WO2018151453A1 - Method for producing super absorbent polymer - Google Patents

Abstract

The present invention relates to a method for producing a super absorbent polymer having excellent absorption properties, and more specifically relates to a production method of a super absorbent polymer wherein trouble with a process may be prevented by effectively suppressing the initiation of a polymerization reaction in a pipe prior to the introduction into a polymerization reactor.

Description

 [Name of invention]

 Manufacturing method of super absorbent polymer

[Art Field]

 Cross citation with related application (s)

 This application claims the benefit of priority based on Korean Patent Application No. 10-2017-0021051 dated February 16, 2017 and Korean Patent Application No. 10-2018-0014095 dated February 5, 2018. All content disclosed in the literature is included as part of this specification. The present invention relates to a method for producing a super absorbent polymer having excellent water absorption performance, and more particularly, to a method for producing a super absorbent polymer, which can effectively inhibit the polymerization reaction from starting in a pipe prior to the addition of the polymerization reactor. It is about.

Background Art

Superabsorbent polymer (Super Absorbent Polymer, SAP) is a synthetic polymer material with a can absorb about 500 to 1000 times the water of its own ^weight, features, developers every _{SAM (. Super Absorbency Material),} AG ( They are named differently, such as Absorbent Gel Material. Such super absorbent polymers have been put into practical use as physiological devices, and are currently used in sanitary products such as paper diapers for children, horticultural soil repair agents, civil engineering, building index materials, seedling sheets, freshness retainers in the food distribution field, and It is widely used as a material for steaming.

^Gajing, in many cases, these super-absorbent resins are widely used in the field of sanitary materials such as diapers and sanitary napkins. Within this sanitary material, the superabsorbent resin is generally included in the state spread in the peel. However, in recent years, efforts have been made to provide sanitary materials such as thinner diapers, and as a part thereof, the content of pulp is reduced, or more so-called pulpless diapers, in which no pil is used at all. Development is underway. As such, the content of pulp may be reduced, or In this case, relatively high absorbent polymers are included in a high proportion, and such superabsorbent polymer particles are inevitably included in the hygienic material in multiple layers. In order for the overall superabsorbent polymer particles contained in the multilayer to absorb the liquid such as urine more efficiently, the superabsorbent resin basically needs to exhibit high absorption performance and absorption rate. .

 Such superabsorbent water: paper is made by the method of drying, pulverizing and classifying a hydrogel polymer prepared by cross-polymerizing a monomer containing a salt thereof, or by surface crosslinking again. .

 In the crosslinking polymerization of the above-mentioned monomers, an appropriate kind of polymerization initiator or polymerization inhibitor is used, and the progress of polymerization reaction is controlled through the reaction conditions of reaction, and in particular, in order to activate the polymerization, present in the monomer mixture. It is known to remove dissolved oxygen before adding to the polymerization reactor.

 In addition, for the excellent physical properties of the final superabsorbent polymer, it is necessary to precisely control the initiation or suppression of reaction, which is very difficult due to the nature of the radical reaction, depending on the amount of polymerization initiator or polymerization inhibitor used, There is a problem that the physical properties of the water absorbent resin are lowered.

 In particular, in order to use a small amount of the polymerization initiator, the water-soluble ethylenically unsaturated carboxylic acid black has to raise the temperature of the neutralized neutralized liquid in order to obtain its salt, in which case the polymerization is initiated in a transfer line such as a pipe rather than a polymerization reactor. There is a disadvantage that continuous operation is difficult.

 Therefore, research is needed to efficiently control the initiation and suppression of the polymerization reaction while reducing the amount of the polymerization initiator and proceeding the polymerization at a high temperature.

[Detailed Description of the Invention]

 [Technical problem]

In the present invention, when the polymerization proceeds at a high temperature, it is possible to reduce the amount of polymerization and initiator to be used and to initiate and suppress the polymerization reaction, compared to conventional polymerization methods. It is to provide a method for producing a super absorbent polymer which can be efficiently controlled.

Technical Solution

 Seeing

 S O

 A) A gas containing oxygen in an aqueous monomer mixture comprising a water-soluble ethylenically unsaturated monomer having a neutralized acidic group, a crosslinking agent, and a polymerization inhibitor which inhibits polymerization of the water-soluble ethylenically unsaturated monomer in the presence of oxygen. Injecting;

B) transferring the aqueous monomer mixture injected with the gas containing oxygen to a polymerization reactor; ^·

 C) immediately before the aqueous monomer mixture into which the oxygen-containing gas is injected is introduced into the polymerization reactor. Removing oxygen from the aqueous monomer mixture; And

D) in the polymerization reactor, crosslinking polymerizing the water-soluble ethylenically unsaturated monomer to form a hydrogel polymer comprising the first crosslinked polymer,

 Provided is a method for producing a super absorbent polymer.

【Effects of the Invention】

 According to the superabsorbent polymer production method of the present invention, the polymerization can be carried out at a high temperature, and the amount of the polymerization initiator can be reduced in the polymerization process rather than the conventional polymerization method, and the initiation and suppression of the polymerization reaction can be efficiently controlled. .

