EA030945B1 - Process and device for the preparation of water-absorbent polymer particles, use of particles, composite material and process for the production thereof - Google Patents

Abstract

The present invention generally relates to a process for the preparation of water-absorbent polymer particles and to a device for the preparation of water-absorbent polymer particles, a composite material comprising water-absorbent polymer particles and a process for the production thereof.

Description

The present invention relates to a method for producing water-absorbing polymer particles; to the water-absorbing polymer particle, which can be obtained by this method; to a composite material containing the specified water-absorbing polymer particle; to a method for producing a composite material, to a composite material that can be obtained by this method; to the use of water-absorbing polymer particles; to a device for producing water-absorbing polymer particles and to a method for producing water-absorbing polymer particles using the specified device.

The level of technology

Superabsorbents are water-insoluble cross-linked polymers that can absorb large amounts of aqueous fluids, especially physiological fluids, more specifically urine or blood, with swelling and formation of hydrogels, as well as to keep these fluids at a certain pressure. Due to these characteristic properties, such polymers are used mainly in hygienic products, such as, for example, baby diapers / diapers, products for patients with incontinence or sanitary napkins.

The preparation of superabsorbents is generally carried out by free radical polymerization of monomers containing an acid group in the presence of crosslinking agents; Polymers with different absorbing properties can be obtained by selecting the monomer composition, crosslinking agents and polymerization conditions, as well as the processing conditions of the hydrogel obtained after polymerization (details are presented, for example, in Modern Superabsorbent Polymer Technology, FL Buchholz, GT Graham, Wiley-VCH, 1998).

Polymer gel, also called hydrogel, obtained after polymerization, is usually crushed, dried and sorted to obtain a superabsorbent in the form of particles with a well-defined particle size distribution. At the next technological stage, these superabsorbent particles are often subjected to surface crosslinking to improve absorption characteristics. For this, the particles are mixed with an aqueous solution containing a surface crosslinking agent and optionally additional additives, and the resulting mixture is thermally treated to accelerate the crosslinking reaction.

Monomers containing an acidic group can be polymerized in the presence of crosslinkers in a batch process or in a continuous process. In continuous and batch polymerization, partially neutralized acrylic acid is usually used as the monomer. Suitable polymerization processes are described, for example, in EP 0372706 A2, EP 0574260 A1, WO 2003/051415 A1, EP 1470905 A1, WO 2007/028751 A1, WO 2007/028746 A1 and WO 2007/028747 A1.

Description

Technical problem

To obtain water-absorbing polymer particles, the polymer gel is dried and the dried polymer gel is ground. In the prior art it is known that the advantage is two-stage grinding. In the first grinding stage, the dried polymer gel is subjected to coarse grinding to obtain particles. These particles as quickly as possible serves on the second stage of grinding. As a result, the particles of water-absorbing material adhere to the grinding device, for example, the teeth of the gear wheel, which leads to a deterioration of the grinding result. In addition, deposits of water-absorbing material accumulate in the grinding device. Such deposits may block moving parts of the chopping device or passage through the device, or both. When growing to a sufficient mass, these deposits can fall down and cause damage to the internal parts of the device or adversely affect the grinding process, or both.

When implementing the present invention, it was unexpectedly found that the storage of particles after the first grinding stage or before the second grinding stage leads to an improvement in the grinding result. This effect was investigated to determine the dependencies and the optimal storage time with respect to the grinding result and the effectiveness of the general method of preparation.

Technical solution

In general, the object of the present invention is, at least in part, to overcome the drawback inherent in the prior art in the context of the preparation of superabsorbents.

An additional challenge is to provide a method for producing water-absorbing polymers, in which the operational life or the operational period is increased before the need for maintenance arises, or both, at least part of the device used to grind the dried polymer gel. An additional object of the present invention is to provide a method for preparing water-absorbing polymers in which the amount of small water-absorbing polymer particles formed is reduced, preferably by grinding the dried polymer gel. An additional object of the present invention is to provide a continuous method for producing water-absorbing polymers, in which the size of the device used in said method is reduced, without reducing the yield of the process. Before

- 1 030945 The additional objective of the present invention is to provide a continuous method for producing water-absorbing polymers, in which the cost of the device used in the specified method is reduced, without reducing the yield of the process. An additional objective of the present invention is to provide a method for producing water-absorbing polymers, where this method demonstrates a balanced combination of the above advantages. An additional challenge is to provide water-absorbing polymer particles obtained in a less expensive way. An additional object of the present invention is to provide a device for producing water-absorbing polymer particles in a manner having at least one of the above advantages. An additional objective of the present invention is to provide a composite material containing a water-absorbing polymer particle obtained by a method having at least one of the above advantages, where the composite material shows no deterioration.

The contribution to the solution of at least one of the above problems is presented by the independent claims. Dependent claims represent preferred implementations of the present invention, which also serve to solve at least one of the above problems.

Beneficial effect

The present invention provides at least a partial overcoming of the disadvantage inherent in the prior art in the context of producing superabsorbents.

Description of figures

The figures represent:

FIG. 1 is a flow chart illustrating the process steps of the present invention;

FIG. 2 is a flow chart illustrating the steps of another process according to the present invention;

FIG. 3 is a flow chart illustrating the steps of another process according to the present invention;

FIG. 4 is a flow sheet of a process step (ix) according to the present invention;

FIG. 5 is a flow chart of another process step (ix) according to the present invention;

FIG. 6 is a block diagram of an apparatus for producing water-absorbing polymer particles according to the present invention;

FIG. 7 is a block diagram of another device for producing water-absorbing polymer particles according to the present invention.

List of symbols:

100 — method according to the present invention;

101 - stage (i);

102 stage (ii);

103 - stage (iii);

104 — stage (iv);

105 - stage (v);

106 stage (vi);

107 stage (vii);

108 stage (viii);

109 - stage (ix);

110 - stage (x);

111 stage (xi);

401 - dried polymer gel;

402 - the first grinding device;

403 — the first ground water-absorbing polymer particles;

404 - withstand device;

405 - the first part of the first ground water-absorbing polymer particles;

406 - additional grinding device;

407 — additional ground water-absorbing polymer particles;

408 - first stay;

409 - second stay;

410 - the third time of stay;

501 - additional sorting device;

502 - an additional part of the first ground water-absorbing polymer particles;

600 — apparatus for producing particles of a water-absorbing polymer;

601 - the first container;

602 - additional container;

- 2 030945

603 - mixing device;

604 - polymerization reactor;

605 - crushing device;

606 - belt dryer;

607 - the first sorting device;

608 - process flow.

The best way to exercise

The contribution to the solution of at least one of these tasks is provided by means of a method for producing water-absorbing polymer particles, including the technological steps:

(i) obtaining an aqueous solution of a monomer containing at least one partially neutralized monoethylenically unsaturated monomer comprising carboxylic acid groups (a1) and at least one crosslinking agent (a3);

(ii) optionally adding fine particles of a water-absorbing polymer to the aqueous monomer solution;

(iii) adding a polymerization initiator or at least one component of a polymerization initiator system, which contains two or more components, to an aqueous solution of a monomer;

(iv) optionally reducing the oxygen content in the aqueous monomer solution;

(v) loading the aqueous monomer solution into the polymerization reactor;

(vi) polymerization of monomers in an aqueous solution of monomer in a polymerization reactor;

(vii) discharging the polymer gel from the polymerization reactor and optionally crushing the polymer gel;

(viii) drying the polymer gel;

(ix) processing:

a) the dried polymer gel in the first grinding stage in the first grinding device to produce the first crushed water-absorbing polymer particles;

b) first ground water-absorbing polymer particles by keeping in a holding device; then

c) at least the first part of the first crushed water-absorbing polymer particles at an additional grinding stage in an additional grinding device with obtaining additional crushed water-absorbing polymer particles;

(x) sorting by size of the additional ground water-absorbing polymer particles; and (xi) optional surface treatment of additional ground and water-absorbable polymer particles sorted by size, where in the process step (ix) the dried polymer gel and the first ground water-absorbing polymer particles obtained from the dried polymer gel are generally kept for the first time in the first grinding device;

the first crushed water-absorbing polymer particles are kept for a second residence time in a holding device;

at least the first part of the first ground water-absorbing polymer particles and the additional ground water-absorbing polymer particles obtained from at least the first part of the first ground water-absorbing polymer particles are generally kept for a third residence time in the additional grinding device; where the second time is more than the first time; where the second time is more than the third time.

In this process, the second residence time is preferably longer than the first residence time for more than 5 minutes, more preferably for more than 10 minutes, more preferably for more than 20 minutes, more preferably for more than 30 minutes, more preferably for more than 40 minutes, more preferably for more than 50 minutes , more preferably for more than 60 minutes, more preferably for more than 70 minutes, more preferably for more than 80 minutes, more preferably for more than 90 minutes, more preferably for more than 100 minutes, more preferably for more than 120 minutes, more preferred at no more than 130 minutes, most preferably for more than 135 minutes.

The second residence time is preferably longer than the third residence time for more than 5 minutes, more preferably for more than 10 minutes, more preferably for more than 20 minutes, more preferably for more than 30 minutes, more preferably for more than 40 minutes, more preferably for more than 50 minutes, more preferably for more than 60 minutes, more preferably for more than 70 minutes, more preferably for more than 80 minutes, more preferably for more than 90 minutes, more preferably for more than 100 minutes, more preferably for more than 120 minutes, more preferably for more than 130 minutes, he most preferably more than 135 m.

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In this regard, the successive stages of the process according to the present invention may be carried out simultaneously, or may overlap in time, or both options may occur. This applies in particular to stages (i) - (iv), especially to stages (iii) and (iv).

The method according to the present invention is preferably a continuous process in which an aqueous solution of monomer is provided continuously and continuously fed to the polymerization reactor. The resulting hydrogel is continuously discharged from the polymerization reactor and, optionally, continuously crushed, dried, crushed and sorted by size in subsequent process steps. However, this continuous process can be interrupted, for example, to replace some parts of the process equipment such as a conveyor belt material, if a conveyor belt is used as a polymerization reactor, to clean some process equipment items, especially to remove polymer deposits in tanks or pipes, or to start a new process. if it is necessary to obtain water-absorbing polymer particles with other absorption characteristics.

