-% und besonders bevorzugt 70–98,79 Gew.-% polymerisierten, ethylenisch ungesättigten, säuregruppentragenden 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) 0,001 bis 5 Gew.-%, vorzugsweise 0,01 bis 2,5 Gew.-% und am meisten bevorzugt 0,1 bis 1 Gew.-% des Metallsalzes,
• (α5) 0,001–5 Gew.-%, vorzugsweise 0,01–2,5 Gew.-% und am meisten bevorzugt 0,1–1 Gew.-% des Oxides des Metalls,
• (α6) 0–30 Gew.-%, vorzugsweise 0–5 Gew.-% und besonders bevorzugt 0,1–5 Gew.-% eines wasserlöslichen Polymeren,
• (α7) 0–20 Gew.-%, vorzugsweise 2,5–15 Gew.-% und besonders bevorzugt 5–10 Gew.-% Wasser, sowie
• (α8) 0–20 Gew.-%, vorzugsweise 0–10 Gew.-% und besonders bevorzugt 0,1–8 Gew.-% eines oder mehrerer Hilfsmittel, wobei die Summe der Gewichtsmengen (α1) bis (α8) 100 Gew.-% beträgt.

In a preferred embodiment of the water-absorbing polymer structures according to the invention, these are based on

• (α1) 20-99.999 wt .-%, preferably 55-98.99 wt .-% and particularly preferably 70-98.79 wt .-% polymerized, ethylenically unsaturated, acid group-carrying monomers or their salts or polymerized, ethylenically unsaturated, one protonated or quaternized nitrogen-containing monomers, or mixtures thereof, wherein at least ethylenically unsaturated, acid group-containing monomers, preferably acrylic acid-containing mixtures are particularly preferred,
• (α2) 0-80 wt .-%, preferably 0-44.99 wt .-% and particularly preferably 0.1-44.89 wt .-% polymerized, monoethylenically unsaturated, with (α1) copolymerizable monomers,
• (α3) 0.001-5 wt .-%, preferably 0.01-3 wt .-% and particularly preferably 0.01-2.5 wt .-% of one or more crosslinkers,
• (α4) from 0.001 to 5% by weight, preferably from 0.01 to 2.5% by weight and most preferably from 0.1 to 1% by weight of the metal salt,
• (α5) 0.001-5 wt.%, preferably 0.01-2.5 wt.% and most preferably 0.1-1 wt.% of the oxide of the metal,
• (α6) 0-30 wt .-%, preferably 0-5 wt .-% and particularly preferably 0.1-5 wt .-% of a water-soluble polymer,
• (α7) 0-20 wt .-%, preferably 2.5-15 wt .-% and particularly preferably 5-10 wt .-% water, and
• (α8) 0-20 wt .-%, preferably 0-10 wt .-% and particularly preferably 0.1-8 wt .-% of one or more auxiliaries, wherein the sum of the amounts by weight (α1) to (α8) 100 wt .-% is.

The monoethylenically unsaturated acid group-containing monomers (α1) may 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%. In this context is on DE 195 29 348 A1 The disclosure of which is hereby incorporated by reference. The neutralization can be done partially or completely even after the polymerization. Furthermore, the neutralization can be carried out with alkali metal hydroxides, alkaline earth metal hydroxides, ammonia and carbonates and bicarbonates. In addition, every other base is conceivable, which forms a water-soluble salt with the acid. Also a mixed neutralization with different bases is conceivable. Preference is given to neutralization with ammonia and alkali metal hydroxides, particularly preferably with sodium hydroxide and with ammonia.

Further can for a polymer, the free acid groups predominate, so that this polymer has a pH in the acidic range having. This acidic water-absorbing polymer can be replaced by a polymer with free basic groups, preferably amine groups, by comparison to which the acidic polymer is basic, at least partially neutralized become. These polymers are referred to in the literature as "Mixed-Bed Ion-Exchange Absorbent Polymers "(MBIEA polymers) and are disclosed inter alia in WO 99/34843 A1. The revelation WO 99/34843 A1 is hereby incorporated by reference and is thus considered part of the revelation. In general, MBIEA polymers provide a composition comprising, on the one hand, basic polymers which are used in are able to exchange anions, and on the other hand a comparison to the basic polymer acidic polymer that is capable of cations exchange. The basic polymer has basic groups and is typically due to the polymerization of monomers obtained that carry basic groups or groups that are basic Groups can be converted. These monomers are, above all, 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 ethyleneamine, allylamine, diallylamine, 4-aminobutene, Alky loxycycline, vinylformamide, 5-aminopentene, carbodiimide, formaldacin, Melamine and the like, as well as their secondary or tertiary amine derivatives.

preferred ethylenically unsaturated, containing acid groups Monomers (α1) are preferably those compounds described in WO 2004/037903 A2, which is hereby incorporated by reference and thus as part of the Revelation applies as ethylenically unsaturated, acid group-containing monomers called (α1) become. Particularly preferred ethylenically unsaturated, acid group-containing monomers (α1) acrylic acid and methacrylic acid, being acrylic acid most preferred.

