KR20230062096A - Super absorbent polymer composition and preparation method thereof - Google Patents

Abstract

The present invention relates to a superabsorbent polymer composition and a method for preparing the same. More specifically, it relates to a method for preparing a superabsorbent polymer composition capable of suppressing aggregation of a water-containing gel polymer and improving pulverization processability in a pulverization process by including an additive having a specific structure.

Description

Super absorbent polymer composition and method for preparing the same {SUPER ABSORBENT POLYMER COMPOSITION AND PREPARATION METHOD THEREOF}

The present invention relates to a superabsorbent polymer composition and a method for preparing the same. More specifically, it relates to a method for preparing a superabsorbent polymer composition capable of suppressing aggregation of a water-containing gel polymer and improving pulverization processability in a pulverization process by including an additive having a specific structure.

Super Absorbent Polymer (SAP) is a synthetic high-molecular substance that has the ability to absorb moisture 500 to 1,000 times its own weight. Material), etc., are named by different names. The superabsorbent polymer as described above has begun to be put into practical use as a sanitary tool, and is currently widely used as a material for gardening soil remediation agents, civil engineering and construction waterstop materials, seedling sheets, freshness retainers in the field of food distribution, and steaming. .

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

As described above, in the case of a sanitary material in which the pulp content is reduced or pulp is not used, the super absorbent polymer is included in a relatively high ratio, so that the super absorbent polymer particles are inevitably included in multiple layers in the sanitary material. In order for the entire superabsorbent polymer particles included in multiple layers to more efficiently absorb a large amount of liquid such as urine, the superabsorbent polymer basically needs to exhibit high absorption performance as well as a fast absorption rate.

On the other hand, such superabsorbent polymers are generally prepared by polymerizing monomers to prepare a water-containing gel polymer containing a large amount of water, and coarsely pulverizing and drying the water-containing gel polymer, and then pulverizing the water-containing gel polymer into resin particles having a desired particle size. are manufactured In particular, in the process of coarsely pulverizing the hydrogel polymer, there has been a problem that the pulverization is not easily performed because the coarsely pulverized hydrogel polymers agglomerate or agglomerate with each other.

Accordingly, in addition to improving the water retention capacity (CRC), which is a physical property that represents the basic absorption and water retention capacity of the superabsorbent polymer, and the absorbency under load (AUP), which represents the property of retaining the absorbed liquid well even under external pressure, the absorption rate of the superabsorbent polymer The development of technology that can improve the process and technology that can improve the pulverization process is continuously requested.

Accordingly, the present invention relates to a method for preparing a superabsorbent polymer composition capable of suppressing aggregation of a water-containing gel polymer and improving pulverization processability in a pulverization process by including an additive having a specific structure.

In order to solve the above problems, the present invention,

superabsorbent polymer particles comprising a crosslinked polymer of a water-soluble ethylenically unsaturated monomer having an acidic group and an internal crosslinking agent; and

Provided is a superabsorbent polymer composition comprising at least one additive selected from the group consisting of a carboxylic acid represented by Formula 1 and a salt thereof:

[Formula 1]

In Formula 1,

R is straight-chain or branched-chain alkyl of 6 to 18 carbon atoms or straight-chain or branched-chain alkenyl of 6 to 18 carbon atoms.

In addition, the present invention,

crosslinking polymerization of a water-soluble ethylenically unsaturated monomer having an acidic group in the presence of an internal crosslinking agent and a polymerization initiator to form a polymer (step 1);

neutralizing at least some of the acid groups of the polymer (step 2);

Preparing base resin particles by atomizing the polymer in the presence of at least one additive selected from the group consisting of carboxylic acids represented by Formula 1 and salts thereof (step 3); and

Including the step of drying the base resin particles (step 4),

A method for preparing a superabsorbent polymer composition is provided:

[Formula 1]

In Formula 1,

R is straight-chain or branched-chain alkyl of 6 to 18 carbon atoms or straight-chain or branched-chain alkenyl of 6 to 18 carbon atoms.

According to the superabsorbent polymer composition and the manufacturing method of the present invention, the pulverization processability can be improved by adding a carboxylic acid-based additive having a specific structure during the hydrogel polymer pulverization process to suppress the aggregation of the hydrogel polymer particles. Absorption performance and absorption rate of the superabsorbent polymer may be improved.

1 is a flowchart of a conventional manufacturing method of superabsorbent polymer.
2 is H-NMR data of the additive of Chemical Formula 1 synthesized in Example 1.
3 is a photograph showing an example of evaluation item ◎ in the first evaluation of particle aggregation characteristics.
4 is a photograph showing an example of evaluation item ○ in the first evaluation of particle aggregation characteristics.
5 is a photograph showing an example of the evaluation item △ in the first evaluation of particle aggregation characteristics.
6 is a photograph showing an example of evaluation item X in the first evaluation of particle aggregation characteristics.

Terms used in this specification are only used to describe exemplary embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, terms such as "comprise", "comprise" or "having" are intended to indicate that there is an embodied feature, step, component, or combination thereof, but one or more other features or steps; It should be understood that the presence or addition of components, or combinations thereof, is not previously excluded.

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

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

Prior to that, technical terms used herein are only for referring to specific embodiments and are 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.

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

Also, the term "superabsorbent polymer particles" refers to a particulate material comprising a crosslinked polymer in which a water-soluble ethylenically unsaturated monomer containing an acidic group is polymerized and crosslinked by an internal crosslinking agent.

In addition, the term “superabsorbent polymer” means a crosslinked polymer obtained by polymerizing a water-soluble ethylenically unsaturated monomer containing an acidic group, or a base resin in powder form composed of superabsorbent polymer particles obtained by pulverizing the crosslinked polymer, depending on the context. or, for the crosslinked polymer or the base resin, an additional process such as neutralization (including both neutralization before polymerization and neutralization after polymerization), surface crosslinking, fine powder reassembly, drying, pulverization, classification, etc. It is used to cover everything that has been put into a state suitable for commercialization. Accordingly, the term "super absorbent polymer composition" may be interpreted as a composition including a super absorbent polymer, that is, a plurality of super absorbent polymer particles.

Also, the term "fine powder" refers to particles having a particle diameter of less than 150 μm among the superabsorbent polymer particles. The particle diameter of these resin particles may be measured according to the European Disposables and Nonwovens Association (EDANA) standard EDANA WSP 220.3 method.

In addition, the term "micronization or chopping" refers to cutting the water-containing gel polymer into small pieces in millimeter units to increase drying efficiency, and is used separately from pulverization to the level of micrometers or normal particles.

On the other hand, conventional super absorbent polymers are formed by cross-linking polymerization of water-soluble ethylenically unsaturated monomers having at least partially neutralized acidic groups in the presence of an internal cross-linking agent and polymerization initiator to form a water-containing gel polymer, drying the water-containing gel polymer formed in this way, and then forming a desired particle size. At this time, a chopping process of cutting the water-containing gel polymer into particles of several millimeters in size is usually carried out before the drying process to facilitate drying of the water-containing gel polymer and increase the efficiency of the grinding process. . However, due to the stickiness of the hydrogel polymer in this chopping process, the hydrogel polymer cannot be pulverized to the level of micro-sized particles and becomes an aggregated gel. When the water-gel polymer in the form of an aggregated gel is dried, a plate-shaped dry body is formed, and in order to grind it to the level of micro-sized particles, it must go through a multi-stage grinding process, so there has been a problem that many fine particles are generated in this process. .

Specifically, FIG. 1 is a flowchart of a conventional method for manufacturing a superabsorbent polymer. Referring to FIG. 1, conventional superabsorbent polymers have been manufactured by including the following steps.

(neutralization) neutralizing at least a part of the acidic groups of the water-soluble ethylenically unsaturated monomer;

(Polymerization) forming a water-containing gel polymer by crosslinking polymerization of a water-soluble ethylenically unsaturated monomer having an acidic group at least partially neutralized in the presence of an internal crosslinking agent and a polymerization initiator;

(Chopping) chopping the water-containing gel polymer;

(Drying) drying the chopped hydrogel polymer; and

(grinding/classifying) pulverizing the dried polymer and then classifying it into normal particles and fine powder;

As described above, the chopped water-containing gel polymer has an aggregated gel form with a size of about 1 cm to 10 cm. dried by hot air. Since the polymer dried by the drying method exhibits a plate shape rather than a particle shape, the step of classifying after grinding is coarsely pulverized and classified so that the particles to be produced become normal particles, that is, particles having a particle diameter of 150 μm to 850 μm It has been carried out in the step of classifying after pulverization again. Since the amount of the fine powder separated in the final classification step by this manufacturing method is about 10% to about 20% by weight based on the total weight of the finally manufactured superabsorbent polymer, the separated fine powder is mixed with an appropriate amount of water to recycle the fine powder. After assembly, it was reused by putting it in the chopping step or the step before drying.

However, problems such as causing an increase in equipment load and/or energy consumption have occurred when the reassembly of the fine powder mixed with water for reuse of the fine powder is re-entered into the grinding or drying process, and the remaining fine powder that has not been classified This caused the deterioration of the physical properties of the superabsorbent polymer.

Therefore, the present inventors have found that the amount of fine powder generated in the conventional manufacturing method has a large influence in the grinding process, and in the process of chopping it (micronization process), the present inventors add a surfactant to grind them more finely than before, while at the same time preventing aggregation By controlling the production of particles in the form of agglomerated fine particles, it was noted that the amount of fine powder generated during the manufacturing process can be significantly reduced.

On the other hand, when a surfactant is added to the neutralized water-containing gel polymer, the surfactant penetrates into the inside of the water-containing gel polymer rather than existing at the interface of the water-containing gel polymer due to the high water content of the neutralized water-containing gel polymer. There is a problem with not fulfilling the role properly.

As a result of repeated research to solve this problem, polymerization is not carried out in a state where the acidic groups of the water-soluble ethylenically unsaturated monomers are neutralized, as in the conventional manufacturing method of superabsorbent polymer, but polymerization is first carried out in a state where the acidic groups are not neutralized, resulting in polymer After forming, and then neutralizing the acid group of the polymer to form a water-containing gel polymer, the water-containing gel polymer is atomized in the presence of a surfactant, or when the acid group present in the polymer is neutralized simultaneously with the atomization, the surfactant is It was confirmed that it is present in a large amount on the surface and can sufficiently play a role of preventing the polymer from excessive aggregation by lowering the high adhesiveness of the polymer and controlling the aggregation state to a desired level.