[Form for implementation of invention]

 Method for producing a super absorbent polymer of the present invention,

A) at least a water-soluble ethylenically unsaturated monomer, a crosslinking agent, and the presence of oxygen for containing a polymerization inhibitor to inhibit the polymerization of the water-soluble ethylenically unsaturated monomer, the aqueous monomer common ^compounds, gas containing oxygen part having a neutralized acid Injecting;

B) transferring the aqueous monomer mixture injected with the gas containing oxygen to a polymerization reactor; C) removing oxygen from the aqueous monomer mixture immediately before the aqueous monomer mixture into which the gas containing oxygen is injected is introduced into a polymerization reactor; And

D) in the polymerization reactor, cross-polymerizing the water-soluble ethylenically unsaturated monomer to form a hydrogel polymer comprising the first crosslinked polymer. In the present invention, terms such as first and second are used to describe various components, which terms are used only for the purpose of distinguishing one component from other components.

 Also, the terminology used herein is for the purpose of describing example embodiments only and is not intended to be limiting of the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. As used herein, the terms "comprise", "comprise" or "have" are intended to indicate that there is a feature, number, step, component, or combination thereof, that is, one or more other features, It is to be understood that the present invention does not exclude the possibility of adding or presenting numbers, steps, components, or a combination thereof.

 As the invention allows for various changes and numerous modifications, particular embodiments will be illustrated and described in detail below. However, this is not intended to limit the present invention to a particular disclosed form, it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention. Hereinafter, the superabsorbent polymer production method of the present invention will be described in detail step by step. Method for producing a super absorbent polymer according to an aspect of the present invention,

A) Oxygen is added to an aqueous monomer mixture comprising a water-soluble ethylenically unsaturated monomer having a neutralized acidic group, a crosslinking agent, and a polymerization inhibitor that inhibits polymerization of the water-soluble ethylenically unsaturated monomer in the presence of oxygen. Injecting a gas comprising;

 B) transferring the aqueous monomer mixture injected with the gas containing oxygen to a polymerization reactor;

 C) removing oxygen from the aqueous monomer mixture immediately before the aqueous monomer mixture into which the gas containing oxygen is injected is introduced into a polymerization reactor; And

D) in the polymerization reactor, crosslinking polymerization of the water-soluble ethylenically unsaturated monomer to form a hydrogel polymer comprising the first crosslinked polymer. Step D) is a step of forming a hydrogel polymer, which is a step of crosslinking and polymerizing an aqueous monomer mixture comprising a water-soluble ethylenically unsaturated monomer having at least a part of which is neutralized with a crosslinking agent and a polymerization initiator.

 The water-soluble ethylenically unsaturated monomer constituting the first crosslinked polymer may be any monomer commonly used in the preparation of superabsorbent polymers. As a non-limiting example, the water-soluble ethylenically unsaturated monomer may be a compound represented by Formula 1:

 [Formula 1]

 R1-COOM1

 In Chemical Formula 1,

 R1 is an alkyl group having 2 to 5 carbon atoms containing an unsaturated bond,

M 1 is a hydrogen atom, a monovalent or divalent metal, an ammonium group or an organic amine salt. Preferably, the monomer may be at least one selected from the group consisting of acrylic acid, methacrylic acid, and monovalent metal salts, divalent metal salts, ammonium salts and organic amine salts of these acids. like this. When acrylic acid or its salt is used as the water-soluble ethylenically unsaturated monomer, it is advantageous to obtain a superabsorbent polymer having improved water absorption. In addition, the monomers include maleic anhydride, fumaric acid, crotonic acid, itaconic acid, 2-acryloylethane sulfonic acid, 2-methacryloylethanesulfonic acid, 2-

(Meth) acryloylpropanesulfonic acid or 2- (meth) acrylamide-2-methyl propane sulfonic acid, (meth) acrylamide, N-substituted (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2 -Hydroxypropyl (meth) acrylate, Mesopolyethylene glycol _. (Meth) acrylate, polyethylene glycol

(Meth) acrylate, (Ν, Ν) -dimethylaminoethyl (meth) acrylate, (Ν, Ν) -dimethylaminopropyl (meth) acrylamide and the like can be used.

 Here, the water-soluble ethylenically unsaturated monomer has an acidic group, at least a portion of the acidic group may be neutralized. Preferably, those which have been partially neutralized with an alkali substance such as sodium hydroxide, potassium hydroxide, ammonium hydroxide and the like can be used.

In this case, the neutralization degree of the monomer may be from about 40 to about 95 mol%, or from about 40 to about 80 mol%, or from about 45 to about 75 mole _^0/0. If the degree of neutralization is too high, polymerization of the monomer may be difficult to proceed due to precipitation of the neutralized monomer. On the contrary, if the degree of neutralization is too low, the absorbing power of the polymer may not be greatly reduced and may exhibit properties such as elastic rubber that is difficult to handle. However, the present invention is not necessarily limited to the above range, and the range of the degree of neutralization may vary depending on the physical properties of the final superabsorbent polymer.

