WO2020149651A1 - Preparation method of super absorbent polymer - Google Patents

Abstract

A preparation method of a super absorbent polymer, according to the present invention, wherein: in a process of grinding and classifying, following the formation and drying of a hydrogel polymer, the amount of fines generated which are 150 µm or smaller may be minimized by blocking particles having a specific size or smaller from also being included in the grinding; the particle size of a final product may be easily adjusted according to a target particle diameter setting of a classifier; and a super absorbent polymer exhibiting physical properties equal to or greater than those of conventional super absorbent polymers may be prepared.

Description

Manufacturing method of super absorbent polymer

Cross-citation with relevant application(s)

This application claims the benefit of priority based on Korean Patent Application No. 10-2019-0005757 on January 16, 2019 and Korean Patent Application No. 10-2020-0005490 on January 15, 2020. All content disclosed in the literature is incorporated as part of this specification.

The present invention relates to a method for producing a super absorbent polymer capable of suppressing and reducing the generation of fine powder.

Super Absorbent Polymer (SAP) is a synthetic polymer material that has the ability to absorb about 500 to 1,000 times its own weight.Sam (Super Absorbency Material), AGM (Absorbent Gel) for each developer Material). The superabsorbent resin as described above began to be put into practical use as a sanitary tool, and now, in addition to sanitary products such as paper diapers for children, soil repair agents for horticulture, civil engineering, construction water supply materials, nursery sheets, freshness retention agents in the food distribution field, and It is widely used as a material for poultice. In most cases, these superabsorbent polymers are widely used in the field of hygiene materials such as diapers and sanitary napkins.

The superabsorbent polymer is prepared through a process of preparing a hydrogel polymer using a water-soluble ethylenically unsaturated monomer, followed by drying and pulverization. In this process, particles having a particle diameter of 150 μm or less are inevitably generated. Is becoming. These fine powders are known to occur at a rate of about 20 to 30% during the pulverization or transfer process during the manufacturing process of the super absorbent polymer. Since the fine powder affects the pressure absorbing capacity (AUP) and permeability of the super absorbent polymer, it is difficult to produce a super absorbent polymer having both properties simultaneously increased. For this reason, during the manufacturing process of the super absorbent polymer, particularly in the classification process, these fine powders are separated to produce the super absorbent polymer only with the remaining polymer particles.

However, in products in which a specific particle size ratio needs to be increased in order to exhibit a property with a fast absorption rate, the milling of the roll mill is excessively carried out to realize the particle size distribution, and accordingly, the fine powder of less than 150 μm is greatly increased. As a result, the ratio of fines recycling in the process is maintained. Therefore, the method has a problem in that the load of the drying/grinding/classifying process increases and the production amount decreases.

The present invention is to provide a method for manufacturing a superabsorbent polymer and an apparatus for producing a superabsorbent polymer capable of reducing and suppressing the generation of fine powder while maintaining excellent properties of the superabsorbent polymer.

The present invention (A) in the presence of an internal crosslinking agent and a polymerization initiator, at least a part of the polymerization step of crosslinking polymerization of a water-soluble ethylenically unsaturated monomer having an acidic group neutralized to form a hydrogel polymer; (B) a drying step of drying the hydrogel polymer to prepare a dry polymer; And (C) a grinding step of grinding the dry polymer; The (C) grinding step includes (C1) a first grinding step and (C2) a second grinding step to pulverize the dry polymer, and (C2) the second grinding step is (C21) the An abnormal particle classification step of classifying the primary pulverized dry polymer into'abnormal particles' having a particle diameter equal to or larger than the target particle diameter and'normal particles' having a particle diameter smaller than the target particle diameter; And (C22) provides a method for producing a super absorbent polymer, comprising the step of pulverizing the abnormal particles, collecting and crushing only the'abnormal particles'.

In addition, the present invention is an input unit 100 to which the dry polymer is added; A crushing unit 200 for pulverizing the introduced dry polymer; And an outlet portion 300 for discharging the pulverized dry polymer particles; The crushing unit 200 includes a first crushing unit 210 and a second crushing unit 220 for pulverizing the dried polymer, and the second crushing unit 220 is the first An abnormal particle classifying portion 221 for classifying the dried polymer pulverized in the primary crushing unit 210 into'abnormal particles' having a particle diameter equal to or larger than the target particle diameter and'normal particles' having a particle diameter smaller than the target particle diameter; And an abnormal particle pulverization portion 222 that collects only the “abnormal particles” and pulverizes again.

Hereinafter, a method of manufacturing a super absorbent polymer according to specific embodiments of the present invention will be described in more detail.

Prior to this, the terminology used in this specification is only for referring to specific embodiments, and is not intended to limit the present invention. And, the singular forms used herein also include plural forms unless the phrases express an opposite meaning.

As used herein, the meaning of'comprising' or'containing' embodies a specific property, region, integer, step, action, element or component, and of other specific properties, areas, integers, steps, action, elements, or components. It does not exclude addition.

The term "polymer" or "polymer" as used in the specification of the present invention means that the water-soluble ethylenically unsaturated monomer is in a polymerized state, and may cover all water content ranges or particle size ranges. Among the polymers, a polymer having a water content (moisture content) of about 40% by weight or more as a state after drying after polymerization may be referred to as a hydrogel polymer.

In addition, "superabsorbent polymer" means the polymer or base resin itself depending on the context, or additional processes for the polymer or the base resin, such as surface crosslinking, fine powder reassembly, drying, grinding, classification, etc. It is used to cover everything that has been made suitable for commercialization.

According to one embodiment of the invention, (A) in the presence of an internal crosslinking agent and a polymerization initiator, at least a part of the polymerization step of crosslinking polymerization of a water-soluble ethylenically unsaturated monomer having a neutralized acidic group to form a hydrogel polymer; (B) a drying step of drying the hydrogel polymer to prepare a dry polymer; And (C) a grinding step of grinding the dry polymer; The (C) grinding step includes (C1) a first grinding step and (C2) a second grinding step to pulverize the dry polymer, and (C2) the second grinding step is (C21) the An abnormal particle classification step of classifying the primary pulverized dry polymer into'abnormal particles' having a particle diameter equal to or larger than the target particle diameter and'normal particles' having a particle diameter smaller than the target particle diameter; And (C22) a method for producing a super absorbent polymer, comprising the steps of pulverizing the abnormal particles, collecting and crushing only the'abnormal particles'.

The method for producing a superabsorbent polymer according to the present invention, in the process of forming and drying a hydrogel polymer, pulverizing and then classifying the dried dry polymer, crushing and classifying again only for particles having a certain size or more after the crushing step, preferably By pulverizing and classifying repeatedly about 2 or more times, or 2 to 5 times, or 2 to 4 times, or 3 to 4 times, particles of a certain size or less are prevented from being crushed together, and the particle size is about 150 μm. It is possible to minimize the amount of the following fine powder.

