KR20230076766A - Preparation method of super absorbent polymer - Google Patents

Abstract

The present invention relates to a method for producing a super absorbent polymer, and more particularly, to a method for producing a super absorbent polymer capable of realizing excellent physical properties related to water absorption by including a cationic polymer as a surface crosslinking agent.

Description

Manufacturing method of super absorbent polymer {PREPARATION METHOD OF SUPER ABSORBENT POLYMER}

The present invention relates to a method for preparing a superabsorbent polymer.

Super Absorbent Polymer (SAP) is a synthetic high-molecular substance that has the ability to absorb moisture 500 to 1,000 times its own weight. Material), etc., are named by different names. The superabsorbent polymer as described above has begun to be put into practical use as sanitary utensils, and now, in addition to sanitary products such as paper diapers for children, soil retaining agents for gardening, water retention materials for civil engineering and construction, sheets for raising seedlings, freshness retainers in the field of food distribution, and It is widely used as a material for steaming.

In most cases, these superabsorbent polymers are widely used in sanitary materials such as diapers and sanitary napkins. In such a sanitary material, it is common that the superabsorbent polymer is included in a spread state in the pulp. However, in recent years, efforts have been made to provide sanitary materials such as diapers with a thinner thickness, and as part of this, the content of pulp is reduced or, furthermore, so-called pulpless diapers in which pulp is not used at all. Development is actively progressing.

As described above, in the case of sanitary materials in which the pulp content is reduced or pulp is not used, the superabsorbent polymer is included in a relatively high ratio, and these superabsorbent polymer particles are inevitably included in multiple layers in the sanitary material. In order for the entire superabsorbent polymer particles included in multiple layers to more efficiently absorb liquid such as urine, the superabsorbent polymer basically needs to exhibit high absorption performance and absorption rate. To this end, a method of crosslinking the surface of the superabsorbent polymer is used.

The surface cross-linking of the super-absorbent polymer is to form a surface cross-linking layer by combining functional groups such as a carboxy group present on the surface of the super-absorbent polymer, and through this, the physical properties of the super-absorbent polymer can be improved. However, when the surface crosslinking layer is formed in this way, physical strength may be increased, but the absorption rate of the superabsorbent polymer may be decreased. Therefore, there is a demand for a method of forming a surface crosslinking layer without impairing the physical properties of the superabsorbent polymer.

An object of the present invention is to provide a method for preparing a super absorbent polymer capable of solving the above problems by using a specific component of a polymer material in forming a surface crosslinking layer of the super absorbent polymer.

Forming a hydrogel polymer by cross-linking polymerization of a water-soluble ethylenically unsaturated monomer having an acidic group at least partially neutralized in the presence of a polymerization initiator and an internal cross-linking agent; forming a base resin powder by drying, pulverizing, and classifying the hydrogel polymer; and a surface crosslinking step of forming a surface crosslinking layer by crosslinking the surface of the base resin powder in the presence of a surface crosslinking agent and a cationic polymer; The cationic polymer provides a method for preparing a superabsorbent polymer including quaternary ammonium ions in repeating units.

In addition, the present invention is a base resin powder comprising a crosslinked polymer of a water-soluble ethylenically unsaturated monomer having an acidic group at least partially neutralized; and a surface cross-linking layer formed on the base resin powder by further cross-linking the cross-linking polymer with a surface cross-linking agent, wherein the surface cross-linking layer comprises a cationic polymer containing quaternary ammonium ions in repeating units. A superabsorbent polymer is provided.

In the present invention, terms such as first and second are used to describe various components, and the terms are used only for the purpose of distinguishing one component from another.

In addition, terms used in this specification are only used to describe exemplary embodiments, and are not intended to limit the present invention.

Singular expressions include plural expressions unless the context clearly dictates otherwise.

In this specification, terms such as "comprise", "comprise" or "having" are used to describe an implemented feature, number, step, component, or combination thereof, and one or more other features, numbers, or steps. , components, combinations or additions thereof are not excluded.

Also, in this specification, when each layer or element is referred to as being formed “on” or “above” each layer or element, it means that each layer or element is formed directly on each layer or element, or other This means that layers or elements may be additionally formed between each layer or on the object or substrate.

Since the present invention can have various changes and various forms, specific embodiments will be exemplified and described in detail below. However, it should be understood that this does not limit the present invention to the specific disclosed form, and includes all modifications, equivalents, and substitutes included in the spirit and technical scope of the present invention.

Throughout this specification, physiological saline means physiological saline (0.9 wt% NaCl(s)).

Hereinafter, the present invention will be described in detail.

According to one aspect of the present invention, cross-linking polymerization of a water-soluble ethylenically unsaturated monomer having an acidic group at least partially neutralized in the presence of a polymerization initiator and an internal cross-linking agent to form a hydrogel polymer; forming a base resin powder by drying, pulverizing, and classifying the hydrogel polymer; and a surface crosslinking step of forming a surface crosslinking layer by crosslinking the surface of the base resin powder in the presence of a surface crosslinking agent and a cationic polymer; The cationic polymer includes a quaternary ammonium ion in a repeating unit, and a method for preparing a superabsorbent polymer is provided.

The inventors of the present invention, in the case of surface crosslinking, which is a process of manufacturing superabsorbent polymer, when a cationic polymer is included in addition to a surface crosslinking agent that has been generally used in the past, physical and chemical properties having a long polymer chain and cations in the molecule are improved. The present invention was completed by discovering that a conventional surface crosslinking agent contributes to the formation of a surface crosslinking layer through the use of the present surface crosslinking agent, thereby maintaining the water retention capacity and absorption rate of the prepared superabsorbent polymer while simultaneously improving the high absorbency and liquid permeability under high pressure.

Hereinafter, the manufacturing method of the superabsorbent polymer of one embodiment will be described in more detail for each step.

For reference, in the present specification, "polymer" or "polymer" means a water-soluble ethylenically unsaturated monomer in a polymerized state, and may cover all moisture content ranges, all particle diameter ranges, and all surface crosslinking states or processing states. . Among the polymers, a polymer having a water content (moisture content) of about 40% by weight or more in a state after polymerization and before drying may be referred to as a hydrous gel polymer. Also, among the above polymers, a polymer having a particle diameter of 150 μm or less may be referred to as “fine powder”.

In addition, "superabsorbent polymer" means the polymer itself, depending on the context, or a condition suitable for commercialization through additional processes such as surface crosslinking, fine powder reassembly, drying, pulverization, classification, etc. It is used to cover everything.

(polymerization)

First, a step of forming a hydrogel polymer is a step of crosslinking polymerization of a water-soluble ethylenically unsaturated monomer having an acidic group at least partially neutralized in the presence of a polymerization initiator and an internal crosslinking agent to form a hydrogel polymer.

The monomer mixture, which is a raw material of the superabsorbent polymer, may include a water-soluble ethylenically unsaturated monomer having an acidic group and at least a portion of the acidic group neutralized, more specifically, an acrylic acid-based monomer and a polymerization initiator.

(monomer)

The acrylic acid-based monomer is a compound represented by Formula 1 below:

[Formula 1]

R ¹ -COOM ¹

In Formula 1,

R ¹ is an alkyl group having 2 to 5 carbon atoms including an unsaturated bond;

M ¹ is a hydrogen atom, a monovalent or divalent metal, an ammonium group, or an organic amine salt.

The acrylic acid-based monomer may include, for example, 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 thereof.