Water-absorbing polymer particles, preferred according to the present invention, are particles that have an average particle size in accordance with WSP 220.2 (Word Strategic Partners ED ANA and INDA test method) from 10 to 3000 μm, preferably from 20 to 2000 μm, and particularly preferably from 150 to 850 microns. In this context it is particularly preferable that the content of particles of water-absorbing polymers having a particle size of from 300 to 600 μm is at least 30% by weight, particularly preferably at least 40% by weight and most preferably at least 50% by weight total mass of water-absorbing polymer particles.

In the process step (i) of the process according to the present invention, an aqueous monomer solution is obtained containing at least one partially neutralized monoethylenically unsaturated monomer having carboxylic acid groups (“1) and at least one crosslinking agent (“ 3).

Preferred monoethylenically unsaturated monomers having carboxylic acid groups (“1) are the monomers mentioned in DE 10223060 A1 as preferred monomers (“ 1), thus, particularly preferred is acrylic acid.

According to the present invention, it is preferable that the water-absorbing polymer obtained by the method according to the present invention contains monomers having carboxylic acid groups in an amount of at least up to 50% by weight, preferably at least up to 70% by weight and even more preferably at least up to 90 wt.% relative to dry weight. According to the present invention, it is particularly preferred that the water-absorbing polymer obtained by the method according to the present invention is obtained from at least 50% by weight, preferably from at least 70% by weight of acrylic acid, which is preferably neutralized to at least 20 mol%, particularly preferably at least up to 50 mol.%. The concentration of partially neutralized, monoethylenically unsaturated monomers having carboxylic acid groups (“1) in the aqueous monomer solution, which is provided at the technological stage (i), is preferably from 10 to 60 wt.%, Preferably from 30 to 55 wt.% And most preferably from 40 to 50 wt.% of the total mass of the aqueous solution of monomer.

The aqueous monomer solution may also contain monoethylenically unsaturated monomers (“2), which can be copolymerized with (“ 1). Preferred monomers (“2) are the monomers mentioned in DE 10223060 A1 as preferred monomers (“ 2), thus acrylamide is particularly preferred.

Preferred crosslinking agents (“3) according to the present invention are compounds that have at least two ethylenically unsaturated groups in one molecule (crosslinking agent of class I), compounds that have at least two functional groups that can interact with the functional groups of monomers ("1) or (" 2) in a condensation reaction (= crosslinking agents of condensation), in an addition reaction or in a ring opening reaction (crosslinking agent of class II), compounds that have at least one and an unsaturated group and at least one functional group that can interact with the functional groups of the monomers (“1) or (2) in the condensation reaction, in the addition reaction or in the ring opening reaction (crosslinking agent of class III), or polyvalent metal cations ( crosslinking agent class IV). Thus, with compounds of a class of crosslinking agents I, polymer crosslinking is achieved by radical polymerization of ethylenically unsaturated groups of molecules of a crosslinking agent with monoethylenically unsaturated monomers ("1) or (" 2), and with compounds of the class of crosslinking agents II and cations of polyvalent metals of the class of crosslinking agents IV, crosslinking of the polymer , respectively, by the condensation reaction of functional groups (a class II crosslinking agent) or by electrostatic interaction of a polyvalent metal cation (a crosslinking agent cl cca IV) with monomer functional groups (“1) or (“ 2). With compounds of the class of crosslinking agents III, cross-linking of polymers is achieved, respectively, by radical polymerization

- 4 030945 ethylenically unsaturated groups, as well as a condensation reaction between the functional groups of the crosslinking agents and the functional groups of the monomers (a1) or (a2).

Preferred crosslinking agents (a3) are all those compounds which are indicated in DE 10223060 A1 as crosslinking agents (a3) of crosslinker classes I, II, III and IV, thus, as compounds of crosslinking agent I class, Ν, 'are particularly preferred methylene-bis-acrylamide, di (meth) acrylates of polyethylene glycol triallilmetilammoniya chloride, tetra allyl ammonium chloride and allilnonaetilenglikolakrilat obtained from 9 moles of ethylene oxide per 1 mole of acrylic acid, wherein more preferably Ν, Ν'-methylene-bis-acrylamide, and as compounds class Ca crosslinking agents IV are particularly preferred Al ₂ (SO.-i) ₃ , and its hydrates.

Preferred water-absorbing polymers obtained by the method according to the present invention are polymers crosslinked with crosslinking agents of the following classes of crosslinking agents, or crosslinking agents of the following combinations of classes of crosslinking agents, respectively: I, II, III, IV, III, I III, I IV, I II III, I II IV, I III IV, II II IV, II IV or III IV.

Additionally, preferred water-absorbing polymers obtained by the method according to the present invention are polymers crosslinked by any crosslinking agents described in DE 102 23 060 A1 as a crosslinking agent of crosslinking agents class I, thus, are particularly preferred as crosslinking agents of the class of crosslinking agents I KI - methylene bis-acrylamide. polyethylene glycol di (meth) acrylates, triallylmethylammonium chloride, tetraallyl ammonium chloride and allylnone ethyleneglycol acrylate, prepared from 9 mol of ethylene oxide per 1 mol of acrylic acid, where Ν, Ν'-methylene bis acrylamide is more preferred.

The aqueous monomer solution may additionally contain water-soluble polymers (a4). Preferred water-soluble polymers (a4) include partially or fully saponified polyvinyl alcohol, polyvinylpyrrolidone, starch or starch derivatives, polyglycols or polyacrylic acid. The molecular weight of these polymers is not critical, provided that they are water soluble. Preferred water soluble polymers (a4) are starch or starch derivatives or polyvinyl alcohol. Water-soluble polymers (a4), preferably synthetic, such as polyvinyl alcohol, can not only serve as the basis for grafting polymerizable monomers. It is clear that these water-soluble polymers can also be mixed with a polymer gel or with an already dried water-absorbing polymer.

The aqueous monomer solution may additionally contain auxiliary substances (a5), and these auxiliary substances include, in particular, complexing agents, such as, for example, EDTA.

The relative amount of monomers (a1) and (a2), and cross-linking agents (a3), and water-soluble polymers (a4), and auxiliary substances (a5) in an aqueous monomer solution is preferably chosen so that the structure of the water-absorbing polymer obtained after drying of the optionally crushed polymer gel, based on 20-99.999 wt.%, preferably 55-98.99 wt.% and particularly preferably 70-98.79 wt.% on the monomers (a1), 0-80 wt.%, preferably 0 -44.99 wt.% And particularly preferably 0.1-44.89 wt.% On monomers (a2), 0-5 wt.%, Preferably on 0.001-3 wt.% And particularly preferably 0.01-2.5 wt.% On crosslinking agents (a3), 0-30 wt.%, Preferably 0-5 wt.% And particularly preferably 0.1 -5 wt.% On water-soluble polymers ((/.4), 0-20 wt.%, Preferably 0-10 wt.% And particularly preferably 0.1-8 wt.% On excipients (a5), and 0.5-25 wt.%, preferably 1-10 wt.% and particularly preferably 3-7 wt.% on water (/ 6), the sum of the quantities by weight (/ 1) - (/ 6) is 100 wt.%.

The optimal concentration values, in particular, monomers, crosslinking agents and water-soluble polymers in the monomer solution can be determined by simple preliminary experiments or on the basis of the known prior art, in particular from publications US 4286082, DE 2706135 A1, US 4076663, DE 3503458 A1, DE 4020780 C1, DE 4244548 A1, DE 4333056 A1 and DE 4418818 A1.

In the process step (ii), fine particles of a water-absorbent polymer may optionally be added to the aqueous monomer solution. Regardless of the optional step (ii), the fine particles of the water-absorbing polymer may be added to the aqueous monomer solution at any step selected from the group consisting of: after step (iii), after step (iv) and before step (v) or in combination at least two of them.

Water-absorbing fine particles are preferably particles of a water-absorbing polymer whose composition corresponds to the composition of the water-absorbing polymer particles described above, it is preferable that at least 90% by weight of water-absorbing small particles, preferably at least 95% by weight of water-absorbing small particles and most

- 5 030945, preferably at least 99 wt.% Of water-absorbing fine particles have a particle size of less than 200 microns, preferably less than 150 microns and particularly preferably less than 100 microns.

In a preferred embodiment of the method according to the present invention, the water-absorbing fine particles, which can optionally be added to the aqueous monomer solution at the process stage (ii), are water-absorbing small particles that are obtained at the process stage (x) of the method according to the present invention and which way, return to the cycle.

These fine particles can be added to the aqueous monomer solution using any mixing device known to those skilled in the art as suitable for the purpose indicated. In a preferred embodiment of the present invention, which is particularly suitable if the process is carried out continuously as described above, fine particles are added to an aqueous solution of monomer in a mixing device, in which the first stream of small particles and the second stream of aqueous solution of monomer are sent continuously, but from different positions , in a rotating mixing device. This type of mixing plant can be implemented in a so-called rotor-stator mixer, which contains in the mixing zone a preferably cylindrical, non-rotating stator, in the center of which also preferably a cylindrical rotor rotates. The walls of the rotor, as well as the walls of the stator are usually provided with notches, for example, notches in the form of slots through which a mixture of fine particles and an aqueous solution of monomer can be sucked and, therefore, subjected to high shear forces.

In this context, it is particularly preferable that the first stream of fine particles and the second stream of monomer aqueous solution form an angle δ of from 60 to 120 °, more preferably from 75 to 105 °, even more preferably from 85 to 95 ° and most preferably form an angle of about 90 ° . It is also preferable that the flow of the mixture of small particles and the aqueous monomer solution leaving the mixer, and the first stream of small particles entering the mixer, form an angle of ε from 60 to 120 °, preferably from 75 to 105 °, even more preferably from 85 to 95 ° and most preferably form an angle of about 90 °.