In particular, the present invention, after pulverization, since the classification process using a classifier is essential, it is possible not only to reduce the amount of fines generated, but also to control the particle size according to the particle size in the classifier, so that the particle size of the final product can be easily adjusted. It is possible to provide a method for producing a superabsorbent polymer having physical properties equal to or higher than those of the prior art.

In addition, the present invention reduces the amount of fines generated by controlling the degree of separation by setting the separation target according to the particle size of the classifier during crushing, that is, the target particle size, thereby reducing the load of the fine powder reassembly, drying, pulverization and classification process. Can.

As described above, in this specification, the target target particle size means a particle size that is a standard for classification for separating normal particles and abnormal particles in the abnormal particle classification step of the second grinding step.

According to an embodiment of the present invention, through the above-described method, the particles in a specific size range are classified through classification in each crushing step, and small-sized particles (for example, about By separating particles having a particle diameter of 200 µm or less, or about 150 µm or less), it is possible to selectively exclude such particles from being re-introduced into grinding.

In addition, the present invention is to arbitrarily select the size of the classifier used in this process according to the target particle size, easily adjust the particle size of the particles used in the final product to a specific range, thereby changing the properties of the super absorbent polymer. Can.

Hereinafter, the present invention will be described in detail for each step.

(Polymerization step)

The polymerization step is a step of forming a hydrogel polymer, and is a step of crosslinking and polymerizing a monomer composition comprising an internal crosslinking agent and a water-soluble ethylenically unsaturated monomer having at least a partially neutralized acidic group.

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

[Formula 1]

R ¹ -COOM ¹

In Chemical Formula 1,

R ¹ 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. When acrylic acid or a salt thereof is used as the water-soluble ethylenically unsaturated monomer, it is advantageous to obtain a superabsorbent polymer with improved absorbency. 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-(metha) )Acrylamide-2-methyl propane sulfonic acid, (meth)acrylamide, N-substituted (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, methoxypolyethylene Glycol (meth)acrylate, polyethylene glycol (meth)acrylate, (N,N)-dimethylaminoethyl (meth)acrylate, (N,N)-dimethylaminopropyl (meth)acrylamide, and the like can be used.

Here, the water-soluble ethylenically unsaturated monomer has an acidic group, and at least a portion of the acidic group may be neutralized. Preferably, the monomer may be partially neutralized with an alkali material such as sodium hydroxide, potassium hydroxide or ammonium hydroxide.

In this case, the degree of neutralization of the monomer may be about 40 to about 95 mol%, or about 40 to about 80 mol%, or about 45 to about 75 mol%. The range of the degree of neutralization may vary depending on the final physical properties, but if the degree of neutralization is too high, the neutralized monomer may be precipitated and polymerization may be difficult to proceed smoothly. It may exhibit properties such as elastic rubber that are difficult to handle.

In addition, the concentration of the water-soluble ethylenically unsaturated monomer in the monomer composition may be appropriately adjusted in consideration of polymerization time and reaction conditions, and preferably about 20 to about 90% by weight, or about 40 to about 65% by weight Can. This concentration range may be advantageous for controlling the grinding efficiency when pulverizing the polymer, which will be described later, while eliminating the need to remove unreacted monomers after polymerization by using the gel effect phenomenon that occurs in the polymerization reaction of a high concentration aqueous solution. However, if the concentration of the monomer is too low, the yield of the super absorbent polymer may be lowered. Conversely, if the concentration of the monomer is too high, a part of the monomer may be precipitated or there may be a process problem such as poor crushing efficiency when pulverizing the polymerized hydrogel polymer, and physical properties of the super absorbent polymer may be deteriorated.

Further, as the internal crosslinking agent, any compound can be used as long as it allows introduction of crosslinking during polymerization of the water-soluble ethylenically unsaturated monomer. As a non-limiting example, the internal crosslinking agent is N,N'-methylenebisacrylamide, trimethylolpropane 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, hexanediol di(meth) )Acrylate, triethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, dipentaerythritol pentaacrylate, glycerin tri(meth)acrylate, penta Multifunctional crosslinking agents such as erythritol tetraacrylate, triarylamine, ethylene glycol diglycidyl ether, propylene glycol, glycerin, or ethylene carbonate may be used alone or in combination of two or more, but are not limited thereto.

The internal crosslinking agent may be added in a concentration of about 0.001 to about 1% by weight relative to the monomer composition. That is, when the concentration of the internal crosslinking agent is too low, the absorption rate of the resin is lowered and the gel strength may be weakened, which is not preferable. Conversely, when the concentration of the internal cross-linking agent is too high, the absorbency of the resin is lowered, which may make it undesirable as an absorber.

In addition, in the polymerization step, a polymerization initiator generally used in the production of a super absorbent polymer may be included. As a non-limiting example, as the polymerization initiator, a thermal polymerization initiator or a photo polymerization initiator may be used depending on the polymerization method, and a thermal polymerization initiator may be used. However, even by 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 according to the progress of the exothermic polymerization reaction, a thermal polymerization initiator may be additionally included.

As the thermal polymerization initiator, one or more compounds selected from the group consisting of a persulfate-based initiator, an azo-based initiator, hydrogen peroxide, and ascorbic acid may be used. Specifically, as the persulfate-based initiator, sodium persulfate (Na ₂ S ₂ O ₈ ), potassium persulfate (K ₂ S ₂ O ₈ ), ammonium persulfate (A mmonium persulfate; (NH ₄ ) ₂ S ₂ O ₈ ) and the like. In addition, as the azo-based initiator, 2,2-azobis-(2-amidinopropane) dihydrochloride (2,2-azobis(2-amidinopropane) dihydrochloride), 2,2-azobis-(N, N-dimethylene)isobutyramidine dihydrochloride (2,2-azobis-(N,N-dimethylene)isobutyramidine dihydrochloride), 2-(carbamoyl azo)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, For example, 4-azobis-(4-cyanovaleric acid) (4,4-azobis-(4-cyanovaleric acid)). More various thermal polymerization initiators are disclosed on page 203 of the Odian book "Principle of Polymerization (Wiley, 1981)", which can be referred to. Preferably, ascorbic acid and potassium persulfate are used as the thermal polymerization initiator.

