WO2017155197A1

WO2017155197A1 - Method for preparing superabsorbent resin, and superabsorbent resin

Info

Publication number: WO2017155197A1
Application number: PCT/KR2017/000057
Authority: WO
Inventors: 윤형기; 남대우; 이혜민; 한장선; 서성종
Original assignee: 주식회사 엘지화학
Priority date: 2016-03-11
Filing date: 2017-01-03
Publication date: 2017-09-14

Abstract

The present invention relates to a method for preparing a superabsorbent resin, which maintains excellent absorption performance and exhibits improved liquid permeability and absorption rate. The method for preparing a superabsorbent resin may comprise the steps of: performing cross-linking polymerization on a water-soluble ethylenically unsaturated monomer having an at least partially neutralized acidic group to form a hydrogel polymer comprising a cross-linked polymer, in the presence of an internal cross-linking agent; drying, pulverizing, and classifying the hydrogel polymer to form a base resin powder; and performing surface cross-linking on the base resin powder by using a surface cross-linking liquid containing a surface cross-linking agent of an alkylene carbonate having 2 to 5 carbon atoms, in the presence of hydrophobic silica particles having a contact angle of greater than 10° and smaller than or equal to 150° with respect to water and hydrophilic silica particles having a contact angle of smaller than or equal to 10° with respect to water.

Description

[Specifications

[Name of invention]

Method for producing super absorbent polymer, and super absorbent polymer

Technical Field

Cross Citation with Related Application (s)

This application claims the benefit of priority based on Korea Patent Application No. 10-2016-0029834 dated March 1, 2016 and Korea Patent Application No. 10-2016-0103024 dated August 12, 2016, the corresponding Korean patent application All content disclosed in these references is included as part of this specification.

The present invention relates to a superabsorbent polymer and a method for preparing the same while maintaining excellent absorption performance and exhibiting improved liquid permeability, gel strength and absorption rate.

Background Art

Super Absorbent Polymer (SAP) is a synthetic polymer material capable of absorbing water of 500 to 1,000 times its own weight.As a developer, a super absorbent material (SAM) and an absorbent gel (AGM) They are named differently. Such super absorbent polymers have been put into practical use as physiological tools, and are currently used in sanitary products such as paper diapers for children, horticultural soil repair agents, civil engineering, building index materials, seedling sheets, freshness retainers in food distribution, and It is widely used as a material for steaming.

In most cases, such superabsorbent polymers are widely used in the field of sanitary products such as diapers and sanitary napkins. For this purpose, it is necessary to exhibit high absorption of moisture, and the absorbed moisture must not escape the external pressure. In addition, it is necessary to maintain the shape well even in the state where the water is absorbed by volume expansion (swelling) to exhibit excellent permeability.

In particular, as efforts have recently been made to provide a diaper that has a thinner thickness and a lighter weight, and exhibits superior performance, many efforts have been made to provide a superabsorbent polymer having improved absorption properties such as liquid permeability and absorption rate. Attention is focused. In order to achieve excellent absorption characteristics such as a high absorption rate and improved liquid permeability, the surface strength of the superabsorbent polymer particles, particularly the surface crosslinked layer, needs to be harder and thus high gel strength is required. It needs to be evenly and quickly dispersed in the absorbent core.

However, in the case of increasing the gel strength and improving the liquid permeability by a previously known method, there was a disadvantage in that the basic absorption performance (absorption under pressure and absorption under pressure) is greatly reduced.

As a result, it is possible to provide a super absorbent polymer with improved gel strength, liquid permeability and absorption rate while maintaining excellent basic absorption performance. There is a continuing need for the development of technologies that make this possible.

[Content of invention]

[Problem to solve]

The present invention is to provide a method for producing a super absorbent polymer, which exhibits improved fluid permeability, gel strength, absorption rate, and the like while maintaining excellent absorption performance.

[Measures of problem]

The present invention comprises the steps of cross-polymerizing a water-soluble ethylenically unsaturated monomer having at least a part of a neutralized acidic group in the presence of an internal crosslinking agent to form a hydrogel polymer comprising a crosslinked polymer;

Drying, pulverizing and classifying the hydrogel polymer to form a base resin powder; And

Surface crosslinking comprising a surface crosslinking agent of alkylene carbonates having 2 to 5 carbon atoms in the presence of hydrophobic silica particles having a contact angle of greater than 10 ^{° to} 150 ^° with respect to water and hydrophilic silica particles having a contact angle of 10 ^° or less with respect to water. It provides a method for producing a super absorbent polymer comprising the step of surface crosslinking the base resin powder using a liquid.

