KR20210078057A - Preparation method of super absorbent polymer - Google Patents

Abstract

The present invention relates to a method for manufacturing a super absorbent polymer. More specifically, the present invention relates to a method for manufacturing a super absorbent polymer capable of exhibiting a fast absorption rate by polymerizing a water-soluble ethylene-based unsaturated monomer having at least a partially neutralized acidic group in the presence of a xanthate.

Description

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

The present invention relates to a method for producing a super absorbent polymer. More specifically, it relates to a method for preparing a super absorbent polymer having a fast absorption rate.

Super Absorbent Polymer (SAP) is a synthetic polymer material that has the ability to absorb water 500 to 1,000 times its own weight, and each developer uses either SAM (Super Absorbency Material) or AGM (Absorbent Gel). Material), etc., are named differently. The superabsorbent polymer as described above began to be put to practical use as a sanitary tool, and is now widely used as a soil repair agent for horticulture, a water-retaining material for civil engineering and construction, a sheet for seedlings, a freshness maintenance agent in the food distribution field, and a poultice. .

Such superabsorbent polymers are mainly used in the field of hygiene materials such as diapers and sanitary napkins. In the sanitary material, the superabsorbent polymer is generally included in a state spread in the pulp. However, in recent years, efforts have been made to provide sanitary materials such as diapers with a thinner thickness, and as a part of that, the content of pulp is reduced, or moreover, so-called pulpless diapers such as diapers not used at all are used. Development is actively underway.

As such, in the case of a sanitary material in which the content of pulp is reduced or in which pulp is not used, the superabsorbent polymer is included in a relatively high ratio, so that the superabsorbent polymer particles are inevitably included in multiple layers in the sanitary material. In order for the entire superabsorbent polymer particles included in the multi-layered structure to more efficiently absorb liquids such as urine, the superabsorbent polymer needs to basically exhibit high absorption performance and absorption rate.

Accordingly, in recent years, attempts have been continuously made to manufacture and provide a superabsorbent polymer having an improved absorption rate.

The most common method for increasing the absorption rate is a method of increasing the surface area of the superabsorbent polymer by forming a porous structure inside the superabsorbent polymer.

As such, in order to increase the surface area of the superabsorbent polymer, conventionally, a porous structure is formed in the base resin powder by cross-linking polymerization using a carbonate-based foaming agent, or bubbles are formed in the monomer composition in the presence of a surfactant and/or a dispersant. After introducing the porous structure, cross-linking polymerization was performed to form the porous structure, and the like.

However, it is difficult to achieve an absorption rate above a certain level by any previously known method, so the development of a technology capable of further improving the absorption rate has been continuously requested.

Moreover, in order to obtain a superabsorbent polymer with a further improved absorption rate by the conventional method, it is inevitably accompanied by the use of an excessive amount of a foaming agent and/or surfactant, and as a result, various physical properties of the superabsorbent polymer, for example, Disadvantages such as surface tension, liquid permeability, or bulk density are lowered.

Accordingly, the development of a technology capable of further improving the absorption rate of the superabsorbent polymer without using a surfactant and/or a foaming agent has been continuously requested.

Accordingly, an object of the present invention is to provide a method for preparing a superabsorbent polymer capable of exhibiting a fast absorption rate by polymerizing a water-soluble ethylenically unsaturated monomer having at least partially neutralized acidic groups in the presence of xanthate.

In order to solve the above problems, the present invention provides a method for producing a super absorbent polymer comprising:

Preparing a monomer composition comprising a water-soluble ethylenically unsaturated monomer having at least a partially neutralized acidic group, an internal crosslinking agent, a polymerization initiator, and a xanthate represented by the following Chemical Formula 1;

polymerizing the monomer composition to form a hydrogel polymer;

drying and pulverizing the hydrogel polymer to prepare a powdery base resin; and

In the presence of a surface crosslinking agent, further crosslinking the surface of the base resin to form a surface crosslinking layer:

[Formula 1]

In Formula 1,

M is an alkali metal,

R is an alkyl group having 1 to 10 carbon atoms.

In the method for preparing the superabsorbent polymer according to the present invention, the absorption rate of the superabsorbent polymer can be improved by polymerizing a water-soluble ethylenically unsaturated monomer having at least partially neutralized acidic groups in the presence of xanthate.

The terminology used herein is used to describe exemplary embodiments only, and is not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly dictates otherwise. In this specification, terms such as "comprises", "comprises" or "have" are intended to designate the presence of an embodied feature, step, element, or a combination thereof, but one or more other features or steps; It should be understood that the possibility of the presence or addition of components, or combinations thereof, is not precluded in advance.

Since the present invention may have various changes and may have various forms, specific embodiments will be illustrated and described in detail below. However, this is not intended to limit the present invention to the specific disclosed form, it should be understood to include all modifications, equivalents and substitutes included in the spirit and scope of the present invention.

Since the present invention may have various changes and may have various forms, specific embodiments will be illustrated and described in detail below. However, this is not intended to limit the present invention to the specific disclosed form, it should be understood to include all modifications, equivalents and substitutes included in the spirit and scope of the present invention.

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

Before that, the terminology used herein is for the purpose of referring to particular embodiments only, and is not intended to limit the present invention. And, as used herein, the singular forms also include the plural forms unless the phrases clearly indicate the opposite.

According to an embodiment of the present invention, preparing a monomer composition comprising a water-soluble ethylenically unsaturated monomer having at least a partially neutralized acidic group, an internal crosslinking agent, a polymerization initiator, and a xanthate represented by the following Chemical Formula 1; polymerizing the monomer composition to form a hydrogel polymer; drying and pulverizing the hydrogel polymer to prepare a powdery base resin; and in the presence of a surface crosslinking agent, further crosslinking the surface of the base resin to form a surface crosslinking layer is provided:

[Formula 1]

In Formula 1,

M is an alkali metal,

R is an alkyl group having 1 to 10 carbon atoms.

