TW201329113A - Process for the continuous preparation of water-absorbent polymers - Google Patents

Abstract

The invention relates generally to a process for the preparation of water-absorbent polymer particles, comprising the process steps of (i) preparing an aqueous monomer solution comprising at least partially neutralized, monoethylenically unsaturated monomers bearing carboxylic acid groups ( &agr; 1) and at least one crosslinker ( &agr; 3); (ii) optionally adding fine particles of a water-absorbent polymer or aqueous salt solutions to the aqueous monomer solution; (iii) adding a polymerization initiator or at least one component of a polymerization initiator system that comprises two or more components to the aqueous monomer solution; (iv) decreasing the oxygen content of the aqueous monomer solution; (v) charging the aqueous monomer solution into a polymerization reactor; (vi) polymerizing the monomers in the aqueous monomer solution in the polymerization reactor, thereby obtaining a polymer gel; (vii) discharging the polymer gel out of the polymerization reactor and optionally comminuting the polymer gel thereby obtaining polymer gel particles; (viii) drying the polymer gel particles; (ix) grinding the dried polymer gel particles thereby obtaining particulate water-absorbent polymer particles; (x) sizing the grinded water-absorbent polymer particles; and (xi) crosslinking the surface of the grinded and sized water-absorbent polymer particles; wherein process step (xi) comprises the steps of: (x1a) mixing the particles with an aqueous crosslinker solution; and (x2a) heat-treating the mixture obtained in process step (x1a) in a horizontally operated mixing device, wherein the horizontally operated mixing device is hydraulically driven.

Description

Method for continuously preparing water-absorbing polymer

The present invention relates to a method for preparing a water-absorbing polymer particle, a water-absorbent polymer particle obtainable by the method, a composite material, a method for preparing the composite material, and a composite material obtained by the method, a chemical product, and Use of water-absorbing polymer particles or composite materials.

Superabsorbers are water-insoluble cross-linked polymers that absorb large amounts of aqueous liquids, especially body fluids, especially urine or blood, which swell and form hydrogels, and can be under certain pressures. Keep these liquids. Due to these peculiar properties, these polymers are primarily used for incorporation into sanitary articles such as diapers, incontinence products or sanitary towels for infants.

The preparation of the superabsorbent is usually carried out by radical polymerization of a monomer having an acid group in the presence of a crosslinking agent, wherein the permeable monomer composition, the crosslinking agent, the polymerization conditions are selected, and the polymerization is carried out. The processing conditions of the hydrogel obtained after the reaction are selected to prepare polymers having different absorber properties (for details, refer to, for example, " Modern Superabsorbent Polymer Technology ", FL Buchholz , GT Graham , Wiley-VCH , 1998 ).

The monomer bearing an acid group can be polymerized in a batch process or a continuous process in the presence of a crosslinking agent. No. 4,857,610 discloses a continuous process for preparing superabsorbents. According to this method, the monomer having an acid group and the crosslinking agent are continuously loaded into a layer of at least one centimeter thick on a moving endless conveyor belt and polymerized, thereby obtaining a gel system. The discharge is continuously carried out from the conveyor belt, followed by comminute, drying, sieving and optionally surface treatment.

The surface treatment of the water-absorbing polymer particles generally comprises a surface crosslinking step in which the polymer particles are first mixed with an aqueous solution comprising a surface crosslinking agent, and wherein the resulting mixture is then mixed in another mixture. The heat treatment in the apparatus is preferably carried out in a horizontally operated mixing apparatus such as an electrically driven NARA-mixer. However, in order to obtain water-absorbing polymer particles having predictable and reproducible absorption characteristics, it is very important to control the residence time of the polymer particles in the NARA-mixer. However, a disadvantage of the prior art method is that if the NARA-mixer has to be stopped due to, for example, a particular overload or for other reasons, it is very difficult to restart the mixer in a fully loaded state, especially if the wet polymer The fluidity of the particles is lowered by the presence of an additive such as an aluminum salt. In the electrically driven NARA-mixer aspect, the maximum torque cannot be reached immediately upon restarting the mixer, with the result that the polymer particles are not sufficiently mixed at the beginning of the restart. This is tantamount to the problem of restarting the NARA-mixer, resulting in an unpredictable extension of the residence time of the polymer particles in the NARA-mixer and thus to unpredictable absorption characteristics of the final product. When the inner surface of the NARA-mixer is heated, the polymer particles may even burn if they are in contact with such surfaces for an extended period of time.

It is an object of the present invention to overcome at least some of the above mentioned disadvantages of the prior art. Another object of the present invention is to provide a process for preparing water-absorbing polymer particles in a manner effective in both time and resources. Still another object of the present invention is to carry out a method of treating the surface of a water-absorbing polymer particle, particularly a method of crosslinking a surface of a water-absorbing polymer particle, under more reproducible conditions. A further object of the present invention is to provide a continuous process for treating the surface of water-absorbing polymer particles, especially the surface of cross-linked water-absorbing polymer particles, which can be performed more efficiently, for example, which can be more easily stopped and restarted. start up. The method should also uniformly mix the additive with the water-absorbing polymer particles, which additive generally has a negative impact on the fluidity of the mixture.

The contribution of the solution to the above object is achieved by a method for preparing a water-absorbing polymer particle, which comprises the following method steps: (i) preparing an aqueous monomer solution comprising at least partially neutralized monoethylenically unsaturated monomer (α1) having a carboxylic acid group and at least one crosslinking agent (α3) (ii) adding a fine particle of a water-absorbing polymer to the aqueous monomer solution as needed; (iii) adding a polymerization initiator or at least one component of a polymerization initiator system containing two or more components To the aqueous monomer solution; (iv) reducing the oxygen content of the aqueous monomer solution; (v) loading the aqueous monomer solution into a polymerization reactor; (vi) polymerizing the aqueous monomer in the polymerization reactor a monomer in the monomer solution to obtain a polymer gel; (vii) discharging the polymer gel out of the polymerization reactor, and if necessary, gelling the finely divided polymer to obtain polymer gel particles; Viii) drying the polymer gel particles; (ix) grinding the dried polymer gel particles to obtain particulate water-absorbing polymer particles; (x) sizing the ground water absorption Polymeric particles; and (xi) cross-linking the ground and sieved water-absorbing polymer particles The method step (xi) comprises the steps of: (x1a) mixing the particles with an aqueous crosslinking agent solution; and (x2a) heat treating the method step (x1a) in a horizontally operated mixing device. A mixture wherein the horizontally operated mixing device is hydraulically driven.

1‧‧‧ horizontally operated mixing device

2‧‧‧Axis

3‧‧‧Pipe blades

4‧‧‧ fill level

5‧‧‧Adjustable gap堰

6‧‧‧Inlay gear

7‧‧‧In-line gears driven directly in hydraulic form

8‧‧‧ slots

9‧‧‧Polymerization zone

10‧‧‧Dry area

11‧‧‧Making and screening sections

12‧‧‧Surface cross-section

13‧‧‧First Mixer

Figure 1 is a schematic cross-sectional view of a mixing apparatus suitable for horizontal operation in accordance with one of the methods of the present invention.

