EA031397B1 - Process and device for the preparation of water-absorbent polymer particles, use of particles, composite material and process for the preparation thereof - Google Patents

Abstract

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

Description

The present invention relates generally to a method for producing water-absorbing polymer particles, as well as to a device for producing water-absorbing polymer particles, a composite material containing water-absorbing polymer particles, and a method for producing it.

031397 Bl

031397 B1

Technical field

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, also known as superabsorbent polymers (SAPs), are water-insoluble cross-linked polymers that can absorb large amounts of aqueous fluids, especially body fluids, more specifically urine or blood, with swelling and hydrogel formation, as well as retain these fluids with 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, in general, is carried out by free radical polymerization of monomers containing an acidic 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.

Continuous polymerization processes are usually carried out in a polymerization reactor under certain conditions. Often the polymerization reactor is a ribbon polymerization reactor. A conventional ribbon polymerization reactor contains a conveyor belt adapted to transfer during the polymerization an aqueous monomer solution which contains monomers containing an acid group. Such a conveyor belt is described in EP 0955086 B1.

Description

Technical problem

The main disadvantage of these methods of obtaining water-absorbing polymer particles is the high content of residual monomer, in particular, when used in diapers. Residual monomers that remain in water-absorbing polymer particles can cause skin irritation with the particular use of diapers.

Technical solution

In general, the object of the present invention is to at least partially overcome the drawback inherent in the prior art in the context of producing water-absorbing polymer particles.

The object of the present invention is to provide a method for producing water-absorbing polymer particles that can be used in diapers with a reduced ability to cause skin irritation. An additional challenge is to provide water-absorbing polymer particles with a low content of residual monomer. In addition, the challenge is to provide a device suitable for obtaining water-absorbing polymer particles with a low content of residual monomer.

An additional object of the present invention is to provide a water-absorbing polymer particle obtained by a method having at least one of the above advantages, where the water-absorbing polymer particle demonstrates no degradation in quality. 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. An additional object of the present invention is to provide

- 1 031397 device for obtaining water-absorbing polymer particles in a manner having at least one of the above advantages.

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.

The method of obtaining water-absorbing polymer particles includes technological stages:

(i) obtaining an aqueous monomer solution containing at least one partially neutralized, monoethylenically unsaturated monomer containing carboxylic acid groups (α1), and at least one crosslinking agent (α3);

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

(iv) an optional reduction in the oxygen content of the aqueous monomer solution;

(v) loading the aqueous monomer solution into the polymerization reactor (400);

(vi) polymerizing monomers in an aqueous solution of monomer in a polymerization reactor (400) to form a polymer gel;

(vii) discharging the polymer gel from the polymerization reactor (400) and optionally crushing the polymer gel;

(viii) drying the optionally crushed polymer gel;

(ix) grinding the dried polymer gel to form water-absorbing polymer particles;

(x) sorted by size of ground water-absorbing polymer particles; and (xi) optional surface treatment of crushed and sized water-absorbing polymer particles;

where at the technological stage (i) obtaining an aqueous solution of the monomer further includes the steps:

(11) providing the first part of acrylic acid; and (12) bringing into contact the first part of acrylic acid with hydroxide in the first stage of bringing into contact to obtain the first acrylate phase, where the first acrylate phase has a pH of 10 or more, where the first acrylate phase has a degree of neutralization of at least 0.95; and (13) bringing into contact the first acrylate phase with an additional part of acrylic acid in the second stage of bringing into contact with obtaining a monomer solution, where the additional part of acrylic acid has a water content less than the water content in the first acrylate phase, where the monomer solution has a pH less than the pH of the first acrylate phase, where the monomer solution has a degree of neutralization from 0.5 to 0.9;

where the content of acrylate and acrylic acid in an aqueous solution of the monomer is from 30 to 50 wt.%, each value relative to the total mass of the aqueous solution of monomer.

A device for obtaining water-absorbing polymer particles in the process stream contains:

a) a first container (501), adapted to contain acrylic acid;

b) a second container (502), configured to accommodate a metal hydroxide;

c) a cooling device (503), where a cooling device (503):

i) located after the second container (502), ii) made with the possibility of cooling the metal hydroxide;

d) the first mixing device (504), where the first mixing device (504):

i) located after the first container (501) and the cooling device (503), ii) is equipped with a cooler and powered mixing devices;

e) the third container (505), where the third container (505):

i) located after the first mixing device (504), ii) adapted to receive an aqueous monomer solution containing at least one partially neutralized, monoethylenically unsaturated monomer containing carboxylic acid groups (α1);

f) a fourth container (506), configured to receive at least one crosslinking agent (α3);

g) the second mixing device (507), where the second mixing device (507):

i) located after the third container (505) and the fourth container (506), ii) made with the possibility of mixing the monomer solution and at least one crosslinking agent (α3);

h) a polymerization ribbon reactor (400), where the polymerization ribbon reactor (400):

i) is located after the second mixing device (507), ii) is adapted to accommodate an aqueous monomer solution and at least one crosslinking agent (α3) during the polymerization of the monomers in the aqueous monomer solution to form a polymer gel;

j) the crushing device (508), where the crushing device (508):

i) located after the ribbon polymerization reactor (400), ii) made with the possibility of crushing the polymer gel;

k) belt dryer (509), where belt dryer (509):

i) is located after the crushing device (508), ii) is made with the possibility of drying the polymer gel;

l) grinding device (510), where grinding device (510):

i) located after the belt dryer (509), ii) made with the possibility of grinding the dried polymer gel with getting water-absorbing polymer particles;

m) sorting device (511), where the sorting device (511):

i) located after the crushing device (510), ii) made with the possibility of sorting the crushed particles of water-absorbing polymer.

Beneficial effects

Water absorbing polymer particles are presented which can be used in diapers with a reduced ability to cause skin irritation and with a low content of residual monomer, as well as a composite material containing the specified water absorbing polymer. In addition, a device is presented suitable for the production of water-absorbing polymer particles with a low content of residual monomer.

Description of figures

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 diagram of basic settings of a polymerization belt reactor according to the present invention; and FIG. 5 is a block diagram of an apparatus for producing water-absorbent polymer particles according to the present invention.

