KR20210038228A - Preparation method for super absorbent polymer - Google Patents

Abstract

The present invention provides a method for preparing a super absorbent polymer having a high initial absorption rate and excellent repeated absorption performance.

Description

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

The present invention relates to a method for producing a super absorbent polymer having a fast initial absorption rate and excellent repeated absorption performance.

Super Absorbent Polymer (SAP) is a synthetic polymer material that has a function of absorbing moisture of 500 to 1,000 times its own weight.In addition to hygiene products such as baby diapers, adult diapers, and sanitary products, soil repair materials It is widely used as a material such as water-stop material, food freshness retention material, etc.

In most cases, such super absorbent polymers are widely used in the field of sanitary materials such as diapers and sanitary napkins, and for this purpose, it is necessary to exhibit high absorption of moisture, etc., and moisture absorbed by external pressure must not escape. In addition, it is necessary not only to quickly absorb water, but also to maintain a fast absorption rate even under repeated use conditions.

In addition, after the super absorbent polymer applied to hygiene materials such as diapers and sanitary napkins absorbs liquid, the surface may become moist and give an unpleasant feeling of use. To prevent this, the super absorbent polymer is required to exhibit a fast initial absorption rate. The faster the initial absorption rate, the more comfortable the state of use can be maintained because the dry surface is maintained even after swelling by the liquid.

In general, this absorption rate can be improved by increasing the surface area of the super absorbent polymer. For example, a method of increasing the roughness of the particle surface is used by forming a porous structure on the surface of the particles of a super absorbent polymer by using a foaming agent, or by passing through a hole of a narrow size in the gel subdividing process of the polymer. The method of using the blowing agent has a point in that it is difficult to obtain uniformly porous particles, and accordingly, it is difficult to implement a sufficiently fast absorption rate. In addition, when a large amount of the foaming agent is used in order to speed up the absorption rate, the strength of the particles is weakened after drying, so that an excessive amount of fine particles is formed in the pulverizing process.

On the one hand, it is possible to increase the absorption rate by increasing the surface area by making a sufficiently small primary particle through reverse phase suspension polymerization and assembling it to make secondary particles, but using a large amount of organic solvent and a complex solvent recovery process There is a disadvantage that the organic solvent remains in the super absorbent polymer particles.

Accordingly, there is a need for continuous research on a method of manufacturing a super absorbent polymer capable of realizing a sufficient initial absorption rate while not using a foaming agent or minimizing the amount of use.

An object of the present invention is to provide a method for producing a super absorbent polymer having a fast initial absorption rate and excellent repetitive absorption performance.

The present invention provides a step of performing a neutralization reaction by adding a basic substance to a monomer composition comprising a water-soluble ethylenically unsaturated monomer having an acidic group, an internal crosslinking agent, and a bubble stabilizer;

Lowering the temperature of the monomer composition to 30 ^o C to 50 ^o C after the neutralization reaction, and crosslinking the water-soluble ethylenically unsaturated monomer having an acidic group in the presence of a polymerization initiator to form a hydrogel polymer;

Drying the hydrogel polymer;

Pulverizing the dried polymer; And

Including; mixing the pulverized polymer and a surface crosslinking agent to perform a surface crosslinking reaction

The bubble stabilizer comprises at least one selected from the group consisting of sucrose ester and sulfuric ester salt,

It provides a method for producing a super absorbent polymer.

In addition, the present invention provides a super absorbent polymer prepared by the above-described method.

Specifically, the superabsorbent polymer neutralizes a water-soluble ethylenically unsaturated monomer having an acidic group in the presence of at least one bubble stabilizer selected from the group consisting of sucrose ester and sulfuric acid ester salt, and then crosslinking polymerization with an internal crosslinking agent. A base resin containing the resulting crosslinked polymer; And a surface cross-linking layer formed on the surface of the base resin, the water holding capacity (CRC) measured according to the EDANA method WSP 241.3 is 25 g/g or more, and the absorption rate (vortex time) is 40 or less.

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

The terms used in the present 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 indicates otherwise.

In the present specification, terms such as "comprise", "include" or "have" are used to describe implemented features, numbers, steps, components, or combinations thereof, and one or more other features, numbers, and steps , Components, combinations thereof, or the possibility of addition are not excluded.

In addition, in the present specification, when each layer or element is referred to as being formed “on” or “on” each layer or element, it means that each layer or element is formed directly on each layer or element, or other It means that a layer or element may be additionally formed between each layer, on the object, or on the substrate.

The present invention will be described in detail below and exemplify specific embodiments, as various modifications can be made and various forms can be obtained. However, this does not limit the present invention to a specific form of disclosure, and it should be understood that all changes, equivalents, and substitutes included in the spirit and scope of the present invention are included.

Hereinafter, the present invention will be described in detail.

According to an aspect of the present invention, a step of performing a neutralization reaction by adding a basic substance to a monomer composition comprising a water-soluble ethylenically unsaturated monomer having an acidic group, an internal crosslinking agent, and a bubble stabilizer; Lowering the temperature of the monomer composition to 30 ^o C to 50 ^o C after the neutralization reaction, and crosslinking the water-soluble ethylenically unsaturated monomer having an acidic group in the presence of a polymerization initiator to form a hydrogel polymer; Drying the hydrogel polymer; Pulverizing the dried polymer; And performing a surface crosslinking reaction by mixing the pulverized polymer and a surface crosslinking agent, wherein the bubble stabilizer comprises at least one selected from the group consisting of sucrose ester and sulfuric ester salt. , A method for producing a super absorbent polymer is provided.

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

In addition, the "base resin" is made into a powder form by drying and pulverizing a polymer in which a water-soluble ethylenically unsaturated monomer is polymerized, and crosslinked polymer particles in which the water-soluble ethylenically unsaturated monomer is polymerized and crosslinked by an internal crosslinking agent. It means a collection of ). That is, the base resin refers to a powder form composed of crosslinked polymer particles without performing a surface modification or surface crosslinking step described later. Accordingly, "crosslinking the surface of the base resin" means crosslinking the surface of each of the crosslinked polymer particles constituting the base resin.

In addition, "super absorbent polymer" means the polymer or the base resin itself, depending on the context, or an additional process such as surface crosslinking, fine powder reassembly, drying, grinding, classification, etc. for the polymer or the base resin It is used to cover all items that have been in a state suitable for commercialization after passing through.