According to one embodiment the method according to the invention Water-absorbing polymer structures are used in which the monoethylenically unsaturated, with (α1) copolymerizable monomers (α2) Acrylamides, methacrylamides or vinylamides are.

preferred (Meth) acrylamides are alkyl-substituted in addition to acrylamide and methacrylamide (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 vinylamides are for example N-vinylamides, N-vinylformamides, N-vinylacetamides, N-vinyl-N-methylacetamides, N-vinyl-N-methylformamide, vinylpyrrolidone. Among these monomers especially preferred is acrylamide.

According to another embodiment of the process according to the invention, water-absorbing polymer structures are used in which the monoethylenically unsaturated, copolymerizable with (α1) Monomers (α2) are water-soluble monomers. Alkoxypolyalkylene oxide (meth) acrylates such as methoxypolyethylene glycol (meth) acrylates are particularly preferred in this context.

Of Further, as monoethylenically unsaturated, with (α1) copolymerizable Monomers (α2) water-dispersible monomers are preferred. As dispersible in water Monomers are acrylic esters and methacrylates, such as methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate or butyl (meth) acrylate.

The monoethylenically unsaturated, with (α1) copolymerizable monomers (α2) further include methyl polyethylene glycol allyl ether, vinyl acetate, Styrene and isobutylene.

When Crosslinker (α3) Preferably, those compounds are used, which in the WO 2004/037903 A2 as crosslinker (α3) to be named. Among these crosslinkers, water-soluble crosslinkers are especially prefers. Most preferred are N, N'-methylenebisacrylamide, polyethylene glycol di (meth) acrylates, Triallylmethylammoniumchlorid, Tetraallylammoniumchlorid and with 9 moles of ethylene oxide per mole of acrylic acid Allylnonaethylenglykolacrylat prepared particularly preferred.

When Metal salt (α4) can all metal salts known to those skilled in the art are used, wherein but water-soluble Metal salts are particularly preferred. "Water-soluble" are preferably metal salts understood, of which at a temperature of 25 ° C preferably at least 1 g, more preferably at least 10 g, moreover preferably at least 100 g and most preferably at least 500 g are soluble in one liter of distilled water.

Under The above-mentioned, preferably water-soluble metal salts are in particular Sulfates, sulfites, sulfides, chlorides, bromides, iodides, nitrates, nitrites, phosphates, Phosphites, carbonates, bicarbonates, hydroxides, acetates, lactates and oxalates, with sulfates being most preferred.

Furthermore, it is preferred according to the invention that the metal cation of the metal salt is a monovalent, divalent or trivalent metal cation, with trivalent metal cations being most preferred. Preferred metal cations are Na ⁺ , K ⁺ , Li ⁺ , M ^{2 +} , Ca ²⁺ , Fe ²⁺ , Fe ³⁺ , A ⁺ , Cu ⁺ Cu ²⁺ , Zn ²⁺ , and Al ³⁺ , where as Al ^{3+ is} most preferred.

The following metal salts are preferably contained in the water-absorbing polymer structures according to the invention as surface treatment agents: AlCl ₃ × 6H ₂ O, NaAl (SO ₄ ) 2 × 12 H ₂ O, Al (NO ₃ ) ₃ × 9 H ₂ O, KAl (S0 ₄ ) ₂ × 12 H ₂ O or Al ₂ (SO ₄ ) ₃ × 14-18 H ₂ O and the corresponding anhydrous salts, Na ₂ SO ₄ or its hydrates, MgSO ₄ × 10 H ₂ O or anhydrous magnesium sulfate.

When Oxide of a metal are preferably used powdery oxides. there For example, it is particularly preferred that at least 50% by weight, preferably at least 75% by weight and most preferably at least 90% by weight of the oxide of the metal by sieve analysis (for particle sizes greater than 10 μm) or Laser diffractometry (for Particle sizes smaller than 10 μm) Particle size in one Range of 10 to 1,000,000 nm, more preferably in one range from 100 to 500,000 nm, and most preferably in one range from 1 to 250 μm exhibit. Furthermore, it is preferred that the oxide of the metal a weight average particle size in a range of 50 up to 500 μm, preferably in a range of 75 to 400 microns, and most preferably in a range of 100 to 300 microns having.

When Oxide of a metal can all metal oxides are used, wherein as the "oxide of a metal" not the oxides of semimetals, such as boron, silicon or germanium understood become.

In a preferred embodiment the water-absorbing invention Polymeric structures include these as oxide of a metal an oxide a transition metal, among the transition metals zinc most preferred.

