KR102223611B1 - Monomer preparation with over-neutralization for production of water-absorbent polymer particles - Google Patents

Abstract

The present invention generally comprises the steps of: (i) preparing an aqueous monomer solution comprising at least one partially neutralized monoethylenically unsaturated monomer having a carboxylic acid group (α1) and at least one crosslinking agent (α3); (ii) optionally, adding absorbent polymer microparticles to the aqueous monomer solution; (iii) adding a polymerization initiator or one or more constituents of a polymerization initiation system including one or more constituents to the aqueous monomer solution; (iv) optionally, lowering the oxygen content of the aqueous monomer solution; (v) filling an aqueous monomer solution into the polymerization reactor; (vi) polymerizing the monomer to obtain a polymer gel; (vii) discharging the polymer gel from the polymerization reactor and optionally crushing the polymer gel; (viii) optionally, drying the crushed polymer gel; (ix) pulverizing the dried polymer gel to obtain absorbent polymer particles; (x) classifying the pulverized absorbent polymer particles; And (xi) optionally, treating the surface of the pulverized and classified absorbent polymer particles, wherein in the production step (i), the preparation of the aqueous monomer solution comprises: i1) providing a first fraction of acrylic acid; i2) contacting the first fraction of acrylic acid with hydroxide in the first contacting step to obtain a first acrylate phase; (i3) It relates to a method for producing absorbent polymer particles, comprising the step of contacting the first acrylate phase with an additional fraction of acrylic acid in the second contacting step to obtain a monomer solution.

Description

Monomer treatment method using over-neutralization for producing absorbent polymer particles {MONOMER PREPARATION WITH OVER-NEUTRALIZATION FOR PRODUCTION OF WATER-ABSORBENT POLYMER PARTICLES}

The present invention relates to a method for producing absorbent polymer particles, absorbent polymer particles obtainable by such a method, composite materials comprising such absorbent polymer particles, methods of preparing such composite materials, composite materials obtainable by such methods, and absorbent polymer particles. It relates to a use, an apparatus for producing absorbent polymer particles, and a method for producing absorbent polymer particles using such apparatus.

Superabsorber, also known as super absorbing polymer (SAP), can absorb a large amount of aqueous fluid, especially body fluid, more specifically urine or blood, through swelling and formation of a hydrogel. It is a water-insoluble crosslinked polymer that can hold these fluids even under the pressure of These polymers, due to their inherent properties, are mainly used in hygiene products, such as, for example, baby diapers, incontinence products or sanitary napkins.

Since the preparation of the super absorbent is generally carried out by free radical polymerization of monomers having an acidic group in the presence of a crosslinking agent, various absorptions depending on the monomer composition, crosslinking agent, and polymerization conditions and the selection of the processing conditions of the hydrogel obtained after polymerization It is possible to prepare polymers with properties (for specifics see, for example, Modern Superabsorbent Polymer Technology, FL Buchholz, GT Graham, Wiley-VCH, 1998).

Polymer gels obtained after polymerization, also referred to as hydrogels, are usually subjected to crushing, drying and sorting processes to obtain a particulate superabsorbent having a defined particle size distribution. In a further process step, these superabsorbent particles are often subjected to surface crosslinking to improve their absorption behavior. To this end, the particles are mixed with an aqueous solution containing a surface crosslinking agent and optionally additional additives, and the mixture is heat treated to promote the crosslinking reaction.

Monomers having an acidic group can be polymerized in the presence of a crosslinking agent in a batch process or a continuous process. In continuous polymerization and batch polymerization, partially neutralized acrylic acid is typically used as the monomer. Suitable neutralization methods are, for example, EP 0 372 706 A2, EP 0 574 260 A1, WO 2003/051415 A1, EP 1 470 905 A1, WO 2007/028751 A1, WO 2007/028746 A1 and WO 2007/028747 A1 It is described in

The continuous polymerization process is generally carried out under special conditions in a polymerization reactor. The polymerization reactor is usually a polymerization belt reactor. A typical polymerization belt reactor includes a conveyor belt designed to convey an aqueous monomer solution containing a monomer having an acidic group during the polymerization process. Such conveyor belts are disclosed in EP 0 955 086 B1.

The main problem with the method for producing absorbent polymer particles is that the residual amount of the monomer is high, especially when used in diapers. Residual monomers remaining in the absorbent polymer particles can cause skin irritation if diapers are frequently used.

In general, an object of the present invention is to solve at least some of the problems of the prior art related to the production of absorbent polymer particles.

An object of the present invention is to provide a method for producing absorbent polymer particles that can be used in diapers with a reduced tendency to induce skin irritation. Another object of the present invention is to provide water absorbent polymer particles with a low residual amount of monomers. In addition, an object of the present invention is to provide an apparatus suitable for producing absorbent polymer particles having a low residual amount of monomers.

Another object of the present invention is to provide water absorbent polymer particles that are produced by a method having one or more of the above-described advantages and are not deteriorated in quality. Another object of the present invention is to provide a composite material containing absorbent polymer particles produced by a method having one or more of the above-described advantages and does not deteriorate in quality. Another object of the present invention is to provide an apparatus for producing absorbent polymer particles through a method having one or more of the advantages described above.

A solution to one or more of the aforementioned tasks is presented as an independent claim. The dependent claims present preferred embodiments of the present invention, and are also presented to solve one or more of the aforementioned problems.

The method for producing water absorbent polymer particles,

(i) at least one partially neutralized, monoethylenically unsaturated monomer bearing carboxylic acid group; And preparing an aqueous monomer solution comprising at least one crosslinking agent (α3);

(ii) optionally, adding absorbent polymer microparticles to the aqueous monomer solution;

(iii) adding a polymerization initiator or one or more constituents of a polymerization initiation system comprising two or more constituents to the aqueous monomer solution;

(iv) optionally, lowering the oxygen content of the aqueous monomer solution;

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

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

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

(viii) optionally drying the crushed polymer gel;

(ix) grinding the dried polymer gel to obtain absorbent polymer particles;

(x) sizing the pulverized absorbent polymer particles; And

(xi) optionally, treating the surface of the pulverized and classified absorbent polymer particles,

In step (i), the step of preparing an aqueous monomer solution is the following steps:

i1) providing a first fraction of acrylic acid;

i2) contacting a first fraction of acrylic acid with hydroxide in the first contacting step to obtain a first acrylate phase,

The first acrylate phase has a pH of 10 or more,

The first acrylate phase having a degree of neutralization of 0.95 or higher;

i3) contacting the first acrylate phase with an additional fraction of acrylic acid in the second contacting step to obtain a monomer solution,

The additional fraction of acrylic acid has a moisture content less than that of the first acrylate phase,

The monomer solution has a pH lower than the pH of the first acrylate phase,

The monomer solution has a degree of neutralization in the range of 0.5-0.9,

The amount of acrylate and acrylic acid in the aqueous monomer solution is in the range of 30-50% by weight based on the total amount of the aqueous monomer solution.

An apparatus for producing absorbent polymer particles in a production stream comprises the following a) to m):

a) a first container 501, designed to contain acrylic acid;

b) a second vessel 502, designed to contain a metal hydroxide;

c) cooling system 503:

The cooling device 503,

i) located downstream of the second vessel 502 and

ii) designed to cool metal hydroxides;

d) first mixing device 504:

The first mixing device 504 is

i) located downstream of the first container 501 and the cooling device 503,

ii) equipped with a cooler and propelled mixing mean;

e) third container 505:

The third container 505 is

i) located downstream of the first mixing device 504,

ii) designed to contain an aqueous monomer solution comprising at least one partially neutralized monoethylenically unsaturated monomer having a carboxylic acid group (α1);

f) a fourth container 506, designed to contain one or more crosslinking agents (α3);

g) second mixing device 507:

The second mixing device 507 is

i) located downstream of the third container 505 and the fourth container 506,

ii) designed to mix the monomer solution with one or more crosslinking agents (α3);

h) polymerization belt reactor 400:

The polymerization belt reactor 400 is

i) located downstream of the second mixing device 507,

ii) designed to receive the aqueous monomer solution and at least one crosslinking agent (α3) during polymerization of the monomer in the aqueous monomer solution to obtain a polymer gel;

j) crushing device 508:

The crushing device 508

i) located downstream of the polymerization belt reactor 400,

ii) designed to break polymer gels;

k) belt dryer 509:

The belt dryer 509 is

i) located downstream of the crushing device 508,

ii) designed to dry polymer gels;

l) Crushing device 510:

The crushing device 510 is

i) located downstream of the belt dryer 509,

ii) designed to pulverize the dried polymer gel to obtain absorbent polymer particles;

m) Classification device (511):

The classification device 511 is

i) located downstream of the grinding device 510,

ii) Designed to classify pulverized absorbent polymer particles.

According to the present invention, there is provided an absorbent polymer particle and a composite material comprising the absorbent polymer particle, which is usable in a diaper, has a low tendency to cause skin irritation and has a low monomer residual amount. In addition, there is provided an apparatus suitable for producing an absorbent polymer having a low residual amount of monomer.

1 is a flow chart showing the manufacturing steps of the method according to the invention;
2 is a flow chart showing the manufacturing steps of another method according to the present invention;
3 is a flow chart showing the manufacturing steps of another method according to the present invention;
4 is a schematic diagram of a basic setup of a polymerization belt reactor according to the present invention;
5 is a block diagram of an apparatus for producing absorbent polymer particles according to the present invention.

