阅读说明：本技术 超吸收性聚合物组合物以及用于制备其的方法 (Superabsorbent polymer composition and method for making the same ) 是由 李琗俄 金起贤 金琪哲 金泰润 于 2020-07-21 设计创作，主要内容包括：本公开内容涉及超吸收性聚合物组合物以及用于制备其的方法。更具体地,根据本公开内容的超吸收性聚合物组合物以及用于制备其的方法,可以提供具有改善的抗结块效率而不使吸收性能劣化的超吸收性聚合物组合物。(The present disclosure relates to superabsorbent polymer compositions and methods for making the same. More specifically, according to the superabsorbent polymer composition of the present disclosure and the method for preparing the same, a superabsorbent polymer composition having improved anti-blocking efficiency without deteriorating absorption performance can be provided.)

1. A superabsorbent polymer composition comprising:

superabsorbent polymer particles comprising a crosslinked polymer of a water-soluble ethylenically unsaturated monomer having at least partially neutralized acidic groups;

a first hydrophobic material; and

a second hydrophobic material that is a hydrophobic material,

wherein the first hydrophobic material includes a carboxylic acid represented by the following chemical formula 1 or a salt thereof, and

the second hydrophobic material includes a carboxylic acid represented by the following chemical formula 2 or a salt thereof:

[ chemical formula 1]

In the chemical formula 1, the first and second organic solvents,

x is an integer of 10 to 20,

[ chemical formula 2]

In the chemical formula 2,

y is an integer of 5 to 15, and

z is an integer from 1 to 10.

2. The superabsorbent polymer composition of claim 1,

wherein at least a portion of the first hydrophobic material and the second hydrophobic material are present on the surface of the superabsorbent polymer particles.

3. The superabsorbent polymer composition of claim 1,

wherein x is an integer of 11 to 15,

y is 11, and

z is an integer of 5 to 10.

4. The superabsorbent polymer composition of claim 1,

wherein the first hydrophobic material is in a solid phase at 25 ℃, and

the second hydrophobic material is in a liquid phase at 25 ℃.

5. The superabsorbent polymer composition of claim 1,

wherein the first hydrophobic material and the second hydrophobic material are included in a molar ratio of 3:7 to 7: 3.

6. The superabsorbent polymer composition of claim 1,

further comprising a surface cross-linked layer formed by additionally cross-linking the cross-linked polymer by a surface cross-linking agent on at least a part of the surface of the superabsorbent polymer particles.

7. The superabsorbent polymer composition of claim 1,

wherein the anti-blocking (A/C) efficiency of the superabsorbent polymer composition, calculated by the following numerical formula 3, is 20% or more, an

The wetting time, defined as the total time for which unwetted superabsorbent polymer composition was observed on top of the liquid while 2g of the superabsorbent polymer composition was placed in 50mL of a saline solution at 23 ℃ to 24 ℃ and stirred at 600rpm with a magnetic bar (8 mm diameter, 30mm length), was 15 seconds or less:

[ mathematical formula 3]

A/C(％)＝W₆/W₅×100

In the above-mentioned mathematical formula 3,

W₅is the weight (g) of the superabsorbent polymer composition applied to a culture dish having a diameter of 10cm, and

W₆to uniformly apply the superabsorbent polymer composition on a culture dish having a diameter of 10cm, the superabsorbent polymer composition was maintained in a constant temperature and humidity chamber having a temperature of 40 ℃. + -. 3 ℃ and a humidity of 80%. + -. 3% for 10 minutes, and then the weight (g) of the superabsorbent polymer composition dropped from the culture dish after inverting the culture dish on a filter paper and tapping 3 times.

8. A method for preparing a superabsorbent polymer composition comprising:

performing a cross-linking polymerization of a water-soluble ethylenically unsaturated monomer having at least partially neutralized acidic groups in the presence of an internal cross-linking agent and a polymerization initiator to form a hydrogel polymer;

introducing and grinding a hydrophobic composition comprising a first hydrophobic material and a second hydrophobic material into the hydrogel polymer to produce a ground product comprising wet superabsorbent polymer particles and the hydrophobic composition; and

drying the ground product to produce a superabsorbent polymer composition comprising superabsorbent polymer particles, the first hydrophobic material, and the second hydrophobic material,

wherein the first hydrophobic material includes a carboxylic acid represented by the following chemical formula 1 or a salt thereof, and

the second hydrophobic material includes a carboxylic acid represented by the following chemical formula 2 or a salt thereof:

[ chemical formula 1]

In the chemical formula 1, the first and second organic solvents,

x is an integer of 10 to 20,

[ chemical formula 2]

In the chemical formula 2,

y is an integer of 5 to 15, and

z is an integer from 1 to 10.

9. The method for preparing a superabsorbent polymer composition of claim 8,

wherein the hydrogel polymer has a water content of 30 to 70 wt.%.

10. The method for preparing a superabsorbent polymer composition of claim 8,

wherein the total weight of the first hydrophobic material and the second hydrophobic material is 0.01 parts by weight to 1 part by weight based on 100 parts by weight of the hydrogel polymer.

11. The method for preparing a superabsorbent polymer composition of claim 8,

wherein the hydrophobic composition further comprises water.

12. The method for preparing a superabsorbent polymer composition of claim 8,

wherein the grinding process is performed by a chopper.

13. The method for preparing a superabsorbent polymer composition of claim 8,

wherein the particle size of the superabsorbent polymer particles is from 300 μm to 5000 μm.

14. The method for preparing a superabsorbent polymer composition of claim 8,

wherein in the milled product at least a portion of the first hydrophobic material and the second hydrophobic material are present on the surface of the wet superabsorbent polymer particles.

15. The method for preparing a superabsorbent polymer composition of claim 8,

further comprising: forming a surface cross-linked layer on at least a portion of the surface of the superabsorbent polymer particles in the presence of a surface cross-linking agent.

Technical Field

Cross Reference to Related Applications

This application claims the benefits of korean patent application No. 10-2019-0120645, filed on 30.9.2019 and korean patent application No. 10-2020 0087106, filed on 14.7.2020 and incorporated herein by reference in its entirety.

The present disclosure relates to superabsorbent polymer compositions and methods for making the same. More particularly, the present disclosure relates to superabsorbent polymer compositions having improved anti-caking efficiency without deterioration of absorption properties, and methods for making the same.

Background

Superabsorbent polymers (SAP) are synthetic polymer materials that can absorb moisture 500 to 1000 times their own weight, and are also variously named superabsorbent materials (SAM), Absorbent Gel Materials (AGM), etc. according to development companies. Superabsorbent polymers are starting to be commercialized as sanitary products, and at present, they are widely used as water retention materials for soil, water stop materials for civil engineering and construction, sheets for growing seedlings, freshness keeping agents in the field of food distribution, dressing materials, and the like.

Such superabsorbent polymers are widely used in the field of sanitary goods such as diapers or sanitary napkins and the like. In sanitary goods, superabsorbent polymers are typically included while distributed in the slurry. However, recently, there have been continuous efforts to provide sanitary articles such as diapers having a thinner thickness, and as a part of this, development of diapers having a reduced content of size, or pulp-free diapers in which size is not used at all, is being actively conducted.

Therefore, in a hygienic article or a pulp-free hygienic article having a reduced content of pulp, superabsorbent polymer is contained at a relatively high ratio, and thus superabsorbent polymer particles are inevitably contained in multiple layers in the hygienic article. The superabsorbent polymers should exhibit high absorption properties so that all the superabsorbent polymer particles contained in the plurality of layers can more effectively absorb a large amount of liquid, such as urine or the like.