Figure 2 is a schematic cross-sectional view of another suitable for horizontally operating a mixing device in accordance with one of the methods of the present invention.

Figure 3 is a schematic cross-sectional view of a horizontally operating mixing device suitable for use in accordance with one of the methods of the present invention, wherein the paddle shaft is driven directly at hydraulic pressure via the insert gear.

Figure 4 is a flow chart of the method according to the invention.

The process of the present invention is preferably a continuous process wherein the aqueous monomer solution is continuously supplied and continuously fed to the polymerization reactor. The hydrogel obtained is continuously discharged from the polymer reactor and continuously finely chopped, dried, ground and classified in subsequent process steps. However, this continuous process can also be interrupted, for example for the following purposes: - when replacing a particular component of the process equipment, such as a belt of a conveyor belt when a conveyor belt is used as a polymerization reactor; - when cleaning a particular part of the equipment , especially in order to remove polymer precipitates in the tank or in the tube; or - when it is necessary to prepare water-absorbent polymer particles with other absorption properties to start a new process.

Preferred water-absorbing polymer particles according to the present invention have a thickness of 10 to 3,000 μm, preferably 20 to 2,000 μm, and particularly preferably 150 to 850 μm according to WSP 220.2 (" Word Strategic Partners " EDANA and INDA test methods). Average particle size. Here, it is particularly preferred that the content of the polymer particles having a particle size of 300 to 600 μm is at least 30% by weight, particularly preferably at least 40% by weight and most preferably at least the total weight of the water-absorbing polymer particles. 50% by weight.

In step (i) of the process according to the process of the invention, a monoethylenically unsaturated monomer (α1) having at least partially neutralized carboxylic acid groups and at least one crosslinking agent (α3) is prepared. Aqueous monomer solution.

A preferred monoethylenically unsaturated monomer (?1) having a carboxylic acid group is contained in DE 102 23 060 A1 as a preferred monomer (?1), and particularly preferably acrylic acid.

According to a preferred embodiment of the invention, the water-absorbing polymer obtained by the process according to the invention comprises, by dry weight thereof, at least 50% by weight, preferably at least 70% by weight and more preferably at least 90% by weight. A monomer of a carboxylic acid group. It is especially preferred according to the invention that the water-absorbing polymer obtained by the process according to the invention is At least 50% by weight, preferably at least 70% by weight, of acrylic acid is formed, preferably neutralized to at least 20% by mole, particularly preferably at least 50% by mole. The content of the at least partially neutralized monoethylenically unsaturated monomer having a carboxylic acid group (α1) in the aqueous monomer solution provided in process step (i), based on the total weight of the aqueous monomer solution It is preferably 10 to 60% by weight, more preferably 20 to 50% by weight, and most preferably 30 to 40% by weight.

The aqueous monomer solution may also contain a monoethylenically unsaturated monomer (α2) which is copolymerizable with (α1). Preferred monomers (?2) are those preferred as the preferred monomer (?2) as DE 102 23 060 A1, and more preferably acrylaimde.

The preferred crosslinking agent (α3) according to the invention is a compound having at least two vinyl-type unsaturated groups in one molecule (crosslinking agent type I); having at least two compounds which can be condensed (= condensation a compound (crosslinking type II) which reacts with a functional group of a monomer (α1) or (α2) in an addition reaction or a ring-opening reaction; has at least one vinyl type a saturated group and at least one compound (crosslinking agent type III) capable of reacting with a functional group of a monomer (α1) or (α2) in a condensation reaction, an addition reaction or a ring opening reaction; or Multivalent metal cation (crosslinker type IV). Thus, in the case of the compound of the crosslinking type I, the crosslinking of the polymer is via the radical polymerization of the vinyl-type unsaturated group of the crosslinking agent molecule and the ethylenically unsaturated monomer (α1) or (α2). When the reaction is carried out; and in the case of the compound of the crosslinking type II and the polyvalent metal cation of the crosslinking agent type IV, the crosslinking of the polymer is respectively transmitted through the condensation reaction of the functional group (crosslinking agent type II) or by multivalent The electrostatic interaction of the metal cation (crosslinker type IV) with the functional group of the monomer (α1) or (α2) is achieved. In the case of a compound of the crosslinking type III, the crosslinking of the polymer is by a radical polymerization of a vinyl-type unsaturated group and a functional group of a crosslinking agent and a functional group of the monomer (α1) or (α2) The condensation reaction between the groups is achieved accordingly.

Preferred crosslinkers (α3) are compounds of the crosslinkers (α3) as crosslinkers of the type I, II, III and IV described in DE 102 23 060 A1, wherein: - as crosslinker type I Compound, N, N'-methylene bisacrylamide, polyethyleneglycol di(meth)acrylates, tripropylene hydride Methylammonium chloride, tetraallylammonium chloride, and allylnona-ethyleneglycol acrylate obtained by using 9 moles of ethylene oxide per mole of acrylic acid Particularly preferred; and - as a compound of the crosslinking agent type IV, Al ₂ (SO ₄ ) ₃ and a hydrate thereof are particularly preferred.

Preferred water-absorbent polymers prepared according to the process of the present invention are each crosslinked by a crosslinking agent type or a crosslinking agent which is combined by the following crosslinking agent types: I, II, III, IV , I/II, I/II, I/III, I/IV, I/II/III, I/II/IV, I/III/IV, II/III/IV, II/IV or III/IV.

More preferred water-absorbing polymers obtained by the process according to the invention are polymers obtained by crosslinking any of the crosslinking agents described in DE 102 23 060 A1, wherein A crosslinking agent of the agent type I, particularly preferably N, N'-methylene bisacrylamide, polyethylene glycol di(meth) acrylate (polyethyleneglycol di (meth) Acrylate), triallylmethylammonium chloride, tetraallylammonium chloride, and acrylic propylene hexaethylene 2 using 9 moles of ethylene oxide per mole of acrylic acid Aldlnonaethylene-glycol acrylate.

The aqueous monomer solution may further comprise a water soluble polymer (α4). Preferred water-soluble polymers (α4) include partially or fully saponified polyvinyl alcohol, polyvinylpyrrolidone, starch or starch derivatives, polyethylene glycol or polyacrylic acid. The molecular weight of these polymers is not critical as long as it is water soluble. Preferred water-soluble polymer (α4) is a starch or starch derivative and polyethylene glycol. The water-soluble polymer (α4), preferably a synthetic water-soluble polymer (such as polyethylene glycol), can serve not only as a graft base of the monomer to be polymerized, but also can cause these water-soluble polymers to be coagulated with water. The glue or the already dried water-absorbing polymer is mixed.

The aqueous monomer solution may further comprise auxiliary substances (α5), which in particular comprise a complexing agent such as EDTA.