As used herein, the term “polymer” or “polymer” refers to a polymerized state of a water-soluble ethylenically unsaturated monomer, and may cover all water content ranges or particle diameter ranges. Among the polymers, a polymer having a water content (moisture content) of about 20% by weight or more in a state before drying after polymerization may be referred to as a hydrogel polymer.

In addition, "base resin" or "base resin powder" is made by drying and pulverizing a polymer obtained by polymerization of a water-soluble ethylenically unsaturated monomer to form particles or powder, and a surface modification or surface crosslinking step described later. It means a polymer in an untreated state.

In addition, "super absorbent polymer" means the polymer or the base resin itself, depending on the context, or an additional process for the polymer or the base resin, such as surface crosslinking, fine powder reassembly, drying, grinding, classification, etc. It is used to encompass all of the products that have undergone the process and are in a state suitable for commercialization.

Recently, in order to improve the absorption rate of the superabsorbent polymer finally produced during polymerization of the superabsorbent polymer, attempts have been made to introduce a porous structure in the resin using a foaming agent during polymerization of the monomer, or to control the polymerization rate by an additive. In addition to not exhibiting a satisfactory fast absorption rate, there have been problems such as a decrease in the bulk density of the superabsorbent polymer.

Accordingly, the present inventors have found that when a water-soluble ethylenically unsaturated monomer is polymerized in the presence of a xanthate having a specific structure, the molecular weight of the polymer is reduced while the polymerization reaction rate is delayed, and the crosslinking density in the polymer is lowered, so that the superabsorbent polymer is By confirming that the initial absorption capacity and the absorption rate can be improved at the same time, the present invention was completed.

Specifically, the monomer composition prepared for the preparation of the superabsorbent polymer may be prepared in a solution state, such as an aqueous solution, and in such a monomer composition, for example, in the monomer composition in an aqueous state, represented by Formula 1 Xanthate is present in ionized form:

Accordingly, the ionized xanthate may serve as a chain-transfer agent in the polymerization step to be described later. Here, the chain transfer agent refers to a compound that serves to move a polymer growth site during polymerization. Specifically, when a chain transfer agent is present during polymerization, additional growth at the site is terminated by a leaving group that is easily released, such as a hydrogen ion in the chain transfer agent molecule, reacts with the conventional polymerization growth site, and the chain transfer agent from which the leaving group is released is a monomer. A new polymer growth site is created by reacting with Therefore, upon polymerization in the presence of a chain transfer agent, the polymerization reaction rate may be delayed, and the molecular weight of the finally produced polymer may be reduced.

That is, when the water-soluble ethylenically unsaturated monomer is polymerized with an internal crosslinking agent, when the xanthate is present, the polymerization reaction rate is delayed so that the polymerization reaction is stably carried out while at the same time the molecular weight of the polymer is reduced, thereby increasing the crosslinking density of the polymer. can be lowered Accordingly, the superabsorbent polymer prepared by polymerizing the monomer in the presence of xanthate may exhibit a significantly faster absorption rate compared to the case in which xanthate is not used.

Hereinafter, each step of the manufacturing method of the superabsorbent polymer according to an embodiment will be described in more detail.

In the method for producing a superabsorbent polymer according to an embodiment, first, a water-soluble ethylenically unsaturated monomer having at least a partially neutralized acidic group, an internal crosslinking agent, a polymerization initiator, and a monomer comprising xanthate represented by Formula 1 The steps of preparing the composition are carried out.

Here, the monomer composition may be prepared by preparing a neutralizing solution for neutralizing at least some of the acidic groups included in the water-soluble ethylenically unsaturated monomer, and then adding the xanthate to the neutralizing solution.

Specifically, preparing the monomer composition comprises:

mixing a water-soluble ethylenically unsaturated monomer having an acidic group, the internal crosslinking agent, the polymerization initiator, and a neutralizing agent to prepare a neutralized solution in which at least some of the acidic groups of the water-soluble ethylenically unsaturated monomer are neutralized; and

It may be carried out including the step of adjusting the temperature of the neutralizing solution in the range of 20 °C to 50 °C, and then adding the xanthate.

As described above, when xanthate is added after preparing the neutralized solution, there is an advantage that the temperature of the neutralized solution can be adjusted when the xanthate is added.

Specifically, the neutralization reaction of the acid group of the water-soluble ethylenically unsaturated monomer with the neutralizing agent corresponds to an exothermic reaction, so that the temperature of the neutralizing solution during the reaction rises to about 70° C., and the temperature of the neutralizing solution is raised to 50° C. through a cooling system. If xanthate is added after lowering it to below, there may be an advantage in that the absorption rate is faster. More specifically, the temperature of the neutralizing solution may be adjusted to about 20 °C to about 50 °C, or about 30 °C to 40 °C, for example, about 50 °C, about 40 °C, about 30 °C, or about 20 °C. .

In addition, as described above, the xanthate represented by Formula 1 included in the monomer composition delays the polymerization reaction rate in the polymerization step to be described later, and serves to control the molecular weight of the finally produced polymer.

However, a hypophosphite compound such as sodium hypophosphite may also play a role in controlling the molecular weight of the polymer, but it is difficult to sufficiently improve the absorption rate of the superabsorbent polymer prepared when the sodium hypophosphite is used. On the other hand, the xanthate has an intramolecular xanthine group, so that the reaction rate with the polymerization growth site is faster than that of the hypophosphite containing phosphoric acid, so that the growth rate of the polymer can be more effectively delayed, and thus the sodium hypophosphite It enables the preparation of a super absorbent polymer having a significantly improved absorption rate compared to the case of using it.

In addition, in Formula 1, R may be a linear or branched alkyl group having 1 to 6 carbon atoms. Specifically, R may be a linear alkyl group having 1 to 6 carbon atoms, for example, R may be methyl, ethyl, or propyl.

In addition, in Formula 1, M may be sodium or potassium as an alkali metal.