In a particular embodiment of the water-absorbing polymer structures according to the invention, these contain as oxide of a metal a finely divided zinc oxide which is based to at least 50 wt .-% on optionally agglomerated particles having a particle size in a range of about 10 nm to 500 microns. Such finely divided zinc oxides are, for example, under the trade name "Nanox ^®" from Elementis Specialties, USA.

Water-absorbing polymer structures which are particularly preferred according to the invention are Pelymer structures, whose surface has been contacted with a water-soluble salt of aluminum as a metal salt and with a powdery zinc oxide as an oxide of a metal.

When water-soluble Polymers (α6) can water-soluble in the polymer structures Polymers, such as partially or fully saponified polyvinyl alcohol, polyvinylpyrrolidone, Strength or starch derivatives, Polyglycols or polyacrylic acid contained, preferably copolymerized. The molecular weight These polymers are not critical as long as they are water soluble. Preferred water-soluble Polymers are starch or starch derivatives or polyvinyl alcohol. The water-soluble polymers, preferably Synthetic such as polyvinyl alcohol, can also be used as a grafting base for the serve to be polymerized monomers.

When Aids (α8) are preferably settling agents, odor binders, surface-active Agents or antioxidants as well as those additives that are used to manufacture the polymer structures were used (initiators, etc.) in the polymer structures contain.

In a particular embodiment the polymer structures of the invention These are based to at least 50 wt .-%, preferably at least 70% by weight and above more preferably at least 90% by weight on carboxylate-bearing Monomers. It is still according to the invention preferred that the component (α1) at least 50 wt .-%, preferably at least 70 wt .-% of acrylic acid which is preferably at least 20 mol%, more preferably to at least 50 mol% and above Moreover, it is preferably neutralized in a range of 60 to 85% by mole is.

In another preferred embodiment the polymer structures of the invention These have a core-shell structure and include an interior area (Core) and an outer area (shell) surrounding the inner area on, wherein the polymer structure in the outdoor area more crosslinked is considered indoors.

Farther are the water-absorbing invention Polymeric structures whose surface contacted with a metal salt and an oxide of a metal have been through an R / LA ratio of at least 2.59 g / g ·%, more preferably at least 2.8 g / g%, and most preferably at least 3 g / g ·% characterized. Here R is the according to ERT 441.2-02 (ERT = EDANA Recommended Test Method) determined CRC value (CRC = Centrifugation Retention Capacity; in the case of particles each determined for the whole Particle fraction) and LA determined according to ERT 470.2-02 Content of extractables (soluble Interests).

Furthermore, the water-absorbing polymer structures according to the invention are preferably characterized by an absorption determined according to ERT 442.2-02 under a pressure of 50 g / cm ² of at least 15 g / g, preferably at least 17 g / g and most preferably at least 19 g / g (in Case of particles each determined for the entire particle fraction).

• i) Bereitstellen eines unbehandelten, wasserabsorbierenden Polymergebildes;
• ii) in Kontakt bringen der Oberfläche des unbehandelten, wasserabsorbierenden Polymergebildes mit einer Kombination aus einem Metallsalz und einem Oxid eines Metalls bei einer Temperatur in einem Bereich von 100 bis 300°C, vorzugsweise in einem Bereich von 125 bis 250°C und am meisten bevorzugt in einem Bereich von 150 bis 200°C.

A contribution to the solution of the abovementioned objects is also provided by a process for the treatment of the surface of water-absorbing polymer structures, comprising the process steps

• i) providing an untreated, water-absorbing polymer structure;
• ii) contacting the surface of the untreated, water-absorbing polymer structure with a combination of a metal salt and an oxide of a metal at a temperature in a range of 100 to 300 ° C, preferably in a range of 125 to 250 ° C, and most preferably in a range of 150 to 200 ° C.

"Untreated" in the sense of the present Invention means that the water-absorbing polymer structures not yet with the combination of a metal salt and an oxide of a metal have been brought into contact. The term "untreated", however, concludes not that the water-absorbing polymer structures by means of other surface modification measures, such as surface postcrosslinking, can be modified. It is particularly according to the invention preferred that the untreated water-absorbing polymer structure one in accordance with ERT 441.2-02 CRC value of at least 30 g / g, more preferably at least 35 g / g and most preferably at least 40 g / g (in the case of of particles each determined for the entire particle fraction). Furthermore, the term "untreated water-absorbing polymer structure "also polymer structures that are not yet are completely dried and still have a water content of more than 10 wt .-%, preferably more than 20% by weight, and most preferably more than 30% by weight, in each case based on the total weight of the untreated, water-absorbing Polymer-formed, have.