Recently, in a situation where hygiene materials, especially diapers, are used, the surface may become moist after absorbing liquid by the super absorbent polymer, which may give an unpleasant feeling of use.In order to prevent this, whether the super absorbent polymer exhibits a fast initial absorption rate, Whether or not the excellent absorption rate is maintained even during repeated injections is an important measure of diaper characteristics. Accordingly, in addition to improving the water-holding capacity and absorption capacity under pressure, which are basic physical properties of the super absorbent polymer, the rapid initial absorption rate and improvement of the repeated absorption performance have become important issues.

In a situation where the initial absorption rate and repeated absorption capacity of such super absorbent polymers are evaluated as important physical properties, conventionally, for this purpose, a large number of pores are formed on the surface of the super absorbent polymer to increase the contact area with water or the particle size of the super absorbent polymer. It is known how to make it smaller. However, there is a limitation in reducing the particle size of the super absorbent polymer, and when pores are formed unevenly on the surface, there is a disadvantage in that a large number of fine particles are formed in the pulverizing process, resulting in poor processability.

In particular, if a large amount of bubble stabilizer is used with a foaming agent after neutralization in the conventional method, the surface tension of the superabsorbent polymer decreases, and the diaper applied with this decreases the liquid diffusion rate due to the weakening of the capillary force and increases the wetness of the surface. There are drawbacks. Therefore, it is very important to minimize and use the bubble stabilizer while at the same time realizing a fast absorption rate.

Accordingly, the present inventor neutralizes the acidic group contained in the water-soluble ethylenically unsaturated monomer in the presence of a specific bubble stabilizer such as sucrose ester and sulfuric acid ester when preparing the base resin, and then adjusts the temperature raised by the heat of neutralization to the optimum range. In the case of performing crosslinking polymerization by lowering to, it was found that the absorption rate and repeated absorption performance were remarkably improved even without using an additional blowing agent. In addition, even with the same foam stabilizer, it was confirmed that a significant difference appears in the effect depending on the time point of application, thereby completing the present invention.

Specifically, the bubble stabilizer may include one or more selected from the group consisting of sucrose ester and sulfuric ester salt. , For example, the sucrose ester may be sucrose stearate, sucrose palmitate, or sucrose laurate. In addition, the sulfate ester salt may be sodium dodecyl sulfate, ammonium lauryl sulfate, or sodium lauryl ether sulfate (SLES).

By neutralizing the acidic groups contained in the water-soluble ethylenically unsaturated monomer in the presence of bubble stabilizers such as sucrose ester and sulfuric ester salt, microbubbles generated by the heat of neutralization during the neutralization reaction are trapped and stabilized. You can get reinforced particles.

And, after neutralizing the acidic group contained in the water-soluble ethylenically unsaturated monomer in the presence of the specific bubble stabilizer as described above, the temperature of the monomer composition is about 30 ^o C to about 50 ^o C, or about 32 ^o C to about It may ^{be lowered to 48 o} C, or about 35 ^o C to about 45 ^o C, and cross-linked polymerization of the water-soluble ethylenically unsaturated monomer having an acidic group in the presence of a polymerization initiator to form a hydrogel polymer. By optimizing the polymerization temperature as described above, microbubbles generated by performing a neutralization process in the presence of a bubble stabilizer are collected and stabilized to effectively control the size and distribution of pores, and finely porous particles can be obtained.

Accordingly, before neutralizing the acidic group contained in the water-soluble ethylenically unsaturated monomer, a specific bubble stabilizer such as sucrose ester and sulfuric acid ester salt was added and then a neutralization reaction was performed. When crosslinking polymerization is performed by lowering the temperature to the optimum range, microbubbles generated by the neutralization heat during the neutralization reaction can be maximized, stabilized effectively, and finely porous particles can be obtained. A base resin having a vortex time can be prepared, and a super absorbent polymer having a more improved absorption capacity and an absorption rate can be obtained.

Hereinafter, a method of manufacturing a super absorbent polymer according to an embodiment will be described in more detail for each step.

In the method for producing a super absorbent polymer according to an embodiment, first, a neutralization reaction step is performed by adding a basic substance to a monomer composition including a water-soluble ethylenically unsaturated monomer having an acidic group, an internal crosslinking agent, and a bubble stabilizer.

The water-soluble ethylenically unsaturated monomer may be any monomer commonly used in the preparation of a super absorbent polymer. As a non-limiting example, the water-soluble ethylenically unsaturated monomer may be a compound represented by the following Formula 1:

[Formula 1]

R ₁ -COOM ¹

In 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 (meth)acrylic acid, and monovalent (alkali) metal salts, divalent metal salts, ammonium salts, and organic amine salts of these acids.

As described above, when (meth)acrylic acid and/or a salt thereof are used as a water-soluble ethylenically unsaturated monomer, it is advantageous to obtain a super absorbent polymer having improved water absorption. In addition, the monomers include maleic anhydride, fumaric acid, crotonic acid, itaconic acid, 2-acryloylethane sulfonic acid, 2-methacryloylethanesulfonic acid, 2-(meth)acryloylpropanesulfonic acid or 2-(meth) )Acrylamide-2-methyl propane sulfonic acid, (meth)acrylamide, N-substituted (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, methoxypolyethylene Glycol (meth)acrylate, polyethylene glycol (meth)acrylate, (N,N)-dimethylaminoethyl (meth)acrylate, (N,N)-dimethylaminopropyl (meth)acrylamide, and the like may be used.

Here, the water-soluble ethylenically unsaturated monomer may have an acidic group, and the acidic group may be a non-neutralized non-neutralized form or at least some of the acidic groups may be neutralized. However, in the aspect of obtaining finely porous particles by sufficiently collecting microbubbles generated by the heat of neutralization in the neutralization reaction with a basic substance, the water-soluble ethylenically unsaturated monomer prior to the neutralization reaction is preferably unneutralized and not neutralized. Do.

In particular, after mixing the water-soluble ethylenically unsaturated monomer having an acidic group with an internal crosslinking agent and a bubble stabilizer, a basic substance is added to perform a neutralization reaction, thereby collecting and stabilizing microbubbles generated by the heat of neutralization during the neutralization reaction. Porous particles can be obtained.