The present invention also provides a resin composition comprising: a base resin powder comprising a first crosslinked polymer of a water-soluble ethylenically unsaturated monomer having at least part of a neutralized acid group; Formed on the base resin powder, and the first crosslinked polymer A surface crosslinking layer comprising a second crosslinked polymer further crosslinked via a surface crosslinker; And

As a super absorbent polymer, which is dispersed on the surface crosslinking layer and comprises hydrophilic silica particles having a contact angle of 10 ^° or less with respect to water,

EFFC represented by the following formula 1 is 24 to 28g / g,

Flow inducibility (SFC; ^■ 1CT ⁷ cm ³ s / g) of physiological saline solution (0.685 weight ⁰ /. Aqueous sodium chloride solution) is 85 to 160 (1 (r ⁷ cm ³ s / g),

Provided is a super absorbent polymer having a gel strength (G ′) of 9,000 to 15,000 Pa:

[Equation 1]

EFFC = (CRC + AUP) / 2

CRC is the high indicates a centrifugation beam SAT for half an hour for a normal saline solution (0.9 weight ^_0/0 aqueous sodium chloride solution) of a water-absorbent resin, AUP is the super-absorbent resin of the physiological saline (0.9 wt. ⁰ /. Aqueous solution of sodium chloride Pressurized absorption capacity for 1 hour under 0.7 psi for

The gel strength (G ′) is the horizontal gel strength of the superabsorbent polymer measured using a rheometer after swelling by absorbing physiological saline solution (0.9 wt. ⁰ /. Sodium chloride solution) for 1 hour to the superabsorbent polymer. Indicates. Hereinafter, a super absorbent polymer according to a specific embodiment of the present invention and a manufacturing method thereof will be described in more detail. However, this is presented as an example of the invention, thereby not limited to the scope of the invention, it is apparent to those skilled in the art that various modifications to the embodiment is possible within the scope of the invention.

In addition, unless otherwise indicated throughout the specification, "including" or "containing" refers to including any component (or component) without particular limitation, and adding other components (or component). Cannot be interpreted as excluding. According to one embodiment of the invention, cross-polymerizing a water-soluble ethylenically unsaturated monomer having at least a part of a neutralized acidic group in the presence of an internal crosslinking agent to form a hydrogel polymer comprising a crosslinked polymer;

Surface crosslinking comprising a surface crosslinking agent of alkylene carbonate having 2 to 5 carbon atoms in the presence of hydrophobic silica particles having a contact angle of greater than 10 ^{° to} 150 ^° with respect to water and hydrophilic silica particles having a contact angle of 10 ^° or less with respect to water Provided is a method for producing a super absorbent polymer, the method comprising surface crosslinking the base resin powder using a liquid.

The present inventors have super-absorbent resin of the gel strength, barrel-component, and the absorption rate a ^'result of continuous studies in order to further improve, and the conditions of the production step of the water-absorbent resin, for example, the type of the internal cross-linking agent to be described later and content of the polymerization Conditions are optimized to obtain a base resin powder having a high gel strength, specific surface crosslinking conditions (e.g., simultaneous or separate use of certain silica particles, more specifically two or more hydrophilic and hydrophobic silica particles upon surface crosslinking, etc.). As the surface crosslinking proceeds under), it shows a significantly improved gel strength, permeability and absorption rate than previously known, while maintaining excellent absorption performance (absorption under pressure and under pressure; CRC, AUP and EFFC, etc. to be described later) It has been found that superabsorbent resins can be provided.

In particular, the surface having a predetermined level or more on the base resin powder having a high gel strength as the specific silica particles defined in a predetermined contact angle range is used during the surface crosslinking, and the surface crosslinking is carried out under constant temperature raising conditions or the like. It appears that the crosslinking layer can be formed uniformly. This is because the specific silica particles are uniformly included in the crosslinking structure of the surface crosslinking layer to make the crosslinking structure more firm, and the surface crosslinking reaction occurs appropriately around each silica particle under the above elevated temperature conditions during surface crosslinking, thereby providing an appropriate crosslinking structure. It is expected because it can be formed.