Here, the acrylic acid-based monomer may have an acidic group and at least a portion of the acidic group may be neutralized. Preferably, those obtained by partially neutralizing the monomers with a basic material such as sodium hydroxide, potassium hydroxide, or ammonium hydroxide may be used. At this time, the degree of neutralization of the acrylic acid-based monomer may be adjusted to less than about 70 mol%, or about 40 to about 69 mol%, or about 50 to about 65 mol%.

If the degree of neutralization is too high, neutralized monomers may precipitate, making it difficult for the polymerization to proceed smoothly, and furthermore, the effect of additional neutralization after the start of surface crosslinking is substantially lost, so that the degree of crosslinking of the surface crosslinking layer is not optimized. , the liquid permeability of the superabsorbent polymer may not be sufficient. Conversely, if the degree of neutralization is too low, not only the absorbency of the polymer is greatly reduced, but also exhibits properties such as elastic rubber that are difficult to handle.

The concentration of the monomer may be about 20 to about 60% by weight, or about 30 to about 55% by weight, or about 40 to about 50% by weight based on the monomer mixture including the raw material of the superabsorbent polymer and the solvent. It can be appropriately adjusted in consideration of polymerization time and reaction conditions.

If the concentration of the monomer is too low, the yield of the superabsorbent polymer may be lowered, resulting in problems with economic feasibility. On the contrary, if the concentration of the monomer is too high, a part of the monomer is precipitated or the polymerized water-containing gel polymer is pulverized, the pulverization efficiency Problems in the process, such as lowering the water content, may occur, and physical properties of the superabsorbent polymer may be deteriorated.

(Polymerization initiator)

The polymerization initiator used in the superabsorbent polymer manufacturing method of one embodiment is not particularly limited as long as it is generally used for preparing the superabsorbent polymer.

Specifically, the polymerization initiator may be a thermal polymerization initiator or a photo polymerization initiator according to UV irradiation according to a polymerization method. However, even with the photopolymerization method, a certain amount of heat may be generated by ultraviolet irradiation or the like, and since a certain amount of heat may be generated according to the progress of the polymerization reaction, which is an exothermic reaction, a thermal polymerization initiator may be additionally included.

As the photopolymerization initiator, any compound capable of forming radicals by light such as ultraviolet rays may be used without limitation in its configuration.

Examples of the photopolymerization initiator include benzoin ether, dialkyl acetophenone, hydroxyl alkylketone, phenyl glyoxylate, and benzyl dimethyl ketal. Dimethyl Ketal), acyl phosphine, and alpha-aminoketone (α-aminoketone) may be used at least one selected from the group consisting of. On the other hand, as a specific example of acylphosphine, 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 photoinitiators are well described in 'UV Coatings: Basics, Recent Developments and New Applications (Elsevier 2007)' p115, a book by Reinhold Schwalm, and are not limited to the above examples.

In addition, as the thermal polymerization initiator, at least one selected from the group consisting of a persulfate-based initiator, an azo-based initiator, hydrogen peroxide, and ascorbic acid may be used. Specifically, examples of persulfate-based initiators include sodium persulfate (Na2S2O8), potassium persulfate (K2S2O8), ammonium persulfate ((NH4)2S2O8), and the like, and azo (Azo) Examples of the based initiator include 2, 2-azobis (2-amidinopropane) dihydrochloride, 2, 2-azobis- (N, N-dimethylene) Isobutyramidine dihydrochloride (2,2-azobis-(N, N-dimethylene)isobutyramidine dihydrochloride), 2-(carbamoylazo)isobutylonitril, 2,2-azo Bis[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)) and the like. More various thermal polymerization initiators are well described in Odian's 'Principle of Polymerization (Wiley, 1981)', p203, and are not limited to the above examples.

The polymerization initiator may be added in a concentration of about 0.001 to about 1% by weight, preferably about 0.1 to about 0.9% by weight, based on the total weight of the monomer mixture. If the concentration of the polymerization initiator is too low, the polymerization rate may be slowed and a large amount of residual monomer may be extracted into the final product, which is not preferable. Conversely, when the concentration of the polymerization initiator is higher than the above range, the polymer chain constituting the network is shortened, which is not preferable because the physical properties of the resin may be deteriorated, such as an increase in the content of water-soluble components and a decrease in absorbency under pressure.

(internal cross-linking agent)

According to one embodiment of the invention, the monomer mixture includes an internal crosslinking agent as a raw material of the superabsorbent polymer. Such an internal crosslinking agent is for crosslinking the inside of a polymer in which acrylic acid-based monomers are polymerized, that is, a base resin, and is distinguished from a surface crosslinking agent for crosslinking the surface of the polymer.

The type of internal cross-linking agent is not particularly limited, and any internal cross-linking agent that can be previously used in the preparation of the superabsorbent polymer may be used. Specific examples of such an internal crosslinking agent include a poly(meth)acrylate-based compound of a polyol having 2 to 20 carbon atoms, a polyglycidyl ether-based compound of a polyol having 2 to 20 carbon atoms, or an allyl (meth)acrylate having 2 to 20 carbon atoms. system compounds etc. are mentioned.

More specific examples of these internal crosslinking agents include trimethylolpropane tri(meth)acrylate, ethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, and polypropylene glycol di(meth)acrylate. (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 Acrylate, tripropylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, dipentaerythritol pentaacrylate, glycerin tri(meth)acrylate, pentaerythol tetraacrylate, ethylene glycol deglycy Dill ether (ethyleneglycol diglycidyl ether), polyethylene glycol diglycidyl ether, glycerol polyglycidyl ether, propylene glycol diglycidyl ether or polypropylene glycol diglycidyl ether, and the like, and various other polyfunctional compounds can be used as an internal crosslinking agent.

The internal crosslinking agent is included in a concentration of about 0.01 to about 1% by weight, or about 0.05 to about 0.8% by weight, or about 0.2 to about 0.7% by weight based on the total weight of the monomer mixture, and the hydrogel polymer and the resulting product therefrom A cross-linked structure can be introduced into the base resin powder.

If the concentration of the internal crosslinking agent is too low, the absorption rate of the superabsorbent polymer may be lowered and the gel strength may be weakened, which is undesirable. Conversely, if the concentration of the internal cross-linking agent is too high, the absorbency of the superabsorbent polymer is lowered, making it undesirable as an absorbent.

(other additives and monomer mixtures)

In addition, the monomer mixture may further include, in some cases, a foaming agent and a foam stabilizer.

The foaming agent serves to form pores in the hydrogel polymer by foaming in the monomer mixture during polymerization, thereby increasing the surface area of the hydrogel polymer.

Carbonate may be used as the foaming agent, for example, sodium bicarbonate, sodium carbonate, potassium bicarbonate, potassium carbonate, calcium bicarbonate, calcium Calcium bicarbonate, magnesium bicarbonate, or magnesium carbonate may be used.

In addition, the foaming agent is preferably used in an amount of 1500 ppmw or less, or about 1300 ppmw or less, based on the weight of the water-soluble ethylenically unsaturated monomer. If the amount of the foaming agent is too large, pores may be too large, resulting in a decrease in gel strength and a low density of the superabsorbent polymer, which may cause problems in distribution and storage. In addition, the foaming agent is preferably used in an amount of 500 ppmw or more, or 1000 ppmw or more, based on the weight of the water-soluble ethylenically unsaturated monomer.