Specifically, the bubble stabilizer includes at least one selected from the group consisting of sucrose ester and sulfuric ester salt. As an example, the sucrose ester may be one or more selected from the group consisting of sucrose stearate, sucrose palmitate, and sucrose laurate. , Preferably it may be sucrose stearate. In addition, the sulfate ester salt is one selected from the group consisting of sodium dodecyl sulfate, ammonium lauryl sulfate, and sodium lauryl ether sulfate (SLES). It may be more than one, preferably sodium dodecyl sulfate (sodium dodecyl sulfate).

In addition, based on 100 parts by weight of the water-soluble ethylenically unsaturated monomer having an acidic group, the bubble stabilizer is from about 0.001 parts by weight to about 0.1 parts by weight, or about 0.005 parts by weight to about 0.05 parts by weight, or about 0.01 parts by weight to about 0.02. It may include parts by weight. The bubble stabilizer may be included in an amount of about 0.001 parts by weight or more in terms of improving the absorption rate. In addition, when a large amount of the foam stabilizer is used in excess of about 0.1 parts by weight, the surface tension of the superabsorbent resin decreases, resulting in a decrease in the surface tension of the diaper. have.

On the other hand, a monomer composition comprising a water-soluble ethylenically unsaturated monomer having an acidic group, an internal crosslinking agent, and a bubble stabilizer is prepared from about 3 minutes to about 60 minutes, or from about 5 minutes to about 55 minutes, or from about 10 minutes to about 50 minutes, or After stirring for about 15 minutes to about 45 minutes, a basic substance may be added to perform a neutralization reaction. At this time, it is preferable to stir for about 3 minutes or more in terms of uniform dispersion of the monomer composition, and it is preferable to stir for about 60 minutes or less in terms of total working time.

In this case, as a neutralizing agent for performing a neutralization reaction with the water-soluble ethylenically unsaturated monomer, a basic substance capable of neutralizing an acidic group may be mentioned. An alkali metal salt may be used as the basic material, and specifically, at least one of lithium hydroxide, sodium hydroxide, potassium hydroxide, ammonium carbonate, sodium carbonate, potassium carbonate, ammonium phosphate, and sodium phosphate may be used. However, in consideration of performance and manufacturing cost, sodium hydroxide or sodium carbonate may be used.

The use ratio of the basic substance is about 50 mol% to about 90 mol%, or about 55 mol% to about 88 mol%, or about 58 mol% to about 85 mol% of the acidic group contained in the water-soluble ethylenically unsaturated monomer. Can be %. The basic material may be used in an amount of 50 mol% or more in terms of water holding capacity, and 90 mol% or less in terms of efficiency of polymerization reaction time.

In addition, as described above, the water-soluble ethylenically unsaturated monomer having an acidic group is neutralized with a basic substance in the presence of at least one bubble stabilizer selected from the group consisting of sucrose ester and sulfuric acid ester salt. At least some of the acidic groups contained in the ethylenically unsaturated monomer may be neutralized or may be in the form of a completely neutralized salt. At this time, the degree of neutralization of the water-soluble ethylenically unsaturated monomer, which refers to the degree of neutralization by the basic substance among the acidic groups contained in the water-soluble ethylenically unsaturated monomer, is about 50 mol% to about 90 mol%, or about 60 mol% To about 85 mole percent, or about 65 mole percent to about 85 mole percent, or about 70 mole percent to about 80 mole percent. 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 the polymerization may be difficult to proceed smoothly. On the contrary, if the degree of neutralization is too low, the absorption power of the polymer is greatly reduced. It may exhibit properties such as elastic rubber that are difficult to handle.

In addition, the term'internal crosslinking agent' used in the present specification is a term used to distinguish it from the surface crosslinking agent for crosslinking the surface of the base resin to be described later, and serves to crosslink and polymerize the unsaturated bonds of the water-soluble ethylenically unsaturated monomers described above. Do it. The crosslinking in the above step proceeds without distinction between the surface or the interior, but by the surface crosslinking process of the base resin to be described later, the surface of the particles of the finally prepared super absorbent polymer has a structure crosslinked by a surface crosslinking agent, and the inside is the interior. It consists of a crosslinked structure by a crosslinking agent.

As the internal crosslinking agent, any compound may be used as long as it allows the introduction of a crosslinking bond 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, butanedioldi(meth)acrylate, butylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, hexanedioldi(meth)acrylate )Acrylate, triethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, dipentaerythritol pentaacrylate, glycerin tri(meth)acrylate, penta A polyfunctional crosslinking agent 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 is not limited thereto. Preferably, ethylene glycol diglycidyl ether may be used among them.

This internal crosslinking agent may be used in an amount of about 0.01 parts by weight to about 5 parts by weight based on 100 parts by weight of the water-soluble ethylenically unsaturated monomer. For example, the internal crosslinking agent is about 0.01 parts by weight or more, about 0.05 parts by weight or more, about 0.1 parts by weight or more, or about 0.45 parts by weight or more, and about 5 parts by weight or less, based on 100 parts by weight of the water-soluble ethylenically unsaturated monomer. 3 parts by weight or less, about 2 parts by weight or less, about 1 part by weight or less, or about 0.7 parts by weight or less may be used. If the content of the upper internal crosslinking agent is too low, crosslinking does not occur sufficiently, and thus it may be difficult to implement the strength above an appropriate level, and if the content of the upper internal crosslinking agent is too high, the internal crosslinking density increases, and thus it may be difficult to implement the desired water holding capacity.

On the other hand, in the method for producing a super absorbent polymer according to an embodiment, after performing the above-described neutralization reaction, about 30 ^o C to about 50 ^o C, or about 32 ^o C to about 48 ^o C, or It is lowered to about 35 ^° C. to about 45 ^° C., and crosslinking polymerization of the water-soluble ethylenically unsaturated monomer having an acidic group in the presence of a polymerization initiator to form a hydrogel polymer. If the cooling step is not performed after the neutralization reaction, the temperature of the neutralization solution ^{is generally 80 o} C or higher, and the reaction occurs with only a small amount of polymerization initiator, making it difficult to control the reaction rate. There is a drawback that serial production is difficult.

Prior to such crosslinking polymerization, after neutralizing the acidic groups contained in the water-soluble ethylenically unsaturated monomer in the presence of a specific bubble stabilizer, crosslinking polymerization is performed by lowering the elevated temperature to the optimum range after the neutralization reaction. Finely porous particles can be obtained by collecting and stabilizing the generated microbubbles.

^{The crosslinking polymerization temperature should be 30 o} C or higher in terms of efficiency of the polymerization initiation time, ^{and 50 o} C is preferable in terms of improving the stability of the neutralization solution.