Accordingly, as the secondary particles in which the primary particles are aggregated form the polymer, and then the pulverization and drying processes proceed under milder conditions, the amount of fine powder generated during the process can be significantly reduced.

In addition, when the polymer is pulverized in the presence of a carboxylic acid-based additive having a specific structure of Formula 1 as described above, the hydrophobic functional group included in the additive imparts hydrophobicity to the surface of the pulverized superabsorbent polymer particles, resulting in frictional force between the particles. While increasing the apparent density of the super absorbent polymer by relaxing the surface tension of the super absorbent polymer, the hydrophilic functional group included in the additive is also bonded to the super absorbent polymer particles so that the surface tension of the polymer is not lowered. Accordingly, the superabsorbent polymer prepared according to the above-described manufacturing method may have a high apparent density value while exhibiting an equivalent level of surface tension compared to a resin without using such an additive.

In addition, if polymerization is first performed in an unneutralized state to form a polymer and then acid groups present in the polymer are neutralized, a longer chain polymer can be formed and the crosslinking is incomplete, so that the water-soluble component present in an uncrosslinked state It is possible to achieve the effect of reducing the content of.

Since the water-soluble component has a property of being easily eluted when the superabsorbent polymer comes into contact with a liquid, when the content of the water-soluble component is high, most of the eluted water-soluble component remains on the surface of the superabsorbent polymer and makes the superabsorbent polymer sticky. This causes the permeability to decrease. Therefore, it is important to keep the content of water-soluble components low in terms of liquid permeability.

In summary, when the present inventors pulverize a polymer by mixing at least one additive selected from the group consisting of a carboxylic acid having a specific structure represented by the following Chemical Formula 1 and a salt thereof, the pulverized water-containing gel polymer particles are placed together. It was confirmed that the aggregation was suppressed and the grinding processability was improved, and the present invention was completed. Particularly, the particles included in the superabsorbent polymer composition prepared according to the above manufacturing method are characterized in that they exhibit an improved absorption rate compared to the case where the additive is not used.

[Formula 1]

In Formula 1,

R is straight-chain or branched-chain alkyl of 6 to 18 carbon atoms or straight-chain or branched-chain alkenyl of 6 to 18 carbon atoms.

Specifically, the additive represented by Chemical Formula 1 has a hydrophobic functional group and a hydrophilic functional group at the same time. On the other hand, since the water-soluble ethylenically unsaturated monomer contains an acidic group (-COOH) and/or a neutralized acidic group ( ^-COO- ), the surface of the polymer produced by polymerization has an acidic group (- COOH) and/or a large amount of hydrophilic moieties by neutralized acidic groups ( ^-COO- ). Therefore, when the additive is mixed with the polymer, the hydrophilic functional group of the additive is adsorbed to at least some of the hydrophilic portions present on the surface of the polymer, and the surface of the polymer to which the additive is adsorbed has a hydrophobic surface located at the other end of the additive. Hydrophobicity is indicated by the functional group. Accordingly, aggregation between the pulverized water-containing gel polymer particles may be suppressed.

Hereinafter, the superabsorbent polymer composition of one embodiment will be described in more detail for each component.

(Super absorbent polymer composition)

According to one embodiment of the invention, the superabsorbent polymer particles comprising a crosslinked polymer of a water-soluble ethylenically unsaturated monomer having an acidic group and an internal crosslinking agent; and at least one additive selected from the group consisting of a carboxylic acid represented by Formula 1 below and a salt thereof (hereinafter, referred to as “carboxylic acid-based additive”).

[Formula 1]

In Formula 1,

R is straight-chain or branched-chain alkyl of 6 to 18 carbon atoms or straight-chain or branched-chain alkenyl of 6 to 18 carbon atoms.

The superabsorbent polymer composition of one embodiment includes superabsorbent polymer particles including a crosslinked polymer of a water-soluble ethylenically unsaturated monomer having an acidic group and an internal crosslinking agent. At this time, the crosslinked polymer is obtained by crosslinking polymerization of the water-soluble ethylenically unsaturated monomer having an acidic group in the presence of an internal crosslinking agent, and has a three-dimensional network structure in which main chains formed by polymerization of the monomers are crosslinked by the internal crosslinking agent. .

In other words, the superabsorbent polymer composition of one embodiment includes superabsorbent polymer particles including a crosslinked polymer between a water-soluble ethylenically unsaturated monomer having an acidic group and an internal crosslinking agent. As such, when the crosslinked polymer has a three-dimensional network structure in which the main chains formed by polymerization of the monomers are crosslinked by the internal crosslinking agent, compared to a case where the crosslinked polymer has a two-dimensional linear structure not additionally crosslinked by the internal crosslinking agent. The water retention capacity and absorbency under pressure, which are all physical properties of the superabsorbent polymer, can be remarkably improved.

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

[Formula 2]

R-COOM'

In Formula 2,

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

M' 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 its salt is used as the water-soluble ethylenically unsaturated monomer, it is advantageous to obtain a superabsorbent polymer with improved water absorbency. In addition, the monomers include maleic anhydride, fumaric acid, crotonic acid, itaconic acid, 2-acryloylethanesulfonic acid, 2-methacryloylethanesulfonic acid, 2-(meth)acryloylpropanesulfonic acid or 2-(meth)acryloylethanesulfonic acid. ) Acrylamide-2-methyl propane sulfonic acid, (meth)acrylamide, N-substituted (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, methoxypolyethylene Glycol (meth)acrylate, polyethylene glycol (meth)acrylate, (N,N)-dimethylaminoethyl (meth)acrylate, (N,N)-dimethylaminopropyl (meth)acrylamide and the like can be used.

Here, the water-soluble ethylenically unsaturated monomer has acidic groups, and at least some of the acidic groups are neutralized by a neutralizing agent in a neutralization step to be described later. In this case, as the neutralizing agent, basic materials such as sodium hydroxide, potassium hydroxide, and ammonium hydroxide capable of neutralizing acidic groups may be used, which will be described in detail in the manufacturing method section to be described later.

In addition, the term 'internal cross-linking agent' used herein is a term used to distinguish it from the surface cross-linking agent for cross-linking the surface of the superabsorbent polymer particles described later, and polymerization by cross-linking the unsaturated bonds of the above-described water-soluble ethylenically unsaturated monomers play a role in Crosslinking in this step proceeds regardless of surface or internal crosslinking, but when the surface crosslinking process of the superabsorbent polymer particles described later proceeds, the surface of the finally prepared superabsorbent polymer particles has a structure crosslinked by a surface crosslinking agent, The inside is made up of a cross-linked structure by the internal cross-linking agent.

As the internal crosslinking agent, any compound may be used as long as it enables the introduction of crosslinking bonds 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, polyethylene glycol di( 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 Multifunctional crosslinkers such as (meth)acrylate, pentaerythol tetraacrylate, triarylamine, pentaerythol triallyl ether, ethylene glycol diglycidyl ether, propylene glycol, glycerin, or ethylene carbonate are used alone or in combination The above may be used in combination, but is not limited thereto. Preferably, among them, pentaerythol triallyl ether may be used.

The cross-linking polymerization of the water-soluble ethylenically unsaturated monomer in the presence of such an internal cross-linking agent may be carried out by thermal polymerization, photo-polymerization or co-polymerization in the presence of a polymerization initiator and, if necessary, a thickener, a plasticizer, a storage stabilizer, an antioxidant, and the like. However, the specific details will be described later.

The superabsorbent polymer particles may have a particle size of about 150 to about 850 μm, and this particle size may be measured according to the European Disposables and Nonwovens Association (EDANA) standard EDANA WSP 220.3 method.

In addition, the superabsorbent polymer composition includes at least one additive selected from the group consisting of carboxylic acids represented by Formula 1 and salts thereof. As described above, the additive is mixed with the polymer and added so that the pulverization (chopping) step can be easily performed without agglomeration.

Specifically, the additive is selected from the group consisting of a carboxylic acid represented by Formula 1, an alkali metal salt of a carboxylic acid represented by Formula 1, and an alkaline earth metal salt of a carboxylic acid represented by Formula 1 .

Specifically, in the carboxylic acid additive represented by Formula 1, the hydrophobic functional group is an alkyl (R) having 6 to 18 carbon atoms, which is a terminal functional group, and the hydrophilic functional group is a carboxyl group (COOH) or a carboxylate group (COO ^- ) in the case of a salt. , The hydrophobic functional group and the hydrophilic functional group are located at both ends of the additive, respectively. In particular, the carboxylic acid-based additive includes carboxyl groups at two terminals to improve adsorption performance to the polymer surface. Accordingly, the additive having the structure of Chemical Formula 1 has superior adsorption performance to the surface of a hydrophilic polymer compared to a compound having a single structure of a hydrophobic functional group-hydrophilic functional group, and can effectively suppress aggregation of superabsorbent polymer particles. can

In Formula 1, the hydrophobic functional group is a terminal functional group, R, which is a straight-chain or branched chain alkyl having 6 to 18 carbon atoms or a linear or branched-chain alkenyl having 6 to 18 carbon atoms. At this time, when R is alkyl or alkenyl having less than 6 carbon atoms, there is a problem in that the chain length is short and the aggregation control of the pulverized particles is not effectively achieved, and when R is alkyl or alkenyl having more than 18 carbon atoms, the mobility of the additive (mobility) may be reduced so that it may not be effectively mixed with the polymer, and there may be a problem that the cost of the composition increases due to the increase in the cost of the additive.

Preferably, R may be a linear alkyl or linear alkenyl having 6 to 18 carbon atoms. The case where R is a straight-chain alkyl or alkenyl is more advantageous in terms of suppressing aggregation of branched-chain particles and improving dispersibility. Specifically, in Formula 1, when R is a linear alkyl having 6 to 18 carbon atoms, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decanyl, n-undecanyl, n-dodecyl. canyl, n-tridecanyl, n-tetradecanyl, n-pentadecanyl, n-hexadecanyl, n-heptadecanyl, or n-octadecanyl, or linear alkenyl of 6 to 18 carbon atoms. In the case of 2-hexenyl, 2-heptenyl, 2-octenyl, 2-nonenyl, n-dekenyl, 2-undecenyl, 2-dodekenyl, 2-tridekenyl, 2-tetradekenyl, 2-pentadekenyl, 2-hexadecenyl, 2-heptadekenyl, or n-octadekenyl.