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)

112 stage (i1)

113 stage (i2)

114 stage (i3)

400 polymerization reactor; ribbon polymerization reactor

401 tape

402 guide roller

403 direction of movement of the polymer gel on the tape

404 direction opposite to the direction of movement of the polymer gel on the tape

405 longitudinal directions

406 transverse directions

500 device for producing particles of water-absorbing polymer

501 first container

502 second container

- 3 031397

503 cooling device

504 first mixing device

505 third container

506 fourth container

507 second mixing device

508 crushing device

509 belt dryer

510 grinding device

511 sorting device

512 process flow

The best way to exercise

The contribution to the solution of at least one of these tasks is made using the method (100) of obtaining water-absorbing polymer particles, including the technological stages:

(i) obtaining an aqueous monomer solution containing at least one partially neutralized, monoethylenically unsaturated monomer containing carboxylic acid groups (α1), and at least one crosslinking agent (α3);

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

(iv) an optional reduction in the oxygen content of the aqueous monomer solution;

(v) loading the aqueous monomer solution into the polymerization reactor (400);

(vi) polymerizing monomers in an aqueous solution of monomer in a polymerization reactor (400) to form a polymer gel;

(vii) discharging the polymer gel from the polymerization reactor (400) and optionally crushing the polymer gel;

(viii) drying the optionally crushed polymer gel;

(ix) grinding the dried polymer gel to form water-absorbing polymer particles;

(x) sorted by size of ground water-absorbing polymer particles; and (xi) optional surface treatment of crushed and sized water-absorbing polymer particles;

where at the technological stage (i) obtaining an aqueous solution of the monomer further includes the steps:

(11) providing the first part of acrylic acid; and (12) bringing into contact the first part of acrylic acid with hydroxide in the first stage of bringing into contact to obtain the first acrylate phase, where the first acrylate phase has a pH of 10 or more, where the first acrylate phase has a degree of neutralization of at least 0.95, preferably at least 0.98, more preferably at least 0.99; and (13) bringing into contact the first acrylate phase with an additional part of acrylic acid in the second stage of bringing into contact with obtaining a monomer solution, where the additional part of acrylic acid has a water content less than the water content in the first acrylate phase, where the monomer solution has a pH less than the pH of the first acrylate phase, where the monomer solution has a degree of neutralization from 0.5 to 0.9, preferably from 0.6 to 0.85, and more preferably from 0.65 to 0.8;

where the content of acrylate and acrylic acid in the aqueous solution of the monomer is from 30 to 50 wt.%, preferably from 35 to 45 wt.%, each value relative to the total mass of the aqueous solution of monomer.

In this regard, the successive stages of the process according to the present invention can be carried out simultaneously or can overlap in time, or both can take place. This applies in particular to stages (i) - (iv), especially to stages (iii) and (iv). The degree of neutralization in this context is the ratio of the number of moles of hydroxide to the number of moles of acrylic acid.

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. Preferably, the polymerization reactor is a ribbon polymerization reactor. Preferably, an aqueous solution of the monomer is added continuously, therefore, and continuously fed to the ribbon of a polymerization ribbon reactor. The resulting polymer gel is continuously discharged from the polymerization reactor and optionally continuously crushed, dried, crushed and

- 4 031397 sorted at subsequent process stages. 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 test method EDANA and INDA) in the range 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 preferred that the content of particles of water-absorbing polymers having a particle size in the range 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 % relative to the 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 (α1) and at least one crosslinking agent (α3).

Preferred monoethylenically unsaturated monomers having carboxylic acid groups (α1) are the monomers mentioned in DE 10223060 A1 as the preferred monomers (α1), thus, particularly preferred is acrylic acid. Preferred monoethylenically unsaturated monomers containing carboxylic acid groups (α1) are acrylic acid, methacrylic acid, ethacrylic acid, α-chloro-acrylic acid, α-cyanoacrylic acid, β-methacrylic acid (crotonic acid), α-phenylacrylic acid, β-methacrylic acid (crotonic acid), and a flow chart. sorbic acid, α-chlorosorbic acid, 2'-methylisocrotonic acid, cinnamic acid, p-chlorocinnamic acid, β-stearic acid, itaconic acid, citraconic acid, mesaconic acid, glutacon Ovic acid, aconitic acid, maleic acid, fumaric acid, tri-carboxyethylene and maleic anhydride, where acrylic acid and methacrylic acid are preferred, and acrylic acid is particularly preferred.

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 further preferably at least up to 90 wt.% Relative to the dry weight of the polymer. 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 wt.%, Preferably at least 70 wt.% Acrylic acid, which is preferably neutralized to at least 20 mol.%, Especially preferably at least up to 50 mol.%. The concentration of partially neutralized, monoethylenically unsaturated monomers having carboxylic acid groups (α1) in an aqueous solution of monomer, 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.% from the total mass of the aqueous solution of the monomer.

Neutralization of monomers containing carboxylic acid groups is preferably carried out by adding sodium hydroxide to at least a portion of the aqueous monomer solution at the beginning of stage (i) in step (i2). Acrylic acid optionally contains a polymerization inhibitor. The polymerization inhibitor is preferably selected from the group consisting of hydroquinone monomethyl ether (MEHQ) or hydroquinone (HQ), or both.

Acrylic acid preferably contains a polymerization inhibitor, for example, hydroquinone monomethyl ester (MEHQ) or hydroquinone (HQ) preferably in an amount of from 100 to 2000 ppm or preferably in an amount of from 120 to 1000 ppm, or preferably in an amount of from 150 to 500 ppm by weight the first part of acrylic acid. Preferably, acrylic acid contains hydroquinone monomethyl ester (MEHQ).

In step (i2) of the process of the present invention, the first part of the acrylic acid is brought into contact with the hydroxide to obtain a pH of 10 or more, preferably more than 10.5 or more preferably more than 10.8. In some cases, a maximum pH of 12 is reached. The first part of acrylic acid preferably contains hydroxide in a weight ratio to acrylic acid from 0.1: 1 to 1.5: 1, or preferably from 0.2: 1 to 1.3: 1, or preferably from 0.3: 1 to 1: 1. The addition of hydroxide to acrylic acid leads to the conversion of at least part of acrylic acid to acrylate. According to the present invention, in the first acrylate phase, at least 95 mol% of acrylic acid is an acrylate.

The first acrylate phase is brought into contact in step (i3) with an additional part of acrylic acid to form a monomer solution. Bringing into contact at stage (i3) can be carried out by any method chosen by the person skilled in the art to bring the two waters into contact.