Meanwhile, the superabsorbent polymer contains many hydrophilic portions on the surface so as to exhibit high absorbency for liquid, particularly water, and due to such hydrophilic portions, when exposed to air, it absorbs moisture contained in the air, thus generating aggregation and agglomeration between the superabsorbent polymer particles.

Therefore, in order to prevent aggregation and caking between superabsorbent polymer particles, it has been considered to add an anti-caking agent, but when the anti-caking agent is used, the absorption properties of the superabsorbent polymer deteriorate.

Accordingly, there is a continuing need to develop superabsorbent polymer technology that can prevent agglomeration between superabsorbent polymer particles without degrading absorption performance.

Disclosure of Invention

Technical problem

It is an object of the present disclosure to provide a superabsorbent polymer composition having improved anti-caking efficiency without deteriorating absorption properties by simultaneously comprising a first hydrophobic material and a second hydrophobic material of a specific structure.

It is another object of the present disclosure to provide a method for preparing a superabsorbent polymer composition, in which a hydrogel polymer is prepared and then ground together with a hydrophobic composition, thereby imparting hydrophobicity to at least a portion of the surface of the prepared superabsorbent polymer particles, thereby preventing agglomeration, and two hydrophobic materials having different hydrophobic characteristics are included in the hydrophobic composition, thereby preventing deterioration of absorption properties.

Technical scheme

To achieve the object, there is provided a superabsorbent polymer composition comprising:

superabsorbent polymer particles comprising a crosslinked polymer of a water-soluble ethylenically unsaturated monomer having at least partially neutralized acidic groups;

a first hydrophobic material; and

a second hydrophobic material.

Wherein the first hydrophobic material includes a carboxylic acid represented by the following chemical formula 1 or a salt thereof, and the second hydrophobic material includes a carboxylic acid represented by the following chemical formula 2 or a salt thereof:

[ chemical formula 1]

In the chemical formula 1, the first and second,

x is an integer of 10 to 20,

[ chemical formula 2]

In the chemical formula 2, the first and second organic solvents,

y is an integer of 5 to 15, and

z is an integer from 1 to 10.

Further, a method for preparing a superabsorbent polymer composition is provided, comprising the steps of:

performing a cross-linking polymerization of a water-soluble ethylenically unsaturated monomer having at least partially neutralized acidic groups in the presence of an internal cross-linking agent and a polymerization initiator to form a hydrogel polymer;

introducing and grinding a hydrophobic composition comprising a first hydrophobic material and a second hydrophobic material into a hydrogel polymer to produce a ground product comprising wet superabsorbent polymer particles and the hydrophobic composition; and

drying the ground product to produce a superabsorbent polymer composition comprising superabsorbent polymer particles, a first hydrophobic material, and a second hydrophobic material.

Advantageous effects

The superabsorbent polymer composition according to the present disclosure can improve anti-caking efficiency without deteriorating absorption performance.

Further, according to the method of preparing a superabsorbent polymer of the present disclosure, when a hydrogel polymer is ground while introducing a hydrophobic composition including two hydrophobic materials having different hydrophobic characteristics, no agglomeration occurs between the prepared superabsorbent polymer particles, and thus agglomeration can be prevented even under a high temperature and humidity environment.

Detailed Description

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. The singular forms "a", "an" and "the" include plural referents unless the content clearly dictates otherwise or is clear from the context. As used herein, the terms "comprising," "including," or "having," etc., are intended to mean that there are practical features, numbers, steps, elements, or combinations thereof, and they are not intended to preclude the possibility of one or more other features, numbers, steps, elements, or combinations thereof, being present or added.

While the present disclosure is susceptible to various modifications and alternative forms, specific examples will be shown and described in detail below. It should be understood, however, that these are not intended to limit the present disclosure to the particular disclosure, and that the present disclosure includes all modifications, equivalents, and alternatives thereof without departing from the spirit and technical scope of the present disclosure.

While the present disclosure is susceptible to various modifications and alternative forms, specific examples will be shown and described in detail below. It should be understood, however, that these are not intended to limit the present disclosure to the particular disclosure, and that the present disclosure includes all modifications, equivalents, and alternatives thereof without departing from the spirit and technical scope of the present disclosure.

Hereinafter, a method for preparing a superabsorbent polymer and a superabsorbent polymer according to embodiments of the present disclosure will be described in detail.

First, technical terms in the present specification are used only to refer to specific embodiments, and they are not intended to limit the present disclosure unless they are specifically mentioned. Furthermore, as used herein, the singular may include the plural unless explicitly stated or otherwise clear from the context.

According to one embodiment of the present invention, there is provided a superabsorbent polymer composition comprising: superabsorbent polymer particles comprising a crosslinked polymer of a water-soluble ethylenically unsaturated monomer having at least partially neutralized acidic groups; a first hydrophobic material; and a second hydrophobic material.

Wherein the first hydrophobic material includes a carboxylic acid represented by the following chemical formula 1 or a salt thereof, and the second hydrophobic material includes a carboxylic acid represented by the following chemical formula 2 or a salt thereof:

[ chemical formula 1]

In the chemical formula 1, the first and second,

x is an integer of 10 to 20,

[ chemical formula 2]

In the chemical formula 2, the first and second organic solvents,

y is an integer of 5 to 15, and

z is an integer from 1 to 10.

According to another embodiment of the present invention, there is provided a method for preparing a superabsorbent polymer composition, comprising the steps of: performing a cross-linking polymerization of a water-soluble ethylenically unsaturated monomer having at least partially neutralized acidic groups in the presence of an internal cross-linking agent and a polymerization initiator to form a hydrogel polymer; introducing and grinding a hydrophobic composition comprising a first hydrophobic material and a second hydrophobic material into a hydrogel polymer to produce a ground product comprising wet superabsorbent polymer particles and the hydrophobic composition; and drying the ground product to produce a superabsorbent polymer composition comprising superabsorbent polymer particles, a first hydrophobic material, and a second hydrophobic material.

As used herein, the term "polymer" means the polymerized state of water-soluble ethylenically unsaturated monomers, and may include polymers of any range of water content or particle size. Among polymers, a polymer having a water content of about 30% by weight or more before drying may be referred to as a hydrogel polymer, and ground and dried particles of such a hydrogel polymer may be referred to as a crosslinked polymer.

Furthermore, the term "superabsorbent polymer particles" refers to particulate material comprising a crosslinked polymer polymerized from a water-soluble ethylenically unsaturated monomer containing at least partially neutralized acidic groups and crosslinked by an internal crosslinking agent.

Further, the term "superabsorbent polymer particles" means, depending on the context, a crosslinked polymer of water-soluble ethylenically unsaturated monomers containing at least partially neutralized acidic groups, or a base polymer in powder form composed of superabsorbent polymer particles formed by grinding the crosslinked polymer, or its use including making the crosslinked polymer or base polymer suitable for being manufactured for commercialized by additional processes (e.g., surface crosslinking, fine particle reassembly, drying, grinding, sieving, etc.). Thus, the term "superabsorbent polymer" may be construed to include compositions comprising superabsorbent polymer, i.e., composite superabsorbent polymer particles.

In general, a superabsorbent polymer, which is a crosslinked polymer prepared by polymerization of a water-soluble ethylenically unsaturated monomer in the presence of an internal crosslinking agent, has a hydrophilic surface due to remaining unpolymerized acidic groups (-COOH) and/or neutralized acidic groups (-COO-). The superabsorbent polymer absorbs moisture in the air during exposure to the air due to the hydrophilicity of the surface, and thus, capillary force, hydrogen bonding, inter-particle diffusion, or van der waals force, etc. between particles are generated by water existing between particles of the superabsorbent polymer, and irreversible aggregation between particles is generated. In addition, water must be used during the process of preparing the superabsorbent polymer, but an additional grinding process is required due to aggregation between particles during the process.