Meanwhile, in the manufacturing method of the above-described embodiment, the monomer mixture may further include additives such as a thickener, a plasticizer, a storage stabilizer, and an antioxidant, if necessary.

The monomer mixture comprising the aforementioned monomer mixture, a polymerization initiator, an internal crosslinking agent, and a water-soluble ethylenically unsaturated monomer having at least a partially neutralized acidic group and, optionally, other additives, is in the form of a monomer mixture solution dissolved in a solvent can be prepared with

The solvent that can be used at this time can be used without limitation in composition as long as it can dissolve the above-mentioned components, and for example, 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 At least one selected from ethyl ether, toluene, xylene, butyrolactone, carbitol, methyl cellosolve acetate, and N,N-dimethylacetamide may be used in combination.

The solvent may be included in a residual amount so that each component is adjusted to the above-described concentration range with respect to the total content of the monomer mixture.

(polymerization)

Meanwhile, a method of forming a hydrogel polymer by thermal polymerization or photopolymerization of such a monomer mixture is also not particularly limited as long as it is a commonly used polymerization method.

Specifically, the polymerization method can be largely divided into thermal polymerization and photopolymerization according to the polymerization energy source.

In general, when thermal polymerization is performed, it may be performed in a reactor having an agitation shaft such as a kneader, and when light polymerization is performed, it may be performed in a reactor equipped with a movable conveyor belt. And, the present invention is not necessarily limited to the polymerization method described above.

For example, as described above, the hydrogel polymer obtained by thermal polymerization by supplying hot air to a reactor such as a kneader equipped with an agitation shaft or heating the reactor may be obtained according to the shape of the agitation shaft provided in the reactor. , can be in the form of a few centimeters to a few millimeters. Specifically, the size of the obtained hydrogel polymer may vary depending on the concentration and injection speed of the monomer mixture to be injected, and a hydrogel polymer having a weight average particle diameter of 2 to 50 mm or 3 to 30 mm may be obtained. there is.

In addition, as described above, when photopolymerization is performed in a reactor equipped with a movable conveyor belt, the form of a hydrogel polymer usually obtained may be in the form of a sheet having the width of a belt. At this time, the thickness of the polymer sheet may vary depending on the concentration and injection speed of the injected monomer mixture, and the monomer mixture is supplied so that a hydrogel polymer on a sheet having a thickness of usually 0.5 to 5 cm or 1 to 3 cm can be obtained. It is desirable to do

When the monomer mixture is supplied to such an extent that the thickness of the polymer on the sheet is too thin, production efficiency is low, which is undesirable, and when the thickness of the polymer on the sheet exceeds 5 cm, the polymerization reaction does not occur evenly over the entire thickness due to the excessively thick thickness. may not be

A typical moisture content of the hydrogel polymer obtained in this way may be about 40 to about 80% by weight, or about 50 to about 70% by weight. Meanwhile, throughout the present specification, "moisture content" refers to a value obtained by subtracting the weight of the dry polymer from the weight of the hydrogel polymer as the content of moisture with respect to the total weight of the hydrogel polymer.

Specifically, it is defined as a value calculated by measuring the weight loss due to evaporation of water in the polymer in the process of raising the temperature of the polymer through infrared heating and drying. At this time, the drying condition is a method in which the temperature is raised from room temperature to about 180 ° C and then maintained at about 180 ° C, the total drying time is set to about 20 minutes including about 5 minutes of the temperature raising step, and the moisture content is measured.

(dry)

Next, a step of drying the obtained hydrogel polymer is performed.

In this case, if necessary, a step of coarsely pulverizing may be further performed before drying to increase the efficiency of the drying step.

At this time, the grinder used is not limited in configuration, but specifically, a vertical pulverizer, a turbo cutter, a turbo grinder, a rotary cutter mill, a cutting Includes any one selected from the group of crushing devices consisting of a cutter mill, a disc mill, a shred crusher, a crusher, a chopper, and a disc cutter However, it is not limited to the above example.

At this time, in the pulverization step, the hydrogel polymer may be pulverized so that the particle size is about 2 to about 10 mm, or about 3 to about 8 mm. The particle size of the hydrogel polymer may be defined as the longest distance among straight line distances connecting arbitrary points on the surface of the hydrogel polymer.

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 also may cause agglomeration of the pulverized particles. On the other hand, when the particle diameter is greater than about 10 mm, the effect of increasing the efficiency of the subsequent drying step is insignificant.

Drying is performed on the hydrogel polymer immediately after polymerization that has been pulverized or not subjected to the pulverization step as described above.

At this time, the drying temperature of the drying step may be about 150 to about 250 ℃. When the drying temperature is less than about 150° C., the drying time may be excessively long and the physical properties of the superabsorbent polymer finally formed may deteriorate. When the drying temperature exceeds about 250 °C, only the surface of the polymer is excessively dried, and fine particles may be generated in a subsequent pulverization process, and physical properties of the finally formed superabsorbent polymer may be deteriorated. Accordingly, the drying may be performed at a temperature of about 150 to about 200 °C, more preferably at about 160 to 180 °C.

Meanwhile, the drying time may be about 20 to about 90 minutes, or about 30 to about 70 minutes in consideration of process efficiency, but is not limited thereto.

As long as the drying method of the drying step is also commonly used as a drying process for hydrogel polymers, the composition may be used without limitation. Specifically, the drying step may be performed by a method such as hot air supply, infrared ray irradiation, microwave irradiation, or ultraviolet ray irradiation.

The moisture content of the polymer after such a drying step may be about 0.1 to about 10% by weight, or about 1 to about 8% by weight. If the moisture content after drying is too low, the hydrogel polymer may deteriorate during the drying process and the physical properties of the super absorbent polymer may deteriorate. progress can be difficult.

Next, a step of pulverizing the dried polymer obtained through such a drying step is performed.

The polymer powder obtained after the grinding step may have a particle size of about 150 to about 850 μm. The grinder used for grinding to such a particle size is specifically, a pin mill, a hammer mill, a screw mill, a roll mill, a disc mill, or A jog mill or the like may be used, but the invention is not limited to the above example.

In addition, in order to manage the physical properties of the superabsorbent polymer powder to be finalized after the pulverization step, a separate process of classifying the polymer powder obtained after pulverization according to the particle size may be performed, and the polymer powder is prepared at a certain weight ratio according to the particle size range. can be classified so that

(surface cross-linking)

The surface crosslinking step is a step of forming a superabsorbent polymer having more improved physical properties by inducing a crosslinking reaction on the surface of the pulverized polymer in the presence of a surface crosslinking solution containing a surface crosslinking agent. Through this surface cross-linking, a surface cross-linking layer is formed on the surface of the pulverized and classified base resin powder.

Generally, since a surface crosslinking agent is applied to the surface of the base resin powder, a surface crosslinking reaction takes place on the surface of the base resin powder, which improves the crosslinkability on the surface of the particle without substantially affecting the inside of the particle. Therefore, the surface-crosslinked superabsorbent polymer particles have a higher degree of crosslinking near the surface than inside because the crosslinked polymer on the surface of the base resin powder is additionally crosslinked.

On the other hand, as the surface crosslinking agent, a compound capable of reacting with a functional group of the base resin is used, and for example, polyhydric alcohol-based compounds, polyvalent epoxy-based compounds, haloepoxy compounds, or alkylene carbonate-based compounds can be used without any particular limitation. there is.