Preferably, the relative amounts of the monomers (α1) and (α2) and the crosslinking agent (α3) and the water-soluble polymer (α4) and the auxiliary substance (α5) in the aqueous monomer solution are selected so that the method after drying The water-absorbing polymer structure obtained in step x) is based on the following: - in the range of from 20 to 99.999 wt%, preferably from 55 to 98.99 wt%, particularly preferably from 70 to 98.79 wt% in the monomer (α1); In the monomer (α2), up to 0 to 80% by weight, preferably 0 to 44.99% by weight, particularly preferably in the range of 0.1 to 44.89% by weight; - in the crosslinking agent (α3), up to 0 to 5% by weight, Preferably in the range of 0.001 to 3% by weight, particularly preferably 0.01 to 2.5% by weight; - in the water-soluble polymer (α4), up to 0 to 30% by weight, preferably 0 to 5% by weight, particularly preferably 0.1 to 5 by weight a range of %; - in the auxiliary substance (α5), in the range of 0 to 20% by weight, preferably 0 to 10% by weight, particularly preferably 0.1 to 8% by weight; and - in water (α6), up to 0.5 to 25 The weight %, preferably 1 to 10% by weight, particularly preferably 3 to 7% by weight, and the total weight of (α1) to (α6) is 100% by weight.

The optimum values for the concentration of the monomers, crosslinkers and water-soluble polymers in the monomer solution can be determined by simple pre-experiment or from prior art, in particular the following publications: US 4,286,082, DE 27 06 135 A1, US 4,076,663, DE 35 03 458 A1, DE 40 20 780 C1, DE 42 44 548 A1, DE 43 33 056 A1 and DE 44 18 818 A1.

In method step (ii), a water-absorbing polymer fine particle or an aqueous salt solution may be added to the aqueous monomer solution as needed.

The water-absorbent fine particles are preferably water-absorbent polymer particles, and the composition of the water-absorbing particles corresponds to the composition of the aforementioned water-absorbing polymer particles, wherein at least 90% by weight of the water-absorbent fine particles, more preferably 95% by weight, of the water-absorbing particles are preferable. The fine fine particles and preferably 99% by weight of the water-absorbing fine particles have a thickness of less than 200 μm, preferably less than 150 μm. The size of the particles is preferably less than 100 microns. The water-absorbing fine particles may also contain a metal salt, especially an aluminum salt.

In a preferred embodiment of the process according to the invention, the water-absorbing fine particles which can be added to the aqueous monomer solution, if desired in process step (ii), are obtained in step (x) of the process according to the process of the invention. And thus the fine particles recovered.

The fine particles can be added to the aqueous monomer solution by any mixing device deemed suitable for this purpose by those skilled in the art. In a preferred embodiment of the present invention, the fine particles are added to the aqueous monomer solution in a mixing device, wherein the first stream of the fine particles and the second stream of the aqueous monomer solution are continuously but introduced in different directions. On a rotary mixing device, this is particularly effective in that the process is carried out continuously as described above. This hybrid arrangement can be implemented in a "Rotor Stator Mixer" which includes a preferably cylindrical non-rotating stator in the mixing zone and a likewise preferably cylindrical rotor (rotor) rotates at its center. The rotor wall and the stator wall usually have scores, such as groove-like nicks, which absorb the mixture of fine particles and aqueous monomer solution through the score and thereby withstand high shear.

Here, it is particularly preferred that the first stream of the fine particles and the second stream of the aqueous monomer solution form an angle δ of 60 to 120°, preferably 75 to 105°, and even more preferably 85. Up to 95°, and most preferably about 90°. Also preferably, the mixture of fine particles leaving the mixer and the aqueous monomer solution flows at an angle ε to the first stream of fine particles entering the mixer, which is 60 to 120°, preferably 75 to 105. °, even more preferably 85 to 95°, and most preferably about 90°.

Such a hybrid arrangement can be achieved, for example, by the mixing device disclosed in DE-A-25 20 788 and DE-A-26 17 612, the disclosure of which is incorporated herein by reference. Specific examples which can be used to add fine particles to the aqueous monomer solution in step (ii) of the process of the invention are available from ISTA ^® Werke GmbH & Co. KG, Germany, under the name MHD 2000/4, MHD 2000/05 MHD 2000/10, MDH 2000/20, MHD 2000/30 and MHD 2000/50, among which the hybrid device MDH 2000/20 is better. Other available mixing devices are those supplied by German ystral GmbH, Ballrechten-Dottingen, for example, the name "Conti TDS", or the trademark of Megatron ^® by Kinematika AG, Switzerland.

The amount of fine particles which may be added to the aqueous monomer solution in the method step (ii) is preferably from 0.1 to 15% by weight, more preferably from 0.5 to 10% by weight and most preferably 3, based on the weight of the aqueous monomer solution. Up to 8% by weight.

As the aqueous salt solution which can be added to the aqueous monomer solution in the method step (ii), an aqueous solution containing a carbonate can be used. Such solutions can be obtained in the form of so-called "scrubber water" as disclosed in US 2011/0245436 A.

In step (iii) of the process of the present invention, a polymerization initiator or at least one component of a polymerization initiator system comprising two or more components is added to the aqueous monomer solution.

As the polymerization initiator for the initial polymerization, all of the initiators which form radicals under the polymerization conditions can be used, which are commonly used for the preparation of superabsorbents. In these cases of thermal catalysts, redox catalysts and photoinitiators, the activation occurs through energy radiation. The polymerization initiator may be dissolved or dispersed in the aqueous monomer solution to preferably use a water-soluble catalyst.

As the thermal initiator, all compounds known to those skilled in the art to decompose to form free radicals under the action of temperature can be used. Particularly preferred is a thermal polymerization initiator which has a half-life of less than 180 ° C, preferably less than 140 ° C, of 10 seconds, more preferably 5 seconds. Particularly preferred thermal polymerization initiators are peroxides, hydroperoxides, hydrogen peroxide, persulphates and azo compounds. In some cases, it is advantageous to use a mixture of various thermal polymerization initiators. Among these mixtures, those composed of hydrogen peroxide and sodium peroxodisulfate or potassium are preferably used in any desired ratio. Suitable organic peroxides are preferably acetamidineacetone, methyl ethyl ketone peroxide, benzoyl peroxide, laurel, ruthenium peroxide, ruthenium peroxide, diisopropyl peroxydicarbonate. Ester, di(2-ethylhexyl)peroxydicarbonate, tert-butyl hydroperoxide, cumene hydroperoxide, tert-amyl perpivalate, trimethyl peroxidate Tert.-butyl perpivalate, tert.-butyl perneohexonate, tert-butyl isobutyrate, tertiary butyl peroxy-2-ethylhexanoate Tert.-butyl per-2-ethylhexanoate, tert-butyl peroxydecanoate, tert.-butyl permaleate, tert-butyl perbenzoate, 3 , 5,5-trimethylhexanoic acid, tertiary butyl ester, and amyl perneodecanoate. Further, the following thermal polymerization initiators are preferred: azo compounds such as azo-bis-isobutyronitrole, azo-bis-dimethylvaleronitrile (azo-bis-) Dimethylvaleronitrile), 2,2-azobis-(2-amidinopropane) dihydrochloride, azo-bis-methylpropyl hydrazine Azo-bis-amidinopropane dihydrochloride, 2,2'-azo-bis-(N,N-dimethylene)diisobutylphosphonium dihydrochloride (2,2 ' -azo- Bis-(N,N-dimethylene)isobutyramidine di-hydro-chloride), 2-(carbamoylazo)isobutyronitrile and 4,4'-azo-bis-( 4-cyano - valeric acid) (4,4 '-azo-bis- ( 4-cyano-valeric acid)). The above compounds are used in a conventional amount, preferably from 0.01 to 5, more preferably from about 0.1 to 2 mol%, based on the amount of the monomer to be polymerized.