In addition, the concentration of the aqueous monomer common compound The water-soluble ethyl butene unsaturated monomer may be appropriately adjusted in consideration of the polymerization time and banung conditions, preferably from 20 to 90% by weight, or 40 to 65 weight _^0/0 days Can you-. This concentration range may be advantageous in order to control the grinding efficiency during the grinding of the polymer to be described later, while eliminating the need to remove unreacted monomers after polymerization by using the gel effect phenomenon appearing in the polymerization reaction of a high concentration aqueous solution. However, when the concentration of the monomer is too low, the yield of the super absorbent polymer may be lowered. On the contrary, when the concentration of the monomer is too high, some of the monomers may precipitate or process problems may occur, such as when the pulverized efficiency of the polymerized hydrogel polymer is pulverized, and the physical properties of the super absorbent polymer may be reduced. Common ethylenically unsaturated monomers, such as acrylic acid and methacrylic acid, generally contain a polymerization inhibitor in order to prevent polymerization from occurring during storage or transportation. Hydroquinone ether-based compounds are commonly used, and specific examples thereof include monomethyl ether of hydroquinone (MEHQ). Polymerization inhibitors are ethylenically unsaturated monomers In contrast, from about lOppmw to about 300ppmw is used, preferably in a content of about 50ppmw to about 250ppmw, or about 150ppmw to about 220ppmw.

 Since such a polymerization inhibitor has a polymerization inhibitory effect of an ethylenically unsaturated monomer in the presence of oxygen, it is necessary to maintain a partial pressure of oxygen with a polymerization inhibitor at a constant or higher during the transport or storage of the ethylenically unsaturated monomer. It is necessary to remove the oxygen present in the monomer before starting the polymer polymerization. As the polymerization initiator, a thermal polymerization initiator or a photopolymerization initiator may be used depending on the polymerization method. However, even with the photopolymerization method, since a certain amount of heat is generated by ultraviolet irradiation or the like, and a certain amount of heat is generated in accordance with the progress of the polymerization reaction, which is an exothermic reaction, a thermal polymerization initiator is additionally used. Can be.

 Examples of the photopolymerization initiator include benzoin ether, dialkyl acetophenone, hydroxyl alkylketone, phenylglyoxylate, and benzyldimethyl ketal (for example, benzoin ether). One or more compounds selected from the group consisting of benzyl dimethyl ketal, acyl phosphine, and alpha-aminoketone can be used. As specific examples of acylphosphine, commercially available lucirin TPO, that is, 2,4,6-trimethyl-benzoyl-trimethyl phosphine oxide can be used. . A wider variety of photopolymerization initiators is disclosed in Reinhold Schwalm's book, "UV Coatings: Basics, Recent Developments and New Application (Elsevier 2007)", page 15. As the thermal polymerization initiator, at least one thermal polymerization initiator compound selected from the group consisting of persulfate initiator, azo initiator, hydrogen peroxide, and ascorbic acid may be used.

Specifically, as the persulfate-based initiator, sodium persulfate (Na2S208), potassium persulfate (Potassium persulfate; 2S208), ammonium persulfate (Ammonium) persulfate; (NH4) 2S208) etc. are mentioned.

 In addition, azo-based initiators include 2,2-azobis- (2-amidinopropane) dihydrochloride (2,2-azobis (2-amidinopropane) dihydrochloride), 2,2-azobis- (Ν, Ν-dimethylene) isobutyramidine dihydrochloride (2,2-azobis- (N, N-dimethylene) isobutyramidine dihydrochloride), 2-

(Carbamoylazo) isobutyronitrile ( ^2- (carbamoylazo) isobutylonitril), 2,2-azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride (2,2-azobis [ 2- (2-imidazolin-2-yl) propane] dihydrochloride), 4,4-azobis- (4-cyanovaleric acid) (4,4-azobis- (4-cyanovaleric acid)) Can be.

 For a more varied thermal polymerization initiator, see Odian, "Principle of

Polymerization (Wiley, 1981) ", which may be referred to. The polymerization initiator may be added at a concentration of about 0.001 to about 1 part by weight based on 100 parts by weight of the monomer. If the concentration of the polymerization initiator is too low, the polymerization rate may be slow and a large amount of residual monomer may be extracted in the final product, and if the concentration of the polymerization initiator is too high, the polymer chain forming the network may be shortened. In particular, the thermal polymerization initiator may be present in an amount of about 0.01 to about 0.5 parts by weight based on 100 parts by weight of the ethylenically unsaturated monomer in the present invention. The amount of the thermal polymerization initiator to be used may be The physical properties of the base resin may be affected, and in particular, the water-soluble component content of the base resin may be increased. In addition, when the thermal polymerization initiator is used too little, the efficiency of the hydrogel polymerization may be lowered, and various physical properties of the superabsorbent polymer to be finally produced may be lowered. Is about 0.05 to about 100 parts by weight of the ethylenically unsaturated monomer 0.5 parts by weight can be used. The above-mentioned polymerization initiators may be used in a form initially contained in the aqueous monomer mixture of step A), including a water-soluble ethylenically unsaturated monomer, a crosslinking agent, and a polymerization inhibitor, to remove oxygen from the aqueous monomer mixture. C) may be used in the form of a separate input just before or immediately after the step.