Examples of the photo polymerization initiator include, for example, benzoin ether, dialkyl acetophenone, hydroxyl alkylketone, phenyl glyoxylate, and benzyl dimethyl ketal ( One or more compounds selected from the group consisting of Benzyl Dimethyl Ketal, acyl phosphine and alpha-aminoketone may be used. Among them, as a specific example of acylphosphine, a commercially available lucirin TPO, that is, 2,4,6-trimethyl-benzoyl-trimethyl phosphine oxide (2,4,6-trimethyl-benzoyl-trimethyl phosphine oxide) can be used. . More various photopolymerization initiators are disclosed on page 115 of Reinhold Schwalm's book "UV Coatings: Basics, Recent Developments and New Application (Elsevier 2007)", which can be referred to.

The polymerization initiator may be added in a concentration of about 0.001 to 1% by weight relative to the monomer composition. That is, when the concentration of the polymerization initiator is too low, the polymerization rate may be slow, and residual monomers in the final product may be extracted in large quantities, which is not preferable. Conversely, when the concentration of the polymerization initiator is higher than the above range, the polymer chains forming the network are shortened, and thus the content of the water-soluble component is increased and the pressure absorption capacity is lowered, so that the physical properties of the resin may be deteriorated, which is not preferable.

In addition, the polymerization step can be carried out in the presence of a blowing agent. The foaming agent foams during polymerization to form pores in the hydrogel polymer to increase the surface area. The foaming agent may be an inorganic foaming agent or an organic foaming agent. Examples of inorganic blowing agents include sodium bicarbonate, sodium carbonate, potassium bicarbonate, potassium carbonate, calcium bicarbonate, and calcium bicarbonate. , Magnesium bicarbonate or magnesium carbonate. In addition, examples of the organic blowing agent are azodicarbonamide (ADCA), dinitroso pentamethylene tetramine (DPT), p,p'-oxybisbenzenesulfonylhydrazide (p,p' -oxybisbenzenesulfonylhydrazide (OBSH), and p-toluenesulfonyl hydrazide (TSH).

In addition, the blowing agent is preferably used in an amount of about 0.001 to about 1% by weight based on the weight of the water-soluble ethylenically unsaturated monomer. When the amount of the blowing agent exceeds about 1% by weight, the pores become too large, the gel strength of the super absorbent polymer falls and the density becomes small, which may cause problems in distribution and storage.

In addition, the monomer composition may further include additives such as a surfactant, a thickener, a plasticizer, a storage stabilizer, and an antioxidant, if necessary.

And, such a monomer composition may be prepared in the form of a solution in which a raw material such as the above-described monomer is dissolved in a solvent. At this time, as a usable solvent, any material that can dissolve the aforementioned raw materials can be used without limitation of its configuration. For example, the solvent includes 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 , Methyl ethyl ketone, acetone, methyl amyl ketone, cyclohexanone, cyclopentanone, diethylene glycol monomethyl ether, diethylene glycol ethyl ether, toluene, xylene, butyrolactone, carbitol, methyl cellosolve acetate, N,N-dimethylacetamide, or mixtures thereof, and the like can be used.

And, the formation of a hydrogel polymer through polymerization of the monomer composition may be performed by a conventional polymerization method, and the process is not particularly limited. As a non-limiting example, the polymerization method is largely divided into thermal polymerization and photo polymerization according to the type of polymerization energy source. When the thermal polymerization is performed, the polymerization method may be performed in a reactor having a stirring axis such as a kneader, and photo polymerization In the case of proceeding, it may proceed in a reactor equipped with a movable conveyor belt.

For example, a hydrogel polymer may be obtained by introducing the monomer composition into a reactor such as a kneader equipped with a stirring shaft, and supplying hot air to it or heating the reactor to thermally polymerize it. At this time, depending on the type of agitation shaft provided in the reactor, the hydrogel polymer discharged to the reactor outlet may be obtained as particles of several millimeters to several centimeters. Specifically, the resulting hydrogel polymer can be obtained in various forms depending on the concentration and injection speed of the monomer composition to be injected, and a hydrogel polymer having a particle diameter of 2 to 50 mm (average weight) is usually obtained.

And, as another example, when the photopolymerization of the monomer composition in a reactor equipped with a movable conveyor belt is performed, a hydrogel polymer in the form of a sheet may be obtained. At this time, the thickness of the sheet may vary depending on the concentration and injection rate of the monomer composition to be injected. In order to ensure the production speed and the like while allowing the entire sheet to be evenly polymerized, it is usually adjusted to a thickness of 0.5 to 5 cm. desirable.

At this time, the normal water content of the hydrogel polymer obtained in this way may be about 40 to about 80% by weight. On the other hand, "water content" in the present specification refers to a value obtained by subtracting the weight of the polymer in the dry state from the weight of the water-containing gel polymer as the amount of moisture occupied with respect to the total weight of the hydrogel polymer. Specifically, it is defined as a calculated value by measuring a weight loss due to evaporation of water in the polymer during the drying process by raising the temperature of the polymer through infrared heating. At this time, the drying condition is a method of raising the temperature from room temperature to about 180°C and then maintaining it at about 180°C. The total drying time is set to about 20 minutes, including about 5 minutes in the temperature rising step, to measure the water content.

(Drying step)

The drying step is a step of drying the hydrogel polymer prepared in the polymerization step to make a dry polymer.

Separately, according to an example of the invention, before drying the hydrogel polymer as described above, the hydrogel polymer having a water content of about 40 to about 80% by weight is pulverized in a hydrogel state, as described above, to improve drying efficiency. A gel grinding or gel disintegration step, which promotes improvement, may optionally be performed.

Such gel grinding, or gel disintegration, is a vertical pulverizer, a turbo cutter, a turbo grinder, a rotary cutter mill, and a cutter mill. , Disc mill, shred crusher, crusher, chopper, and disc cutter may be performed using any one selected from the group of grinding machines.

At this time, the gel grinding step may be performed such that the particle diameter of the hydrogel polymer after grinding is about 2 mm to about 10 mm. It is not technically easy to adjust the particle size after gel grinding to be small due to the high water content of the hydrogel polymer, and when the particle diameter is too small after pulverization, a phenomenon that the pulverized hydrogel polymers aggregate again may appear. On the other hand, if the particle size is too large after gel grinding, the effect of increasing the efficiency of the subsequent drying step may be insignificant.

The hydrous gel-like polymer that has been subjected to gel grinding as described above or has not undergone a gel grinding step is introduced into a drying step and dried.

At this time, the drying temperature of the drying step may be about 50 to about 250 ℃. If the drying temperature is too low, a drying time may be too long, and a problem of deterioration in physical properties of the superabsorbent polymer to be formed may occur. When the drying temperature is too high, only the polymer surface is dried due to a fast drying rate, which is achieved later. Fine powder may be generated in the pulverization process, and there is a fear that the physical properties of the superabsorbent polymer finally formed may be deteriorated.