• a) radikalische Polymerisation säuregruppen-tragender, ethylenisch ungesättigter, gegebenenfalls teilneutralisierter Monomere in Gegenwart eines Vernetzers unter Bildung eines Hydrogels;
• b) gegebenenfalls Zerkleinern des Hydrogels;
• c) Trocknen des gegebenenfalls zerkleinerten Hydrogels unter Erhalt wasserabsorbierender Polymergebilde;
• d) gegebenenfalls Zermahlen des so erhaltenen absorbierenden Polymergebildes und absieben auf eine gewünschte Partikelgrößenfraktion;
• e) gegebenenfalls weitere Oberflächenmodifizierungen der so erhalten wasserabsorbierenden Polymergebilde;

The untreated, water-absorbing polymer structures used in the process according to the invention are preferably polymers which have been obtained by a process comprising the process steps:

• a) free radical polymerization of acid group-carrying, ethylenically unsaturated, optionally partially neutralized monomers in the presence of a crosslinker to form a hydrogel;
• b) optionally comminuting the hydrogel;
• c) drying the optionally comminuted hydrogel to obtain water-absorbing polymer structures;
• d) optionally grinding the resulting absorbent polymer structure and sieving to a desired particle size fraction;
• e) optionally further surface modifications of the resulting water-absorbing polymer structures;

The "untreated" polymer structure obtained in this manner is then contacted with the combination of a metal salt and a metal oxide, it being preferred that the metal salt and the oxide of the metal be in the form of a fluid F ₁ comprising a solvent Water and water-miscible organic solvents such as methanol, ethanol, 1-propanol, 2-propanol or 1-butanol or mixtures of at least two of these solvents are used, with water being the most preferred solvent, Further, it is preferable that the metal salt in the fluid F _{1 be} in an amount in a range of 0.1 to 50% by weight, more preferably 1 to 40 % By weight and most preferably 5 to 25% by weight and the oxide of the metal in the fluid F ₁ in an amount in the range of 0, 1 to 50 wt .-%, particularly preferably 1 to 40 wt .-% and most preferably 5 to 25 wt .-%, each based on the total weight of the solvent, is included. It is also conceivable to use the metal salt and the oxide of the metal in separate fluids.

Farther is it preferred according to the invention that the metal salt in an amount in a range of 0.001 to 5% by weight, preferably 0.01 to 2.5% by weight, and more preferably 0.1 to 1% by weight and the oxide of the metal in an amount in one Range of 0.001 to 5 wt .-%, preferably 0.01 to 2.5 wt .-% and even more preferably 0.1 to 1 wt .-%, each based on the weight of the untreated water-absorbing polymer structure with which untreated water-absorbing polymer structures brought into contact become.

When Metal salt and oxide of a metal salt are those compounds preferably, the input already in connection with the water-absorbing invention Polymer structures have been mentioned as preferred components (α4) and (α5).

Suitable mixing units for applying the fluid F ₁ are again the Patterson-Kelley mixer, DRAIS turbulence mixers, Lödigemischer, Ruberg mixer, screw mixers, plate mixers and fluidized bed mixers and con- continuously working vertical mixer in which the polymer structure mixed by means of rotating blades in fast frequency becomes (Schugi mixer).

• (α1) die ethylenisch ungesättigten, säuregruppen-tragenden Monomeren oder deren Salze, wobei Acrylsäure als säuregruppentragendes Monomer besonders bevorzugt ist,
• (α2) gegebenenfalls monoethylenisch ungesättigte, mit (α1) copolymerisierbare Monomere,
• (α3) den Vernetzer,
• (α6) gegebenenfalls ein wasserlösliches Polymer, sowie
• (α8) gegebenenfalls einen oder mehrere Hilfsmittel beinhaltet.

The radical polymerization taking place in process step a) is preferably carried out in aqueous solution, this aqueous solution preferably being used in addition to water as solvent

• (α1) the ethylenically unsaturated acid group-carrying monomers or their salts, acrylic acid being particularly preferred as the acid group-carrying monomer,
• (α2) optionally monoethylenically unsaturated monomers copolymerizable with (α1),
• (α3) the crosslinker,
• (α6) optionally a water-soluble polymer, and
• (α8) optionally contains one or more adjuvants.

When ethylenically unsaturated, carrying acid groups Monomers (α1), as monoethylenically unsaturated, with (α1) copolymerizable monomers (α2), as crosslinker (α3), as water-soluble Polymers (α6) and as an aid (α8) In turn, those compounds are preferred which are already mentioned at the beginning in connection with the polymer structures according to the invention as ethylenic unsaturated, carrying acid groups Monomers (α1), as monoethylenically unsaturated, with (α1) copolymerizable monomers (α2), as crosslinker (α3), as water-soluble Polymers (α6) and as an aid (α8) were called.

From the abovementioned monomers, comonomers, crosslinkers, water-soluble polymers and auxiliaries, the water-absorbing polymer structures can be prepared by various polymerization methods produce. For example, in this context, bulk polymerization, which preferably takes place in kneading reactors such as extruders, solution polymerization, spray polymerization, inverse emulsion polymerization and inverse suspension polymerization, may be mentioned.

Preferably, the solution polymerization is carried out in water as a solvent. The solution polymerization can be continuous or discontinuous. From the prior art, a wide range of possible variations in terms of reaction conditions such as temperatures, type and amount of initiators and the reaction solution can be found. 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 incorporated by reference and thus are considered part of the disclosure.