In particular, in the case of using the above-described thermal polymerization initiator, in consideration of the interaction with oxygen, it may be preferable to separate the oxygen from the aqueous monomer mixture in the step C), and then separately added before the step D). have. In addition, the polymerization reaction can be carried out in the presence of a crosslinking agent. The crosslinking agent may be any compound as long as it allows the introduction of a crosslink in the polymerization of the water-soluble ethylenically unsaturated monomer. As a non-limiting example, the crosslinking agent is Ν, Ν'- methylenebisacrylamide, trimethyl propane tri (meth) acrylate, ethylene glycol di (meth) acrylate, polyethylene glycol (meth) acrylate, propylene glycol di (meth) Acrylate, polypropylene glycol (meth) acrylate, butanediol di (meth) acrylate, butylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate: nucleic acid diol di (meth) acrylic Rate, triethylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, dipentaerythritol pentaacrylate, glycerin tri (meth) acrylate, penta Erys tetraacrylate, triarylamine, ethylene glycol diglycidyl ether, propylene Multifunctional crosslinking agents such as glycols, glycerin, or ethylene carbonate may be used alone or in combination of two or more, but are not limited thereto. Preferably, two polyethyleneglycol diacrylates with different molecular weights are used. Such a crosslinking agent may be added in an amount of about 0.001 to about 1 part by weight based on 100 parts by weight of the water-soluble ethylenically unsaturated monomer. That is, the crosslinking agent is too small If included, the absorption rate of the resin may be lowered and the gel strength may be weakened, which is undesirable. On the contrary, when the crosslinking agent is used too much, the absorbency of the superabsorbent polymer is lowered, which may be undesirable as an absorber. In addition, the reaction material in such a polymerization reaction may be prepared in the form of an aqueous monomer mixture in which raw materials such as the monomers described above are dissolved in a solvent. In this case, any solvent that can be used may be used without limitation as long as it can dissolve the above-described raw materials. For example, as the solvent, water, ethanol, ethylene glycol, diethylene glycol, triethylene glycol, 1,4-butanediol, propylene glycol ethylene glycol monobutyl ether, propylene glycol monomethyl ether propylene glycol monomethyl ether acetate methylethyl Ketones, acetone, methyl amyl ketone cyclonucanonone, cyclopentanone, diethylene glycol monomethyl ether diethylene glycol ethyl ether, toluene, xylene, butyrolactone, carbitle, methyl cellosolve acetate, Ν, Ν -Dimethylacetic acid, or mixtures thereof, and the like can be used. In addition, the formation of the hydrogel polymer through polymerization of the aqueous monomer mixture may be performed by a conventional thermal polymerization method. For example, a ^"can take place in a half unggi with stirring axis, such as a kneader (kneader). In this case, the aqueous monomer mixture may be introduced into a reactor such as a kneader equipped with a stirring shaft, and hot water may be supplied thereto, or the reactor may be heated to thermally polymerize to obtain a hydrogel polymer. At this time, the hydrous gel phase polymer discharged to the reactor outlet according to the form of the stirring shaft provided in the reaction vessel may be obtained from particles of several millimeters to several centimeters. Specifically, the hydrous gel polymer obtained may be obtained in various forms depending on the concentration and the injection speed of the monomer in the injected aqueous monomer mixture, and the hydrogel polymer having a particle size of about 2 to about 50 mm is usually obtained. Can be. On the other hand, as described above, in order to improve the physical properties of the base resin and the final superabsorbent polymer to be produced, it is preferable to use a relatively small amount of polymerization initiator in the polymerization reaction, in this case, to improve the polymerization efficiency To this end, after at least a portion of the acidic groups contained in the water-soluble ethylenically unsaturated monomer is thickened, the polymerization reaction is added to the polymerization reactor in a state where the temperature of the aqueous monomer mixture further comprising a thickening liquid or various additives is added thereto. .

 For example, the aqueous monomer mixture may be transferred and introduced into the polymerization reactor via a transfer line at a temperature condition of about 40 to about 90 ° C.

 However, when the temperature of the neutralizing liquid is added to the polymerization reactor in order to improve the efficiency of the polymerization reaction, the polymerization reaction may be started early in the transfer line, which may cause process troubles such as clogging of the pipe. . Solubility of water, such as oxygen, in water is very sensitive to silver and pressure, as well as the nature of the gas molecules themselves, such as polarity.

 Specifically, in a typical atmospheric composition, oxygen accounts for about 21%, and under this atmospheric composition, at about 20 ° C, about 1 atmosphere, the saturated dissolved oxygen amount per liter of distilled water is about 8.84 mg, but about 40 ° C At 1 atm, the saturated dissolved oxygen content per liter of distilled water is about 6.59 mg. In addition, in the process of producing a super absorbent polymer as in the present application, after neutralizing at least a part of the acid groups included in the above-described water-soluble ethylenically unsaturated monomers, the neutralizing liquid or various additives is further included. It becomes an aqueous monomer mixture condition, and by interaction with other components dissolved in water, the solubility of oxygen itself is generally lower than the above range.

 For example, in the case of the aqueous monomer mixture, the saturated dissolved oxygen amount per 1 liter of the aqueous monomer mixture is about 7.5 to about 8 mg at about 20 ° C, about 1 atmosphere, and about 40 ° C, at 1 atmosphere, The amount of saturated dissolved oxygen for 1 liter of the monomer mixture is greatly lowered to about 3.0 to about 4 mg.

 However, under these conditions, the amount of oxygen in the aqueous monomer mixture is not sufficient, and it is very difficult for the polymerization inhibitor to function properly, and thus the polymerization reaction can be started early.

Accordingly, in the present invention, a gas containing oxygen is optionally injected into a thickening liquid containing the polymerization inhibitor described above, or an aqueous monomer mixture containing such a neutralizing liquid and various additives, and an aqueous monomer mixture in which a gas containing oxygen is injected. To a polymerization reactor. In this case, the injected oxygen By increasing the activity of the polymerization inhibitor may serve to control the polymerization reaction does not occur during the transfer process.