Accordingly, the inventors determined that in the case where two hydrophobic materials having different hydrophobic characteristics are added after the hydrogel polymer is prepared and ground together, hydrophobicity may be imparted to a portion of the surface of the prepared superabsorbent polymer particles, thereby preventing agglomeration, and deterioration of absorption performance may be prevented due to the hydrophobic materials exhibiting different hydrophobic characteristics, and completed the present disclosure.

Specifically, both the first hydrophobic material represented by chemical formula 1 and the second hydrophobic material represented by chemical formula 2 have both a hydrophobic functional group through a linear alkyl group and a hydrophilic functional group through a carboxyl group. Therefore, in the case of grinding them together with the hydrogel polymer, the hydrophilic functional groups of the hydrophobic material are adsorbed to the hydrophilic portions present on the surface of the superabsorbent polymer particles, and the surface of the particles adsorbed with the hydrophobic material exhibits hydrophobicity due to the linear alkyl groups of the hydrophobic material. Therefore, even if the superabsorbent polymer is exposed to air, a portion of the superabsorbent polymer particles exhibit hydrophobicity, so that irreversible aggregation between the particles can be suppressed.

Further, unlike the first hydrophobic material, the second hydrophobic material further includes one or more ethylene oxide linking groups between the linear alkyl groups and the carboxyl groups present at both ends, and thus exhibits lower hydrophobicity than the first hydrophobic material. Accordingly, in the case where the first hydrophobic material and the second hydrophobic material are used together during the preparation of the superabsorbent polymer, it is possible to prepare a superabsorbent polymer having improved anti-blocking efficiency without deteriorating absorption properties. In contrast, if the first hydrophobic material is used alone, absorption performance may be deteriorated due to strong hydrophobicity, and if the second hydrophobic material is used alone, anti-blocking may not be effectively achieved.

Superabsorbent polymer composition

Hereinafter, one embodiment of the superabsorbent polymer composition will be described in detail according to components.

The superabsorbent polymer composition of one embodiment comprises: superabsorbent polymer particles comprising a crosslinked polymer of water-soluble ethylenically unsaturated monomers having at least partially neutralized acidic groups. Wherein the crosslinked polymer is formed by crosslinking-polymerizing a water-soluble ethylenically unsaturated monomer having an at least partially neutralized acidic group in the presence of an internal crosslinking agent, and has a three-dimensional network structure in which a main chain formed by polymerization of the monomer is crosslinked by the internal crosslinking agent.

The water-soluble ethylenically unsaturated monomer can be any of the monomers commonly used in the preparation of superabsorbent polymers. As a non-limiting example, the water-soluble ethylenically unsaturated monomer may be a compound represented by the following chemical formula 2:

[ chemical formula 2]

R₁-COOM₂

In the chemical formula 2, the first and second organic solvents,

R₁is a C2 to C5 hydrocarbon group containing an unsaturated bond,

M₂is a hydrogen atom, a monovalent or divalent metal, an ammonium group or an organic amine salt.

Preferably, the monomer may be one or more selected from the group consisting of: (meth) acrylic acid and monovalent (alkali) metal salts, divalent metal salts, ammonium salts and organic amine salts thereof.

The use of (meth) acrylic acid or a salt thereof as the water-soluble ethylenically unsaturated monomer is advantageous in that a superabsorbent polymer having improved absorption characteristics can be obtained. Furthermore, as monomers, one or more selected from the following may be used: maleic anhydride, fumaric acid, crotonic acid, itaconic acid, 2-acryloylethanesulfonic acid, 2-methacryloylethanesulfonic acid, 2- (meth) acryloylpropanesulfonic acid, 2- (meth) acrylamide-2-methylpropanesulfonic 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, or (N, N) -dimethylaminopropyl (meth) acrylamide, and the like.

Wherein the water-soluble ethylenically unsaturated monomer may have an acid group, and at least a part of the acid group may be neutralized. Specifically, at least part of the acid groups of the water-soluble ethylenically unsaturated monomer may be neutralized in the step of mixing the water-soluble ethylenically unsaturated monomer having acid groups, the internal crosslinking agent, the polymerization initiator, and the neutralizing agent. Among them, as the neutralizing agent, basic materials capable of neutralizing an acidic group, such as sodium hydroxide, potassium hydroxide, ammonium hydroxide, and the like, can be used.

Further, the degree of neutralization of the water-soluble ethylenically unsaturated monomer (which means the degree of neutralization of the acidic group contained in the water-soluble ethylenically unsaturated monomer by a neutralizing agent) may be 50 to 90 mol%, or 60 to 85 mol%, or 65 to 75 mol%. Although the range of the neutralization degree may vary depending on the final characteristics, if the neutralization degree is too high, the neutralized monomer may precipitate, thereby making smooth progress of polymerization difficult, and conversely, if the neutralization degree is too low, the absorption of the polymer may be significantly reduced, and the polymer may exhibit rubber-like characteristics that are difficult to handle.

Further, the term "internal crosslinking agent" is used herein to distinguish from a surface crosslinking agent for surface crosslinking of superabsorbent polymer particles as described below, and to crosslink unsaturated bonds of the above-mentioned water-soluble ethylenically unsaturated monomer to polymerize. In this step, crosslinking is performed without distinguishing between the surface and the inside, but in the case of performing a surface crosslinking process of the superabsorbent polymer particles as described below, the surface of the finally prepared superabsorbent polymer particles is composed of a structure crosslinked by a surface crosslinking agent, and the inside is composed of a structure crosslinked by an internal crosslinking agent.

As the internal crosslinking agent, any compound may be used as long as it can introduce crosslinking during polymerization of the water-soluble ethylenically unsaturated monomer. As non-limiting examples, as the internal crosslinking agent, a polyfunctional crosslinking agent such as N, N' -methylenebisacrylamide, trimethylolpropane tri (meth) acrylate, ethylene glycol di (meth) acrylate, polyethylene glycol (meth) acrylate, propylene glycol di (meth) acrylate, polypropylene glycol (meth) acrylate, butane glycol di (meth) acrylate, butanediol 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, glycerol tri (meth) acrylate, pentaerythritol tetraacrylate, triarylamine, ethylene glycol diglycidyl ether, propylene glycol di (meth) acrylate, butylene glycol di (meth) acrylate, Propylene glycol, glycerin, or ethylene carbonate, but it is not limited thereto. Preferably, among them, ethylene glycol diglycidyl ether may be used.

Crosslinking of the water-soluble ethylenically unsaturated monomer in the presence of such an internal crosslinking agent may be carried out by thermal polymerization, photopolymerization, or hybrid polymerization in the presence of a thickener, a plasticizer, a storage stabilizer, an antioxidant, or the like, as needed, which will be described in detail later.

Such superabsorbent polymer particles may have a particle size of from about 150 μm to about 850 μm and may be measured according to the EDANA standard of the European Disposables and nowovins Association, European Disposables and nonwoven Association, WSP 220.3.

Further, the superabsorbent polymer composition includes a first hydrophobic material represented by chemical formula 1 and a second hydrophobic material represented by chemical formula 2 in addition to the superabsorbent polymer particles. As described above, the first hydrophobic material and the second hydrophobic material may be mixed in during the grinding process of the hydrogel polymer after polymerization, not during the polymerization process, and uniformly cover the surface of the superabsorbent polymer particles.

The first hydrophobic material includes a carboxylic acid represented by the following chemical formula 1 or a salt thereof. In addition, the first hydrophobic material may be carboxylic acid represented by the following chemical formula 1 or a salt thereof.