One or more objects of the present invention are achieved by a method 100 for producing absorbent polymer particles comprising the following manufacturing steps:

(i) preparing an aqueous monomer solution comprising at least one partially neutralized monoethylenically unsaturated monomer having a carboxylic acid group (α1) and at least one crosslinking agent (α3);

(ii) optionally, adding absorbent polymer microparticles to the aqueous monomer solution;

(iii) adding a polymerization initiator or one or more constituents of a polymerization initiation system comprising two or more constituents to the aqueous monomer solution;

(iv) optionally, lowering the oxygen content of the aqueous monomer solution;

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

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

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

(viii) optionally, drying the crushed polymer gel;

(ix) pulverizing the dried polymer gel to obtain absorbent polymer particles;

(x) classifying the pulverized absorbent polymer particles; And

(xi) optionally, treating the surface of the pulverized and classified absorbent polymer particles;

In the preparation step (i), the preparation of the aqueous monomer solution further includes the following steps:

(i1) providing a first fraction of acrylic acid;

(i2) contacting a first fraction of acrylic acid with hydroxide in the first contacting step to obtain a first acrylate phase,

The first acrylate phase has a pH of 10 or more,

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;

(i3) contacting the first acrylate phase with an additional fraction of acrylic acid in the second contacting step to obtain a monomer solution,

The additional fraction of acrylic acid has a moisture content less than that of the first acrylate phase,

The monomer solution has a pH lower than the pH of the first acrylate phase,

The monomer solution has a degree of neutralization in the range of 0.5-0.9, preferably in the range of 0.6-0.85, more preferably in the range of 0.65-0.8,

A step wherein the content of acrylate and acrylic acid in the aqueous monomer solution is in the range of 30-50% by weight, preferably in the range of 35-45% by weight with respect to the total amount of the aqueous monomer solution.

Herein, the subsequent steps of the manufacturing method according to the present invention may be carried out simultaneously or overlapped in time, or both. This corresponds in particular to steps (i)-(iv), and more specifically to steps (iii) and (iv). Throughout this application, the degree of neutralization is the mole ratio of hydroxide to moles of acrylic acid.

The method according to the invention is preferably a continuous process in which an aqueous monomer solution is continuously supplied and continuously introduced into the polymerization reactor. Preferably, the polymerization reactor is a polymerization belt reactor. Preferably, the aqueous monomer solution is added continuously and, therefore, is continuously fed onto the belt of the polymerization belt reactor. The polymer gel obtained is continuously discharged from the polymerization reactor and optionally crushed, dried, pulverized and classified in succession in a subsequent production step. However, this continuous process may be interrupted, for example in the following cases.

-When some parts of the manufacturing equipment, when the conveyor belt is used as a polymerization reactor, when replacing the belt material of the conveyor belt, etc.,

-When cleaning, to remove some parts of the manufacturing equipment, especially polymer deposits in tanks or pipes, or

-When it is necessary to manufacture absorbent polymer particles with different absorption characteristics, when initiating a new manufacturing step.

Preferred absorbent polymer particles according to the present invention, according to WSP 220.2 ("Word Strategic Partners" EDANA and INDA test method), in the range of 10 to 3,000 µm, preferably 20 to 2,000 µm, particularly preferably 150 to 850 µm It is a particle having an average particle size of. Herein, the content of particles having a particle size in the range of 300 to 600 μm in the absorbent polymer is at least 30% by weight, particularly preferably at least 40% by weight, most preferably at least 50% by weight, based on the total weight of the absorbent polymer particles. It is particularly preferred that it is %.

In the preparation step (i) of the method according to the invention, an aqueous monomer solution is prepared comprising at least one partially neutralized monoethylenically unsaturated monomer having a carboxylic acid group (α1) and at least one crosslinking agent (α3).

Preferred monoethylenically unsaturated monomers having a carboxylic acid group (α1) are those mentioned in DE 102 23 060 A1 as preferred monomers (α1), with acrylic acid being particularly preferred. Preferred monoethylenically unsaturated monomers having a carboxylic acid group (α1) include acrylic acid, methacrylic acid, ethacrylic acid, α-chloro-acrylic acid, α-cyano-acrylic acid, β-methylacrylic acid (crotonic acid), α-phenyl -Acrylic acid, β-acryloxypropionic acid, sorbic acid, α-chlorosorbic acid, 2'-methylisocrotonic acid, cinnamic acid, p-chloro cinnamic acid, β-stearyl acid, itaconic acid, citraconic acid, mesaconic acid , Glutaconic acid, aconitic acid, maleic acid, fumaric acid, tri-carboxy-ethylene- and maleic anhydride, acrylic acid and methacrylic acid are preferred, and acrylic acid is particularly preferred.

According to the invention, the absorbent polymer produced by the method according to the invention contains at least 50% by weight, preferably at least 70% by weight, more preferably at least 90% by weight of monomers with carboxylic acid groups, based on the dry weight of the polymer. It is preferable to include it by weight. According to the invention, the absorbent polymer produced by the method according to the invention is made of 50% by weight or more, preferably 70% by weight or more of acrylic acid, preferably has a degree of neutralization of 20 mol-% or more, particularly preferably It is particularly preferably 50 mol-% or more. The concentration of the partially neutralized monoethylenically unsaturated monomer having a carboxylic acid group (α1) in the aqueous monomer solution provided in the preparation step (i) is preferably 10 to 60% by weight, based on the total weight of the aqueous monomer solution, It is preferably in the range of 30 to 55% by weight, most preferably 40 to 50% by weight.

Preferably, in step (i2), neutralization of the monomer having a carboxylic acid group at the beginning of step (i) is implemented by adding sodium hydroxide to at least a portion of the aqueous monomer solution. Acrylic acid optionally includes a polymerization inhibitor. The polymerization inhibitor is preferably selected from the group consisting of monomethyl ether hydroquinone (MEHQ) or hydroquinone (HQ) or both.

Acrylic acid is preferably a polymerization inhibitor, for example mono methyl ether hydroquinone (MEHQ) or hydroquinone (HQ), based on the total weight of the first fraction of acrylic acid, preferably 100 to 2000 ppm, Or preferably 120 to 1000 ppm, or preferably 150 to 500 ppm. Preferably, the acrylic acid comprises mono methyl ether hydroquinone (MEHQ).

In the preparation step (i2) of the process according to the invention, a first fraction of acrylic acid is contacted with a hydroxide, wherein a pH of at least 10, preferably> pH 10.5 or preferably> pH 10.8 is achieved. In some cases, a maximum pH of 12 is achieved. The first fraction of acrylic acid preferably contains a hydroxide, a hydroxide: acrylic acid weight ratio of 0.1:1 to 1.5:1, or preferably 0.2:1 to 1.3:1, or preferably 0.3:1 to Included in the range of 1:1. When hydroxide is added to acrylic acid, at least a portion of the acrylic acid is converted to acrylate. In the present invention, at least 95 mol-% of acrylic acid on the first acrylate is acrylate.

In step (i3), the first acrylate phase is contacted with a further fraction of acrylic acid to obtain a monomer solution. The contacting in step (i3) can be carried out in any way that a person skilled in the art can choose to contact the two water phases. The additional fraction of acrylic acid has a lower moisture content than the first acrylate phase. The moisture content of the acrylic acid addition fraction is lower than that of the first fraction of acrylic acid. The acrylic acid first fraction has a moisture content, preferably in the range of 30 to 80% by weight, or 35 to 75% by weight, or 40 to 70% by weight, based on the total weight of the acrylic acid first fraction. The acrylic acid further fraction has a moisture content, preferably in the range of 0 to 8% by weight, or preferably 0 to 6% by weight, based on the total weight of the acrylic acid further fraction.

The monomer solution fed to step (i3) of the method according to the invention has a pH lower than that of the first acrylate phase. Preferably, the pH of the monomer solution represents the difference between the pH of the first acrylate phase and 0.5 to 6 pH units, or preferably 1 to 5 pH units, or preferably 1.5 to 4.5 pH units. According to the present invention, it is preferred that 60 to 80 mol-%, preferably 65 to 78 mol-%, or preferably 67 to 76 mol-% of acrylic acid in the monomer solution is an acrylate.

In step (i), the preparation of the aqueous monomer solution preferably comprises several additional steps:

α. Providing a first fraction of acrylic acid comprising acrylate and optionally MEHQ or HQ; And/or

β. Providing an acrylic acid monomer; And/or

χ. Providing an additional monoethylenically unsaturated monomer (α2).

Steps β-χ may proceed in any order, and may be performed in any combination with step α. In a preferred embodiment, only step α is carried out. In another preferred embodiment, steps α and β are carried out. In another preferred embodiment, steps α and χ are carried out. Also, the order can be different in step (i). In a preferred embodiment, it is possible to firstly provide a crosslinking agent (α3) and then perform step α and optionally one of steps β and/or χ. In another preferred embodiment, step α alone or in combination with step β or χ is carried out first, and then the crosslinking agent (α3) is added.

The content of acrylate and acrylic acid in the aqueous monomer solution is less than 55% by weight, preferably less than 50% by weight, or preferably less than 45% by weight, based on the total weight of the aqueous monomer solution. In addition, the content of acrylate and acrylic acid in the aqueous monomer solution is preferably 30% by weight or more.

In addition, the aqueous monomer solution may contain a monoethylenically unsaturated monomer (α2) copolymerizable with (α1). Preferred monomers (α2) are those mentioned as preferred monomers (α2) in DE 102 23 060 A1, with acrylamide being particularly preferred.

Preferred crosslinking agents (α3) according to the present invention are compounds having two or more ethylenically unsaturated groups in one molecule (Class I crosslinking agent), condensation reaction (= condensation crosslinking agent), monomer (α1) or (α2) in addition reaction or ring-opening reaction. A compound having two or more functional groups capable of reacting with a functional group of) (Class II crosslinking agent), at least one functional group capable of reacting with a functional group of a monomer (α1) or (α2) in a condensation reaction, addition reaction, or ring opening reaction, and one A compound having the above ethylenically unsaturated groups (Class III crosslinking agent), or a polyvalent metal cation (Class IV crosslinking agent). Thus, when using a class I crosslinker compound, crosslinking of the polymer is achieved by radical polymerization of monoethylenically unsaturated monomers (α1) or (α2) with ethylenically unsaturated groups of the crosslinker molecule, and class II crosslinker compounds and class IV In the case of using a polyvalent metal cation of the crosslinking agent, the crosslinking of the polymer is performed through a condensation reaction of the functional group of the monomer (α1) or (α2) with the functional group (Class II crosslinking agent) or through the electrostatic interaction of the polyvalent metal cation (Class IV crosslinking agent). Through, is achieved. When using a class III crosslinking agent compound, crosslinking of the polymer is achieved by radical polymerization of ethylenically unsaturated groups as well as condensation reactions between the functional groups of the crosslinking agent and the functional groups of the monomer (α1) or (α2).