This type of mixing plant can, for example, be implemented using mixing devices described in DE-A-2520788 and DE-A-2617612, the contents of which are incorporated herein by reference. Specific examples of mixing devices that can be used to add fine particles to an aqueous monomer solution at the technological stage (ii) of the present invention are mixing devices that can be purchased from PSA® Werke GmbH & Co. KG, Staufen, Germany, under the trade designations MHD 2000/4, MHD 2000/05, MHD 2000/10, MDH 2000/20, MHD 2000/30 and MHD 2000/50, where the MHD 2000/20 mixing device is particularly preferred. Additional mixing devices that can be used are those manufactured by Ystral GmbH, Balrechten-Döttingen, Germany, for example, under the trademark Conti TDS, or by Kinematika AG, Littau, Switzerland, for example, under the trademark Megatron®.

The amount of fine particles that can be added to the aqueous monomer solution in the process step (ii) is preferably from 0.1 to 15% by weight, even more preferably from 0.5 to 10% by weight and most preferably from 3 to 8 wt.% relative to the mass of the aqueous solution of monomer.

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

As initiators of polymerization for initiating polymerization, all initiators forming radicals under polymerization conditions, which are usually used in the preparation of superabsorbents, can be used. These include thermal catalysts, redox catalysts and photoinitiators, the activation of which occurs during energy irradiation. Polymerization initiators can be dissolved or dispersed in an aqueous solution of the monomer. Preferably the use of water-soluble catalysts.

As thermal initiators, all compounds known to those skilled in the art that decompose under the action of elevated temperature to form radicals can be used. Thermal polymerization initiators with a half-life of less than 10 s, more preferably less than 5 s at a temperature of less than 180 ° C, more preferably less than 140 ° C, are particularly preferred. Particularly preferred thermal polymerization initiators are peroxides, hydroperoxides, hydrogen peroxide, persulfates and azo compounds. In some cases, it is preferable to use mixtures of various thermal polymerization initiators. Among such mixtures, mixtures containing hydrogen peroxide and sodium or potassium peroxodisulfate are preferred, which can be used in any desired proportion. Suitable organic peroxides are preferably acetylacetone peroxide, methyl ethyl ketone peroxide, benzoyl peroxide, lauroyl peroxide, acetyl peroxide, caprylyl peroxide,

- 6,090 days per month. , tert-butyl-3,5,5-trimethylhexanoate and amyl perneodecanoate. In addition, the following thermal polymerization initiators are preferred: azo compounds, such as azo-bis isobutyronitrile, azo-bis-dimethylvaleronitrile, azo-bis-amidinopropane dihydrochloride, 2,2'-azo-bis (Y, M-dimethylene) isobutyramidine dihydrochloride, 2 - (carbamoylazo) isobutyronitrile and 4,4'-azo-bis- (4 cyanovaleric acid). The above compounds are used in conventional amounts, preferably from 0.01 to 5 mol.%, Preferably from 0.1 to 2 mol.%, Respectively, relative to the amount of polymerized monomers.

Redox catalysts contain two or more components, usually one or more of the peroxo compounds listed above, and at least one reducing component, preferably ascorbic acid, glucose, sorbose, mannose, hydrosulfite, sulfate, thiosulfate, hyposulfite or ammonium sulfide or an alkali metal , metal salts, such as iron ions (11) or silver ions, or sodium hydroxymethyl sulphoxylate. Preferably, ascorbic acid or sodium pyrosulfite is used as the reducing component of the redox catalyst. From 1x10 ^-5 to 1 mol.% Of the reducing component of the redox catalyst and from 1x10 ^-5 to 5 mol.% Of the oxidizing component of the redox catalyst are used, in each case relative to the amount of monomers used in the polymerization. Instead of the oxidative component of the redox catalyst or as its addition, one or more preferably water-soluble azo compounds can be used.

Polymerization is preferably initiated by the action of energy radiation, so-called photoinitiators are usually used as initiators. These may include, for example, so-called a-splitters, H-depleting systems, or also azides. Examples of such initiators are benzophenone derivatives, such as Michler's ketone, phenanthrene derivatives, fluorine derivatives, anthraquinone derivatives, thioxanthone derivatives, coumarin derivatives, benzoic ester and its derivatives, azo compounds, such as the aforementioned radical-forming compounds, substitute cacidic acid, Icidic acid,. Examples of azides are: 2- (K, N-dimethylamino) ethyl-4-azidocinnamate,

2- (M, N-dimethylamino) ethyl 4-azidonaphthylketone, 2- (S, N-dimethylamino) ethyl 4-azidobenzoate, 5-azido-1naphthyl-2 '- (M, N-dimethylamino) ethylsulfone, Y- (4-sulfonyl azidophenyl) maleinimide, N-acetyl-4 sulfonyl azidoaniline, 4-sulfonyl azidoaniline, 4-azidoaniline, 4-azidophenacyl bromide, p-azidobenzoic acid, 2,6-bis (p-azido benzylidene) cyclohexane-hecanane-benzoic acid; p-azidobenzylidene) -4 methylcyclohexanone. An additional group of photoinitiators are dialkoxyketals, such as 2,2-dimethoxy-1,2-diphenylethan-1-one. Photoinitiators, when used, are usually used in an amount of from 0.0001 to 5 wt.% Relative to the polymerized monomers.

In accordance with an additional embodiment of the method according to the present invention, it is preferable that at the technological stage (iii) the initiator contains the following components:

iiia) peroxodisulfate; and iiib) an organic initiator molecule containing at least three oxygen atoms or at least three nitrogen atoms, where said initiator contains peroxodisulfate and an organic initiator molecule in a molar ratio of from 20: 1 to 50: 1.

In one aspect of this embodiment, it is preferred that the concentration of the initiator component (iiia) is from 0.05 to 2% by weight with respect to the amount of polymerizable monomers. In another aspect of this embodiment, it is preferred that the organic initiator molecule is selected from the group consisting of 2,2-dimethoxy-1,2-diphenylethan-1-one, 2,2-azo-bis (2amidinopropane) dichloride, 2,2 azo bis (cyanovaleric acid) or a combination of at least two of them. In an additional aspect of this embodiment, it is preferred that the peroxodisulfate has the general formula M ₂ S ₂ O ₈ , where M is selected from the group consisting of NH ₄ , Li, Na, K, or at least two of them. The components described above are particularly suitable for UV initiating the polymerization in step (vi) of the process according to the present invention. The use of this composition additionally results in a low amount of residual monomer and a decrease in yellowing of the water-absorbing polymer particle, which can be obtained by the method according to the present invention.

In this context, it should also be noted that stage (iii), the addition of a polymerization initiator, can be implemented to stage (iv), simultaneously with stage (iv) or overlap in time with stage (iv), i.e. with a decrease in the oxygen content in the aqueous solution of the monomer. When using a polymerization initiator system that contains two or more components, one or more components of such a polymerization initiator system may, for example, be added to the technological stage (iv), while the rest of the component or the remaining components that are necessary for

- 7 030945 the completion of the activity of the said polymerization initiator system, is added after the technological stage (iv), possibly even after the technological stage (v). Regardless of the optional step (iv), a decrease in the oxygen content of the aqueous monomer solution can also be carried out before the technological step (iii) in accordance with the present invention.

At the technological stage (iv) of the method according to the present invention in the aqueous monomer solution, the oxygen content is not necessarily reduced. Regardless of the optional step (iv), a decrease in the oxygen content of the aqueous monomer solution can also be carried out before, during or after the process step (ii) in accordance with the present invention. Preferably, the oxygen content in the aqueous solution of the monomer is reduced after the addition of fine particles in the process step (ii).

Whenever there is a decrease in the oxygen content of an aqueous monomer solution, it can be realized by contacting an aqueous monomer solution with an inert gas, such as nitrogen. The inert gas phase brought into contact with the aqueous monomer solution does not contain oxygen and, therefore, is characterized by a very low partial pressure of oxygen. Consequently, oxygen is transferred from the aqueous solution of the monomer to the inert gas phase before the partial pressure of oxygen in the inert gas phase and in the aqueous monomer solution is equal. The contacting of the aqueous monomer phase with the inert gas phase can be accomplished, for example, by passing inert gas bubbles through the monomer solution in the form of a direct flow, countercurrent or at an intermediate feed angle. Good mixing can be achieved, for example, using nozzles, static or dynamic mixers or bubble columns. The oxygen content in the monomer solution before polymerization is preferably reduced to less than 1 ppm by weight, more preferably less than 0.5 ppm by weight relative to the weight of the monomer solution.

At the technological stage (v) of the method according to the present invention, an aqueous monomer solution is loaded into a polymerization reactor, preferably on a conveyor belt, particularly preferably in the forward position of the conveyor belt, and at the technological stage (vi) monomers in an aqueous monomer solution are polymerized in a polymerization reactor obtaining a polymer gel. When carrying out polymerization on a conveyor belt, as a polymerization reactor, a sheet of polymer gel is obtained in the rear part of the conveyor belt, which is preferably crushed to obtain particles of polymer gel before drying.

As a polymerization reactor, any reactor can be used that is considered suitable by those skilled in the art for continuous or batch polymerization of monomers such as acrylic acid in aqueous solution. An example of a suitable polymerization reactor is a kneading reactor. In a kneader, the polymer gel formed during the polymerization of an aqueous monomer solution is continuously crushed, for example, using agitator shafts rotating in opposite directions, as described in WO 2001/38402. Therefore, the crushing of the polymer gel can be carried out before unloading the polymer gel from the polymerization reactor.

Another example of a preferred polymerization reactor is a conveyor belt. As a conveyor belt suitable for the method according to the present invention, any conveyor belt can be used, which experts in the field of technology consider suitable as a supporting material on which the aqueous monomer solution described above can be loaded and then polymerized to obtain a hydrogel.