More preferably, the drying may be carried out at a temperature of about 150 to about 200 ℃, more preferably at a temperature of about 160 to about 190 ℃. On the other hand, in the case of drying time, process efficiency and the like may be considered, and may be performed for about 20 minutes to about 15 hours, but the present invention is not necessarily limited thereto.

The device used in the drying, as long as it is generally used in the technical field to which the present invention pertains, may be selected and used without limitation of its 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 the drying step, that is, the dry polymer may be from about 0.05 to about 10% by weight.

(Grinding step)

The crushing step is a step of pulverizing the dried polymer dried in the drying step to prepare a base resin in the form of particles, and may be divided into a first crushing step and a second crushing step.

In the present invention, in order to reduce the generation of fine powder, it is characterized in that, among the particles pulverized through the first pulverization, only abnormal particles having a particle diameter equal to or larger than a target particle diameter are again pulverized.

In general, in the case of pulverizing the base resin, in order to improve the efficiency of pulverization, coarse pulverization and fine pulverization are often performed separately by setting different pulverization particle sizes.

In the manufacturing method according to an aspect of the present invention, i) the first grinding may correspond to coarse grinding, and the second grinding may correspond to fine grinding. Alternatively, ii) both the first pulverization and the second pulverization may correspond to a fine grinding process.

In a manufacturing method according to an embodiment of the present invention, in the case of ii) in which both the first and second pulverization correspond to fine grinding, it may be further performed by further comprising a separate coarse pulverization process prior to the first pulverization. When further comprising a separate co-grinding process, the particles of the pulverized base resin after co-grinding may be preferable in terms of the efficiency of crushing in a particle size range of about 800 μm to about 5000 μm.

The present invention can be carried out using a continuous roll mill and classifier. In one example, the grinding step may be performed using a single roll mill, or a multi-stage roll mill, and a classifier.

The classifier is provided with a classifier having the same size as the target particle size, and performs the primary classification with'normal particles' having a particle size larger than the target particle size and'normal particles' having a particle diameter less than the target particle size. do.

At this time, the target target particle size, as described above, in the second particle classification step of the second pulverization step, means a particle diameter that is a reference for classification for separating normal particles and abnormal particles, from about 200 to about 850 It can be selected in the range of μm. Preferably, it may be selected from a range of about 200 μm or more, or about 300 μm or more, or about 420 μm or more, about 850 μm or less, or about 800 μm or less, or about 750 μm or less, or about 700 μm or less.

In the manufacture of a conventional super absorbent polymer, in order to produce particles having a particle diameter of 150 μm to 850 μm (180 to 850 μm, or 300 to 850 μm), continuous grinding is performed, and accordingly, particles having the particle size can be produced. However, since particles crushed to a certain size or less in the first crushing step, that is, particles falling within a normal range or smaller particles, are also re-injected into crushing in the next step, there is a problem that the generation of relatively fine powder is relatively high. .

However, in the present invention, since the abnormal particles and the normal particles are separated between each pulverization step, and only the abnormal particles are added to the subsequent pulverization step, the pulverization conditions in each pulverization step can be relaxed and proceed. Accordingly, it is possible to increase the'ratio of particles having a relatively large particle size', which is a target in each grinding step, and as a result, the generation of fine powder in each grinding step can be further reduced.

Preferably, in the particles produced through the first pulverization step, the proportion of abnormal particles having a particle diameter equal to or greater than the target target particle diameter is about 60 wt% or more, or about 80 wt%, relative to the total weight of the whole crushed particles The pulverization conditions of the first pulverization may be adjusted to be greater than or equal to or greater than about 90 wt%, less than or equal to about 99 wt%, or less than about 95 wt%.

In addition, in the particles produced through the pulverizing step, particles having a particle diameter of less than about 180 μm, or less than about 150 μm, that is, fine particles or fine powder, about 10.0 wt% or less, based on the total weight of the total pulverized particles, about The pulverization conditions of the first pulverization can be adjusted to be 5.0 wt% or less, or about 1.0 wt% or less.

The fine particles having a particle diameter of less than about 150 μm or less than about 180 μm among the particles prepared in the grinding step may be discarded or reassembled by adding water to circulate to the drying step.

The second pulverization step is a step of classifying and pulverizing the first pulverized particles in the pulverization step. In order to distinguish it from the first pulverization step described above, it is referred to as'secondary pulverization' in this specification. .

As described above, when the first pulverization corresponds to coarse pulverization, the second pulverization may refer to the first pulverization step of pulverization. In addition, if the first pulverization is performed in a separate co-grinding step, the first pulverization is the first pulverization step of the fine grinding, and the second pulverization means the second pulverization stage of the fine grinding. Can.

As described above, in the first grinding step, since the proportion of particles having a relatively large particle size is higher than in the prior art, in order to prepare particles having a particle size of 150 μm to 850 μm (180 to 850 μm, or 300 to 850 μm), additional Grinding is necessary.

At this time, in the present invention, the second grinding process is performed at least once, or at least twice, or 2 to 5 times, or 3 to 4 times, and by using the grinder and classifier together in each grinding step, the target particle size The smaller particles can be prevented from being further crushed together with particles larger than the target particle size, thereby reducing the generation of fines.

As described above, when the first pulverization corresponds to coarse pulverization, it may be more preferable to perform the second pulverization, that is, separate fine pulverization two or more times.

According to a preferred embodiment, the first and second angular crushing steps of the present invention use a continuous multi-stage roll mill, or a continuous single roll mill, wherein the sequential roll mill is the bottom of the crushing stage or the last stage. By introducing the classifier in the previous step, only the abnormal particles having a particle size equal to or more than the target particle size described above are introduced into the roll mill of the next step. Through this, it is characterized in that it suppresses the generation of fine powders in the corresponding process by blocking the possibility of normal particles having a particle size smaller than the target target particle size being re-injected into the lower roll mill and crushed.

In addition, the present invention can be carried out by using the multi-stage roll as described above, but the gap width of each stage of the roll forming the multi-stage roll is different from the top to the bottom.

Specifically, according to one embodiment of the invention, in the second grinding, it is preferable to use a device having a narrower roll gap width than the first grinding, and the second grinding is repeated two or more times. In the case, it is preferable to use a narrower roll gap width as the order is added.

In the present invention, the gap width may refer to the distance between the rolls in the configuration of each stage constituting the multi-stage roll.

That is, according to one embodiment of the present invention, stepwise narrowing the distance between the roll mills to increase the degree of crushing, normal particles among the crushed products crushed in each step do not proceed to further grinding, only additional grinding By putting in the step, excessive pulverization can be reduced, and accordingly, the amount of fine powder can be reduced.