In chemical formula 1, the moiety exhibiting hydrophobicity is a linear alkyl group having a carbon number of x +2, wherein if x is less than 10, sufficient hydrophobicity may not be imparted to the surface of the superabsorbent polymer particles, and if x is greater than 20, the molecular length of the material may be too long and may not be effectively coated on the hydrogel polymer. More specifically, x may be 11 or greater, 13 or greater, or 14 or greater, and 18 or less, 17 or less, or 16 or less. For example, x may be an integer of 11 to 15.

Further, the first hydrophobic material includes a salt of the carboxylic acid represented by chemical formula 1 in addition to the carboxylic acid represented by chemical formula 1, wherein the carboxylic acid salt may be a monovalent metal salt, a divalent metal salt, or an ammonium salt, in particular. More specifically, the carboxylate may be an alkali metal salt, such as a sodium or potassium salt.

As the first hydrophobic material, stearic acid, myristic acid, palmitic acid, or alkali metal salts thereof may be used.

Meanwhile, in chemical formula 2, the portion exhibiting hydrophobicity is a linear alkyl group having a carbon number of y +1, wherein if y is less than 5, sufficient hydrophobicity may not be imparted to the surface of the superabsorbent polymer particles as in the first hydrophobic material, and if y is greater than 15, the molecular length of the material may be too long and may not be effectively coated on the hydrogel polymer. More specifically, y may be 9 or more, 10 or more, and 13 or less, 12 or less. For example, y may be 11.

Further, if z, which means the number of ethylene oxide connecting groups of chemical formula 2, is 0, the hydrophobic property may not be different from the first hydrophobic material, and thus, the absorption speed of the superabsorbent polymer may be deteriorated, and if z is greater than 11, it may be difficult to impart the hydrophobic property to the superabsorbent polymer, and thus, it may be difficult to suppress agglomeration between particles. More specifically, z can be 2 or greater, 3 or greater, or 4 or greater, and 10 or less. For example, z may be an integer from 5 to 10.

Wherein the second hydrophobic material includes a salt of the carboxylic acid represented by chemical formula 2 in addition to the carboxylic acid represented by chemical formula 2, and with respect to the description of the salt, reference may be made to the description with respect to the first hydrophobic material.

As the second hydrophobic material, laureth-6-carboxylic acid, laureth-7-carboxylic acid, laureth-8-carboxylic acid, laureth-9-carboxylic acid, laureth-10-carboxylic acid, laureth-11-carboxylic acid or an alkali metal salt thereof may be used.

Further, the first hydrophobic material may be a solid phase at 25 ℃. That is, the first hydrophobic material may have a melting point above 25 ℃, and thus, may be solid at room temperature. Further, the second hydrophobic material may be in a liquid phase at 25 ℃. That is, the second hydrophobic material may have a melting point below 25 ℃, and thus, may be liquid at room temperature.

Wherein the total weight of the first hydrophobic material and the second hydrophobic material may be 0.01 parts by weight to 1.0 parts by weight based on 100 parts by weight of the superabsorbent polymer particles. If the total weight of the hydrophobic material in the composition is too low, the effect of the hydrophobic material to impart hydrophobicity may be insufficient, and thus it may be difficult to suppress caking, while if the total weight of the hydrophobic material is too high, the centrifuge retention capacity and the absorption rate under pressure of the superabsorbent polymer may be deteriorated.

Further, the first hydrophobic material and the second hydrophobic material may be included in a molar ratio of 3:7 to 7: 3. If the molar ratio of the first hydrophobic material is too high, the absorption rate of the superabsorbent polymer may be deteriorated, and if the molar ratio of the second hydrophobic material is too high, the effect of imparting hydrophobicity to the superabsorbent polymer may be insufficient, based on the total molar number of the hydrophobic materials, so that agglomeration between particles may not be suppressed.

Meanwhile, at least a portion of the first hydrophobic material and the second hydrophobic material may be present on the surface of the superabsorbent polymer particles. Wherein, the description "at least a portion of the first hydrophobic material and the second hydrophobic material may be present on the surface of the superabsorbent polymer particle" means that at least a portion of the first hydrophobic material and the second hydrophobic material is adsorbed or bound to the surface of the superabsorbent polymer particle. In particular, the first hydrophobic material and the second hydrophobic material may be physically or chemically adsorbed on the surface of the superabsorbent polymer. More specifically, the hydrophilic functional groups of the first hydrophobic material and the second hydrophobic material may be physically adsorbed to the hydrophilic portions of the superabsorbent polymer surface by intermolecular forces, such as dipole-dipole interactions. Accordingly, the hydrophilic portions of the first and second hydrophobic materials may be physically adsorbed onto and cover the surface of the superabsorbent polymer particle, and the hydrophobic portions of the first and second hydrophobic materials may not be adsorbed onto the surface of the polymer particle, and thus, in the superabsorbent polymer particle, the portion on which the hydrophobic material is adsorbed may exhibit hydrophobicity.

Therefore, in the case where at least a portion of the first hydrophobic material and the second hydrophobic material is present on the surface of the superabsorbent polymer particles, the agglomeration during exposure of the superabsorbent polymer particles to air can be more effectively suppressed, as compared to the case where all of the hydrophobic material is present inside the superabsorbent polymer particles, in particular, inside the crosslinked polymer.

Meanwhile, the superabsorbent polymer composition may further include a surface cross-linked layer formed by additionally cross-linking the cross-linked polymer by the surface cross-linking agent on at least a portion of the surface of the superabsorbent polymer particles. It is intended to increase the surface cross-linking density of the superabsorbent polymer particles, and in the case where the superabsorbent polymer particles further comprise a surface cross-linking layer, it may have a structure in which the outer cross-linking density is higher than the inner cross-linking density.

As the surface cross-linking agent, a surface cross-linking agent previously used in the preparation of the superabsorbent polymer may be used without particular limitation. For example, the surface cross-linking agent may include: one or more polyols selected from the group consisting of ethylene glycol, propylene glycol, 1, 3-propanediol, 1, 4-butanediol, 1, 6-hexanediol, 1, 2-hexanediol, 1, 3-hexanediol, 2-methyl-1, 3-propanediol, 2, 5-hexanediol, 2-methyl-1, 3-pentanediol, 2-methyl-2, 4-pentanediol, tripropylene glycol, and glycerol; one or more carbonate-based compounds selected from the group consisting of ethylene carbonate, propylene carbonate, and glycerol carbonate; epoxy compounds such as ethylene glycol diglycidyl ether and the like;azoline compounds, e.g.Oxazolidinones and the like; a polyamine compound; sheetOxazolidinone compound, bisOxazolidinone compounds or polypeptidesAn oxazolidinone compound; or a cyclic urea compound; and so on.

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

Further, about 90 wt%, preferably 95 wt% or more of the superabsorbent polymer composition may be superabsorbent polymer particles having a particle size of about 150 μm to 850 μm, based on the total weight of the superabsorbent polymer composition.

Further, the superabsorbent polymer composition can have a Centrifuge Retention Capacity (CRC) measured according to EDANA method WSP241.3 of 30g/g or greater, or 31g/g or greater, or 33g/g or greater, and 40g/g or less, or 38g/g or less, or 37g/g or less.

Further, the superabsorbent polymer composition can have an Absorbency Under Pressure (AUP) at 0.3psi of 18g/g or greater, or 20g/g or greater, or 22g/g or greater, and 27g/g or less, or 25g/g or less, as measured according to EDANA method WSP 242.3.