Specifically, examples of the polyhydric alcohol compound include di-, tri-, tetra- or polyethylene glycol, 1,3-propanediol, dipropylene glycol, 2,3,4-trimethyl-1,3-pentanediol, polypropylene glycol, glycerol, polyglycerol, 2-butene-1,4-diol, 1,4-butanediol, 1,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, and 1,2-cyclohexane At least one selected from the group consisting of dimethanol may be used.

In addition, polyvalent epoxy-based compounds include ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, triethylene glycol diglycidyl ether, tetra At least one selected from the group consisting of ethylene glycol diglycidyl ether, glycerin polyglycidyl ether, and sorbitol polyglycidyl ether may be used. .

In addition, as the haloepoxy compound, epichlorohydrin, epibromohydrin, and α-methylepichlorohydrin may be used. Meanwhile, as the mono-, di- or polyoxazolidinone compound, for example, 2-oxazolidinone or the like can be used.

In addition, ethylene carbonate or propylene carbonate may be used as the alkylene carbonate-based compound. These may be used alone or in combination with each other.

The superabsorbent polymer manufacturing method of the present invention further includes a cationic polymer in addition to the general surface crosslinking agent described above. The cationic polymer means a material having a cation in the main chain or side chain of the molecule. When a surface crosslinking reaction is performed by adding a cationic polymer together with a surface crosslinking agent, it is possible to maintain high absorbency under pressure while maintaining water retention even at a high crosslinking density due to the interaction between ions present in the polymer and the existing surface crosslinking agent. In addition, liquid permeability may also be improved by evenly surface-treating the surface of the base resin.

Meanwhile, the cationic polymer may have one or more cations selected from the group consisting of ammonium, imidazolium, pyridinium, phosphonium, and sulfonium. Preferably, the cationic polymer contains cations in repeating units, more preferably, ammonium ion groups in repeating units. The ammonium ion may be classified into primary to quaternary ammonium ions according to the number of hydrogens in the ammonium ion substituted with organic groups. For example, the cationic polymer may include quaternary ammonium ions in repeating units, but the present invention is not necessarily limited thereto.

According to one embodiment of the present invention, the cationic polymer may include repeating units derived from ethylenically unsaturated monomers to which ammonium ions are linked. For example, the ethylenically unsaturated monomers may be (meth)acrylic acid, (meth)acrylates, (meth)acrylamides, vinyl acetate, ethylene, propylene, butadiene, and styrene. In addition, the ammonium ion may be directly bonded to the ethylenically unsaturated monomer-derived repeating unit or bonded through C _1-10 alkylene.

Also, according to one embodiment of the present invention, the cationic polymer may include cyclic ammonium ions in repeating units. The cyclic ammonium ion refers to a structure in which at least two or more organic groups substituted for ammonium ions are bonded to each other to form a ring. In addition, the cyclic ammonium ion may be a form in which a monomer of a cationic polymer is converted to a cyclic form during polymerization, or a monomer of the cationic polymer may include a cyclic ammonium ion.

The cationic polymer is specifically, for example, poly(diallyldimethylammonium chloride), poly(2-(methacryloyloxy)ethyltrimethylammonium methylsulfate), poly(2-dimethylamino)ethyl methacrylate methyl chloride quaternary salt), and poly(acrylamide-dimethylaminoethyl acrylate quaternary salt). Meanwhile, the poly(diallyldimethylammonium chloride) includes a repeating unit represented by Formula 1, and the poly(2-(methacryloyloxy)ethyltrimethylammonium methyl sulfate) is a repeating unit represented by Formula 2 below It is a compound containing

[Formula 1]

[Formula 2]

Preferably, the cationic polymer may have a weight average molecular weight of 50,000 g/mol to 700,000 g/mol, more preferably 80,000 g/mol to 600,000 g/mol, or 100,000 g/mol to 500,000 g/mol. there is. When the weight average molecular weight of the cationic polymer satisfies the above range, it is suitable for coating the base resin through interaction with an existing surface crosslinking agent, and thus various physical properties of absorption can be improved.

Preferably, the cationic polymer may be included in an amount of 0.01 to 0.9 parts by weight based on 100 parts by weight of the base resin. More preferably, it may be included in 0.3 parts by weight to 0.8 parts by weight, or 0.05 parts by weight to 0.5 parts by weight based on 100 parts by weight of the base resin. When the cationic polymer is included in the above range, it is suitable for surface treatment of the base resin and can improve high pressure absorption capacity and liquid permeability at the same time.

Meanwhile, the content of the surface crosslinking agent may be appropriately selected depending on the type of the surface crosslinking agent added or reaction conditions, but is usually about 0.001 part by weight to about 5 parts by weight, or about 100 parts by weight of the base resin powder. 0.005 parts by weight to about 2 parts by weight, or about 0.01 parts by weight to about 1 parts by weight, or about 0.02 parts by weight to about 0.5 parts by weight may be used. If the content of the surface crosslinking agent is too small, the surface crosslinking reaction hardly occurs, and if the content of the surface crosslinking agent is too large, basic absorption properties such as water retention may be deteriorated due to excessive progress of the surface crosslinking reaction.

When adding the surface crosslinking agent, water may be additionally mixed together and added in the form of a surface crosslinking solution. When water is added, there is an advantage in that the surface crosslinking agent can be evenly dispersed in the base resin. At this time, the amount of water added is about 1 weight based on 100 parts by weight of the base resin for the purpose of inducing uniform dispersion of the surface crosslinking agent, preventing aggregation of the base resin powder, and at the same time optimizing the surface penetration depth of the surface crosslinking agent It is preferably added in a proportion of about 1 part to about 10 parts by weight.

On the other hand, the above-described surface crosslinking liquid, in addition to the cationic polymer, includes at least one inorganic material selected from the group consisting of silica, clay, alumina, silica-alumina composite, titania, zinc oxide, and aluminum sulfate. A surface cross-linking reaction may be performed by further addition. The inorganic material may be used in a powder form or a liquid form, and in particular, may be used as an alumina powder, a silica-alumina powder, a titania powder, or a nano-silica solution. In addition, the inorganic material may be used in an amount of about 0.05 parts by weight to about 2 parts by weight based on 100 parts by weight of the base resin.

In addition, in the surface crosslinking process, the surface crosslinking structure of the superabsorbent polymer can be further optimized by adding a polyvalent metal cation instead of or together with the inorganic material to perform surface crosslinking. This is expected because such a metal cation can further reduce the crosslinking distance by forming a chelate with the carboxy group (COOH) of the superabsorbent polymer.

In addition, there is no limitation on the configuration of the method for adding the inorganic material and/or polyvalent metal cation to the base resin powder as necessary. For example, a method of mixing the surface crosslinking agent and base resin powder in a reaction tank, spraying the surface crosslinking agent, etc. on the base resin powder, continuously supplying and mixing the base resin powder and surface crosslinking agent, etc. to a continuously operated mixer method, etc. can be used.

When adding the surface crosslinking agent, water and methanol may be further mixed together and added. When water and methanol are added, there is an advantage in that the surface crosslinking agent can be evenly dispersed in the base resin powder. At this time, the content of added water and methanol can be appropriately adjusted to induce uniform dispersion of the surface crosslinking agent, prevent aggregation of the base resin powder, and optimize the surface penetration depth of the surface crosslinking agent.

Meanwhile, a surface modification step is performed on the base resin powder by applying heat to a mixture of the base resin powder and the surface crosslinking liquid to raise the temperature.