The additive may be selected from carboxylic acids represented by Formulas 1-1 to 1-8 below:

[Formula 1-1]

[Formula 1-2]

[Formula 1-3]

[Formula 1-4]

[Formula 1-5]

[Formula 1-6]

[Formula 1-7]

[Formula 1-8]

In Formulas 1-1 to 1-8,

M ₁ and M ₂ are each independently an alkali metal or an alkaline earth metal.

The additive may be included in an amount of 0.01 to 10 parts by weight based on 100 parts by weight of the water-soluble ethylenically unsaturated monomer. If the total content of the additives compared to the monomers in the composition is too low, the effect of controlling aggregation by the additives is low, and superabsorbent polymer particles that are not pulverized to a desired particle diameter may be included, and if the total content of the additives is too high, high The balance between water retention capacity and absorbency under pressure, which are various physical properties of the absorbent polymer, may deteriorate.

The content of the additive in the super absorbent polymer composition was firstly added to 1 ml of distilled water, followed by sufficient mixing for 1 hour until swelling, then filtering to extract only the solution portion, and then HPLC analysis. It can be measured by analyzing the amount of additives dissolved in the solution portion.

More specifically, the additive is 0.01 parts by weight or more, 0.02 parts by weight or more, 0.05 parts by weight or more, 0.1 parts by weight or more, or 0.5 parts by weight or more, 10 parts by weight or less, 8 parts by weight of 100 parts by weight of the water-soluble ethylenically unsaturated monomer. Or less, 5 parts by weight or less, 3 parts by weight or less, or 2 parts by weight or less may be included.

Meanwhile, at least some of these additives may be present on the surface of the super absorbent polymer particles. Here, "at least some of the additives are present on the surface of the super absorbent polymer particles" means that at least some of the additives are adsorbed or bonded to the surface of the super absorbent polymer particles. Specifically, each of the additives may be physically or chemically adsorbed on the surface of the superabsorbent polymer. More specifically, the hydrophilic functional group of each of the additives may be physically adsorbed to the hydrophilic portion of the surface of the superabsorbent polymer by an intermolecular force such as dipole-dipole interaction. In this way, the hydrophilic part of each of the additives is physically adsorbed on the surface of the superabsorbent polymer particle and covers the surface, and the hydrophobic part of each additive is not adsorbed on the surface of the resin particle, forming a kind of micelle structure. Each additive may be coated on the surface of the resin particle.

Therefore, when at least some of the additives are present on the surface of the super absorbent polymer particles, compared to the case where all of the carboxylic acid-based additives are present in the super absorbent polymer particles, specifically, in the crosslinked polymer, the high During the manufacturing process of the water absorbent polymer composition, aggregation of pulverized particles may be more effectively suppressed.

In addition, since at least some of the additives are present on the surface of the superabsorbent polymer particles, the superabsorbent polymer composition including the additives may have an improved absorption rate compared to a composition not including the additives.

Meanwhile, when the super absorbent polymer composition does not further include a surface crosslinking layer described later, a plurality of super absorbent polymer particles, the additive, and a hydrolyzate of the additive produced by hydrolysis of the additive during the manufacturing process of the super absorbent polymer. Other hydrophilic additives may not be included.

Specifically, the superabsorbent polymer composition of one embodiment may not include a compound having a plurality of hydroxyl group-containing glucose units in a molecule, such as microcrystalline cellulose. For example, when the superabsorbent polymer composition includes microcrystalline cellulose having an average particle diameter of 1 to 10 μm, such as AVICEL ^® PH-101 represented by Formula 3 available from FMC, a plurality of hydroxy Aggregation between the superabsorbent polymer particles may not be suppressed due to the groups, and thus the effects of the above-described additives may not be effectively expressed.

[Formula 3]

In addition, the superabsorbent polymer composition of one embodiment includes polyethylene glycol, polypropylene glycol, poly(ethylene glycol)-poly(propylene glycol) copolymer, polyoxyethylene lauryl ether carboxylic acid, sodium polyoxyethylene lauryl ether carboxyl It may not contain hydrophilic additives such as lauryl, lauryl sulfate, sodium lauryl sulfate, and the like. Such additives have a problem in that they are not sufficiently adsorbed on the surface of the crosslinked polymer, and thus aggregation between the superabsorbent polymer particles is not effectively suppressed. Accordingly, when the superabsorbent polymer composition includes the above hydrophilic additive instead of the carboxylic acid additive, aggregation between particles is not suppressed after pulverization of the crosslinked polymer, so that the superabsorbent polymer composition includes a large amount of fine powder, It exhibits low water holding capacity and low apparent density.

Meanwhile, the superabsorbent polymer composition may further include a surface crosslinking layer formed by additionally crosslinking the crosslinked polymer on at least a portion of the surface of the superabsorbent polymer particle via a surface crosslinking agent. This is to increase the surface cross-linking density of the super-absorbent polymer particles. As described above, when the super-absorbent polymer particles further include a surface cross-linking layer, they have a structure in which the external cross-linking density is higher than the internal ones.

As the surface crosslinking agent, any surface crosslinking agent conventionally used in the preparation of the superabsorbent polymer may be used without 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- 1 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 more than one polyol; 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 cyclic urea compounds; etc. may be included.

Specifically, one or more, two or more, or three or more of the aforementioned surface crosslinking agents may be used as the surface crosslinking agent, and for example, propylene glycol, ethylene carbonate, and propylene carbonate may be used.

In addition, the superabsorbent polymer composition may have a vortex time of less than 35 seconds, less than 34 seconds, less than 23 seconds, less than 30 seconds, or less than 27 seconds at 24.0 ° C according to the vortex method. In addition, the absorption rate is excellent as the value is small, and the lower limit of the absorption rate is theoretically 0 seconds, but for example, it may be 5 seconds or more, 8 seconds or more, 10 seconds or more, or 20 seconds or more. In this case, a method for measuring the absorption rate of the superabsorbent polymer will be described in more detail in Experimental Examples to be described later.

In addition, the superabsorbent polymer composition has a water retention capacity (CRC) of 39 g/g or more, 40 g/g or more, or 42 g/g or more, and 50 g/g or less, 48 g or less, measured according to EDANA method WSP 241.3 /g or less, 45 g/g or less, or 43 g/g or less. The method for measuring the water retention capacity will be described in more detail in experimental examples to be described later.

In addition, the superabsorbent polymer composition has an absorbency under load (AUP) of 24.0 g/g or more, 25.0 g/g or more, or 25.2 g/g or more at 0.7 psi measured according to WSP 242.3 of the EDANA method, or 30 g/g or more. g or less, 28.0 g/g or less, 27.0 g/g or less, 26.0 g/g or less, or 25.5 g/g or less. The method for measuring the absorbency under load will be described in more detail in Experimental Examples to be described later.

(Method for producing superabsorbent polymer composition)

On the other hand, the superabsorbent polymer composition,

crosslinking polymerization of a water-soluble ethylenically unsaturated monomer having an acidic group in the presence of an internal crosslinking agent and a polymerization initiator to form a polymer (step 1);

neutralizing at least some of the acid groups of the polymer (step 2);

Preparing base resin particles by atomizing the polymer in the presence of at least one additive selected from the group consisting of carboxylic acids represented by Formula 1 and salts thereof (step 3); and

It may be prepared by including drying the base resin particles (step 4):

[Formula 1]

In Formula 1,

R is straight-chain or branched-chain alkyl of 6 to 18 carbon atoms or straight-chain or branched-chain alkenyl of 6 to 18 carbon atoms.

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

(Step 1)

In the method for preparing a superabsorbent polymer according to an embodiment, first, a step of forming a water-containing gel polymer is performed by cross-linking and polymerizing a water-soluble ethylenically unsaturated monomer having an acidic group in the presence of an internal cross-linking agent and a polymerization initiator.

The step may include preparing a monomer composition by mixing the water-soluble ethylenically unsaturated monomer, an internal crosslinking agent, and a polymerization initiator, and forming a polymer by thermally or photopolymerizing the monomer composition. At this time, the description of the water-soluble ethylenically unsaturated monomer and the internal crosslinking agent refers to the above.

Here, the water-soluble ethylenically unsaturated monomer has an acidic group. As described above, in the preparation of the conventional superabsorbent polymer, a water-containing gel polymer is formed by cross-linking polymerization of a monomer in which at least some of the acidic groups are neutralized by a neutralizing agent. Specifically, in the step of mixing the water-soluble ethylenically unsaturated monomer having an acidic group, an internal crosslinking agent, a polymerization initiator, and a neutralizing agent, at least some of the acidic groups of the water-soluble ethylenically unsaturated monomer were neutralized.

However, according to one embodiment of the present invention, polymerization is first performed in a state where the acidic groups of the water-soluble ethylenically unsaturated monomers are not neutralized to form a polymer.

A water-soluble ethylenically unsaturated monomer (eg, acrylic acid) in which the acidic group is not neutralized is in a liquid state at room temperature and has high miscibility with a solvent (water), so it exists as a mixed solution in the monomer composition. However, the water-soluble ethylenically unsaturated monomer having neutralized acid groups is in a solid state at room temperature and has different solubility depending on the temperature of the solvent (water), and the lower the temperature, the lower the solubility.

As such, the water-soluble ethylenically unsaturated monomers in which the acidic groups are not neutralized have higher solubility or miscibility in the solvent (water) than the monomers in which the acidic groups are neutralized, so they do not precipitate even at low temperatures, and thus are advantageous for long-term polymerization at low temperatures. . Accordingly, it is possible to stably form a polymer having a higher molecular weight and a uniform molecular weight distribution by performing polymerization for a long time using the water-soluble ethylenically unsaturated monomer in which the acidic group is not neutralized.

In addition, it is possible to form a longer chain polymer, thereby achieving an effect of reducing the content of water-soluble components present in a non-crosslinked state due to incomplete polymerization or crosslinking.

In addition, polymerization is first performed in a state in which the acidic group of the monomer is not neutralized to form a polymer, and after neutralization, atomization is performed in the presence of the carboxylic acid additive, or when the acidic group present in the polymer is neutralized simultaneously with atomization, the carboxyl group An acid additive may be present in a large amount on the surface of the polymer to sufficiently play a role of lowering the adhesiveness of the polymer.