Further, the Anti-blocking (a/C) efficiency of the superabsorbent polymer composition may be 20% or more, more specifically 30% or more, 40% or more, or 50%, and the higher the value, the more excellent the Anti-blocking efficiency, so there is no upper limit to the Anti-blocking efficiency, but for example, it may be 75% or less, 70% or less, or 65% or less. Wherein the anti-caking efficiency is calculated by the following mathematical formula 3:

[ mathematical formula 3]

A/C(％)＝W₆/W₅×100

In the case of the mathematical formula 3,

W₅is the weight (g) of the superabsorbent polymer composition applied to a culture dish having a diameter of 10cm, and

W₆to uniformly apply the superabsorbent polymer composition on a culture dish having a diameter of 10cm, the culture dish was maintained in a constant temperature and humidity chamber having a temperature of 40 ℃. + -. 3 ℃ and a humidity of 80%. + -. 3% for 10 minutes, and then the culture dish was turned upside down on a filter paper and tapped 3 times, and then the weight (g) of the superabsorbent polymer composition dropped from the culture dish.

Further, the wetting time of the superabsorbent polymer may be 15 seconds or less, more specifically 13 seconds or less, 10 seconds or less, or 5 seconds or less, which is defined as the total time for which non-wetted superabsorbent polymer composition is observed on top of the liquid while 2g of the superabsorbent polymer composition is put into 50mL of a saline solution of 23 ℃ to 24 ℃ and stirred at 600rpm with a magnetic bar (8 mm in diameter, 30mm in length), and the smaller the value, the more excellent the wetting time, so the lower limit of the wetting time is theoretically 0 second, but for example, it may be 1 second or more.

Among them, the measuring method of the characteristics of the superabsorbent polymer composition will be explained in detail in the following examples.

Accordingly, in the case of using two hydrophobic materials satisfying a specific chemical formula at the same time as described above, it is possible to provide a superabsorbent polymer composition having excellent absorption properties and anti-blocking efficiency, in which the anti-blocking (a/C) efficiency calculated by mathematical formula 3 is 20% or more and the wetting time is 15 seconds or less.

Method for preparing superabsorbent polymer composition

Meanwhile, according to another embodiment of the present disclosure, there is provided a method for preparing a superabsorbent polymer composition, including the steps of: performing a cross-linking polymerization of a water-soluble ethylenically unsaturated monomer having at least partially neutralized acidic groups in the presence of an internal cross-linking agent and a polymerization initiator to form a hydrogel polymer; introducing and grinding a hydrophobic composition comprising a first hydrophobic material and a second hydrophobic material into a hydrogel polymer to produce a ground product comprising wet superabsorbent polymer particles and the hydrophobic composition; and drying the ground product to produce a superabsorbent polymer composition comprising superabsorbent polymer particles, a first hydrophobic material, and a second hydrophobic material.

Hereinafter, a method for preparing a superabsorbent polymer according to one embodiment will be described in detail according to the respective steps.

In a method for preparing a superabsorbent polymer according to one embodiment, the following steps are first performed: crosslinking polymerizing a water-soluble ethylenically unsaturated monomer having at least partially neutralized acidic groups in the presence of an internal crosslinking agent and a polymerization initiator to form a hydrogel polymer.

This step may include the steps of: the water-soluble ethylenically unsaturated monomer, the internal crosslinking agent, and the polymerization initiator are mixed to prepare a monomer composition, and thermal polymerization or photopolymerization of the monomer composition is performed to form the hydrogel polymer. Among them, as for the water-soluble ethylenically unsaturated monomer and the internal crosslinking agent, the above description can be referred to.

The internal crosslinking agent may be used in an amount of 0.01 to 5 parts by weight, based on 100 parts by weight of the water-soluble ethylenically unsaturated monomer in the monomer composition. For example, the internal crosslinking agent may be used in an amount of 0.01 parts by weight or more, 0.05 parts by weight or more, 0.1 parts by weight or more, or 0.2 parts by weight or more, and 5 parts by weight or less, 3 parts by weight or less, 2 parts by weight or less, 1 part by weight or less, or 0.5 parts by weight or less, based on 100 parts by weight of the water-soluble ethylenically unsaturated monomer. If the content of the internal crosslinking agent is too low, crosslinking may not sufficiently occur, and thus it may be difficult to achieve strength beyond an optimum level, whereas if the content of the internal crosslinking agent is too high, the internal crosslinking density may increase, and thus it may be difficult to achieve a desired centrifuge retention capacity.

Further, the polymerization initiator may be appropriately selected according to the polymerization method, and in the case of using thermal polymerization, a thermal polymerization initiator may be used; in the case of photopolymerization, a photopolymerization initiator may be used; and in the case of using a hybrid polymerization method (using both heat and light), both a thermal polymerization initiator and a photopolymerization initiator may be used. However, even in the case of photopolymerization, since a certain amount of heat is generated by UV irradiation or the like and some degree of heat is generated according to the progress of the exothermic polymerization reaction, a thermal polymerization initiator may be additionally included.

As the photopolymerization initiator, any compound capable of forming radicals by light such as UV can be used without limitation.

As the photopolymerization initiator, one or more selected from the following may be used: benzoin ethers, dialkyl acetophenones, hydroxy alkyl ketones, phenyl glyoxylates, benzyl dimethyl ketals, acyl phosphines and alpha-amino ketones. Meanwhile, specific examples of acylphosphines may include diphenyl (2,4, 6-trimethylbenzoyl) phosphine oxide, phenyl bis (2,4, 6-trimethylbenzoyl) phosphine oxide, ethyl (2,4, 6-trimethylbenzoyl) phenylphosphonite, and the like. Further different photopolymerization initiators are described in Reinhold Schwalm, UV Coatings: bases, Recent Developments and New Application (Elsevier2007), page 115 and are not limited to the above examples.

Further, as the thermal polymerization initiator, at least one selected from a persulfate initiator, an azo initiator, hydrogen peroxide, and ascorbic acid may be used. Specific examples of the persulfate initiator may include sodium persulfate (Na)₂S₂O₈) Potassium persulfate (K)₂S₂O₈) Ammonium persulfate ((NH)₄)₂S₂O₈) Etc., and specific examples of the azo initiator may include 2, 2-azobis (2-amidinopropane) dihydrochloride, 2-azobis- (N, N-dimethylene) isobutyramidine dihydrochloride, 2- (carbamoylazo) isobutyronitrile, 2-azobis [2- (2-imidazolin-2-yl) propane ] dihydrochloride]Dihydrochloride, 4-azobis- (4-cyanovaleric acid), and the like. Further different thermal initiators are described on page 203 of "principles of Polymerization (Wiley, 1981)" by Odian and are not limited to the above examples.

Such a polymerization initiator may be added in a content of 2 parts by weight or less based on 100 parts by weight of the water-soluble ethylenically unsaturated monomer. That is, if the concentration of the polymerization initiator is too low, the polymerization speed may become slow and a large amount of residual monomers may be extracted in the final product. Conversely, if the concentration of the polymerization initiator is too high, polymer chains constituting the network may become short, and thus the water-soluble content may increase and the absorption rate under pressure may decrease, thereby deteriorating the characteristics of the polymer.

Further, the monomer composition may further contain additives such as a thickener, a plasticizer, a preservation stabilizer, an antioxidant, and the like, as necessary.

Further, the monomer composition containing the monomer may be in a solution state, dissolved in a solvent such as water, and the solid content in the monomer composition in the solution state, that is, the concentrations of the monomer, the internal crosslinking agent and the polymerization initiator may be appropriately controlled in consideration of the polymerization time and the reaction conditions. For example, the solids content in the monomer composition can be 10 to 80 weight percent, or 15 to 80 weight percent, or 20 to 60 weight percent.

In the case where the monomer composition has a solid content in the above range, since a gel effect occurs in the polymerization reaction of the high-concentration aqueous solution, it is not necessary to remove unreacted monomers after the polymerization, and it may be advantageous to control the milling efficiency when milling the polymer, as described below.