The redox catalyst comprises two or more components, usually one or more of the above peroxy compounds and at least one reducing component, preferably ascorbic acid; glucose; saponose; mannose; ammonium or alkali metal Bisulfite, sulfate, thiosulfate, hyposulfite, or sulfide; metal salts such as divalent iron or silver ions; or sodium hydroxymethyl sulfoxylate. Preferably, ascorbic acid or sodium metabisulfite is used as a reducing component of the redox catalyst. The amount of the reducing component of the redox catalyst is from 1 × 10 ^-5 to 1 mol%, and the amount of the oxidizing component of the redox catalyst is from 1 × 10 ^-5 to 5 mol%, with reference to the amount of the monomer used in the polymerization reaction. . One or more azo compounds, preferably water-soluble, may be used in place of or as a complement to the oxidizing component of the redox catalyst.

If the polymerization reaction is initiated by the action of an energy beam, a so-called photoinitiator is usually used as the initiator. This may comprise, for example, so-called alpha-splitters, H-abstracting systems or azides. Examples of such starters are diphenyl ketone derivatives (e.g., micones), phenanthrene derivatives, fluorine derivatives, anthraquinone derivatives, isopropyl thioxene Keto derivative (thioxanthone derivatives), coumarin derivatives, benzoinether and its derivatives, azo compounds (such as the aforementioned radical formers), substituted six Alkeny hexaarylbisimidazoles or acylphosphine oxides. An example of an azide is 2-(N,N-dimethylamino)ethyl-4-azidocinnamate, 2-(N(N, N-dimethylamino)ethyl-4-azidocinnamate) N,N-Dimethylamino)ethyl-4-azidonaphthylketone (2-(N,N-dimethylamino)ethyl-4-azidonaphthylketone), 2-(N,N-di-methylamine) 2-(N,N-di-methylaminoethyl-4-azidobenzoate), 5-azido-1-naphthyl-2'-(N, N-(Dimethylamino)ethylsulfone, N-(4-sulfonyl azidophenyl) malazone N-(4-sulfonylazidophenyl)maleinimide, N-acetyl-4-sulfonyl-azidoaniline, 4-sulfonyl-azidoani 4-sulfonylazidoaniline, 4-azidoaniline, 4-azidophenacyl bromide, p-azidobenzoic acid, 2,6-bis(p-azidobenzylidene)cyclohexanone and 2,6-bis(p-azidophenylene)-4- Methylcyclohexanone (2,6-bis(p-azidobenzylidene)-4-methylcyclohexanone). The photoinitiator is generally used in an amount of from 0.01 to 5% by weight based on the monomer to be polymerized.

A particularly preferred redox system for use in the process according to the invention is a redox system comprising hydrogen peroxide, sodium peroxodisulfate and ascorbic acid.

Here, it should also be noted that the polymer reaction initiator can be added before, during or after the method step (iv) (i.e., after the oxygen content of the aqueous monomer solution is reduced). If a polymerization initiator system comprising two or more components, such as a preferred initiator system comprising hydrogen peroxide, sodium peroxodisulfate and ascorbic acid and which is active only after the addition of all components, is used, (iv) previously adding, for example, one or more of the components of the polymerization initiator system, but after process step (iv) or even process step (v), additional ingredients necessary to complete the polymerization initiator system are added.

In step (iv) of the process according to the method of the invention, the reduction of the aqueous single The oxygen content of the bulk solution should be such that process step (iv) can also be carried out before, during or after process step (ii). Preferably, the oxygen content of the aqueous monomer solution is reduced after the fine particles have been added in process step (ii).

The oxygen content of the aqueous monomer solution is reduced by contacting the aqueous monomer solution with an inert gas such as nitrogen. The inert gas phase in contact with the aqueous monomer solution does not contain oxygen and is therefore characterized by a very low partial pressure of oxygen, whereby oxygen is transferred from the aqueous monomer solution to the inert gas phase until the aqueous monomer solution and inert gas The partial pressure of oxygen in the phase is equal. The aqueous monomer phase can be brought into contact with the inert gas, for example, by introducing an inert gas bubble into the monomer solution at a cocurrent, countercurrent or intermediate entry angle. Good mixing can be achieved, for example, by nozzles, static or dynamic mixers or bubble columns. The oxygen content of the monomer solution prior to the polymerization is preferably reduced to less than 1 ppm by weight, more preferably less than 0.5 ppm by weight.

In step (v) of the process according to the process of the invention, the aqueous monomer solution is charged into a polymerization reactor, preferably into a conveyor belt, particularly preferably upstream of the conveyor belt, and in the method step ( In vi), the monomer in the aqueous monomer solution is polymerized in a polymerization reactor to obtain a polymer gel. If the polymerization is carried out on a polymerization belt as a polymer reactor, a polymer gel is obtained downstream of the conveyor belt, which is preferably finely divided before drying to obtain gel particles.

Any reactor known to those skilled in the art to be suitable for continuous or batch polymerization of monomers such as acrylic acid in an aqueous solution can be used as the polymerization reactor. An example of a suitable polymerization reactor is a kneading reactor. In a kneading machine, the polymer gel formed by the polymerization of the aqueous monomer solution is continuously finely divided by, for example, a counter-rotating stirring shaft, as described in WO 2001/38402.

Another example of a preferred polymerization reactor is a conveyor belt. Anyone skilled in the art would be considered suitable as a support material on which the aqueous monomer solution can be injected and subsequently polymerized to form a hydrogel, as a conveyor belt suitable for use in the method according to the invention. Examples of conveyor belts that can be used in the process of the invention are disclosed in DE-A-35 44 770, EP-A-0 955 086 and EP-A-1 683 813, the disclosure of which is incorporated herein by reference. And here for reference.

The conveyor belt typically includes a cyclically moving conveyor belt through the support member and at least two conductive rollers that drive at least one of the conductive rollers and are configured to be adjustable. Optionally, a scrolling and feeding system for the release sheet that can be used for the upper surface section of the conveyor belt is provided. The system comprises a feeding and metering system for the reaction component, and a radiation tool disposed in the direction of movement of the conveyor belt, after the supply and metering system, and a cooling and heating device, and a device for transporting A removal system for polymer gel bundles near the transfer roller for return. In order to carry out the polymerization in the highest possible space-time yield, according to the invention, there is an upward extension in the vicinity of the upper section of the conveyor belt, on both sides of the horizontal support element, in the region of the beginning of the feeding and metering system The support members have their longitudinal axes intersecting at a point below the upper run and which shape the supported conveyor belt to be suitable for a suitable groove shape. Therefore, according to the present invention, the conveyor belt is supported by a plurality of groove-like supports and load-bearing members in the vicinity of the feeding system of the reaction components, and the support and the carrier member form a deep groove or disk-like structure. Shaped for the reaction components introduced. The desired shape of the groove depends on the shape and arrangement of the support member over the length of the upper stroke. The support elements must be relatively close to each other in the region where the reaction components are introduced, and in the subsequent regions, the placement of the support members can be slightly separated after the initial polymerization reaction. The angle of inclination of the support member and the cross-section of the support member can be varied such that the initial deep groove flattens toward the end of the polymerization section and is again brought into an extended state. In another embodiment of the invention, each support member is preferably formed by a cylindrical or spherical roller that is rotatable along its longitudinal axis. The cross-sectional shape of the desired groove can be easily achieved by varying the cross section of the roller and the configuration of the roller. In order to ensure proper groove formation via the conveyor belt, it is preferred that the conveyor belt be stretchable both in the longitudinal and transverse directions as the conveyor belt transitions from a flat to a groove-like shape and back to a flat shape.