For example, sodium ethyl xanthate may be used as the xanthate represented by Formula 1, but is not limited thereto.

In addition, the xanthate may be used in an amount of 0.001 to 0.2 parts by weight based on 100 parts by weight of the water-soluble ethylenically unsaturated monomer. For example, the xanthate is 0.005 parts by weight or more, 0.01 parts by weight or more, 0.015 parts by weight or more, 0.02 parts by weight or more, or 0.025 parts by weight or more, and 0.15 parts by weight or less, relative to 100 parts by weight of the water-soluble ethylenically unsaturated monomer. , 0.1 parts by weight or less, or 0.075 parts by weight or less. If the content of the xanthate is too low, the growth rate of the polymer is not sufficiently delayed, so the absorption rate of the superabsorbent polymer may not be improved to the desired degree. If the content of the upper xanthate is too high, internal crosslinking Since the density is lowered, it may be difficult to implement a desired water holding capacity.

In addition, the xanthate may be used in a weight ratio of 0.01 to 1 based on the weight of the internal crosslinking agent. For example, the xanthate salt may be used in a weight ratio of 0.02 to 0.5, or 0.05 to 0.2, based on the weight of the internal crosslinking agent in terms of maintaining the water holding capacity of the superabsorbent polymer.

The water-soluble ethylenically unsaturated monomer included in the monomer composition may be any monomer commonly used in the preparation of the super absorbent polymer. As a non-limiting example, the water-soluble ethylenically unsaturated monomer may be a compound represented by the following Chemical Formula 2:

[Formula 2]

R ₁ -COOM ¹

In Formula 2,

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.

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 such, when (meth)acrylic acid and/or a salt thereof are used as the water-soluble ethylenically unsaturated monomer, it is advantageous because a superabsorbent polymer with improved water absorption can be obtained. In addition, the monomer includes 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 can be used.

Here, the water-soluble ethylenically unsaturated monomer may have an acidic group, and at least a portion of the acidic group may be neutralized by a neutralizing agent. Specifically, in the mixing of the water-soluble ethylenically unsaturated monomer having the acidic group, the internal crosslinking agent, the polymerization initiator, and the neutralizing agent, at least a portion of the acidic groups of the water-soluble ethylenically unsaturated monomer may be neutralized. Accordingly, the prepared neutralizing solution may contain a water-soluble ethylenically unsaturated monomer having an acidic group at least partially neutralized, an internal crosslinking agent, and a polymerization initiator.

In addition, as the neutralizing agent, a basic material such as sodium hydroxide, potassium hydroxide, ammonium hydroxide, etc. capable of neutralizing an acidic group may be used.

In this case, the neutralization degree of the water-soluble ethylenically unsaturated monomer, which refers to the degree of neutralization by the neutralizing agent among the acidic groups included in the water-soluble ethylenically unsaturated monomer, is 50 to 90 mol%, or, 60 to 85 mol%, or 65 to 85 mole %, or 70 to 80 mole %. 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 is precipitated and it may be difficult for the polymerization to proceed smoothly. Conversely, if the degree of neutralization is too low, the absorption power of the polymer is greatly reduced as well as It can exhibit properties like elastic rubber, which is difficult to handle.

In addition, the term 'internal crosslinking agent' used in the present specification is a term used to distinguish it from a surface crosslinking agent for crosslinking the surface of the base resin, which will be described later, and serves to crosslink the unsaturated bonds of the water-soluble ethylenically unsaturated monomers and polymerize them. do The crosslinking in the above step proceeds without a surface or an internal division, but by the surface crosslinking process of the base resin to be described later, the surface of the superabsorbent polymer finally prepared has a structure crosslinked by the surface crosslinking agent, and the inside is the internal crosslinking agent to form a crosslinked structure.

As the internal crosslinking agent, any compound may be used as long as it enables 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, butanediol di (meth) acrylate, butylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, hexanediol di (meth) ) acrylate, triethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, dipentaerythritol pentaacrylate, glycerin tri(meth)acrylate, penta 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, among them, ethylene glycol diglycidyl ether may be used.

The internal crosslinking agent may be used in an amount of 0.01 to 5 parts by weight based on 100 parts by weight of the water-soluble ethylenically unsaturated monomer. For example, the internal crosslinking agent is 0.01 parts by weight or more, 0.05 parts by weight or more, 0.1 parts by weight, or 0.3 parts by weight or more, and 5 parts by weight or less, 3 parts by weight or less, 2 parts by weight based on 100 parts by weight of the water-soluble ethylenically unsaturated monomer. part by weight or less, 1 part by weight or less, or 0.7 part by weight or less. When the content of the upper internal crosslinking agent is too low, crosslinking does not occur sufficiently and it may be difficult to implement strength above an appropriate level. If the content of the upper internal crosslinking agent is too high, the internal crosslinking density increases and it may be difficult to implement the desired water holding capacity.

In addition, the polymerization initiator may be appropriately selected depending on the polymerization method. When using the thermal polymerization method, a thermal polymerization initiator is used, and when using the photopolymerization method, a photopolymerization initiator is used, and a hybrid polymerization method (thermal and light). both of the thermal polymerization initiator and the 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, so a thermal polymerization initiator may be additionally used.

Specifically, in the monomer composition, the polymerization initiator may include both a thermal polymerization initiator and a photopolymerization initiator. At this time, when the monomer composition is prepared by preparing a neutralizing solution for neutralizing at least some of the acidic groups included in the water-soluble ethylenically unsaturated monomer, and then adding the xanthate to the neutralizing solution, the photopolymerization initiator is the acid It is mixed with a water-soluble ethylenically unsaturated monomer having a group, and the thermal polymerization initiator may be added together with the xanthate. As described above, unlike the photopolymerization initiator, the addition of a thermal polymerization initiator to the neutralization solution after the neutralization reaction, such as xanthate, is generated in the neutralization step when the thermal polymerization initiator and xanthate are included in the neutralization solution. This is because thermal polymerization is initiated by heat, so that the polymerization reaction and the reaction by xanthate may proceed.