According to one embodiment of the invention, the roll used for grinding may consist of two. Here, the gap width refers to the distance between two rolls. The narrower the gap width of the roll, the smaller the size distribution of the pulverized particles.

When using a continuous multi-stage roll, preferably, the gap width of the upper roll mill can be fixedly positioned to be, for example, about 4.0 to about 5.0 mm, and the gap width of the lower roll mill is, for example, about 1.5 mm It can be made as follows. That is, it is preferable to perform grinding and classification while gradually reducing the width of the roll gap by the second number of times of grinding. For example, it is preferable to adjust the gap width of the single roll mill forming the bottom while narrowing the gap width by about 0.3 mm to about 0.6 mm, depending on the number of times the second milling is performed.

In addition, in the particles produced by the second pulverization, a re-classification step may be added to classify the particles into particles having a particle diameter of about 150 to about 850 μm again and smaller particles, among which about 150 to Particles having a particle diameter of about 850 μm can be used as the final product.

In addition, in the case of the present invention, it may include a step of separating particles having a particle diameter of less than 150 μm, that is, fine particles or fine powder, re-assembled by adding water, and circulating to the drying step. The reassembly method may be performed according to a method well known in the art, but is not limited to the method.

In addition, in the present invention, the surface of the single roll mill may exhibit a corrugated roll surface, but is not limited thereto. In addition, the rotational speed of a single roll mill constituting each stage may be 2 m/s to 15 m/s.

(Other steps)

In addition, the present invention may include a step of crosslinking the surface of the prepared particles as necessary.

That is, the present invention can use the normal particles obtained through the above-described method as a base resin powder. Therefore, the present invention may further include forming a surface crosslinking layer by further crosslinking the surface of the base resin powder in the presence of a surface crosslinking agent.

Specifically, in the presence of a surface crosslinking solution, the step of heat-treating the prepared particles may further include surface crosslinking.

The surface crosslinking solution may include any one or more surface crosslinking agents selected from the group consisting of compounds having two or more epoxy rings, and compounds having two or more hydroxys.

Preferably, the surface crosslinking solution includes both compounds having two or more epoxy rings and compounds having two or more hydroxys. In this case, the surface crosslinking solution contains a compound having two or more epoxy rings and a compound having two or more hydroxy groups in a ratio of 1:1.1 to 1:5.

Examples of the compound having two or more epoxy rings, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerol polyglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl Diyl ether, 1,4-butanediol diglycidyl ether, 1,4-cyclohexanedimethanol diglycidyl ether, hexahydrophthalic anhydride diglycidyl ether, neopentyl glycol diglycidyl ether, And at least one compound selected from the group consisting of bisphenol a diglycidyl ether and N,N-diglycidyl aniline. Preferably, ethylene glycol diglycidyl ether is used.

Examples of the compound having two or more hydroxy, ethylene glycol, diethylene glycol, propylene glycol, triethylene glycol, tetraethylene glycol, propane diol, dipropylene glycol, polypropylene glycol, glycerin, polyglycerin, butanedi And one or more compounds selected from the group consisting of all, heptanediol, hexanediol, trimethylolpropane, pentaerythritol, and sorbitol. Preferably, propylene glycol is used.

At this time, the surface crosslinking agent is preferably used in an amount of 1 part by weight or less based on 100 parts by weight of the base resin. Here, the amount of the surface crosslinking agent used means the total amount of the surface crosslinking agent when two or more are used. When the surface crosslinking agent is used in an amount of more than 1 part by weight, excessive surface crosslinking may occur, and various properties of the super absorbent polymer, particularly, dryness may be deteriorated. In addition, the surface crosslinking agent is preferably used in an amount of 0.01 parts by weight or more, 0.02 parts by weight or more, 0.03 parts by weight or more, 0.04 parts by weight or more, or 0.05 parts by weight or more based on 100 parts by weight of the base resin.

In addition, the surface crosslinking solution is 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, Methyl ethyl ketone, acetone, methyl amyl ketone, cyclohexanone, cyclopentanone, diethylene glycol monomethyl ether, diethylene glycol ethyl ether, toluene, xylene, butyrolactone, carbitol, methyl cellosolve acetate and N, It may further include one or more solvents selected from the group consisting of N-dimethylacetamide. Preferably, water is included. The solvent may be used in 0.5 to 10 parts by weight relative to 100 parts by weight of the base resin powder.

In addition, the surface crosslinking solution may further include aluminum sulfate. The aluminum sulfate may be included in 0.02 to 0.3 parts by weight based on 100 parts by weight of the base resin powder.

In addition, the surface crosslinking solution may include an inorganic filler. The inorganic filler may include silica, aluminum oxide, or silicate. The inorganic filler may be included in an amount of 0.01 to 0.5 parts by weight based on 100 parts by weight of the base resin powder.

In addition, the surface crosslinking solution may further include a thickener. When the surface of the base resin powder is further crosslinked in the presence of a thickener in this way, deterioration in physical properties can be minimized even after grinding. Specifically, one or more selected from polysaccharides and hydroxy-containing polymers may be used as the thickener. As the polysaccharide, a gum-based thickener and a cellulose-based thickener may be used. Specific examples of the gum-based thickener include xanthan gum, arabic gum, karaya gum, tragacanth gum, ghatti gum, guar gum (guar gum), locust bean gum (locust bean gum) and silylium seed gum, and the like, and specific examples of the cellulose-based thickener include hydroxypropyl methyl cellulose, carboxymethyl cellulose, and methyl cellulose , Hydroxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, hydroxyethylmethylcellulose, hydroxymethylpropylcellulose, hydroxyethylhydroxypropylcellulose, ethylhydroxyethylcellulose and methylhydroxypropylcellulose Can. Meanwhile, specific examples of the hydroxy-containing polymer 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 mixed in a reaction tank, a method of spraying a surface crosslinking solution on the base resin, and the surface resin and the surface crosslinking in a continuously operated mixer. A method of continuously supplying and mixing the liquid may be used.

In addition, the surface crosslinking may be performed under a temperature of 100 to 250°C, and may be continuously performed after the drying and pulverizing steps proceeding at a relatively high temperature. At this time. The surface crosslinking reaction may be performed for 1 to 120 minutes, or 1 to 100 minutes, or 10 to 60 minutes. That is, while inducing a minimum amount of the surface crosslinking reaction, the polymer particles may be damaged during excessive reaction to prevent the physical properties from being deteriorated, and thus the conditions of the surface crosslinking reaction may be performed.