Preferred crosslinking agents (α3) are all compounds mentioned in DE 102 23 060 A1 as crosslinking agents of classes I, II, III and IV (α3),

-As a class I crosslinker compound, prepared using N,N'-methylene bisacrylamide, polyethylene glycol di(meth)acrylate, triallylmethylammonium chloride, tetraallylammonium chloride, and 9 mol of ethylene oxide per mol of acrylic Allyl nonaethylene glycol acrylate is particularly preferred, N,N'-methylene bisacrylamide is particularly more preferred,

-As class IV crosslinking agent compounds, Al ₂ (SO ₄ ) ₃ and hydrates thereof are particularly preferred.

Preferred water absorbent polymers prepared by the process according to the invention are polymers, each crosslinked by the following classes of crosslinkers or by the following combinations of crosslinkers: I, II, III, IV, I II, I III, I IV , I II III, I II IV, I III IV, II III IV, II IV or III IV.

Other preferred absorbent polymers prepared by the process according to the invention are polymers, crosslinked by any crosslinking agents mentioned in DE 102 23 060 A1 as class I crosslinkers, wherein N,N'-methylene bisacrylamide, Polyethylene glycol di(meth)acrylate, triallyl-methylammonium chloride, tetraallylammonium chloride, and allylnonaethylene-glycol acrylate prepared from 9 mol of ethylene oxide per mol of acrylic acid are more preferred as class I crosslinking agents, N,N'-methylene bisacrylamide is even more preferred.

The aqueous monomer solution may further contain a water-soluble polymer (α4). Preferred water soluble polymers (α4) are partially or fully saponified polyvinyl alcohol, polyvinylpyrrolidone, starch or starch derivatives, polyglycols or polyacrylic acid. The molecular weight of these polymers is not important as long as the polymer is water-soluble. Preferred water-soluble polymers (α4) are starch or starch derivatives or polyvinyl alcohol. Water-soluble polymers (α4), preferably synthetic polymers, for example polyvinyl alcohol, can be used as a graft base for the monomers to be polymerized, as well as these water-soluble polymers with polymer gels or already dried absorbent polymers. Mixing of is also possible.

The aqueous monomer solution may also contain auxiliary substances (α5), in particular complexing agents such as EDTA and the like.

In the aqueous monomer solution, the relative content of the monomers (α1) and (α2), the crosslinking agent (α3), the water-soluble polymer (α4) and the auxiliary substance (α5) is, preferably, the water absorbency obtained after drying the crushed polymer gel. The polymer structure is chosen so that it is constructed as follows:

-Monomer (α1) 20 to 99.999% by weight, preferably 55 to 98.99% by weight, particularly preferably 70 to 98.79% by weight,

-Monomer (α2) 0 to 80% by weight, preferably 0 to 44.99% by weight, particularly preferably 0.1 to 44.89% by weight,

-Crosslinking agent (α3) 0 to 5% by weight, preferably 0.001 to 3% by weight, particularly preferably 0.01 to 2.5% by weight,

-Water-soluble polymer (α4) 0 to 30% by weight, preferably 0 to 5% by weight, particularly preferably 0.1 to 5% by weight,

-Auxiliary substances (α5) 0 to 20% by weight, preferably 0 to 10% by weight, particularly preferably 0.1 to 8% by weight, and

-0.5 to 25% by weight of water (α6), preferably 1 to 10% by weight, particularly preferably 3 to 7% by weight,

The total weight of (α1) to (α6) is 100% by weight.

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

In the preparation step (ii), optionally fine particles of the water absorbent polymer may be added to the aqueous monomer solution. Independently of the selection step (ii), the microparticles of the water absorbent polymer are, at one of a time selected from the group consisting of after step (iii), after step (iv) and before step (v), or at least two of these. It can be added to the aqueous monomer solution at a time.

The absorbent fine particles are preferably absorbent polymer particles whose composition corresponds to that of the aforementioned absorbent polymer particles, preferably at least 90% by weight, more preferably at least, based on the total weight of the absorbent fine particles. 95% by weight, most preferably at least 99% by weight of the absorbent fine particles have a particle size of less than 200 μm, preferably less than 150 μm and particularly preferably less than 100 μm.

In a preferred embodiment of the method according to the present invention, optionally, the absorbent fine particles which can be added to the aqueous monomer solution in the preparation step (ii) are the absorbent fine particles obtained in the preparation step (x) of the method according to the present invention. , That is, recycled.

The fine particles can be added to the aqueous monomer solution using any mixing device deemed suitable for this purpose by those skilled in the art. In a preferred embodiment of the invention in which it is particularly useful that the method is carried out continuously as described above, the fine particles are added to the aqueous monomer solution in a mixing device, and the first stream of fine particles and the second stream of the aqueous monomer solution are continuously However, from different directions, it is applied onto the rotating mixing device. This type of mixing setup comprises a preferably cylindrical non-rotating stator in the mixing zone, at its center likewise preferably a so-called "rotor, in which a cylindrical rotor rotates. It can be implemented in "Rotor Stator Mixer". A notch is usually provided on the wall of the rotor and the wall of the stator. For example, a notch in the form of a slot capable of applying a high shear force by suctioning a mixture of fine particles and an aqueous monomer solution is provided.

In this context, the first stream as fine particles and the second stream as an aqueous monomer solution are in the range of 60-120°, preferably in the range of 75-105°, more preferably in the range of 85-95°, most preferably about 90°. It is particularly preferable to achieve the angle δ of. In addition, a mixture stream of fine particles and an aqueous monomer solution discharged from the mixer, and a first stream of fine particles flowing into the mixer are in the range of 60-120°, preferably in the range of 75-105°, and more preferably in the range of 85-95°. It is desirable to achieve an angle ε of the range, most preferably about 90°.

This type of mixing setup can be implemented, for example, using the mixing apparatus disclosed in DE-A-25 20 788 and DE-A-26 17 612. A specific example of a mixing device that can be used to add fine particles to the aqueous monomer solution in the production step (ii) of the present invention is described in Staufen, Germany KG IKA ^® Werke GmbH & Co. It is a mixing device, which is commercially available under the trade names of MHD 2000/4, MHD 2000/05, MHD 2000/10, MDH 2000/20, MHD 2000/30 and MHD 2000/50 by the company, and a mixing device MHD 2000/20 is particularly preferred. Another mixing device that can be used is a device provided for example by the company ystral GmbH, Dottingen, Wallenchten, Germany under the trade name "Conti TDS" or from the company Kinematika AG, Rutau, Switzerland, for example under the trade name Megatron ^® .

The amount of fine particles that can be added to the aqueous monomer solution in the preparation step (ii) is preferably in the range of 0.1 to 15% by weight, even more preferably in the range of 0.5 to 10% by weight, based on the weight of the aqueous monomer solution. It is preferably in the range of 3 to 8% by weight.

In the preparation step (iii) of the method according to the invention, to the aqueous monomer solution, a polymerization initiator or at least one constituent of a polymerization initiator system composed of two or more constituents is added.

As the polymerization initiator for polymerization initiation, all initiators that form radicals under polymerization conditions, which are commonly used in the production of a super absorbent agent, can be used. Among them, thermal catalysts, redox catalysts and photo-initiators are activated by energetic irradiation. The polymerization initiator may be dissolved or dispersed in the aqueous monomer solution. It is preferred to use a water-soluble catalyst.

As the thermal initiator, all compounds recognized by those skilled in the art that decompose under elevated temperature to form radicals can be used. At temperatures lower than 180° C., more preferably at temperatures lower than 140° C., thermal polymerization initiators having a half-life shorter than 10 seconds, preferably shorter than 5 seconds are particularly preferred. Peroxide, hydroperoxide, hydrogen peroxide, persulfate and azo compounds are particularly preferred thermal polymerization initiators. In some cases, it is beneficial to use mixtures of various thermal polymerization initiators. Among these mixtures, a mixture consisting of hydrogen peroxide and potassium persulfate or sodium persulfate is preferable, and these may be used in any desired quantitative ratio. Suitable organic peroxides are, preferably, acetylacetone peroxide, methyl ethyl ketone peroxide, benzoyl peroxide, lauroyl peroxide, acetyl peroxide, capryl peroxide, isopropyl peroxydicarbonate, 2-ethyl Hexyl peroxydicarbonate, tert.-butyl hydroperoxide, cumene hydroperoxide, and tert.-amyl perpivalate, tert.-butyl perpivalate, tert.-butyl perneohexa Noate, tert.-butyl isobutyrate, tert.-butyl per-2-ethylhexenoate, tert.-butyl perisononanoate, tert.-butyl permalate, tert.-butyl perbenzoate , tert.-butyl-3,5,5-trimethylhexanoate and amyl perneodecanoate. In addition, the following thermal polymerization initiators are preferred: azo compounds, for example azo-bis-isobutyronitrile, azo-bis-dimethylvaleronitrile, azo-bis-ami-dinopropane dihydrochloride (azo-bis-ami-dinopropane dihydrochloride), 2,2'-azobis-(N,N-dimethylene)isobutyramidine di-hydrochloride, 2-(carbamoylazo)isobutyronitrile and 4, 4'-azobis-(4-cyano-valeric acid). The aforementioned compounds are used in conventional amounts, preferably in the range of 0.01 to 5 mol-%, more preferably in the range of 0.1 to 2 mol-%, respectively, based on the weight of the monomer to be polymerized.

The redox catalyst comprises two or more constituents, usually one or more of the aforementioned peroxo compounds and one or more reducing components, preferably ascorbic acid, glucose, sorbose. , Mannose, ammonium or alkali metal hydrogen sulfite, sulfate, thiosulfate, hypersulfite or sulfide, metal salts such as iron II ions or silver salts, or sodium hydroxymethyl sulfoxylate. Preferably, ascorbic acid or sodium pyrosulfite is used as the reducing material component of the redox catalyst. Based on the amount of monomer used in the polymerization, 1 x 10 ^-5 to 1 mol-% of the reducing material component of the redox catalyst and 1 x 10 ^-5 to 5 mol-% of the oxidizing material component of the redox catalyst is used. In place of the oxidizing material component of the redox catalyst or as a complement thereof, one or more, preferably, water-soluble azo compounds may be used.