- 5 031397 phases. An additional part of acrylic acid has a lower water content than the first acrylate phase. The water content in the additional part of the water is less than the water content in the first part of acrylic acid. The first part of acrylic acid preferably has a water content of from 30 to 80 wt.%, Or from 35 to 75 wt.%, Or from 40 to 70 wt.%, Each value relative to the total mass of the first part of acrylic acid. The additional part of the acrylic acid preferably has a water content of from 0 to 10% by weight, or preferably from 0 to 8% by weight, or preferably from 0 to 6% by weight, each value relative to the total weight of the additional part of acrylic acid.

The monomer solution obtained in step (i3) of the method according to the present invention has a pH less than the pH of the first acrylate phase. Preferably, the pH of the monomer solution differs from the pH of the first acrylate phase by a value from 0.5 to 6 units. pH, or preferably from 1 to 5 units. pH, or preferably from 1.5 to 4.5 units. pH. According to the present invention, it is preferable that 60-80 mol.%, Preferably 65-78 mol.% Or preferably 67-76 mol.% Of acrylic acid in solution. The monomer is an acrylate.

At stage (i) obtaining an aqueous solution of the monomer preferably includes several additional stages:

α) providing the first part of acrylic acid containing acrylate and optionally MEHQ or HQ, and / or;

β) providing acrylic acid monomer and / or;

χ) providing additional monoethylenically unsaturated monomers (α2);

Stage β-χ can be carried out in any order and in any combination with stage α. In one preferred embodiment, the implementation is carried out only stage α. In an additional preferred embodiment, the implementation of stage α and β. In an additional preferred embodiment, the implementation stage α and χ. In stage (i), the order can also be changed. In a preferred embodiment, the implementation first provide a crosslinking agent (α3), and then can be carried out stage α and optionally one of the stages β and / or χ. In an additional preferred embodiment, the implementation is first carried out only stage α or in combination with one of the stages β or χ, and then add a crosslinking agent (α3).

The content of acrylate and acrylic acid in the aqueous solution of the monomer is less than 55% by weight, preferably less than 50% by weight or preferably less than 45% by weight, of the total weight of the aqueous solution of monomer. It is further preferred that the content of acrylate and acrylic acid in the aqueous monomer solution is at least 30% by weight.

The aqueous monomer solution may also contain monoethylenically unsaturated monomers (α2), which can be copolymerized with (α1). Preferred monomers (α2) are the monomers indicated in DE 10223060 A1 as preferred monomers (α2), thus acrylamide is particularly preferred.

Preferred crosslinking agents (α3) according to the present invention are compounds that have at least two ethylenically unsaturated groups in one molecule (a crosslinking agent of class I), compounds that have at least two functional groups that can interact with the functional groups of monomers ( α1) or (α2) in the condensation reaction (= crosslinking agents of condensation), in the addition reaction or in the ring opening reaction (crosslinking agent of class II), compounds that have at least one floor and an unsaturated group and at least one functional group that can interact with the functional groups of the monomers (α1) or (α2) 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 class-I crosslinking agents, polymer crosslinking is achieved by radical polymerization of ethylenically unsaturated groups of crosslinking agent molecules with monoethylenically unsaturated monomers (α1) or (α2), and with class II crosslinking agents and polyvalent metal cations of the crosslinking agent IV polymer crosslinking , respectively, by the condensation reaction of functional groups (class II crosslinking agent) or by electrostatic interaction of a polyvalent metal cation (crosslinking agent Class IV) with the functional groups of the monomer (α1) and (α2). With compounds of the class of cross-linking agents III, cross-linking of polymers is achieved, respectively, by radical polymerization of ethylenically unsaturated groups, as well as by condensation between functional groups of cross-linking agents and functional groups of monomers (α1) or (α2).

Preferred crosslinking agents (α3) are all those compounds which are indicated in DE 10223060 A1 as crosslinking agents (α3) of crosslinkers classes I, II, III and IV, thus, N.N 'are particularly preferred as compounds of crosslinking agents I. -metilenbisakrilamid, di (meth) acrylates of polyethylene glycol triallilmetilammoniya chloride, tetra allyl ammonium chloride and acrylate allilnonaetilenglikolya obtained from 9 moles of ethylene oxide per mole of acrylic acid, wherein more preferably Ν, Ν'-methylenebisacrylamide, and

- 6 031397 Al ₂ (SO 4) 3 and its hydrates are particularly preferred as compounds of the class of crosslinking agents IV.

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, I II, 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 10223060 A1 as a crosslinking agent of crosslinking agents class I, thus, are particularly preferred as crosslinking agents of the class of crosslinking agents IN, N ' methylene bisacrylamide, polyethylene glycol di (meth) acrylates, triallylmethylammonium chloride, tetraallyl ammonium chloride and allyl non-ethylene glycol acrylate, prepared from 9 mol of ethylene oxide per m l of acrylic acid, wherein more preferably Ν, Ν'-methylenebisacrylamide.

The aqueous monomer solution may additionally contain water-soluble polymers (α4). Preferred water-soluble polymers (α4) 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 (α4) are starch or starch derivatives, or polyvinyl alcohol. Water-soluble polymers (α4), 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 (α5), and these auxiliary substances include, in particular, complexing agents, such as, for example, EDTA.

The relative amount of monomers (α1) and (α2), and crosslinking agents (α3), and water-soluble polymers (α4), and excipients (α5) in an aqueous monomer solution is preferably chosen so that the structure of the water-absorbing polymer obtained after drying the optionally crushed polymer the gel is based on 20-99.999 wt.%, preferably 55-98.99 wt.% and particularly preferably 70-98.79 wt.% on monomers (α1), on 0-80 wt.%, preferably on 0- 44.99 wt.% And particularly preferably 0.1-44.89 wt.% On monomers (α2), 0-5 wt.%, Preferably 0 , 001-3 wt.% And particularly preferably 0.01-2.5 wt.% On cross-linking agents (α3), 0-30 wt.%, Preferably 0-5 wt.% And particularly preferably 0, 1-5 wt.% On water-soluble polymers (α4), 0-20 wt.%, Preferably 0-10 wt.% And particularly preferably 0.1-8 wt.% On auxiliary substances (α5), and 0.5-25 wt.%, Preferably 1-10 wt.% And particularly preferably 3-7 wt.% On water (α6), the sum of the quantities by weight (α1) - (α6) is 100 wt.%.

The optimal concentration values, in particular, monomers, cross-linking agents and water-soluble polymers in the monomer solution can be determined by simple preliminary experiments or based on the known prior art, in particular, from publications US 4286082, DE 2706135 A1, US 4076663, DE 3503458 A1, DE 40 20 780 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), fine particles of the water-absorbing polymer can 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 combinations of at least two of them.