A conveyor belt usually contains an infinitely moving conveyor belt passing over the supporting elements and at least two guide rollers, of which at least one is driven and adjustable. Optionally, a system is provided for unwinding and feeding a release sheet that can be used in sections on the upper surface of a conveyor belt. This system contains a system for supplying and dispensing reaction components, as well as optional radiation means located in the direction of movement of the conveyor belt after the supply and dispensing system, along with cooling and heating devices, as well as a polymer gel strand removal system located near the guide roller of the reverse conveyor branch tapes. In order to ensure complete polymerization with the highest possible product yield in a single pass per unit of time, in accordance with the present invention, upward supporting elements are arranged on both sides of the horizontal support elements, starting up in the delivery zone and dosing systems, support elements with their longitudinal axes intersect are located at a point under the upper branch, and which give the conveyor belt, supported by them, the shape of a suitable gutter. Thus, in accordance with the present invention, a conveyor belt in the vicinity of the reaction component supply system supports a plurality of support and support elements in the form of a gutter, which provide a configuration of the supplied reaction components in the form of a deep trough or plate. The desired shape of the gutter is determined by the shape and location of the supporting elements along the entire length of the path of the upper branch. In the area of introduction of the reaction components, the support elements should be located relatively close to each other, and in the next area, after initiation of the polymerization, the support elements can be located at a somewhat larger distance from each other. The angle of inclination of the supporting elements and the shape of

- 8 030945 cross sections of the supporting elements can be variable to align the initially deep gutter as it moves to the end of the polymerization part and re-bring it into a stretched state. In an additional embodiment, the implementation of the present invention, each support element is preferably formed by a cylindrical or spherical roller, able to rotate about its longitudinal axis. By changing the cross section of the roller, as well as the configuration of the roller, you can easily achieve the desired shape of the cross section of the chute. To ensure proper molding of the gutter from the conveyor belt, when it goes from a flat state to a gutter shape and when it returns back to a flat state, it is preferable to use a conveyor belt in a flexible longitudinal and transverse directions.

The tape can be made of various materials, although they should preferably meet the requirements of good tensile strength and flexibility, good fatigue strength at repeated bending stresses, good deformability and chemical resistance to individual components of the reaction under polymerization conditions. One material usually does not meet the specified requirements. Therefore, as the tape according to the present invention is usually used a multilayer material. Mechanical requirements can be met using a skeleton, such as woven inserts made from natural and / or synthetic fibers, or glass fibers, or steel cord. Chemical resistance can be achieved by coating, for example, polyethylene, polypropylene, polyisobutylene, halogenated polyolefins such as polyvinyl chloride or polytetrafluoroethylene, polyamides, natural or synthetic rubbers, polyester resins or epoxy resins. The preferred coating material is silicone rubber.

At the technological stage (vii) of the method according to the present invention, the polymer gel obtained in the polymerization reactor is optionally crushed to obtain particles of the polymer gel. Preferred polymer gel particles are particles selected from the group consisting of polymer gel strands, polymer gel flakes, and polymer gel lumps or a combination of at least two of them. The crushing device may be a polymerization reactor or part of a polymerization reactor, or a separate device, or both. Therefore, the crushing of the polymer gel can be carried out before, during or after unloading the polymer gel from the polymerization reactor. The preferred polymerization reactor, which is a crushing device, is a kneading reactor. When performing crushing in a polymerization reactor, the obtained particles of a polymer gel are preferably further crushed after being discharged from the polymerization reactor. If the polymerization reactor is a conveyor belt, crushing is preferably carried out after unloading the polymer gel in the form of a sheet of polymer gel from the conveyor belt in the crushing device, while the crushing device is a separate device. Preferably, the polymer gel sheet is discharged from the conveyor belt in the form of a continuous sheet that has a soft, semi-solid texture, and then sent to additional processing, such as crushing.

Crushing the polymer gel is preferably carried out in at least three stages:

In the first stage, a cutting machine is used, preferably a knife, for example a knife described in WO-A-96/36464, to cut the polymer gel into flat strips of gel, preferably from 5 to 500 mm long, preferably from 10 to 300 mm and particularly preferably from 100 up to 200 mm, height from 1 to 30 mm, preferably from 5 to 25 mm and particularly preferably from 10 to 20 mm, and also from 1 to 500 mm wide, preferably from 5 to 250 mm and particularly preferably from 10 to 200 mm;

in the second stage, a grinding device, preferably a crusher, is used to grind the gel strips into gel pieces, preferably from 3 to 100 mm long, preferably from 5 to 50 mm, up to 1 to 25 mm high, preferably from 3 to 20 mm, and also from 1 to 100 mm, preferably from 3 to 20 mm;

in the third stage, a (crushing) installation of a top is used, preferably of the cutter type, preferably having an auger and a plate with holes, where the screw pushes the product through the plate with holes to grind and grind the gel pieces for polymer gel particles, which are preferably smaller than the gel pieces.

Thereby, an optimum ratio of surface area to volume is achieved, which has a favorable effect on the drying characteristics at the technological stage (viii). Gel crushed in this way is particularly suitable for drying on tape. Three-stage crushing provides better air access due to air ducts located between the granulate particles.

At the technological stage (viii) of the method according to the present invention, the polymer gel is dried.

The drying of the polymer gel can be carried out in any dryer or kiln, which is considered suitable by those skilled in the art for drying the polymer gel or the polymer gel particles described above. As an example, rotary tube furnaces, fluidized bed dryers, disc dryers, rotary vane dryers and injectors can be mentioned.

- 9 030945 frared red dryers.

Belt dryers are particularly preferred. Belt dryer is a convection drying system for particularly gentle processing of products with free air access. The product to be dried is placed on an endless conveyor belt, which passes the gas, and is treated with a stream of heated gas, preferably air. The drying gas is recirculated so that it can become very highly saturated with multiple passes through the product bed. A certain part of the drying gas, preferably not less than 10%, more preferably not less than 15% and most preferably not less than 20% and preferably up to 50%, more preferably up to 40% and most preferably up to 30% of the gas per pass, is discharged from the dryer in as a highly saturated steam that carries a certain amount of water evaporated from the product. The temperature of the heated gas stream is preferably at least 50 ° C, more preferably at least 100 ° C and most preferably at least 150 ° C and preferably up to 250 ° C, more preferably up to 220 ° C and most preferably up to 200 ° C.

The size and design of the dryers depend on the processed product, production capacity and load during drying. Belt dryer can be implemented as a single belt, multiple belt system, multi-stage or multi-stage system. The present invention is preferably carried out using a belt dryer having at least one belt. Particularly preferred are single-belt dryers. To ensure optimal drying characteristics, the drying properties of water-absorbing polymers are separately determined on the tape as a function of the selected process parameters. For a particular product, choose the size of the holes and the size of the cells of the tape. There are also some options for surface optimization, such as electrolytic polishing or teflon coating.

The particles of the polymer gel to be dried are preferably applied to the belt of the belt dryer using a rotating belt. Feed height, i.e. the vertical distance between the rotary belt and the belt dryer belt is preferably not less than 10 cm, more preferably not less than 20 cm and most preferably not less than 30 cm and preferably up to 200 cm, more preferably up to 120 cm and most preferably up to 40 cm. Layer thickness Polymer gel particles to be dried on a 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, more preferably not more than 15 cm and most preferably not more than 12 cm. The belt speed of the belt dryer is 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 / s and preferably up to 0.05 m / s, more preferably up to 0.03 m / s and most preferably up to 0.025 m / s.

In addition, in accordance with the present invention, the gel is preferably dried to a water content in the range from 0.5 to 25 wt.%, Preferably from 1 to 10 wt.% And particularly preferably from 3 to 7 wt.% Relative to the dried polymer gel.

At the technological stage (ix) of the method according to the present invention, the dried polymer gel or particles of the dried polymer gel, or both, are ground to obtain particles of the water-absorbing polymer in the form of particles. The specified grinding includes the first stage of grinding in the first grinding device with obtaining the first crushed water-absorbing polymer particles. Then, the first ground water-absorbing polymer particles are fed to a holding device. The preferred holding device is a bunker. The specified grinding additionally includes an additional grinding stage in an additional grinding device with obtaining additional ground water-absorbing polymer particles.

The first grinding device and the additional grinding device may be any device that is considered suitable by those skilled in the art for grinding the above-described dried polymer gel or particles of the dried polymer gel. As an example of a suitable first grinding device and a suitable additional grinding device, a single-stage or multi-stage roller mill may be mentioned, preferably a two- or three-stage roller mill, a pin mill, a hammer mill, or a vibratory mill. In this process, the first grinding device is preferably selected to provide coarse grinding of the dried polymer gel compared to the additional grinding device, which is preferably selected to provide a finer grinding. Preferably, the first grinding device and the additional grinding device are selected so that the combined grinding of the dried polymer gel in the context of the first grinding stage and the additional grinding stage provides the required size distribution of the water-absorbing polymer particles.

At the technological stage (x) of the method according to the present invention, the additional ground particles of the water-absorbing polymer are sorted, preferably using suitable sieves. In this context, it is particularly preferable that after sorting the particles of a water-absorbing polymer, the content of polymer particles having a particle size less than 150 microns, the composition

- 10 030945 less than 10 wt.%, Preferably less than 8 wt.% And, in particular, less than 6 wt.%, And that the content of polymer particles having a particle size of more than 850 microns is also less than 10 wt.%, Preferably less than 8 wt.% And particularly preferably less than 6 wt.%. It is also preferable that after sorting the particles of the water-absorbing polymer, at least 30% by weight, more preferably at least 40% by weight and most preferably at least 50% by weight of the particles are in the range from 300 to 600 microns.

At the technological stage (xi) of the method according to the present invention, the surface of the additional crushed and sorted particles of the water-absorbing polymer is not necessarily treated. As a means for treating the surface of particles of a water-absorbing polymer, any means that experts in the art will consider appropriate for this purpose can be used. Examples of surface treatment include, for example, surface crosslinking, surface treatment with water-soluble salts, such as aluminum sulfate or aluminum lactate, surface treatment with inorganic particles, such as silicon dioxide, and the like. Preferably, the components used to treat the surface of the polymer particles (crosslinking agents, water soluble salts) are added to the particles of the water-absorbing polymer in the form of aqueous solutions. After mixing the particles with these aqueous solutions, they are heated to a temperature of from 150 to 230 ° C, preferably from 160 to 200 ° C to accelerate the surface crosslinking reaction.