The type of the water-soluble ethylenically unsaturated monomer in the monomer composition is the same as that described in the superabsorbent polymer composition. In addition, the concentration of the water-soluble ethylenically unsaturated monomer may be appropriately adjusted in consideration of polymerization time and reaction conditions, and may be about 20 to about 60% by weight, or about 20 to about 40% by weight.

The type of the internal crosslinking agent in the monomer composition is applied in the same manner as described in the above-described superabsorbent polymer composition. In addition, the amount of the internal crosslinking agent may be 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, or 0.1 parts by weight or more, based on 100 parts by weight of the water-soluble ethylenically unsaturated monomer, and 5 parts by weight or less, 3 parts by weight or less, 2 parts by weight or less, 1 It may be used in parts by weight or less, or 0.7 parts by weight or less. If the content of the upper internal cross-linking agent is too low, cross-linking does not occur sufficiently, making it difficult to realize an appropriate level of strength. If the content of the upper internal cross-linking agent is too high, the internal cross-linking density increases, making it difficult to realize the desired water retention capacity.

In addition, the polymerization initiator may be appropriately selected according to the polymerization method, a thermal polymerization initiator is used when a thermal polymerization method is used, a photopolymerization initiator is used when a photopolymerization method is used, and a hybrid polymerization method (thermal and photopolymerization initiators) is used. In the case of using both), both a thermal polymerization initiator and a photopolymerization initiator may be used. However, even with the photopolymerization method, since a certain amount of heat is generated by light irradiation such as ultraviolet irradiation, and a certain amount of heat is generated as the polymerization reaction progresses, which is an exothermic reaction, a thermal polymerization initiator may be additionally used.

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

Examples of the photopolymerization initiator include benzoin ether, dialkyl acetophenone, hydroxyl alkylketone, phenyl glyoxylate, and benzyl dimethyl ketal. Ketal), 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. More various photoinitiators are well described in "UV Coatings: Basics, Recent Developments and New Application (Elsevier 2007)" p115, a book by Reinhold Schwalm, and are not limited to the above examples.

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

The polymerization initiator may be 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 a large amount of residual monomer may be extracted into the final product, which is not preferable. Conversely, when the concentration of the polymerization initiator is higher than the above range, the polymer chain constituting the network is shortened, which is not preferable because the physical properties of the resin may be deteriorated, such as an increase in the content of water-soluble components and a decrease in absorbency under pressure.

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 including the monomer may be, for example, in a solution state dissolved in a solvent such as water, and the solid content, that is, the concentration of the monomer, the internal crosslinking agent, and the polymerization initiator in the monomer composition in the solution state is determined by polymerization. It may be appropriately adjusted in consideration of time and reaction conditions. For example, the solids content in the monomer composition may be 10 to 80% by weight, or 15 to 60% by weight, or 30 to 50% by weight.

When the monomer composition has a solid content in the above range, the gel effect phenomenon that occurs in the polymerization reaction of a high-concentration aqueous solution is used to eliminate the need to remove unreacted monomers after polymerization, while increasing the pulverization efficiency when pulverizing the polymer, which will be described later. It can be advantageous to adjust.

The solvent that can be used at this time can be used without limitation in composition as long as it can dissolve the above-mentioned components. 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, methylcellosolveacetate, and N,N-dimethylacetamide may be used in combination.

According to one embodiment of the present invention, the step of forming a polymer by performing polymerization on the monomer composition may be performed in a batch type reactor.

In the conventional method for producing a superabsorbent polymer composition, the polymerization method is largely divided into thermal polymerization and photopolymerization according to the polymerization energy source, and in the case of conventional thermal polymerization, it may be performed in a reactor having an agitation shaft such as a kneader, and photopolymerization may be performed. When proceeding, it may proceed in a reactor with a movable conveyor belt or in a flat-bottomed vessel.

On the other hand, in the polymerization method as described above, a polymer having a wide molecular weight distribution without a high molecular weight is formed according to a relatively short polymerization reaction time (eg, 1 hour or less).

On the other hand, when photopolymerization is performed in a reactor equipped with a movable conveyor belt or in a container with a flat bottom, a water-containing gel polymer is usually obtained in the form of a sheet having the width of the belt, and the thickness of the polymer sheet is It depends on the concentration of the monomer composition and the injection rate or amount of injection, but is usually obtained in a thickness of about 0.5 to about 5 cm.

However, when the monomer composition is supplied to such an extent that the thickness of the polymer on the sheet is too thin, production efficiency is low, which is undesirable. When the thickness of the polymer on the sheet is increased for productivity, the polymerization reaction does not occur evenly over the entire thickness, resulting in high-quality products. Polymer formation becomes difficult.

In addition, in the polymerization in the reactor having the stirring shaft of the reactor equipped with the conveyor belt, a new monomer composition is supplied to the reactor while the polymerization product is moved, so that the polymerization is carried out in a continuous manner, so that polymers having different polymerization rates are mixed. Accordingly, the monomer composition It is difficult to achieve uniform polymerization throughout, and overall physical properties may be deteriorated.

However, according to one embodiment of the present invention, as the polymerization proceeds in a stationary manner in a batch reactor, there is little risk of mixing polymers having different polymerization rates, and accordingly, polymers having uniform quality can be obtained.

In addition, the polymerization step is carried out in a batch reactor having a predetermined volume, and the polymerization reaction is carried out for a longer period of time, for example, 6 hours or more, than in the case of continuous polymerization in a reactor equipped with a conveyor belt. In spite of the long polymerization reaction time described above, since polymerization is performed on unneutralized water-soluble ethylenically unsaturated monomers, monomers are not easily precipitated even when polymerization is performed for a long time, and therefore, it is advantageous to perform polymerization for a long time.

Meanwhile, as the polymerization in the batch reactor of the present invention uses a thermal polymerization method, the polymerization initiator may be a thermal polymerization initiator among the above-mentioned initiators.

Meanwhile, in one embodiment of the present invention, polymerization may be initiated by adding the initiator and a reducing agent forming a redox couple together.

Specifically, when the initiator and the reducing agent are added to the polymer solution, they react with each other to form radicals.

The formed radical reacts with the monomer, and since the oxidation-reduction reaction between the initiator and the reducing agent is highly reactive, polymerization is initiated even when only a small amount of the initiator and the reducing agent are added, and there is no need to increase the process temperature, enabling low-temperature polymerization. , it is possible to minimize the change in physical properties of the polymer solution.

The polymerization reaction using the oxidation-reduction reaction may occur smoothly even at a temperature near or below room temperature (25° C.). For example, the polymerization reaction may be carried out at a temperature of 5°C or more and 25°C or less, or 5°C or more and 20°C or less.

In one embodiment of the present invention, when using a persulfate-based initiator as the initiator, the reducing agent is sodium metabisulfite (Na ₂ S ₂ O ₅ ); tetramethyl ethylenediamine (TMEDA); a mixture of iron(II) sulfate and EDTA (FeSO ₄ /EDTA); sodium formaldehyde sulfoxylate; And one or more selected from the group consisting of disodium 2-hydroxy-2-sulfinoacetate (Disodium 2-hydroxy-2-sulfinoacteate) may be used.

In one example, using potassium persulfate as an initiator and disodium 2-hydroxy-2-sulfinoacetate as a reducing agent; Ammonium persulfate is used as an initiator and tetramethylethylenediamine is used as a reducing agent; Sodium persulfate can be used as an initiator and sodium formaldehyde sulfoxylate as a reducing agent.

In another embodiment of the present invention, when using a hydrogen peroxide-based initiator as the initiator, the reducing agent is ascorbic acid; Sucrose; sodium sulfite (Na ₂ SO ₃ ) sodium metabisulfite (Na ₂ S ₂ O ₅ ); tetramethyl ethylenediamine (TMEDA); a mixture of iron(II) sulfate and EDTA (FeSO ₄ /EDTA); sodium formaldehyde sulfoxylate; Disodium 2-hydroxy-2-sulfinoacteate; And it may be at least one selected from the group consisting of disodium 2-hydroxy-2-sulfoacetate.

As the polymer obtained in this way is polymerized using an unneutralized ethylenically unsaturated monomer, a polymer having a high molecular weight and a uniform molecular weight distribution can be formed as described above, and the content of water-soluble components can be reduced. there is.

The polymer obtained in this way is in the form of a water-containing gel polymer and may have a moisture content of 30 to 80% by weight. For example, the water content of the polymer may be 30 wt% or more, or 45 wt% or more, or 50 wt% or more, and 80 wt% or less, or 70 wt% or less, or 60 wt% or less.

If the water content of the polymer is too low, it may not be effectively pulverized because it is difficult to secure an appropriate surface area in the subsequent grinding step, and if the water content of the polymer is too high, the pressure applied in the subsequent grinding step may increase, making it difficult to pulverize to the desired particle size. .

On the other hand, "moisture content" throughout the present specification refers to a value obtained by subtracting the weight of the polymer in a dry state from the weight of the polymer as the content of moisture with respect to the total weight of the polymer. Specifically, it is defined as a value calculated by measuring the weight loss due to evaporation of water in the polymer in the process of raising the temperature of the polymer in the crumb state through infrared heating and drying. At this time, the drying condition is a method of raising the temperature from room temperature to about 180 ° C and then maintaining it at 180 ° C. The total drying time is set to 40 minutes including 5 minutes of the temperature raising step, and the moisture content is measured.

(Step 2 and Step 3)

Next, neutralizing at least some of the acid groups of the polymer (step 2); and preparing base resin particles by atomizing the polymer in the presence of one or more additives selected from the group consisting of carboxylic acids represented by Formula 1 and salts thereof (step 3).

First, as the neutralizing agent used in step 2, a basic material such as sodium hydroxide, potassium hydroxide, or ammonium hydroxide capable of neutralizing an acidic group may be used.

In addition, the degree of neutralization, which refers to the degree of neutralization by the neutralizing agent among the acid groups included in the polymer, is 50 to 90 mol%, or 60 to 85 mol%, or 65 to 85 mol%, or 65 to 75 mol%. can be 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 absorption capacity of the superabsorbent polymer may decrease, and the concentration of carboxyl groups on the surface of the particles is too low, making it difficult to properly perform surface crosslinking in the subsequent process. Absorption under pressure or liquid permeability may decrease. Conversely, if the degree of neutralization is too low, not only the absorbency of the polymer is greatly reduced, but also exhibits properties such as elastic rubber that are difficult to handle.