Meanwhile, the crosslinking polymerization is performed in the presence of a polymerization initiator, and the polymerization initiator may be appropriately selected according to a polymerization method. For example, as the polymerization initiator, a thermal polymerization initiator is used when a thermal polymerization method is used, a photo polymerization initiator is used when a photo polymerization method is used, and a hybrid polymerization method (a method using both heat and light) is used. Both a thermal polymerization initiator and a photopolymerization initiator can be used. However, even by the photopolymerization method, a certain amount of heat is generated by light irradiation such as ultraviolet irradiation, and a certain amount of heat is generated according to the progress of the polymerization reaction, which is an exothermic reaction, and thus a thermal polymerization initiator may be additionally used.

The photopolymerization initiator may be used without limitation of its configuration as long as it is a compound capable of forming radicals by light such as ultraviolet rays.

Examples of the photopolymerization initiator include benzoin ether, dialkyl acetophenone, hydroxyl alkylketone, phenyl glyoxylate, and benzyl dimethyl ketone. Ketal), acyl phosphine, and alpha-aminoketone (α-aminoketone) may be used at least one selected from the group. On the other hand, specific examples of acylphosphine include diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide, phenylbis (2,4,6-trimethylbenzoyl) phosphine oxide, ethyl (2,4,6- Trimethylbenzoyl)phenylphosphineate and the like. More various photoinitiators are well specified in Reinhold Schwalm's book "UV Coatings: Basics, Recent Developments and New Application (Elsevier 2007)" p115, and are not limited to the above examples.

In addition, as the thermal polymerization initiator, at least one selected from the group of initiators consisting of persulfate-based initiators, azo-based initiators, hydrogen peroxide and ascorbic acid may be used. Specifically, examples of the persulfate-based initiator include sodium persulfate (Na ₂ S ₂ O ₈ ), potassium persulfate (K ₂ S ₂ O ₈ ), ammonium persulfate (Ammonium persulfate; (NH ₄ )) ₂ S ₂ O ₈ ), etc., and examples of azo-based initiators include 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), 4,4-azobis-(4-cyanovaleric acid) (4,4-azobis-(4-cyanovaleric acid)) and the like. More various thermal polymerization initiators are well specified in Odian's'Principle of Polymerization (Wiley, 1981)', p203, and are not limited to the above-described examples.

This polymerization initiator may be used in an amount of 2 parts by weight or less based on 100 parts by weight of the water-soluble ethylenically unsaturated monomer. That is, 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 in the final product, which is not preferable. On the contrary, when the concentration of the polymerization initiator is higher than the above range, the polymer chain forming the network is shortened, so that the content of the water-soluble component increases and the absorption capacity under pressure may decrease, and thus the physical properties of the resin may be lowered, which is not preferable.

According to an embodiment of the present invention, the crosslinking polymerization is performed in a monomer composition with sodium bicarbonate, sodium carbonate, potassium bicarbonate, potassium carbonate, and calcium bicarbonate. bicarbonate), calcium carbonate, magnesium bicarbonate, and magnesium carbonate.

In addition, the crosslinking polymerization may be performed by further adding at least one bubble stabilizer selected from the group consisting of sucrose ester and sulfuric acid ester salt to the monomer composition, and the type and content range of the bubble stabilizer Is as described above.

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

And, the monomer composition containing the monomer may be, for example, in a solution state dissolved in a solvent such as water, and the solid content in the monomer composition in such a solution state, that is, the concentration of the monomer, the internal crosslinking agent, and the polymerization initiator It may be appropriately adjusted in consideration of time and reaction conditions. For example, the solid content in the monomer composition may be 10% to 80% by weight, or 15% to 60% by weight, or 20% to 40% by weight.

When the monomer composition has a solid content in the above range, the gel effect phenomenon occurring in the polymerization reaction of a high concentration aqueous solution is used to prevent the need to remove the unreacted monomer after polymerization, while improving the pulverization efficiency during pulverization of the polymer to be described later. It can be advantageous to control.

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

On the other hand, after neutralizing a water-soluble ethylenically unsaturated monomer having an acidic group in the presence of at least one bubble stabilizer selected from the group consisting of sucrose esters and sulfuric acid ester salts, water-soluble ethylenically unsaturated having an acidic group at least partially neutralized. The crosslinking polymerization of the monomers may proceed without any particular limitation on the configuration as long as the hydrogel polymer can be formed by thermal polymerization, photopolymerization, or hybrid polymerization.

Specifically, the polymerization method is largely divided into thermal polymerization and photopolymerization depending on the polymerization energy source, and when performing thermal polymerization, it can be performed in a reactor having a stirring axis such as a kneader, and when performing photopolymerization, it is possible to move. It may be carried out in a reactor equipped with a conveyor belt or in a container having a flat bottom, but the above-described polymerization method is an example, and the present invention is not limited to the above-described polymerization method.

For example, as described above, the hydrogel polymer obtained by thermal polymerization by supplying hot air or heating the reactor to a reactor such as a kneader equipped with a stirring shaft may be transferred to the reactor outlet according to the shape of the stirring shaft provided in the reactor. The discharged hydrogel polymer may be in the form of several centimeters to several millimeters. Specifically, the size of the resulting hydrogel polymer may vary depending on the concentration and injection speed of the monomer composition to be injected, and a hydrogel polymer having a weight average particle diameter of 2 mm to 50 mm can be obtained.

In addition, as described above, when photopolymerization is carried out in a reactor equipped with a movable conveyor belt or a container having a flat bottom, the form of the hydrogel polymer usually obtained may be a hydrogel polymer in a sheet form having the width of the belt. At this time, the thickness of the polymer sheet varies depending on the concentration of the monomer composition to be injected and the injection speed or the injection amount, but it is generally recommended to supply the monomer composition so that a sheet-like polymer having a thickness of about 0.5 cm to about 5 cm can be obtained. desirable. In the case of supplying the monomer composition to the extent that the thickness of the polymer on the sheet is too thin, the production efficiency is not preferable, and when the thickness of the polymer on the sheet exceeds 5 cm, due to the excessively thick thickness, the polymerization reaction is evenly performed over the entire thickness. It may not happen.