In step (vii) of the process according to the process of the invention, the particulate polymer gel obtained in the polymerization reactor (preferably the polymer gel particles obtained in the kneading reactor or downstream of the conveyor belt) Part of the obtained polymer gel bundle) exits the reactor and is (further) finely divided, especially in a conveyor belt. The case of the gel bundle to obtain polymer gel particles. Preferably, the resulting polymer gel bundle is removed from the conveyor belt in the form of a continuous bundle having a soft semi-solid consistency and then passed through for further processing such as comminution.

The finely divided polymer gel bundle is preferably carried out in at least three steps: - in the first step, a cutting unit, preferably a cutter as disclosed in WO-A-96/36464, is used to The polymer gel bundle is cut into flat gel strips, preferably from 5 to 500 mm, preferably from 10 to 300 mm and especially from 100 to 200 mm, and from 1 to 30 mm, preferably from 5 to 25 in length. Typically, it is 10 to 20 mm, and the width is 1 to 500 mm, preferably 5 to 250 mm, and particularly preferably 10 to 200 mm; in the second step, all the broken units are used, preferably one. The crusher cuts the gel strip into a gel sheet, preferably having a length of 1 to 25 mm, preferably 1 to 12.5 mm, a height of 0.25 to 15 mm, preferably 0.25 to 7.5 mm, and a width 0.25 to 20 mm, preferably 0.25 to 10 mm; and - in the third step, using a "Wofu" (grinding) unit, preferably a Wolf, preferably having a feed screw and a hole plate Thereby the feed screw is transported relative to the orifice plate to grind and crush the gel sheet into polymer gel particles, preferably less than the gel sheet

An optimum surface-to-volume ratio is achieved here, which has a favourable effect on the drying behaviour of process step (viii). A gel that is finely divided in this manner is especially suitable for belt drying. The three-step smashing provides a preferred "airability" because of the air passage between the granulated kernels.

The polymer gel particles are dried in step (viii) of the process according to the process of the invention.

Drying of the polymer gel can be carried out by any dryer or oven known to those skilled in the art as being suitable for drying the above gel particles. For example: rotary tube furnaces, fluidized bed dryers, disk dryers, paddle dryers, and infrared dryers.

Especially preferred is a belt drying gas. The belt dryer is a pair of flow systems that are dry, providing a particularly gentle treatment of through-airable products. The product to be dried is placed on a circulating conveyor belt through which the gas can pass, and is subjected to a heated gas stream, preferably air. The drying gas is recycled so that it can become highly saturated during repeated passage through the product layer. a certain portion of the drying gas, preferably not less than 10% per stroke, and not less than 15% An optimum amount of gas of not less than 20%, and preferably up to 50%, more up to 40% and most preferably up to 30%, leaves the dryer in the form of highly saturated vapor and carries away the amount of water evaporated by the product. The temperature of the heated gas stream is preferably not lower than 50 ° C, further lower than 100 ° C and most preferably not lower than 150 ° C, and preferably at most 250 ° C, more preferably at most 220 ° C and most preferably at most 200 ° C.

The size and design of the dryer depends on the product to be treated, the manufacturing capacity and the drying load. Belt dryers can be embodied as single belt, multiple belt, multi-stage or multistory systems. The invention is preferably practiced using a belt dryer having at least one belt, with a single belt dryer being especially preferred. To ensure optimal performance of the belt drying operation, the drying properties of the water-absorbing polymer are each determined as a function of the method variable chosen. The pore size and mesh size of the tape are consistent with the product. Similarly, specific surface strengthening such as electropolishing or Teflonizing is possible.

The polymer gel particles to be dried are preferably applied to the belt of the belt dryer via a rotating belt. The feed height (ie, the vertical distance between the belt of the belt and the belt dryer) is preferably not less than 10 cm, more preferably not less than 20 cm, and most preferably not less than 30 cm, and preferably at most 200 The centimeters are better at up to 120 cm and the best is up to 40 cm. The thickness of the dried polymer gel particles on the belt dryer is preferably not less than 2 cm, more preferably not less than 5 cm, and most preferably not less than 8 cm, and preferably not more than 20 cm. Better not more than 15 cm, and the best is no more than 12 cm. The belt dryer has a belt speed of preferably not less than 0.005 m/s, more preferably not less than 0.01 m/s, and most preferably not less than 0.015 m/sec, and preferably at most 0.05 m/s. , preferably up to 0.03 meters / sec, and the best is at most 0.025 meters / sec.

Further, according to the present invention, the polymer gel particles are preferably dried to a water content of from 0.5 to 25% by weight, preferably from 1 to 10% by weight, and particularly preferably from 3 to 7% by weight.

In step (ix) of the process according to the process of the invention, the dried polymer gel particles are ground to obtain particulate water-absorbing polymer particles.

Grinding of the polymer gel can be carried out by any means known to those skilled in the art as being suitable for milling the above dried polymer particles. An example of a suitable grinding apparatus may be a single or multi-stage roll mill (preferably a two or three stage roll mill), a pin mill, a hammer mill or a vibratory mill.

In step (x) of the process according to the process of the invention, the ground water-absorbing polymer particles are sieved, preferably using suitable sieve plates. Here, especially preferred, for screening After the water-absorbing polymer particles, the polymer particles have a particle size of less than 150 μm, less than 10% by weight, preferably less than 8% by weight, and especially less than 6% by weight, and a particle size of more than 850 μm. It is also less than 10% by weight, preferably less than 8% by weight, and especially less than 6% by weight. It is also preferred that after absorbing the water-absorbing polymer particles, the total weight of the water-absorbing polymer particles is at least 30% by weight, more preferably at least 40% by weight, and most preferably at least 50% by weight is from 300 to 600 microns. Particle size.

In step (xi) of the process according to the process of the invention, the surface of the ground and sieved water-absorbing polymer particles is crosslinked. Any means known to those skilled in the art to be suitable for this purpose may be used as a means of crosslinking the surface of the water-absorbing polymer particles. Preferably, the components (crosslinking agents, water-soluble salts) employed to treat the surface of the polymer particles are added to the water-absorbing polymer particles in the form of an aqueous solution. After the particles are mixed with the aqueous solution, they are heated to a temperature of from 150 to 230 ° C, preferably from 160 to 200 ° C, to promote surface crosslinking reaction.