Accordingly, the surface crosslinking layer may further increase the gel strength of each of the superabsorbent polymer particles, so that the superabsorbent polymer of one embodiment may have high gel strength. Significantly improved SFC and liquid permeability, and thus improved absorption rate. In addition, the superabsorbent polymer prepared by the method of the embodiment can maintain excellent absorption performance defined by relatively high EFFC (arithmetic mean value of CRC and AUP) as the internal crosslinking structure and the surface crosslinking structure are optimized.

Accordingly, the superabsorbent polymer of one embodiment is highly desirable for various sanitary materials, such as ultra-thin diapers with reduced pulp content, as it exhibits excellent absorption performance with significantly improved fluidity, gel strength and absorption rate than previously known. Can be applied. Hereinafter, a method of preparing the super absorbent polymer of one embodiment will be described in more detail.

Superabsorbent polymers typically contain a water-soluble ethylenically unsaturated monomer having an acidic group at least partially neutralized in the presence of an internal crosslinking agent, such as, for example, a mixture of acrylic acid and its sodium salt in which at least some carboxylic acid is neutralized with sodium salt or the like. After polymerization, it can be prepared by drying, pulverizing and classifying and surface crosslinking. In a specific example, in the manufacturing method of the embodiment, the superabsorbent polymer crosslinks the monomer in the presence of an internal crosslinking agent to obtain a base resin powder, and then, in the presence of a predetermined surface crosslinking agent and hydrophobic and hydrophilic silica particles. It can be obtained by surface crosslinking the base resin powder.

In particular, by adjusting the type and content of the internal crosslinking agent and polymerization conditions, to obtain a base resin powder having a high gel strength, for example, specific silica particles, more specifically hydrophilic and hydrophobic silica particles defined by the contact angle range to water As the surface crosslinking proceeds using, it was confirmed that a super absorbent polymer having excellent properties and effects as described above can be produced. In a preferred embodiment, in the production method of this embodiment, the following hydrophilic silica particles, more specifically, the hydrophilic and hydrophobic silica particles as follows can be used at the time of surface crosslinking.

First, in the one embodiment the manufacturing method, when the surface cross-linked more than 10 ^° for water and 10 ^° or greater than 150 ^° or less, and more suitably from 12 ^° to 150 ^° of the And the hydrophobic silica particles having a contact angle, it is possible to use hydrophilic silica particles having a contact angle of 10 ^° or less, or from 1 to 10 ^° against water. Accordingly, the superabsorbent polymer prepared by the method of the embodiment may further include hydrophilic silica particles and / or hydrophobic silica particles dispersed on the surface of the base resin powder, for example, on the surface crosslinking layer. In this case, the hydrophilic silica particles or the hydrophobic silica particles are dispersed on the surface crosslinking layer means that each of these silica particles are contained / dispersed in the crosslinked structure of the surface crosslinking layer or embedded in the surface of the surface crosslinking layer. It may mean.

On the other hand, in one specific example, the hydrophobic silica particles may be included in the surface crosslinking solution and treated as described in more detail below, or may be separately mixed and treated on the base resin powder before the black surface crosslinking. Thus, such hydrophobic silica particles may, for example, be present at least in part on the surface of the base resin powder, for example in the surface crosslinking layer, and a portion thereof may be embedded in the surface of the base resin powder. . In addition, the hydrophilic silica particles may be dispersed on the surface crosslinking layer and present in the crosslinking structure included therein, or a part thereof may be embedded in the surface of the surface crosslinking layer.

By treating the hydrophobic and hydrophilic silica particles in the above-described manner, these hydrophilic and / or hydrophobic silica particles can effectively surround the surface crosslinking liquid. For this reason, it can suppress that a surface crosslinking liquid is absorbed rapidly only to a part of base resin powder locally, and can apply | coat uniformly over the base resin powder whole surface. Therefore, surface crosslinking can be made uniform, and these silica particles can also be uniformly distributed on the surface crosslinking layer. As such, hydrophilic and / or hydrophobic silica particles for improving the liquid permeability are present on at least the surface crosslinking layer, and the surface crosslinking solution is uniformly applied so that the surface crosslinking is uniformly performed on the base resin powder, thereby improving liquid permeability. Etc. Excellent physical properties can be expressed and maintained for a long time.