(Device)

On the other hand, according to another aspect of the present invention, the input unit 100 to which the dry polymer is introduced; A crushing unit 200 for pulverizing the introduced dry polymer; And an outlet portion 300 for discharging the pulverized dry polymer particles; The crushing unit 200 includes a first crushing unit 210 and a second crushing unit 220 for pulverizing the dried polymer, and the second crushing unit 220 is the first An abnormal particle classifying portion 221 for classifying the dried polymer pulverized in the primary crushing unit 210 into'abnormal particles' having a particle diameter equal to or larger than the target particle diameter and'normal particles' having a particle diameter smaller than the target particle diameter; And an abnormal particle pulverization portion 222 that collects only the “abnormal particles” and crushes them again.

1 shows a super absorbent fabrication apparatus according to an embodiment of the present invention.

Referring to Figure 1, in the super absorbent polymer manufacturing apparatus according to another embodiment of the present invention, the input unit 100 is introduced to the dry polymer; A crushing unit 200 for pulverizing the introduced dry polymer; And an outlet portion 300 for discharging the pulverized dry polymer particles; The crushing unit 200 includes a first crushing unit 210 and a second crushing unit 220 for pulverizing the dried polymer, and the second crushing unit 220 is the first An abnormal particle classifying portion 221 for classifying the dried polymer pulverized in the primary crushing unit 210 into'abnormal particles' having a particle diameter equal to or larger than the target particle diameter and'normal particles' having a particle diameter smaller than the target particle diameter; And it can be seen that it comprises an abnormal particle crushing portion 222, which collects only the'abnormal particles' and crushes it again.

At this time, it may be preferable that the second pulverization unit includes one or more or two or more.

In addition, the crushing unit includes a roll mill, and the roll gap width in the roll mill forming each stage included in the first crushing unit and the second crushing unit has a structure that becomes narrower from top to bottom. It may be preferable, and if the second pulverization part is included in two or more, it may also be desirable to have a structure in which the width of the roll gap in the roll mill forming each stage becomes narrower as the order is added.

In addition, the abnormal particle classification portion may be located at the bottom of each stage single roll mill.

Specifically, when explaining the device according to an embodiment of the present invention, first, the base resin dried through the input unit 100 is introduced, and is moved to the first crushing unit 210.

While passing through the primary grinding unit, the primary milled base resin is moved to the secondary grinding unit 220 at the bottom. The second pulverization unit is an abnormality in which the dry polymer pulverized in the first pulverization unit 210 is classified into'abnormal particles' having a particle diameter equal to or larger than a target particle diameter and'normal particles' having a particle diameter smaller than a target particle diameter. It includes a particle classification portion 221, and such a classification portion may be specifically configured in the form of a classification body.

Among the base resin particles pulverized in the primary crushing unit 210, in the case of abnormal particles, through the abnormal particle classification part 221, only'abnormal particles' are collected and crushed again, to the abnormal particle crushing part 222 It is injected, and in the case of normal particles, it passes directly through the particle classification portion 221 in the form of a sieve, and is moved to the discharge portion.

The abnormal particles introduced into the abnormal particle crushing portion 222 are again crushed by a roll mill.

The base resin particles pulverized again in the abnormal particle crushing portion 222 again pass through the abnormal particle classification portion 221, in which, in the case of abnormal particles, only ``abnormal particles'' are collected and crushed again, 222), and in the case of normal particles, may pass directly through the particle classification portion 221 in the form of a sieve, and may be moved to the discharge portion.

It has been described above that the second crushing unit may include one or more.

The present invention, in the process of forming a hydrogel polymer to form a super absorbent polymer, and then classifying it after drying, pulverize large particles of a certain size or more, and filter particles of a certain size or less through classification after each step to filter the particles It can block crushing and minimize the formation of particles of 150 μm or less.

Furthermore, the present invention can be repeated several times to change the particle size of the final superabsorbent polymer product by varying the particle size of the classification after each step of pulverization and at the time of classification. In addition, the superabsorbent polymer production method according to the present invention, while implementing a narrow particle size distribution in the grinding process of the dried polymer, reducing the amount of fine powder, it is possible to reduce the load of the fine powder reassembly, drying, grinding and classification process.

1 schematically shows an apparatus for manufacturing a super absorbent polymer according to an embodiment of the present invention.

Hereinafter, preferred embodiments are presented to aid in understanding of the invention. However, the following examples are only for illustrating the present invention, and the present invention is not limited thereto.

Example 1

Polymerization step

100 g of acrylic acid in a glass reactor, 132.3 g of a 31.5% by weight caustic soda (NaOH) solution, 0.39 g of a capsule-type blowing agent, 0.002 g of polyethylene glycol diacrylate, 0.12 g of ethylene glycol diglycidyl ether, thermal polymerization initiator sodium persulfate 0.17 g, a photopolymerization initiator (diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide) 0.008 g, sodium dodecyl sulfate aqueous solution 0.036 g and 50.0 g of water to prepare a monomer composition having a total solids concentration of 43% by weight It was prepared.

The monomer composition was supplied at a speed of 500 to 2000 mL/min on a rotating conveyor belt in which a belt of 10 cm in width and 2 m in length continuously moves at a speed of 50 cm/min. Then, simultaneously with the supply of the monomer composition, irradiated with ultraviolet light having an intensity of 10 mW/cm ² , a polymerization reaction was performed for 60 seconds to prepare a hydrogel polymer.

Gel grinding and drying steps

The hydrogel polymer having the polymerization reaction completed is cut to a size of 0.1 to 1.0 cm × 0.1 to 1.0 cm through a screw-type extruder (meat chopper: hole size 16 mm) mounted inside the cylindrical grinder, and an air-flow oven is used. And dried at 195°C for 40 minutes.

Grinding stage: primary grinding (including coarse grinding) and classification stage

The dried polymer was ground using a two-stage roll mill (GRAN-U-LIZERTM, MPE). After grinding, the grinding conditions were adjusted so that the particle ratio of 600 µm or more became 90% or more.

The pulverized polymer particles were classified using a classifying sieve, and then separated into particles of 600 µm or more and particles of less than 600 µm. In addition, when classifying, the standards of classifiers are classified using 4750 μm, 3350 μm, 2000 μm, 850 μm, 710 μm, 600 μm, 425 μm, 300 μm, 180 μm, and 150 μm pan based on ASTM standards. After pulverization, the particle size of the particles was measured.

In the two-stage roll used, the roll gap width of the top roll was about 5.0 mm, and the roll gap width of the bottom roll was about 4.0 mm.

Fine grinding and classification

In the above step, only particles having a particle diameter of 600 µm or more among the pulverized/classified particles were selected, and were subjected to a plurality of secondary pulverization (pulverization) and classification processes. A single roll mill was used for the fine grinding, and a classifier and a classifier were used for classifying.