The method according to the method of the present invention, characterized in that the method step (xi) comprises the steps of: (x1a) mixing the particles with an aqueous crosslinking agent solution; and (x2a) heat treating the method in a horizontally operated mixing device The mixture obtained in the step (x1a), wherein the horizontally operated mixing device is hydraulically driven.

The term "horizontal operation mixing device" as used herein refers to a mixing device in which the central axis of rotation (ie, the central axis of rotation of the rotating member of the mixing device) is substantially parallel to the ground, and wherein the mixture is tied in the mixer to be parallel It is transported in the direction of the rotating central axis. However, the central axis can also be inclined by up to ±10 degrees with respect to the ground, preferably by up to ±5 degrees.

In order to crosslink the water-absorbing polymer particles after grinding and sieving, the particles are mixed with an aqueous crosslinking agent solution. The aqueous crosslinking agent solution comprises, in addition to water as a solvent, a surface crosslinking agent (for example, an alkyl carbonate such as an ethyl carbonate, a polyol such as glycerol, or a glycol such as ethylene glycol. An epoxide of an epoxy glyceryl ether), and optionally additional additives such as aluminum salts, especially aluminum sulfate and/or aluminum lactate. Here, it is preferred that the amount of water used in the operation step (x1a) is not more than 16% by weight, preferably not more than 12% by weight, and preferably not more than 8% by weight based on the weight of the water-absorbing polymer particles. %. When at least 50% by body, preferably at least 70% by weight, More preferably, at least 90% by weight of the water-absorbing polymer particles are contacted with the aqueous crosslinking agent solution during the mixing operation of operation step (x1a), i.e., a suitable mixing is achieved.

Preferably, the mixing of the water-absorbing polymer particles with the crosslinking agent solution can be carried out in a mixing device different from the horizontal operation of the mixing device used in the operating step (x2a), or used in the operation step (x2a). Mixing is carried out in a horizontally operated mixing device. However, it is preferred to use a mixing device different from the mixing device operated at the level used in the operating step (x2a). This mixing device is hereinafter referred to as the "first mixing device" and is distinguished from the horizontally operated mixing device used in the operating step (x2a). An example of a suitable first mixing device is the so-called "Schugi"-mixer.

The first mixing device and the horizontally operated mixing device are continuously operable, that is, both mixing devices have a product inlet to continuously water-absorbent polymer particles (for the first mixing device) or in operation step (x1a) The resulting mixture (for a horizontally operated mixing device) is introduced, and a product outlet for the mixture obtained in operation step (x1a) (for the first mixing device) or the heat-treated water-absorbing polymer particles (for this level) The operating mixing device) leaves the mixing device.

The horizontally operated mixing device can be part of the first mixing device. For example, the horizontally operated mixing device can be directly or indirectly connected to the first mixing device. The connection may be established via a tool that is part of the first mixing device or the horizontally operated mixing device, for example, a conveyor belt that extends at least from the first mixing device to the horizontally operating mixing device. Of course, it is also possible (and preferably also preferred) to position the first mixing device above the horizontally operated mixing device so that the mixture obtained in the first mixing device can flow only by gravity. The product inlet of the horizontally operated mixing device. Here, a discharge shaft can be used to introduce the mixture into the horizontally operated mixing device. In addition, a conduit may also be used to deliver the mixture obtained in the first mixing device to the horizontally operated mixing device, the conduit connecting the product outlet of the first mixing device and the product inlet of the horizontally operating mixing device .

Since the mixture must be heated in the horizontally operated mixing device to crosslink the surface of the water-absorbing polymer particles, it is also advantageous to pre-treat in another preheater between the first mixing device and the horizontally operated mixing device. Heat the mixture. In the preheater, the mixture may be preheated to a temperature of from 100 to 160 ° C from 20 to 100 ° C, preferably from 40 to 60 ° C. A temperature of from 120 to 140 ° C is preferred.

In addition, it may be advantageous to introduce the mixture into a dwell time mixer which may also be located between the first mixing device and the horizontally operated mixing device to make the aqueous crosslinking agent solution sufficient. The surface area of the aqueous polymer particles is infiltrated and the surface of the aqueous polymer particles is more uniformly wetted.

At least the horizontally operated mixing device provides a means for heat treating the mixture obtained in step (x1a), which may have the same or a different configuration than the first mixing device. The mixing device can have any shape and size to achieve proper mixing of the polymer. The cross-sectional configuration of the horizontally operated mixing device can be circular, oblate, cylindrical or rectangular. The mixing device provides at least one surface in contact with the compound during the heating operation, the surface being referred to as the "contact surface." The horizontally operated mixing device may have any volume, and preferably, the mixing device has a filling volume of 1 to 250,000 liters, more preferably 100 to 100,000 liters, most preferably 1,000 to 30,000 liters. Preferably, the mixture is introduced into the horizontally operated mixing apparatus at from about 4 to 10 tons per hour, and even preferably from 6 to 8.5 tons.

It is preferred to achieve a high degree of mixing of the polymer particles with the crosslinking agent. To this end, at least a portion of the first mixing device or the horizontally operated mixing device or the two devices can be moved in at least one direction, preferably in two directions, more preferably in more than two directions, the movement being horizontal or vertical. . The movement of at least a portion of the first or second mixing device is preferably a rotation or rotation of a movable member (e.g., having a shaft of a paddle) (in the case of the horizontally operated second mixing device, the paddle Rotation of the shaft). The rotation or rotation of at least a portion of the first or second mixing device may be horizontal or vertical or both (in the case of the horizontally operated second mixing device, the horizontal rotation of the paddle shaft). At least a portion of the convolution of the first mixing device may be simultaneously or sequentially in more than one direction.

According to a preferred embodiment of the method of the invention, the horizontally operated mixing device is a so-called " paddle dryer ". A paddle dryer is an indirect heating type of dryer that is attached to a hollow wedge-shaped rotary heater (a paddle placed on one or more shafts) without using any gas as a heating medium. Rotating in a horizontal direction about a central axis to heat the powdered material. All or almost all of the heat content required for drying is provided by direct heat transfer from the paddle shaft to the jacket. The heat transfer area of the preferred paddle dryer is preferably from 1 to 500 square meters, preferably from 80 to 200 square meters. The ratio of the surface of the shaft to the surface of the paddle to the surface of the sleeve area ("axis + paddle" surface area / "clip" surface area), preferably 1. An example of a suitable paddle dryer is model NPD-1.6W or NPD-14W supplied by Nara Machinery Co., Ltd. of Freising, Germany. Other mixing devices suitable for this purpose are paddle dryers supplied by Komline-Sanderson of Peapack, USA, or paddle dryers provided by Royal GMF-Gouda of Waddinxveen, The Netherlands.