Water-absorbing fine particles are preferably particles of a water-absorbing polymer, the composition of which 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 preferably at least 99% by weight of water-absorbing fine particles of the total mass of water-absorbing fine particles have a particle size of less than 200 microns, preferably less than 150 microns and especially preferably less than 100 microns.

In a preferred embodiment of the method according to the present invention, the water-absorbing fine particles, which may optionally be added to the aqueous solution of monomer at the technological stage (ii), are water-absorbing small particles, which at the technological stage (x) of the method according to the present invention and which, thus, 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 preferred that the first stream of fine particles and the second stream of monomer aqueous solution form an angle of 5 in the range from 60 to 120 °, more preferably in the range from 75 to 105 °, even more preferably in the range from 85 to 95 ° and most preferably form an angle of about 90 °. It is also preferable that the flow of the mixture of fine particles and the aqueous monomer solution leaving the mixer, and the first stream of fine particles entering the mixer, form an angle s in the range from 60 to 120 °, preferably in the range from 75 to 105 °, more preferably in range 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. Specific examples of mixing devices that can be used to add fine particles to an aqueous solution of monomer at the technological stage (ii) according to the present invention are mixing devices that can be purchased from IKA® 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 the polymerization initiator system, which contains two or more components, is added to the 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 the peroxide tert-butyl per-2-ethylhexenoate, tert-butylperisone, tert-butyl permaleate, tert-butylperbenzoate, tert-butyl-3,5,5-trimethylhex anoata and amilperneodekanoata. Further preferred are the following thermal polymerization initiators are: azo compounds such as azo-bis- isobutyronitrile 8 031397, azobis-dimethylvaleronitrile, azobis-amidinopropane dihydrochloride, 2,2'-azobis (N, N-dimethylene) izobutiramidina dihydrochloride 2- (carbamoylazo) isobutyronitrile and 4,4'-azobis- (4 cyanoaleric acid). The above compounds are used in conventional amounts, preferably in the range 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 (II) ions or silver ions, or sodium hydroxymethyl sulphoxylate. Preferably, ascorbic acid or sodium pyrosulfite is used as the reducing component of the redox catalyst. From 1 x 10 ^-5 to 1 mol.% Of the reducing component of the redox catalyst and from 1 x 10 ^-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 α-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, I-dimethylamino) ethyl 4-azidocinnamate, 2- (I, I-dimethylamino) ethyl 4-azidonaphthylketone, 2- (I, I-dimethylamino) ethyl 4-azidobenzoate, 5-azido-1-naphthyl-2 '- (I, I-dimethylamino) ethylsulfone, n-c (4-sulfonyl azidophenyl) maleimide, No-acetyl-4-sulphonyl azidoaniline, 4-sulfonyl-azidoaniline, 4-azidoaniline, 4-azidophenylace, 4-sulfonyl azidoaniline, 4-azidoaniline, 4-azidophenyl, 4-sulfonyl azidoaniline , 6-bis- (p-azidobenzylidene) cyclohexanone and 2,6-bis- (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 the specified initiator contains peroxodisulfate and a molecule of organic initiator in a molar ratio of from 20: 1 to 50: 1.

In one aspect of this embodiment, it is preferable 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-azobis- (2-amidinopropane) dichloride, 2,2 -azobis- (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, Ka, 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, as in the case of a preferred initiator system that contains hydrogen peroxide, sodium peroxodisulfate and ascorbic acid, and which is active only when all components are added, one or more components of such a polymerization initiator system can for example, be added to the technological stage (iv), while the rest of the component or the rest of the components needed to supplement the system activity initiator The polymerization is added after process step (iv), possibly even after process step (v).

At the technological stage (iv) of the method according to the present invention in an aqueous solution of

- 9 031397 numbers do not necessarily reduce the oxygen content. The optional step (iv), the reduction of the oxygen content in the aqueous monomer solution, can be carried out before, during or after the technological step (ii). Preferably, the content of oxygen in the aqueous solution of the monomer is reduced after the addition of small particles at the technological stage (ii).

Reducing the oxygen content of the aqueous monomer solution can be accomplished by bringing the aqueous monomer solution into contact 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 wt. ppm, more preferably to less than 0.5 wt. ppm relative to the total amount of 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 polymerization belt as a polymerization reactor, in the rear part of the conveyor belt, a strand of polymer gel is obtained, which is preferably crushed before drying to form gel particles.

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 obtained by polymerizing an aqueous monomer solution is continuously crushed, for example, using agitator shafts rotating in opposite directions, as described in WO 2001/38402.

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. Examples of conveyor belts that can be used in the method according to the present invention are described in DE-A3544770, EP-A-0955086 and EP-A-1683813.

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 for unwinding and supplying a release sheet is presented, which 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 maximum possible product yield in a single pass per unit of time, in accordance with the present invention, upward supporting elements, longitudinal axes, are located on both sides of the horizontal support elements, starting in the delivery zone and dosing systems. which intersect 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 cross-sectional shape of the supporting elements can be variable to align the initially deep chute as it moves toward 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,

- 10 031397 can easily achieve the desired shape of the cross section of the gutter. 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. In process step (vi), the monomers in the aqueous monomer solution are preferably polymerized on a belt to form a polymer gel. Preferably, the polymer gel is obtained on the back along the tape. Before drying, the polymer gel is preferably crushed to obtain particles of a polymer gel.

In a preferred embodiment of the present invention, the monomer solution is subjected to radical polymerization to form a precursor polymer. Radical polymerization can be initiated by any method chosen by a person skilled in the art. Preferably, the initiator is selected from the group consisting of heat, irradiation, or a combination thereof. Radiation initiation is preferred. The investment is preferably provided by UV radiation. Preferably, the precursor polymer is subjected to an additional crosslinking step. An additional crosslinking step can be carried out using any step chosen by a person skilled in the art for the crosslinking process. The optional crosslinking step may include the following steps:

a1) adding monomers to the precursor polymer;

A2) adding a crosslinking agent (α3) to the precursor polymer;

a3) adding an initiator to the precursor polymer;

A4) initiation of polymerization.

Stages a1-a4 can be carried out individually or in any combination with each other and in any sequence.

At the technological stage (vii) of the method according to the present invention, the particulate polymer gel obtained in the polymerization reactor, preferably the polymer gel particles obtained in the kneading reactor, or strands of the polymer gel obtained in the rear part of the conveyor belt, is unloaded from the reactor and, especially in the case of a polymer gel strand obtained on a conveyor belt, it is (additionally) crushed to obtain polymer gel particles. Preferably, the obtained polymer gel strand is unloaded from the conveyor belt in the form of a continuous strand, which has a soft, semi-solid consistency, and then is sent for additional processing, such as crushing.