The surface crosslinking step may be performed under well-known conditions depending on the type of surface crosslinking agent, for example, at a temperature of about 140 °C to about 200 °C for about 20 minutes to about 60 minutes. In a more specific example, the surface crosslinking step is performed by adding a surface crosslinking agent and the like to the base resin powder having an initial temperature of about 20 ° C to about 80 ° C, and then about 140 ° C to about 140 ° C over about 30 minutes. Heat treatment may be performed by raising the temperature to a maximum temperature of 200 °C, or about 175 °C to about 195 °C, and maintaining the maximum temperature for about 5 minutes to about 60 minutes.

Depending on the surface cross-linking conditions, the basic absorption characteristics of the superabsorbent polymer, such as water retention capacity, and liquid permeability and/or absorbency under pressure may be optimized together.

The means for raising the temperature for the surface crosslinking reaction is not particularly limited. It can be heated by supplying a heat medium or directly supplying a heat source. At this time, as the type of heat medium that can be used, high-temperature fluids such as steam, hot air, and hot oil can be used, but are not limited thereto, and the temperature of the heat medium supplied is determined by the means of the heat medium, the temperature increase rate, and the temperature rise It can be selected appropriately in consideration of the target temperature. On the other hand, as a heat source directly supplied, heating through electricity and heating through gas may be mentioned, but the present invention is not limited to the above-described examples.

(super absorbent polymer)

Meanwhile, the manufacturing method may further include a step of classifying a base resin made of a crosslinked polymer having the surface crosslinked layer formed thereon.

The physical properties of the superabsorbent polymer powder to be finalized can be managed through the step of classifying the base resin made of the crosslinked polymer on which the surface crosslinking layer is formed according to the particle size. Through such processes such as pulverization and classification, it is appropriate to manufacture and provide the superabsorbent polymer obtained therefrom to have a particle size of about 150 to 850 μm. More specifically, about 90% by weight, preferably at least 95% by weight of the base resin on which the surface crosslinking layer is formed has a particle diameter of about 150 to 850 μm, and about 3% by weight of fine powder having a particle diameter of less than about 150 μm can be less than

As the particle size distribution of the super absorbent polymer is adjusted within a desirable range, the finally prepared super absorbent polymer may exhibit excellent water absorption properties. Therefore, in the classification step, a polymer having a particle diameter of about 150 to about 850 μm may be classified and commercialized.

On the other hand, the present invention is a base resin powder comprising a crosslinked polymer of water-soluble ethylenically unsaturated monomers having an acidic group at least partially neutralized; and a surface cross-linking layer formed on the base resin powder by further cross-linking the cross-linking polymer with a surface cross-linking agent, wherein the surface cross-linking layer comprises a cationic polymer containing quaternary ammonium ions in repeating units. A superabsorbent polymer is provided.

As described above, the superabsorbent polymer according to the manufacturing method of the present invention includes a surface crosslinking layer in which the cationic polymer is distributed in the surface crosslinking structure of the surface of the base resin by adding the cationic polymer in the surface crosslinking step. Description of the surface cross-linking agent including the cationic polymer constituting the surface cross-linking layer is as described above.

According to one embodiment of the present invention, the cationic polymer may include repeating units derived from ethylenically unsaturated monomers to which ammonium ions are linked. For example, the ethylenically unsaturated monomers may be (meth)acrylic acid, (meth)acrylates, (meth)acrylamides, vinyl acetate, ethylene, propylene, butadiene, and styrene. In addition, the ammonium ion may be directly bonded to the ethylenically unsaturated monomer-derived repeating unit or bonded through C _1-10 alkylene.

Also, according to one embodiment of the present invention, the cationic polymer may include cyclic ammonium ions in repeating units. The cyclic ammonium ion refers to a structure in which at least two or more organic groups substituted for ammonium ions are bonded to each other to form a ring. In addition, the cyclic ammonium ion may be a form in which a monomer of a cationic polymer is converted to a cyclic form during polymerization, or a monomer of the cationic polymer may include a cyclic ammonium ion.

Preferably, the cationic polymer is poly(diallyldimethylammonium chloride), poly(2-(methacryloyloxy)ethyltrimethylammonium methyl sulfate), poly(2-dimethylamino)ethyl methacrylate methylchloride 4 grade salt), and poly (acrylamide-dimethylaminoethyl acrylate quaternary salt) may include any one or more selected from the group consisting of.

Preferably, as the surface crosslinking agent, a compound capable of reacting with a functional group of a base resin is used, and for example, polyhydric alcohol-based compounds, polyvalent epoxy-based compounds, haloepoxy compounds, or alkylene carbonate-based compounds are all without particular limitation. can be used

Examples of specific polyhydric alcohol-based compounds, polyhydric epoxy-based compounds, haloepoxy compounds, or alkylene carbonate-based compounds are as described above, and examples include di-, tri-, tetra- or polyethylene glycol, 1,3-propanediol , dipropylene glycol, 2,3,4-trimethyl-1,3-pentanediol, polypropylene glycol, glycerol, polyglycerol, 2-butene-1,4-diol, 1,4-butanediol, 1,3-butanediol , 1,5-pentanediol, 1,6-hexanediol, 1,2-cyclohexanedimethanol, ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, triethylene glycol diglycidyl ether, Tetraethylene glycol diglycidyl ether, glycerin polyglycidyl ether, sorbitol polyglycidyl ether, ethylenediamine, diethylenetriamine, triethylenetetraamine, tetraethylenepentamine, pentaethylenehexamine, polyethyleneimine, poly amide polyamine, epichlorohydrin, epibromohydrin and α-methylepichlorohydrin, 2-oxazolidinone, ethylene carbonate, and propylene carbonate.

Based on this, the superabsorbent polymer of the present invention, due to the surface crosslinked layer formed on the base resin, was able to improve the absorbency under pressure while maintaining the water retention capacity, and could realize excellent high absorbency under pressure and liquid permeability even at a high crosslinking density. can

The term "CRC (Centrifugal Retention Capacity)" used in the present invention is also called centrifugal retention capacity, and means the amount of solution that can be absorbed under no load. The CRC can be measured according to EDANA WSP 241.3, and a specific measurement method is described in detail in the following examples. Preferably, the CRC of the superabsorbent polymer is 25 g/g to 40 g/g, or 30 g/g to 35 g/g.

The term "AUP (Absorbency Under Pressure)" used in the present invention is also referred to as absorbency under pressure, and means the amount of a solution that can be absorbed under a certain pressure (0.7 psi). The AUP can be measured according to the EDANA method WSP 242.3, and the specific measurement method is described in detail in the following examples. Preferably, the AUP of the superabsorbent polymer is 10 g/g to 30 g/g. More preferably, the AUP of the superabsorbent polymer is 13 g/g to 25 g/g.

The term “EFFC” used in the present invention is also referred to as effective absorption capacity, and the effective absorption capacity (EFFC) can be obtained by substituting the water retention capacity (CRC) and the 0.7 psi absorbency under pressure (AUP) into the following formula 3:

[Calculation 3]

Effective Absorption Capacity = {Retaining Capacity (CRC) + 0.7 psi Absorbency Under Pressure (AUP)}/2

Preferably, the EFFC of the superabsorbent polymer is 22 g/g to 30 g/g. More preferably, the superabsorbent polymer has an EFFC of 23 g/g to 28 g/g, or 25 g/g to 28 g/g.