Next, in the presence of at least one additive selected from the group consisting of carboxylic acids represented by Formula 1 and salts thereof, the polymer is atomized to prepare base resin particles (step 3); is performed.

Here, steps 2 and 3 may be performed sequentially, simultaneously, or alternately.

The step is to atomize the polymer in the presence of the carboxylic acid additive, and the polymer is not chopped to a millimeter size, but chopped and agglomerated at the same time. This is a step of preparing secondary agglomerated particles in the form of agglomerated particles. The surface area of the base resin particles, which are secondary agglomerated particles, prepared in this step is greatly increased, so that the absorption rate can be remarkably improved.

After mixing the polymer and the carboxylic acid additive, the polymer is atomized in the presence of the carboxylic acid additive, and the superabsorbent polymer particles and the surfactant are mixed. particles can be produced.

The description of one or more additives selected from the group consisting of carboxylic acid represented by Chemical Formula 1 and salts thereof may be applied in the same manner as described in the above-described superabsorbent polymer composition.

Here, the "base resin particles" are particles having a moisture content (moisture content) of about 30% by weight or more, and since the polymer is chopped and aggregated into particles without a drying process, the moisture content of 30 to 80% by weight, preferably may have a moisture content of 70 to 80% by weight.

Meanwhile, the carboxylic acid additive may be used in an amount of 0.01 to 10 parts by weight based on 100 parts by weight of the water-soluble ethylenically unsaturated monomer used for crosslinking polymerization to prepare the polymer. When the carboxylic acid additive is used in an excessive amount, it is not evenly adsorbed on the surface of the polymer, and re-agglomeration of particles after grinding may occur. this may deteriorate. For example, the carboxylic acid additive is 0.01 parts by weight or more, 0.015 parts by weight or more, or 0.1 parts by weight or more, and 5 parts by weight or less, 3 parts by weight or less, 2 parts by weight or less, based on 100 parts by weight of the water-soluble ethylenically unsaturated monomer or less, or less than 1 part by weight.

Preferably, the carboxylic acid additive may be prepared through a ring-opening reaction of a compound represented by Formula A below:

[Formula A]

In Formula A,

R is straight-chain or branched-chain alkyl of 6 to 18 carbon atoms or straight-chain or branched-chain alkenyl of 6 to 18 carbon atoms.

Preferably, R may be a linear alkyl or linear alkenyl having 6 to 18 carbon atoms. The case where R is a straight-chain alkyl or alkenyl is more advantageous in terms of suppressing aggregation of branched-chain particles and improving dispersibility. Specifically, in Formula 1, when R is a linear alkyl having 6 to 18 carbon atoms, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decanyl, n-undecanyl, n-dodecyl. canyl, n-tridecanyl, n-tetradecanyl, n-pentadecanyl, n-hexadecanyl, n-heptadecanyl, or n-octadecanyl, or linear alkenyl of 6 to 18 carbon atoms. In the case of 2-hexenyl, 2-heptenyl, 2-octenyl, 2-nonenyl, n-dekenyl, 2-undecenyl, 2-dodekenyl, 2-tridekenyl, 2-tetradekenyl, 2-pentadekenyl, 2-hexadecenyl, 2-heptadekenyl, or n-octadekenyl.

Conditions for the ring-opening reaction are not particularly limited, and may be performed by heating at about 70° C. to 120° C. for 1 hour to 10 hours using a solvent, but is not limited thereto.

The carboxylic acid-based additive represented by Chemical Formula 1 of the present application obtained through the ring-opening reaction may preferably be in a dispersed state in a solvent, and thus may be mixed in a dispersed state when mixed with a polymer.

For example, the carboxylic acid additive may be mixed in a dispersed state in a solvent. At this time, all kinds of solvents can be used without limitation, including inorganic solvents and organic solvents, but water is most appropriate considering the ease of ring-opening reaction in the obtaining process, the ease of drying process, and the cost of the solvent recovery system.

Meanwhile, according to one embodiment of the present invention, steps 2 and 3 may be performed sequentially, simultaneously, or alternately.

That is, after adding a neutralizing agent to the polymer to neutralize the acidic group first, adding the additive of Formula 1 to the neutralized polymer to micronize the polymer in which the additive is mixed, or simultaneously adding the neutralizer and the additive of Formula 1 to the polymer to Neutralization and atomization can also be performed. Alternatively, the additive of Chemical Formula 1 may be added first and the neutralizing agent may be added later. Alternatively, the neutralizing agent and the additive of Chemical Formula 1 may be alternately introduced. Alternatively, the additive of Chemical Formula 1 may be added first to atomize the mixture, then a neutralizer may be added to neutralize the mixture, and then the additive of Chemical Formula 1 may be additionally added to the neutralized water-containing gel polymer to further perform the atomization process.

On the other hand, it may be desirable to set a certain time difference between the injection of the neutralizer and the atomization process for uniform neutralization of the entire polymer.

At least some or a significant amount of the carboxylic acid additive may be present on the surface of the base resin particle.

Here, the fact that the carboxylic acid additive is present on the surface of the base resin particle means that at least a part or a significant amount of the carboxylic acid additive is adsorbed or bonded to the surface of the base resin particle. Specifically, the carboxylic acid additive may be physically or chemically adsorbed on the surface of the base resin particle. More specifically, the hydrophilic functional group of the carboxylic acid additive may be physically adsorbed to the hydrophilic portion of the surface of the base resin particle by an intermolecular force such as dipole-dipole interaction. In this way, the hydrophilic part of the carboxylic acid additive is physically adsorbed on the surface of the base resin particle and covers the surface, and the hydrophobic part of the carboxylic acid additive is not adsorbed on the surface of the base resin particle, so that the base resin particle is a kind of A carboxylic acid additive may be coated in the form of a micelle structure. This is because the carboxylic acid additive is not added during the polymerization process of the water-soluble ethylenically unsaturated monomer, but is added during the atomization step after polymer formation, and the carboxylic acid additive is added during the polymerization process to form the carboxylic acid inside the polymer. Compared to the case where an additive is present, it can faithfully perform its role as a surfactant, and pulverization and aggregation occur simultaneously to obtain particles with a large surface area in the form of agglomerated fine particles.

According to one embodiment, the step (step 3) of preparing the base resin particles may be performed using an atomization device.

The atomization device may include a body portion including a transport space in which a mixture of a polymer and an additive is transported; a screw member rotatably installed inside the transfer space to move the mixture; a driving motor providing rotational driving force to the screw member; and a cutter member including a perforated plate installed in the body and having a plurality of holes, and pulverizing the mixture while discharging it to the outside of the body.

According to one embodiment, steps 2 and 3 are performed sequentially, simultaneously or alternately, which may be performed using an atomization device.

In this case, the atomization device further includes a neutralizer injection nozzle installed inside the body, and the neutralizer is injected through the neutralizer injection nozzle, so that steps 2 and 3 are performed sequentially, simultaneously, or alternately. be able to

Specifically, the neutralizer is injected into the body through the neutralizer injection nozzle to neutralize at least some of the acidic groups of polymers having acidic groups in the mixture. Specifically, in the atomization device, a neutralizer is injected into the body through the neutralizer injection nozzle to neutralize at least some of the acid groups of polymers having acid groups in the mixture, and the mixture is discharged to the outside of the body through a perforated plate. being pulverized (atomized).

Preferably, the neutralizing agent pulverized by the neutralizing agent injection nozzle may be sprayed adjacent to the perforated plate, and in this case, when the neutralization process is performed and the mixture is discharged through the hole of the perforated plate, the slip agent in the mixture It is desirable because it can reduce the load of the hall by performing a role.

Preferably, the cutter member of the atomization device includes a perforated plate and a cutting knife disposed adjacent to the perforated plate and disposed on the outlet side of the body, and after the mixture passes through the perforated plate, the mixture is more effectively pulverized by the cutting knife for atomization. do.

In the atomization device, the cutter member may include a plurality of perforated plates and a plurality of cutting knives. The arrangement order of the plurality of perforated plates and the plurality of cutting knives is not particularly limited, and each may be sequentially disposed, may be disposed crossing each other, a plurality of perforated plates may be disposed in succession, or a plurality of cutting knives may be disposed in succession. can

By including a plurality of perforated plates and cutting knives as described above, multiple times of atomization can be performed in a single atomization device. Meanwhile, a plurality of neutralizer spray nozzles may be disposed adjacent to at least one of the plurality of perforated plates and cutting knives, and the neutralizer spray nozzles are preferably disposed adjacent to the perforated plate in terms of improving slip properties.

In the atomization device, the hole size formed in the perforated plate may be 0.1 mm to 30 mm. Preferably, it may be 0.5 mm to 25 mm, 1 mm to 20 mm, or 1 mm to 10 mm. By using a perforated plate having the above-mentioned hole size, base resin particles having a desired particle size may be prepared. As described above, when the cutter member includes a plurality of perforated plates, the size of holes formed in each of the perforated plates may satisfy the above range, and they may be the same as or different from each other.

According to one embodiment of the invention, step 3 may be performed a plurality of times, using a plurality of atomization devices, or using a single atomization device including a plurality of perforated plates and/or a plurality of cutting knives. Alternatively, some of the plurality of atomization devices may include a plurality of perforated plates and/or a plurality of cutting knives. The atomization step may be preferably performed 1 to 6 times or 1 to 4 times. When step 3 is performed a plurality of times, the additive may be additionally introduced a plurality of times.

The step (step 3) of preparing base resin particles by atomizing the polymer may be atomized such that the average particle diameter of the base resin particles is 50 μm to 600 μm, preferably, 100 μm to 500 μm, 150 μm to 450 μm It can be atomized so that it may become ㎛, or 200 ㎛ to 400 ㎛. By satisfying the above particle size range, the amount of fine powder generated during the process can be significantly reduced as the polymer is prepared as secondary particles in which the primary particles are aggregated and then the pulverization and drying process proceeds under milder conditions.

