KR102814159B1 - Super absorbent polymer particle, composition indcluding the same, preparation method for of the same - Google Patents

Abstract

The present invention relates to a method for producing superabsorbent resin particles and superabsorbent resin particles.
Specifically, the present invention provides superabsorbent resin particles having a substituted or unsubstituted C _10-30 alkyl group introduced to the surface and a composition in which the superabsorbent resin particles are dispersed in an organic solvent.
In addition, a method for producing the superabsorbent resin particles by reverse emulsification polymerization in the presence of a reactive surfactant (surfmer) of a specific structure is provided.

Description

SUPER ABSORBENT POLYMER PARTICLE, COMPOSITION INDCLUDING THE SAME, PREPARATION METHOD FOR THE SAME

The present invention relates to superabsorbent resin particles, a composition comprising the same, and a method for producing the same.

Super Absorbent Polymer (SAP) is a synthetic polymer material that can absorb 500 to 1,000 times its own weight in moisture. Different developers call it by different names, such as SAM (Super Absorbency Material) and AGM (Absorbent Gel Material).

These superabsorbent resins can be manufactured from water-soluble ethylenically unsaturated monomers such as acrylic acid, and various polymerization methods are known for their manufacturing, including solution polymerization, reverse phase suspension polymerization, dispersion polymerization, and photopolymerization, but generally, a method using solution polymerization is used.

When using solution polymerization, a hygroscopic high molecular weight monomer dissolved in water is bulk polymerized together with a crosslinking agent to obtain a hydrogel, which is then dried, pulverized, and classified to obtain a superabsorbent resin.

Other methods, such as suspension polymerization, can be used to obtain smaller superabsorbent resin particles, but when superabsorbent resin particles containing a large amount of moisture on the particle surface are created, irreversible aggregation occurs between the particles, and the particles are physically crushed before use.

During physical crushing or pulverization, the particle size is not uniformly controlled, and the particle size is generally about 150 to 850 ㎛, so there is a problem that particles with a diameter in the nano-level range cannot be obtained.

In order to solve the above-mentioned problem, the present invention provides superabsorbent resin particles having a substituted or unsubstituted C _10-30 alkyl group introduced to the surface and a composition in which the superabsorbent resin particles are dispersed in an organic solvent.

In addition, a method for producing the superabsorbent resin particles by reverse emulsification polymerization in the presence of a reactive surfactant (surfmer) of a specific structure is provided.

Specifically, in one embodiment of the present invention, specifically, in the manufacturing method of the one embodiment, a superabsorbent resin particle is provided, which comprises a crosslinked polymer of an acrylic acid-based monomer having an acidic group and at least a part of the acidic group being neutralized; and a compound bonded to a surface functional group of the crosslinked polymer and represented by the following chemical formula 1:

[Chemical Formula 1]

In the chemical formula 1 above, n is an integer from 1 to 10, R is a substituted or unsubstituted C _10-30 alkyl, and the dotted line indicates a bond with a surface functional group of the crosslinked polymer.

In another embodiment of the present invention, a superabsorbent resin composition is provided, comprising: an organic solvent; and superabsorbent resin particles dispersed in the organic solvent.

In another embodiment of the present invention, there is provided a step of preparing a monomer mixture comprising an acrylic acid-based monomer having an acidic group and at least a portion of the acidic group being neutralized, a polymerization initiator, and an internal cross-linking agent;

A step for preparing a surfactant solution containing 60 to 190 parts by weight of a compound represented by the following chemical formula 2 alone; or a mixture of a compound represented by the following chemical formula 2 and a non-reactive surfactant; based on 100 parts by weight of the above monomer;

A step of forming a pre-emulsion by mixing the above surfactant solution with the above monomer mixture; and

A step of polymerizing a monomer mixture in the above pre-emulsion to obtain a composition including superabsorbent resin particles; comprising;

Provided is a method for producing superabsorbent resin particles:

[Chemical formula 2]

In the above chemical formula 2, n is an integer from 1 to 5, and R is a substituted or unsubstituted C _10-30 alkyl.

According to the manufacturing method of the above embodiment, superabsorbent resin particles having a small particle size, a uniform distribution, and improved dispersibility in an organic solvent can be manufactured, compared to cases where other polymerization methods are used or where a reverse emulsification polymerization method is used but a surfactant having a structure different from that of the above chemical formula 2 is used.

By using these superabsorbent resins, sanitary materials such as diapers and sanitary pads can be provided that can quickly absorb body fluids and provide a soft feel.

Figure 1 is an FE-SEM image of the final product of Example 1.
Figure 2 is an FE-SEM image of the final product of Example 2.
Figure 3 is an FE-SEM image of the final product of Example 3.
Figure 4 is an FE-SEM image of the final product of Example 4.
Figure 5 is an FE-SEM image of the final product of Example 5.
Figure 6 is an FE-SEM image of the final product of Comparative Example 1.
Figure 7 is an FE-SEM image of the final product of Comparative Example 2.

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

Additionally, the terminology used herein is for the purpose of describing exemplary embodiments only and is not intended to limit the present invention.

Singular expressions include plural expressions unless the context clearly indicates otherwise. In this specification, the terms "comprises," "includes," or "has" are intended to describe implemented features, numbers, steps, components, or combinations thereof, but do not exclude the possibility of one or more other features, numbers, steps, components, combinations, or additions thereof.

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

Unless otherwise defined herein, “copolymerization” may mean a block copolymer, a random copolymer, a graft copolymer or an alternating copolymer, and “copolymer” may mean a block copolymer, a random copolymer, a graft copolymer or an alternating copolymer.

Additionally, in this specification, (meth)acrylate means both acrylate and methacrylate.

The term "substituted or unsubstituted" as used herein means a group which is unsubstituted or substituted with one or more substituents selected from the group consisting of deuterium; a halogen group; a nitrile group; a nitro group; a hydroxy group; a carbonyl group; an ester group; an imide group; an amino group; a phosphine oxide group; an alkoxy group; an aryloxy group; an alkylthioxy group; an arylthioxy group; an alkylsulfoxy group; an arylsulfoxy group; a silyl group; a boron group; an alkyl group; a cycloalkyl group; an alkenyl group; an aryl group; an aralkyl group; an aralkenyl group; an alkylaryl group; an alkylamine group; an aralkylamine group; a heteroarylamine group; an arylamine group; an arylphosphine group; or a heterocyclic group containing at least one of N, O, and S atoms, or a substituted or unsubstituted group in which two or more of the above-mentioned substituents are linked. For example, the "substituent linked with two or more substituents" can be a biphenyl group. That is, the biphenyl group can be an aryl group, or it can be interpreted as a substituent in which two phenyl groups are connected.

The present invention may have various modifications and may take various forms, and specific embodiments are exemplified and described in detail below. However, this does not limit the present invention to a specific disclosed form, but should be understood to include all modifications, equivalents, or substitutes included in the spirit and technical scope of the present invention.

Throughout this specification, saline solution means saline solution (0.9% NaCl).

Hereinafter, embodiments of the present invention will be described in detail.

Superabsorbent resin

In one embodiment of the present invention, a superabsorbent resin particle is provided, which comprises a crosslinked polymer of an acrylic acid-based monomer having an acidic group and at least a portion of the acidic group being neutralized; and a compound bonded to a surface functional group of the crosslinked polymer and represented by the following chemical formula 1:

[Chemical Formula 1]

In the chemical formula 1 above, n is an integer from 1 to 10, R is a substituted or unsubstituted C _10-30 alkyl, and the dotted line indicates a bond with a surface functional group of the crosslinked polymer.