Here, the solvent that can be used is not limited in its constitution as long as it can dissolve or disperse the above-mentioned raw materials, and for example, one or more selected from the following may be used alone or in combination: water, ethanol, ethylene glycol, diethylene glycol, triethylene glycol, 1, 4-butane diol, propylene glycol, ethylene glycol monobutyl ether, propylene glycol monomethyl ether acetate, methyl ethyl ketone, acetone, methyl amyl ketone, cyclohexanone, cyclopentanone, diethylene glycol monomethyl ether, diethylene glycol diethyl ether, toluene, xylene, butyrolactone, carbitol, methyl cellosolve acetate, N-dimethylacetamide, and the like.

Meanwhile, the crosslinking polymerization of the water-soluble ethylenically unsaturated monomer having an acid group at least partially neutralized may be performed without particular limitation as long as it can form a hydrogel polymer by thermal polymerization, photopolymerization, or hybrid polymerization.

Specifically, polymerization methods are roughly classified into thermal polymerization and photopolymerization according to a polymerization energy source, and generally, thermal polymerization may be performed in a reactor (e.g., a kneader) having a stirring shaft, and photopolymerization may be performed in a reactor equipped with a movable conveyor belt or in a flat-bottomed container, but the above polymerization methods are merely examples, and the present disclosure is not limited thereto.

For example, the hydrogel polymer may be obtained by: the above monomer composition is introduced into a reactor equipped with a stirring shaft (for example, a kneader), and hot air is supplied or the reactor is heated to perform thermal polymerization. Here, the hydrogel polymer discharged to the outlet of the reactor may be obtained in a size of several centimeters to several millimeters according to the shape of the stirring shaft provided in the reactor. Specifically, the size of the obtained hydrogel polymer may vary depending on the concentration of the introduced monomer composition, the introduction speed, and the like, and in general, a hydrogel polymer having a (weight average) particle diameter of 2mm to 50mm may be obtained.

Further, in the case where photopolymerization of the monomer composition is carried out in a reactor equipped with a movable conveyor belt as described above, a hydrogel polymer in the form of a sheet having the width of the belt can be obtained. Wherein the thickness of the sheet may vary depending on the concentration of the introduced monomer mixture and the introduction speed or the introduction amount, but preferably, the monomer composition is supplied so as to obtain the polymer in the form of a sheet having a thickness of about 0.5cm to about 5 cm. In the case where the monomer composition is supplied such that the thickness of the polymer in the form of a sheet may be too thin, production efficiency may be low, and if the thickness of the polymer in the form of a sheet is more than 5cm, polymerization may not uniformly occur throughout the thickness due to the too thick thickness.

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

Wherein the hydrogel polymer obtained may have a water content of 30 to 70% by weight. For example, the hydrogel polymer can have a water content of 40 wt.% or more, or 45 wt.% or more, and 70 wt.% or less, 65 wt.% or less, 60 wt.% or less, or 50 wt.% or less. In terms of conducting the polymerization, the water content of the hydrogel polymer should not be less than 30% by weight, and if the water content of the hydrogel polymer is too high, the hydrophobic composition may penetrate into the inside of the polymer, so that the inhibition of agglomeration between the prepared particles may not be significant.

Here, the "water content" is a content of moisture based on the total weight of the hydrogel polymer, and it means a value obtained by subtracting the weight of the polymer in a dry state from the weight of the hydrogel polymer. Specifically, it is defined as a value calculated by measuring a weight loss according to evaporation of moisture in the polymer while raising the temperature of the polymer in a crumb state by heating via infrared rays to perform drying. Among them, the drying condition may be set such that the temperature is raised from room temperature to about 180 ℃ and then maintained at 180 ℃, and the total drying time may be 40 minutes, including 5 minutes of the temperature raising step.

Next, a hydrophobic composition comprising a first hydrophobic material and a second hydrophobic material is introduced to the hydrogel polymer, and the mixture is then ground to produce a ground product comprising wet superabsorbent polymer particles and the hydrophobic composition. For details of the first hydrophobic material and the second hydrophobic material, reference may be made to the above description.

In a conventional method of preparing a superabsorbent polymer, a hydrogel polymer is coarsely ground without introducing a hydrophobic material, and then ground to a desired particle size to prepare the superabsorbent polymer. In such a case, the coarsely ground superabsorbent polymer particles may aggregate or agglomerate through the water used during the process, thereby increasing the internal load and causing equipment failure. In addition, a strong force should be applied in order to grind the thus aggregated superabsorbent polymer into a desired particle size, and thus, the properties of the superabsorbent polymer may be deteriorated.

However, as described above, in the case where the hydrogel polymer is ground together with the first hydrophobic material and the second hydrophobic material, particles having a desired particle diameter may be prepared without aggregating the ground particles. Thus, the method for preparing a superabsorbent polymer composition according to one embodiment enables grinding into particles having a desired particle size without applying an intensive force, thereby greatly reducing the production cost of the superabsorbent polymer.

In this step, the total weight of the first hydrophobic material and the second hydrophobic material may be 0.01 parts by weight to 1 part by weight, based on 100 parts by weight of the hydrogel polymer. Specifically, the first hydrophobic material and the second hydrophobic material may be used in an amount of 0.1 parts by weight or more, or 0.2 parts by weight or more, and 1 part by weight or less, 0.8 parts by weight or less, or 0.5 parts by weight or less, based on 100 parts by weight of the hydrogel polymer. In the case where too few first and second hydrophobic materials are used, the hydrophobic materials may not be uniformly applied on the surface of the hydrogel polymer, so that the effect of imparting hydrophobicity may not be significant, and if too many first and second hydrophobic materials are used, the characteristics of the finally prepared superabsorbent polymer may be deteriorated.

Such first and second hydrophobic materials may be included in the hydrophobic composition as raw materials or in the form of an aqueous dispersion, respectively.

More specifically, the first hydrophobic material and the second hydrophobic material may be introduced into the hydrogel polymer as raw materials, wherein in the case where the first hydrophobic material is solid at room temperature, it may be melted by heat generated during grinding after introduction, thereby being adsorbed onto the ground polymer particles.

In addition, the first hydrophobic material and the second hydrophobic material may be introduced while being mixed in water. That is, the hydrophobic composition may further include water, wherein the solid content of the hydrophobic composition may be 0.5 wt% or more and 100 wt% or less. Hydrophobic compositions having the above solids content ranges may be suitable because they can be uniformly applied on the hydrogel polymer.

The hydrophobic composition may be introduced into the reactor in which the hydrogel polymer has been prepared and mixed, or may be introduced into the mixer together with the hydrogel polymer and sprayed, or may be introduced by being continuously supplied into the continuously running mixer together with the hydrogel polymer.

After the hydrophobic composition is introduced into the hydrogel polymer, grinding may be performed so that the particle size of the wet superabsorbent polymer particles may be 300 μm to 5000 μm. Herein, "wet superabsorbent polymer particles" means particles having a water content of about 40% by weight or more, and may have a water content of 30% by weight to 70% by weight as the hydrogel polymer since it is formed by grinding the hydrogel polymer in the form of particles without a separate drying process. Particle size can be measured according to EDANA (european disposables and nonwovens association, EDANA) standard EDANAWSP 220.3.

Among them, as a grinder for grinding, specifically, a vertical crusher, a turbo cutter, a turbo grinder, a rotary chopper (rotary mill), a chopper (chopper mill), a disc mill, a shredder, a crusher, a chopper (chopper), and a disc cutter may be used, but it is not limited thereto.

However, in terms of process stability, it is preferable to perform the grinding process using a chopper.