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

As the photopolymerization initiator, for example, benzoin ether, dialkyl acetophenone, hydroxyl alkylketone, phenyl glyoxylate, benzyl dimethyl ketal Ketal), acyl phosphine (acyl phosphine) and alpha-aminoketone (α-aminoketone) may be used at least one selected from the group consisting of. 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)phenylphosphinate etc. are mentioned. A wider variety of photoinitiators are well described in Reinhold Schwalm's book "UV Coatings: Basics, Recent Developments and New Application (Elsevier 2007)" p115, but 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 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 ) and the like, and examples of the azo initiator 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-(carbamoylazo)isobutyronitrile (2-(carbamoylazo)isobutylonitril), 2,2-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride (2,2-azobis[2-(2-imidazolin-2- yl)propane] dihydrochloride), and 4,4-azobis-(4-cyanovaleric acid) (4,4-azobis-(4-cyanovaleric acid)). More various thermal polymerization initiators are well described in Odian's book 'Principle of Polymerization (Wiley, 1981)', p203, and are not limited to the above-described examples.

The 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, when the concentration of the polymerization initiator is too low, the polymerization rate may be slowed and the residual monomer may be extracted in a large amount in 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, so that the content of the water-soluble component is increased and the physical properties of the resin may be lowered, such as lowering the absorbency under pressure, which is not preferable.

In addition, when the polymerization initiator includes both a photoinitiator and a thermal polymerization initiator, the photopolymerization initiator may be used in an amount of 0.0001 to 0.1 parts by weight, or 0.0001 to 0.001 parts by weight, based on 100 parts by weight of the monomer. If the concentration of the photopolymerization initiator is too low, the polymerization rate may be slowed, and if the concentration of the photopolymerization initiator is too high, the molecular weight of the superabsorbent polymer may be small and physical properties may be non-uniform. In addition, the thermal polymerization initiator may be used in an amount of 0.001 to 1 parts by weight or less, or 0.01 to 0.5 parts by weight or less, based on 100 parts by weight of the monomer. When the concentration of the thermal polymerization initiator is too low, additional thermal polymerization hardly occurs and the effect of adding the thermal polymerization initiator may be insignificant. If the concentration of the thermal polymerization initiator is too high, the molecular weight of the superabsorbent polymer may be small and the physical properties may be non-uniform. have.

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

In addition, the monomer composition including the monomer may be in a solution state dissolved in a solvent such as water, and the solid content in the monomer composition in the solution state, that is, the concentration of the monomer, the internal crosslinking agent, and the polymerization initiator is determined by polymerization. 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 20 to 60% by weight, or 40 to 60% by weight.

When the monomer composition has a solid content in the above range, it is not necessary to remove unreacted monomers after polymerization by using the gel effect phenomenon that occurs in the polymerization reaction of a high concentration aqueous solution, and the grinding efficiency of the polymer to be described later is improved. It may be advantageous to control.

The solvent that can be used at this time can be used without limitation in its composition as long as it can dissolve the above-mentioned components, 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.

Next, a step of thermally or photopolymerizing the monomer composition to form a hydrogel polymer is performed.

In the above step, as long as the hydrogel polymer can be formed by thermal polymerization, photopolymerization, or hybrid polymerization of the prepared monomer composition, the composition may be performed without limitation.

Specifically, when the thermal polymerization is carried out, it may be carried out in a reactor having a stirring shaft such as a kneader.

In this case, the polymerization of the monomer composition may be carried out in a temperature range of about 20 to about 40 ℃. When the polymerization temperature is too high, the water holding capacity of the superabsorbent polymer may be too low or the absorption rate may be slow. If the polymerization temperature is too low, the reaction may be delayed too much and crosslinking may not be properly performed.

A means for achieving the polymerization temperature in the above range is not particularly limited, and heating may be performed by supplying a heating medium to the reactor or directly supplying a heat source. As the type of heating medium that can be used, a fluid with increased temperature such as steam, hot air, or hot oil may be used, but it is not limited thereto, and the temperature of the supplied heating medium is determined by considering the means of the heating medium, the temperature increase rate and the temperature increase target temperature. can be appropriately selected. On the other hand, the directly supplied heat source may be a heating method through electricity or a heating method through a gas, but is not limited to the above-described example.

On the other hand, when the photopolymerization is carried out, it may be carried out in a reactor equipped with a movable conveyor belt, but the polymerization method described above is an example, and the present invention is not limited to the polymerization method described above.

For example, when thermal polymerization is performed by supplying a heating medium or heating the reactor to a reactor such as a kneader having a stirring shaft as described above, the hydrogel polymer discharged to the reactor outlet can be obtained. The hydrogel polymer thus obtained may have a size of several centimeters to several millimeters depending on the shape of the stirring shaft provided in the reactor. Specifically, the size of the hydrogel polymer obtained may vary depending on the concentration and injection rate of the injected monomer composition.

In addition, when photopolymerization is performed in a reactor equipped with a movable conveyor belt as described above, the form of the hydrogel polymer obtained may be a hydrogel polymer on a sheet having the width of the belt. At this time, the thickness of the polymer sheet varies depending on the concentration and injection rate of the monomer composition to be injected, but it is preferable to supply the monomer composition so that a polymer sheet having a thickness of usually about 0.5 to about 10 cm can be obtained. When the monomer composition is supplied so that the thickness of the polymer on the sheet is too thin, the production efficiency is low, which is not preferable, and when the thickness of the polymer on the sheet exceeds 10 cm, due to the excessively thick thickness, the polymerization reaction is uniformly performed over the entire thickness. it may not happen

The polymerization time of the monomer composition is not particularly limited and may be adjusted to about 30 seconds to 60 minutes.

Typically, the water content of the hydrogel polymer obtained in this way may be about 20 to about 70 wt%. For example, the water content of the hydrogel polymer may be about 30 wt% or more, or about 35 wt% or more, and about 70 wt% or less, about 60 wt% or less, or about 50 wt% or less.