The compound represented by the above chemical formula 1 is bonded to the surface functional group of the cross-linked polymer via a methacrylate functional group, and as a result, the alkyl chain (i.e., a substituted or unsubstituted C _10-30 alkyl group) at the terminal of the compound represented by the above chemical formula 1 hydrophobically modifies the outer surface of the superabsorbent resin particle and contributes to improving the dispersibility of the superabsorbent resin particle.

By using these superabsorbent resins, sanitary materials such as diapers and sanitary pads can be provided that can quickly absorb body fluids and provide a soft feel.

Specifically, the superabsorbent resin particles of the above embodiment may be polymerized in reverse emulsification in the presence of a compound represented by the following chemical formula 2, so as to have a small particle size, a uniform distribution, and improved dispersibility in an organic solvent:

[Chemical formula 2]

In the above chemical formula 2, n is an integer from 1 to 10, and R is a substituted or unsubstituted C _10-30 alkyl.

More specifically, the superabsorbent resin particles of the above embodiment may be reverse-emulsified in the presence of a compound represented by the above chemical formula 2 alone; or a mixture of the compound represented by the above chemical formula 2 and a non-reactive surfactant. In the latter case, the non-reactive surfactant may be sorbitan monooleate, polyoxyethylene sorbitan monooleate, or a mixture thereof.

The compound represented by the above chemical formula 2 is a type of reactive surfactant (surfmer) capable of participating in a reverse emulsification polymerization reaction.

Accordingly, in the process of synthesizing an acrylic acid monomer having the acidic group and at least a portion of the acidic group being neutralized into a crosslinked polymer, the methacrylate functional group in the compound represented by the chemical formula 2 can react with the surface functional group of the crosslinked polymer.

Additionally, the alkyl chain (i.e., a substituted or unsubstituted C _10-30 alkyl group) bonded to the other terminal of the ethylene oxide repeating unit in the compound represented by the chemical formula 2 may face the outer surface of the superabsorbent resin particle.

The compound represented by the above chemical formula 1 corresponds to a form in which the compound represented by the above chemical formula 2 is combined with a surface functional group of the above cross-linked polymer.

A detailed description of the materials used in the manufacture of the superabsorbent resin particles of the above embodiment, including the compound represented by the above chemical formula 2, will be provided below.

The superabsorbent resin particles of the above embodiment may have a size of 0.1 to 20 μm, specifically 0.1 to 10 μm, for example 0.1 to 5 μm.

Here, the size of the superabsorbent resin particles may be the diameter of the superabsorbent resin particles. For example, after drying the superabsorbent resin particles in a vacuum oven at 60°C, an image of the external surface of the superabsorbent resin particles is taken using a FE-SEM (Field Emission Scanning Electron Microscope, product name: S-4800, manufacturer: Hitachi), and the size (diameter) can be confirmed from the taken image.

Superabsorbent resin composition

In another embodiment of the present invention, a superabsorbent resin composition is provided, comprising: an organic solvent; and the superabsorbent resin particles described above dispersed in the organic solvent.

The alkyl chain (i.e., substituted or unsubstituted C _10-30 alkyl group) in the superabsorbent resin particles described above is introduced into the superabsorbent resin particles in a manner that it bonds with the surface of the crosslinked polymer, thereby modifying the surface thereof to be hydrophobic and contributing to improving the dispersibility of the superabsorbent resin particles.

Accordingly, in the superabsorbent resin composition, the dispersibility of the superabsorbent resin particles described above can be excellent.

For example, the above-mentioned superabsorbent resin particles can be dispersed in an alkane series organic solvent at a content of 5 wt% or more of the total solution weight (100 wt%).

However, this is an example, and the number of carbon atoms in the alkane series organic solvent or the degree of dispersion of the superabsorbent resin particles therein are not particularly limited.

Method for producing superabsorbent resin

In one embodiment of the present invention, a method for producing superabsorbent resin particles by reverse emulsification polymerization in the presence of a methacrylate compound having a specific structure is provided.

Specifically, in the manufacturing method of the above embodiment,

A step of preparing a monomer mixture comprising an acrylic acid-based monomer having an acidic group and at least a portion of the acidic group being neutralized, a polymerization initiator, and an internal cross-linking agent;

A step for preparing a surfactant solution containing 60 to 190 parts by weight of a compound represented by the following chemical formula 2 alone; or a mixture of a compound represented by the following chemical formula 2 and a non-reactive surfactant; based on 100 parts by weight of the above monomer;

A step of forming a pre-emulsion by mixing the above surfactant solution with the above monomer mixture; and

A step of polymerizing a monomer mixture in the above pre-emulsion to obtain a composition including superabsorbent resin particles; comprising;

Provided is a method for producing superabsorbent resin particles:

[Chemical formula 2]

In the above chemical formula 2, n is an integer from 1 to 5, and R is a substituted or unsubstituted C _10-30 alkyl.

reverse emulsification polymerization

Inverse emulsion polymerization refers to a method of dissolving a monomer in water to produce an aqueous dispersion, emulsifying it in a continuous organic medium to form a pre-emulsion (inverse emulsion emulsion), and then polymerizing it within the pre-emulsion.

Specifically, the reverse emulsion polymerization method is a method in which a monomer dissolved in water is stabilized by a surfactant to form monomer droplets, and the reaction proceeds through a mechanism of reaction initiation - growth - termination in the same process as conventional oil-in-water emulsion polymerization.

This reverse emulsion polymerization method can polymerize a hydrophilic monomer using an organic solvent or oil as a continuous phase. However, since the emulsion stability is low compared to emulsion polymerization, the emulsion can easily clump during the polymerization reaction, so by using an appropriate surfactant, small and uniform particles can be formed compared to solution polymerization or suspension polymerization. That is, in the case of the reverse emulsion polymerization method including an appropriate surfactant, superabsorbent resin particles having a small synthesized particle size, a uniform distribution, and improved dispersibility in an organic solvent can be obtained.

Methacrylate compound represented by chemical formula 2 (reactive surfactant)

Meanwhile, even if the reverse emulsification polymerization method is used, the particle size, distribution, and dispersibility of the final product (superabsorbent resin particles) may vary depending on the surfactant added to the organic medium in the continuous phase.

Specifically, non-reactive surfactants have low adsorption stability at the emulsion interface at high temperatures, and thus fail to form a stable pre-emulsion (reverse emulsion) during the polymerization process, resulting in the formation of superabsorbent resin particles with a large variation in particle size.

Accordingly, it is necessary to use a reactive surfactant (surfmer) that is more stable at high temperatures by reacting with the monomer at the emulsion interface. In particular, in this case, the dispersibility of hydrophilic superabsorbent resin particles in an organic solvent is improved, so that the agglomeration of particles before and after polymerization is minimized.

Meanwhile, among reactive surfactants, if the surfactant contains an aromatic ring in the molecule, agglomeration occurs between the reactive surfactants present at the emulsion interface before and after polymerization due to π(pi)-π(pi) interaction, van der Waals attraction, etc., preventing the formation of nano-sized superabsorbent resin particles. Therefore, it is necessary to avoid reactive surfactants containing an aromatic ring in the molecule.

In addition, the reactive surfactant has a structure that introduces a functional group to a nonionic surfactant. If an ionic surfactant is used, the HLB value is high and it is not suitable for reverse emulsion polymerization. In addition, even if the hydrophilic group of the nonionic surfactant does not contain an ethylene oxide (EO) repeating unit and contains an amine or sulfur, the HLB value is high and it is not suitable for reverse emulsion polymerization. Therefore, it is necessary to use a reactive surfactant containing an ethylene oxide (EO) repeating unit so that it can have an HLB suitable for reverse emulsion polymerization.