The crushing of the polymer gel or gel strand 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 a 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 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 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 wide from 1 to 100 mm, preferably from 3 to 20 mm, and in the third stage a (crushing) installation of a top is used, preferably of the cutter type, preferably having a screw and a plate with holes, where the screw pushes the product through the plate with holes, for grinding and grinding chkov gel particles in the polymer gel, which gel preferably smaller 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. During this stage of (viii) drying, water is preferably removed from the polymer gel at a rate of from 120 to 240 kg / min, preferably from 130 to 230 kg / min, or preferably from 140 to 220 kg / min, or preferably from 150 to 210 kg / min, or preferably from 160 to 200 kg / min relative to a batch of polymer gel weighing from 0.5 to 5 tons, or preferably from 0.8 to 4.5 tons, or preferably from 1 to 4 tons. It is preferable to reduce the water content from 40 -60 wt.% Of the total mass of the polymer gel to 3-7 wt.% Of the total mass of the dried polymer reach over a period of time and from 1 to 60 minutes or preferably from 2 to 50 minutes, or preferably from 3 to 40 minutes. The dry polymer obtained preferably has a water content of from 3 to 7 wt.% Or preferably from 3.5 to 6.5 wt.%, Or preferably from 4 to 6 wt.% Of the total weight of the dried polymer. The water content is measured by the Karl-Fisher titration method.

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 to dry the polymer gel or

- 11 031397 gel particles described above. As an example, rotary tube furnaces, fluidized bed dryers, disc dryers, rotary paddle dryers and infrared dryers can be mentioned.

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 a continuous conveyor belt, which passes the gas, and is treated with a stream of heated gas, preferably air. The drying gas is preferably recycled 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 polymer gel to be dried is 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. The thickness of the polymer the gel 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 m 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 is ground to form water-absorbing polymer particles.

For grinding the dried polymer gel, any device can be used that is considered suitable by those skilled in the art for grinding the dried polymer gel or the above-described dried polymer gel. As an example of a suitable grinding device, a single or multi-stage roller mill can be mentioned, preferably a two- or three-stage roller mill, a pin mill, a hammer mill, or a vibratory mill.

At the technological stage (x) of the method according to the present invention, the 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 the water-absorbing polymer, the content of polymer particles having a particle size of less than 150 microns is less than 10% by weight, preferably less than 8% by weight and, in particular, less than 6% by weight, and that the content is polymer particles having a particle size of more than 850 μm are also less than 10% by weight, preferably less than 8% by weight and particularly preferably less than 6% by weight, each value is expressed relative to the total weight of the particles of the water-absorbing polymer. 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 of the water-absorbing polymer have a particle size of from 300 to 600 μm.

At the technological stage (xi) of the method according to the present invention, the surface of the crushed and sorted particles of 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, processing

- 12 031397 surfaces with water-soluble salts, such as aluminum sulphate or aluminum lactate, surface treatment with inorganic particles, such as silicon dioxide, etc. 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. Additionally, preferably, the treatment of water-absorbing polymer particles or surface-crosslinked water-absorbing polymer particles is mixing the particles in one, two or more fractions with zeolites. Zeolites preferably contain one of the elements selected from the group consisting of Ag, Na, Zn, or a mixture of at least two of them. Preferably, the zeolites are mixed with water-absorbing polymer particles in an amount of from 0.05 to 5 wt.% Or preferably from 0.1 to 13 wt.%, Or preferably from 0.2 to 10 wt.% Of the total mass of water-absorbing polymer particles. Through this treatment, an additional treated water-absorbing polymer particles are obtained.

In a preferred embodiment of the present invention, the degree of neutralization of the acrylate phase in step (i2) is more than 1, preferably more than 1.05, more preferably more than 1.1, most preferably more than 1.15. Preferably, the degree of neutralization of the acrylate phase in step (i2) is no more than 1.2.

In a preferred embodiment of the present invention, the temperature of the first part of acrylic acid and the temperature of the hydroxide differ by 2 K or more, preferably by 5 K or more, more preferably by 10 K or more, more preferably by 15 K or more, more preferably by 20 K or more, most preferably 25 K or more. Preferably, the hydroxide has a temperature of from 0 to 20 ° C, more preferably from 0 to 15 ° C, more preferably from 0 to 10 ° C, most preferably from 0 to 5 ° C.

In a preferred embodiment of the present invention, the additional part of acrylic acid contains less than 5% by weight of water, preferably less than 3% by weight of water, more preferably less than 2% by weight of water, based on the total weight of the additional part of acrylic acid.

In a preferred embodiment of the present invention, the first part of acrylic acid contains 50% by weight or more of water, preferably 60% by weight or more of water, more preferably from 60 to 70% by weight of water, more preferably from 62 to 68% by weight, more preferably from 62 to 66% by weight of water, most preferably from 63 to 64% by weight of water, based on the total weight of the first part of acrylic acid.

In a preferred embodiment of the present invention, the pH of the monomer solution is from 8 to 12, preferably from 8 to 11, more preferably from 8 to 10, most preferably from 8 to 9.

In a preferred embodiment of the present invention, the hydroxide is selected from the group consisting of sodium hydroxide, potassium hydroxide and lithium hydroxide, or a mixture of at least two of them.

In a preferred embodiment of the present invention, the oxygen gas content in the monomer solution is from 3 to 15 wt. ppm, preferably from 5 to 12 wt. ppm, more preferably from 6 to 10 wt. ppm by weight of the monomer solution. Preferably the monomer solution is saturated with gaseous oxygen.

In a preferred embodiment of the present invention, the monomer solution is brought into contact with active carbon in an additional step of bringing into contact. Preferably, the additional contacting step is carried out to step (i2). Preferably, the additional contacting step is carried out for from 60 to 240 minutes, preferably from 80 to 220 minutes, more preferably from 100 to 200 minutes, most preferably from 120 to 180 minutes. Preferably the amount of active carbon used in the additional stage of bringing into contact is from 0.05 to 10 wt.%, Preferably from 0.1 to 5 wt.%, More preferably from 0.2 to 1 wt.% Of the total mass of the solution monomer. Preferably the active carbon is a granule containing powder. Preferably, the diameter of the granules is less than 1.0 mm, preferably less than 0.7 mm, more preferably less than 0.5 mm.