 Specifically, in the step A), the dissolved oxygen ratio represented by Equation 1 below is greater than about 1.0, about 2.5 or less, preferably about 1.5 or more and 2.5 or less, more preferably, about 1.7 or more Oxygen or a gas containing oxygen (atmosphere, etc.) may be injected to satisfy the range of 2.3 or less.

 [Equation 1]

 D02 / D01

 In Equation 1,

 D01 is the amount of dissolved oxygen (mg / L) in the aqueous monomer mixture, measured immediately before injecting the gas containing oxygen into the aqueous monomer mixture,

 D02 is the amount of dissolved oxygen (mg / L) in the aqueous monomer mixture measured immediately after injecting the gas containing oxygen into the aqueous monomer mixture. .

As described above, in the present invention, the atmosphere containing oxygen or oxygen is injected into the neutralizing liquid or the aqueous monomer mixture containing the neutralizing liquid and various additives, thereby polymerizing the aqueous monomer mixture having a large increase in the amount of dissolved oxygen. By transferring to the reactor, it is possible to effectively inhibit the progress of the polymerization reaction in the transfer line, it is possible to prevent the process ^shock , such as clogging of the pipe. However, as described above, when the oxygen-injected aqueous monomer mixture is directly introduced into the polymerization reactor, a polymerization reaction proceeding in the polymerization reactor is suppressed and a reaction efficiency may decrease.

 Therefore, it is necessary to remove oxygen from the aqueous monomer mixture immediately before the aqueous monomer mixture into which the oxygen-containing gas is injected is introduced into the polymerization reactor, and, for example, inert to the aqueous monomer mixture into which the oxygen is injected. Gas can be injected to remove oxygen.

The inert gas means a gas which is not reactive to the monomer and various additive components contained in the above-mentioned aqueous monomer mixture, and specifically ,. Group 18 gases such as helium (He), neon (Ne), argon (Ar), carbon monoxide (CO), Carbon dioxide (C0 ₂ ), nitrogen (N ₂ ) and the like may be included, and one or more of these may be used in combination.

 The inert gas may be injected in the same direction or in the opposite direction as the aqueous monomer mixture to remove oxygen, mixed with the aqueous monomer mixture by a valve, a mixer, or a bubble column, and then discharged. Oxygen contained in the mixture can be removed.

 The inert gas is preferably injected in the same direction as the aqueous monomer mixture, and may be introduced together with the polymerization reactor. Through this process, oxygen dissolved in the aqueous monomer mixture can be effectively removed.

 Specifically, the dissolved oxygen ratio represented by Equation 2 may be about 0.01 or more, or about 0.05 or more, and about 0.2 or less, preferably about 15 or less.

 Then, the dissolved oxygen ratio represented by the following equation (3) is about οι to about

0.5, preferably about 0.1 or more, or about 0.2 or more, about 0.5 or less, or about 0.4 or less, preferably about 0.3 or less.

 Equation 2-D03 / D02

 [Equation 3]

 D03 / D01

 In Equations 2 and 3, D01 and D02 are as defined in Equation 1,

D03 is the amount of dissolved oxygen in the aqueous monomer mixture (mg / L) measured immediately after removing oxygen from the aqueous monomer mixture. On the other hand, the conventional water content of the hydrogel polymer obtained by the above method may be about 40 to about 80% by weight. On the other hand, throughout the present specification, "water content" means the content of water to account for the total weight of the hydrogel polymer minus the weight of the polymer in the dry state. Specifically, In the process of raising the temperature of the polymer through infrared heating and drying, it is defined as a calculated value by measuring the weight loss due to evaporation of water in the polymer. At this time, the drying condition is to increase the temperature up to about 180 ° C from phase silver and maintained at 180 ° C. The total drying time is set to about 20 minutes, including about 5 minutes of the temperature rise step, the moisture content is measured. Step E) is a step of drying, pulverizing and classifying the hydrogel polymer prepared by the above-described method to form a base resin powder, wherein the base resin powder and the super absorbent polymer obtained therefrom have a particle diameter of about 150 to about 850. Manufactured and provided to have suitable.

 More specifically, at least about 95% by weight or more of the base resin powder and the superabsorbent polymer obtained therefrom have a particle size of about 150 to about 850 mm 3, and the fine powder having a particle size of less than about 150 is less than about 3% by weight. Can be. As such, as the particle size distribution of the base resin powder and the super absorbent polymer is adjusted to a preferred range, the final superabsorbent polymer prepared may express the above-described physical properties better. On the other hand, it will be described in more detail with respect to the progress of the drying, grinding and classification as follows.