At this time, the water content of the hydrogel polymer obtained by the above method may have a water content of about 40% by weight to about 80% by weight. Meanwhile, in the entire specification, the "water content" refers to a value obtained by subtracting the weight of the dried polymer from the weight of the hydrogel polymer as the content of moisture occupied by the total weight of the hydrogel polymer. Specifically, it is defined as a value calculated by measuring the weight loss due to evaporation of moisture in the polymer during drying by raising the temperature of the polymer in a coarsely pulverized state through infrared heating. At this time, the drying condition is ^{a method of raising the temperature from room temperature to about 180 o} C and then ^{maintaining it at 180 o} C. The total drying time is set to 40 minutes including 5 minutes of the temperature rise step, and the moisture content is measured.

Next, a step of preparing a base resin including a crosslinked polymer obtained by drying and pulverizing the hydrogel polymer is performed.

The crosslinked polymer in the above step has a particulate form by drying and pulverizing the hydrogel polymer, and thus, the prepared base resin is in the form of a powder consisting of crosslinked polymer particles. Specifically, the base resin may be a crosslinked polymer particle having a particle diameter of about 150 μm to about 850 μm in 90% by weight or more based on the total weight.

On the other hand, the step of preparing the base resin may include a process of coarsely pulverizing the hydrogel polymer before drying in order to increase drying efficiency.

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

Through this coarse pulverization process, the particle diameter of the hydrogel polymer may be adjusted to about 0.1 mm to about 10 mm. Grinding so that the particle diameter is less than 0.1 mm is not technically easy due to the high moisture content of the hydrogel polymer, and a phenomenon of agglomeration between the pulverized particles may occur. On the other hand, when pulverizing so that the particle diameter exceeds 10 mm, the effect of increasing the efficiency of the subsequent drying step may be insignificant.

Drying is performed on the hydrogel polymer immediately after polymerization that has undergone the coarse pulverization process as described above or has not been subjected to the coarse pulverization process. At this time, the drying temperature may be about 60 ^o C to about 250 ^o C. At this time, when the drying temperature is ^{less than about 70 o} C, the drying time may be too long, and when the drying temperature exceeds about 250 ^o C, only the polymer surface is excessively dried, and fine powder may be generated in a subsequent grinding process, There is a concern that the physical properties of the finally formed super absorbent polymer may be deteriorated. Therefore, preferably, the drying may be performed at a temperature ^{of about 100 o} C to about 240 ^{o C, more preferably about 110 o} C to about 220 ^o C.

In addition, in the case of the drying time, it may be performed for about 20 minutes to about 12 hours in consideration of process efficiency and the like. For example, it may be dried for about 10 minutes to about 100 minutes, or about 20 minutes to about 60 minutes.

As long as the drying method in the drying step is also commonly used as a drying process of the hydrous gel polymer, it 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 moisture content of the polymer after the drying step proceeds may be from about 0.1% to about 10% by weight.

Thereafter, the step of pulverizing the dried polymer obtained through the drying step may be performed. The pulverizing step is a step for optimizing the surface area of the dried polymer, and may be performed so that the pulverized crosslinked polymer has a particle diameter of about 150 µm to about 850 µm. Here, the particle size of the pulverized crosslinked polymer may be measured according to the European Disposables and Nonwovens Association (EDANA) standard EDANA WSP 220.3 method.

At this time, the pulverizer used for pulverization is specifically, a pin mill, a hammer mill, a screw mill, a roll mill, a disc mill, or a jog mill ( jog mill) or the like, but is not limited to the above-described example.

Thereafter, as a step of modifying the surface of the polymer pulverized through the above step, in the presence of a surface crosslinking liquid containing a surface crosslinking agent, the base resin powder is surface crosslinked through heat treatment to form super absorbent polymer particles. to be.

The surface modification is a step of forming a super absorbent polymer having improved physical properties by inducing a crosslinking reaction on the surface of the pulverized polymer in the presence of a surface crosslinking agent. Through such surface modification, a surface crosslinking layer is formed on the surface of the pulverized polymer particles.

The surface modification (surface crosslinking reaction) may be carried out by a conventional method of increasing the crosslinking density of the surface of the polymer particles, for example, a crosslinking reaction by mixing a solution containing a surface crosslinking agent and the pulverized polymer Can be done with

Here, the surface crosslinking agent is a compound capable of reacting with a functional group of the polymer, and its configuration is not particularly limited. However, as a non-limiting example, the surface crosslinking agent is ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerol polyglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether , Ethylene glycol, diethylene glycol, propylene glycol, triethylene glycol, tetraethylene glycol, propane diol, dipropylene glycol, polypropylene glycol, glycerin, polyglycerin, butanediol, heptanediol, hexanediol trimethylolpropane, pentaerythritol, It may be one or more compounds selected from the group consisting of sorbitol, calcium hydroxide, magnesium hydroxide, aluminum hydroxide, iron hydroxide, calcium chloride, magnesium chloride, aluminum chloride, and iron chloride.

At this time, the content of the surface crosslinking agent may be appropriately adjusted according to the type of the crosslinking agent or reaction conditions, and preferably, it may be adjusted to about 0.001 parts by weight to about 5 parts by weight based on 100 parts by weight of the pulverized polymer. If the content of the surface crosslinking agent is too low, surface modification may not be performed properly, and physical properties of the final resin may be deteriorated. Conversely, when an excessive amount of the surface crosslinking agent is used, the absorption power of the resin may be rather lowered due to excessive surface crosslinking reaction, which is not preferable.

Meanwhile, in the surface modification step, a method of mixing the surface crosslinking agent and the pulverized polymer into a reaction tank, a method of spraying a surface crosslinking agent onto the pulverized polymer, and continuously supplying the pulverized polymer and the surface crosslinking agent to a continuously operated mixer. It can be carried out by a conventional method such as a method of mixing.

In addition, water may be additionally added when adding the surface crosslinking agent. When the surface crosslinking agent and water are added together as described above, even dispersion of the surface crosslinking agent can be induced, agglomeration of the polymer particles is prevented, and the penetration depth of the surface crosslinking agent to the polymer particles can be more optimized. In consideration of these purposes and effects, the content of water added with the surface crosslinking agent may be adjusted to about 0.5 parts by weight to about 10 parts by weight based on 100 parts by weight of the pulverized polymer.