According to a particularly preferred embodiment of one of the methods of the invention, the horizontally operated mixing device operates in an at least partially continuous manner. This may, for example, introduce water-absorbent polymer particles which have been mixed with the aqueous surface crosslinking solution, via the inlet of the head region of the horizontally operated mixing device, through the horizontally operated mixing device and then, with a certain delay After the time, this is achieved by exiting the horizontally operated mixing device at the outlet of the rear head region. Herein, the average delay time of the water-absorbing polymer particles depends, in particular, on the amount of the mixture fed from the inlet per unit time, the volume of the mixing device operated at the level, and the heat treatment from the outlet per unit time. The amount of the mixture. In addition to an adjustable inlet device, the delay time can be adjusted in particular via an adjustable outlet device. Preferably, the outlet means has one or more adjustable outlet openings. Possible outlet means are weirs, preferably vertically adjustable notches, but may also be cellular wheel sluices, discharge screws, especially for periodic adjustments. Or at least two of these.

The horizontally operated mixing device is hydraulically driven, which can be implemented via a hydraulic drive or hydraulic machine with a hydraulic motor. In a larger hydraulic system, a hydraulic motor is a common component, and a hydraulic motor converts hydraulic energy into mechanical energy. In industrial hydraulic systems, the pump and motor are typically used with appropriate valves and lines to create hydraulic energy transmission. Typically, the pump is connected to the motor via a carrier line, then the fluid is withdrawn from a reservoir and forced into the motor, which forces the movable member of the motor to operate, and then rotates the attached shaft. The shaft, which is mechanically coupled to the work load, provides a rotating mechanical operation. Finally, the fluid is discharged at a low pressure and returned to the pump. Different oils and water can be used as fluids. An advantage of a hydraulic machine that promotes this level of operation compared to an electronic motor is that the hydraulic machine can convert a large amount of energy to the mixing device without the risk of inversion or slippage. This has the advantage that it can be easily restarted even after the continuous process has been stopped, in which the compound is left in the mixing device. Restarting here, since the compounds usually stick together and cannot be mixed in the normal way, it is usually necessary to apply a large amount of energy.

In a preferred embodiment of the invention, the mixture is heat treated in a horizontally operated mixing apparatus at a temperature of from 150 to 250 ° C, preferably from 160 to 240 ° C, and most preferably from 170 to 230 ° C. The mixture may also be heat treated in the first mixing device, which may also be a hydraulic drive. Heating of the mixture in one of the mixing devices can be achieved by heating the contacting surface of the mixing device or by blowing a heated gas into the compound. Thus, there may be openings in at least a portion of the contact surface of the mixing device.

In the method according to the invention, the horizontally operated mixing device comprises one or more rotating shafts, preferably one or more rotating paddle shafts, particularly preferably two rotating paddle shafts rotating in opposite directions, and A hydraulic motor that converts hydraulic pressure and flow into torque and angular displacement is included to cause horizontal rotation of the paddle shaft. The conversion of the hydraulic energy to the shaft movement preferably does not use a plurality of conversion members. Thereby the energy of the hydraulic motor can be converted to the shaft without high energy losses. Even if the compound sticks to the mixing device due to the interruption of the process, the mixing device can be easily activated via the energy of the hydraulic motor.

Preferably, the paddle is provided on the rotating shaft. The paddles can be of any configuration and size as long as they can support mixing operations. Preferably, the paddles are in an extended form. The paddles are preferably oriented at an angle to the contact surface, preferably from 10 to 90, preferably from 30 to 70, more preferably from 40 to 60. The paddles may comprise any material suitable for contact with the compound, preferably the paddles comprise metal, plastic, wood or ceramic or a mixture of at least two of these. Preferably, the paddle comprises a metal selected from the group consisting of iron (especially high grade steel), titanium, silver, gold, chromium, cobalt or more. The paddle may be coated with a suitable polymer, such as a polypropylene or poly(tetrafluoroethylene) polymer, as desired. The number of paddles is preferably from 1 to 75, more preferably from 10 to 50 and most preferably from 15 to 30. In a preferred embodiment, wherein the horizontally operated mixing device comprises two rotating paddle shafts, the number of paddles on each axis may differ by one, two or three paddles, preferably one paddle. Furthermore, it is preferred that the shaft and the paddle on which the paddle is mounted have a hollow structure so that the heating medium can flow through the components of the mixer and the double wall coating flowing through the mixer (double -wall blanket). Accordingly, the inner surface of the coating of the horizontally operated mixing device and the outer surface of the paddle and the shaft serve as contact surfaces for heating the product.

Further, it is preferred to use oil as the hydraulic fluid in the motor. Any hydraulic oil that hardly changes its volume when pressed can be used. The oil can be any at 10 ° C to 300 ° C, Preferably, the temperature is from 50 ° C to 270 ° C, and more preferably from 100 ° C to 250 ° C.

The hydraulic drive or machine can provide power directly or indirectly to the paddle shaft. Direct power can be established by directly connecting, for example, a hydraulic arm to a paddle shaft of a horizontally operated mixing device. Preferably, however, one or more of the insert gears are coupled to couple the paddle shaft of the horizontally operated mixing device to the hydraulic motor. The gears can be located in a groove filled with gear oil. In order to avoid decomposition of the gear oil at the temperature of the horizontally operated mixing device, it is advantageous to cover the surface of the gear oil in the tank with a nitrogen pressure, thereby avoiding any contact of the hot gear oil with oxygen which causes the gear oil to decompose.

Another preferred method is that the average residence time of the granules in the horizontally operated mixing apparatus is from 5 to 500 minutes, preferably from 10 to 250 minutes, more preferably from 20 to 180 minutes. At this time of delay, the polymer particles which have been mixed with the crosslinking agent will react with the crosslinking agent on the surface thereof to obtain surface-crosslinked polymer particles.

In a preferred embodiment, the rotational speed of the shaft in the horizontally operated mixing device is 5 to 25 revolutions per minute, more preferably 7.5 to 22.5 revolutions, and most preferably 10 to 20 revolutions.

A contribution to the resolution of the objects mentioned at the outset is also provided by the water-absorbing polymer particles obtainable by this method. Preferably, the water-absorbing polymer particles have a residual monomer content of less than 500 ppm, preferably less than 450 ppm and even preferably less than 400 ppm, as determined according to the WSP 210.2 test method.

Further, the contribution to the achievement of the objects mentioned at the outset is provided by a composite material comprising water-absorbent polymer particles obtainable by the process according to the invention and a substrate. Here, it is preferred that the water-absorbing polymer particles and the substrate are firmly bonded to each other. Preferred substrates are polymers (for example, polyethylene, polypropylene, or polyimide) films, metals, nonwovens, fluff, tissues, fabrics, natural or man-made fibers, or Other foam materials. According to still another preferred embodiment of the present invention, the composite material comprises at least one region comprising from about 15 to 100% by weight, preferably from about 30 to 100% by weight, particularly preferably from about the total weight of the composite material region in question. 50 to 99.99% by weight, further preferably about 60 to 99.99% by weight, and further preferably about 70 to 99% by weight of the water-absorbing polymer particles, preferably having at least 0.01 cubic centimeters, preferably at least 0.1 cubic centimeters and The best size is at least 0.5 cubic centimeters.