In one embodiment of the present invention, the second residence time is from 120 to 180 minutes, preferably from 120 to 175 minutes, more preferably from 100 to 170 minutes, more preferably from 120 to 165 minutes, more preferably about 130 to 160 minutes, most preferably 140 to 155 minutes

In one of the embodiments of the present invention, the product D _{50 of the} diameter of additional crushed water-absorbing polymer particles and the second residence time is from 4x10 ³ to 100x10 ³ μm-min, preferably from 5x10 ³ to 100x10 ³ μm-min, more preferably from 5x10 ³ to 95x10 ³ micron-min, more preferably from 5x10 ³ to 9x10 ³ micron-min, more preferably from 5x10 ³ to 85x10 ³ micron-min, more preferably from 5x10 ³ to 80x10 ³ micron-min, more preferably from 5x10 ³ to 75x10 ³ micron min, most preferably from 54x10 ³ to 72x10 ³ μm-min.

In one embodiment of the present invention, the ratio of the sum of the first residence time and the second residence time to the water content of the dried polymer gel prior to the process step (ix) is from 10 to 100 min / wt.%, Preferably from 12 to 90 min / wt. , more preferably from 14 to 80 min / wt.%, more preferably from 16 to 70 min / wt.%, more preferably from 18 to 60 min / wt.%, more preferably from 19 to 50 min / wt.%, most preferably from 20 to 45 min. / wt.%.

In one embodiment of the present invention, the ratio D50 of the diameter of the first ground water-absorbing polymer particles to the second residence time is from 10 to 40 μm / min, preferably from 15 to 35 μm / min, most preferably from 19 to 29 μm / min.

In one embodiment, the implementation of the present invention at the technological stage (ix) after processing the first crushed water-absorbing polymer particles by holding in a holding device and before processing at least the first part of the first crushed water-absorbing polymer particles at an additional grinding stage in an additional grinding device, the first crushed water-absorbing polymer particles are sorted by size, separating the first part of the first ground water-absorbing polymer parts eggs from an additional part of the first ground water-absorbing polymer particles; however, an additional part of the first ground water-absorbing polymer particles is not subjected to an additional grinding stage in an additional grinding device. Preferably, an additional portion of the first ground water-absorbing polymer particles is at least partially subjected to process steps (x) or (xi), or both. Preferably, the particles of an additional part of the first ground water-absorbing polymer particles are characterized by a particle diameter of more than 800-900 μm, preferably more than 850 μm.

In one embodiment of the present invention, the first grinding device is an impact mill. A preferred impact mill contains a rotating element and a plurality of hammers, where each hammer is connected to a rotating element. Preferably, the dried polymer gel is ground by repeated exposure to said hammers.

In one embodiment of the present invention, the first grinding device comprises at least one, preferably at least two, more preferably at least three, more preferably at least 4, more preferably at least 5, more preferably at least 6, more preferably at least 7, more preferably at least 8, more preferably at least 9, more preferably at least 10, more preferably at least 11, more preferably at least

- 11 030945

12, more preferably at least 13, most preferably at least 14 rotating knives (knife) and at least one, preferably at least 2, more preferably at least 3, most preferably at least 4 fixed knives (knife) . Preferably the rotating knives are arranged in pairs. Preferably the fixed knives are arranged in pairs.

In one embodiment of the present invention, the holding device is a bunker. The preferred hopper is a storage tank used to supply granular materials with an inclined chute to restrict flow.

In one embodiment, the implementation of the present invention additional grinding device is a roller mill. The preferred roller mill contains at least 2, preferably at least 3, more preferably at least 4, more preferably at least 5, most preferably at least 6 rollers. In said process, the two rollers are preferably arranged as a pair comprising a roller and an opposite roller. Another preferred roller mill is a three-stage roller mill. A particularly preferred roller mill is a three-stage roller mill containing one pair of rollers for each of the three stages.

In one embodiment of the present invention, the polymer gel discharged at the technological stage (vii) contains water in an amount of 40-60 wt.%, Preferably 50-60 wt.%, More preferably 53-56 wt.% Relative to the polymer gel.

In one of the embodiments of the present invention, the polymer gel discharged at the technological stage (vii) is a sheet of polymer gel; where the specified sheet of polymer gel is characterized by a thickness of from 10 to 200 mm, preferably from 10 to 100 mm, more preferably from 15 to 75 mm, most preferably from 15 to 50 mm.

In one of the embodiments of the present invention, the polymer gel discharged at the technological stage (vii) is a sheet of polymer gel; where the specified sheet of polymer gel is characterized by a width of from 30 to 300 cm, preferably from 50 to 250 cm, more preferably from 60 to 200 cm, most preferably from 80 to 100 cm

In one embodiment of the present invention, the polymerization in step (vi) is carried out in the presence of a blowing agent. A blowing agent may be added to the aqueous monomer solution in one of the stages selected from the group consisting of stage (i), stage (ii), stage (iii), stage (iv), stage (v) and stage (iv) or in a combination of at least two of them. Preferably, a foaming agent is added to the monomer solution in step (i). A blowing agent must be added before or immediately after the initiation of the polymerization in step (vi). Particularly preferably, a blowing agent is added to the monomer solution after or simultaneously with the addition of an initiator or component of the initiator system. Preferably, the foaming agent is added to the monomer solution in an amount of from 500 to 4000 ppm by weight, preferably from 1000 to 3500 ppm by weight, more preferably from 1500 to 3200 ppm by weight, most preferably from 2000 to 3000 ppm by weight of the total weight of monomer solution .

A foaming agent is a substance capable of forming a cellular structure or pores, or both, by foaming during the polymerization of the monomers. The foaming process is preferably endothermic. The preferred endothermic foaming process is initiated by heat generated in an exothermic polymerization or cross-linking reaction, or in both reactions. A preferred blowing agent is a physical blowing agent, or a chemical blowing agent, or both. A preferred physical blowing agent is an agent selected from the group consisting of CFC, HCFC, hydrocarbon, and CO _2, or a combination of at least two of them. Preferred CO ₂ is liquid CO ₂ . The preferred hydrocarbon is a hydrocarbon selected from the group consisting of pentane, isopentane and cyclopentane, or a combination of at least two of them. Preferred chemical blowing agent is one selected from the group consisting of carbonate blowing agent, nitrite, peroxide, soda ash, oxalic acid derivative, aromatic azo compound, hydrazine, azide, N.N'-dinitrosoamide and organic blowing agent or a combination of least two of them.

A particularly preferred blowing agent is a carbonate blowing agent. Carbonate blowing agents that can be used in accordance with the present invention are described in US 5,118,719 A, incorporated herein by reference. A preferred carbonate blowing agent is a carbonate-containing salt or a bicarbonate-containing salt, or both. Another preferred carbonate blowing agent contains an agent selected from the group consisting of CO ₂ as a gas, CO ₂ as a solid, ethylene carbonate, sodium carbonate, potassium carbonate, ammonium carbonate, magnesium carbonate or magnesium hydroxycarbonate, calcium carbonate, barium carbonate, bicarbonate, their hydrates, other cations and natural carbonates, or a combination of at least two of them. Preferred

- 12 030945 natural carbonate is dolomite. The above carbonate foaming agents, dissolved or dispersed in the monomer solution, release CO ₂ when heated. A particularly preferred carbonate blowing agent is MgCO ₃ , which can also be represented by the formula (MgCO ₃ ) ₄ -Mg (OH) ₂ -5H ₂ O. Another preferred carbonate blowing agent is (NH ₄ ) ₂ CO ₃ . MgCO ₃ and (NH4) 2CO3 can also be used in mixtures. Preferred carbonate blowing agents are carbonate salts of polyvalent cations such as Mg, Ca, Zn, etc. Examples of such carbonate blowing agents are Na2CO3, K2CO3, (NH4) 2CO3, MgCO3, CaCO3, NaHCO3, KHCO3, NH4HCO3, Mg (HCO3) 2, Ca (HCO3) 2, ZnCO3, and BaCO3. Although some polyvalent transition metal cations can be used, some of them, such as the iron (III) cation, can cause staining and can undergo oxidation-reduction reactions or hydrolytic equilibrium in water. This can lead to difficulties in controlling the quality of the finished polymer product. In addition, other polyvalent cations, such as Ni, Ba, Cd, Hg, may be unacceptable due to their potentially toxic or skin-sensitizing effects.

The preferred nitrite is ammonium nitrite. The preferred peroxide is hydrogen peroxide. A preferred aromatic azo compound is a compound selected from the group consisting of triazene, arylazosulfones, arylazotriarylmethanes, hydrazo compounds, diazo ester and diazo aminobenzene, or a combination of at least two of them. The preferred hydrazine is phenylhydrazine.

The preferred azide is carbonyl azide or sulfonyl azide, or both. A preferred N.N'-dinitrosoamide is CI-dimethyl-NI-dinitrosoterephthalamide.

The contribution to the solution of at least one of the above objectives is provided by means of an apparatus for producing water-absorbing polymer particles in the process stream, comprising:

a) a first container adapted to receive an aqueous solution of a monomer containing at least one partially neutralized monoethylenically unsaturated monomer containing carboxylic acid groups (a1);

b) an additional container configured to receive at least one crosslinking agent (a3);

c) a mixing device, where the mixing device:

i) located after the first container and additional container, ii) made with the possibility of mixing the monomer solution and at least one crosslinking agent (a3);

a) a polymerization reactor, where the polymerization reactor:

i) is located after the first container and additional container, ii) configured to accommodate the aqueous monomer solution and at least one crosslinking agent (a3) during the polymerization of the monomers in the aqueous monomer solution, to form a polymer gel;

d) crushing device, where crushing device:

i) located after the first container and an additional container, ii) made with the possibility of crushing the polymer gel with the formation of particles of polymer gel,

e) belt dryer, where belt dryer:

i) is located after the crushing device, ii) made with the possibility of drying the particles of the polymer gel,

f) the first grinding device, where the first grinding device:

i) located after the belt dryer, ii) made with the possibility of processing the dried polymer gel particles in the first grinding stage to obtain the first crushed water-absorbing polymer particles, iii) made with the possibility of accommodating the dried polymer gel particles and the first crushed water-absorbing polymer particles obtained from them, during the first stay;

g) a holding device, where a holding device:

i) located after the first grinding device, ii) configured to accommodate the first crushed water-absorbing polymer particles during the second residence time;

h) additional grinding device, where additional grinding device:

i) located after the holding device, ii) configured to process at least the first part of the first ground water-absorbing polymer particles in an additional grinding stage to produce additional ground water-absorbing polymer particles;

- 13 030945 iii) configured to accommodate at least the first part of the first ground water-absorbing polymer particles and the additional ground water-absorbing polymer particles obtained from them during the third residence time;

j) the first sorter by size, where the first sorter by size:

i) located after the additional grinding device, ii) made with the possibility of sorting additional crushed particles of water-absorbing polymer;

where the second time is more than the first time;

where the second time is more than the third time.