^{And, the surface crosslinking is about 100 o} C to about 200 ^o C, or about 110 ^o C to about 195 ^o C, or about 120 ^o C to about 190 ^o C, or about 135 ^o C, depending on the type of crosslinking agent used. It may be carried out under a temperature of about 185 ^o C, and may be carried out continuously after the drying and pulverizing step performed at a relatively high temperature. More preferably, it may be carried out under a temperature of ^{about 110 o} C to about 195 ^o C, or about 120 ^o C to about 190 ^o C, or about 135 ^o C to about 185 ^{o C.}

At this time. The surface crosslinking reaction may proceed for about 1 minute to about 120 minutes, or about 1 minute to about 100 minutes, or about 10 minutes to about 60 minutes. That is, in order to induce a surface crosslinking reaction of a minimum limit and to prevent physical properties from deteriorating due to damage to the polymer particles during excessive reaction, the surface crosslinking reaction may be performed under the conditions of the surface crosslinking reaction described above.

Meanwhile, according to another embodiment of the present invention, a super absorbent polymer prepared according to the above-described manufacturing method is provided.

The super absorbent polymer is a crosslinked polymer obtained by neutralizing a water-soluble ethylenically unsaturated monomer having an acidic group in the presence of at least one bubble stabilizer selected from the group consisting of sucrose ester and sulfuric acid ester salt, and crosslinking polymerization with an internal crosslinking agent. Base resin comprising a; And a surface crosslinking layer formed on the surface of the base resin, and the water holding capacity (CRC) measured according to the EDANA method WSP 241.3 may be about 25 g/g or more or about 25 g/g to about 50 g/g, and , The vortex time may be about 40 seconds or less, or about 10 seconds to about 40 seconds.

Therefore, in the present invention, after neutralizing the acidic groups contained in the water-soluble ethylenically unsaturated monomer in the presence of a specific bubble stabilizer in the manufacture of the base resin, crosslinking polymerization is performed by lowering the temperature raised by the neutralization heat to the optimum range, resulting in the production of the super absorbent polymer. By trapping and stabilizing microbubbles, high water holding capacity and absorption rate can be exhibited.

For descriptions of the water-soluble ethylenically unsaturated monomer, the internal crosslinking agent, and the bubble stabilizer used in the super absorbent polymer, refer to the foregoing.

Specifically, the super absorbent polymer has a water holding capacity (CRC) of about 25 g/g or more, or about 35 g/g or more, or about 40 g/g or more, as measured according to the EDANA method WSP 241.3, and about 50 g /g or less, or about 48 g/g or less, or about 45 g/g or less.

In addition, the super absorbent polymer may have a vortex time of about 40 seconds or less, or about 35 seconds or less, or about 30 seconds or less. The lower the value of the absorption rate, the better, and the lower limit of the absorption rate may theoretically be about 1 second, but may be, for example, about 10 seconds or more, or about 15 seconds or more, or about 20 seconds or more.

The absorption rate refers to the time (time, unit: second) at which the vortex of the liquid disappears due to rapid absorption when a superabsorbent resin is added to physiological saline and stirred, and the shorter the time, the superabsorbent resin Can be seen as having a fast initial absorption rate.

As an example, when the superabsorbent polymer contains 2 g of the superabsorbent polymer in a 100 mL container, and is ^{immersed by pouring 30 mL of 24 o} C brine (0.9wt% NaCl aqueous solution) at a time, until the water on the surface disappears The first absorption time defined as the time of may be about 35 seconds or less, or about 30 seconds or less, or about 28 seconds or less. Specifically, even when the beaker is tilted sideways by about 45 degrees, it is determined that there is no moving water, and the time required from the time when the brine is added to this time can be measured as the first absorption time in seconds. The lower the value of the absorption time is, the better, and the lower limit of the first absorption time may theoretically be about 1 second, but may be, for example, about 10 seconds or more, or about 15 seconds or more, or about 20 seconds or more.

In addition, after 10 minutes elapsed from the measurement of the first absorption rate as described above, 30 mL of brine (0.9wt% NaCl aqueous solution) was poured again and immersed in 2, which is defined as the time until the water on the surface disappears. The difference absorption time may be about 45 seconds or less, or about 40 seconds or less, or about 35 seconds or less. The first and second absorption times are better as the value is smaller, so that the lower limit of the absorption time may theoretically be 1 second or less, but for example, it may be about 10 seconds or more, or about 15 seconds or more, or about 20 seconds or more. . Specifically, even if the beaker is tilted sideways by 45 degrees, it is determined that there is no moving water, and the time required from the point when the brine is re-injected to this point can be measured as the second absorption time in seconds. . The lower the value of the absorption time is, the better, and the lower limit of the second absorption time may theoretically be about 1 second, but may be, for example, about 15 seconds or more, or about 20 seconds or more, or about 25 seconds or more.

In addition, the super absorbent polymer is, when 1 g of the super absorbent polymer is put in a 250 mL beaker, immersed in 150 mL of brine for 10 minutes, and then poured all over a 100 mesh standard sieve having a diameter of 90 mm A 10-minute saline absorption capacity defined by weight of at least about 50 g, or at least about 53 g/g, or at least about 55 g/g, while at most about 73 g/g, or at most about 68 g/g, or about 65 g It can have a range of /g or less.

As described above, the superabsorbent polymer of the present invention has an excellent absorption ability, and in particular, it is possible to provide a high-quality sanitary material with a fast initial absorption rate and excellent repeated absorption performance.

According to the present invention, so that the surface of the superabsorbent polymer can be maintained in a dry state even after absorbing the liquid, the initial absorption rate absorbed in a short period of time after liquid injection is excellent, as well as excellent absorption rate during repeated injection. There is an excellent effect of manufacturing a super absorbent polymer that can be maintained.

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

[Example]

<Production of super absorbent polymer>

Example 1

In a 3L glass container equipped with a stirrer and thermometer, add 500 g of acrylic acid, 1.0 g of polyethylene glycol diacrylate (PEGDA 400, Mw = 400) as an internal crosslinking agent, and 0.05 g of sucrose stearate (S1670) as a bubble stabilizer at about 25 ^o C. And stirred for 30 minutes. Then, 800 g of an aqueous solution of sodium hydroxide having a concentration of 24% by weight was slowly added to the mixture, and a neutralization reaction was performed while stirring for 10 minutes, thereby preparing an aqueous water-soluble unsaturated monomer solution (neutralization degree: 70 mol%).