The polymerization is preferably initiated by the action of energy irradiation, so-called photo-initiators are generally used as initiators. Such photo-initiators may include, for example, so-called α-splitters, H-abstracting systems, or may include azidos. Examples of such initiators include benzophenol derivatives such as Michler's ketone, phenanthrene derivatives, fluorine derivatives, anthraquinone derivatives, thioxanthone derivatives, coumarin derivatives, benzoin ethers and derivatives thereof, azo compounds, such as For example, there are the aforementioned radical formers, substituted hexaarylbisimidazoles or acylphosphine oxides. Examples of azide include 2-(N,N-dimethylamino)ethyl-4-azidocinnamate, 2-(N,N-dimethylamino)ethyl-4-azidonaphthylketone, 2-(N ,N-di-methylamino)ethyl-4-azidobenzoate, 5-azido-1-naphthyl-2'-(N,N-dimethylamino)ethylsulfone, N-(4-sulfonylazido Phenyl) maleimide, N-acetyl-4-sulfonyl-azidoaniline, 4-sulfonylazidoaniline, 4-azidoaniline, 4-azidophenacyl bromide, p-azidobenzoic acid, 2,6 -Bis(p-azidobenzylidene)cyclohexanone and 2,6-bis(p-azidobenzylidene)-4-methylcyclohexanone. Another group for photo-initiators are di-alkoxy ketals such as 2,2-dimethoxy-1,2-diphenylethan-1-one. The photo-initiator, when used, is generally used in an amount of 0.0001 to 5% by weight, based on the monomer to be polymerized.

In another embodiment of the method according to the invention, in the preparation step (iii), the initiator comprises the following components,

iiia. Peroxodisulfate; And

iiib. It contains an organic initiator molecule containing 3 or more oxygen atoms or 3 or more nitrogen atoms,

It is preferred to include peroxodisulfate and organic initiator molecules in a molar ratio ranging from 20:1 to 50:1. In one aspect of this embodiment, the concentration of the initiator component iiia is preferably in the range of 0.05 to 2% by weight based on the weight of the monomer to be polymerized. In another aspect of this embodiment, the organic initiator molecule is 2,2-dimethoxy-1,2-diphenylethan-1-one, 2,2-azobis-(2-amidinopropane)dihydrochloride , 2,2-azobis-(cyano valeric acid), or a combination of two or more thereof is preferably selected from the group consisting of. In another aspect of this embodiment, peroxodisulfate is _{a compound of the general formula M 2} S ₂ O ₈ , wherein M is _{selected from the group consisting of NH 4} , Li, Na, Ka or a combination of two or more thereof. It is desirable. The aforementioned components are particularly suitable for initiating polymerization with UV in the polymerization step (vi) of the process of the invention. With the use of such a composition, a reduction in the residual amount of monomers and a reduction in yellowing of the absorbent polymer particles obtainable by the method according to the invention are further achieved.

In this context, also, step (iii) of adding a polymerization initiator may be performed prior to step (iv), simultaneously with step (iv) or in time overlap with step (iv), i.e., the oxygen content of the aqueous monomer solution is reduced. When done, it should be noted that it can be performed. When using a polymerization initiator system that contains two or more constituents and is active only when all of the constituents are added, such as a preferred initiator system containing hydrogen peroxide, sodium peroxodisulfate and ascorbic acid, these polymerizations One or more constituents of the initiator system are added, for example, prior to the preparation step (iv), while the remaining constituents or the remaining constituents necessary to achieve the activity of the polymerization initiator system are after step (iv), possibly even prepared. It is added after step (v).

In the preparation step (iv) of the method according to the invention, optionally, a reduction in the oxygen content of the aqueous monomer solution is carried out. The optional step (iv), that is, the step of lowering the oxygen content of the aqueous monomer solution, may be performed before, during or after the production step (ii), and preferably, fine particles are added in the production step (ii). Thereafter, reduction of the oxygen content of the aqueous monomer solution is performed.

The reduction in the oxygen content of the aqueous monomer solution can be achieved by contacting the aqueous monomer solution with an inert gas such as nitrogen. The inert gas phase in contact with the aqueous monomer solution is free of oxygen and is therefore characterized by a very low oxygen partial pressure. As a result, oxygen is converted from the aqueous monomer solution into the inert gas phase until the partial pressure of oxygen in the inert gas phase and the oxygen partial pressure in the aqueous monomer solution become the same. Contact of the monomer water phase and the inert gas phase can be achieved, for example, by introducing bubbles of inert gas into the monomer solution in the same direction as the monomer supply direction, or in the opposite direction or at an intermediate angle thereof. For example, mixing can be performed well using a nozzle, a static mixer, a dynamic mixer, or a bubble column. Prior to the polymerization reaction, the oxygen content of the monomer solution is preferably dropped to less than 1 ppmw (ppm by weight), more preferably less than 0.5 ppmw, based on the total weight of the monomer solution.

In the production step (v) of the method according to the invention, the aqueous monomer solution is fed to a position upstream of the polymerization reactor, preferably a conveyor belt, particularly preferably a conveyor belt, and in the production step (vi), the monomer in the aqueous monomer solution is It is polymerized in a polymerization reactor to produce a polymer gel. When the polymerization is carried out on a polymerization belt as a polymerization reactor, it is obtained as a polymer gel strand in the downstream section of the conveyor belt, which is preferably crushed into gel particles before drying.

As the polymerization reactor, any reactor that a person skilled in the art considers suitable for continuous or batch polymerization of monomers such as acrylic acid in an aqueous solution can be used. An example of a suitable polymerization reactor is a kneading reactor. The polymer gel formed by polymerization of an aqueous monomer solution is continuously crushed in a kneader, for example by means of a contrarotatory stirrer shaft as described in WO 2001/38402.

Another example for a preferred polymerization reactor is a conveyor belt. As a conveyor belt usable in the method according to the present invention, any conveyor belt which a person skilled in the art considers useful as a suitable support material for forming a hydrogel by polymerization after the above-described aqueous monomer solution is loaded thereon. Can be used. Examples of conveyor belts that can be used in the method according to the invention are described in DE-A-35 44 770, EP-A-0 955 086 and EP-A-1 683 813.

The conveyor belt generally includes an endless moving conveyor belt and two or more guide rollers passing over a support member, at least one of the rollers driving the belt and the other one adjusting It is configured to be possible. Optionally, a winding and feed system is provided for a release sheet which can be used in section on the upper surface of the conveyor belt. The device comprises a supply and metering system for the reactive components, followed by the supply and metering system, along with a cooling and heating device, an optional irradiating mean arranged in the direction of movement of the conveyor belt, and a conveyor belt. And a removal system of polymer gel strands disposed in the vicinity of the guide rollers for return travel of the. According to the invention, in order to complete the polymerization at the maximum possible space-time yield, on both sides of the horizontal support member near the upper run of the conveyor belt, starting in the supply and metering system area, extending upwardly. There is a support member, which upwardly extending support members intersect each other at a point where their longitudinal axes are below the upper run, and support the conveyor belt so that the conveyor belt is properly trough-shaped. Thus, according to the present invention, the conveyor belt comprises a plurality of trough-shaped support and bearing members forming a deep trough-like or dish-like structure for the incoming reaction components, near the supply system of the reaction components. Supported by the field. The preferred trough-like shape is determined by the shape and arrangement of the support members disposed along the length of the path of the upper run. The supporting members should be relatively adjacent to each other in the zone into which the reaction components are introduced, but in subsequent zones, after polymerization has begun, the supporting members may be arranged somewhat spaced apart from each other. The angle of inclination of the support member and the cross-section of the support member may be varied so as to gradually flatten the initial deep trough toward the end of the polymerization zone and bring it back into an expanded state. In a further embodiment of the invention, each support member is preferably formed by a cylindrical or spherical roller rotatable about its longitudinal axis. By changing the structure of the roller as well as the cross section of the roller, the desired cross-sectional shape of the trough is easily achieved. When the belt transitions from a flat shape to a trough-shaped shape and when it is restored to a flat shape again, a conveyor belt that is flexible in both the longitudinal direction and the transverse direction is provided to ensure proper formation of the trough by the conveyor belt. desirable. In the production step (vi), the monomers of the aqueous monomer solution are preferably polymerized on a belt, whereby a polymer gel is obtained. Preferably, the polymer gel is obtained in the area downstream of the belt. The polymer gel is preferably crushed before drying to obtain polymer gel particles.

In a preferred embodiment of the present invention, radical polymerization is performed on the monomer solution to obtain a polymer precursor. Radical polymerization can be initiated by any means that can be selected by one of ordinary skill in the art. Preferably, the initiation is selected from the group consisting of heat, light irradiation, or combinations thereof. Initiation by light irradiation is preferred. Light irradiation is preferably provided by UV irradiation. Preferably, the polymer precursor is subjected to an additional crosslinking step. The additional crosslinking step can be provided as any step that a person skilled in the art can select as a crosslinking step. Additional crosslinking steps may include the following steps:

a1. Monomer addition to the polymer precursor;

a2. Addition of a crosslinking agent (?3) to the polymer precursor;

a3. Adding an initiator to the polymer precursor;

a4. Initiation of polymerization.

Steps a1 to a4 may be performed alone, or may be performed in any order with any combination thereof.

In the production step (vii) of the method according to the invention, the polymer gel particles obtained in the polymerization reactor, preferably the polymer gel particles obtained in the kneading reactor or the polymer gel strands obtained in the downstream section of the conveyor belt, are obtained from the reactor. The polymer gel strands discharged, in particular obtained on a conveyor belt, are (additionally) crushed to obtain polymer gel particles. Preferably, the polymer gel strands produced are recovered from the conveyor belt as long strands of soft semi-solid concentration and then conveyed for further processing such as crushing.

The crushing of the polymer gel or gel strand is preferably carried out in at least 3 steps:

-In the first step, using a cutting unit, preferably a knife, for example the knife mentioned in WO-A-96/36464, the polymer gel into a flat gel strip, preferably 5 to 500 mm in length, It is preferably in the range of 10 to 300 mm, particularly preferably in the range of 100 to 200 mm, the height is in the range of 1 to 30 mm, preferably in the range of 5 to 25 mm, particularly preferably in the range of 10 to 20 mm, and the width is in the range of 1 to 500 mm, preferably in the range of 5 to 250 mm, particularly preferably in the range of 10 to 200 mm, cut into flat gel strips;

-In the second step, using a shredding unit, preferably a breaker, the gel strip is a piece of gel, preferably in the range from 3 to 100 mm, preferably from 5 to 50 mm, Crushed into pieces of gel, with a height ranging from 1 to 25 mm, preferably 3 to 20 mm, and a width ranging from 1 to 100 mm, preferably 3 to 20 mm;

-In the third step, a "wolf (crushing)" unit, preferably a mincer, preferably a mincer with a screw and a perforated plate with a screw moving toward the perforated plate, is used, preferably a piece of gel Grind and mash into polymer gel particles that are smaller than a piece of gel.