Meanwhile, throughout the present specification, "moisture content" refers to a value obtained by subtracting the weight of the polymer in a dry state from the weight of the hydrogel polymer as the content of moisture occupied 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 moisture in the polymer during drying by raising the temperature of the polymer through infrared heating. At this time, the drying condition is set to 40 minutes including 5 minutes of the temperature rise step in such a way that the temperature is raised from room temperature to about 180°C and then maintained at 180°C, and the moisture content is measured.

Next, a step of drying and pulverizing the hydrogel polymer to form a powdery base resin is performed.

As the encapsulated foaming agent is foamed by the heat applied for drying in the above step, the inside of the prepared base resin has a structure in which a plurality of pores are formed. Accordingly, it is possible to prepare a superabsorbent polymer having an improved absorption rate compared to the case in which the encapsulated foaming agent is not used.

On the other hand, the step of forming 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, a cutting Including 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-described example.

Through this coarse grinding process, the particle diameter of the hydrogel polymer can be adjusted to about 0.1 to about 10 mm. Grinding so that the particle diameter is less than 0.1 mm is not technically easy due to the high water 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 grinding process as described above or has not undergone the coarse grinding process. At this time, the drying temperature may be about 60 ℃ to about 250 ℃. At this time, when the drying temperature is less than about 70°C, the drying time is too long and the thermoplastic resin shell of the encapsulated foaming agent is difficult to soften, so that the foaming phenomenon may not occur, and when the drying temperature exceeds about 250°C, the polymer is excessively Since only the surface is dried, fine powder may be generated in the subsequent grinding process, and there is a risk that the physical properties of the superabsorbent polymer finally formed may be reduced. Therefore, preferably, the drying may be carried out at a temperature of about 100 °C to about 240 °C, more preferably at a temperature of about 110 °C to about 220 °C.

In addition, the drying time may be carried out 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.

If the drying method of the drying step is also commonly used in the drying process of the hydrogel polymer, it may be selected and used without limitation in its configuration. Specifically, the drying step may be performed by a method such as hot air supply, infrared irradiation, microwave irradiation, or ultraviolet irradiation. After the drying step, the moisture content of the polymer may be about 1 to about 5 wt%.

Thereafter, the dried polymer obtained through the drying step is pulverized using a pulverizer.

Specifically, the pulverizer used to pulverize the base resin in powder form into particles having a particle diameter of about 150 μm to about 850 μm is specifically a pin mill, a hammer mill, a screw It may be a screw mill, a roll mill, a disk mill, or a jog mill, but is not limited to the above-described examples.

Next, in the presence of a surface crosslinking agent, a step of further crosslinking the surface of the base resin to form a surface crosslinking layer is performed. Here, the additional crosslinking of the surface of the base resin means that the surface of the base resin particles constituting the powdery base resin is additionally crosslinked. Accordingly, through the above steps, the surface of each of the base resin particles is crosslinked. A surface cross-linked layer is formed on the

The above step is a step of forming a surface crosslinking layer using a surface crosslinking agent to increase the surface crosslinking density of the base resin, so that the unsaturated bonds of the water-soluble ethylenically unsaturated monomer remaining on the surface without crosslinking are crosslinked by the surface crosslinking agent. As a result, a superabsorbent polymer having an increased surface crosslinking density is formed. This heat treatment process increases the surface crosslinking density, that is, the external crosslinking density, while the internal crosslinking density does not change, so that the superabsorbent polymer with the surface crosslinked layer formed has a structure having a higher external crosslinking density than the internal crosslinking density.

As the surface cross-linking agent, any surface cross-linking agent that has been conventionally used in the production of superabsorbent polymers may be used without any particular limitation. For example, the surface crosslinking agent is ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, 1,2-hexanediol, 1,3-hexanediol, 2- One selected from the group consisting of methyl-1,3-propanediol, 2,5-hexanediol, 2-methyl-1,3-pentanediol, 2-methyl-2,4-pentanediol, tripropylene glycol and glycerol or more polyols; at least one carbonate-based compound selected from the group consisting of ethylene carbonate, propylene carbonate, and glycerol carbonate; Epoxy compounds, such as ethylene glycol diglycidyl ether; oxazoline compounds such as oxazolidinone; polyamine compounds; oxazoline compounds; mono-, di- or polyoxazolidinone compounds; or a cyclic urea compound; and the like.

Specifically, one or more, or two or more, or three or more of the above-described surface crosslinking agents may be used as the surface crosslinking agent, for example, ethylene carbonate-propylene carbonate (ECPC), propylene glycol and/or glycerol carbonate can be used.

The surface crosslinking agent may be used in an amount of about 0.001 to about 5 parts by weight based on 100 parts by weight of the base resin. For example, the surface crosslinking agent is in an amount of 0.005 parts by weight or more, 0.01 parts by weight or more, or 0.05 parts by weight or more, and 5 parts by weight or less, 4 parts by weight or less, or 3 parts by weight or less based on 100 parts by weight of the base resin. can be used By adjusting the content range of the surface crosslinking agent to the above-mentioned range, a superabsorbent polymer having excellent absorbent properties can be prepared.

In addition, the step of forming the surface crosslinking layer may be performed by adding an inorganic material to the surface crosslinking agent. That is, in the presence of the surface crosslinking agent and the inorganic material, the step of further crosslinking the surface of the base resin to form a surface crosslinking layer may be performed.

As the inorganic material, at least one inorganic material selected from the group consisting of silica, clay, alumina, silica-alumina composite, titania, zinc oxide, and aluminum sulfate may be used. The inorganic material may be used in powder form or liquid form, and in particular, may be used as alumina powder, silica-alumina powder, titania powder, or nano silica solution. In addition, the inorganic material may be used in an amount of about 0.001 to about 1 part by weight based on 100 parts by weight of the base resin.