After the neutralization reaction was completed, the water-soluble unsaturated monomer aqueous solution temperature, which had increased due to the heat of neutralization, ^{was lowered to 40 o} C, and then diphenyl (2,4,6-trimethylbenzoyl)-phosphine oxide, a photoinitiator, was 0.05 g. Dissolve and add 30 g of water, and 1 g of sodium persulfate (SPS), a thermal polymerization initiator, is dissolved in 30 g of water and added, stirred for 30 seconds, and then 25 cm wide and 35 cm long, After being put in a container made of a silicone sheet having a height of 10 cm and a thickness of 0.5 cm, UV polymerization was performed ^{by irradiation with ultraviolet rays for 1 minute (irradiation amount: 10 mV/cm 2 ).} After performing the polymerization reaction in this way ^{, heat was applied in an oven at 80 o} C for 120 seconds to aging to obtain a hydrogel polymer sheet.

The obtained hydrogel polymer sheet was passed through a chopper having a hole size of 16 mm to prepare granular gel particles. The granular gel was dried in an oven capable of transferring air volume up and down. 185 ^o C hot air was uniformly dried by flowing from the bottom to the top for 15 minutes and from the top to the bottom for 15 minutes. After drying, the moisture content of the dried body was 2% or less. After pulverizing the dried resin with a food mixer, classify it with a standard mesh sieve of ASTM standard to make 150-300 µm particles 20% by weight, 300-600 µm particles 70% by weight, and 600-850 µm particles 10% by weight. The base resin to have was obtained.

A surface crosslinking solution containing 6 g of water, 6 g of methanol, 0.4 g of ethyleneglycol diglycidyl ether as a surface crosslinking agent, and 0.05 g of silica (Aerosil 200) was used in a high-speed mixer. After mixing, the mixture was put into a container consisting of a stirrer and a double jacket, and a surface crosslinking reaction was performed at ^{150 o C for 40 minutes.} After the surface crosslinking reaction was completed, the sample was cooled to room temperature, and classified into a standard mesh of ASTM standard to prepare a super absorbent polymer having a particle diameter of 150 µm to 850 µm.

Example 2

In Example 1, a superabsorbent polymer was prepared in the same manner as in Example 1, except that 0.1 g of sucrose stearate (S1670), which is a bubble stabilizer, was used.

Example 3

In Example 1, a super absorbent polymer was prepared in the same manner as in Example 1, except that 0.05 g of sodium dodecyl sulfate (SDS) was used instead of sucrose stearate (S1670) as a bubble stabilizer. I did.

Example 4

In Example 1, the same method as in Example 1, except for polymerization reaction by dissolving 1 g of sodium bicarbonate (sodium bicarbonate) in 30 g of water while adding a photoinitiator and a thermal initiator after the neutralization reaction was completed. To prepare a super absorbent polymer.

Comparative Example 1

In Example 1, after performing a neutralization reaction without adding a bubble stabilizer when preparing the aqueous unsaturated monomer solution, sucrose stearate (S1670), which is a bubble stabilizer together with a photoinitiator and a thermal initiator, in the monomer aqueous solution cooled to ^{40 o C.} A super absorbent polymer was prepared in the same manner as in Example 1, except that 0.05 g was added to perform polymerization reaction.

Comparative Example 2

A super absorbent polymer was prepared in the same manner as in Comparative Example 1, except that 0.05 g of sodium dodecyl sulfate] was used instead of sucrose stearate (S1670) as a bubble stabilizer.

Comparative Example 3

In Example 1, after the neutralization reaction was completed, the polymerization reaction was carried out by adding a photoinitiator and a thermal initiator at ^85° C without cooling ^{the temperature of the aqueous unsaturated monomer solution to 40°C.} As soon as the thermal initiator was added, the reaction proceeded and the polymerization was unstable, and as a result, unpolymerized material was generated in the polymerization sheet. A super absorbent polymer was prepared in the same manner as in Example 1 using a polymerization sheet excluding the unpolymerized material.

Comparative Example 4

A super absorbent polymer was prepared in the same manner as in Example 1, except that 0.05 g of sorbitan monosterate (Span 60) was used instead of sucrose stearate (S1670) as a bubble stabilizer.

Main process conditions for the Examples and Comparative Examples are as shown in Table 1 below.

Bubble stabilizer type Bubble stabilizer input amount
(Part by weight) Bubble stabilizer input
Point of view Add
Bubble stabilizer type Add
Bubble stabilizer input amount
(Part by weight) Add
Bubble stabilizer input
Point of view Type of blowing agent Foaming agent input amount
(Part by weight) Injection of blowing agent
Point of view Polymerization reaction temperature
( ^o C) Example 1 Sucrose stearate 0.01
(100ppm) Before neutralization none none none none none none 40 Example 2 Sucrose stearate 0.02
(200ppm) Before neutralization none none none none none none 40 Example 3 Sodium dodecyl sulfate 0.01
(100ppm) Before neutralization none none none none none none 40 Example 4 Sucrose stearate 0.01
(100ppm) Before neutralization none none none Sodium bicarbonate 0.2
(2000
ppm) After neutralization 40 Comparative Example 1 Sucrose stearate 0.01
(100ppm) After neutralization none none none none none none 40 Comparative Example 2 Sodium dodecyl sulfate 0.01
(100ppm) After neutralization none none none none none none 40 Comparative Example 3 Sucrose stearate 0.01
(100ppm) Before neutralization none none none none none none 85 Comparative Example 4 Sorbitan Mono Stearate 0.01
(100ppm) Before neutralization none none none none none none 40

In Table 1, the amount of the foam stabilizer, the additional foam stabilizer, and the foaming agent is a value by weight based on 100 parts by weight of acrylic acid.

<Experimental Example>

With respect to the superabsorbent polymer after surface crosslinking prepared in the Examples and Comparative Examples, physical properties were evaluated in the following manner.

Unless otherwise indicated, all the following physical property evaluations were performed at room temperature (about 23 to 25 ^o C), and physiological saline or saline means 0.9 wt% sodium chloride (NaCl) aqueous solution.

(1) Centrifuge Retention Capacity (CRC)

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

Specifically, super absorbent polymer W ₀ (g) (about 0.2 g) was uniformly placed in a nonwoven bag and sealed, and then immersed in physiological saline (0.9% by weight) at room temperature. After 30 minutes elapsed, water was removed 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. Moreover, after performing the same operation without using a resin, the mass W ₁ (g) at that time was measured. Using each obtained mass, CRC (g/g) was calculated according to the following equation.

[Equation 1]

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

(2) absorption rate (Vortex time)

The vortex time was measured in seconds according to the method described in International Patent Publication No. 1987-003208.