This achieves an optimum surface-volume ratio, which is advantageous for the drying behavior of the manufacturing step (viii). Gels crushed in this way are particularly suitable for belt drying. The crushing in three steps imparts better "airability" due to the air channels existing between the granulate kernels.

In the production step (viii) of the method according to the invention, the polymer gel is dried. During this drying step (viii), based on the amount of polymer gel in the range of 0.5 to 5 t, or preferably 0.8 to 4.5 t, the moisture is 120 to 240 kg/min, preferably 130 to 230 kg/min, or It is preferably removed in the range of 140 to 220 kg/min, or preferably 150 to 210 kg/min, or preferably 160 to 200 kg/min. Preferably, the moisture reduction from 40 to 60% by weight based on the total weight of the polymer gel to 3 to 7% by weight based on the total weight of the dried polymer is 1 to 60 minutes, or preferably 2 to 50 minutes. , Or is preferably achieved within the range of 3 to 40 minutes. The dry polymer obtained preferably has a moisture content in the range of 3 to 7% by weight, or preferably 3.5 to 6.5% by weight, or preferably 4 to 6% by weight, based on the total weight of the dried polymer. . Moisture content is determined by Karl-Fischer titration.

Drying of the polymer gel can be carried out in any dryer or oven that one of ordinary skill in the art considers to be suitable for drying the polymer gel or the aforementioned gel particles. Examples include a rotary tube furnace, a fluidized bed dryer, a plate dryer, a paddle dryer, and an infrared dryer.

In particular, a belt dryer is preferred. Belt dryers are in particular convective system of drying for the non-harsh treatment of through-airable products. The product to be dried is placed on a continuous conveyor belt through which gas is allowed and exposed to a heated gas stream, preferably a stream of air. The drying gas is preferably recycled so that it can be extremely highly saturated during iterative passage through the product bed. A predetermined fraction of the dry gas, preferably at least 10%, more preferably at least 15%, most preferably at least 20%, preferably at most 50%, more preferably at most 40 of the gas content in one pass. %, most preferably at most 30%, is discharged from the dryer as highly saturated vapor to remove any evaporated moisture from the product. The temperature of the heated gas stream is preferably at least 50° C., more preferably at least 100° C., most preferably at least 150° C., preferably at most 250° C., more preferably at most 220° C., most preferably at most. It is 200°C.

The size and design of the dryer will depend on the product being processed, the manufacturing capacity and the drying duty. The belt dryer can be implemented as a single-belt, multi-belt, multi-stage or multistory system system. The invention is preferably practiced using a belt dryer with one or more belts. One-belt dryers are particularly preferred. In order to ensure optimal performance of the belt-drying operation, the drying properties of the absorbent polymer are each determined according to the selected processing parameters. The belt hole size and mesh size are set according to the product. Likewise, certain surface hardening, such as electropolishing or teflonizing, is also possible.

The polymer gel to be dried is preferably applied to the belt of a belt dryer using a swivel belt. The feeding height, i.e. the vertical distance between the swivel belt and the belt of the belt dryer, is preferably 10 cm or more, more preferably 20 cm or more, most preferably 30 cm or more, preferably 200 cm or less, more preferably It is 120 cm or less, most preferably 40 cm or less. The thickness of the polymer gel to be dried on the belt dryer is preferably 2 cm or more, more preferably 5 cm or more, most preferably 8 cm or more, preferably 20 cm or less, more preferably 15 cm or less, most It is preferably 12 cm or less. The belt speed of the belt dryer is preferably 0.005 m/s or more, more preferably 0.01 m/s or more, most preferably 0.015 m/s or more, preferably 0.05 m/s or less, more preferably 0.03. m/s or less, most preferably 0.025 m/s or less.

In addition, according to the present invention, the polymer gel is dried to contain a moisture content in the range of 0.5 to 25% by weight, preferably 1 to 10% by weight, particularly preferably 3 to 7% by weight, based on the dried polymer gel. It is desirable.

In the production step (ix) of the method according to the present invention, the dried polymer gel is pulverized to obtain absorbent polymer particles.

For pulverizing the dried polymer gel, any apparatus that one skilled in the art considers suitable for pulverizing the dried polymer gel or the dried polymer gel described above can be used. As examples of suitable grinding devices, mention may be made of a single- or multi-stage roll mill, preferably a two- or three-stage roll mill, a pin mill, a hammer mill or a vibratory mill.

In the production step (x) of the method according to the invention, the pulverized water absorbent polymer particles are preferably classified using a suitable sieve. Here, after classification of the absorbent polymer particles, the proportion of the polymer particles having a particle size of less than 150 μm, respectively, based on the total weight of the absorbent polymer particles is less than 10% by weight, preferably less than 8% by weight, particularly preferably 6 It is particularly preferred that the proportion of polymer particles which is less than% by weight and the particle size is greater than 850 μm is less than 10% by weight, preferably less than 8% by weight, particularly preferably less than 6% by weight. In addition, after classification of the water absorbent polymer particles, it is preferable that 30% by weight or more, preferably 40% by weight or more, more preferably 50% by weight or more of the water absorbent polymer particles have a particle size in the range of 300 to 600 μm.

In the production step (xi) of the method according to the invention, the surface of the pulverized and classified absorbent polymer particles is selectively processed. As a means for processing the surface of the absorbent polymer particles, any means considered suitable for this purpose can be used by those skilled in the art. Examples of the surface treatment include, for example, surface treatment, surface treatment using water-soluble salts such as aluminum sulfate or aluminum lactate, surface treatment using inorganic particles such as silicon dioxide, and the like. Preferably, the component used for surface treatment of the polymer particles (crosslinking agent, water-soluble salt) is added to the water absorbent polymer particles in the form of an aqueous solution. After mixing the particles with this aqueous solution, it is heated in the range of 150 to 230°C, preferably 160 to 200°C in order to accelerate the surface crosslinking reaction. A preferred additional treatment for the absorbent polymer particles or surface-crosslinked absorbent particles is to mix the particles once or more than once with the zeolite. The zeolite preferably contains one element selected from the group consisting of Ag, Na, and Zn, or a mixture of two or more thereof. Preferably, the zeolite is mixed with the absorbent polymer particles in the range of 0.05 to 5% by weight or preferably in the range of 0.1 to 13% by weight or preferably in the range of 0.2 to 10% by weight, based on the total weight of the absorbent polymer particles. By this type of treatment, post-treated absorbent polymer particles are obtained.

In a preferred embodiment of the invention, the degree of neutralization of the acrylate phase in step (i2) is> 1, preferably> 1.05, more preferably> 1.1, most preferably> 1.15. Preferably, the degree of neutralization of the acrylate phase in step (i2) is not more than 1.2.

In a preferred embodiment of the present invention, the temperature of the first fraction of acrylic acid and the temperature of the hydroxide are 2 K or more, preferably 5 K or more, more preferably 10 K or more, more preferably 15 K or more, more Preferably it has a difference of 20 K or more, and most preferably 25 K or more. Preferably, the hydroxide has a temperature in the range of 0 to 20°C, more preferably 0 to 15°C, more preferably 0 to 10°C, most preferably 0 to 5°C.

In a preferred embodiment of the present invention, the additional fraction of acrylic acid comprises less than 5% by weight, preferably less than 3% by weight, more preferably less than 2% by weight of moisture, based on the total weight of the acrylic acid addition fraction. .

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

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

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

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

In a preferred embodiment of the invention, the monomer solution is contacted with activated carbon in an additional contacting step. Preferably, an additional contacting step is carried out prior to step (i2). Preferably, the further contacting step is carried out for a period in the range of 60-240 minutes, preferably 80-220 minutes, more preferably 100-200 minutes, most preferably 120-180 minutes. Preferably, the amount of activated carbon used in the further contacting step is in the range of 0.05 to 10% by weight, preferably 0.1 to 5% by weight, more preferably 0.2 to 1% by weight, based on the total weight of the monomer solution. Preferably, the activated carbon is a powder comprising granules. 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 invention, at least the first contact step or the second contact step or both steps are carried out for a period in the range of 10 to 300 minutes, preferably 20 to 250 minutes, more preferably 30 to 200 minutes. .

In a preferred embodiment of the invention, at least a first contact step or a second contact step or both, preferably both steps (sum), less than 40° C., preferably less than 30° C., more preferably Is carried out at a temperature of the aqueous monomer solution below 25°C.

In a preferred embodiment of the invention, in step (v), the polymerization reactor is a polymerization belt reactor. A preferred polymerization belt reactor comprises a conveyor belt, preferably an endless conveyor belt.

In a preferred embodiment of the present invention, the polymer gel discharged in the preparation step (vii) is in the range of 40 to 60% by weight, preferably 50 to 60% by weight, more preferably 53 to 56% by weight, based on the polymer gel. Contains moisture as.

In a preferred embodiment of the present invention, the polymer gel discharged in the preparation step (vii) is 10 to 200 mm, preferably 10 to 100 mm, more preferably 15 to 75 mm, most preferably 15 to 50 mm. It is a polymer gel sheet, characterized by a range of thicknesses.

In a preferred embodiment of the present invention, the polymer gel discharged in the production step (vii) is 30 to 300 cm, preferably 50 to 250 cm, more preferably 60 to 200 cm, most preferably 80 to 100 cm. It is a polymer gel sheet, characterized by a range of widths.

In one embodiment of the invention, the polymerization in step (vi) is carried out in the presence of a blowing agent. The blowing agent is added to the aqueous monomer solution in one step selected from the group consisting of step (i), step (ii), step (iii), step (iv), step (v) and step (vi), or a combination of two or more thereof. I can. Preferably, the blowing agent is added to the monomer solution in step (i). The blowing agent should be added before or immediately after the polymerization initiation of step (vi). Particularly preferably, the blowing agent is added to the monomer solution immediately after or simultaneously with the addition of the initiator or components of the initiator system. Preferably, the blowing agent is in an amount ranging from 500 to 4000 ppmw, preferably 1000 to 3500 ppmw, more preferably 1500 to 3200 ppmw, most preferably 2000 to 3000 ppmw, based on the total weight of the monomer solution. It is added to the monomer solution.