Meanwhile, at least a portion of the first hydrophobic material and the second hydrophobic material included in the ground product may be present on the surface of the wet superabsorbent polymer particles. As mentioned above, the expression "at least a portion of the first hydrophobic material and the second hydrophobic material is present on the surface of the wet superabsorbent polymer particles" means that at least a portion of the first hydrophobic material and the second hydrophobic material is adsorbed or bound to the surface of the wet superabsorbent polymer particles. Since the hydrophobic material is introduced after the polymer is formed, rather than during the polymerization process of the water-soluble ethylenically unsaturated monomer, re-agglomeration of the wet superabsorbent polymer particles can be inhibited as compared to the case where the hydrophobic material is introduced during the polymerization process and the hydrophobic material is present inside the polymer.

Next, the ground product is dried to produce a superabsorbent polymer composition comprising superabsorbent polymer particles, a first hydrophobic material, and a second hydrophobic material.

The drying of the ground product may be performed such that the water content of the plurality of superabsorbent polymer particles contained in the prepared superabsorbent polymer composition may be about 10% by weight or less, respectively, specifically, about 0.1% by weight to about 10% by weight.

Wherein the drying temperature may be about 60 ℃ to about 250 ℃. If the drying temperature is too low, the drying time may be too long, and if the drying temperature is too high, only the surface of the polymer may be dried, and thus, there is a concern that the characteristics of the finally prepared superabsorbent polymer are deteriorated. Thus, preferably, drying may be carried out at a temperature of from about 100 ℃ to about 240 ℃, more preferably from about 110 ℃ to about 220 ℃.

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

The drying method is not particularly limited as long as it is generally used in the drying process. Specifically, the drying may be performed by hot air supply, infrared irradiation, ultrahigh frequency irradiation, UV irradiation, or the like.

Further, after the ground product is dried, it may be ground using a grinder so that the finally prepared superabsorbent polymer particles may be composed of particles of about 150 to about 850 μm.

As the grinder that can be used, a pin mill, a hammer mill, a screw mill, a roll mill, a disc mill, a jog mill, or the like can be used, but it is not limited thereto.

Thereafter, according to necessity, a step of forming a surface cross-linked layer on at least a part of the surface of the superabsorbent polymer particles in the presence of a surface cross-linking agent may be further included. By this step, the crosslinked polymer contained in the superabsorbent polymer particles may be additionally crosslinked by the surface crosslinking agent, thereby forming a surface crosslinked layer on at least a part of the surface of the superabsorbent polymer particles.

Such surface cross-linking agents may be used in an amount of about 0.001 parts by weight to about 5 parts by weight, based on 100 parts by weight of the superabsorbent polymer particles. For example, the surface cross-linking agent may be used in an amount of 0.005 parts by weight or more, 0.01 parts by weight or more, or 0.05 parts by weight or more, and 5 parts by weight or less, 4 parts by weight or less, or 3 parts by weight or less, based on 100 parts by weight of the superabsorbent polymer particles. By controlling the content range of the surface cross-linking agent within the above range, a superabsorbent polymer exhibiting excellent absorption characteristics can be prepared.

In addition, in the step of forming the surface cross-linked layer, an inorganic material may be additionally added to the surface cross-linking agent. That is, the step of forming surface crosslinks may be performed by additionally crosslinking the surface of the superabsorbent polymer particles in the presence of a surface crosslinking agent and an inorganic material.

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

Further, the method of mixing the surface cross-linking agent with the superabsorbent polymer composition is not limited. For example, the surface cross-linking agent and the superabsorbent polymer composition may be placed in a reactor and mixed, or the surface cross-linking agent may be sprayed onto the superabsorbent polymer composition, or the superabsorbent polymer composition and the surface cross-linking agent may be continuously supplied to a continuously running mixer and mixed.

In mixing the surface cross-linking agent and the superabsorbent polymer composition, water and methanol may be additionally mixed and added. With the addition of water and methanol, the surface cross-linking agent can be uniformly dispersed in the superabsorbent polymer composition. Among them, the content of the added water and methanol can be properly controlled so as to cause uniform dispersion of the surface crosslinking agent, prevent agglomeration of the superabsorbent polymer composition, and optimize the penetration depth of the crosslinking agent.

The surface crosslinking process may be performed at a temperature of about 80 ℃ to about 250 ℃. More specifically, the surface crosslinking process may be performed at a temperature of about 100 ℃ to about 220 ℃, or about 120 ℃ to about 200 ℃ for about 20 minutes to about 2 hours, or about 40 minutes to about 80 minutes. When the above surface crosslinking conditions are satisfied, the surface of the superabsorbent polymer particles can be sufficiently crosslinked, so that the absorption rate under pressure can be increased.

The temperature raising means for the surface crosslinking reaction is not particularly limited. The heating medium may be supplied, or the heat source may be directly supplied to heat. Here, the kind of the heating medium that may be used may include a fluid having an increased temperature, such as steam, hot air, hot oil, etc., but is not limited thereto, and may be appropriately selected in consideration of the manner of the heating medium, the rate of temperature increase, and the temperature to be increased. Meanwhile, the heat source directly supplied may include electric heating, gas heating, etc., but is not limited thereto.

In the following, preferred embodiments are presented for a better understanding of the present disclosure. However, these embodiments are presented merely as illustrations of the present disclosure, and the present disclosure is not limited thereto.

EXAMPLE-preparation of superabsorbent Polymer composition

Example 1

In a 3L glass vessel equipped with a stirrer and a thermometer, 100g (1.388mol) of acrylic acid, 0.26g of polyethylene glycol diacrylate as an internal crosslinking agent (PEGDA, Mw: 400), 0.008g of diphenyl (2,4, 6-trimethylbenzoyl) phosphine oxide as a photopolymerization initiator, 0.20g of sodium persulfate as a thermal polymerization initiator, and 123.5g of a 32% caustic soda solution were mixed with 40.0g of water at room temperature to prepare a monomer composition (neutralization degree of acrylic acid: 70 mol%, solid content: 45.0 wt%).

Thereafter, the monomer composition was supplied at a rate of 500 mL/min to 2000 mL/min on a conveyor belt of 10cm in width and 2m in length rotating at 50 cm/min. Further, while supplying the monomer composition, at 10mW/cm²Was irradiated with UV at an intensity of 46.5 wt% to perform polymerization for 60 seconds, thereby obtaining a hydrogel polymer having a water content of 46.5 wt%.

Next, to the hydrogel polymer, a hydrophobic composition (solvent: water, solid content 2.91 wt%) containing stearic acid (represented by the following chemical formula 1-1, manufactured by LG Household & Health Care) and laureth-6 carboxylic acid (represented by the following chemical formula 2-1, manufactured by KAO) in a molar ratio of 7:3 was introduced so that the total weight becomes 0.3 parts by weight based on 100 parts by weight of the hydrogel polymer, and then grinding was performed using a meat grinder so that the hydrogel polymer becomes particles having a particle diameter of 300 μm to 5000 μm. Wherein the wet superabsorbent polymer particles contained in the ground product had a water content of 46% by weight.

Thereafter, the milled product was dried in hot air at 185 ℃ for 30 minutes using a pneumatic oven.

To 100g of the dried product, a solution mixture of 3.2g of ultrapure water, 4.5g of methanol and 0.13g of ethylene carbonate was introduced and mixed for 1 minute using a magnetic stirrer, and then subjected to a surface crosslinking reaction for 60 minutes using a convection oven at 198 ℃. And, then, sieving it to prepare a superabsorbent polymer composition comprising superabsorbent polymer particles of 150 to 850 μm.

[ chemical formula 1-1]

[ chemical formula 2-1]

Example 2

A superabsorbent polymer composition was prepared by the same method as in example 1, except that a hydrophobic composition comprising stearic acid and laureth-6 carboxylic acid in a molar ratio of 5:5 was used.

Example 3

A superabsorbent polymer composition was prepared by the same method as in example 1, except that a hydrophobic composition comprising stearic acid and laureth-6 carboxylic acid in a molar ratio of 3:7 was used.