In addition, about the method of mixing the said surface crosslinking agent with a base resin, there is no limitation of the structure. For example, a method of mixing the surface crosslinking agent and the base resin in a reaction tank, spraying the surface crosslinking agent on the base resin, or a method of continuously supplying and mixing the base resin and the surface crosslinking agent to a continuously operated mixer can be used. .

When mixing the surface crosslinking agent and the base resin, water and methanol may be mixed together and added. When water and methanol are added, there is an advantage that the surface crosslinking agent can be uniformly dispersed in the base resin. At this time, the content of the added water and methanol may be appropriately adjusted to induce even dispersion of the surface crosslinking agent, prevent agglomeration of the base resin, and at the same time optimize the surface penetration depth of the crosslinking agent.

The surface crosslinking process may be performed at a temperature of about 80 °C to about 250 °C. More specifically, the surface crosslinking process may be performed at a temperature of about 100° C. to about 220° C., or about 120° C. to about 200° C., for about 20 minutes to about 2 hours, or about 40 minutes to about 80 minutes. . When the above-described surface crosslinking process conditions are satisfied, the surface of the base resin is sufficiently crosslinked to increase absorbency under pressure.

A means for increasing the temperature for the surface crosslinking reaction is not particularly limited. It can be heated by supplying a heating medium or by directly supplying a heat source. At this time, as the type of heating medium that can be used, a fluid with increased temperature such as steam, hot air, or hot oil may be used, but it is not limited thereto, and the temperature of the supplied heating medium is determined by the means of the heating medium, the temperature increase rate and the temperature increase target temperature. Considering it, it can be appropriately selected. On the other hand, the directly supplied heat source may be a heating method through electricity or a heating method through a gas, but is not limited to the above-described example.

Meanwhile, the step may further include classifying the base resin on which the surface cross-linking layer is formed.

It is possible to manage the physical properties of the superabsorbent polymer powder to be finally manufactured through the step of classifying the base resin on which the surface cross-linking layer is formed according to particle size. It is appropriate that the superabsorbent polymer obtained therefrom is prepared and provided to have a particle diameter of about 150 to 850 μm through such processes such as pulverization and classification. More specifically, at least about 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 the fine powder having a particle diameter of less than about 150 μm may be less than about 3% by weight.

As described above, as the particle size distribution of the superabsorbent polymer is adjusted to a desirable range, the final manufactured superabsorbent polymer may exhibit excellent absorbent properties. Therefore, in the classification step, the polymer having a particle diameter of about 150 to about 850 μm may be classified and commercialized.

In the method of manufacturing the superabsorbent polymer according to the embodiment, the type and content of the basic material, the type and content of the encapsulated foaming agent, and the temperature and/or time conditions of the subsequent polymerization process (drying process or surface crosslinking reaction process) are appropriately adjusted. It is possible to provide a superabsorbent polymer having a desired level of absorption rate and initial absorption capacity by controlling it. Such superabsorbent polymers can exhibit significantly improved absorption capacity and absorption rate in 1 minute compared to superabsorbent polymers prepared by polymerization without the presence of xanthate.

Meanwhile, according to another embodiment of the present invention, there is provided a superabsorbent polymer having an absorption rate of 50 seconds or less by a vortex method as a superabsorbent polymer manufactured according to the above-described manufacturing method. At this time, the absorption rate by the vortex method (Vortex) is defined as the time during which the vortex of the liquid disappears due to rapid absorption when the superabsorbent polymer is added to physiological saline and stirred. The measuring method is more concrete in the following examples. Specifically, the absorption rate is 60 seconds or less, 55 seconds or less, or 50 seconds or less, and the smaller the value, the better, the lower limit of the absorption rate is 0 seconds in theory, but for example 10 seconds or more, 15 seconds or more, 20 more than a second, or more than 30 seconds.

In addition, as the superabsorbent polymer prepared according to the above-described manufacturing method, the superabsorbent polymer having an absorption capacity (distilled water) of 70 g/g or more in 1 minute is provided. In this case, the absorption capacity in 1 minute is defined as the total amount of distilled water that can be absorbed in 1 minute when the superabsorbent polymer is immersed in distilled water, and the method of measuring the absorption capacity in 1 minute is more detailed in Examples below. Specifically, the one-minute water absorption capacity of the superabsorbent polymer is 70 g/g or more, 75 g/g or more, or 80 g/g or more, and the higher the value, the better, and there is no upper limit on the one-minute water absorption capacity. 150 g/g or less, 120 g/g or less, or 100 g/g or less.

In addition, the superabsorbent polymer prepared according to the above-described manufacturing method has a water holding capacity (CRC) of 25 g/g or more, or 28 g/g or more, or 29 g/g or more, measured according to EDANA method WSP 241.3, 40 g/g or less, or 38 g/g or less, or 35 g/g or less.

In addition, the super absorbent polymer prepared according to the above-described manufacturing method has an absorbency under pressure (AUP) of 18 g/g or more, or 19 g/g or more, or 20 g/g at 0.7 psi measured according to EDANA method WSP 242.3. or more, and may be 24 g/g or less, or 23 g/g or less.

Hereinafter, preferred embodiments are presented to help the understanding of the invention. However, the following examples are only for illustrating the invention, and do not limit the invention thereto.

[Example] Preparation of super absorbent polymer

Example 1

In 500 g of acrylic acid in a vessel, 2.25 g of polyethylene glycol diacrylate (PEGDA, Mw = 523) as a crosslinking agent (0.45 parts by weight relative to 100 parts by weight of acrylic acid), diphenyl (2,4,6-trimethylbenzoyl)-phosphate as a photopolymerization initiator 0.04 g of pin oxide was added and dissolved, and 640 g of 25.1% caustic soda (NaOH) and 170 g of water were mixed and stirred in another vessel. After 30 minutes, caustic soda (NaOH) and an aqueous solution of water were mixed with an acrylic acid mixture vessel using a pump to prepare a neutralized solution. At this time, the temperature of the neutralizing solution was increased to 70°C.