In this process, the mixing device may be identical to the polymerization reactor. In addition, the polymerization reactor may be identical to the crushing device. Therefore, the mixing device, the polymerization reactor and the crushing device may be identical. Preferred components or devices, or both, of the equipment according to the present invention are made in accordance with the method according to the present invention. The preferred first grinding device is the first grinding device in accordance with the method according to the present invention. Preferred additional grinding device is an additional grinding device in accordance with the method according to the present invention. The preferred holding device is a holding device in accordance with the method of the present invention. The preferred first residence time is the first residence time in accordance with the method of the present invention. The preferred second residence time is the second residence time in accordance with the method of the present invention. The preferred third residence time is the third residence time in accordance with the method of the present invention. The preferred first screening device is a sieve that is considered suitable by those skilled in the art for screening additional ground water-absorbing polymer particles.

In one embodiment of the present invention, the device further comprises an additional screening device, where the additional screening device:

a) located after the holding device;

b) made with the possibility of sorting the size of the first crushed water-absorbing polymer particles, separating the first part of the first crushed water-absorbing polymer particles from an additional part of the first crushed water-absorbing polymer particles.

Preferred additional sorting device is a sieve, which specialists in this field of technology is considered suitable for separating the first part of the first ground water-absorbing polymer particles from the additional part of the first ground water-absorbing polymer particles. The preferred additional screening device comprises a grid having a mesh size of 18 to 25 US mesh, preferably 20 US mesh. Another preferred additional screening device comprises an additional grid having a mesh size of from 70 to 140 US mesh, preferably 100 US mesh.

The contribution to the solution of at least one of the above objectives is provided by the method for producing particles of a water-absorbing polymer in the device according to the present invention. Preferably, said process includes process steps (i) - (xi) according to the present invention.

The contribution to the solution of at least one of the above objectives is provided by using a particle of a water-absorbing polymer, which can be obtained by the method according to the present invention. An additional aspect of the present invention relates to a set of surface-crosslinked particles of a water-absorbing polymer, containing:

a) a chelating agent, in particular EDTA, in an amount of from 500 to 3000 ppm by weight, preferably from 1000 to 2000 ppm by weight;

b) polyalkylene glycol, in particular polyethylene glycol, in an amount of from 500 to 3000 ppm by weight, preferably from 1000 to 2000 ppm by weight; and

c) SiO ₂ in an amount of from 500 to 3000 ppm by weight, preferably from 1000 to 2000 ppm by weight, each value is expressed relative to the mass of the plurality of surface-crosslinked particles of the water-absorbing polymer.

In accordance with a further aspect of the present invention, a plurality of surface-crosslinked particles of a water-absorbing polymer further comprise Ag zeolite, preferably in an amount of from 0.0001 to 1 part by weight, more preferably from 0.001 to 0.5 part by weight. and most preferably from 0.002 to 0.01 parts by weight, each value is expressed relative to the total mass of the plurality of surface-crosslinked particles of the water-absorbing polymer.

The contribution to the solution of at least one of the above objectives is provided with a composite material containing a particle of a water-absorbing polymer, which can be obtained by the method according to the present invention.

- 14 030945

In one embodiment of the present invention, the composite material according to the present invention comprises a material selected from the group consisting of foam, a shaped article, fiber, foil, film, cable, sealing material, a moisture-absorbing hygienic article, a carrier for plant growth and fungi control agents, packaging material, soil additive, building material, or a combination of at least two of them. The preferred cable is a blue submarine cable. A preferred dehumidifying hygienic article is a product selected from the group consisting of a diaper, a tampon, and a sanitary pad or a combination of at least two of them. A preferred diaper is a baby diaper or a diaper for incontinent adults, or both.

The contribution to the solution of at least one of the above objectives is provided by a method for producing a composite material, where a particle of a water-absorbing polymer according to the present invention and a substrate, as well as an optional adjuvant, are brought into contact with each other.

The contribution to the solution of at least one of the above problems is provided with a composite material, which can be obtained by the method according to the present invention.

The contribution to the solution of at least one of the above objectives is provided by applying the water-absorbent polymer particle according to the present invention in a foam, a shaped article, a fiber, a foil, a film, a cable, a sealing material, a moisture-absorbing hygienic article, a carrier for plant growth regulators and fungi, packaging material, soil additive, controlled release of active compound or in building material.

Test methods.

In the present invention, the following test methods were used. In the absence of a test method, an ISO test method was used to measure the characteristics closest to the early filing date of the application for this invention. In the absence of an ISO test method, the EDANA test method was used that was closest to the early filing date of the application for this invention. In the absence of specific measurement conditions, ambient temperature and pressure (SATP) were used, i.e. temperature 298.15 K (25 ° C, 77 ° F) and an absolute pressure of 100 kPa (14.504 psi, 0.986 atm).

Water content

The water content of the particles of the water-absorbing polymer after drying was determined by the Karl-Fisher method.

The method of carrying out the invention

Examples

Further, the present invention is explained in more detail using the examples and drawings given as an example, which do not limit it.

A) Preparation of monomer solution of partially neutralized acrylic acid.

0,4299 wt.h. water was mixed in a suitable container with 0.27 wt.h. acrylic acid and 0.0001 wt.h. hydroquinone monomethyl ester (MEHQ). 0.2 wt.h. 48 wt.% Sodium hydroxide solution. A solution of sodium acrylate monomer was obtained with a neutralization degree of 70 mol%.

The sodium acrylate monomer solution was optionally degassed with nitrogen.

B) Polymerization of the monomer solution.

In the container were mixed 1 wt.h. the monomer solution obtained in stage A), with 0.001 wt.h. trimethylolpropane triacrylate as a crosslinking agent, 0.001 wt.h. sodium peroxodisulfate as the first component of the initiator, 0,000034 wt.h. 2,2-dimethoxy-1,2-diphenylethan-1-one (Ciba® Irgacure® 651 manufactured by Ciba Specialty Chemicals Inc., Basel, Switzerland) as the second initiator component, up to 0.1 wt.h. particles of acrylic acid (with a particle size of less than 150 microns) to obtain a mixed solution. When adding a blowing agent in accordance with the presented table. 1-4 to the stirred solution was added 0.1 wt.h. sodium carbonate by weight of the total mixed solution.

A sufficient amount of the mixed solution was subjected to additional processing to obtain a polymer gel, and then subsequent particles of a water-absorbing polymer, and then surface-crosslinked particles of a water-absorbing polymer, and then a further processed water-absorbing product. Details of the additional processing are presented below.

Then the mixed solution was placed on a belt conveyor belt reactor and initiated the polymerization by UV radiation. The conveyor belt was at least 20 m long and 0.8 m wide. The conveyor belt was shaped like a gutter to hold the solution on the belt before and during the polymerization. The dimensions of the conveyor belt and the transport speed of the conveyor belt were chosen so as to obtain a polyacrylic acid gel at the far end of the belt. At the end of this stage, a water-absorbent polymer gel was obtained. The polymer gel had a water content

- 15 030945 approximately 52 wt.% From the total mass of the polymer gel.

C) Crushing and drying the polymer gel.

The polymer gel formed strands of polymer gel, which was unloaded from the conveyor belt and crushed in three stages: the rubbery gel of polyacrylic acid was cut into flat strips of gel with a knife. The gel strips had a length of 10 to 20 cm, a height of 10 to 200 m and a width of 10 to 200 mm, then used a crusher to cut the strips into gel pieces with a length of 5 to 50 mm, a height of 3 to 20 mm, and a width of 3 to 20 mm, then the gel pieces were forced through a mixer with a grinder to grind the gel pieces to obtain gel particles having a length of 3 to 20 mm, a height of 3 to 20 mm, and a width of 3 to less than 20 mm.

The crushed gel was dried on a belt dryer at a temperature of 180 ° C to a water content of 5 wt.% Relative to the dried polymer gel. The belt of the belt dryer contained holes through which hot air under pressure was injected into the polymer gel through nozzles. The gel on the tape was also blown off with hot air from above.

D) Grinding and sorting by size.

The dried polymer gel was crushed in three stages. First, the dried polymer gel was passed through a Herbold HGM 60/145 granulator (HERBOLD Meckesheim GmbH) as the first grinding device. The dried polymer gel was kept for the first time in a specified first grinding device. Then the obtained particles of the dried polymer gel was kept in the hopper during the second residence time. Then, the particles of the dried polymer gel were additionally crushed in a roller mill as an additional grinding device to form water-absorbing polymer particles. The particles of the dried polymer gel / water-absorbing polymer particles were kept for the third time in a roller mill. Type, i.e. The number of stages of the roller mill is shown below. The values of the first, second and third residence time for specific examples and comparative examples are presented below.

Water-absorbing polymer particles were sieved through drum sieves having several grids. The following grid sizes were used: from 20, 30, 40, 50, 60 to 100 US mesh. At least 50 wt.% Of the obtained water-absorbing polymer particles had a particle size of from 300 to 600 microns. Less than 5 wt.% Of water-absorbing polymer particles in the examples according to the present invention had a size of less than 150 microns, less than 5 wt.% Of water-absorbing polymer particles in the examples according to the present invention had a particle size of more than 850 microns. The resulting water-absorbing polymer particles were called the precursor I.

E) Treatment with silica.

At the processing stage, the precursor I was mixed in a disk mixer with about 0.01 wt.h. (± 10%) silicon dioxide (SiO ₂ ) relative to the total mass of the precursor I and SiO ₂ . Silicon dioxide was used in the form of Sipemat® 22 manufactured by Evonik Industries AG, Essen, Germany. When mixing the precursor I with SiO _{2, the} temperature of the precursor was still more than 80-100 ° C, preferably 100 ° C. Received predecessor II.