In a preferred embodiment of the present invention, at least the first stage of bringing into contact or the second stage of bringing into contact, or both stages complete within a period of time from 10 to 300 minutes, preferably from 20 to 250 minutes, more preferably from 30 to 200 minutes .

In a preferred embodiment of the present invention, at least the first stage of bringing into contact or the second stage of bringing into contact, or both stages, preferably both stages are carried out in aggregate at a temperature of an aqueous solution of monomer less than 40 ° C, preferably less than 30 ° C, more preferably less than 25 ° C.

In a preferred embodiment of the present invention, in step (v), the polymerization reactor is a ribbon polymerization reactor. Preferred ribbon reactor

- 13 031397 polymerization contains a conveyor belt, preferably an endless conveyor belt.

In a preferred 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 a preferred embodiment 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 in the range 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 a preferred embodiment 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 in the range 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. The 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 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 foaming agent is added to the monomer solution immediately after or simultaneously with the addition of an initiator or a component of the initiator system. Preferably, the foaming agent is added to the monomer solution in an amount of from 500 to 4000 wt. ppm, preferably from 1000 to 3500 wt. ppm, more preferably from 1500 to 3200 wt. ppm, most preferably from 2000 to 3000 wt. ppm of the total mass of the monomer solution.

A blowing agent is a substance capable of forming cells 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 an agent 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 in combination 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 Pat. No. 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 CO2 as a gas, CO2 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 natural carbonate is dolomite. The above carbonate foaming agents, dissolved or dispersed in the monomer solution, release CO2 when heated. A particularly preferred carbonate blowing agent is MgCO ₃ , which can also be represented by the formula ^ gCOsE-Mg ^^^ n ^. Another preferred carbonate foaming agent is (NH ₄ ) ₂ CO ₃ . MgCO ₃ and (NH ₄ ) ₂ CO ₃ can also be used in mixtures. Preferred carbonate foaming agents are carbonate salts of polyvalent cations such as Mg, Ca, Zn, and the like. Examples of such carbonate foaming agents are Na ₂ CO ₃ , K ₂ CO ₃ , (NH ₄ ) ₂ CO ₃ , MgCO ₃ , CaCO ₃ , NaHCO ₃ , KHCO ₃ , NH ₄ HCO ₃ , Mg (HCO ₃ ) ₂ , Ca (HCO ₃ ) ₂ , ZnCO ₃ and BaCO ₃ . 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. The preferred aromatic azo compound is

- 14 031397 a compound selected from the group consisting of triazene, arylazosulfones, arylazotriarylmethanes, hydrazo compounds, a 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-K ^ -dinitrosoterephthalamide.

The contribution to the solution of at least one of the above tasks is made by means of a device for producing water-absorbing polymer particles in a process stream, comprising:

a) a first container configured to accommodate acrylic acid;

b) a second container configured to accommodate a metal hydroxide;

c) a cooling device where the cooling device

i) located after the second container, ii) configured to cool the metal hydroxide;

d) the first mixing device, where the first mixing device:

i) located after the first container and the cooling device, ii) is equipped with a cooler and mixing tools set in motion;

e) the third container, where the third container:

i) located after the first mixing device; ii) configured to receive an aqueous monomer solution containing at least one partially neutralized, monoethylenically unsaturated monomer containing carboxylic acid groups (α1);

f) a fourth container configured to receive at least one crosslinking agent (α3);

g) a second mixing device, where the second mixing device:

i) located after the third container and the fourth container, ii) made with the possibility of mixing the monomer solution and at least one crosslinking agent (α3);

h) a ribbon polymerization reactor, where the ribbon polymerization reactor:

i) is located after the second mixing device, ii) configured to accommodate the aqueous monomer solution and at least one crosslinking agent (α3) during the polymerization of the monomers in the aqueous monomer solution, to form a polymer gel;

j) crushing device, where crushing device:

i) located after the ribbon polymerization reactor, ii) made with the possibility of crushing the polymer gel;

k) belt dryer, where belt dryer:

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

l) grinding device, where the grinding device:

i) located after the belt dryer, ii) made with the possibility of grinding the dried polymer gel with getting water-absorbing polymer particles;

m) sorting device, where sorting device:

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

Preferred components or devices, or both, of said equipment for producing particles of a water-absorbing polymer according to the present invention, are made in accordance with the method according to the present invention.

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.

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.

In a preferred embodiment of the present invention, the composite material according to the present invention contains 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 and fungal growth control agents, a packaging

- 15 031397 material, additives for soil, building material or a combination of at least two of them. The preferred cable is a blue submarine cable. A preferred dehumidifying sanitary 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 the active compound, or in a building material.

Polymerization Tape Reactor

The preferred ribbon of a polymerization belt 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 polymer gel .

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 for the method according to the present invention is usually used multilayer material. Mechanical requirements can be met with a frame, for example, woven inserts made from natural and / or synthetic fibers, or glass fibers, or steel cords. 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.

The polymerization belt reactor is located near the guide roller for the return leg of the conveyor belt.

In order to ensure complete polymerization with the maximum possible product yield in a single pass per unit of time, in accordance with the present invention, upward supporting elements can be arranged on both sides of the horizontal support elements, starting in the delivery zone and dosing systems, whose longitudinal axes intersect at a point under the upper branch, and which give the conveyor belt, supported by them, the shape of a suitable groove.

Another means of providing a configuration in the form of a gutter is to place overflow elements on an approximately flat tape. In this method, at least one overflow element is placed in the longitudinal direction at each side edge of the tape. At least two additional overflow elements are arranged in the transverse direction in other longitudinal positions of the tape, with the groove extending longitudinally between said two positions. The height of the overflow elements determines the depth of the chute and, therefore, the number of reaction components that can be loaded into the chute. Longitudinal overflow elements should be designed with the possibility of buckling along with the tape in the rotary sections of the tape. For this, the longitudinal overflow elements may be made of a flexible material, or they may consist of a plurality of shorter longitudinal overflow elements located close to each other.

The configuration of the gutter-shaped polymerization tape can also be achieved by combining transversely oriented overflow elements and ensuring the shape of the tape in the transverse direction using support elements, or a combination of longitudinally oriented overflow elements and ensuring the shape of the tape in the longitudinal direction using support elements.

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 earliest

- 16 031397 filing date of this application. In the absence of an ISO test method, the EDANA test method was used closest to the earlier filing date of the present application. In the absence of specific measurement conditions, ambient temperature and pressure (SATP) were used, that is, a temperature of 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 was determined by the Karl-Fisher method.