 ―

First, in drying the hydrogel polymer, coarsely pulverizing before drying in order to increase the efficiency of the drying step, if necessary. At this time, the pulverizer used is not limited in configuration, but specifically, a vertical pulverizer, a turbo cutter, a turbo grinder, a rotary cutter mill, a cutting machine Includes any one selected from the group of grinding machines consisting of cutter mills, disc mills, shred crushers, crushers, choppers and disc cutters Although it is possible, it is not limited to the above-mentioned example. At this time, in the coarse grinding step, the particle diameter of the hydrogel filler is about 2 mm to about 10 mm. It can be ground as much as possible. Grinding to a particle diameter of less than about 2 mm is not technically easy due to the high water content of the hydrogel polymer, and may also cause agglomeration between the crushed particles. On the other hand, when the particle size is pulverized more than about 10mm, the effect of increasing the efficiency of the subsequent drying step may be insignificant. ^The drying is carried out for the hydrogel polymer immediately after polymerization as described above or not subjected to the coarse grinding step. At this time, the drying temperature of the drying step may be about 50 to about 250 ^o C. If the drying temperature is less than about 50 ^o C, the drying time may be too long and the physical properties of the superabsorbent polymer to be finally formed may be lowered. If the drying temperature exceeds about 250 ^o C, only the polymer surface is dried excessively, Fine powder may be generated in a subsequent grinding step, and there is a fear that the physical properties of the superabsorbent polymer to be finally formed are reduced. More preferably, the drying may proceed at a temperature of about 150 to about 200 ° C, more preferably at a temperature of about 160 to about 190 ° C. On the other hand, in the case of drying time may be performed for about 20 minutes to about 15 hours in consideration of process efficiency, but is not limited thereto. As long as it is conventionally used in the drying process, can be selected and used without limitation of the configuration. Specifically, the drying step may be performed by a method such as hot air supply, infrared irradiation, microwave irradiation, or ultraviolet irradiation. The water content of the polymer after such a drying step may be about 0.05 to about 10 weight ⁰ /. Next, the step of pulverizing the dried polymer obtained through this drying step is carried out. The polymer powder obtained after the grinding step may have a particle diameter of about 150 to about 850. The grinder used to grind to such a particle size is specifically, a ball mill, a pin mill, a hammer mill, a screw mill, a mill, a roll mill, a disk. A mill or a jog mill may be used, but is not limited to the example described above. In addition, in order to manage the physical properties of the super absorbent polymer powder to be finalized after such a grinding step, a separate process of classifying the polymer powder obtained after grinding according to the particle diameter may be performed. Preferably, the polymer having a particle size of about 150 to about 850 may be classified and commercialized through a surface crosslinking reaction step to be described later only for the polymer powder having such a particle size. The step F) is a step of crosslinking the surface of the base resin prepared in the step E), and in the presence of a surface crosslinking solution, heat treating the base resin powder to crosslink the surface to form superabsorbent resin particles. The surface crosslinking solution is ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerol polyglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, ethylene glycol, Diethylene glycol, propylene glycol, triethylene glycol, tetraethylene glycol, propane diol, dipropylene glycol, ^' polypropylene glycol, glycerin, polyglycerol, butanediol, heptanediol, nucleic acid die, trimethylolpropane, pentaerythritol , Sorbbi, may include one or more surface crosslinking agents selected from the group consisting of calcium hydroxide, magnesium hydroxide, aluminum hydroxide, iron hydroxide, calcium chloride, magnesium chloride, aluminum chloride, and iron chloride. Preferably, ethylene glycol diglycidyl ether can be used. At this time, it is preferable to use the said surface crosslinking agent about 1 weight part or less with respect to 100 weight part of said base resins. Here, the amount of the surface crosslinking agent used means the total amount thereof when two or more kinds of the surface crosslinking agents are used. When the amount of the surface crosslinking agent exceeds about 1 part by weight, excessive surface crosslinking may proceed to deteriorate various physical properties of the superabsorbent polymer, in particular, dryness. The surface crosslinking agent may be used in an amount of about 0. 2 parts by weight, about 0.02 parts by weight, about 03 parts by weight, about 0.04 parts by weight, or about 0.05 parts by weight or more based on 100 parts by weight of the base resin. desirable. In addition, the surface crosslinking solution is water, methanol, ethanol, isopropyl alcohol ethylene glycol, diethylene glycol, triethylene glycol, 1,4-butanediol, propylene glycol ethylene glycol monobutyl ether, propylene glycol monomethyl ether propylene glycol monomethyl Ether acetate, methyl ethyl ketone, acetone, methyl amyl ketone cyclonucleanone, cyclopentanone, diethylene glycol monomethyl ether diethylene glycol ethyl ether, toluene, xylene, butyrolactone, carbyl, methyl cellosolve acetate And Ν, Ν-dimethylacetamide may further comprise at least one solvent selected from the group consisting of. Preferably, water is included. The solvent may be used in about 0.5 to about 10 parts by weight based on 100 parts by weight of the base resin powder. In addition, the surface crosslinking liquid may further include aluminum sulfate. The aluminum sulfate may be included in about 0.02 to about 1.5 parts by weight based on 100 parts by weight of the base resin powder. In addition, the surface crosslinking liquid may further include an inorganic filler. The inorganic filler may include silica, aluminum oxide, or silicate. The inorganic filler may be included in an amount of about 0.01 to about 0.5 parts by weight based on 100 parts by weight of the base resin powder. In addition, the surface crosslinking liquid may further include a thickener. Thus further crosslinking the surface of the base resin powder in the presence of a thickener can minimize the decrease in physical properties after grinding. Specifically, the thickener may be used one or more selected from polysaccharides and hydroxy containing polymers. As the polysaccharide, gum thickener and cellulose thickener may be used. Examples of the gum-based thickener, xanthan gum (xanthan gum), Arabic gum (arabic gum), karaya gums (karaya gum), bit ⁱ raegeo kaenseu gum (tragacanth gum), Gatti gum (ghatti gum), guar Guar gum, locust bean gum, silylium seed gum, and the like. Specific examples of the cellulose-based thickeners include hydroxypropylmethylcellulose, carboxy, and the like. Methyl cellulose, Methylcellose, hydroxymethylcellose, hydroxyethylcellose, hydroxypropylcellose ', hydroxyethylmethylcellose, hydroxymethylpropylcellose, hydroxyethylhydroxypropylcell Rhose, ethyl hydroxyethyl cellulose, methyl hydroxypropyl cellulose, etc. are mentioned. On the other hand, specific examples of the hydroxy-containing polymers include polyethylene glycol and polyvinyl alcohol. On the other hand, in order to perform the surface crosslinking, the surface crosslinking solution and the base resin are put into a reaction tank and mixed, a method of spraying a surface crosslinking solution onto the base resin, and the base resin and the surface crosslinking to a mixer which is continuously operated. The method of supplying and mixing a liquid continuously, etc. can be used. In addition, the surface crosslinking may be performed at a temperature of about 100 to about 250 ^° C., and may be continuously performed after the drying and grinding step of proceeding at a relatively high temperature. At this time. The surface crosslinking reaction may proceed for about 1 to about 120 minutes, or about 1 to about 100 minutes, or about 10 to about 60 minutes. That is, in order to induce a minimum surface crosslinking reaction, the polymer particles may be damaged during excessive reaction and thus the physical properties may be deteriorated. As described above, it is possible to have a superabsorbent excellent absorption performance produced by the production method of the present invention. Specifically, the super-absorbent resin according to the present invention, centrifugation beam SAT (CRC) for 30 minutes for saline solution (0.9 weight _^0/0 aqueous sodium chloride solution) is not less than 30g / g. The measuring method of the centrifugal water holding capacity is specified in the following Examples. Preferably, the centrifugal water holding capacity is 3 (). 5g / g or more, or 31g / g or more. In addition, the higher the value, the better the centrifugal water holding capacity, and there is no limit of a practical upper limit. 35 g / g or less, 34 g / g or less, or 33 g / g or less. Further, preferably, the super absorbent polymer according to the present invention has a pressurized absorption capacity (0.7 AUP) of 1 g or more for 1 hour under 0.7 psi with respect to physiological saline solution (0.9 weight ⁰ /. Sodium chloride aqueous solution). The measuring method of the said pressure absorbing power is specified more in the following example. Preferably, the 0.7 AUP is at least 20 g / g, or at least 8.0 g / g. Further, the higher the pressure absorbing capacity is, the better the value is, and there is no limit to the practical upper limit. In addition, the superabsorbent polymer according to the present invention has a proportion of particles having a particle diameter of about 150 to about 850 / ΛΠ of about 90% or more. Hereinafter, the operation and effects of the invention will be described in more detail with reference to specific examples of the invention. _However,. These embodiments are presented by way of example only, and the scope of the invention is not defined thereby.