The Polymerization, as is common practice, by an initiator triggered. As initiators for the initiation of the polymerization, all under the polymerization conditions free-radical initiators used, usually be used in the production of superabsorbents. Also one Initiation of the polymerization by the action of electron beams on the polymerizable, aqueous Mixture is possible. However, the polymerization can also be carried out in the absence of initiators of the type mentioned above by the action of high-energy radiation in the presence of photoinitiators. polymerization can in a solution Inventive monomers solved or dispersed. As initiators come all the person skilled in known compounds decomposing into radicals. This includes in particular those initiators who already in WO 2004/037903 A2 as possible initiators to be named.

Especially is preferred for the preparation of water-absorbing polymer structures a redox system consisting of hydrogen peroxide, sodium peroxodisulfate and ascorbic acid used.

Also the inverse suspension and emulsion polymerization can be used for the preparation be applied to the polymer structure. According to these processes, one becomes aqueous partially neutralized solution the monomers (α1), and (α2), optionally including water-soluble polymers and auxiliaries, with the aid of protective colloids and / or emulsifiers in a hydrophobic, organic solvents dispersed and initiated by radical initiators the polymerization. The crosslinkers are either dissolved in the monomer solution and are combined with it dosed or separately and optionally added during the polymerization. Possibly the addition of a water-soluble Polymers (α6) as a grafting over the monomer solution or by direct submission to the oil phase. Subsequently, will the water is azeotropically removed from the mixture and the polymer filtered off.

Furthermore, in the solution polymerization as well as in the inverse suspension and emulsion polymerization, the crosslinking can be effected by copolymerization of the polyfunctional crosslinker dissolved in the monomer solution and / or by reaction of suitable crosslinkers with functional groups of the polymer during the polymerization steps. The methods are for example in the publications US 4,340,706 . DE 37 13 601 . DE 28 40 010 and WO 96/05234 A1, the corresponding disclosure of which is hereby incorporated by reference.

The in the solution polymerization or the inverse suspension and emulsion polymerization in the process step a) hydrogels obtained are dried in process step c).

Especially in the case of solution polymerization However, it is preferred that the hydrogels before drying in first an additional Process step b) are crushed. This crushing is done by Shredding devices known to the person skilled in the art, such as a Meat grinder.

The Drying of the hydrogel is preferably carried out in suitable dryers or ovens. Exemplary are rotary kilns, Fluid bed dryer, plate dryer, paddle dryer or infrared dryer called. Furthermore, it is preferred according to the invention that the drying of the hydrogel in process step c) to a water content from 0.5 to 25% by weight, preferably from 1 to 10% by weight, the drying temperatures usually in a range from 100 to 200 ° C lie.

The dried water-absorbing polymer structures obtained in process step c), in particular if they were obtained by solution polymerization, can still be ground in a further process step d) and sieved to the desired grain size mentioned at the outset. The grinding of the dried, water-absorbing polymer structures is preferably carried out in suitable, mechani crushers, such as a ball mill.

in the Following the drying of the hydrogels and optionally carried out further preparation of the dried water-absorbing Polymer structures can this in a further process step e) in the surface area be modified (in addition to the more detailed below Described modification with the combination of the metal salt and the oxide of a metal).

A preferred modification measure here is the surface postcrosslinking, in which the dried polymer structure or else the not yet dried but preferably already comminuted hydrogel is brought into contact with a preferably organic, chemical surface postcrosslinker. In this case, the postcrosslinker, in particular if it is not liquid under the postcrosslinking conditions, is preferably brought into contact with the polymer particles or the hydrogel in the form of a fluid F ₂ comprising the postcrosslinker and a solvent. The solvents used are preferably water, water-miscible organic solvents such as methanol, ethanol, 1-propanol, 2-propanol or 1-butanol or mixtures of at least two of these solvents, with water being the most preferred solvent. Furthermore, it is preferred that the postcrosslinker in the fluid F ₂ in an amount in a range of 5 to 75 wt .-%, particularly preferably 10 to 50 wt .-% and most preferably 15 to 40 wt .-%, based on the total weight of the fluid F ₂ , is included.

The bringing into contact of the polymer structure or of the comminuted hydrogel with the fluid F ₂ comprising the postcrosslinker preferably takes place in the process according to the invention by good mixing of the fluid F ₂ with the polymer structure.

Suitable mixing units for applying the fluid F ₂ are z. As the Patterson-Kelley mixer, DRAIS turbulence mixers, Lödigemischer, Ruberg mixer, screw mixers, plate mixers and fluidized bed mixers and continuously operating vertical mixers in which the polymer structure is mixed by means of rotating blades in rapid frequency (Schugi mixer).