Specifically, particles having a particle diameter of 600 µm or more among the particles that were first coarsely pulverized in the above step were pulverized using a single roll mill. The pulverized particles were separated into particles having a particle diameter of 600 µm or more (ie, abnormal particles) and particles having a particle diameter of less than 600 µm (ie, normal particles) using a classifier disposed at the rear end.

Thereafter, the normal particles were discharged as they were, and only the abnormal particles were selected, and then put again in a single roll mill to perform grinding. The pulverized particles were separated into abnormal particles having a particle diameter of 600 µm or more and normal particles having a particle diameter of less than 600 µm through a classifier placed at the rear end of the roll mill. The normal particles were discharged as they were, and only the abnormal particles were selected, and then again put into a single roll mill to perform grinding.

As described above, the crushing was repeated three times and the classification process was repeated two times. At this time, the roll gap width of the single roll mill was 1.0 mm, 0.4 mm, and again 0.19 mm. .

All particles separated in each crushing and classification step were collected.

Surface crosslinking

The particles collected in the above are classified by a standard network of ASTM standard by a conventional method, to separate coarse powder having a particle diameter of 850 µm or more and fine powder having a particle size of 150 µm or less, and 150 µm or more and 850 as particles for product production. Only particles smaller than μm were selected.

Using the selected particles as a base resin, surface crosslinking was performed.

To the base resin powder 100 g, ultrapure water 5.9 g, Methanol 5.0 g, Ethylene Glycol Diglycidyl Ether 0.034 g, 50% Polycarboxylic ether 0.2 g, silica (A200) 0.04 g, 23% aluminum sulfate solution 1.73 g surface crosslinking agent mixed solution And mixed for 20 seconds. This was heat-treated at 140° C. for 35 minutes to undergo surface crosslinking, and then classified to prepare superabsorbent polymer particles having a particle diameter of 150 μm to 850 μm.

Example 2

In Example 1, in the fine grinding and classifying step, the target particle size was set to 425 µm, not 600 µm, and the roll gap width of the single roll mill was 1.0 mm, 0.4 mm, and again 0.17 mm in three pulverization processes. , It proceeded in the same manner as in Example 1, except that the width of the roll gap was narrowed according to the number of times of each progress.

Example 3

In Example 1, in the pulverizing and classifying step, two pulverizing and one classifying processes were repeated, and the roll gap width of a single roll mill was 0.6 mm and 0.16 mm in each of the two pulverizing processes. Accordingly, the procedure was the same as in Example 1, except that the width of the roll gap was narrowed.

Example 4

In Example 1, in the pulverizing and classifying step, four pulverizing and three classifying processes were repeated, and the roll gap width of a single roll mill in two pulverizing processes was 1.5 mm, 0.8 mm, 0.4 mm, and 0.18 mm. Furnace, the process was performed in the same manner as in Example 1, except that the width of the roll gap was narrowed according to the number of times of each progress.

Comparative Example 1

In Example 1, without performing a separate classification process after pulverization, all the pulverized particles are introduced into a subsequent roll mill, and in three fine grinding processes, the roll gap width of a single roll mill is 1.0 mm, 0.4 mm, 0.16. In mm, the procedure was the same as in Example 1, except that the width of the roll gap was narrowed according to the number of times of each progress.

Experimental Example 1

The particles obtained in Examples and Comparative Examples were collected, and particle sizes were measured using a sieve for classification.

A mesh sieve of 850 µm, 710 µm, 600 µm, 425 µm, 300 µm, 180 µm, and 150 µm Pan of ASTM standard was used, and vibration was applied for 10 minutes at an amplitude of 1.5 mm/'g' to classify particles. After that, the weight of the particles on the top of each sieve was measured to obtain the particle size.

	Fraction ratio (% by weight)
Particle size	Comparative Example 1	Example 1	Example 2	Example 3	Example 4
20 mesh phase (>850 μm)	0.1	0.0	0.1	0.1	0.1
30 mesh phase (600 μm or more but less than 850 μm)	2.5	3.4	3.2	3.2	3.0
40 mesh phase (425 µm or more and less than 600 µm)	24.4	36.9	24.6	31.8	36.5
50 mesh phase (300 μm or more but less than 425 μm)	25.2	21.6	28.9	23.1	22.5
100 mesh phase (more than 150 ㎛ less than 300 ㎛)	22.3	18.2	22.0	19.9	18.1
100 mesh pass (less than 150 ㎛)	25.5	19.9	21.2	21.9	19.8
Differentiation rate*	34.2	24.8	26.9	28.0	24.6
* A value obtained by dividing the weight (g) of particles having a particle diameter of less than 150 μm by the weight (g) of particles (normal particles) having a particle diameter of 150 μm or more to less than 850 μm.

Referring to Table 1, as a result of particle size analysis of the polymer particles obtained in Comparative Example 1, particles having a size of 600 μm or more and less than 850 μm are about 2.5 wt%, particles having a size of 425 μm or more and less than 600 μm are about 24.4 wt%, 300 μm Particles having a size of more than 425 µm were about 25.2% by weight, and particles having a size of 150 µm or more and less than 300 µm constituted 22.4% by weight. The ratio of fine powder generation to normal particles having a particle diameter of 150 µm or more and less than 850 µm was about 34.3% by weight. The term fine powder refers to particles having a size of less than 150 μm.

On the other hand, as a result of analyzing the particle size of the polymer particles obtained in Example 1, particles having a size of 600 μm or more and less than 850 μm are about 3.4% by weight, particles having a size of 425 μm or more and less than 600 μm are about 36.9% by weight, 300 μm or more and having a size of less than 425 μm The particles were about 21.5% by weight, and particles having a size of 150 μm or more and less than 300 μm were about 18.2% by weight. Therefore, in Example 1, when compared with Comparative Example 1, the proportion of particles having a size of 425 µm or more and less than 600 µm was increased, and a ratio of particles having a size of 150 µm or more and less than 425 µm was decreased. In addition, the ratio of fine particles to the normal particles was about 24.9% by weight, showing an effect of decreasing by about 27% compared to Comparative Example 1. This is thought to be caused by separating particles having a particle diameter of less than about 600 μm through classification in the fine grinding process and blocking them from being added to a further grinding process.

As a result of particle size analysis of the polymer particles obtained in Example 2, particles having a size of 600 μm or more and less than 850 μm are about 3.2 wt%, particles having a size of 425 μm or more and less than 600 μm are about 24.6 wt%, particles having a size of 300 μm or more and less than 425 μm Was about 28.9% by weight, and particles having a size of 150 μm or more and less than 300 μm were about 22.0%. As compared with Comparative Example 1, it showed a similar particle size distribution. However, the ratio of fine powder generation to normal particles was about 27% by weight, showing an effect of about 21% reduction compared to Comparative Example 1. Through this, it was clearly confirmed that the particle size of the pulverized particles can be adjusted by varying the classification criteria of the classified particles in the fine grinding process, that is, the target particle size.