<Example>

While stirring with a 20 L SUS container with temperature control, 4500 g of acrylic acid having a monomethylether hydroquinone content of 100 ppm and 10147 NaOH diluted with 24% were slowly introduced. When the temperature of the neutralizing solution reached 45 ° C. 5 g of methylene bisacrylamide (MAAA) was dissolved in 500 g of acrylic acid, and the stirring was continued. Here an air diffuser (air iser diff) to the container floor, and input to a gas containing oxygen at a rate of 50L per minute, the mixture was stirred for 30 minutes ^i.

In-line Homogenizer (Megatron MT 3000, 4 inlets and 1 outlet) is installed at the upper inlet of single-axis kneader (listed by LIST) that can continuously inject and discharge. , 0.2% ascorbic acid 30g per minute and 0.7% hydrogen peroxide solution 30g per minute, respectively, injecting nitrogen gas into another inlet at a rate of 20L per minute, and rotating the homogenizer at 6,000rpm per minute to mix the solution and gas. The mixed solution and gas inside the homogenizer were introduced into the kneader through the outlet. After adding the neutralizing solution to the kneader, a gel was formed inside the kneader and foaming occurred. The gel was subdivided and discharged out of the kneader by the force given from the rotating body inside, and the size of the gel was 5 mm to 50 mm. This was chopped using a Meat Chopper to further refine the average gel size to 5 mm.

 It was dried in an oven capable of transferring wind direction up and down. The hot air at 185 ° C. was heated uniformly by flowing from downward to upward for 15 minutes and upward from downward for 5 minutes. After drying, the moisture content of the dried body was adjusted to be 2% or less. The resultant was pulverized with a grinder and then classified for 10 minutes using standard meshes (# 20, # 30, # 50, # 100) and Sieve Shaker to obtain a polymer having a particle size of 150 to 850. In this way, a base resin powder was obtained. .

 Then, 100 parts by weight of the prepared base resin, surface crosslinking liquid (4 parts by weight of water, 3 parts by weight of methanol, 0.15 parts by weight of ethylene glycol _ diglycidyl ether (EX-810), 0.3 parts by weight of propylene glycol (PG) After the addition, evenly mixed with aluminum sulfate 18 hydrate (0.15 parts by weight of aluminum sulfate, 0.1 parts by weight of aluminum silica (Aerosil 200)), the surface cross-linking reaction was carried out for 30 minutes at 140 ° C. The reaction was completed using a standard network to obtain 150 urn to 850 m particles. The process conditions of Examples and Comparative Examples are summarized in Table 1 below.