As the hydrophobic silica particles, at least one of the commercialized hydrophobic silica particles having the above-described contact angle range may be used without any particular limitation, and more preferably, the hydrophobic silica particles may be included in the surface crosslinking solution. When used, particles having a contact angle of more than 10 ^{° and} 50 ^° or less may be used in view of dispersibility to the surface crosslinking liquid, or particles having a contact angle of 50 ^° to 150 ^° or less may be used together with a separate dispersant.

In addition, when the hydrophobic silica particles are added and mixed separately to the base resin powder before the surface crosslinking, the particles having a contact angle of 50 ^° to 150 ^° or less may be more preferably used in terms of more effective fluid permeability and absorption rate. Can be. In addition, as the hydrophilic silica particles, one or more kinds of commercially available water-dispersible silica particles having a contact angle range of 10 ^° or less may be used without any particular limitation.

More specifically, the hydrophobic silica particles are trade name: DM30S or

Hydrophobic silica particles made of Aerosil or the like can be suitably used. As the hydrophilic silica particles, water-dispersible silica particles made of trade name: ST-O or ST-AK or the like can be used as appropriate, and the liquid permeability and absorption rate of the superabsorbent polymer, etc. Can be further improved.

In addition, a contact angle with respect to water for separating the hydrophilic and hydrophobic silica particles may be defined as a contact angle with respect to water of each silica particle measured on a glass substrate.

On the other hand, in the manufacturing method of the super absorbent polymer of one embodiment, the water-soluble ethylenically unsaturated monomer is acrylic acid, methacrylic acid, maleic anhydride, fumaric acid, crotonic acid, itaconic acid, 2-acryloylethane sulfonic acid, 2-methacryl Anionic monomers and salts thereof of loylethanesulfonic acid, 2- (meth) acryloylpropanesulfonic acid, or 2- (meth) acrylamide-2-methyl propane sulfonic acid; (Meth) acrylamide, N-substituted (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate,

Nonionic hydrophilic containing monomers of methoxypolyethylene glycol (meth) acrylate or polyethylene glycol (meth) acrylate; And an amino group-containing unsaturated monomer of (Ν, Ν) -dimethylaminoethyl (meth) acrylate or (Ν, Ν) -dimethylaminopropyl (meth) acrylamide and its quaternized product; It may include. Of these, acrylic acid or salts thereof, such as at least a portion of acrylic acid Alkali metal salts such as neutralized acrylic acid and / or sodium salt thereof may be used, and the use of such monomers enables the production of superabsorbent polymers having better physical properties. When the alkali metal salt of acrylic acid ¾ or the like is used as a monomer, at least a portion of acrylic acid may be neutralized with a basic compound such as caustic soda (NaOH).

In addition, the internal crosslinking agent for crosslinking polymerization of such monomers includes bis (meth) acrylamide having 8 to 12 carbon atoms, poly (meth) acrylate having 2 to 10 carbon atoms, and poly (meth) having a polyol having 2 to 10 carbon atoms. One or more types selected from the group consisting of allyl ether can be used. More specifically, the internal crosslinking agent is one selected from the group consisting of polyethylene glycol di (meth) acrylate, polypropyleneoxy di (meth) acrylate, glycerin diacrylate, glycerin triacrylate, and trimethy triacrylate. The poly (meth) acrylate of the above poly can be used suitably. Among these, as the internal crosslinking agent such as polyethylene glycol di (meth) acrylate is used, an internal crosslinked structure can be optimized and a base resin powder having a high gel strength can be obtained. The water absorbent resin can be obtained more appropriately.

Further, the specific internal crosslinking agent is 0.005 mol or more, black is 0.005 to 0.1 mol, or 0.005 to 0.05 mol (black is 0.3 parts by weight relative to 100 parts by weight of acrylic acid) based on 1 mol of unneutralized acrylic acid contained in the monomer. Or 0.3 to 0.6 parts by weight). According to the content range of the internal crosslinking agent, a base resin powder having a high gel strength before surface crosslinking can be appropriately obtained, and a superabsorbent polymer having excellent physical properties can be obtained through the method of one embodiment.