The residual monomer content

The residual monomer content was measured in accordance with the standard test method for superabsorbent materials determined by EDANA. This test method is described in EDANA, Harmonized Test Methods Nonwovens and Related Industries, 2012 edition, in the Residual Monomers section with the method number WSP 210.2.R3 (12).

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) Obtaining a solution of monomer 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 sodium acrylate monomer solution was obtained with a neutralization degree of 0.7. To obtain the specified monomer solution, an aqueous solution of acrylic acid was provided with a water content of 63% by weight and a temperature of 25 ° C. An aqueous solution of NaOH containing 30% by weight of NaOH was cooled to the temperature indicated in the table and added to the aqueous solution of acrylic acid in the mixer to obtain the degree of neutralization indicated in the table, maintaining the temperature during the neutralization within 35 ° C. Five minutes after neutralization, ice-cold acrylic acid was added to achieve a degree of neutralization of 0.7, maintaining the temperature during the neutralization within 35 ° C.

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.

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 treated water-absorbing product. Details of the additional processing are presented below.

The mixed solution was then placed on a conveyor belt belt as shown in FIG. 4, and initiated polymerization by UV radiation. The length of the conveyor belt was at least 20 m. The conveyor belt was shaped like a groove 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 of about 52% by weight of the total weight of the polymer gel.

C) Crushing and drying the polymer gel

The polymer gel formed a strand of polymer gel, which was unloaded from the conveyor belt and crushed in three stages:

rubbery polyacrylic acid gel was cut into flat gel strips 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 a crusher was used 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 dried polymer gel

- 17 031397 was passed through a Herbold HGM 60/145 granulator (HERBOLD Meckesheim GmbH) and the obtained dried polymer gel particles, which had a size less than 7 mm, were placed for 2.5 hours in a container to balance the moisture content of the polymer gel particles. The particles of the dried polymer gel were then ground in a roller mill of the type Bauermeister, 350.1 x 1800 (3-stage crusher) (Bauermeister Zerkleinerungstechnik GmbH) to obtain water-absorbing polymer particles having a particle size of less than 1 mm.

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 in the range 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 Sipernat® 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 crosslinking agent relative to the total mass of the mixture of precursor II and crosslinking 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 (Gebruder 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 in the range from 300 to 600 μm. 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. Received additionally treated surface-crosslinked particles of a water-absorbing polymer.

The content of residual monomer, depending on the degree of neutralization and temperature of NaOH

Example Degree of neutralization Temperature NaQH _R0 4H Content residual monomer Comparative Example 1 0.7 25 ° С Comparative Example 2 0.7 5 ° С Comparative Example 2 0.8 5 ° С Example 1 0.97 25 ° С + Example 2 1.01 25 ° С ++ Example 3 1.01 5 ° С +++ Example 4 1.1 5 ° С +++

The following scale was used to compare the measurement results of the parameters presented in the table for examples and comparative examples. In the order shown below, the measurement results are improved from left to right: ---, -, -, +, ++, +++.

- 18 031397

From the table above it is obvious that the content of residual monomer in surface-crosslinked water-absorbing polymer particles can be significantly reduced by excessive neutralization with an aqueous solution of NaOH having a low temperature.

FIG. 1 is a flow chart illustrating steps (101-111) provided after steps 112 and 114, process 100 for preparing water-absorbing polymer particles according to the present invention. The first stage (i1) 112 includes: providing the first part of acrylic acid containing hydroquinone monomethyl ester (MEHQ) or hydroquinone (HQ), or both. Additional stage (i2) 113 includes: bringing into contact the first part of acrylic acid with sodium hydroxide (NaOH) in the first stage of bringing into contact, where a pH of 10 or more is reached to obtain the first aqueous phase containing sodium acrylate. Preferably, the first aqueous phase containing sodium acrylate has a degree of neutralization of 1 or more. In step (i3) 114, the first acrylate phase is brought into contact with an additional part of acrylic acid in the second step of bringing into contact to form a monomer solution. In step (i), a 101 monomer aqueous solution contains at least one partially neutralized, monoethylenically unsaturated monomer containing carboxylic acid groups (α1). The monomer solution is obtained in step (i1) 112, step (i2) 114, step (i3) 116. Preferably, the aqueous monomer solution is an aqueous solution of partially neutralized acrylic acid, which additionally contains crosslinking agents. Preferably, the partially neutralized acrylic acid is provided as a solution in the form of a first part of acrylic acid containing MEHQ neutralized with sodium hydroxide NaOH prior to the first acrylate phase. After neutralization in the first acrylate phase, about 96 mol.% Acrylic acid is an acrylate. The aqueous monomer solution may also contain additional monomer such as acrylic acid or acrylamide. The monomer solution and at least one crosslinking agent (α3) are provided in step (i) 101.

In the second stage 102, fine particles of a water-absorbing polymer may be added to the aqueous monomer solution. Preferably, said particles comprise polyacrylic acid particles. In the third step 103, a polymerization initiator or at least one component of the polymerization initiator system, which contains two or more components, is added to the aqueous monomer solution. In the fourth stage 104, the oxygen content in the monomer aqueous solution is reduced by passing nitrogen through the monomer aqueous solution. In the fifth stage 105, the monomer solution is loaded onto a ribbon 401 of a polymerization ribbon reactor 400. The belt 401 is a continuous 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 401. Then the polymer gel is crushed to obtain particles of the 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 of the polymer gel are discharged from the belt dryer, and then crushed in the ninth stage 109 to form water-absorbing polymer particles. At the tenth stage 110, water-absorbing polymer particles are sorted by size to form water-absorbing polymer particles having a well-defined particle size distribution. At the eleventh stage 111, the surface of the water-absorbing polymer particles is subjected to surface crosslinking.

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 and 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 is a schematic diagram of basic settings for a polymerization belt reactor 400 according to the present invention. The polymerization belt reactor 400 comprises a belt 401. The belt 401 is an endless conveyor belt. The belt 401 runs around two guide rollers 402, so that the upper branch of the belt 401 moves in a downward direction. The downward movement of the upper branch of the belt 401 determines the direction of movement 403 of the polymer gel (not shown) on the belt 401, indicated by the arrow. Another arrow indicates the direction 404, opposite to the direction of movement of the polymer gel on the tape. The other arrow indicates both longitudinal directions 405 of the tape 401, and another arrow indicates the transverse directions 406 of the tape. The ribbon polymerization reactor 400 may contain additional components that are not shown in the figure, such as support elements, a feed and dispense system, irradiating devices, cooling and heating devices, as well as a discharge system.