The Polymer structure is in the process according to the invention in the post-crosslinking preferably with at most 20 wt .-%, more preferably at least 15 wt .-%, beyond preferably with at most 10% by weight, above even more preferably with at most 5% by weight of solvent, preferably water, brought into contact.

In the case of polymer structures in the form of preferably spherical particles, it is further preferred according to the invention for the contacting to take place so that only the outer area but not the inner area of the particulate polymer structures are brought into contact with the fluid F ₂ and thus with the postcrosslinker.

When Postcrosslinkers which are used in the process according to the invention are preferably understood compounds which are at least two have functional groups with functional groups of a Polymer structure in a condensation reaction (= condensation crosslinker), can react in an addition reaction or in a ring-opening reaction. When Postcrosslinkers are preferred in the process according to the invention mentioned in WO 2004/037903 A2 as a crosslinker of crosslinking classes II were.

Under These compounds are particularly preferred as Nachvernetzer Kondensationsvemetzer such as diethylene glycol, triethylene glycol, polyethylene glycol, Glycerol, polyglycerol, propylene glycol, diethanolamine, triethanolamine, Polyoxypropylene, oxyethylene-oxypropylene block copolymers, sorbitan fatty acid esters, polyoxyethylene, Trimethylolpropane, pentaerythritol, polyvinyl alcohol, sorbitol, 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-dioxan-2-one, 4-methyl-1,3-dioxan-2 on, 4,6-dimethyl-1,3-dioxane-on-2 as well as 1,3-dioxolan-2-one.

After this the polymer structures or the hydrogels with the postcrosslinker or brought into contact with the fluid containing the postcrosslinker were, they are to a temperature in the range of 50 to 300 ° C, preferably 75 to 275 ° C and more preferably heated at 150 to 250 ° C, so that, preferably whereby, the outer area of the polymer structures compared to the inner area stronger is crosslinked (= post-crosslinking). The duration of the heat treatment is due to the danger that the desired property profile of the Polymer structure is destroyed as a result of exposure to heat limited.

The surface modification by means of post-crosslinking described above can also take place at the same time with the modification of the water-absorbing polymer structures with the combination of a metal salt and an oxide of a metal. In this case, it is preferable to add the postcrosslinker already to the fluid F ₁ or to bring the fluid F ₁ and the fluid F ₂ into contact with the water-absorbing polymer structure at the same time.

In an embodiment the method according to the invention takes place bringing into contact the untreated water-absorbing Polymer structure with the combination of the metal salt and the oxide of a After the water-absorbing polymer structures with a in WO 2004/037903 A2 as crosslinkers of crosslinking classes II mentioned Postcrosslinkers have been postcrosslinked.

In another embodiment of the process according to the invention, the contacting of the untreated water-absorbing polymer structures with the combination of the metal salt and the oxide of a metal takes place simultaneously with contacting the water-absorbing polymer structures with a crosslinker of crosslinking classes II mentioned in WO 2004/037903 A2 Postcrosslinker, in which case it is preferred to add the crosslinker of the crosslinker class II to the fluid F ₁ . In this case, it is preferable that the untreated water-absorbing polymer structures contacted with the fluid F ₁ comprising the metal salt, the oxide of the metal and the crosslinker of crosslinker class II are at a temperature in a range of 50 to 300 ° C, preferably 75 to 275 ° C and most preferably from 150 to 250 ° C to heat.

In a further embodiment the method according to the invention takes place bringing into contact the untreated water-absorbing Polymer structure with the combination of the metal salt and the oxide a metal before the water-absorbing polymer structure with a in WO 2004/037903 A2 as crosslinkers of crosslinking classes II mentioned Postcrosslinker has been brought into contact.

a further contribution to the solution The objects described in the introduction provide the method according to the invention available surface-treated water-absorbing polymer structures.

there it is preferred that the water-absorbing polymer structures according to the invention described above have the same properties as those by the method according to the invention available surface-treated water-absorbing polymer structures. It is also preferred according to the invention that those values associated with the method of the invention and the polymer structures according to the invention given as lower limits of features according to the invention without upper limits were 20 times, preferably 10 times and especially preferred 5 times the most preferred value of the lower limit.

A further solution to the problems described above is provided by a composite comprising the water-absorbing polymer structures according to the invention or the surface-treated water-absorbing polymer structures obtainable by the process according to the invention and a substrate. It is preferred that the polymer structures according to the invention and the substrate are firmly joined together. As substrates, films of polymers, such as of polyethylene, polypropylene or polyamide, metals, nonwovens, fluff, tissues, fabrics, natural or synthetic fibers, or other foams are preferred. Furthermore, it is preferred according to the invention that the composite comprises at least one region which contains the water-absorbing polymer structure according to the invention in an amount in the range from about 15 to 100% by weight, preferably about 30 to 100% by weight, particularly preferably from about 50 to 99.99 wt .-%, further preferably from about 60 to 99.99 wt .-% and more preferably from about 70 to 99 wt .-%, each based on the total weight of the respective region of the composite includes, said Range preferably has a size of at least 0.01 cm ³ , preferably at least 0.1 cm ³ and most preferably at least 0.5 cm ³ .