After cooling the temperature of the neutralization solution to 30° C. using a cooling jacket, 0.025 parts by weight of sodium ethyl xanthate compared to 100 parts by weight of acrylic acid, sodium persulfate, a thermal polymerization initiator, was added to the cooled neutralized solution. , SPS) was added in 0.24 parts by weight based on 100 parts by weight of acrylic acid to prepare a monomer composition having a total solids concentration of 45.6% by weight. The degree of neutralization of the acrylic acid in the prepared monomer composition was 73 mol%.

The monomer composition was fed at a rate of 500 to 2000 mL/min on a conveyor belt in which a belt having a width of 10 cm and a length of 2 m was rotated at a speed of 50 cm/min. Then, at the same time as the supply of the monomer composition, ^{ultraviolet rays having an intensity of 10 mW/cm 2} were irradiated for 60 seconds, and then heat of 80 degrees was irradiated for 120 seconds to proceed with thermal polymerization.

After the hydrogel polymer obtained through the polymerization reaction was pulverized to a size of 2 mm * 2 mm, the water content was measured and found to be 40.1%. After adding 180 g of water to the pulverized hydrogel polymer, it was evenly buried, and then passed through a hole having a diameter of 10 mm using a meat chopper to prepare a crumb. Then, using a convection oven that can transfer the air volume up and down, hot air at 185° C. is flowed from the bottom to the top for 20 minutes, and then flows from the top to the bottom for 20 minutes to dry the powder uniformly. did it The dried powder was pulverized to prepare a powdery base resin.

To 100 g of the base resin prepared above, a solution of 5.4 g of ultrapure water, ethylene carbonate-propylene carbonate (ECPC) 1.8 g, propylene glycol (PG) 0.2 g, glycerol carbonate 0.6 g, and aluminum sulfate 0.4 g was mixed and stirred. and mixed for 1 minute, then surface crosslinking reaction was performed at 186° C. for 60 minutes. Thereafter, it was classified to obtain a superabsorbent polymer composed of particles having an average particle diameter of 150 to 850 μm.

Example 2

In Example 1, the same method as in Example 1 was used, except that 0.55 parts by weight of the internal crosslinking agent PEGDA was used based on 100 parts by weight of acrylic acid, and 0.05 parts by weight of sodium ethyl xanthate was used based on 100 parts by weight of acrylic acid. was used to prepare a super absorbent polymer.

Example 3

In Example 1, the same method as in Example 1 was used, except that 0.70 parts by weight of the internal crosslinking agent PEGDA was used based on 100 parts by weight of acrylic acid, and 0.075 parts by weight of sodium ethyl xanthate was used based on 100 parts by weight of acrylic acid. was used to prepare a super absorbent polymer.

Example 4

A superabsorbent polymer was prepared in the same manner as in Example 1, except that in Example 1, the neutralizing solution was cooled to 40° C. and then sodium ethyl xanthate was added.

Comparative Example 1

A superabsorbent polymer was prepared in the same manner as in Example 4, except that in Example 4, sodium ethyl xanthate was not used and 0.35 g of the internal crosslinking agent PEGDA was used.

Comparative Example 2

A superabsorbent polymer was prepared in the same manner as in Example 4, except that sodium hypophosphite was used instead of sodium ethyl xanthate in Example 4.

Comparative Example 3

A superabsorbent polymer was prepared in the same manner as in Example 4, except that sodium ethyl xanthate was not used in Example 4.

test example

For the superabsorbent polymers prepared in Examples and Comparative Examples, centrifugation retention capacity (CRC), absorbency under pressure (AUP), absorption rate and one-minute absorption capacity were measured in the following manner, and the results are shown in Table 1 below. indicated.

(1) Centrifuge Retention Capacity (CRC)

The water holding capacity of each resin according to the no-load absorption magnification was measured according to the European Disposables and Nonwovens Association (EDANA) standard EDANA WSP 241.3.

Specifically, from the resins obtained through Examples and Comparative Examples, a resin classified through a sieve of #30-50 was obtained. This resin W ₀ (g) (about 0.2 g) was uniformly put in a non-woven bag and sealed, and then immersed in physiological saline (0.9 wt %) at room temperature. After 30 minutes, the bag was drained of water for 3 minutes under the conditions of 250G using a centrifuge, and the mass W ₂ (g) of the bag was measured. Further, after the same operation without using the resin then the weight W ₁ (g) was measured.

CRC (g/g) was calculated according to the following Equation 1 using each obtained mass.

[Equation 1]

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

(2) Absorbency under Pressure (AUP: Absorbency under Pressure)

The absorbency under pressure of 0.7 psi of the superabsorbent polymers of Examples and Comparative Examples was measured according to WSP 242.3 of the EDANA method.

First, in the measurement of the absorbency under pressure, the fraction of the resin in the CRC measurement was used.

Specifically, a stainless steel 400 mesh wire mesh was mounted on the bottom of a plastic cylinder having an inner diameter of 25 mm. Under the conditions of room temperature and humidity of 50%, the water absorbent resin W ₀ (g) (0.16 g) is uniformly sprayed on the wire mesh, and the piston that can further apply a load of 0.7 psi on it is slightly smaller than the outer diameter of 25 mm. There is no gap between the inner wall of the cylinder and the vertical movement is not disturbed. 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 inside a petro dish having a diameter of 150 mm, and physiological saline composed of 0.9 wt% sodium chloride was placed at the same level as the upper surface of the glass filter. One filter paper having a diameter of 90 mm was loaded thereon. The measuring device was placed on the filter paper, and the liquid was absorbed under load for 1 hour. After 1 hour, the measuring device was lifted and the weight W ₄ (g) was measured.

The absorbency under pressure (g/g) was calculated according to the following Equation 2 using each obtained mass.

[Equation 2]

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

(3) Absorption rate by vortex method

The absorption rates of the superabsorbent polymers of Examples and Comparative Examples were measured in seconds according to the method described in International Patent Publication No. 1987-003208.