In this regard, in the manufacturing method of the above embodiment, it is decided to use a reactive surfactant containing 1 to 10 ethylene oxide (EO) repeating units without including an aromatic ring in the molecule. This reactive surfactant corresponds to a methacrylate compound represented by the above chemical formula 2:

The methacrylate compound represented by the above chemical formula 2 does not contain an aromatic ring in the molecule, so that agglomeration does not occur during a polymerization reaction, and has an HLB suitable for reverse emulsion polymerization by containing 1 to 10 ethylene oxide (EO) repeating units, and introduces an alkyl chain of the above chemical formula 2 (i.e., a substituted or unsubstituted C _10-30 alkyl group) to the outer surface of a superabsorbent resin particle, thereby modifying the surface to be hydrophobic and contributing to improving the dispersibility of the superabsorbent resin particle.

In the above chemical formula 2, the number of ethylene oxide (EO) repeating units (i.e., n) can be an integer from 1 to 10, specifically an integer from 1 to 5; and the alkyl chain (i.e., R) can be a substituted or unsubstituted C _10-30 alkyl, specifically a substituted or unsubstituted C _10-20 alkyl.

Within this range, the compound represented by the chemical formula 2 may have an HLB (Hydrophile-Lipophile Balance) value of 1 to 8, specifically 3 to 7, for example 4 to 6.5, which is suitable for reverse emulsion polymerization.

In this case, the compound represented by the chemical formula 2 may have (the number of carbon atoms in the alkyl chain (R))/n of 2 to 10, specifically 5 to 10, for example 8 to 10.

For example, the compound represented by the above chemical formula 2 may be a compound represented by the following chemical formula 2-1, a compound represented by the following chemical formula 2-2, or a compound represented by the following chemical formula 2-3, and its HLB value may be 4 to 6.5, and (the number of carbon atoms in the alkyl chain (R))/n may be 8 to 10. Of course, it is also possible to use them in mixture:

.[Chemical Formula 2-1]

.

[Chemical Formula 2-2]

[Chemical Formula 2-3]

Surfactant solution

The above surfactant solution can be prepared by mixing the compound represented by the above chemical formula 2 with liquid paraffin and, if necessary, adding a non-reactive surfactant.

However, when the compound represented by the chemical formula 2 is used alone and the amount used exceeds 180 parts by weight, a clumping phenomenon may occur between emulsions due to the attractive force between the alkyl chains.

In addition, when the compound represented by the above chemical formula 2 is used alone and the amount used is less than 60 parts by weight, spherical superabsorbent particles themselves are produced, but the particle size is produced to be relatively large, so that the dispersibility in the organic solvent may be reduced.

Meanwhile, when using a mixture of a compound represented by the above chemical formula 2 and a non-reactive surfactant, if the amount of the non-reactive surfactant increases and the total amount of the mixture exceeds 180 parts by weight, some agglomeration occurs between the surfactants, widening the particle size distribution, and the methacrylate compound represented by the above chemical formula 2 is difficult to introduce to the surface of each particle, so that dispersibility may be somewhat reduced.

Therefore, the compound represented by the above chemical formula 2 alone; or the mixture of the compound represented by the above chemical formula 2 and a non-reactive surfactant needs to be used in an amount of 60 to 190 parts by weight, specifically 65 to 185 parts by weight, for example 70 to 180 parts by weight, based on 100 parts by weight of the above monomer.

Within the above range, superabsorbent resin particles having a uniform particle size and suppressing agglomeration between particles can be manufactured.

In the above surfactant solution, the compound represented by the chemical formula 2 can be purchased as a commercially available product or can be manufactured directly and used.

In the latter case, the step of forming a pre-emulsion by mixing a surfactant solution containing a compound represented by the chemical formula 2 with the monomer mixture may further include a step of preparing a compound represented by the chemical formula 2 beforehand.

Specifically, the step of preparing the compound represented by the chemical formula 2 may be a step of reacting the compound represented by the chemical formula 2-1-1 below with methacryloyl chloride.

[Chemical Formula 2-1-1]

In the above chemical formula 2-1-1, the definitions of n and R are as in chemical formula 2. That is, n is an integer from 1 to 10, and R is a substituted or unsubstituted C _10-30 alkyl.

More specifically, a compound represented by the chemical formula 2-1-1 can be reacted with methacryloyl chloride to produce a compound represented by the chemical formula 2. This reaction can be performed in the presence of triethylamine (TEA) and dichloromethane (DCM), and can be represented by the following reaction scheme 1.

[Reaction Formula 1]

For example, when it is desired to prepare a compound represented by the chemical formula 2-1, a compound represented by the chemical formula 2-2 below, or a compound represented by the chemical formula 2-3 below among the compounds represented by the chemical formula 2 above, the following reaction formulas 1-1 to 1-3 can be used:

[Reaction Formula 1-1]

[Reaction Formula 1-2]

[Reaction Formula 1-3]

However, the above reaction schemes 1-1 to 1-3 are only examples, and by utilizing the above reaction scheme 1, and particularly by appropriately controlling the number of alkyl groups and ethylene oxide repeating units of the compound represented by the above chemical formula 2-1-1, which is a reactant, the compound represented by the above chemical formula 2 can be manufactured. In addition, conditions such as reaction temperature and time can be controlled according to common sense in the art.

The surfactant solution may be a continuous oil comprising 60 to 190 parts by weight of a compound represented by the chemical formula 2 alone or a mixture of a compound represented by the chemical formula 2 and a non-reactive surfactant, based on 100 parts by weight of the monomer, and 3,000 to 4,000 parts by weight of liquid paraffin.

Within the above range, as the content of the compound represented by the above chemical formula 2 increases, some agglomeration phenomenon occurs between surfactants, which widens the particle size distribution, and the methacrylate compound represented by the above chemical formula 2 is difficult to introduce to the surface of each particle, which may result in some reduction in dispersibility.

Considering this tendency, the content of the compound represented by the chemical formula 2 can be adjusted to 60 parts by weight or more, 65 parts by weight or more, or 70 parts by weight or more, and 190 parts by weight or less, 185 parts by weight or less, or 180 parts by weight or less, based on 100 parts by weight of the monomer.

The above non-reactive surfactant can play a role in preventing aggregation between resin particles by reducing the water solubility of resin particles present in the solvent.

The type of the non-reactive surfactant may be selected in consideration of the relationship with the compound represented by the chemical formula 2. Specifically, the non-reactive surfactant may be at least one compound selected from the group including alcohols, alkanes, mercaptans, carboxylic acids, ketones, amines, and nonionic surfactants having a HLB (Hydrophile-Lipophile Balance) value of 11 or less having 10 to 40 carbon atoms.

Specifically, the non-reactive surfactant may be hexadecane, cetyl alcohol, polyoxyethylene stearyl ether, polyoxyethylene stearyl amine, polyoxyethylene stearyl ester, polyoxyethylene monostearate, polyoxyethylene sorbitan monooleate, polyoxyethylene lauryl ether, an ethoxylated alcohol having 10 to 20 carbon atoms, ethoxylated octylphenol, an ethoxylated fatty ester, sorbitan laurate, sorbitan monostearate, propylene glycol monostearate, ethylene glycol monostearate, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, or a mixture thereof.

For example, the non-reactive surfactant may be a mixture of sorbitan monooleate and polyoxyethylene sorbitan monooleate in a weight ratio of 5:1 to 1:5, specifically 3:1 to 1:3.