The term "Vortex" used in the present invention is also called absorption rate, and means the rate at which a solution is absorbed into the superabsorbent polymer. The specific measurement method of the vortex is described in detail in the following examples. Preferably, the vortex of the superabsorbent polymer is 40 seconds or less. More preferably, the Vortex of the superabsorbent polymer is 35 seconds or less, 30 seconds or less, or 25 seconds or less. On the other hand, the lower the value of the vortex is, the better it is, and the theoretical lower limit is 0 seconds. For example, the vortex of the superabsorbent polymer is 10 seconds or more, 15 seconds or more, or 20 seconds or more.

The term "permeability" used in the present invention means the ability to rapidly transfer a solution absorbed in a super absorbent polymer to another super absorbent polymer, that is, the mobility of a solution within the super absorbent polymer. On the other hand, the specific measuring method of liquid permeability is described in detail in the following examples. Preferably, the permeability of the superabsorbent polymer is 18 seconds or less. More preferably, the permeability of the superabsorbent polymer is 17 seconds or less, 16 seconds or less, or 15 seconds or less. Meanwhile, the lower the value, the better the permeability, so the theoretical lower limit is 0 seconds. For example, the permeability of the superabsorbent polymer is 3 seconds or more, 5 seconds or more, or 10 seconds or more. .

In addition, the superabsorbent polymer of the present invention includes at least one or more of the physical property ranges of water retention capacity (CRC), absorbency under pressure (AUP), effective absorption capacity (EFFC), absorption rate (vortex), and permeability described above, Preferably, two or more are satisfied, and more preferably, all physical property ranges may be satisfied simultaneously.

According to the manufacturing method of the superabsorbent polymer of the present invention described above, a cationic polymer may be added during surface crosslinking to prepare a superabsorbent polymer having excellent water absorption properties even at a high crosslinking density.

Hereinafter, the action and effect of the invention will be described in more detail through specific examples of the invention. However, these embodiments are only presented as examples of the invention, and the scope of the invention is not determined thereby.

<Preparation of base resin>

manufacturing example

100 g of acrylic acid, 3.0 g of polyethylene glycol diacrylate (PEGDA, MW = 523) as a crosslinking agent, 0.008 g of phenylbis (2, 4, 6-trimethylbenzoyl) phosphine oxide as a photoinitiator, sodium persulfate as a thermal initiator A monomer aqueous solution composition was prepared by mixing 0.08 g of SPS), 128 g of 31.5% caustic soda (NaOH), and 63.5 g of water.

A photopolymerization reaction was performed on the monomer aqueous solution composition to obtain a polymerized sheet. After taking out the polymerized sheet and cutting it into a size of 3 cm X 3 cm, a chopping process was performed using a meat chopper to prepare crumbs. The crumb was dried in an oven capable of transferring air volume up and down. Hot air at 185 ° C. was flowed from the bottom to the top for 15 minutes and from the top to the bottom for 15 minutes to uniformly dry, and after drying, the water content of the dried body was set to 2% or less.

After drying, it was pulverized with a grinder, and then classified at an Amplitude of 1.5 mm for 10 minutes (classification mesh combination: #20#30#50#100), and each classification (10%/65%/22%/3%) was collected. Thus, a base resin powder having a particle size of about 150 μm to 850 μm was obtained.

<Manufacture of superabsorbent polymer>

Comparative Example 1

A surface crosslinking solution (5 parts by weight of water, 3 parts by weight of methanol, 0.06 parts by weight of ethylene glycol diglycidyl ether (EJ1030s, n = 1)) was evenly mixed with 100 parts by weight of the base resin powder prepared in the above Preparation Example. After that, a surface crosslinking reaction was performed at 140 °C for 30 minutes. Then, silica (Aerosil200, 0.1 part by weight) was added and mixed. After the surface treatment was completed, a superabsorbent polymer having an average particle diameter of 850 μm or less was prepared using a sieve.

Example 1

100 parts by weight of the base resin powder prepared in Preparation Example, surface crosslinking solution (5 parts by weight of water, 3 parts by weight of methanol, 0.06 parts by weight of ethylene glycol diglycidyl ether (EJ1030s, n = 1), poly(diallyl) Dimethylammonium chloride) (manufacturer: SINOFLOC, Mw: 150,000 g/mol) 0.1 part by weight) was evenly mixed, and then a surface crosslinking reaction was performed at 140° C. for 30 minutes. Then, silica (Aerosil200, 0.1 part by weight) was added and mixed. After the surface treatment was completed, a superabsorbent polymer having an average particle diameter of 850 μm or less was prepared using a sieve.

Example 2

100 parts by weight of the base resin powder prepared in Preparation Example, surface crosslinking solution (5 parts by weight of water, 3 parts by weight of methanol, 0.06 parts by weight of ethylene glycol diglycidyl ether (EJ1030s, n = 1), poly(2- After evenly mixing (methacryloyloxy)ethyltrimethylammonium methyl sulfate (manufacturer: Senka, Mw: 400,000 g/mol) 0.1 parts by weight), a surface crosslinking reaction was performed at 140 ° C. for 30 minutes. (Aerosil200, 0.1 part by weight) was added and mixed After the surface treatment was completed, a superabsorbent polymer having an average particle diameter of 850 μm or less was prepared using a sieve.

Comparative Example 2

100 parts by weight of the base resin powder prepared in the above Preparation Example was evenly mixed with a surface crosslinking solution (7 parts by weight of water, 3 parts by weight of methanol, 0.025 parts by weight of ethylene glycol diglycidyl ether (EJ1030s, n = 1)) After that, a surface crosslinking reaction was performed at 140 °C for 30 minutes. Then, silica (Aerosil200, 0.1 part by weight) was added and mixed. After the surface treatment was completed, a superabsorbent polymer having an average particle diameter of 850 μm or less was prepared using a sieve.

Example 3

100 parts by weight of the base resin powder prepared in Preparation Example, surface crosslinking solution (7 parts by weight of water, 3 parts by weight of methanol, 0.025 parts by weight of ethylene glycol diglycidyl ether (EJ1030s, n = 1), poly(2- After evenly mixing (methacryloyloxy)ethyltrimethylammonium methyl sulfate (manufacturer: Senka, Mw: 400,000 g/mol) 0.05 parts by weight), a surface crosslinking reaction was performed at 140 ° C. for 30 minutes. (Aerosil200, 0.1 part by weight) was added and mixed After the surface treatment was completed, a superabsorbent polymer having an average particle diameter of 850 μm or less was prepared using a sieve.

Example 4

100 parts by weight of the base resin powder prepared in Preparation Example, surface crosslinking solution (7 parts by weight of water, 3 parts by weight of methanol, 0.025 parts by weight of ethylene glycol diglycidyl ether (EJ1030s, n = 1), poly(2- After evenly mixing (methacryloyloxy)ethyltrimethylammonium methyl sulfate (manufacturer: Senka, Mw: 400,000 g/mol) 0.1 parts by weight), a surface crosslinking reaction was performed at 140 ° C. for 30 minutes. (Aerosil200, 0.1 part by weight) was added and mixed After the surface treatment was completed, a superabsorbent polymer having an average particle diameter of 850 μm or less was prepared using a sieve.