Specifically, put 50 mL of saline and a magnetic bar (diameter 8 mm, length 30 mm) in a 100 mL glass beaker, and set the temperature of the solution to 24 ^o C. After stirring at 600 rpm using a magnetic stirrer to create a vortex, add 2 g of super absorbent polymer at once, and measure the time until the vortex disappears in seconds. Was calculated.

(3) 1st and 2nd absorption time

Add 2 g of super absorbent polymer to a 100 mL glass beaker, add 30 mL of brine (temperature 24 ^o C) at a time, and measure the time until the fluid disappears completely from the surface in seconds, as the first absorption time. I did. Specifically, even when the beaker is tilted sideways by about 45 degrees, when there is no moving water, it is determined that it is completely absorbed, and the time required until this time is measured as the first absorption time in seconds.

After 10 minutes have elapsed after the completion of the first absorption test, 30 mL of brine (temperature 24 ^o C) is added at a time to perform the second absorption test, and the time until the fluid liquid completely disappears from the surface is counted in seconds. It measured in (sec) unit and it was set as the 1st absorption time. Even if the beaker was tilted sideways by 45 degrees, it was judged that there was no moving water, and the time required until this time was measured as the second absorption time in seconds.

(4) Ability to absorb salt water for 10 minutes

1 g of a super absorbent polymer was put in a 250 mL beaker and ^{immersed in 150 mL of 24 o} C brine for 10 minutes. A 100 mesh standard sieve having a diameter of 90 mm was placed on the top of another 250 mL beaker, and all of the immersed super absorbent polymer was poured onto the standard sieve, and then drained for 10 minutes. The mass of the gel remaining on the standard was measured, and the absorption capacity was determined for 10 minutes.

In the Examples and Comparative Examples, the conditions for adding the bubble stabilizer and the physical properties of the superabsorbent polymer after surface crosslinking are shown in Table 2 below.

CRC
(g/g) Vortex time
(sec) Primary
Absorption time
(sec) Secondary
Absorption time
(sec) 10 minutes
Salt absorption ability
(g) Example 1 42 30 28 34 57 Example 2 40 20 21 25 62 Example 3 41 31 29 35 56 Example 4 40 17 20 25 64 Comparative Example 1 42 53 50 70 47 Comparative Example 2 42 47 37 55 50 Comparative Example 3 47 65 60 85 47 Comparative Example 4 43 47 38 52 50

Referring to Table 2, it was confirmed that the examples of the present invention exhibited a fast absorption rate in both the measurement by the vortex method, the first and second absorption times, and the 10-minute saline absorption capacity. On the other hand, in Comparative Examples, both the initial absorption rate evaluated by the first absorption time and the absorption rate by the vortex method were not better than those of the Examples, and the absorption rate during repeated injection evaluated by the second absorption time and the absorption capacity of 10 minutes saline were evaluated It can be seen that the ability to absorb in a short period of time is also not good.

Claims (11)

Performing a neutralization reaction by adding a basic substance to a monomer composition comprising a water-soluble ethylenically unsaturated monomer having an acidic group, an internal crosslinking agent, and a bubble stabilizer;
Lowering the temperature of the monomer composition to 30 ^o C to 50 ^o C after the neutralization reaction, and crosslinking the water-soluble ethylenically unsaturated monomer having an acidic group in the presence of a polymerization initiator to form a hydrogel polymer;
Drying the hydrogel polymer;
Pulverizing the dried polymer; And
Including; mixing the pulverized polymer and a surface crosslinking agent to perform a surface crosslinking reaction
The bubble stabilizer comprises at least one selected from the group consisting of sucrose ester and sulfuric ester salt,
Method for producing a super absorbent polymer.
The method of claim 1,
The water-soluble ethylenically unsaturated monomer having an acidic group is unneutralized,
Method for producing a super absorbent polymer.
The method of claim 1,
The sucrose ester is sucrose stearate, sucrose palmitate, or sucrose laurate,
Method for producing a super absorbent polymer.
The method of claim 1,
The sulfate ester salt is sodium dodecyl sulfate, ammonium lauryl sulfate, or sodium lauryl ether sulfate (SLES),
Method for producing a super absorbent polymer.
The method of claim 1,
Comprising 0.001 parts by weight to 0.1 parts by weight of the bubble stabilizer based on 100 parts by weight of the water-soluble ethylenically unsaturated monomer having an acidic group,
Method for producing a super absorbent polymer.
The method of claim 1,
Adding a basic substance after stirring the monomer composition for 3 to 60 minutes,
Method for producing a super absorbent polymer.
The method of claim 1,
The basic material includes at least one selected from the group consisting of lithium hydroxide, sodium hydroxide, potassium hydroxide, ammonium carbonate, sodium carbonate, potassium carbonate, ammonium phosphate, and sodium phosphate,
Method for producing a super absorbent polymer.
The method of claim 1,
The basic substance is added in an amount of 30 mol% to 90 mol% of the acidic group contained in the water-soluble ethylenically unsaturated monomer.
Method for producing a super absorbent polymer.
A base resin comprising a crosslinked polymer obtained by neutralizing a water-soluble ethylenically unsaturated monomer having an acidic group in the presence of at least one bubble stabilizer selected from the group consisting of a sucrose ester and a sulfuric ester salt, followed by crosslinking polymerization with an internal crosslinking agent; And
Including a surface crosslinking layer formed on the surface of the base resin,
The water holding capacity (CRC) measured according to the EDANA method WSP 241.3 is 25 g/g or more,
Having a vortex time of 40 or less,
Super absorbent polymer.
The method of claim 9,
The super absorbent polymer has a first absorption time defined as the time until the flowing liquid disappears after containing 2 g of the super absorbent polymer in a 100 mL container and 30 mL of brine (0.9 wt% NaCl aqueous solution). Less than 35 seconds,
The second absorption time defined as the time until the flowing liquid disappears after adding 30 mL of brine (0.9 wt% NaCl aqueous solution) again 10 minutes after measuring the first absorption time is 45 seconds Below,
Super absorbent polymer.
The method of claim 9,
The super absorbent polymer is 10 minutes defined as the weight of the salt water absorbed by the super absorbent polymer for 10 minutes when 1 g of the super absorbent polymer is immersed in 150 mL of brine (0.9 wt% NaCl aqueous solution) and swelled for 10 minutes. Having a salt water absorption capacity of 53 g or more,
Super absorbent polymer.