Example 4

A superabsorbent polymer composition was prepared by the same method as example 1, except that a hydrophobic composition containing myristic acid (manufactured by Sigma Aldrich) represented by the following chemical formula 1-2 was used instead of stearic acid represented by chemical formula 1-1 in example 1.

[ chemical formulas 1-2]

Example 5

A superabsorbent polymer composition was prepared by the same method as example 1, except that a hydrophobic composition comprising myristic acid represented by chemical formula 1-2 and laureth-11 carboxylic acid (manufactured by KAO) represented by the following chemical formula 2-2 was used instead of the hydrophobic composition comprising stearic acid represented by chemical formula 1-1 and laureth-6 carboxylic acid represented by chemical formula 2-1 in example 1.

[ chemical formula 2-2]

Example 6

A superabsorbent polymer composition was prepared by the same method as example 1, except that a hydrophobic composition containing palmitic acid (manufactured by Sigma Aldrich) represented by the following chemical formula 1-3 was used instead of stearic acid represented by chemical formula 1-1 in example 1.

[ chemical formulas 1-3]

Example 7

A superabsorbent polymer composition was prepared by the same method as example 1, except that a hydrophobic composition comprising palmitic acid represented by chemical formula 1-3 and laureth-11 carboxylic acid represented by chemical formula 2-2 was used instead of the hydrophobic composition comprising stearic acid represented by chemical formula 1-1 and laureth-6 carboxylic acid represented by chemical formula 2-1 in example 1.

Comparative example 1

A superabsorbent polymer composition was prepared by the same method as in example 1, except that a hydrophobic composition was not used.

Comparative example 2

A superabsorbent polymer composition was prepared by the same method as in example 1, except that a hydrophobic composition containing only stearic acid in example 1 was used.

Comparative example 3

A superabsorbent polymer composition was prepared by the same method as in example 1, except that a hydrophobic composition containing only laureth-6 carboxylic acid of example 1 was used.

Comparative example 4

A superabsorbent polymer composition was prepared by the same method as example 1, except that a hydrophobic composition comprising a compound represented by the following chemical formula a was used instead of stearic acid in example 1.

[ chemical formula A ]

Comparative example 5

A superabsorbent polymer composition was prepared by the same method as example 1, except that a hydrophobic composition containing a compound represented by the following chemical formula B was used instead of laureth-6 carboxylic acid in example 1.

[ chemical formula B ]

[ Experimental example ]

For the superabsorbent polymer compositions prepared in examples and comparative examples, the Centrifuge Retention Capacity (CRC), the Absorbency Under Pressure (AUP), the wetting time, and the anti-blocking (a/C) efficiency were measured, respectively, and the results are shown in table 1 below.

(1) Centrifuge Retention Capacity (CRC)

Centrifuge Retention Capacity (CRC) by suction without load was measured according to the european disposables and nonwovens association (EDANA) standard EDANAWSP 241.3.

Specifically, from each of the polymer compositions obtained in examples and comparative examples, polymers sieved through sieves #30 to #50 were obtained. W is to be₀(g, about 0.2g) the superabsorbent polymer was uniformly placed in an enclosure made of a nonwoven fabric and sealed, and then immersed in a saline solution (0.9 wt% aqueous sodium chloride solution) at room temperature. After 30 minutes, the encapsulate was drained at 250G for 3 minutes using a centrifuge, and then the weight W of the encapsulate was measured₂(g) In that respect Further, the same operation was carried out without using the super absorbent polymer, and then the weight W at that time was measured₁(g)。

Using the obtained weight, CRC (g/g) was calculated according to the following numerical formula 1.

[ mathematical formula 1]

CRC(g/g)＝{[W₂(g)-W₁(g)]/W₀(g)}-1

(2) Absorbency Under Pressure (AUP)

For each of the superabsorbent polymer compositions of the examples and comparative examples, the 0.3psi Absorbency Under Pressure (AUP) was measured according to EDANA method WSP 242.3.

First, the sieved polymer used for measuring CRC was used in measuring the absorption under pressure.

Specifically, a 400-mesh wire net made of stainless steel was mounted on the bottom of a plastic cylinder having an inner diameter of 25 mm. Under the conditions of room temperature and 50% humidity, W is mixed₀(g) (0.16g) each super absorbent polymer was uniformly sprinkled on the wire mesh, and a piston having an outer diameter of slightly less than 25mm and also capable of providing a load of 0.3psi was mounted thereon so that there was no gap with the inner wall of the cylinder and no hindrance to the up and down movement. At this time, the weight W of the apparatus is measured₃(g)。

A glass filter having a diameter of 90mm and a thickness of 5mm was placed inside a petri dish having a diameter of 150mm, and a saline solution composed of 0.9 wt% sodium chloride was put to the same level as the upper side of the glass filter. On which is placedA piece of filter paper with a diameter of 90mm is placed. The measuring device was placed on a glass filter and the liquid was absorbed under pressure for 1 hour. After 1 hour, the measuring device is lifted and the weight W is measured₄(g)。

Using each obtained weight, AUP (g/g) was calculated according to the following numerical formula 2.

[ mathematical formula 2]

AUP(g/g)＝[W₄(g)-W₃(g)]/W₀(g)

(3) Wetting time

The wetting time of each of the superabsorbent polymers of the examples and comparative examples was measured in seconds according to the method for measuring vortex time described in published International patent application No. 1987-003208.

Specifically, while 2g of the superabsorbent polymer composition was placed in 50mL of a saline solution at 23 ℃ to 24 ℃, stirred at 600rpm with a magnetic bar (8 mm in diameter, 30mm in length), the total time for which unwetted superabsorbent polymer composition was observed at the top of the liquid was observed. It was evaluated that the wetting time was not good as the time was longer.

(4) Anti-caking (A/C) efficiency

2g (W)₅) Each of the superabsorbent polymer compositions prepared in examples and comparative examples was uniformly applied to a culture dish having a diameter of 10cm, and maintained in a constant temperature and humidity chamber having a temperature of 40 ℃. + -. 3 ℃ and a humidity of 80%. + -. 3% for 10 minutes, then the culture dish was turned upside down on a filter paper and tapped 3 times, and then the amount of the superabsorbent polymer composition (W) falling from the culture dish was measured₆)。

The anti-blocking property was calculated according to the following numerical formula 3 using the measured weight, and the higher the value, the more excellent the anti-blocking property.

[ mathematical formula 3]

A/C(％)＝W₆/W₅×100

In the case of the mathematical formula 3,

W₅is the weight (g) of the superabsorbent polymer composition applied to a culture dish having a diameter of 10cm, and

W₆to absorb super-absorbentThe polymer composition was uniformly applied on a culture dish having a diameter of 10cm, which was maintained in a constant temperature and humidity chamber having a temperature of 40 ℃. + -. 3 ℃ and a humidity of 80%. + -. 3% for 10 minutes, and then the weight (g) of the superabsorbent polymer composition dropped from the culture dish after inverting the culture dish over a filter paper and tapping 3 times.

[ Table 1]

Referring to table 1, unlike the superabsorbent polymer composition of the comparative example in which the first and second hydrophobic materials are not used, or only one hydrophobic material is used, or one of the two hydrophobic materials does not correspond to the hydrophobic material of the present disclosure, the superabsorbent polymer composition of the example in which both the first and second hydrophobic materials are introduced while grinding the hydrogel polymer exhibits a wetting time of 15 seconds or less and an anti-blocking (a/C) efficiency of 20% or more.

It can thus be determined that when a hydrogel polymer is ground in the presence of two hydrophobic materials having different hydrophobic characteristics, a superabsorbent polymer composition having improved anti-blocking properties can be prepared without deteriorating the absorption properties.