Example 5

100 parts by weight of the base resin powder prepared in Preparation Example, surface crosslinking solution (7 parts by weight of water, 3 parts by weight of methanol, 0.025 parts by weight of ethylene glycol diglycidyl ether (EJ1030s, n = 1), poly(2- After evenly mixing (methacryloyloxy)ethyltrimethylammonium methyl sulfate (manufacturer: Senka, Mw: 400,000 g/mol) 0.2 parts by weight), a surface crosslinking reaction was performed at 140 ° C. for 30 minutes. (Aerosil200, 0.1 part by weight) was added and mixed After the surface treatment was completed, a superabsorbent polymer having an average particle diameter of 850 μm or less was prepared using a sieve.

Example 6

100 parts by weight of the base resin powder prepared in Preparation Example, surface crosslinking solution (7 parts by weight of water, 3 parts by weight of methanol, 0.035 parts by weight of ethylene glycol diglycidyl ether (EJ1030s, n = 1), poly(2- After evenly mixing (methacryloyloxy)ethyltrimethylammonium methyl sulfate (manufacturer: Senka, Mw: 400,000 g/mol) 0.2 parts by weight), a surface crosslinking reaction was performed at 140 ° C. for 30 minutes. (Aerosil200, 0.1 part by weight) was added and mixed After the surface treatment was completed, a superabsorbent polymer having an average particle diameter of 850 μm or less was prepared using a sieve.

Example 7

100 parts by weight of the base resin powder prepared in Preparation Example, surface crosslinking solution (7 parts by weight of water, 3 parts by weight of methanol, 0.035 parts by weight of ethylene glycol diglycidyl ether (EJ1030s, n = 1), poly(2- After evenly mixing (methacryloyloxy)ethyltrimethylammonium methyl sulfate (manufacturer: Senka, Mw: 400,000 g/mol) 0.3 parts by weight), a surface crosslinking reaction was performed at 140 ° C. for 30 minutes. (Aerosil200, 0.1 part by weight) was added and mixed After the surface treatment was completed, a superabsorbent polymer having an average particle diameter of 850 μm or less was prepared using a sieve.

Comparative Example 3

100 parts by weight of the base resin powder prepared in Preparation Example, surface crosslinking solution (5 parts by weight of water, 3 parts by weight of methanol, 0.06 parts by weight of ethylene glycol diglycidyl ether (EJ1030s, n = 1), polyethyleneimine (manufacturer : Polysciences, Inc., Mw: 100,000 g/mol) 0.1 part by weight) was evenly mixed, and then a surface crosslinking reaction was performed at 140° C. for 30 minutes. Then, silica (Aerosil200, 0.1 part by weight) was added and mixed. After the surface treatment was completed, a superabsorbent polymer having an average particle diameter of 850 μm or less was prepared using a sieve.

Comparative Example 4

A surface crosslinking solution (7 parts by weight of water, 3 parts by weight of methanol, 0.035 parts by weight of ethylene glycol diglycidyl ether (EJ1030s, n = 1)) was evenly mixed with 100 parts by weight of the base resin powder prepared in the above Preparation Example. After that, a surface crosslinking reaction was performed at 140 °C for 30 minutes. Then, poly(2-(methacryloyloxy)ethyltrimethylammonium methyl sulfate (manufacturer: Senka, Mw: 400,000 g/mol, 0.3 parts by weight) and silica (Aerosil200, 0.1 parts by weight) were added and mixed. After the surface treatment was completed, a superabsorbent polymer having an average particle diameter of 850 μm or less was prepared using a sieve.

Experimental example

With respect to the superabsorbent polymer obtained in the above Examples and Comparative Examples, each physical property was measured by the following method.

Unless otherwise indicated, evaluation of the physical properties of the superabsorbent polymer was performed on a resin having a particle size of 150 μm to 850 μm classified through an ASTM standard sieve.

(1) CRC

The water retention capacity by water absorption capacity under no load of each resin was measured according to EDANA WSP 241.3.

Specifically, the superabsorbent polymer W ₀ (g) (about 0.2 g) is uniformly placed in a bag made of nonwoven fabric, sealed, and then immersed in physiological saline (0.9% by weight) at room temperature (23 ° C to 25 ° C). made it After 30 minutes, water was drained from the bag for 3 minutes under the condition of 250 G using a centrifuge, and the mass W ₂ (g) of the bag was measured. In addition, after performing the same operation without using the superabsorbent polymer, the mass W ₁ (g) at that time was measured. Using each obtained mass, CRC (g/g) was calculated according to the following equation.

[Calculation 1]

CRC (g/g) = {[W ₂ (g) - W ₁ (g)]/W ₀ (g)} - 1

(2) 0.7 AUP

The absorbency under pressure of 0.7 psi of the superabsorbent polymer was measured according to the EDANA method WSP 242.3.

First, in measuring the absorbency under pressure, the resin classification in the CRC measurement was used.

Specifically, a stainless steel 400 mesh wire mesh was mounted on the bottom of a plastic cylinder with an inner diameter of 25 mm. Super absorbent polymer W ₀ (g) (0.16 g) was uniformly sprayed and the piston, which could further apply a load of 0.7 psi uniformly thereon, had an outer diameter slightly smaller than 25 mm, had no gaps with the inner wall of the cylinder, and did not interfere with vertical movement. At this time, the weight W ₃ (g) of the device was measured.

A glass filter having a diameter of 90 mm and a thickness of 5 mm was placed on the inside of a petro dish having a diameter of 150 mm, and physiological saline solution composed of 0.9% by weight sodium chloride was leveled with the upper surface of the glass filter. One sheet of filter paper having a diameter of 90 mm was placed thereon. The measuring device was placed on a filter paper, and the liquid was absorbed for 1 hour under a load. After 1 hour, the measuring device was lifted up and its weight W ₄ (g) was measured.

Using each obtained mass, the absorbency under pressure (g/g) was calculated according to the following formula.

[Calculation 2]

AUP(g/g) = [W ₄ (g) - W ₃ (g)]/W ₀ (g)

(3) EFFCs

The effective absorption capacity (EFFC) was obtained by substituting the water retention capacity (CRC) measured in (1) and the 0.7 psi absorbency under load (AUP) measured in (2) above into Equation 3 below.

[Calculation 3]

Effective Absorption Capacity = {Retaining Capacity (CRC) + 0.7 psi Absorbency Under Pressure (AUP)}/2

(4) Vortex

The absorption rate was measured according to the Japanese standard method (JIS K 7224).

Specifically, 2 g of superabsorbent polymer was added to 50 mL of physiological saline at 25 ° C, and the magnetic bar (diameter 8 mm, length 31.8 mm) was stirred at 600 rpm to measure the time until the vortex disappeared in seconds. It was calculated by measuring with .

(5) Permeability

Liquid permeability was measured by the following formula.

[Calculation 4]

Perm = [20 mL / T1 (seconds)] * 60 seconds

In Equation 4 above,

Perm is the liquid permeability of superabsorbent polymer,

In T1, 0.2 g of super absorbent polymer is placed in a cylinder, physiological saline (0.9% by weight of sodium chloride aqueous solution) is poured so that the super absorbent polymer is completely submerged, the super absorbent polymer is swollen for 30 minutes, and then 20 mL of water is poured under a pressure of 0.3 psi. It is the time (seconds) required for physiological saline to pass through the swollen superabsorbent polymer. Measurements were conducted at room temperature (23 °C to 25 °C).