F) Surface stitching.

In the next stage, 1 wt.h. predecessor II was mixed with 0,003 wt.h. (± 10%) surface cross-linking agent relative to the total mass of the mixture of precursor II and a cross-linking agent. The surface crosslinking agent consisted of 19 wt.% Water, 40 wt.% Ethylene glycol diglycidyl ether, 1 wt.% Na ₂ SO ₃ , 40 wt.% Polyethylene glycol with a molecular weight of 400 g / mol, all values relative to the total amount of the crosslinking agent. The ingredients of the crosslinking agent were mixed in a linear static mixer. The crosslinking agent was mixed in a CoriMix® CM 350 annular blender (Gebriider Lodige Mascheninenbau GmbH, Paderborn, Germany) with its predecessor II. The mixture was heated to a temperature of from 130 to 160 ° C. The mixture was then dried in a paddle dryer Andritz Gouda Paddle Dryer, preferably of the type GPWD12W120 manufactured by Andritz AG, Graz, Austria, for 45 minutes at a temperature of 130 to 160 ° C. Received surface-linked particles of absorbent polymer.

In the fluidized bed cooler, the temperature of the surface-crosslinked particles of the absorbent polymer was lowered to less than 60 ° C to form cooled, surface-crosslinked particles of the absorbent polymer called precursor III.

G) Additional processing.

Then 1 wt.h. the precursor III was mixed with 0.005 wt.h. Ag zeolite. Then the mixture was sieved. The sieve was chosen to separate the agglomerates of cooled, surface-crosslinked particles of absorbent polymer having a particle size greater than 850 microns. At least 50 wt.% Of the surface-crosslinked particles of the absorbent polymer had a particle size of from 300 to 600 microns. Less than 5 wt.% Of the crosslinked absorbent polymer particles in the examples according to the present invention were less than 150 microns, less than 5 wt.% Of the crosslinked absorbent polymer particles in the examples according to the present invention had a particle size of more than 850 microns. By

- 16 030945 radiated additionally treated surface-crosslinked particles of a water-absorbing polymer.

Used the following scale to compare the measurement results of the parameters presented in table. 1-4, for examples and comparative example. In the order shown below, the measurement results are improved from left to right: -, -, 0, +, ++, +++, ++++.

In comparative example 1 and in examples 1-4, the first grinding device was a Herbold type granulator SML 60/145-SX7-2 manufactured by Herbold Meckesheim GmbH, Meckesheim, Germany. In addition, the first residence time in said first grinding device was kept constant for 1 minute, the third time in the additional grinding device was kept constant for 1 minute, D50 of the first crushed water-absorbing polymer particles was kept constant, and the water content in the dried polymer gel was kept until the first grinding constant, at 5 wt.% from the dried polymer gel. In each case, the additional grinding device was a roller mill. The number of rollers and, therefore, the number of grinding stages in an additional grinding device (number of rollers divided by 2) are presented in table. one.

Table 1 Required maintenance of additional grinding device and the number of small particles formed for various additional grinding devices and various second residence time, as well as depending on the use of the foaming agent

Second stay Additional grinding device Blowing agent Work time additional grinding device to maintenance The amount of fine particles formed during grinding Comparative Example 1 30 s 4-roller mill not ++ Example 1 30 min. 4-roller mill not 0 + Example 2 120 min 4-roller mill not ++ + Example 3 120 min 4-roller mill carbonate sodium +++ Example 4 120 min 6-roller mill * carbonate sodium +++ +

* Bauermeister roller crusher type SWR 350.1x1800, three-stage crusher manufactured by Bauermeister Zerkleinerungstechnik GmbH, Norderstedt, Germany.

In comparative example 1, the second residence time is 30 seconds, which is less than the first and third residence times. A roller mill having 4 rollers for 2 stages of grinding was used as an additional grinding device. In example 1 used the same roller mill. However, the second residence time in the bunker was set at 30 minutes, which is more than the first and third residence times. This led to a significant increase in the period of operation before stopping for the maintenance of an additional grinding device (4-roller mill). The number of small water-absorbing polymer particles having a size of less than 150 microns, obtained after the first and additional grinding, was slightly higher than in comparative example 1. In example 2, the second residence time was further increased to 120 minutes. This led to an additional increase in working time. The amount of fine particles formed was comparable to Example 1. In addition, a blowing agent (sodium carbonate) was used in Example 3. This led to an increase in the number of fine particles formed. However, the working time was further increased. In example 4, a 6-roller mill was used as an additional grinding device. This led to a decrease in the number of fine particles to the level of examples 1 and 2, while maintaining the working time at the level of example 3. Therefore, example 4 shows, in general, the best results.

- 17 030945

Further, X is the ratio of D ₅₀ first ground water-absorbing polymer particles to the second residence time; Y is the product of D ₅₀ additional ground water-absorbing polymer particles for the second residence time and Z is the ratio of the sum of the first residence time and the second residence time to the water content in the dried polymer gel before grinding. In the following examples 5-13 according to the present invention, the second residence time was kept constant at 120 minutes and the first residence time was kept constant at 1 minute. In addition, used the first and additional grinding device according to example 2.

table 2

The working time of the 4-roller mill and the required volume of the hopper depending on the use of the blowing agent and the parameter X

X [μm / min.] Foaming agent Work time additional grinding device to maintenance Required bunker volume Example 5 five not ++ - Example 6 15 not ++ - Example 7 20 not + + Example 8 20 carbonate sodium ++ +

In example 5, X is equal to 5. In the continuous process of obtaining water-absorbing polymer particles, the required volume of the bunker is too large. Increasing X to 15 in Example 6 leads to a decrease in the required bunker volume. The working time until maintenance of the roller mill remains constant. In example 7, X is equal to 20, which leads to an additional decrease in the volume of the bunker, as well as to a small decrease in working time. The use of a blowing agent in addition to example 7, as made in example 8, leads to an increase in working time to the level of examples 5 and 6.

Table 3

The working time of the 4-roller mill, depending on the application of the blowing agent and the parameter Y

Y [μm · min.] Blowing agent Work time additional grinding device to maintenance Example 8 20 10 ³ not + Example 9 4510 ³ not ++ Example 10 60 10 ³ not +++ Example and 60 10 ³ sodium carbonate ++++

In tab. 3 shows that increasing Y from 20x10 ³ to 60x10 ³ leads to an increase in working hours before the need arises for maintenance of a 4-roller mill. In addition, the use of a blowing agent causes an additional increase in the specified working time.

- 18 030945

Table 4

The working time of the 4-roller mill depending on the use of the blowing agent and the parameter Z

Z [min / wt.%] Foaming agent Work time additional grinding device to maintenance Example and four not + Example 12 15 not ++ Example 13 thirty not +++ Example 14 thirty carbonate sodium ++++

In tab. 4 shows that increasing Z from 4 to 30 leads to an increase in working hours before the need for maintenance of a 4-roller mill arises. In addition, the use of a blowing agent causes an additional increase in the specified working time.

FIG. 1 is a flow chart illustrating steps 101-111 of process 100 for producing water-absorbing polymer particles according to the present invention. In the first stage 101, an aqueous monomer solution is provided containing at least one partially neutralized monoethylenically unsaturated monomer containing carboxylic acid groups ((X1) and at least one crosslinking agent (a3). Preferably the aqueous monomer solution is an aqueous solution of partially neutralized acrylic acids, additionally containing a crosslinking agent. In the second step 102, fine particles of a water-absorbing polymer can be added to the aqueous solution of the monomer. In the third step 103 to the aqueous A monomer solution is added with a polymerization initiator or at least one component of a polymerization initiator system that contains two or more components. In the fourth stage, the oxygen content in the monomer aqueous solution is reduced by passing nitrogen through the monomer aqueous solution. In the fifth stage, the monomer solution is loaded onto a tape ribbon polymerization reactor as a polymerization reactor 604.

The belt is an endless conveyor belt. In the sixth stage 106, the aqueous monomer solution is polymerized into a polymer gel. In the seventh stage 107, the polymer gel is discharged from the belt. Then the polymer gel is crushed to obtain particles of a polymer gel. In the eighth stage 108, particles of a polymer gel are loaded onto a belt of a belt dryer, and then dried at a temperature of about 120-150 ° C. The dried particles 401 of the polymer gel are discharged from the belt dryer, and then, in the ninth stage, 109 are ground to form water-absorbing polymer particles. The specified grinding includes processing the particles 401 of the dried polymer gel in the first grinding stage in the first grinding device 402 to obtain the first crushed water-absorbing polymer particles 403, keeping the first crushed water-absorbing polymer particles 403 during the residence time in the holding device 404 and then processing the first part 405 of the first crushed water-absorbing polymer particles 403 at an additional grinding stage in an additional grinding device 406 to obtain Additional crushed water-absorbing polymer particles 406. In this method, the particles 401 of the dried polymer gel and the first crushed water-absorbing polymer particles 403, obtained from the particles 401 of the dried polymer gel, generally stand 407 for the first time in the first grinding device 402, the first crushed water-absorbing the polymer particles 403 are kept for a second time 408 staying in the holding device 404, and the first part 405 of the first ground water-absorbing polymer particles 403 and additional crushed water-absorbing polymer particles 406, obtained from the first crushed water-absorbing polymer particles 403, generally stand for the third time 409 stays in the additional grinding device 405. In this method, the second time 408 stays longer than the first time 407 stays, and the second time 408 stays longer than the third time 409 stays. At the tenth stage 110, the additional ground water-absorbing polymer particles 406 are sorted by size using a sorting device 507 to produce additional ground and screened water-absorbing polymer particles having a well-defined particle size distribution. At the eleventh stage 111, the surface of crushed and sorted water-absorbing polymer particles is processed for surface stitching.

- 19 030945

FIG. 2 is a flow chart illustrating steps 101-111 of process 100 for producing water-absorbing polymer particles according to the present invention. Process 100 shown in FIG. 2 is the same as process 100 of FIG. 1, with the third process stage 103 and the fourth process stage 104 overlapping in time. When a polymerization initiator is added to an aqueous monomer solution, nitrogen is passed through the monomer aqueous solution to reduce its oxygen content.