More specifically, when the compound represented by the chemical formula 2 is used alone, the surfactant solution may be a solution composed of 60 to 90 parts by weight (e.g., 70 to 80 parts by weight) of the compound represented by the chemical formula 2 and 3,000 to 4,000 parts by weight of liquid paraffin, based on 100 parts by weight of the monomer.

In contrast, when using a mixture of a compound represented by the chemical formula 2 and a non-reactive surfactant (i.e., a mixture of a non-reactive surfactant and a reactive surfactant), the solution may be composed of 1 to 90 parts by weight (e.g., 5 to 80 parts by weight) of the compound represented by the chemical formula 2, 60 to 90 parts by weight (e.g., 70 to 80 parts by weight) of sorbitan monooleate, 10 to 40 parts by weight (e.g., 20 to 30 parts by weight) of polyoxyethylene sorbitan monooleate, and 3,000 to 4,000 parts by weight of liquid paraffin, based on 100 parts by weight of the monomer. However, the mixture of the compound represented by the chemical formula 2 and the non-reactive surfactant should be within a total range of 60 to 190 parts by weight.

When the surfactant content is controlled in this way, the particle size can be made more uniform and the agglomeration phenomenon between particles can be significantly suppressed.

Monomer

In the manufacturing method of the above embodiment, an acrylic acid-based monomer having an acidic group and at least a portion of the acidic group being neutralized is used.

Since these monomers are water-soluble, they cannot be used in oil in water (O/w) emulsion polymerization, where the continuous phase is an aqueous solution (water phase).

The above monomer may be a compound represented by the following chemical formula 4:

[Chemical Formula 4] R1-COOM1

In the above chemical formula 4, R1 is an alkyl group having 2 to 5 carbon atoms containing an unsaturated bond; M1 is a hydrogen atom, a monovalent or divalent metal, an ammonium group, or an organic amine salt.

The above monomer may include, for example, at least one selected from the group consisting of acrylic acid, methacrylic acid, and monovalent metal salts, divalent metal salts, ammonium salts, and organic amine salts thereof.

Here, the monomer has an acidic group, and at least a portion of the acidic group may be neutralized. Preferably, the monomer partially neutralized with a basic substance such as sodium hydroxide, potassium hydroxide, ammonium hydroxide, etc. may be used. At this time, the degree of neutralization of the acrylic acid-based monomer may be adjusted to less than about 85 mol%, or about 40 to about 80 mol%, or about 50 to about 70 mol%.

If the degree of neutralization is too high, the neutralized monomer may precipitate, making it difficult for polymerization to proceed smoothly. Furthermore, the effect of additional neutralization after the initiation of surface crosslinking is substantially eliminated, so that the degree of crosslinking of the surface crosslinking layer is not optimized, and the liquid permeability of the superabsorbent resin may become insufficient. On the other hand, if the degree of neutralization is too low, not only is the absorbency of the polymer greatly reduced, but it may also exhibit properties like elastic rubber that are difficult to handle.

In this regard, the step of preparing the monomer mixture may further include a step of mixing a water-soluble ethylenically unsaturated monomer with an alkaline solution to neutralize at least a portion of the acidic groups of the water-soluble ethylenically unsaturated monomer.

The concentration of the above monomer may be about 20 to about 60 wt%, or about 30 to about 55 wt%, or about 40 to about 50 wt% with respect to the monomer mixture including the raw material of the superabsorbent resin and the solvent, and may be appropriately adjusted in consideration of the polymerization time and reaction conditions.

If the concentration of the above monomer is too low, the yield of the superabsorbent resin may be low, which may cause problems with economic feasibility. On the other hand, if the concentration of the monomer is too high, some of the monomer may be precipitated, or the pulverization efficiency may be low when the polymerized polymer is pulverized, which may cause problems in the process, and the physical properties of the superabsorbent resin may be deteriorated.

Manufacturing process of monomer mixture

In the manufacturing method of the above embodiment, a monomer mixture including an acrylic acid-based monomer having an acidic group and at least a portion of the acidic group being neutralized, a polymerization initiator, and an internal cross-linking agent is manufactured.

The above monomer mixture can be prepared in the form of a monomer mixture aqueous solution in which the monomer, polymerization initiator, and internal cross-linking agent are dispersed in water.

When the above polymerization initiator is used as one that dissolves in the aqueous solution of the above-described dispersed phase, the manufactured pre-emulsion can be more stable compared to when the polymerization initiator is used as one that dissolves in the organic medium of the continuous phase described later.

Since the compound represented by the above chemical formula 2 is hydrophobic with one end having 10 or more carbon atoms, when it is added to a monomer mixture, which is a dispersed aqueous solution, rather than to a continuous oil, the compounds represented by the above chemical formula 2 may clump together and phase separate from the monomer mixture.

polymerization initiator

The polymerization initiator used in the manufacturing method of the above embodiment is not particularly limited as long as it is generally used in the manufacturing of superabsorbent resins.

Specifically, the polymerization initiator may be a thermal polymerization initiator or a photopolymerization initiator by UV irradiation depending on the polymerization method. However, even if the photopolymerization method is used, a certain amount of heat may be generated by UV irradiation, etc., and a certain amount of heat may be generated depending on the progress of the polymerization reaction, which is an exothermic reaction. Therefore, a thermal polymerization initiator may be additionally included.

The above photopolymerization initiator can be used without limitation in its composition as long as it is a compound that can form radicals by light such as ultraviolet light.

As the photopolymerization initiator, for example, at least one selected from the group consisting of benzoin ether, dialkyl acetophenone, hydroxyl alkylketone, phenyl glyoxylate, benzyl dimethyl ketal, acyl phosphine, and α-aminoketone can be used. Meanwhile, as a specific example of the acylphosphine, commercially available lucirin TPO, i.e., 2,4,6-trimethyl-benzoyl-trimethyl phosphine oxide, can be used. A more detailed description of the various photoinitiators is given in Reinhold Schwalm's book 'UV Coatings: Basics, Recent Developments and New Applications (Elsevier 2007)' p115, and is not limited to the examples described above.

In addition, as the thermal polymerization initiator, at least one selected from the group of initiators consisting of a persulfate-based initiator, an azo-based initiator, hydrogen peroxide, and ascorbic acid can be used. Specifically, examples of persulfate initiators include sodium persulfate (Na ₂ S ₂ O ₈ ), potassium persulfate (K ₂ S ₂ O ₈ ), and ammonium persulfate (A mmonium persulfate; (NH ₄ ) ₂ S ₂ O ₈ ), and examples of azo initiators include 2, 2-azobis(2-amidinopropane) dihydrochloride, 2, 2-azobis-(N, N-dimethylene)isobutyramidine dihydrochloride, Examples thereof include 2-(carbamoylazo)isobutylonitril, 2,2-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride, and 4,4-azobis-(4-cyanovaleric acid). A more diverse range of thermal polymerization initiators is described in Odian's book, 'Principle of Polymerization (Wiley, 1981),' p203, and is not limited to the examples described above.

Such polymerization initiator may be added at a concentration of about 0.001 to 1 wt%, preferably about 0.1 to about 0.9 wt%, based on the total weight of the monomer mixture. If the concentration of the polymerization initiator is too low, the polymerization rate may be slow and a large amount of residual monomer may be extracted from the final product, which is not preferable. On the other hand, if the concentration of the polymerization initiator is higher than the above range, the polymer chains forming the network may become shorter, which may increase the content of water-soluble components and lower the pressure absorbency, thereby deteriorating the properties of the resin, and the polymerization rate may be too fast, so that the polymerization proceeds in a state where the pre-emulsion (reverse emulsion) is not stabilized, which may cause agglomeration between particles, which is not preferable.