In a particularly preferred embodiment of the composite according to the invention it is a sheet-like composite, as described in WO 02/056812 A1 as "absorbent material" Disclosure of WO 02/056812 A1, in particular with regard to the exact structure of the composite, the basis weight of its components and its thickness is hereby introduced as a reference and provides a part of the disclosure of the present invention.

A further contribution to the solution of the abovementioned objects is provided by a process for producing a composite, wherein the water-absorbing polymer structures according to the invention or the surface-treated water-absorbing polymer structures obtainable by the process according to the invention and a substrate and optionally an additive are brought into contact with one another. As a sub strate preferably those substrates are set, which have already been mentioned above in connection with the composite according to the invention.

a Contribution to the solution The input mentioned tasks also provides a bond available after the method described above, this composite preferably has the same properties as the one described above, composite according to the invention.

a further contribution to the solution The tasks mentioned at the beginning provide chemical products the polymer structures of the invention or a composite according to the invention. Preferred chemical products are in particular foams, moldings, fibers, Films, films, cables, sealing materials, liquid-absorbent hygiene articles, in particular diapers and sanitary napkins, carriers for plant or fungi growth regulating Agents or crop protection agents, additives for building materials, packaging materials or soil additives.

Also the use of the polymer structures according to the invention or the composite according to the invention in chemical products, preferably in the above chemical products, especially in hygiene articles such as diapers or sanitary napkins, as well as the use of superabsorbent particles as a carrier for plant or fungi growth regulating agents or crop protection agents deliver a contribution to the solution the tasks mentioned above. When used as a carrier for plant growth or fungi growth regulating agents or crop protection agents it is preferred that the plant or fungi growth regulating Agents or crop protection agents are controlled by the carrier Period can be submitted.

a further contribution to the solution The task mentioned at the beginning provides the use of a combination of a metal salt and an oxide of a metal for treatment the surface water-absorbing polymer structure, preferably for improvement the retention capacity water-absorbing polymer structure, wherein as the metal salt and as Oxide of a metal those compounds are preferred that already Input in connection with the water-absorbing polymer structures according to the invention as preferred components (α4) and (α5) were called.

The Invention will now be based on test methods and not limiting Examples closer explained.

MANUFACTURE OF SAP PARTICLES

A monomer solution consisting of 600 g of acrylic acid, which was neutralized to 70 mol% with sodium hydroxide solution (466.22 g of 50% NaOH), 881.52 g of water, 0.573 g of polyethylene glycol 300 diacrylate, 1.603 g Monoallylpolyethylenglykol-450-monoacrylic acid ester and 17.2 g of polyethylene glycol-750 monomethacrylsäureestermethylether is freed from the dissolved oxygen by purging with nitrogen and cooled to the starting temperature of 4 ° C. After reaching the starting temperature, the initiator solution (0.6 g of sodium peroxydisulfate in 10 g of H ₂ O, 0.014 g of 35% hydrogen peroxide solution in 10 g of H ₂ 0 and 0.03 g of ascorbic acid in 10 g H ₂ 0) was added. After the final temperature of about 100 ° C was reached, the resulting gel was crushed with a meat grinder and dried at 150 ° C for 2 hours in a drying oven. The dried polymer was crushed roughly, ground with a 2 mm sieve by means of a SM 10 granulator and sieved to a powder having a particle size of 150 to 850 μm (= powder A).

COMPARATIVE EXAMPLE (conventional postcrosslinking)

100 g of powder A are mixed with a solution consisting of 1.0 g of ethylene carbonate, 0.2 g of Al ₂ (SO ₄ ) ₃ .times. 14 H ₂ O and 2.5 g of deionized water, the solution being mixed with a syringe using a syringe 0.45 mm cannula was applied to the located in a mixer polymer powder. Subsequently, the powder A coated with the aqueous solution was heated in a circulating air oven at 170 ° C. for 45 minutes. A powder B was obtained.

EXAMPLE 1

A solution of 150 g deionized water, 12 g of Al ₂ (SO _{4) 3} x 14 H ₂ O, 12 g Nanox ^® 200 (zinc oxide powder from Elementis Specialties, USA, having a BET surface area of 17 m ² / g and a average particle size of 60 nm) and 60 g of ethylene carbonate was measured by means of an Ultra Turax to form a dispersion mixed. By means of a syringe with a 0.9 mm cannula, 3.9 g of this suspension are applied to 100 g of the polymer powder A present in a mixer. Subsequently, the powder coated with the suspension A was heated in a circulating air oven at 170 ° C for 45 minutes. A powder C was obtained.