FIG. 3 is a flow chart illustrating steps 101, 103, 105-110 of process 100 for producing water-absorbing polymer particles according to the present invention. Process 100 depicted in FIG. 3 is the same as process 100 of FIG. 1, with the second stage 102, the fourth stage 104 and the eleventh stage 111 being absent in process 100 in accordance with FIG. 3

FIG. 4 shows a flow sheet of a process step (ix) 109 according to the present invention. The dried polymer gel 401, obtained on a belt dryer 506, is fed to the first grinding device 402 in a first grinding stage. The first grinding device 402 is a Herbold granulator (type SML 60/145-SX7-2 manufactured by Herbold Meckesheim GmbH, Meckesheim, Germany). Thus, the first crushed water-absorbing polymer particles 403 are obtained from the dried polymer gel 401. The said dried polymer gel 401 and the first crushed water-absorbing polymer particles 403 as a whole are kept for the first time 408 of being in the first grinding device 402. The first time 408 of stay is approximately 3 min. Then, the first ground water-absorbing polymer particles 403 are supplied to a holding device 404, which is a bunker. The first crushed water-absorbing polymer particles 403 are kept for a second time of 409 stay of about 150 minutes in a holding device 404. Then the first part 405 of the first crushed water-absorbing polymer particles 403 is fed to an additional grinding device 406, which is a Bauermeister roller crusher (SWR type 350.1x1800, three-stage crusher manufactured by Bauermeister Zerkleinerungstechnik GmbH, Norderstedt, Germany), where the first part of 405 first ground water-absorbing polymer hours egg 403 is further pulverized to obtain additional particulate water-absorbing polymeric particles 407, having the desired particle size distribution. The first part 405 of the first ground water-absorbing polymer particles 403 and the additional ground water-absorbing polymer particles 407 are generally kept for a third residence time of 410 of about 3 minutes in an additional soaking device 406.

FIG. 5 is a flow chart of another process step (ix) 109 according to the present invention. Technological stage (ix) 109 is the same as in FIG. 4, except that after keeping the first ground water-absorbing polymer particles 403, said first ground water-absorbing polymer particles 403 are fed to an additional grinding device 501, which is a sieve. Sifting the first crushed water-absorbing polymer particles 403, separating the first part 405 of the first crushed water-absorbing polymer particles 403 from an additional part 502 of the first crushed water-absorbing polymer particles. Additional portion 502 is then fed to additional process steps, such as process step (x) or (xi), or both. The additional part 502 of the first crushed water-absorbing polymer particles 403 is not subjected to an additional grinding step in the additional grinding device 406. The first part 405 of the first crushed water-absorbing polymer particles 403 is fed to the additional grinding device 406, as described for FIG. four.

FIG. 6 is a block diagram of an apparatus 600 for producing water-absorbent polymer particles according to the present invention. The arrows show the direction of the process stream 608 for the production of water-absorbing polymer particles. The device 600 comprises a first container 601, an additional container 602, a downward mixing device 603, a downstream polymerization ribbon reactor as the polymerization reactor 604, a downstream crushing device 605, a downward belt dryer 606, a downward grinding device 402, a downward holding device 404, a downward additional grinding device 402 406 and a downstream first sorting device 607, each of which corresponds to the present invention.

FIG. 7 is a block diagram of another apparatus 600 for preparing water-absorbent polymer particles according to the present invention. The arrows show the direction of the process stream 608 for the production of water-absorbing polymer particles. The device 600 comprises a first container 601, an additional container 602, a downward mixing device 603, a downstream polymerization ribbon reactor as the polymerization reactor 604, a downstream crushing device 605, a downward belt dryer 606, a downward first grinding device 402, a downstream grinding device 404, a downstream grinding mill device 501, downward additional grinding device 406 and downward first sorting device 607, each of which corresponds to us oyaschemu invention.

- 20 030945

Although the present invention is described in relation to what is currently considered practical illustrative implementation options, it should be understood that the present invention is not limited to the described implementation options, but rather, is intended to cover various modifications and equivalent layout patterns that are part of the general idea. and the scope of the attached claims.

Claims (13)

CLAIM 1. A method of obtaining a water-absorbing polymer particles, comprising the following process steps: (i) obtaining an aqueous solution of a monomer containing at least one partially neutralized monoethylenically unsaturated monomer containing carboxyl groups (a1) and at least one crosslinking agent (a3); (ii) adding a polymerization initiator or at least one component of a polymerization initiator system, which contains two or more components, to an aqueous solution of a monomer; (iii) loading the aqueous monomer solution into the polymerization reactor (604); (iv) polymerization of monomers in an aqueous solution of monomer in a polymerization reactor (604); (v) discharging the polymer gel from the polymerization reactor (604); (vi) drying the polymer gel; (vii) processing: a) the dried polymer gel (401) in the first grinding stage in the first grinding device (402) to obtain the first crushed water-absorbing polymer particles (403); b) first ground water-absorbing polymer particles (403) by keeping in a holding device (404); then c) at least the first part (405) of the first ground water-absorbing polymer particles (403) at an additional grinding stage in the additional grinding device (406) to produce additional ground water-absorbing polymer particles (407); (viii) sorting by size of the additional ground water-absorbing polymer particles (407), where at the technological stage (vii) the dried polymer gel (401) and the first ground water-absorbing polymer particles (403) obtained from the dried polymer gel (401) are kept for first time (408) stay in the first grinding device (402); the first ground water-absorbing polymer particles (403) are kept for a second time (409) stay in the holding device (404); at least the first part (405) of the first ground water-absorbing polymer particles (403) and the additional ground water-absorbing polymer particles (407), obtained from at least the first part (405) of the first ground water-absorbing polymer particles (403), are kept in the third time (410) stay in additional grinding device (406), where the second time (409) stay more than the first time (408) stay; the second time (409) stay more than the third time (410) stay. 2. The method according to claim 1, characterized in that the second time (409) stay ranges from 120 to 180 minutes 3. The method according to claim 1 or 2, characterized in that the product D _{50 of the} diameter of the additional ground water-absorbing polymer particles (407) and the second residence time (409) ranges from 40x10 ³ to 100x10 ³ μm-min. 4. The method according to any of the preceding paragraphs, characterized in that the ratio of the sum of the first time (408) stay and the second time (409) stay to the water content in the dried polymer gel (401) to the technological stage (vii) is from 10 to 100 minutes /mas.%. 5. The method according to any of the preceding paragraphs, characterized in that the ratio D _{50 of the} diameter of the first ground water-absorbing polymer particles (403) to the second residence time (409) ranges from 10 to 40 μm / min. 6. The method according to any of the preceding paragraphs, characterized in that at the technological stage (vii) after keeping the first crushed water-absorbing polymer particles (403) in the holding device (404) and before processing at least the first part (405) of the first crushed water-absorbing polymer particles (403) at an additional grinding stage in an additional grinding device (406) the first crushed water-absorbing polymer particles (403) are sorted by size, separating the first part (405) of the first crushed water-absorbing their polymer particles (403) from an additional part (502) of the first ground water-absorbing polymer particles (403), where the additional portion (502) of the first ground water-absorbing polymer particles (403) is not subjected to an additional grinding stage in the additional ground - 21 030945 common device (406). 7. An apparatus for producing water-absorbing polymer particles in a process stream (608), comprising: a) a first container (601) configured to receive an aqueous monomer solution containing at least one partially neutralized monoethylenically unsaturated monomer containing carboxyl groups (a1); b) an additional container (602), configured to receive at least one crosslinking agent (a3); c) a mixing device (603), where a mixing device (603): i) is located after the first container (601) and the additional container (602), ii) configured to mix the monomer solution and at least one crosslinking agent (a3); d) a polymerization reactor (604), where the polymerization reactor (604): i) is located after the first container (601) and the additional container (602), ii) is adapted to accommodate an aqueous solution of monomer and at least one crosslinking agent (a3) during the polymerization of monomers in an aqueous solution of monomer with the formation of a polymer gel; e) crushing device (605), where crushing device (605): i) located after the first container (601) and the additional container (602), ii) made with the possibility of crushing the polymer gel with the formation of particles of the polymer gel; f) belt dryer (606), where belt dryer (606): i) located after the crushing device (605), ii) made with the possibility of drying the particles of the polymer gel; g) the first grinding device (402), where the first grinding device (402): i) located after the belt dryer (606), ii) configured to process the particles (401) of the dried polymer gel in the first grinding stage to produce the first crushed water-absorbing polymer particles (403), iii) adapted to contain the particles (401) of the dried polymer the gel and the first crushed water-absorbing polymer particles (403) obtained from them, during the first time (408) stay; h) a holding device (404), where a holding device (404): i) located after the first grinding device (402), ii) adapted to accommodate the first crushed water-absorbing polymer particles (403) during the second residence time (409); j) an additional grinding device (406), where an additional grinding device (406): i) located after the holding device (404), ii) configured to process at least the first part (405) of the first crushed water-absorbing polymer particles (403) at an additional grinding stage with obtaining additional crushed water-absorbing polymer particles (407), iii ) made with the possibility of accommodating at least the first part (405) of the first crushed water-absorbing polymer particles (403) and additional crushed water-absorbing polymer particles (407), obtained from them, for a third his residence time (410); k) the first sorting device (607), where the first sorting device (607): i) located after the additional grinding device (406), ii) made with the possibility of sorting additional crushed water-absorbing polymer particles (407), where the second time (409) stay more than the first time (408) stay; the second time (409) stay more than the third time (410) stay. 8. The method of obtaining water-absorbing polymer particles according to any one of claims 1 to 6, using the device according to claim 7. 9. Water-absorbing polymer particle obtained by the method according to any one of claims 1 to 6 or 8. 10. Composite material containing water-absorbing polymer particle according to claim 9. 11. A method for producing a composite material in which the water-absorbing polymer particle according to claim 9 and the substrate are brought into contact with each other. 12. Composite material obtained by the method according to claim 11. 13. The use of a water-absorbing polymer particle according to claim 9 in a moisture-absorbing hygienic article for absorbing aqueous liquids. - 22 030945 FIG. one FIG. 2 FIG. 3 FIG. four - 23 030945 FIG. five FIG. 6 FIG. 7