For example, in the above-described embodiment, 0.1 to 10 parts by weight of ammonium persulfate ((NH ₄ ) ₂ S ₂ O ₈ ), which is a thermal polymerization initiator, may be used based on 100 parts by weight of the ethylenically unsaturated monomer.

Internal crosslinker

The above monomer mixture is a raw material for a superabsorbent resin and contains an internal cross-linking agent having a special chemical structure.

These internal cross-linking agents are for cross-linking the interior of a polymer in which an acrylic acid monomer is polymerized, i.e., a base resin, and are distinguished from surface cross-linking agents for cross-linking the surface of the polymer.

At this time, it may be preferable that the cross-linking bond is formed by at least one cross-linking agent selected from the group consisting of a diol diacrylate cross-linking agent, an alkylene carbonate cross-linking agent, a bis(meth)acrylamide cross-linking agent, a polyol poly(meth)acrylate cross-linking agent, and a polyol poly(meth)allyl ether cross-linking agent.

Examples of the above diol diacrylate crosslinking agent include ethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, propylene glycol di(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, and tetraethylene glycol di(meth)acrylate.

Examples of the alkylene carbonate crosslinking agent include compounds containing a straight-chain or branched divalent alkylene group and a carbonate unit, such as ethylene carbonate, propylene carbonate, and butylene carbonate.

In addition, other crosslinking agents include N,N'-methylenebis(meth)acrylate, ethyleneoxy(meth)acrylate, polyethyleneoxy(meth)acrylate, propyleneoxy(meth)acrylate, glycerin diacrylate, glycerin triacrylate, trimethylol triacrylate, triallylamine, triaryl cyanurate, triallyl isocyanate, polyethylene glycol, diethylene glycol, and propylene glycol.

For example, in the manufacturing method of the above embodiment, N', N'-methylenebis(acrylamide) can be used as an internal cross-linking agent. This can contribute to manufacturing superabsorbent resin particles that are suitable for reverse emulsion polymerization, have a small particle size, uniform distribution, and improved dispersibility in an organic solvent.

The internal cross-linking agent may be used in an amount of 3 to 4 parts by weight, specifically 3.2 to 3.7 parts by weight, based on 100 parts by weight of the monomer.

These internal cross-linking agents are included in a concentration of about 0.01 to about 2 wt%, or about 0.05 to about 1.8 wt%, or about 0.2 to about 1.5 wt% based on the total weight of the monomer mixture, and can introduce a cross-linking structure into the cross-linked polymer and the base resin powder formed therefrom.

If the concentration of the internal cross-linking agent is too low, the absorption rate of the superabsorbent resin may be low and the gel strength may be weakened, which is not desirable. Conversely, if the concentration of the internal cross-linking agent is too high, the absorption capacity of the superabsorbent resin may be low, which is not desirable as an absorbent.

Manufacturing process of pre-emulsion

In the manufacturing method of the above embodiment, the monomer mixture, which is an aqueous solution in a dispersed phase, and the surfactant solution, which is an oil in a continuous phase, are mixed to form a pre-emulsion.

Here, the surfactant solution may be mixed with the monomer mixture and stirred at a rotation speed of 300 to 800 rpm, specifically 400 to 600 rpm.

Here, the above pre-emulsion can be formed under nitrogen purging conditions.

Polymerization process

In the manufacturing method of the above embodiment, if it is a polymerization method for polymerizing the monomer mixture in the pre-emulsion, there is no particular limitation on the composition.

Specifically, polymerization methods can be broadly divided into thermal polymerization and photopolymerization depending on the polymerization energy source.

For example, the polymerization of the monomer mixture in the pre-emulsion may be carried out by thermal polymerization and may be performed at a temperature range of 50 to 90° C., specifically 60 to 80° C., for 1 to 30 hours, specifically 3 to 18 hours.

In the case of a reactor, there is no particular limitation as long as it is a reactor that can implement the above reaction conditions.

Process after polymerization

According to the manufacturing method of the above embodiment, a composition including superabsorbent resin particles which are crosslinked polymers is obtained.

In order to obtain superabsorbent resin particles from the composition, the method may further include: a step of obtaining a composition including the superabsorbent resin particles; thereafter, a step of separating a liquid from the composition including the superabsorbent resin particles to recover the superabsorbent resin particles; a step of washing the recovered superabsorbent resin particles; and a step of drying the washed superabsorbent resin particles.

However, since superabsorbent resin particles having a small particle size, uniform distribution, and improved dispersibility in an organic solvent are obtained, an additional grinding process is unnecessary.

The above solid/liquid separation process, washing process, and drying process can utilize methods generally known in the art, and a detailed description thereof is omitted.

The manufacturing method of the above embodiment may further include a surface cross-linking step.

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

However, the process of manufacturing superabsorbent resin particles using a reverse emulsification polymerization method and then forming a surface cross-linking layer using a surface cross-linking solution containing a compound represented by the chemical formula 2 is avoided.

Since the surface cross-linking solution is mostly in an aqueous state, not only is the compound represented by the chemical formula 2 not well dispersed, but the particles may swell, making it difficult to use. In addition, the functional groups of the monomer for producing the superabsorbent resin are all consumed during the polymerization process, so the reactivity with the resin is minimal.

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

<Synthesis of reactive surfactant (surfmer)>

A reactive surfactant was prepared by referring to the following literature.

Li, Y., & Ren, Q. (2018). Synthesis, characterization, and solution properties of a surface-active hydrophobically associating polymer. Journal of Applied Polymer Science, 135(32), 46569.

Manufacturing example 1 (surfmer 1): Methacrylate compound represented by chemical formula 2-1 (Brij93-methacrylate; HLB: 4.14)

20 mmol of Brij 93 (Mn ~357 g/mol) is dissolved in 100 mL of dichloromethane (DCM), and 24 mmol of triethylamine (TEA) is added while stirring at 300 rpm under a nitrogen atmosphere. The flask containing the above solution is immersed in an ice bath, and when the temperature drops below 5°C, 22 mmol of methacryloyl chloride (MAC) dissolved in 50 mL of DCM is added using a syringe pump for 30 minutes. The syringe pump speed is 1.67 ml/min, and the temperature is maintained below 10°C during the reaction. The mixed solution is stirred at room temperature for 24 hours, and after the reaction is complete, the solvent is evaporated using a rotary evaporator, and then the TEA salt formed as a by-product is removed through reduced pressure filtration. Afterwards, the organic phase was washed with a saturated sodium chloride aqueous solution until the pH value of the organic phase became 7, and anhydrous sodium sulfate was added to the separated organic phase and stirred for 1 hour to remove the moisture remaining in the organic phase. The sodium sulfate in the solution was removed through reduced pressure filtration, and the solvent was evaporated using a rotary evaporator to finally obtain a yellow methacrylate compound, and the synthesized material was confirmed through liquid chromatography (LC) analysis.

[Chemical Formula 2-1]

.

.

Manufacturing Example 2 (surfmer 2): Methacrylate compound represented by chemical formula 2-2 (Brij S2-methacrylate; HLB: 4.91)

20 mmol of Brij S2 (Mn 358.6 g/mol) is dissolved in 100 mL of dichloromethane (DCM), and 24 mmol of triethylamine (TEA) is added while stirring at 300 rpm under a nitrogen atmosphere. The flask containing the above solution is immersed in an ice bath, and when the temperature drops below 5°C, 22 mmol of methacryloyl chloride (MAC) dissolved in 50 mL of DCM is added using a syringe pump for 30 minutes. The speed of the syringe pump is 1.67 ml/min, and the temperature is maintained at 10°C or lower during the reaction time. The mixed solution is stirred at room temperature for 24 hours, and the subsequent process is the same as the surfmer 1 synthesis method.