As a result of the particle size analysis of the polymer particles obtained in Examples 3 and 4, the ratio of fine particles to the normal particles was about 28.2% by weight and about 24.8% by weight, respectively. As the number of times the pulverization and classification was repeatedly performed in the pulverization process, it was confirmed that the amount of pulverization was decreased and the reduction rate according to the number of times was decreased.

Experimental Example 2

Among the particles obtained in Examples and Comparative Examples, the following physical properties were measured for normal particles.

(1) Bulk density (B/D)

After flowing 100 g of the particles prepared in Examples and Comparative Examples through a standard flow measurement device orifice to receive in a volume 100 mL container, and shaving the particles to be horizontal, adjusting the volume of the particles to 100 mL, The weight of only the particles excluding the container was measured. Then, the weight of only the particles was divided by 100 mL of the volume of the particles to obtain an apparent density corresponding to the weight of the particles per unit volume.

(2) Vortex

After adding 50 mL of a 0.9 wt% NaCl solution to a 100 mL beaker, 2 g of the particles prepared in Examples and Comparative Examples were added while stirring at 600 rpm using a stirrer. Then, the time until the vortex of the liquid generated by stirring disappeared and a smooth surface was formed was measured, and the result was expressed as the vortex removal time.

The results are shown in Table 2 below.

Properties	Comparative Example 1	Example 1	Example 2	Example 3	Example 4
Apparent density (g/ml)	0.50	0.48	0.47	0.50	0.48
Vortex (sec)	23.7	24.1	23.0	23.8	24.7

Referring to Table 2, it can be seen that the embodiment of the present invention can improve productivity by reducing the generation of fine powders while realizing existing physical properties.

Claims (16)

1. (A) polymerization step of forming a hydrogel polymer by crosslinking polymerization of a water-soluble ethylenically unsaturated monomer having an acidic group at least partially neutralized in the presence of an internal crosslinking agent and a polymerization initiator; (B) a drying step of drying the hydrogel polymer to prepare a dry polymer; And (C) a grinding step of grinding the dry polymer;

   The (C) grinding step includes (C1) a first grinding step and (C2) a second grinding step of grinding the dry polymer,

   The second grinding step (C2),

   (C21) an abnormal particle classification step of classifying the primary pulverized dry polymer into “abnormal particles” having a particle diameter equal to or larger than the target particle diameter and “normal particles” having a particle diameter smaller than the target particle diameter; And

   (C22) comprising the step of pulverizing the abnormal particles, collecting and crushing only the'abnormal particles',

   Method for producing super absorbent polymer.
2. The method according to claim 1, wherein the grinding step (C) is performed using a continuous multi-stage roll mill and a classifier.
3. The method of claim 1, wherein the second grinding step (C2) is performed one or more times, or two or more times continuously.
4. The method of claim 2, wherein the continuous multi-stage roll mill includes at least two or more stages, and has a structure in which the roll gap width of the roll mill included in each stage narrows from top to bottom.
5. The method of claim 2, wherein the classifier is located at the bottom of the roll mill of each stage.
6. According to claim 1,

   The target particle size is selected from the range of 200 to 850 μm, a method for producing a super absorbent polymer.
7. According to claim 1,

   Before the drying step, a vertical pulverizer, a turbo cutter, a turbo grinder, a rotary cutter mill, a cutter mill, and a disc grinder (Disc mill), shred crusher (Shred crusher), crushers (Crusher), chopper (chopper) and using a disc cutter of any one selected from the group of crushing machine consisting of, cutting the hydrogel polymer, A method for producing a super absorbent polymer comprising a gel grinding step.
8. The method according to claim 1, further comprising the step of collecting the pulverized and classified particles, and classifying the collected particles into normal base resin particles having a particle diameter of 150 to 850 μm, and fine particles smaller than this. Way
9. The method of claim 8,

   A method of manufacturing a superabsorbent polymer further comprising separating the fine particles and reassembling them by adding water to circulate to the drying step.
10. According to claim 1,

    The water-soluble ethylenically unsaturated monomers include acrylic acid, methacrylic acid, maleic anhydride, fumaric acid, crotonic acid, itaconic acid, 2-acryloylethane sulfonic acid, 2-methacryloylethanesulfonic acid, 2-(meth)acryloyl Propanesulfonic acid, or anionic monomers of 2-(meth)acrylamide-2-methyl propane sulfonic acid and salts thereof; (Meth)acrylamide, N-substituted (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, methoxypolyethylene glycol (meth)acrylate or polyethylene glycol ( Nonionic hydrophilic monomers of meth)acrylates; And an amino group-containing unsaturated monomer of (N,N)-dimethylaminoethyl (meth)acrylate or (N,N)-dimethylaminopropyl (meth)acrylamide, and a quaternary product thereof. Method for producing super absorbent polymer.
11. According to claim 1,

    The polymerization initiator is a method for producing a super absorbent polymer comprising a thermal polymerization initiator or a photo polymerization initiator.
12. The method of claim 1, wherein the internal crosslinking agent is N,N'-methylenebisacrylamide, trimethylolpropane 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, hexanediol di( Meth)acrylate, triethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, dipentaerythritol pentaacrylate, glycerin tri(meth)acrylate, A method for producing a superabsorbent polymer of at least one selected from the group consisting of pentaerythritol tetraacrylate, triarylamine, ethylene glycol diglycidyl ether, propylene glycol, glycerin, and ethylene carbonate.
13. A dry polymer input; A crushing unit for pulverizing the introduced dry polymer; And an outlet for discharging the pulverized dry polymer particles;

    The pulverization unit includes a first pulverization unit and a second pulverization unit for pulverizing the introduced dry polymer,

    The second pulverization unit classifies the dry polymer pulverized in the first pulverization unit into'abnormal particles' having a particle diameter equal to or larger than the target particle size and'normal particles' having a particle diameter smaller than the target particle diameter. part; And

    The ‘abnormal particles’ are collected and crushed again.

    A device for producing super absorbent polymers.
14. The method of claim 13,

    An apparatus for producing a super absorbent polymer comprising at least one or more of the second pulverization parts.
15. The method of claim 13,

    The crushing unit includes a roll mill, and has a structure in which the roll gap width in the roll mill forming each stage included in the first crushing unit and the second crushing unit narrows from top to bottom. Resin manufacturing apparatus.
16. The apparatus for manufacturing a superabsorbent polymer according to claim 13, wherein the abnormal particle classification portion is located at a lower end of a roll mill in each stage.

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