In the present invention, the average particle diameter “Dn” means the particle size or particle diameter at the n% point of the cumulative distribution of the number of particles according to the particle size. That is, D50 represents the particle size at the 50% point of the cumulative distribution of the number of particles according to the particle size, D90 represents the particle size at the 90% point of the cumulative distribution of the number of particles according to the particle size, and D10 represents the particle size at the point of the cumulative distribution of the number of particles according to the particle size. The particle size at the 10% point of the particle number cumulative distribution is shown. The Dn can be measured using a laser diffraction method or the like. Specifically, after dispersing the powder to be measured in a dispersion medium, it is introduced into a commercially available laser diffraction particle size measuring device (e.g. Microtrac S3500) to measure the difference in diffraction pattern according to the particle size when the particles pass through the laser beam, Calculate the size distribution. D10, D50 and D90 can be measured by calculating the particle size at the point where it becomes 10%, 50% and 90% of the particle number cumulative distribution according to the particle size in the measuring device.

(Step 4)

Next, a step (step 4) of drying the base resin particles is included. Through this, a super absorbent polymer composition including the super absorbent polymer particles and the carboxylic acid additive may be prepared.

The drying may be performed so that the moisture content of each of the plurality of super absorbent polymer particles included in the prepared super absorbent polymer composition is about 10% by weight or less, specifically, about 0.1 to about 10% by weight.

At this time, drying of the pulverized material may be performed in a moving type. This moving type drying is distinguished from fixed-bed type drying by the presence/absence of material flow during drying.

In a conventional method for preparing super absorbent polymer, the drying step is generally performed until the moisture content of the super absorbent polymer particles is less than 10% by weight. However, in the present invention, aggregation is controlled by performing the atomization step in the presence of a carboxylic acid additive, so that the moisture content of the superabsorbent polymer particles to be dried is 10% to 20% by weight, preferably 10% to 25% by weight. It is performed by drying to become. Accordingly, there is an advantage in that generation of fine powder can be fundamentally prevented by exhibiting a high moisture content. In addition, it is preferable because it can improve the absorption rate of the final superabsorbent polymer composition.

To this end, the drying step is performed in a method of drying in a moving type at a relatively low temperature. This moving type drying is distinguished from fixed-bed type drying by the presence/absence of material flow during drying, and the phenomenon of aggregation between the chopped water-containing superabsorbent polymer particles in the pulverized material to be dried. It is preferable because it can prevent and complete drying within a short time.

To this end, the drying step is performed in a method of drying in a moving type at a relatively low temperature. This moving type drying is distinguished from fixed-bed type drying by the presence/absence of material flow during drying, and prevents aggregation between the chopped base resin particles in the pulverized material to be dried. And, it is preferable because it can complete drying within a short time.

Specifically, the moving type drying refers to a method of drying the drying body while mechanically stirring it. At this time, the direction in which the hot air passes through the material may be the same as or different from the circulation direction of the material. Alternatively, the material may be circulated inside the dryer and the material may be dried by passing a heat exchanger fluid (heat oil) through a separate pipe outside the dryer. On the other hand, fixed-bed type drying refers to a method in which hot air passes through the material from the bottom to the top in a state in which the material to be dried is suspended on the floor such as a perforated iron plate through which air can flow.

In the step of drying the base resin particles (step 4), a generally used liquid dryer may be used without particular limitation, for example, a horizontal-type mixer, a rotary kiln, a paddle dryer (Paddle Dryer) or steam tube dryer (Steam tube dryer) can be carried out using a fluid dryer.

The drying step (step 4) may be performed at a relatively low temperature of 150 ° C or less, and preferably may be performed at 100 ° C to 150 ° C, 100 ° C to 130 ° C, 105 ° C to 115 ° C, Even if it is performed at a low temperature as described above, it is possible to prepare superabsorbent polymer particles having a desired particle size and physical properties without desired aggregation.

On the other hand, the drying temperature may be an internal driving temperature at which dry matter of the fluid type drying device is input, which may be adjusted by passing a heat exchanger fluid (heat oil) through a separate pipe pipe outside the dryer, but is limited thereto. it is not going to be

The drying step (step 4) may be performed for 30 minutes to 80 minutes, 30 minutes to 60 minutes, or 40 minutes to 50 minutes, and between the chopped polymer resin particles in the pulverized material to be dried. Even if the drying step is performed for a short time at a relatively low temperature due to low aggregation, it is possible to prepare superabsorbent polymer particles having a desired particle size and physical properties.

(additional step)

Thereafter, the method for preparing a super absorbent polymer composition according to an embodiment of the present invention may further include pulverizing and classifying the super absorbent polymer particles, if necessary.

Specifically, the pulverizing step may be performed to pulverize the dry super absorbent polymer particles to have a normal particle size, that is, a particle size of 150 μm to 850 μm.

The grinder used for this purpose is specifically a vertical pulverizer, a turbo cutter, a turbo grinder, a rotary cutter mill, a cutter mill, It may be a disc mill, a shred crusher, a crusher, a chopper, or a disc cutter, but is not limited to the above examples.

Alternatively, as a grinder, a pin mill, hammer mill, screw mill, roll mill, disc mill, or jog mill may be used. , It is not limited to the above example.

On the other hand, in the manufacturing method of the present invention, since superabsorbent polymer particles having a smaller particle size distribution than in the conventional chopping step can be implemented in the atomization step, even when grinding is performed under mild conditions with less grinding force, the content of normal particle size is maintained. A very high water-absorbent polymer can be formed, and the fine powder production rate can be greatly reduced.

The super absorbent polymer particles prepared as described above contain 89% by weight or more, 90% by weight or more, 92% by weight or more, or 93% by weight of superabsorbent polymer particles having a particle size of 150 μm to 850 μm, that is, normal particles, relative to the total weight. or more, 94% by weight or more, or 95% by weight or more. The particle diameter of these resin particles may be measured according to the European Disposables and Nonwovens Association (EDANA) standard EDANA WSP 220.3 method.

In addition, the superabsorbent polymer particles may include less than about 10% by weight, specifically less than about 5% by weight, and more specifically less than about 3% of fine powder having a particle size of less than 150 μm relative to the total weight. This is in contrast to having about 10% by weight to about 20% by weight of the fine powder when the superabsorbent polymer is prepared according to a conventional manufacturing method.

Next, the method for preparing super absorbent polymer according to an embodiment of the present invention may include preparing super absorbent polymer particles by thermally crosslinking the surface of the base resin powder in the presence of surface crosslinking.

The surface crosslinking step is to induce a crosslinking reaction on the surface of the base resin powder in the presence of a surface crosslinking agent, and the unsaturated bonds of the water-soluble ethylenically unsaturated monomers remaining on the surface without crosslinking are crosslinked by the surface crosslinking agent, A superabsorbent polymer with high crosslinking density is formed.

Specifically, a surface crosslinking layer may be formed by a heat treatment process due to the presence of a surface crosslinking agent, and the heat treatment process increases the surface crosslinking density, that is, the external crosslinking density, while the internal crosslinking density does not change, resulting in a surface crosslinking layer. The formed superabsorbent polymer has a structure in which the crosslinking density is higher on the outside than on the inside.

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 superabsorbent polymer particle is sufficiently crosslinked to increase absorbency under pressure.

By satisfying these surface crosslinking process conditions (in particular, reaction conditions at elevated temperature and maximum reaction temperature), a superabsorbent polymer that adequately satisfies physical properties such as a better water absorption rate can be produced.

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

Meanwhile, as the surface cross-linking agent included in the surface cross-linking agent composition, any surface cross-linking agent conventionally used in the preparation of the superabsorbent polymer may be used without 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- 1 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 more than one polyol; At least one carbonate-based compound selected from the group consisting of ethylene carbonate and propylene carbonate; epoxy compounds such as ethylene glycol diglycidyl ether; oxazoline compounds such as oxazolidinone; polyamine compounds; oxazoline compounds; mono-, di- or polyoxazolidinone compounds; or cyclic urea compounds; etc. may be included. Preferably, the same internal crosslinking agent as described above may be used, and for example, a diglycidyl ether-based compound of alkylene glycol such as ethylene glycol diglycidyl ether may be used.

In the surface cross-linking step, a surface cross-linking agent composition containing an alcohol-based solvent and water may be used in addition to the surface cross-linking agent.

The surface crosslinking agent may be used in an amount of 0.001 to 2 parts by weight based on 100 parts by weight of the superabsorbent polymer particles. Preferably, it is 0.005 parts by weight or more, 0.01 parts by weight or more, or 0.02 parts by weight or more, and may be used in an amount of 0.5 parts by weight or less and 0.3 parts by weight or less. By adjusting the content range of the surface crosslinking agent within the above-described range, a superabsorbent polymer exhibiting various physical properties such as excellent absorption performance and liquid permeability can be prepared.

On the other hand, the surface crosslinking agent is added to the superabsorbent polymer particles in the form of a surface crosslinking agent composition containing the surface crosslinking agent composition, but there is no particular limitation on the composition of the method for adding the surface crosslinking agent composition. For example, the surface cross-linking agent composition and super-absorbent polymer particles are mixed in a reaction tank, or the surface cross-linking agent composition is sprayed on the super-absorbent polymer particles, and the super-absorbent polymer particles and the surface cross-linking agent composition are continuously mixed in a continuously operated mixer. A method of supplying and mixing can be used.

In addition, the surface crosslinking agent composition may further include water and/or a hydrophilic organic solvent as a medium. As a result, there is an advantage in that the surface crosslinking agent and the like can be evenly dispersed on the base resin powder. At this time, the content of water and the hydrophilic organic solvent is 100 parts by weight of superabsorbent polymer particles for the purpose of inducing uniform dissolution/dispersion of the surface crosslinking agent, preventing aggregation of the base resin powder, and at the same time optimizing the surface penetration depth of the surface crosslinking agent It can be applied by adjusting the addition ratio for

Meanwhile, in the method for preparing the superabsorbent polymer according to an embodiment of the present invention, aluminum salts such as aluminum sulfate salts and other various polyvalent metal salts may be further used to further improve liquid permeability and the like during surface crosslinking. Such a polyvalent metal salt may be included on the surface crosslinking layer of the finally prepared superabsorbent polymer.

According to one embodiment of the present invention, after the step of forming a surface cross-linked layer on at least a portion of the surface of the super-absorbent polymer particle, a cooling step of cooling the super-absorbent polymer particle on which the surface cross-linked layer is formed, the surface cross-linked layer It may be performed by further including at least one step of a hydrolysis step of injecting water into the formed superabsorbent polymer particles and a post-treatment step of injecting an additive into the superabsorbent polymer particles on which the surface crosslinking layer is formed. At this time, the cooling step, the adding step, and the post-treatment step may be performed sequentially or simultaneously.