[Chemical Formula 2-2]

Manufacturing Example 3 (surfmer 3): Methacrylate compound represented by chemical formula 2-3 (Brij 52-methacrylate; HLB: 5.33)

20 mmol of Brij 52 (Mn 330 g/mol) is dissolved in 100 mL of dichloromethane (DCM), and 24 mmol of triethylamine (TEA) is added while stirring at 300 rpm under a nitrogen atmosphere. The flask containing the above solution is immersed in an ice bath, and when the temperature drops below 5°C, 22 mmol of methacryloyl chloride (MAC) dissolved in 50 mL of DCM is added using a syringe pump for 30 minutes. The speed of the syringe pump is 1.67 ml/min, and the temperature is maintained at 10°C or lower during the reaction time. The mixed solution is stirred at room temperature for 24 hours, and the subsequent process is the same as the surfmer 1 synthesis method.

[Chemical Formula 2-3]

Manufacturing Example 4: Methacrylate compound represented by chemical formula 3 (Triton X-45 methacrylate; HLB: 9.8)

10 mmol of Triton X-45 (Mn 426.6 g/mol) is dissolved in 100 mL of dichloromethane (DCM), and 12 mmol of triethylamine (TEA) is added while stirring at 300 rpm under a nitrogen atmosphere. The flask containing the above solution is immersed in an ice bath, and when the temperature drops below 5°C, 10 mmol of methacryloyl chloride (MAC) dissolved in 50 mL of DCM is added using a syringe pump for 30 minutes. At this time, the speed of the syringe pump is 1.67 ml/min, and the temperature is maintained at 10°C or lower during the reaction time. The mixed solution is stirred at room temperature for 24 hours, and the subsequent process is the same as the surfmer 1 synthesis method.

[Chemical Formula 3]

Example 1

An acrylic acid aqueous solution having at least a portion of acidic groups neutralized was prepared by mixing 190 parts by weight of a sodium hydroxide (NaOH) aqueous solution having a degree of neutralization of 70% with 100 parts by weight of acrylic acid (hereinafter referred to as a “neutralized solution”).

In the neutralized aqueous solution above, 3.5 parts by weight of N', N'-methylenebis(acrylamide), an internal cross-linking agent, is dissolved, and then 1 part by weight of ammonium persulfate ((NH4)2S2O8), a thermal polymerization initiator, is added and mixed to prepare an aqueous dispersion solution.

Separately from the above-mentioned aqueous dispersion, 75 parts by weight of the compound of Manufacturing Example 1 was added to 3400 parts by weight of liquid paraffin and mixed to prepare a continuous oil (surfactant solution).

In a 1 L reactor equipped with a thermometer, a reflux condenser, a cooling chiller, and a stirrer, the aqueous solution of the dispersed phase and the oil of the continuous phase were mixed, each was purged with nitrogen for more than 10 minutes, and then stirred at high speed at a rotation speed of 500 rpm to form a pre-emulsion (reverse emulsion).

The internal temperature of the reactor was increased to 70°C, and the pre-emulsion (reverse emulsion) was polymerized for 18 hours while maintaining the temperature at 70°C.

After completion of the polymerization reaction, the reactor was cooled until the internal temperature reached room temperature, filtered to obtain solid particles, and washed three or more times using 500 g of n-hexane and 500 g of methanol to obtain superabsorbent resin particles of Example 1.

Example 2

In Example 2, 10 parts by weight of the compound of Preparation Example 1, 75 parts by weight of Span 80, and 25 parts by weight of Tween 80 were added to 3400 parts by weight of liquid paraffin and mixed to produce a continuous oil.

The continuous oil of Example 2 was used instead of the continuous oil of Example 1, and the remainder was the same as Example 1, thereby obtaining superabsorbent resin particles of Example 2.

Example 3

In Example 3, 75 parts by weight of the compound of Manufacturing Example 1, 75 parts by weight of Span 80, and 25 parts by weight of Tween 80 were added to 3400 parts by weight of liquid paraffin and mixed to produce a continuous oil.

Instead of the continuous oil of the above Example 1, the continuous oil of the above Example 3 was used, and the remainder was the same as in the above Example 1, to obtain superabsorbent resin particles of the above Example 3.

Example 4

In Example 4, 75 parts by weight of the compound of Manufacturing Example 2 was added to 3400 parts by weight of liquid paraffin and mixed to produce a continuous oil.

Instead of the continuous oil of the above Example 1, the continuous oil of the above Example 4 was used, and the remainder was the same as in the above Example 1, to obtain superabsorbent resin particles of the above Example 4.

Example 5

In Example 5, 10 parts by weight of the compound of Manufacturing Example 2 was added to 3400 parts by weight of liquid paraffin and mixed to produce a continuous oil.

Instead of the continuous oil of the above Example 1, the continuous oil of the above Example 5 was used, and the remainder was the same as in the above Example 1, to obtain superabsorbent resin particles of the above Example 5.

Example 6

In Example 6, 75 parts by weight of the compound of Preparation Example 3 was added to 3400 parts by weight of liquid paraffin and mixed to produce a continuous oil.

Instead of the continuous oil of the above Example 1, the continuous oil of the above Example 6 was used, and the remainder was the same as in the above Example 1, to obtain superabsorbent resin particles of the above Example 6.

Comparative Example 1

In Comparative Example 1, 3400 parts by weight of liquid paraffin was mixed with 75 parts by weight of Span 80 and 25 parts by weight of Tween 80 to produce a continuous oil.

Instead of the continuous oil of Example 1, the continuous oil of Comparative Example 1 was used, and the rest was the same as Example 1, to obtain absorbent particles of Comparative Example 1.

Comparative Example 2

In Comparative Example 2, 71 parts by weight of the compound of Manufacturing Example 1 and 29 parts by weight of the compound of Manufacturing Example 4 were added to 3400 parts by weight of liquid paraffin and mixed to produce a continuous oil.

Instead of the continuous oil of Example 1, the continuous oil of Comparative Example 2 was used, and the rest was the same as Example 1, but no particles were produced in Comparative Example 2.

Comparative Example 3

In Comparative Example 3, 200 parts by weight of the compound of Manufacturing Example 1 was added to 3400 parts by weight of liquid paraffin and mixed to prepare a continuous oil.

Instead of the continuous oil of Example 1, the continuous oil of Comparative Example 3 was used, and the rest was the same as Example 1, to obtain superabsorbent resin particles of Comparative Example 3.

Comparative Example 4

In Comparative Example 4, 50 parts by weight of the compound of Manufacturing Example 1 was added to 3400 parts by weight of liquid paraffin and mixed to produce a continuous oil.

Instead of the continuous oil of Example 1, the continuous oil of Comparative Example 4 was used, and the remainder was the same as Example 1, to obtain superabsorbent resin particles of Comparative Example 4.

The contents of each material used in the manufacturing processes of Examples 1 to 6 and Comparative Examples 1 to 4 are summarized in Table 1 below.

For reference, the hydrophilic balance (HLB) of the reactive surfactant solutions used in the manufacturing processes of Examples 1 to 6 and Comparative Examples 1 to 4 was obtained according to Equation 1 below, and when multiple surfactants were used together, it was obtained according to Equation 2 below, and recorded in Tables 1 and 2 below.