 (The amount of initiator is 100 ascorbic acid and hydrogen peroxide solution described in the above example, and the relative amount is described.)

 Table 1

DMS 배출구에 중합물 발생

Polymerization at DMS outlet

 3 minutes after the start of the transfer, Comparative Example 2 0 40 100 Polymer at the outlet of the atmospheric DMS

 2 minutes after the start of the transfer, Comparative Example 3 Polymer at 200 60 50 unloaded DMS outlet.

 Occur

 DMS comparative example 4 200 80 20

Polymerization at the Outlet In Examples 1 to 3, immediately before the gas injection with oxygen (D01), immediately after the gas injection with oxygen (D02), immediately after the oxygen was removed by nitrogen injection (D03), the amount of dissolved oxygen was measured and It summarized in Table 2. ^'

 TABLE 2

Prepared in the Examples and Comparative Examples

 Physical properties are summarized in Table 3 below. .

실시예 2 38 34 24

Example 2 38 34 24

 Example 3 37 33 26

 Comparative Example 1 40 34 22

 Comparative Example 2 37 33 24

 Comparative Example 3 38 34 24

 Comparative Example 4 _ _

Referring to Table 1, in the present embodiment, it can be confirmed that no problem occurs in the DMS outlet by the injection of oxygen, and no trouble occurs in the continuous process, whereas in the comparative example, after the start of the transfer In the DMS outlet, a polymer is produced, and it can be clearly confirmed that a process trouble occurs.

 In particular, in the case of Comparative Example 4, immediately after the start of the transfer, there was a problem in the DMS outlet, the process was not able to proceed at all, it was confirmed that the water-absorbent resin production by the continuous process is impossible

 On the other hand, it was confirmed that the base resin and the super absorbent polymer produced in accordance with the Examples of the present invention had both good water retention capacity and water absorption under pressure.

Claims

[Range of request]  [Claim 1]  A) A gas containing oxygen in an aqueous monomer mixture comprising a water-soluble ethylenically unsaturated monomer having a neutralized acidic group, a crosslinking agent, and a polymerization inhibitor which inhibits polymerization of the water-soluble ethylenically unsaturated monomer in the presence of oxygen. Injecting;  B) transferring the aqueous monomer mixture injected with the gas containing oxygen to a polymerization reactor;  C) removing oxygen from the aqueous monomer mixture immediately before the aqueous monomer mixture into which the gas containing oxygen is injected is introduced into a polymerization reactor; And D) crosslinking polymerization of the water-soluble ethylenically unsaturated monomer in the polymerization reactor to form a hydrogel polymer comprising the first crosslinked polymer,  Method for producing a super absorbent polymer. [Claim 2].  The method of claim 1,  E) drying, grinding and classifying the hydrogel polymer to form a base resin powder; And.  F) heat treating the base resin powder in the presence of a surface crosslinking liquid to crosslink the surface, and to form superabsorbent polymer particles; Method for producing a super absorbent polymer. ^' [Claim 3]  The method of claim 1, The aqueous monomer mixture is transferred to a polymerization reactor at a temperature of 40 ^° C to 90 ^° C, and introduced, a method of producing a high hop water resin. [Claim 4] The method of claim 1, The step A), the dissolved oxygen ratio represented by the following formula 1 is greater than 1.0, proceeds to be 2.5 or less.  Manufacturing method of super absorbent polymer:  [Equation 1]  D02 / D01  In Equation 1,  D01 is the amount of dissolved oxygen in the aqueous monomer mixture (mg / L) measured immediately before injecting the gas containing oxygen into the aqueous monomer mixture,  D02 is the amount of dissolved oxygen in the aqueous monomer mixture (mg / L) measured immediately after injecting the gas containing oxygen into the aqueous monomer mixture. [Claim 5]  The method of claim 1,  In the step C), injecting an inert gas into the aqueous monomer mixture to remove oxygen, the method of producing a super absorbent polymer. [Claim 6]  The method of claim 1,  Step C) is performed so that the dissolved oxygen ratio represented by Equation 2 is 0.01 to 0.5,  Manufacturing method of super absorbent polymer:  [Equation 2]  D03 / D02  In Equation 2,  D02 is the amount of dissolved oxygen in the aqueous monomer mixture (mg / L) measured immediately after injecting a gas containing oxygen into the aqueous monomer mixture,  D03 is the amount of dissolved oxygen in the aqueous monomer mixture (mg / L) measured immediately after removing oxygen from the aqueous monomer mixture. [Claim 7] The method of claim 1,  After the step C) and before the step D), further comprising the step of adding a thermal polymerization initiator to the aqueous monomer mixture,  Method for producing a super absorbent polymer. [Claim 8]  The method of claim 1,  The polymerization inhibitor is a method of producing a super absorbent polymer, wherein at least a part of lOppmw to 300ppmw based on 100 parts by weight of the water-soluble ethylenically unsaturated monomer having a neutralized acid group. [Claim 9]  The method of claim 1,  The superabsorbent polymer has a centrifugal water retention capacity (CRC) of 30 g / g or more and a pressurized hop water capacity (AUP, 0.7 psi) of 15 g / g or more.