In a particularly preferred embodiment of the composite material according to the invention, a planar composite material such as the "absorbent material" described in WO 02/056812 A1 is used. The disclosure of WO 02/056812 A1, in particular with regard to the precise structure of the composite material, per unit thereof The constituent weights and thicknesses of the areas are hereby incorporated by reference and are incorporated herein by reference.

Further, the contribution to the achievement of the objects mentioned at the outset is provided by a method of producing a composite material, wherein the water-absorbent polymer particles obtainable by the method according to the invention and a substrate and optionally additives are obtained. Contact. The substrate used is preferably a substrate which has been mentioned above in relation to the composite material according to the invention.

The contribution to the achievement of the objects mentioned at the outset is also provided by a composite material obtainable by the above-described method according to the invention, which composite material preferably has the same properties as the composite material according to the invention described above.

Further, the contribution to the achievement of the objects mentioned at the outset is provided by a chemical product comprising water-absorbent polymer particles obtainable by the process according to the invention or a composite material according to the invention. Preferred chemical products are, in particular, foamed materials, shaped articles, fibrous materials, foils, membranes, cables, sealing materials, liquid absorbent sanitary articles (especially diapers and sanitary tracts), for plants or mites ( Fungal) A carrier for growth regulators or plant protection active compounds, building material additives, packaging materials or soil additives.

The above object can also be achieved from the use of the water-absorbing polymer particles obtained by the process according to the invention or the composite material according to the invention in chemical products, preferably in the case of the above-mentioned chemical products, in particular in the case of diapers or sanitary tracts. The use of the article, and the use of the superabsorbent particles as a growth regulator for plants or alfalfa or a carrier for a plant protection active compound. For use as a growth regulator for a plant or a plant or a carrier for a plant protection active compound, it is preferred that the plant or earthworm growth regulator or plant protection active compound is released for a period of time controlled by the carrier.

The invention will now be described more closely in the drawings.

Figure 1 shows a schematic cross-sectional view of a mixing device 1 suitable for horizontal operation in accordance with one of the methods of the present invention. The mixing device 1 comprises a rotating paddle shaft 2 provided with a plurality of mixing paddles 3. As shown in Fig. 2, the delay time of the filling level 4 and the water-absorbing polymer particles in the horizontally operated mixing device 1 in the horizontally operated mixing device 1 can be controlled via an adjustable outlet device. Preferably, the outlet device has an adjustable outlet opening 5, which is vertically adjustable The whole form of the gap.

Figure 3 is a schematic cross-sectional view of a horizontally operated mixing device 1 in which the paddle shaft 2 is directly driven by hydraulic pressure via the insert gear 6. Power is transmitted to the paddle shaft 2 via a plurality of inset gears 6 located in the slot 8 via a gearing 7 that is hydraulically driven directly coupled to the hydraulic motor. The tank 8 is filled with gear oil, wherein the gear oil is preferably under a nitrogen atmosphere.

Figure 4 shows a specific embodiment of a device according to the invention for producing a superabsorbent in which a polymer gel is passed through a partially neutralized acrylic acid, at least one crosslinked The agent, and the aqueous monomer solution of the starter, are formed by free radical polymerization, and then, after the finely pulverizing the gel, are dried in the drying zone 10 to a water content of preferably less than 10% by weight. The water absorption obtained in this way is then treated with another grinding and sieving section 11 to obtain a specific particle size fraction.

The water-absorbing polymer particles thus obtained are then sent to a surface cross-linking section 12 comprising a first mixing device 13 (which may be a Schugi® mixer) and a hydraulically driven horizontal mixing device 1 . The horizontally operated mixing device 1 can be, for example, a Nara® mixer.

1‧‧‧ horizontally operated mixing device

9‧‧‧Polymerization zone

10‧‧‧Dry area

11‧‧‧Making and screening sections

12‧‧‧Surface cross-section

13‧‧‧First Mixer

Claims (15)

A method for preparing water-absorbing polymer particles, comprising the steps of: (i) preparing an aqueous monomer solution comprising at least partially neutralized monoethylidene type having a carboxylic acid group ( Monoethylenically) an unsaturated monomer (α1) and at least one crosslinking agent (α3); (ii) optionally adding a fine particle or aqueous salt solution of a water-absorbing polymer to the aqueous monomer solution; (iii) adding a polymerization a reaction initiator or at least one component of a polymerization initiator system comprising two or more components to the aqueous monomer solution; (iv) reducing the oxygen content of the aqueous monomer solution; (v) the aqueous monomer The solution is charged into a polymerization reactor; (vi) the monomer in the aqueous monomer solution is polymerized in the polymerization reactor to obtain a polymer gel; (vii) the polymer gel is discharged from the polymerization reaction And pulverizing the polymer gel as needed to obtain polymer gel particles; (viii) drying the polymer gel particles; (ix) grinding the dried polymer gel particles to obtain particulate water absorption Polymeric particles; (x) sieving the ground water-absorbent polymer And (xi) crosslinking the surface of the ground and sieved water-absorbing polymer particles, wherein the method step (xi) comprises the step of: (x1a) mixing the particles with an aqueous crosslinking agent solution And (x2a) heat treating the mixture obtained in the method step (x1a) in a horizontally operated mixing device, wherein the horizontally operated mixing device is hydraulically driven. The method of claim 1, wherein the mixture is heat-treated at a temperature of from 150 ° C to 250 ° C in a horizontally operated mixing device. The method of claim 1, wherein the horizontally operated mixing device comprises at least one rotating shaft and a hydraulic pressure and flow A hydraulic motor that converts into torque and angular displacement, thereby causing the shaft to rotate. The method of claim 2, wherein the horizontally operated mixing device comprises at least one rotating shaft and a hydraulic motor that converts hydraulic pressure and flow into torque and angular displacement to cause the shaft to rotate. The method of claim 3, wherein the paddle is disposed on the rotating shaft. The method of claim 4, wherein the paddle is disposed on the rotating shaft. The method of any one of claims 3 to 6, wherein oil is used as the hydraulic fluid in the hydraulic motor. The method of any one of claims 1 to 6, wherein the average residence time of the granules in the horizontally operated mixing device is from 5 to 500 minutes. The method of any one of claims 1 to 6, wherein the rotational speed of the shaft in the horizontally operated mixing device is 5 to 25 revolutions per minute. A water-absorbing polymer particle obtained by the method of any one of claims 1 to 9. A composite material comprising the water-absorbing polymer particles of claim 10. A method of producing a composite material, wherein the water-absorbing polymer particles of claim 10 are brought into contact with a substrate and an auxiliary material as needed. A composite material obtained by the method of claim 11. A foaming material, a shaped article, a fiber material, a foil material, a film material, a cable, a sealing material, a liquid absorption sanitary article, a carrier for a plant or a fungal growth regulator, a packaging material, a soil additive, or A building material comprising the water-absorbing polymer particles of claim 10 or a composite material according to claim 11 or 13. A use of the water-absorbing polymer particles of claim 10 or the composite material of claim 11 or 13 for foaming materials, shaped articles, fibrous materials, foils, films, cables, sealing materials, A liquid-absorbable carrier, a plant or a growth regulator of a plant or a plant protection active compound, a packaging material, a soil additive, or a building material.