[Formula 1] HLB = 20 * (M _h /M)

M _h : molecular weight of hydrophilic groups

M : molecular weight of the whole molecule

[Formula 2] HLB _mix = {(C ₁ *HLB ₁ ) + (C ₂ *HLB ₂ ) + (C ₃ *HLB ₃ ) + … }/C _Total

C ₁ , C ₂ , C ₃ , … : component proportion, %

CTotal: total proportion, %

HLB ₁ , HLB ₂ , HLB ₃ , … ::HLB value for the component

Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Monomer Acrylic acid 100 weight parts Sodium hydroxide solution sodium hydroxide 39 weight parts (70% neutralization) water 150 weight parts Internal crosslinker MBA 3.5 weight parts Responsive
Surfactant Methacrylate compounds
(Chemical Formula 2-1) 75
Weight part 10
Weight part 75
Weight part - - - Methacrylate compounds
(Chemical Formula 2-2) - - - 75
Weight part 10
Weight part - Methacrylate compound (chemical formula 2-3) - - - - - 75
Weight part Methacrylate compounds
(chemical formula 3) - - - - - - Non-responsive
Surfactant Span 80 - 75
Weight part 75
Weight part - 75
Weight part - Tween 80 - 25
Weight part 25
Weight part - 25
Weight part - Surfactant solution
Hydrophilic Balance (HLB) 4.14 6.38 5.55 4.91 6.45 5.33 Thermal polymerization
Initiator APS 1 weight part Liquid paraffin 3400 weight parts

Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Monomer Acrylic acid 100 weight parts Sodium hydroxide solution sodium hydroxide 39 weight parts (70% neutralization) water 150 weight parts Internal crosslinker MBA 3.5 weight parts Responsive
Surfactant Methacrylate compounds
(Chemical Formula 2-1) - 71
Weight part 200
Weight part 50
Weight part Methacrylate compounds
(Chemical Formula 2-2) - - - - Methacrylate compound (chemical formula 2-3) - - - - Methacrylate compounds
(chemical formula 3) - 29
Weight part - - Non-responsive
Surfactant Span 80 75
Weight part 75
Weight part - - Tween 80 25
Weight part 25
Weight part - - Surfactant solution
Hydrophilic Balance (HLB) 6.6 5.52 4.14 4.14 Thermal polymerization
Initiator APS 1 weight part Liquid paraffin 3400 weight parts

In Table 1 above, MBA is N,N’-methylenebis(acrylamide) and APS is ammonium persulfate.

Test Example 1

The superabsorbent resin particles of Examples 1 to 6 and Comparative Examples 1 to 4 were evaluated in the following manner.

Particle size : After drying the superabsorbent resin particles in a vacuum oven at 60℃, the external surface images of the superabsorbent resin particles were taken using a FE-SEM (Field Emission Scanning Electron Microscope, product name: S-4800, manufacturer: Hitachi), and the size (diameter) was confirmed from the taken images.

FE-SEM images of the superabsorbent resin particles of Examples 1 to 6 and Comparative Examples 1 to 4 are shown in FIGS. 1 to 7, and the particle sizes (diameters) obtained therefrom are averaged and recorded in Table 2 below.

Particle Dispersion : Superabsorbent Resin Particles and By mixing n-hexane, A solution was prepared in which the content of superabsorbent resin particles was 5 wt% of the total solution (100 wt%). The time for the superabsorbent resin particles to settle in the solution was measured. As a result of the measurement, if it took 10 minutes or more for the superabsorbent resin particles to settle, it was evaluated as 'high', if it took 3 minutes or more but less than 10 minutes, it was evaluated as 'medium', and if it took 3 minutes or less, it was evaluated as 'low'.

The results of the dispersion evaluation for the superabsorbent resin particles of Examples 1 to 6 and Comparative Examples 1 to 4 are recorded in Tables 3 and 4 below.

Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Responsive
Surfactant Methacrylate compounds
(Chemical Formula 2-1) 75
Weight part 10
Weight part 75
Weight part - - - Methacrylate compounds
(Chemical Formula 2-2) - - - 75
Weight part 10
Weight part - Methacrylate compound (chemical formula 2-3) - - - - - 75
Weight part Methacrylate compounds
(chemical formula 3) - - - - - - Non-responsive
Surfactant Span 80 - 75
Weight part 75
Weight part - 75
Weight part - Tween 80 - 25
Weight part 25
Weight part - 25
Weight part - Surfactant solution
Hydrophilic Balance (HLB) 4.14 6.38 5.55 4.91 6.45 5.33 Particle diameter 0.3 ㎛ 1~3㎛ 0.5~3㎛ 0.5~2㎛ 1~5㎛ 0.5~3㎛ Dispersion award middle under award middle middle

Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Responsive
Surfactant Methacrylate compounds
(Chemical Formula 2-1) - 71
Weight part 200
Weight part 50
Weight part Methacrylate compounds
(Chemical Formula 2-2) - - - - Methacrylate compound (chemical formula 2-3) - - - - Methacrylate compounds
(chemical formula 3) - 29
Weight part - - Non-responsive
Surfactant Span 80 75
Weight part 75
Weight part - - Tween 80 25
Weight part 25
Weight part - - Surfactant solution
Hydrophilic Balance (HLB) 6.6 5.52 4.14 4.14 Particle diameter 10~40 ㎛ 5~50 ㎛
(Atypical) 50 ㎛ or more
(Atypical) 10~40 ㎛ Dispersion under under under under

According to FIGS. 1 to 6 and Tables 3 and 4 above, the superabsorbent resin particles of Examples 1 to 6 were confirmed to have a uniform particle size and suppressed agglomeration between particles, compared to Comparative Examples 1 to 4.

In Comparative Example 1, a mixture of two non-reactive surfactants widely used in the art was used, and superabsorbent resin particles with a large particle size deviation of 5 to 50 ㎛ were obtained.

Here, it is inferred that the two non-reactive surfactants form a structurally stable interface depending on the mixing ratio at a low temperature for forming an emulsion, but under high temperature conditions for polymerization, the degree of freedom increases, so that the interface adsorption stability decreases and the surfactant function is lost, resulting in the production of superabsorbent resin particles with a large deviation in particle size. The superabsorbent resin particles of Comparative Example 1 are amorphous and have almost no dispersibility in organic solvents.

Accordingly, there is a need for a surfactant that replaces two types of non-reactive surfactants widely used in the art.

In the above Comparative Example 2, a mixture of a methacrylate compound represented by the chemical formula 2 (specifically, chemical formula 2-1) and a methacrylate compound represented by the chemical formula 3 was used to manufacture superabsorbent resin particles, but the particles themselves were not formed.

This is inferred to be the result of the aggregation of methacrylate compounds represented by the chemical formula 3 due to π(pi)-π(pi) interaction, van der Waals attraction, etc., and thus their inability to participate in the polymerization reaction.

Accordingly, it is necessary to avoid a reactive surfactant containing an aromatic ring in the molecule as in the chemical formula 3 above.

In contrast, in Examples 1 to 6, when 60 to 190 parts by weight of a methacrylate compound represented by the chemical formula 2 (specifically, any one of the chemical formulas 2-1 to 2-3) alone or a mixture thereof with a non-reactive surfactant was used, superabsorbent resin particles having a relatively uniform particle size were produced.

The HLB value of a surfactant solution containing a methacrylate compound represented by the above chemical formula 2 (specifically, any one of chemical formulas 2-1 to 2-3) is within a range of 4 to 6.5, and the ratio of (the number of carbon atoms in the alkyl chain (R))/n is within a range of 8 to 10, making it suitable for reverse emulsion polymerization.

In particular, the alkyl chain of the methacrylate compound represented by the chemical formula 2 (specifically, any one of chemical formulas 2-1 to 2-3) is introduced to the outer surface of the superabsorbent resin particle to modify the surface to be hydrophobic and contribute to improving the dispersibility of the superabsorbent resin particle.