Specifically, a cylinder and a piston were prepared. As the cylinder, one having an inner diameter of 20 mm and having a glass filter and a stopcock at the bottom was used. As the piston, a screen that can freely move the cylinder up and down with an outer diameter slightly smaller than 20 mm is disposed at the bottom, a weight is placed at the top, and a screen and a weight are connected by a rod. It became. A weight was installed on the piston to apply a pressure of 0.3 psi due to the addition of the piston.

While the stopcock of the cylinder was closed, 0.2 g of super absorbent polymer was put thereinto, and an excessive amount of physiological saline solution (0.9% by weight of sodium chloride aqueous solution) was poured so that the super absorbent polymer was completely submerged. Then, the superabsorbent polymer was swollen for 30 minutes. Then, a piston was added so that a load of 0.3 psi could be uniformly applied on the swollen super absorbent polymer.

Next, the stopcock of the cylinder was opened and the time required for 20 mL of physiological saline to pass through the swollen superabsorbent polymer was measured in seconds. At this time, if the meniscus is marked when the cylinder is filled with 40 mL of physiological saline, and the meniscus is marked when the cylinder is filled with 20 mL of physiological saline, the level corresponding to 40 mL is increased to 20 mL. T1 in Equation 4 can be measured by measuring the time taken to reach the corresponding level.

The results are shown in Table 1 and Table 2.

unit Comparative Example 1 Comparative Example 3 Comparative Example 4 Example 1 Example 2 surface cross-linking Water phr 5.0 5.0 5.0 5.0 5.0 MeOH 3.0 3.0 3.0 3.0 3.0 EJ1030s 0.06 0.06 0.06 0.06 0.06 PDADMAC - Polyethyleneimine
0.1 - 0.1 - PMETAMS - - - 0.1 afterword Aerosil200 0.1 0.1 Aerosil200 0.1 + PMETAMS 0.1 0.1 0.1 product properties CRC g/g 30.4 30.3 30.2 31.0 30.7 0.7 AUP g/g 19.7 20.0 20.2 20.7 21.6 EEFC g/g 25.0 25.1 25.2 25.9 26.2 Vortex sec 24 24 24 21 20 Perm. sec 24 19 15 10 7

^* PDADMAC: poly(diallyldimethylammonium chloride) (manufacturer: SINOFLOC, Mw: 150,000 g/mol) ^* PMETAMS: poly(2-(methacryloyloxy)ethyltrimethylammonium methyl sulfate (manufacturer: Senka, Mw: 400,000 g/mol)

unit Comparative Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 surface cross-linking Water Phr 7 MeOH 3 EJ1030s 0.025 0.035 PMETAMS - 0.05 0.1 0.2 0.2 0.3 afterword Aerosil200 0.1 product properties CRC g/g 30.9 31.2 31.1 31 30.1 30.6 0.7 AUP g/g 12.5 13.1 14.8 16.0 20.2 20.2 EEFC g/g 21.7 22.2 23.0 23.5 25.2 25.4 Vortex sec 24 23 24 24 24 24 Perm. sec 20 17 16 14 11 11

As shown in Table 1, the superabsorbent polymers of Examples prepared according to the present invention further included a cationic polymer as a composition of the surface crosslinking liquid during surface crosslinking, so it was confirmed that the water absorption properties were superior to those of Comparative Examples.

In addition, as shown in Table 2, even when the superabsorbent polymer was prepared with a composition in which the crosslinking density was lowered by reducing the content of the surface crosslinking agent, the superabsorbent polymer of Examples prepared according to the present invention had the same physical properties as those of Comparative Examples. It was confirmed that the high pressure absorption capacity and liquid permeability were excellent while maintaining the level.

Claims (17)

cross-linking polymerization of a water-soluble ethylenically unsaturated monomer having an acidic group at least partially neutralized in the presence of a polymerization initiator and an internal cross-linking agent to form a hydrogel polymer;
forming a base resin powder by drying, pulverizing, and classifying the hydrogel polymer; and
a surface crosslinking step of forming a surface crosslinking layer by crosslinking the surface of the base resin powder in the presence of a surface crosslinking agent and a cationic polymer;
The cationic polymer contains a quaternary ammonium ion in the repeating unit,
A method for producing a superabsorbent polymer.
According to claim 1,
The cationic polymer includes a repeating unit derived from an ethylenically unsaturated monomer to which ammonium ions are linked.
A method for producing a superabsorbent polymer.
According to claim 1,
The cationic polymer contains a cyclic ammonium ion in the repeating unit,
A method for producing a superabsorbent polymer.
According to claim 1,
The cationic polymer is poly(diallyldimethylammonium chloride), poly(2-(methacryloyloxy)ethyltrimethylammonium methyl sulfate), poly(2-dimethylamino)ethyl methacrylate methyl chloride quaternary salt), And poly (acrylamide-dimethylaminoethyl acrylate quaternary salt) containing any one or more selected from the group consisting of,
A method for producing a superabsorbent polymer.
According to claim 1,
The cationic polymer has a weight average molecular weight of 50,000 g / mol to 700,000 g / mol,
A method for producing a superabsorbent polymer.
According to claim 1,
The cationic polymer is included in 0.01 parts by weight to 0.9 parts by weight based on 100 parts by weight of the base resin.
A method for producing a superabsorbent polymer.
According to claim 1,
The surface crosslinking agent includes a polyhydric alcohol-based compound, a polyhydric epoxy-based compound, a haloepoxy compound, or an alkylene carbonate-based compound,
A method for producing a superabsorbent polymer.
According to claim 1,
The surface crosslinking agent is used in an amount of 0.001 to 5 parts by weight based on 100 parts by weight of the base resin.
A method for producing a superabsorbent polymer.
a base resin powder comprising a cross-linked polymer of a water-soluble ethylenically unsaturated monomer having an acidic group at least partially neutralized; and
A surface crosslinking layer formed on the base resin powder by further crosslinking the crosslinked polymer with a surface crosslinking agent,
The surface crosslinking layer comprises a cationic polymer containing quaternary ammonium ions in repeating units,
super absorbent polymer.
According to claim 9,
The cationic polymer includes a repeating unit derived from an ethylenically unsaturated monomer to which ammonium ions are linked.
super absorbent polymer.
According to claim 9,
The cationic polymer contains a cyclic ammonium ion in the repeating unit,
super absorbent polymer.
According to claim 9,
The cationic polymer is poly(diallyldimethylammonium chloride), poly(2-(methacryloyloxy)ethyltrimethylammonium methyl sulfate), poly(2-dimethylamino)ethyl methacrylate methyl chloride quaternary salt), And poly (acrylamide-dimethylaminoethyl acrylate quaternary salt) containing any one or more selected from the group consisting of,
super absorbent polymer.
According to claim 9,
The surface crosslinking agent includes a polyhydric alcohol-based compound, a polyhydric epoxy-based compound, a haloepoxy compound, or an alkylene carbonate-based compound,
super absorbent polymer.
According to claim 9,
The liquid permeability of the superabsorbent polymer is 18 seconds or less,
super absorbent polymer.
According to claim 9,
The centrifugal retention capacity (CRC) of the superabsorbent polymer measured according to the EDANA method WSP 241.3 is 25 g / g to 40 g / g,
super absorbent polymer.
According to claim 9,
The absorbent capacity under load (AUP) of 0.7 psi measured according to the EDANA method WSP 242.3 of the superabsorbent polymer is 10 g/g to 30 g/g,
super absorbent polymer.
According to claim 9,
Vortex of the superabsorbent polymer is 40 seconds or less,
super absorbent polymer.