Additives introduced in the post-treatment step may include a liquid permeability improver, an anti-caking agent, a fluidity improver, and an antioxidant, but the present invention is not limited thereto.

By selectively performing the cooling step, the hydrolysis step, and the post-treatment step, the moisture content of the final super absorbent polymer can be improved and a higher quality super absorbent polymer product can be manufactured.

According to another embodiment of the present invention, a superabsorbent polymer composition prepared by the above manufacturing method is provided.

The super absorbent polymer composition prepared by the above manufacturing method has a high water content without a separate additional hydrolysis process or an additive input process, so the fine powder content is low, and water retention capacity (CRC), which is overall absorption property, compared to the super absorbent polymer prepared by the conventional method A superabsorbent polymer with excellent absorbency under load (AUP) at the same level or higher and at the same time with a lower water-soluble component (EC) content can provide a superabsorbent polymer with excellent absorption rate and the like.

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

Example - Preparation of Super Absorbent Polymer Composition

Example 1

(Step 1) In a 5L glass container equipped with a stirrer and a thermometer, 1,000 g of acrylic acid, 3.5 g of pentaerythritol triallyl ether as an internal crosslinking agent, and 2,260 g of water were mixed and stirred while maintaining at 5°C. 1,000 cc/min of nitrogen was introduced into the glass container containing the mixture for 1 hour to replace the mixture with nitrogen conditions. Next, 13 g of a 0.3% aqueous hydrogen peroxide solution, 15 g of a 1% aqueous solution of ascorbic acid, and 30 g of a 2% aqueous solution of 2,2'-azobis-(2-amidinopropane)dihydrochloric acid were added as polymerization initiators, and at the same time 0.01% as a reducing agent. Polymerization was initiated by the addition of 15 g of an aqueous solution of iron sulfate. After the temperature of the mixture reached 85°C, a polymer was obtained by polymerization at 90±2°C for about 3 hours.

(Step 3-1)

A compound of Formula A'-1 (TCl reagent) was mixed with water in a molar ratio of 1:4, and then a ring-opening reaction was performed under stirring at 85°C for 4 hours to obtain compound A-1 of Table 1. 2 shows H NMR data of the ring-opening reaction.

[Formula A'-1]

(Step 2 and Step 3)

As an additive of Formula 1, 1.19 g of Compound A-1 of Table 1 (4,000 ppmw compared to the solid superabsorbent polymer) was dispersed in 52.27 g of water (preparation of 2 wt% aqueous dispersion), and then 1,000 g of the polymer obtained in Step 1 mixed with.

The mixture was passed once through a first atomization device equipped with a perforated plate having a plurality of holes having a hole size of 6 mm to perform a first atomization process.

Next, the 2nd, 3rd, and 4th micronization processes were performed by repeating the injection into a second atomization device equipped with a perforated plate having a plurality of holes having a hole size of 4 mm three times in total.

In the second pulverization process, 400 g of 32% NaOH aqueous solution was injected through a neutralizer nozzle disposed adjacent to the perforated plate, and a pulverization and neutralization process were performed.

In the tertiary micronization process, 37.5 g of a 15% Na ₂ SO ₄ aqueous solution was introduced through a neutralizer nozzle disposed adjacent to the perforated plate, and a neutralization process was performed along with micronization.

Finally, in the fourth micronization process, a micronization process was performed without adding a neutralizer or surfactant to obtain base resin particles.

The degree of neutralization of the base resin particles was 70 mol%.

(Step 4) After that, 1,000 g of the base resin particles were put into a rotary mixer fluid dryer rotating at 100 rpm. Drying was performed for 60 minutes while maintaining the internal temperature of the dryer at 105° C. to obtain superabsorbent polymer particles. The water content of the superabsorbent polymer particles was 13wt%.

Example 2

A superabsorbent polymer composition was prepared in the same manner as in Example 1, except that Compound A-2 in Table 2 (available from GATTEFOSSE) was used instead of Compound A-1 as the additive of Formula 1 in Example 1.

After drying in step 4, the moisture content of the final superabsorbent polymer particles was 13%.

Example 3

0.595 g of compound A-1 used in Example 1 and 0.595 g of compound A-2 used in Example 2 were mixed as additives of Formula 1, and the same method as in Example 1 was used, except that a total of 1.19 g of additives was used. A superabsorbent polymer composition was prepared using

After drying in step 4, the moisture content of the final superabsorbent polymer particles was 13%.

Example 4 - Case with different content of additives

A superabsorbent polymer composition was prepared in the same manner as in Example 1, except that the content of compound A-1 was increased to 2.38 g (as the additive of Formula 1) in Example 1.

After drying in step 4, the moisture content of the final superabsorbent polymer particles was 12%.

Comparative Example 1

A superabsorbent polymer composition was prepared in the same manner as in Example 1, except that the additive of Formula 1 was not used.

Comparative Examples 2 to 6

A superabsorbent polymer composition was prepared in the same manner as in Example 1, except that the additives of Formula 1 were used in the same amounts as those listed in Table 1 below.

Comparative Example 7

In a 3L glass container equipped with a stirrer and a thermometer, 100 g (1.388 mol) of acrylic acid, 0.16 g of internal crosslinking agent polyethylene glycol diacrylate (Mn = 508), photopolymerization initiator diphenyl (2, 4,6-trimethylbenzoyl) phosphine oxide 0.008 g of the thermal polymerization initiator, 0.12 g of sodium persulfate, and 123.5 g of a 32% caustic soda (NaOH) solution were mixed at room temperature to prepare a monomer composition (degree of neutralization of acrylic acid: 70 mol%, solid content: 45% by weight). .

Thereafter, the monomer composition was supplied at a speed of 500 to 2,000 mL/min on a conveyor belt in which a belt having a width of 10 cm and a length of 2 m rotated at a speed of 50 cm/min. And, simultaneously with the supply of the monomer composition, UV light having an intensity of 10 mW/cm 2 was irradiated to conduct a polymerization reaction for 60 seconds, thereby obtaining a water-containing gel polymer having a water content of 55% by weight.

Next, the water-containing gel polymer obtained through the polymerization reaction was pulverized using a meat chopper without additives. At this time, the moisture content of the water-containing superabsorbent polymer particles included in the final pulverized material was 55% by weight.

Thereafter, the pulverized material is dried by flowing hot air at 185 ° C. from bottom to top for 20 minutes using a convection oven capable of transferring air volume up and down, and then flowing from top to bottom for 20 minutes. After drying, A super absorbent polymer having a moisture content of 25% of the final super absorbent polymer particles was prepared.

division Additives in Step 3 Example 1

(A-1)

(A-1) Example 2

(A-2) Example 3 (A-1)+(A-2) Example 4 (A-1) Comparative Example 1 Use of additives X Comparative Example 2 Monobutyl Maleate Comparative Example 3 Monolauryl Glutaratre Comparative Example 4 Dodecanoic Acid Comparative Example 5 Stearic Acid Comparative Example 6 Pluronic L35 Comparative Example 7 Additives X (Polymerization method after pre-neutralization)

test example

With respect to the superabsorbent polymer compositions prepared in the above Examples and Comparative Examples, the following methods were used to evaluate particle aggregation characteristics, centrifugal retention capacity (CRC), absorbency under load (AUP), surface tension, apparent density, amount of fine particles generated, and absorption rate. were measured, respectively, and the results are shown in Table 3 below. Unless otherwise indicated, the following physical property evaluation was carried out in a constant temperature and humidity room (23 ± 2 ℃, relative humidity 45 ± 10%), and the average value of three measurements was used as the measurement data to prevent measurement errors. In addition, in the evaluation of physical properties below, physiological saline or saline means a 0.9% by weight aqueous solution of sodium chloride (NaCl).

(1) Evaluation of particle aggregation characteristics

① For the super absorbent polymer compositions prepared in each Example and Comparative Example, 10 g of the absorbent polymer particles were cut into 6 equal parts using scissors to include at least one edge of 2 cm or longer, and then the carboxylic acid-based additive or Corresponding comparative compounds were mixed in the form of an aqueous solution according to the type and content used in each Example and Comparative Example.

② The mixture was ground at 7,200 rpm for 25 seconds using a homomixer.

③ The pulverized product was visually evaluated by applying the evaluation criteria in Table 2 below. At this time, photographs serving as examples of the evaluation items ◎, ○, △, and X are shown in FIGS. 3, 4, 5, and 6, respectively.

evaluation standard X 6 or more particles larger than 2 cm, or not ground △ In the case of 1 to 5 particles larger than 2 cm ○ No particles larger than 2 cm, but not uniformly ground ◎ When there are no particles larger than 2 cm and it is uniformly pulverized

(2) Centrifuge Retention Capacity (CRC)

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

Specifically, in the superabsorbent polymer compositions obtained through Examples and Comparative Examples, resins classified through a #30-50 sieve were obtained. This resin W ₀ (g) (about 0.2 g) was uniformly placed in a bag made of nonwoven fabric, sealed, and immersed in physiological saline (0.9% by weight) at room temperature. After 30 minutes, water was drained from the bag for 3 minutes under the condition of 250 G using a centrifuge, and the mass W ₂ (g) of the bag was measured. Moreover, after carrying out the same operation without using resin, the mass _W1 (g) at that time was measured.

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

[Equation 1]

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

(3) Absorbency under Pressure (AUP)

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

First, when measuring the absorbency under pressure, the resin classification at the time of the CRC measurement was used.

Specifically, a stainless steel 400 mesh wire mesh was attached to the bottom of a plastic cylinder having an inner diameter of 25 mm. Absorbent resin composition W ₀ (g) (0.16 g) is uniformly sprayed on a wire mesh under conditions of room temperature and 50% humidity, and a piston capable of further uniformly applying a load of 0.7 psi thereon has an outer diameter slightly greater than 25 mm It is small and has no gaps with the inner wall of the cylinder, so that up and down movement is not hindered. 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 solution composed of 0.9% by weight sodium chloride was leveled with the top surface of the glass filter. One sheet of filter paper having a diameter of 90 mm was placed thereon. The measuring device was placed on a filter paper, and the liquid was absorbed for 1 hour under a load. After 1 hour, the measuring device was lifted up and its weight W ₄ (g) was measured.