The blowing agent is a material capable of forming cells or pores or both through the foaming process during the monomer polymerization process. The foaming process is preferably endothermic. A preferred endothermic foaming process is initiated by an exothermic polymerization, a crosslinking reaction, or heat derived from both reactions. Preferred blowing agents are physical blowing agents or chemical blowing agents or both. Preferred physical blowing agents are one or a combination of two or more selected from the group consisting of CFCs, HCFCs, hydrocarbons and CO _2. The preferred CO ₂ is liquid CO ₂ . Preferred hydrocarbons are one or a combination of two or more selected from the group consisting of pentane, isopentane and cyclopentane. A preferred chemical blowing agent is one selected from the group consisting of carbonate blowing agents, nitrites, peroxides, calcined soda, oxalic acid derivatives, aromatic azo compounds, hydrazines, azides, N,N'-dinitrosoamides and organic blowing agents , Or a combination of two or more of these.

A particularly preferred blowing agent is a carbonate blowing agent. Carbonate blowing agents that can be used according to the invention are described in US 5,118,719A, which is incorporated herein by reference. Preferred carbonate blowing agents are carbonate containing salts or bicarbonate containing salts or both. Other preferred carbonate blowing agents are CO ₂ gas, CO ₂ solids, ethylene carbonate, sodium carbonate, potassium carbonate, ammonium carbonate, magnesium carbonate, or magnesium hydroxy carbonate, calcium carbonate, barium carbonate, bicarbonate, hydrates thereof, other cations and One selected from the group consisting of natural carbonates, or a combination of two or more thereof. A preferred natural carbonate is dolomite. The above-described carbonate blowing agent releases _{CO 2} upon heating when dissolved or dispersed in a monomer solution. A particularly preferred carbonate blowing agent is MgCO ₃ , and this compound may be represented by the formula (MgCO ₃ ) ₄ ·Mg(OH) ₂ ·5-H ₂ O. Another preferred carbonate blowing agent is (NH ₄ ) ₂ CO ₃ . MgCO ₃ and (NH ₄ ) ₂ CO ₃ can also be used as a mixture. Preferred carbonate blowing agents are carbonate salts of polyvalent cations such as Mg, Ca, and Zn. Examples of such carbonate blowing agents include 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 . Certain polyvalent transition metal cations may also be used, but some cations, such as ferric cations, may cause color staining and undergo reduction oxidation reactions or hydrolytic equilibrium in water. This can make it difficult to control the quality of the final polymer product. In addition, other polyvalent cations such as Ni, Ba, Cd, Hg will also be unacceptable due to potential toxicity or skin sensitization effects.

The preferred nitrite is ammonium nitrite. A preferred peroxide is hydrogen peroxide. Preferred aromatic azo compounds are one selected from the group consisting of triazene, aryl azosulfone, aryl azotriarylmethane, hydrazo compound, diazoether and diazoaminobenzene, or a combination of two or more thereof. A preferred hydrazine is phenylhydrazine. Preferred azide is carbonyl azide or sulfonyl azide, or both. A preferred N,N'-dinitrosoamide is N,N'-dimethyl-N,N'-dinitrosoterephthalamide.

A solution to at least one of the aforementioned challenges is provided by an apparatus for producing absorbent polymer particles in a production stream, comprising:

a) a first container designed to contain acrylic acid;

b) a second container designed to contain a metal hydroxide;

c) cooling system:

The cooling device,

i) located downstream of the second container

ii) designed to cool metal hydroxides;

d) first mixing device:

The first mixing device

i) located downstream of the first vessel and the cooling device,

ii) equipped with cooler and propeller type mixing means;

e) third container:

The third container

i) located downstream of the first mixing device,

ii) designed to contain an aqueous monomer solution comprising at least one partially neutralized monoethylenically unsaturated monomer having a carboxylic acid group (α1);

f) a fourth container designed to contain one or more crosslinking agents (α3);

g) second mixing device:

The second mixing device

i) located downstream of the third and fourth containers,

ii) designed to mix the monomer solution with one or more crosslinking agents (α3);

h) Polymerization belt reactor:

The polymerization belt reactor is

i) located downstream of the second mixing device,

ii) designed to receive the aqueous monomer solution and at least one crosslinking agent (α3) during polymerization of the monomer in the aqueous monomer solution to obtain a polymer gel;

j) shredding device:

The crushing device

i) located downstream of the polymerization belt reactor,

ii) designed to break polymer gels;

k) belt dryer:

The belt dryer

i) located downstream of the crushing device,

ii) designed to dry polymer gels;

l) Crushing device:

The crushing device

i) located downstream of the belt dryer,

ii) designed to pulverize the dried polymer gel to obtain absorbent polymer particles;

m) Classification device:

The classification device

i) located downstream of the grinding device,

ii) Designed to classify pulverized absorbent polymer particles.

Preferred constituents or devices for producing the absorbent polymer particles according to the invention, or both, are designed according to the production method of the invention.

A solution to at least one of the aforementioned problems is provided by a method for producing absorbent polymer particles in a device according to the invention. Preferably, the method comprises manufacturing steps (i) to (xi) according to the invention.

A solution to at least one of the aforementioned problems is provided by the absorbent polymer particles obtainable by the production process of the present invention.

A solution to at least one of the aforementioned problems is provided by a composite material comprising the absorbent polymer particles according to the present invention.

In a preferred embodiment of the present invention, the composite material according to the present invention is a foam, a shaped article, a fiber, a foil, a film, a cable, a sealing material. (sealing material), liquid-absorbing hygiene article, carrier for plant and fungal growth-regulators, packaging material, soil additive and building material One, or a combination of two or more of these. A preferred cable is a blue water cable. Preferred liquid-absorbing hygiene products are one selected from the group consisting of diapers, tampons and sanitary napkins, or a combination of two or more thereof. Preferred diapers are infant diapers or incontinence adult diapers, or both.

A solution to at least one of the aforementioned problems is provided by a method for producing a composite material, in which the absorbent polymer particles according to the present invention, a substrate, and optionally an auxiliary material are brought into contact with each other.

A solution to at least one of the aforementioned problems is provided by the composite material obtainable by the method according to the invention.

The solution to at least one of the aforementioned problems is foam, shaped article, fiber, foil, film, cable, sealing material. , Liquid-absorbing hygiene articles, carriers for plant and fungal growth-regulators, packaging materials, soil additives, the invention for controlled release of active compounds or for use in building materials According to the use of absorbent polymer particles.

Polymerization belt reactor

A preferred belt of the polymerization belt reactor is a conveyor belt. As a conveyor belt usable in the method according to the present invention, any conveyor belt, which one skilled in the art considers to be usable as a support material capable of forming a polymer gel by loading and polymerizing the above-described aqueous monomer solution thereon, is Can be used.

Belts can be made of a variety of materials, but preferably these materials have good tensile strength and flexibility, good fatigue strength to repetitive bending stress, good deformability and chemical resistance to each reaction component under polymerization conditions. It must meet the same requirements. These requirements are usually not met with a single substance. Thus, multi-layered materials are commonly used as belts in the method of the present invention. Mechanical requirements can also be met by carcasses such as, for example, fabric inserts of natural and/or synthetic fibers or glass fibers or steel cords. Chemical resistance, for example, to covers made of halogenated polyolefins such as polyethylene, polypropylene, polyisobutylene, polyvinyl chloride or polytetrafluoroethylene, polyamides, natural or synthetic rubbers, polyester resins or epoxy resins. Can be achieved by A preferred cover material is silicone rubber.

The polymerization belt reactor is arranged near the guide rollers for the return run of the conveyor belt.

In order to complete the polymerization in the best possible space-time yield, according to the present invention, there is a support member extending upward, starting in the feed and metering system zone, on both sides of the horizontal support member near the upper run of the conveyor belt. , These upwardly extending support members intersect each other at a point where their longitudinal axes are below the upper run and support the conveyor belt so that the conveyor belt is in a suitable trough-shaped.

Another means of providing a trough-like structure is to place a weir element on a generally flat belt. In this case, one or more weir members are arranged longitudinally on both side edges of the belt. Two or more additional weir members are arranged transversely on the other longitudinal positions of the belt, with the trough extending longitudinally between these two positions. The height of the weir member determines the depth of the trough, and thus the amount of reactive components that can be fed into the trough. The longitudinal weir members must be designed to bend longitudinally with the belt in the turning section of the belt. Thus, the longitudinal weir members may be made of a flexible material, or may consist of a plurality of shorter longitudinal weir members disposed close to each other.

The trough-shaped structure of the polymerized belt can also be achieved by a combination of the transverse shape formation of the belt by the transversely oriented weir members and the support member, or by the belt longitudinal shape by the longitudinally oriented weir members and the support member. It can be achieved by a combination of formations.

Test method

The following test methods are used in the present invention. When the test method is omitted, the ISO test method published on the nearest date from the original filing date of the present invention is applied to the feature to be measured. If the ISO test method is not possible, the EDANA test method published on the nearest date from the original filing date of the present invention is applied. In the absence of clear measurement conditions, as standard ambient temperature and pressure (SATP), a temperature of 298.15 K (25° C., 77° F.) and an absolute pressure of 100 kPa (14.504 psi, 0.986 atm) is applied.

Moisture content

Moisture content is determined according to the Karl Fischer method.

Residual amount of monomer

The residual amount of monomer is measured according to the standard superabsorbent test method specified by EDANA. This test method is described in EDANA, Harmonized Test Methods Nonwovens and Related Industries, 2012 Edition as method number WSP 210.2.R3 (12) "residual monomer".

Example

The present invention is now described in more detail with reference to embodiments and drawings presented as examples, but is not limited thereto.