Specifically, for the absorption rate (or vortex time), 2 g of superabsorbent resin is added to 50 mL of physiological saline at 23°C to 24°C, and a magnetic bar (diameter 8 mm, length 31.8 mm) is stirred at 600 rpm to vortex. It was calculated by measuring the time until the (vortex) disappears in seconds.

(4) 1 minute absorption capacity

_{1.0 g (W 5} ) of the superabsorbent polymer of Examples and Comparative Examples was placed in a nonwoven bag (15 cm × 15 cm) and immersed in 500 mL of distilled water at 24° C. for 1 minute. After 1 minute, the bag was taken out of the distilled water, hung and left for 1 minute. Then, the mass (W ₆ ) of the envelope was measured. In addition, after the same operation was performed without using the superabsorbent polymer, the mass W ₇ (g) at that time was measured.

Using each mass thus obtained, the absorption capacity for 1 minute was calculated according to Equation 3 below.

[Equation 3]

1 minute absorption capacity (distilled water) = {[W ₇ (g) - W ₆ (g) - W ₅ (g)]/W ₅ (g)}

neutralizing liquid
Temperature
(℃) inside
crosslinking agent
content ¹⁾ ethyl
xanthic acid
salt
content ²⁾ Properties CRC
(g/g) AUP
(g/g) absorption
speed
(second) 1 minute absorption
(g/g) Example 1 30 0.45 0.025 33.2 22.8 41 90 Example 2 30 0.55 0.050 34.5 21.0 46 82 Example 3 30 0.70 0.075 35.1 20.5 48 80 Example 4 40 0.45 0.025 32.5 22.5 49 75 Comparative Example 1 40 0.35 - 33.5 22.0 61 69 Comparative Example 2 40 0.45 hypophosphorous acid
salt
0.025 34.0 20.6 65 64 Comparative Example 3 40 0.45 - 32.8 22.4 63 73

1) and 2) parts by weight based on 100 parts by weight of acrylic acid

Referring to Table 1, it can be seen that the superabsorbent polymer of Examples exhibits significantly improved initial absorption capacity and faster absorption rate compared to the superabsorbent polymers of Comparative Examples not using xanthate and Comparative Examples using sodium hypophosphite during polymerization. can

Claims (12)

Preparing a monomer composition comprising a water-soluble ethylenically unsaturated monomer having at least a partially neutralized acidic group, an internal crosslinking agent, a polymerization initiator, and a xanthate represented by the following Chemical Formula 1;
polymerizing the monomer composition to form a hydrogel polymer;
drying and pulverizing the hydrogel polymer to prepare a powdery base resin; and
In the presence of a surface crosslinking agent, further crosslinking the surface of the base resin to form a surface crosslinking layer,
Method for preparing super absorbent polymer:
[Formula 1]

In Formula 1,
M is an alkali metal,
R is an alkyl group having 1 to 10 carbon atoms.
According to claim 1,
The step of preparing the monomer composition,
mixing a water-soluble ethylenically unsaturated monomer having an acidic group, the internal crosslinking agent, the polymerization initiator, and a neutralizing agent to prepare a neutralized solution in which at least some of the acidic groups of the water-soluble ethylenically unsaturated monomer are neutralized; and
After adjusting the temperature of the neutralizing solution in the range of 20 ℃ to 50 ℃, comprising the step of adding the xanthate,
A method for producing a super absorbent polymer.
According to claim 1,
In Formula 1,
M is sodium or potassium,
R is methyl, ethyl, or propyl;
A method for producing a super absorbent polymer.
According to claim 1,
The xanthate is used in an amount of 0.001 to 0.2 parts by weight based on 100 parts by weight of the water-soluble ethylenically unsaturated monomer,
A method for producing a super absorbent polymer.
According to claim 1,
The internal crosslinking agent is used in an amount of 0.01 to 5 parts by weight based on 100 parts by weight of the water-soluble ethylenically unsaturated monomer,
A method for producing a super absorbent polymer.
According to claim 1,
The xanthate is used in a weight ratio of 0.01 to 1 based on the weight of the internal crosslinking agent,
Manufacturing method of super absorbent polymer
According to claim 1,
The polymerization of the monomer composition proceeds in a temperature range of 20 to 40 ℃,
A method for producing a super absorbent polymer.
3. The method of claim 2,
The polymerization initiator includes a photopolymerization initiator and a thermal polymerization initiator,
The photopolymerization initiator is mixed with the water-soluble ethylenically unsaturated monomer,
The thermal polymerization initiator is added together with the xanthate,
A method for producing a super absorbent polymer.
According to claim 1,
The hydrogel polymer has a moisture content of 20 to 70% by weight,
A method for producing a super absorbent polymer.
According to claim 1,
The surface crosslinking agent is ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, 1,2-hexanediol, 1,3-hexanediol, 2-methyl-1, at least one polyol selected from the group consisting of 3-propanediol, 2,5-hexanediol, 2-methyl-1,3-pentanediol, 2-methyl-2,4-pentanediol, tripropylene glycol and glycerol; at least one carbonate-based compound selected from the group consisting of ethylene carbonate, propylene carbonate, and glycerol carbonate; Epoxy compounds, such as ethylene glycol diglycidyl ether; oxazoline compounds such as oxazolidinone; polyamine compounds; oxazoline compounds; mono-, di- or polyoxazolidinone compounds; or a cyclic urea compound,
A method for producing a super absorbent polymer.
According to claim 1,
In the step of forming the surface crosslinking layer, at least one inorganic material selected from the group consisting of silica, clay, alumina, silica-alumina composite, titania, zinc oxide and aluminum sulfate is added to the surface crosslinking agent. performed by
A method for producing a super absorbent polymer.
According to claim 1,
The prepared superabsorbent polymer has an absorption rate of 60 seconds or less by the vortex method, and an absorption capacity of 70 g/g or more in 1 minute,
A method for producing a super absorbent polymer.