Using each obtained mass, the absorbency under pressure (g/g) was calculated according to Equation 2 below.

[Equation 2]

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

(4) Surface tension (S/T)

In order to measure the surface tension of the super absorbent polymer compositions of Examples and Comparative Examples, 0.5 g of each super absorbent polymer composition was put into 40 mL of 0.9% saline, stirred at a speed of 350 rpm for 3 minutes, and then, after stopping stirring, swelling saline containing the superabsorbent polymer was obtained. Using the saline water as a measurement sample, the surface tension of each superabsorbent polymer composition was measured using a surface tension meter (product name: Force Tensiometer-K100, manufactured by KRUSS).

(5) Bulk density (BD)

100 g of the super absorbent polymer composition of Examples and Comparative Examples was poured through an orifice of a standard fluidity measuring device, received in a container having a volume of 100 ml, and the super absorbent polymer composition was shaved horizontally to obtain a volume of 100 ml. After adjusting, the weight of only the superabsorbent polymer composition excluding the container was measured. In addition, the apparent density corresponding to the weight of the super absorbent polymer composition per unit volume was obtained by dividing the weight of the super absorbent polymer composition alone by the volume of the super absorbent polymer composition, 100 ml.

(6) Differential generation amount

The amount of fine powder generated in the super absorbent polymer compositions of Examples and Comparative Examples was less than 150 μm relative to the total weight after passing the prepared super absorbent polymer composition through a coarse grinder (2800 rpm, 0.4 mm clearance, 1 mm lower mesh condition) once. It was calculated as the ratio of the weight of the resin with the particle size.

(7) Absorption rate (Vortex time)

The absorption rate (vortex time) of the superabsorbent polymer compositions of Examples and Comparative Examples was measured in the following manner.

① First, 50 mL of 0.9% saline was added to a 100 mL beaker with a flat bottom using a 100 mL Mass Cylinder.

② Next, after placing the beaker in the center of the magnetic stirrer, a magnetic bar (diameter 8 mm, length 30 mm) was placed in the beaker.

③ Then, the stirrer was operated so that the magnetic bar was stirred at 600 rpm, and the lowest part of the vortex generated by the stirring was brought into contact with the top of the magnetic bar.

④ After confirming that the temperature of the brine in the beaker has reached 24.0 ° C, 2 ± 0.01 g of the superabsorbent polymer composition sample is injected, the stop watch is operated at the same time, and the time until the vortex disappears and the liquid surface becomes perfectly level It was measured in seconds, and this was taken as the absorption rate.

division Particle agglomeration properties
evaluation SAP properties CRC
(g/g) AUP
(g/g) S/T
(mN/m) BD
(g/ml) differential generation
(%) absorption
speed
(candle) Example 1 ◎ 42.0 25.2 71.2 0.71 4.0 33 Example 2 ◎ 42.3 25.3 71.3 0.71 3.5 30 Example 3 ◎ 42.2 25.5 71.2 0.71 3.6 31 Example 4 ◎ 42.1 25.3 71.2 0.71 3.1 27 Comparative Example 1 X 37.7 25.5 71.1 0.69 14.5 38 Comparative Example 2 X 38.3 25.0 _ _ 15.1 35 Comparative Example 3 X 36.8 25.7 68.9 0.68 16.2 36 Comparative Example 4 X 37.0 25.5 68.1 0.68 16.3 36 Comparative Example 5 X 37.8 25.3 _ _ 14.9 35 Comparative Example 6 X 38.5 25.0 _ _ 11.7 35 Comparative Example 7 X 36.7 24.3 71.3 0.68 15.4 40

Referring to Table 3 and FIGS. 3 to 6, when a superabsorbent polymer composition is prepared by adding an unneutralized polymer and an additive of Formula 1 of the present application, those additives are not used or compounds that do not conform to the structure are used. Compared to the case of mixing with a water-containing gel polymer or a neutralized water-containing gel polymer, aggregation between particles is suppressed after pulverization, so that a composition containing superabsorbent polymer particles of a desired particle size can be prepared without an additional pulverization process after drying, Accordingly, it can be seen that the amount of differential generation is reduced. Accordingly, it can be confirmed that the superabsorbent polymer composition of this example has a significantly faster absorption rate than that of the comparative example, and has water retention capacity and absorbency under pressure equal to or higher than that of the comparative example, and at the same time, exhibits a high bulk density without a decrease in surface tension. there is.

Claims (22)

superabsorbent polymer particles comprising a crosslinked polymer of a water-soluble ethylenically unsaturated monomer having an acidic group and an internal crosslinking agent; and
A superabsorbent polymer composition comprising at least one additive selected from the group consisting of a carboxylic acid represented by Formula 1 and a salt thereof:
[Formula 1]

In Formula 1,
R is straight-chain or branched-chain alkyl of 6 to 18 carbon atoms or straight-chain or branched-chain alkenyl of 6 to 18 carbon atoms.
According to claim 1,
The additive is selected from the group consisting of a carboxylic acid represented by Formula 1, an alkali metal salt thereof and an alkaline earth metal salt thereof,
A superabsorbent polymer composition.
According to claim 1,
R is a straight-chain alkyl or alkenyl having 6 to 18 carbon atoms,
A superabsorbent polymer composition.
According to claim 1,
The additive is selected from carboxylic acids represented by Formula 1-1 to Formula 1-8,
Super absorbent polymer composition:
[Formula 1-1]

[Formula 1-2]

[Formula 1-3]

[Formula 1-4]

[Formula 1-5]

[Formula 1-6]

[Formula 1-7]

[Formula 1-8]

In Formulas 1-1 to 1-8,
M ₁ and M ₂ are each independently an alkali metal or an alkaline earth metal.
According to claim 1,
The additive is contained in 0.01 to 10 parts by weight based on 100 parts by weight of the water-soluble ethylenically unsaturated monomer.
A superabsorbent polymer composition.
According to claim 1,
Further comprising a surface cross-linking layer formed by additional cross-linking of the cross-linking polymer on at least a portion of the surface of the superabsorbent polymer particle via a surface cross-linking agent,
A superabsorbent polymer composition.
According to claim 1,
The superabsorbent polymer composition,
The absorption rate (vortex time) at 24.0 ° C according to the vortex method is less than 35 seconds,
A superabsorbent polymer composition.
According to claim 1,
The superabsorbent polymer composition,
Centrifugal retention capacity (CRC) according to EDANA WSP 241.3 is 39.0 g / g or more,
A superabsorbent polymer composition.
According to claim 1,
The superabsorbent polymer composition,
Absorption under pressure (AUP) of 0.7 psi according to EDANA method WSP 242.3 is 24.0 g / g or more,
A superabsorbent polymer composition.
crosslinking polymerization of a water-soluble ethylenically unsaturated monomer having an acidic group in the presence of an internal crosslinking agent and a polymerization initiator to form a polymer (step 1);
neutralizing at least some of the acid groups of the polymer (step 2);
Preparing base resin particles by atomizing the polymer in the presence of at least one additive selected from the group consisting of carboxylic acids represented by Formula 1 and salts thereof (step 3); and
Including the step of drying the base resin particles (step 4),
Method for preparing superabsorbent polymer composition:
[Formula 1]

In Formula 1,
R is straight-chain or branched-chain alkyl of 6 to 18 carbon atoms or straight-chain or branched-chain alkenyl of 6 to 18 carbon atoms.
According to claim 10,
The step of forming the polymer (step 1) is performed in a batch type reactor,
A method for preparing a superabsorbent polymer composition.
According to claim 10,
Steps 2 and 3 are performed sequentially, simultaneously, or alternately,
A method for preparing a superabsorbent polymer composition.
According to claim 10,
The additive is prepared through a ring-opening reaction of a compound represented by Formula A below,
Method for preparing superabsorbent polymer composition:
[Formula A]

In Formula A,
R is straight-chain or branched-chain alkyl of 6 to 18 carbon atoms or straight-chain or branched-chain alkenyl of 6 to 18 carbon atoms.
According to claim 10,
The additive is contained in 0.01 to 10 parts by weight based on 100 parts by weight of the water-soluble ethylenically unsaturated monomer,
A method for preparing a superabsorbent polymer composition.
According to claim 10,
The step of preparing the base resin particles (step 3) is performed using an atomization device,
The atomization device,
A body portion including a transfer space in which a mixture of a polymer and an additive is transferred;
a screw member rotatably installed inside the transfer space to move the mixture;
a driving motor providing rotational driving force to the screw member; and
A cutter member including a perforated plate installed in the body and having a plurality of holes formed therein, and pulverizing the mixture while discharging it to the outside of the body;
A method for preparing a superabsorbent polymer composition.
According to claim 10,
Steps 2 and 3 are performed sequentially, simultaneously, or alternately,
Steps 2 and 3 are performed using an atomization device,
The atomization device,
A body portion including a transfer space in which a mixture of a polymer and an additive is transferred;
a screw member rotatably installed inside the transfer space to move the mixture;
a driving motor providing rotational driving force to the screw member;
a cutter member installed on the body, including a perforated plate having a plurality of holes, and pulverizing the mixture while discharging it to the outside of the body; and
Further comprising a neutralizer injection nozzle installed inside the body portion,
A method for preparing a superabsorbent polymer composition.
According to claim 16,
In the atomization device,
The neutralizer is injected into the body through the neutralizer injection nozzle to neutralize at least some of the acid groups of the polymer having acid groups in the mixture.
A method for preparing a superabsorbent polymer composition.
According to claim 16,
The hole size formed in the perforated plate is 0.1 mm to 30 mm,
A method for preparing a superabsorbent polymer composition.
According to claim 10,
The step of drying the base resin particles (step 4) is performed in a moving type,
A method for preparing a superabsorbent polymer composition.
According to claim 10,
In the step of drying the base resin particles (step 4),
Performed using a moving type dryer of a horizontal-type mixer, a rotary kiln, a paddle dryer, or a steam tube dryer,
A method for preparing a superabsorbent polymer composition.
According to claim 10,
The moisture content of the superabsorbent polymer particles obtained in the step of drying the base resin particles (step 4) is 10% to 20% by weight,
A method for preparing a superabsorbent polymer composition.
According to claim 10,
In the presence of a surface cross-linking agent, forming a surface cross-linking layer on at least a portion of the surface of the superabsorbent polymer particles prepared in step 4,
A method for preparing a superabsorbent polymer composition.

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