A) Preparation of partially neutralized acrylic acid monomer solution

0.4299 parts by weight of water (wt.-part) are mixed with 0.27 parts by weight of acrylic acid and 0.0001 parts by weight of mono methyl ether hydroquinone (MEHQ) in a suitable container. To this mixture, a 48% by weight aqueous sodium hydroxide solution was added in an amount of 0.2 parts by weight. A sodium-acrylate monomer solution having a degree of neutralization of 0.7 is prepared. For the preparation of this monomer solution, an aqueous solution of acrylic acid with a water content of 63% by weight and a temperature of 25°C are provided. A NaOH aqueous solution having a NaOH content of 30% by weight was cooled to the temperature shown in Table 1, and added to the acrylic acid aqueous solution contained in a mixer to achieve the degree of neutralization shown in Table 1, and the neutralization does not exceed 35°C. After 5 minutes of neutralization, GAA (glacial acrylic acid) is added until a degree of neutralization of 0.7 is reached without exceeding 35° C. during the neutralization reaction.

Optionally, the sodium-acrylate monomer solution is degassed with nitrogen.

B) polymerization of monomer solution

In a container, 1 part by weight of the monomer solution prepared in step A), 0.001 parts by weight of trimethylol propane triacrylate as a crosslinking agent, 0.001 parts by weight of sodium peroxodisulfate as a primary initiator component, and 2,2 parts by weight as a secondary initiator component. -Dimethoxy-1,2-diphenylethan-1-one (Ciba ^® Irgacure ^® 651, Ciba Specialty Chemicals Inc., Basel, Switzerland) 0.000034 parts by weight and acrylic acid particles (particle size less than 150 μm) up to 0.1 parts by weight By mixing with, a mixed solution is obtained.

To prepare a polymer gel, a further subsequent product, the absorbent polymer particles, a further subsequent product, the surface-crosslinked absorbent polymer particles, and a post-treated further subsequent product, the absorbent product, a sufficient amount of the mixed solution is subjected to further processing treatment. Carry out. Details of further processing treatments are provided below.

Then, as shown in Fig. 4, the mixed solution is loaded onto the belt of the conveyor belt reactor, and polymerization is initiated by UV irradiation. The conveyor belt has a length of 20 m or more. The conveyor belt takes the form of a trough to hold the solution on the belt before and during polymerization. The size of the conveyor belt and the conveying speed of the conveyor belt are selected in such a way that the poly-acrylic acid gel is produced at the downstream end of the belt. At the end of this process, an absorbent polymer gel is prepared. This polymer gel has a moisture content of about 52% by weight based on the total weight of the polymer gel.

C) crushing and drying of the polymer gel

The polymer gel is produced as polymer gel strands, which are discharged from a conveyor belt and crushed in three steps:

-Cut a rubber-like poly-acrylic acid gel into flat gel strips with a knife. The gel strip is 10-20 cm long, 10-20 mm high and 10-200 mm wide, then

-Cut the gel strip into pieces of gel 5-50 mm in length, 3-20 mm in height and 3-20 mm in width using a breaker,

-The gel pieces are extruded through a mixer equipped with a grinder, and the gel pieces are minced, thereby obtaining a gel piece having a length of 3-20 mm, a height of 3-20 mm and a width of 3-<20 mm.

The crushed gel is dried in a belt dryer at 180° C. so as to have a moisture content of 5% by weight based on the dried polymer gel. The belt of the belt dryer is equipped with an orifice, and hot air is injected into the polymer gel through a nozzle. Additionally, hot air flows from above the belt towards the gel.

D) Milling and classification

The dried polymer gel is pulverized in three steps. First, the dried polymer gel was passed through Herbold Granulator HGM 60/145 (HERBOLD Meckesheim GmbH) to obtain the dried polymer gel into pieces less than 7 mm in size, and then placed in a container for 2.5 hours to reduce the humidity of the polymer gel pieces. Make it the same. The dried polymer gel pieces are then pulverized in a roller mill of Bauermeister Type 350.1 x 1800 (3-stage crusher) (Bauermeister Zerkleinerungstechnik GmbH) to obtain absorbent polymer particles having a particle size of less than 1 mm.

The absorbent polymer particles are sieved through a tumbler sieve equipped with several screens. The mesh size of the screens varies from 20, 30, 40, 50, 60 to 100 U.S.-mesh. At least 50% by weight of the obtained absorbent polymer particles have a particle size in the range of 300 to 600 μm. Less than 5% by weight of the absorbent polymer particles of the examples according to the present invention have a particle size of less than 150 μm, and less than 5% by weight of the absorbent polymer particles of the examples according to the present invention have a particle size greater than 850 μm. The obtained water absorbing polymer particles are referred to as precursor I.

E) Silicon dioxide treatment

In the processing step, precursor I is mixed with about 0.01 parts by weight (±10%) of _{silicon dioxide (SiO 2} ), based on the total weight of _{precursor I + SiO 2, in a disk mixer.} Silicon dioxide is used in the form of ^{Sipernat ®} 22, available from Evonik Industries AG, Essen, Germany. When mixing precursor I with SiO ₂ , the precursor still maintains a temperature of 80°C-100°C, preferably 100°C. Precursor II is obtained.

F) surface crosslinking

As a further step, 1 part by weight of the precursor II is mixed with 0.003 parts by weight (+-10%) of the surface cross-linking agent based on the total weight of the mixture of the precursor II and the cross-linking agent. The surface crosslinking agent is composed of 19% by weight of water, 40% by weight of ethylene glycol diglycidyl ether, _{1% by weight of Na 2} SO ₃ , and 40% by weight of polyethylene glycol having a molecular weight of 400 g/mol, based on the total weight of the crosslinking agent. do. The components of the crosslinking agent are mixed in a line static mixer. The crosslinking agent is mixed in the ^{CoriMix ® CM 350 (Gebruder Lodige Mascheninenbau} GmbH, Paderborn, Germany) and the ring-layer mixer II precursors (ringlayer mixer). The mixture is heated to a temperature in the range of 130-160 °C. Then, the mixture is dried at a temperature in the range of 130-160° C. for 45 minutes in a Andritz Gouda Paddle Dryer, a Andritz Gouda Paddle Dryer, preferably a GPWD12W120 type dryer, of Andritz AG located in Graz, Austria. Surface-crosslinked absorbent polymer particles are obtained.

In a fluidized bed type cooling apparatus, the temperature of the surface-crosslinked absorbent polymer particles is cooled to below 60°C to obtain cooled surface-crosslinked absorbent polymer particles, which are referred to as precursor III.

G) Post-treatment

1 part by weight of precursor III is mixed with 0.005 parts by weight of Ag-zeolite. Then, the mixture is sieved. The sieve is selected to separate agglomerates of cooled surface-crosslinked absorbent polymer particles having a particle size greater than 850 μm. At least 50% by weight of the surface-crosslinked absorbent polymer particles have a particle size in the range of 300 to 600 μm. Less than 5% by weight of the surface-crosslinked absorbent polymer particles of the examples according to the present invention have a particle size of less than 150 μm, and less than 5% by weight of the surface-crosslinked absorbent polymer particles of the examples according to the present invention is 850 It has a particle size larger than μm. Post-treated surface-crosslinked absorbent polymer particles are obtained.

Example Neutralization NaOH _aq temperature Residual amount of monomer Comparative Example 1 0.7 25℃ --- Comparative Example 2 0.7 5℃ - Comparative Example 2 0.8 5℃ - Example 1 0.97 25℃ + Example 2 1.01 25℃ ++ Example 3 1.01 5℃ +++ Example 4 1.1 5℃ +++

Table 1: Monomer residual amount depending on the degree of neutralization and NaOH temperature.

Compare the parameter measurement results shown in Table 1 for Examples and Comparative Examples. In the order of the symbols shown below, the measurement results are better from left to right: ---, --, -, +, ++, +++.

From the above table, it becomes clear that the residual amount of the monomer of the surface-crosslinked water absorbent polymer particles can be significantly reduced by over-neutralization with a low-temperature NaOH aqueous solution.

1 is a flow chart showing steps 101 to 111 followed by steps 112 to 114 of a method 100 for producing absorbent polymer particles according to the present invention. The first step (i1) 112 comprises providing an acrylic acid primary fraction comprising mono methyl ether hydroquinone (MEHQ) or hydroquinone (HQ) or both. Further step (i2) 113 comprises the step of contacting the acrylic acid first fraction with sodium hydroxide (NaOH) in a first contact step, wherein a pH of 10 or more is achieved, and as a result, aqueous sodium-acrylate is contained. One first phase is obtained. Preferably, the first phase containing aqueous sodium-acrylate has a degree of neutralization of at least one. In step (i3) 114, the first acrylate phase is contacted with an additional fraction of acrylic acid in a second contact step to obtain a monomer solution. In step (i) 101, an aqueous monomer solution comprising at least one partially neutralized, monoethylenically unsaturated monomer having a carboxylic acid group (α1) is prepared. This monomer solution is prepared in step (i1) 112, step (i2) 114, and step (i3) 116. Preferably, the aqueous monomer solution is an aqueous solution of partially neutralized acrylic acid, and additionally contains a crosslinking agent. Preferably, the partially neutralized acrylic acid is provided as a solution in neutralized form by adding sodium hydroxide NaOH on the first acrylate containing MEHQ. After neutralization, in the first acrylate phase, about 96 mol-% of acrylic acid is acrylate. The aqueous monomer solution may also contain additional monomers such as acrylic acid or acrylamide. The monomer solution and at least one crosslinking agent (α3) are added to step (i) 101.

In the second step 102, the water absorbent polymer fine particles may be added to the aqueous monomer solution. Preferably, these particles comprise polyacrylic acid particles. In a third step 103, a polymerization initiator or one or more constituents of a polymerization initiator system comprising two or more constituents are added to the aqueous monomer solution. In the fourth step 104, nitrogen is bubbled through the aqueous monomer solution to lower the oxygen content of the aqueous monomer solution. In a fifth step 105, the monomer solution is loaded onto the belt 401 of the polymerization belt reactor 400. Belt 401 is a continuous conveyor belt. In the sixth step 106, the aqueous monomer solution is polymerized into a polymer gel. In a seventh step 107, the polymer gel is recovered from the belt 401. Then, the polymer gel is crushed to obtain polymer gel particles. In the eighth step 108, the polymer gel particles are loaded onto the belt of a belt dryer, and then dried at a temperature of about 120-150°C. The dried polymer gel particles are recovered in a belt dryer and then pulverized in a ninth step 109 to obtain absorbent polymer particles. In a tenth step 110, the absorbent polymer particles are classified to obtain absorbent polymer particles having an established particle size distribution. In the eleventh step 111, a crosslinking treatment is performed on the surface of the absorbent polymer particles.