EXAMPLE 2

A solution of 150 g deionized water, 18 g of Al ₂ (SO _{4) 3} x 14 H ₂ O, 18 g Nanox ^® 200 (zinc oxide powder from Elementis Specialties, USA, having a BET surface area of 17 m ² / g and a average particle size of 60 nm) and 60 g of ethylene carbonate was mixed by means of an Ultra Turax to form a dispersion. 4.1 g of this suspension are applied to 100 g of polymer powder A in a mixer by means of a syringe with a 0.9 mm cannula. Subsequently, the powder coated with the suspension A was heated in a circulating air oven at 170 ° C for 45 minutes. A powder D was obtained.

EXAMPLE 3

A solution of 150 g deionized water, 24 g of Al ₂ (SO _{4) 3} x 14 H ₂ O, 30 g Nanox ^® 200 (zinc oxide powder from Elementis Specialties, USA, having a BET surface area of 17 m ² / g and a average particle size of 60 nm) and 60 g of ethylene carbonate was mixed by means of an Ultra Turax to form a dispersion. Using a syringe with a 0.9 mm cannula, 4.4 g of this suspension are applied to 100 g of the polymer powder A present in a mixer. Subsequently, the powder coated with the suspension A was heated in a circulating air oven at 170 ° C for 45 minutes. A powder E was obtained.

The polymer powders have the following absorption properties:

As the above absorption data it is understood, the polymer structures with the metal salt (aluminum sulfate) and the oxide may be a metal of the observed at the surface postcrosslinking waste of the CRC value are reduced visible (Nanox ^® 200) by the inventive surface treatment.

Claims (20)

Water-absorbing polymer structure whose surface with a combination of a metal salt and an oxide of a metal has been brought into contact. Water-absorbing polymer structure according to claim 1, wherein the polymer structure has an R / LA ratio of at least 2.59 g / g ·%. Water-absorbing polymer structure according to claim 1 or 2, wherein the metal salt is a water-soluble metal salt. Water-absorbing polymer structure according to claim 3, wherein the metal salt is a sulfate. Water-absorbing polymer structure according to claim 3 or 4, wherein the metal salt is a salt of a di- or trivalent Metallkations is. Water-absorbing polymer structure according to one of claims 2 to 5, the oxide of the metal is a powdery oxide and wherein at least 50% by weight of the oxide of the metal has a particle size in a range of 10 up to 1,000,000 nm. A water-absorbent polymer structure according to any one of claims 2 to 6, wherein the oxide of the metal is a zinc oxide. Water-absorbing polymer structure according to one of previous claims, wherein polymer structures - one Interior as well - one the surrounding area outside and wherein the outdoor area a higher Has degree of crosslinking than the interior. Process for treating the surface of water-absorbing Polymer structure comprising the method steps i) Provide an untreated, water-absorbing polymer structure; ii) bring the surface into contact of the untreated, water-absorbing polymer structure with a combination of a metal salt and an oxide of a metal at a temperature in a range of 100 to 300 ° C. The method of claim 9, wherein the metal salt and the oxide of the metal in the form of a fluid F ₁ comprising a solvent, the metal salt and the oxide of the metal are brought into contact with the water-absorbing polymer structure. The method of claim 10, wherein the fluid F ₁ additionally comprises a postcrosslinker capable of reacting in a condensation reaction with functional groups of the water absorbing polymer structure. A method according to any one of claims 9 to 11, wherein the metal salt in an amount ranging from 0.001 to 5% by weight, and the oxide the metal in an amount in a range of 0.001 to 5 wt .-%, respectively based on the weight of the untreated, water-absorbing Polymer-formed, with the untreated water-absorbing polymer structure be brought into contact. A method according to any one of claims 9 to 12, wherein the metal salt a salt of aluminum and the oxide of the metal is a zinc oxide. A surface-treated, water-absorbing polymer structure obtainable by a process according to any one of the preceding claims, wherein the polymer structure an R / LA ratio of at least 2.59 g / g ·% having. Composite containing a water-absorbing polymer structure according to one of the claims 1 to 8 or 14 and a substrate. Process for the preparation of a composite, wherein a water-absorbing polymer structure according to one of claims 1 to 8 or 14 and a substrate and optionally an adjuvant with each other be brought into contact. Composite, available according to a method according to claim 16th mousses, Moldings, Fibers, films, films, cables, sealing materials, liquid-absorbent hygiene articles, carrier for plant and fungal growth regulating agents, packaging materials, bottom additives or Building materials include the water-absorbing polymer structure one of the claims 1 to 8 or 14 or the composite according to claim 15 or 17. Use of the water-absorbing polymer structure according to one of the claims 1 to 8 or 14 or the composite according to claim 15 or 17 in foams, moldings, fibers, Films, films, cables, sealing materials, liquid-absorbent hygiene articles, carriers for plant and fungal growth regulating agents, packaging materials, soil additives, for controlled release of active substances or in building materials. Use of a combination of an oxide of a Metal and a metal salt for treating the surface of superabsorbent Polymer structure.