FIG. 5 is a block diagram of an apparatus 500 for preparing water-absorbent polymers.

- 19 031397 particles according to the present invention. The arrows indicate the direction of the process stream 512 for producing water-absorbing polymer particles. The device 500 comprises a first container 501, a second container 502, a cooling device 503 following the second container 502, a cooling device 503 following the cooling device 50 and a first mixing device 504 504 following the first mixing device 504, the third container 505, the fourth container 506, following the third container 505 and the fourth container 506 second mixing device 507, the next polymerization belt reactor 400, the next crushing device 508, the next belt dryer 509, the next grinding A device 510 and a subsequent screening device 511, each of which is in accordance with the present invention.

Claims (1)

CLAIM 1. A method of obtaining a water-absorbing polymer particles, including technological stages: (i) obtaining an aqueous solution of a monomer containing at least one partially neutralized, monoethylenically unsaturated monomer containing carboxyl groups (α1) and at least one crosslinking agent (α3); (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 (400); (iv) polymerizing monomers in an aqueous solution of monomer in a polymerization reactor (400) to form a polymer gel; (v) discharging the polymer gel from the polymerization reactor (400); (vi) drying the polymer gel; (vii) grinding the dried polymer gel to form water-absorbing polymer particles; and (viii) sorting by size of ground water-absorbing polymer particles; where at the technological stage (i) obtaining an aqueous solution of the monomer further includes the steps: (11) providing the first part of acrylic acid and (12) bringing the first part of acrylic acid into contact with the hydroxide in the first contacting stage to obtain the first acrylate phase, where the first acrylate phase has a pH of 10 or more, where the first acrylate phase has a degree of neutralization of at least least 0.95; and (13) bringing the first acrylate phase into contact with an additional part of acrylic acid in the second contacting stage to obtain a monomer solution, where the additional part of acrylic acid has a water content less than the water content in the first acrylate phase, where the monomer solution has a pH less than the pH of the first acrylate phase, where the monomer solution has a degree of neutralization of from 0.5 to 0.9; where the content of acrylate and acrylic acid in an aqueous solution of the monomer is from 30 to 50 wt.% from the total mass of the aqueous solution of monomer. 2. The method according to claim 1, characterized in that the degree of neutralization of the acrylate phase in stage (i2) is more than 1. 3. The method according to claim 1 or 2, characterized in that the temperature of the first part of acrylic acid and the temperature of the hydroxide differ by 2 K or more. 4. The method according to any of the preceding paragraphs, characterized in that the additional part of acrylic acid contains less than 5 wt.% Water relative to the total mass of the additional part of acrylic acid. 5. The method according to any of the preceding paragraphs, characterized in that the first part of acrylic acid contains 50 wt.% Or more of water relative to the total mass of the first part of acrylic acid. 6. The method according to any of the preceding paragraphs, characterized in that the pH of the monomer solution is from 8 to 12. 7. The method according to any of the preceding paragraphs, characterized in that the hydroxide is selected from the group consisting of sodium hydroxide, potassium hydroxide and lithium hydroxide or a mixture of at least two of them. 8. The method according to any of the preceding paragraphs, characterized in that the content of oxygen gas in the monomer solution is from 3 to 15 wt. ppm relative to the mass of the monomer solution. 9. The method according to any of the preceding paragraphs, characterized in that the monomer solution is brought into contact with active carbon at an additional stage of contacting. 10. The method according to any of the preceding paragraphs, characterized in that at least the first stage of contact, or the second stage of contact, or both stages are completed for the period - 20 031397 time from 10 to 300 minutes. 11. The method according to any of the preceding paragraphs, characterized in that at least the first stage of contacting, or the second stage of contacting, or both stages are carried out at a temperature of an aqueous solution of monomer less than 40 ° C. 12. An apparatus for producing water-absorbing polymer particles in a process stream (512), comprising: a) a first container (501) for receiving acrylic acid; b) a second container (502) for receiving a metal hydroxide; c) a cooling device (503), where a cooling device (503): i) located after the second container (502), ii) made with the possibility of cooling the metal hydroxide; d) the first mixing device (504), where the first mixing device (504): i) located after the first container (501) and the cooling device (503), ii) is equipped with a cooler and driven mixing devices; e) the third container (505), where the third container (505): i) is located after the first mixing device (504), ii) is designed to receive an aqueous monomer solution containing at least one partially neutralized, monoethylenically unsaturated monomer containing carboxyl groups (α1); f) a fourth container (506) for receiving at least one crosslinking agent (α3); g) the second mixing device (507), where the second mixing device (507): i) located after the third container (505) and the fourth container (506), ii) is arranged to mix the monomer solution and at least one crosslinking agent (α3); h) a polymerization ribbon reactor (400), where the polymerization ribbon reactor (400): i) is located after the second mixing device (507), ii) is designed to contain the aqueous monomer solution and at least one crosslinking agent (α3) during the polymerization of the monomers in the aqueous monomer solution to form a polymer gel; j) the crushing device (508), where the crushing device (508): i) located after the ribbon polymerization reactor (400), ii) made with the possibility of crushing the polymer gel; k) belt dryer (509), where belt dryer (509): i) is located after the crushing device (508), ii) is made with the possibility of drying the polymer gel; l) grinding device (510), where grinding device (510): i) located after the belt dryer (509), ii) made with the possibility of grinding the dried polymer gel with getting water-absorbing polymer particles; m) sorting device (511), where the sorting device (511): i) located after the crushing device (510), ii) made with the possibility of sorting the crushed particles of water-absorbing polymer. 13. The method of obtaining water-absorbing polymer particles according to any one of claims 1 to 11, using the device according to item 12. 14. Water-absorbing polymer particle obtained by the method according to any one of claims 1 to 11 or 13. 15. Composite material containing water-absorbing polymer particle according to 14. 16. A method of producing a composite material in which the water-absorbing polymer particle of claim 14 and the substrate are brought into contact with each other. 17. Composite material obtained by the method according to clause 16. 18. The use of water-absorbing polymer particles according to claim 14 in the moisture-absorbing hygienic product. 100 114 | <—1 ~ 113 | <- | 112 | 101 | 102 | -> | 103 | -> | 104 | -> | 105 | -> | 106 | | 107 | -> | 108 μ 109 110 | -> | 111 | FIG. one - 21 031397 FIG. 3 FIG. five