2 is a flow chart showing steps 101 to 111 of a method 100 for producing absorbent polymer particles according to the present invention. The manufacturing method 100 shown in FIG. 2 is the same as the manufacturing method 100 of FIG. 1, but the third step 103 and the fourth step 104 overlap in time. While the polymerization initiator is added to the aqueous monomer solution, nitrogen bubbling is performed on the aqueous monomer solution to lower the oxygen content.

3 is a flow chart showing steps 101, 103 and 105-110 of the method 100 for producing absorbent polymer particles according to the present invention. The manufacturing method 100 shown in FIG. 3 is the same as the manufacturing method 100 of FIG. 1, but the second step 102, the fourth step 104, and the eleventh step 111 are the manufacturing method according to FIG. 3 ( Not included as part of 100).

4 is a schematic diagram of a basic setup of a polymerization belt reactor 400 according to the present invention. The polymerization belt reactor 400 includes a belt 401. Belt 401 is an endless conveyor belt. Belt 401 passes over two guide rollers 402 so that the upper run of belt 401 moves to the downstream region. The movement of the belt 401 to the downstream region of the upper run determines the direction of movement 403 indicated by arrows of the polymer gel (not shown) on the belt 401. The other arrow marks indicate the direction 404 opposite to the direction of movement of the polymer gel on the belt. Another arrow mark indicates the longitudinal direction 405 of the belt 401 and another arrow mark indicates the transverse direction 406 of the belt. The polymerization belt reactor 400 may further include other components not shown in the drawings, such as a support member, a supply and measurement system, an irradiation means, a cooling device, a heating device and a recovery system.

5 is a block diagram of an apparatus 500 for producing absorbent polymer particles according to the present invention. The arrow mark indicates the flow direction 512 in the manufacturing process of the absorbent polymer particles. The device 500 is, according to the invention, a cooling device 503, a cooling device 503 and a first container located downstream of the first container 501, the second container 502, the second container 502, respectively. (501) a first mixing device 504 located downstream, a third container 505, a fourth container 506, a third container 505 and a fourth container 506 located downstream of the first mixing device 504 ) A second mixing device 507 located downstream, a polymerization belt reactor 400 located next, a crushing device 508 located next, a belt dryer 509 located next, a crushing device located next ( 501) and a classification device 511 located thereafter.

100 Method according to the invention
101 step (i)
Step 102 (ii)
Step 103 (iii)
Step 104 (iv)
Step 105 (v)
Step 106 (vi)
Step 107 (vii)
Step 108 (viii)
Step 109 (ix)
110 steps (x)
Step 111 (xi)
Step 112 (i1)
Step 113 (i2)
Step 114 (i3)
400 polymerization reactor; Polymerization belt reactor
401 belt
402 guide roller
403 Direction of movement of the polymer gel on the belt
Reverse direction to the direction of movement of the polymer gel on the 404 belt
405 longitudinal
406 transverse direction
500 absorbent polymer particles manufacturing apparatus
501 first container
502 second container
503 cooling unit
504 first mixing device
505 third container
506 fourth container
507 second mixing device
508 shredding device
509 belt dryer
510 grinding device
511 classifier
512 manufacturing stream

Claims (24)

As a method for producing water-absorbent polymer particles (100),
(i) at least one partially neutralized, monoethylenically unsaturated monomer having a carboxylic acid group (α1); And preparing an aqueous monomer solution comprising at least one crosslinking agent (α3);
(ii) adding a polymerization initiator or a polymerization initiator system of one or more components to the aqueous monomer solution;
(iii) filling the polymerization reactor 400 with the aqueous monomer solution;
(iv) polymerizing a monomer in the aqueous monomer solution in the polymerization reactor 400 to obtain 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 obtain absorbent polymer particles; And
(viii) sizing the pulverized absorbent polymer particles
Including,
In the step (i), the step of preparing the aqueous monomer solution,
(i1) providing a first portion of acrylic acid;
(i2) contacting the first fraction of acrylic acid with hydroxide in the first contacting step to obtain a first acrylate phase,
The temperature difference between the temperature of the first fraction of acrylic acid and the hydroxide is 2 K or more,
The first acrylate phase has a pH of 10 or more,
The first acrylate phase has a degree of neutralization of 0.95 or more;
(i3) contacting the first acrylate phase with an additional fraction of acrylic acid in a second contacting step to obtain a monomer solution,
The additional fraction of acrylic acid has a moisture content less than that of the first acrylate phase,
The monomer solution has a pH lower than that of the first acrylate phase,
The monomer solution has a degree of neutralization in the range of 0.5-0.9,
The amount of acrylate and acrylic acid in the aqueous monomer solution is in the range of 30-50% by weight based on the total amount of the aqueous monomer solution.
Further comprising,
Method for producing water absorbent polymer particles. The method of claim 1,
Between steps (i) and (ii), adding fine particles of a water absorbent polymer to the aqueous monomer solution;
Between steps (ii) and (iii), lowering the oxygen content of the aqueous monomer solution;
Between steps (v) and (vi), comminuting the polymer gel; And
After step (viii), treating the surface of the pulverized and classified absorbent polymer particles.
Further comprising one or more of, the manufacturing method. The method of claim 1,
In the step (i2), the neutralization degree of the acrylate phase is higher than 1, the manufacturing method. The method of claim 1,
The production method, wherein the additional fraction of acrylic acid contains less than 5% by weight of moisture based on the total weight of the additional fraction of acrylic acid. The method of claim 1,
The manufacturing method, wherein the first fraction of acrylic acid contains 50% by weight or more of moisture based on the total weight of the first fraction of acrylic acid. The method of claim 1,
The pH of the monomer solution is in the range of 8-12, the preparation method. The method of claim 1,
The hydroxide is one selected from the group consisting of sodium hydroxide, potassium hydroxide and lithium hydroxide, or a mixture of two or more thereof. The method of claim 1,
The production method, wherein the oxygen gas content of the aqueous monomer solution is in the range of 3-15 ppmw (ppm by weight) based on the weight of the aqueous monomer solution. The method of claim 1,
The method of manufacturing, wherein the aqueous monomer solution is contacted with activated carbon in a further contact step. The method of claim 1,
At least the first contacting step or the secondary contacting step, or both steps are completed in a time in the range of 10-300 minutes. The method of claim 1,
At least the first contacting step or the second contacting step, or both steps are carried out at a temperature of the aqueous monomer solution of less than 40°C. The method of claim 1,
In the step (iv), the polymerization reactor 400 is a polymerization belt reactor 400, the manufacturing method. ◈ Claim 13 was abandoned upon payment of the set registration fee. The method of claim 1,
The manufacturing method, wherein the polymer gel discharged in the step (v) contains moisture in the range of 40 to 60% by weight based on the polymer gel. ◈ Claim 14 was abandoned upon payment of the set registration fee. The method of claim 1,
The polymer gel discharged in step (v) is a polymer gel sheet;
The method of manufacturing, wherein the polymer gel sheet has a thickness in the range of 10 to 200 mm. ◈ Claim 15 was abandoned upon payment of the set registration fee.◈ The method of claim 1,
The polymer gel discharged in step (v) is a polymer gel sheet;
The method of manufacturing, wherein the polymer gel sheet has a width in the range of 30 to 300 cm. The method of claim 1,
The production method, wherein the polymerization in step (iv) is carried out in the presence of a blowing agent. Apparatus 500 for producing absorbent polymer particles in production stream 512, comprising the following a) to m):
a) a first container 501, designed to contain acrylic acid;
b) a second vessel 502, designed to contain a metal hydroxide;
c) cooling device 503:
The cooling device 503,
i) located downstream of the second container 502,
ii) designed to cool metal hydroxides;
d) first mixing device 504:
The first mixing device 504
i) located downstream of the first container 501 and the cooling device 503,
ii) equipped with a cooler and propelled mixing mean;
e) third container 505:
The third container 505 is
i) located downstream of the first mixing device 504,
ii) designed to contain an aqueous monomer solution comprising at least one partially neutralized monoethylenically unsaturated monomer having a carboxylic acid group (α1);
f) a fourth container 506, designed to contain one or more crosslinking agents (α3);
g) second mixing device 507:
The second mixing device 507 is
i) located downstream of the third container 505 and the fourth container 506,
ii) designed to mix the monomer solution with one or more crosslinking agents (α3);
h) polymerization belt reactor 400:
The polymerization belt reactor 400 is
i) located downstream of the second mixing device 507,
ii) designed to obtain a polymer gel by receiving the aqueous monomer solution and at least one crosslinking agent (α3) upon monomer polymerization of the aqueous monomer solution;
j) crushing device 508:
The crushing device 508 is
i) located downstream of the polymerization belt reactor 400,
ii) designed to break polymer gels;
k) belt dryer 509:
The belt dryer 509 is
i) located downstream of the crushing device 508,
ii) designed to dry polymer gels;
l) Crushing device 510:
The crushing device 510 is
i) located downstream of the belt dryer 509,
ii) designed to pulverize the dried polymer gel to obtain absorbent polymer particles;
m) Classification device 511:
The classification device 511 is
i) located downstream of the pulverizing device 510,
ii) Designed to classify pulverized absorbent polymer particles. A method for producing absorbent polymer particles using an apparatus (500) according to claim 17. Absorbable polymer particles obtainable by the method according to any one of claims 1 to 16 or by the method according to claim 18. A composite material comprising the absorbent polymer particles according to claim 19. The method of claim 20,
Foam, shaped article, fiber, foil, film, cable, sealing material, liquid-absorbing hygiene article ), carriers for plant and fungal growth-regulators, packaging materials, soil additives and building materials. As a method for producing a composite material,
A method of manufacturing comprising contacting the absorbent polymer particles according to claim 19 and a substrate with each other. A composite material obtainable by the method according to claim 22. An article comprising the absorbent polymer particles according to claim 19, comprising:
The article may be a foam, a shaped article, a fiber, a foil, a film, a cable, a sealing material, a liquid-absorbing hygiene article. absorbing hygiene article), a carrier for plant and fungal growth-regulators, a packaging material, a soil additive, and a building material.

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