Such an effect can also be achieved when a mixture of two non-reactive surfactants widely used in the art is mixed with a methacrylate compound represented by the chemical formula 2.

However, when the amount of the methacrylate compound represented by the chemical formula 2 (specifically, chemical formula 2-1) increases as in Comparative Example 3, a clumping phenomenon may occur between emulsions due to the attractive force between the alkyl chains. In addition, in the case of Comparative Example 4, although spherical superabsorbent particles were produced using the methacrylate compound represented by the chemical formula 2 (specifically, chemical formula 2-1), the amount used was small, so the particle size was produced relatively large and the dispersibility in the organic solvent may be reduced.

Meanwhile, when the amount of non-reactive surfactant mixed increases as in Comparative Example 2, some agglomeration occurs between the surfactants, which broadens the particle size distribution and makes it difficult for the methacrylate compound represented by the chemical formula 2-1 to be introduced to the surface of each particle, which may result in some reduction in dispersibility.

Accordingly, in order to increase the uniformity of particle size and improve dispersibility, it is necessary to use, as in Examples 1 to 6, a methacrylate compound represented by the chemical formula 2 alone; or a mixture thereof with a non-reactive surfactant; in an amount of 60 to 190 parts by weight.

Claims (20)

A crosslinked polymer of an acrylic acid monomer having an acid group and at least a portion of the acid group being neutralized; and
A compound comprising a surface functional group of the above cross-linked polymer and represented by the following chemical formula 1;
Superabsorbent resin particles:
[Chemical Formula 1]

In the above chemical formula,
n is an integer from 1 to 10,
R is substituted or unsubstituted C _10-30 alkyl,
The dotted line indicates bonding with the surface functional group of the cross-linked polymer.
In the first paragraph,
The above superabsorbent resin particles are,
In the presence of a compound represented by the following chemical formula 2, an acrylic acid-based monomer having an acidic group and at least a portion of the acidic group being neutralized is reverse-emulsion polymerized.
Superabsorbent resin particles:
[Chemical formula 2]

In the above chemical formula 2,
n is an integer from 1 to 10,
R is substituted or unsubstituted C _10-30 alkyl.
In the second paragraph,
The above superabsorbent resin particles are,
In the presence of a compound represented by the above chemical formula 2 alone; or a mixture of a compound represented by the above chemical formula 2 and a non-reactive surfactant; an acrylic acid-based monomer having an acidic group and at least a portion of the acidic group being neutralized is reverse-emulsified.
Superabsorbent resin particles.
In the first paragraph,
The size of the above superabsorbent resin particles is
0.1 to 20 ㎛,
Superabsorbent resin particles.
organic solvent; and
Comprising the superabsorbent resin particles of claim 1 dispersed in the organic solvent;
Superabsorbent resin composition.
A step of preparing a monomer mixture comprising an acrylic acid-based monomer having an acidic group and at least a portion of the acidic group being neutralized, a polymerization initiator, and an internal cross-linking agent;
A step for preparing a surfactant solution containing 60 to 190 parts by weight of a compound represented by the following chemical formula 2 alone; or a mixture of a compound represented by the following chemical formula 2 and a non-reactive surfactant; based on 100 parts by weight of the above monomer;
A step of forming a pre-emulsion by mixing the above surfactant solution with the above monomer mixture; and
A step of polymerizing a monomer mixture in the above pre-emulsion to obtain a composition including superabsorbent resin particles; comprising;
Method for producing superabsorbent resin particles:
[Chemical formula 2]

In the above chemical formula 2,
n is an integer from 1 to 10,
R is substituted or unsubstituted C _10-30 alkyl.
In Article 6,
The compound represented by the above chemical formula 2 is
HLB (Hydrophile-Lipophile Balance) value is 1 to 8,
A method for producing superabsorbent resin particles.
In Article 6,
The compound represented by the above chemical formula 2 is
(Carbon number of R)/n is 2 to 10,
A method for producing superabsorbent resin particles.
In Article 6,
The above surfactant solution is, based on 100 parts by weight of the above monomer,
A compound represented by the chemical formula 2 alone; or a mixture of a compound represented by the chemical formula 2 and a non-reactive surfactant; containing 60 to 190 parts by weight,
Containing 3000 to 4000 parts by weight of liquid paraffin,
A method for producing superabsorbent resin particles.
In Article 6,
A step of forming a pre-emulsion by mixing a surfactant solution containing a compound represented by the above chemical formula 2 with the above monomer mixture; before,
It further comprises a step of preparing a compound represented by the chemical formula 2.
A method for producing superabsorbent resin particles.
In Article 10,
The step of preparing the compound represented by the above chemical formula 2 is a step of preparing the compound represented by the above chemical formula 2 by reacting the compound represented by the following chemical formula 2-1-1 with methacryloyl chloride.
Method for producing superabsorbent resin particles:
[Chemical Formula 2-1-1]

In the above chemical formula 2-1-1,
n is an integer from 1 to 10,
R is substituted or unsubstituted C _10-30 alkyl.
In Article 11,
The step of preparing the compound represented by the chemical formula 2 by reacting the compound represented by the chemical formula 2-1-1 with meth(acryloyl) chloride is performed in the presence of triethylamine (TEA) and dichloromethane (DCM).
A method for producing superabsorbent resin particles.
In Article 6,
The above non-reactive surfactant is,
At least one selected from the group consisting of alcohols, alkanes, mercaptans, carboxylic acids, ketones, amines, and nonionic surfactants having an HLB (Hydrophile-Lipophile Balance) value of 11 or less, having 10 to 40 carbon atoms.
A method for producing superabsorbent resin particles.
In Article 6,
The above non-reactive surfactant is,
A mixture in which sorbitan monooleate and polyoxyethylene sorbitan monooleate are mixed in a weight ratio of 5:1 to 1:5,
A method for producing superabsorbent resin particles.
In Article 6,
The above surfactant solution is,
A solution composed of 60 to 90 parts by weight of the compound represented by the chemical formula 2 and 3,000 to 4,000 parts by weight of liquid paraffin, based on 100 parts by weight of the monomer;
A solution comprising 1 to 90 parts by weight of a compound represented by the chemical formula 2, 60 to 90 parts by weight of sorbitan monooleate, 10 to 40 parts by weight of polyoxyethylene sorbitan monooleate, and 3,000 to 4,000 parts by weight of liquid paraffin, based on 100 parts by weight of the monomer, wherein the mixture of the compound represented by the chemical formula 2 and the non-reactive surfactant is in a total range of 60 to 190 parts by weight.
A method for producing superabsorbent resin particles.
In Article 6,
The above internal cross-linking agent is,
Based on 100 parts by weight of the above monomer, 3 to 4 parts by weight are used.
A method for producing superabsorbent resin particles.
In Article 6,
The above polymerization initiator
Based on 100 parts by weight of the above acrylic acid monomer, 0.1 to 10 parts by weight is used.
A method for producing superabsorbent resin particles.
In Article 6,
In the step of forming the above pre-emulsion;
The surfactant solution is mixed with the monomer mixture and stirred at a rotation speed of 300 to 800 rpm.
A method for producing superabsorbent resin particles.
In Article 6,
Polymerization of the monomer mixture in the above pre-emulsion is
It is performed at 50 to 90 ℃,
A method for producing superabsorbent resin particles.
In Article 6,
A step of obtaining a composition comprising the above superabsorbent resin particles; thereafter,
A step of separating a liquid from a composition containing the superabsorbent resin particles and recovering the superabsorbent resin particles;
A step of washing the recovered superabsorbent resin particles; and
A step of drying the washed superabsorbent resin particles is further included.
A method for producing superabsorbent resin particles.