After the crosslinking polymerization of the monomer using the internal crosslinking agent, a base resin powder can be obtained through drying, pulverization, and classification, and the like, and the base resin powder and The superabsorbent polymer obtained is suitably manufactured and provided to have a particle size of 150 to 850 1. More specifically, the base resin powder and And obtained therefrom is at least 95 parts by weight ⁰ / of the water absorbent resin. This has a particle size of more than 150 to 850 rni, 3 a differential having a particle size of less than 150 parts by weight ⁰ / less than _0, or 1 to 0.5 is less than ⁰ wt. /. Can be.

Thus, as the particle size distribution of the base resin powder and the super absorbent polymer is adjusted to a preferred range, the superabsorbent polymer can more properly exhibit the excellent physical properties already described above.

On the other hand, it will be described in more detail in each step with respect to the method of the embodiment described above. However, the above-described monomer, internal crosslinking agent, silica particles, particle size distribution, and the like will not be repeated, and the remaining process configurations and conditions will be described step by step.

The method of preparing a superabsorbent polymer may include forming a hydrogel polymer including a crosslinked polymer by thermally polymerizing or photopolymerizing a monomer composition including a water-soluble ethylenically unsaturated monomer, an internal crosslinking agent, and a polymerization initiator; Drying the hydrogel polymer; Grinding and classifying the dried polymer to form a base resin powder; And surface crosslinking the base resin powder in the presence of the hydrophobic and hydrophilic silica particles using a surface crosslinking solution including a surface crosslinking agent of alkylene carbonate having 2 to 5 carbon atoms.

In such a production method, the monomer composition includes a water-soluble ethylenically unsaturated monomer, an internal crosslinking agent and a polymerization initiator, and the type of the monomer is as described above.

Further, in such a composition, the concentration of the water-soluble ethylenically unsaturated monomer may be 20 to 60 weight ⁰ /. Or 40 to 50 weight ⁰ /. With respect to the total monomer composition including each of the above-described raw materials and solvents. In consideration of polymerization time and reaction conditions, the concentration may be appropriate. However, if the concentration of the monomer is too low, the yield of the superabsorbent polymer may be low and there may be a problem in economics. On the contrary, if the concentration is too high, a part of the monomer may precipitate or the grinding efficiency of the polymerized hydrogel polymer may be low. Phase problems may occur and the physical properties of the super absorbent polymer may be reduced.

In addition, the polymerization initiator is generally used for the production of superabsorbent polymers. It will not specifically limit, if it is used.

Specifically, the polymerization initiator may use a thermal polymerization initiator or a photopolymerization initiator according to UV irradiation depending on the polymerization method. However, even with the photopolymerization method, since a certain amount of heat is generated by irradiation of ultraviolet radiation or the like, and a certain amount of heat is generated in accordance with the progress of the polymerization reaction, which is an exothermic reaction, it may further include a thermal polymerization initiator.

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

Examples of the photopolymerization initiator include benzoin ether, dialkyl acetophenone, hydroxyl alkylketone, phenyl glyoxylate, and benzyl dimethyl ketal. Ketal), acyl phosphine and alpha-aminoketone can be used at least one selected from the group consisting of. Meanwhile, as an example of acylphosphine, commercially available lucirin TPO, that is, 2,4,6-trimethyl-benzoyl-trimethyl phosphine oxide can be used. . A wider variety of photoinitiators are well specified in Reinhold Schwalm's book "UV Coatings: Basics, Recent Developments and New Application (Elsevier 2007)" p1 15, and are not limited to the examples described above.

The photopolymerization initiator may be included in a concentration of 0.01 to 1.0 weight ⁰ /. When the concentration of the photopolymerization initiator is too low, the polymerization rate may be slow. When the concentration of the photopolymerization initiator is too high, the molecular weight of the superabsorbent polymer may be low and the physical properties may be uneven.

In addition, the thermal polymerization initiator may be used at least one selected from the group consisting of persulfate initiator, azo initiator, hydrogen peroxide and ascorbine. Specifically, examples of persulfate-based initiators include sodium persulfate (Na ₂ S ₂ O ₈ ), potassium persulfate (K2S ₂ O ₈ ), and ammonium persulfate ((NH ₄ ) ₂ S ₂ 0 ₈ ), And examples of azo initiators include 2, 2-azobis- (2-amidinopropane) dihydrochloride (2, 2-azobis (2-amidinopropane) dihydrochloride), 2, 2-azobis -(N, N- Isobutyramidine dihydrochloride (2,2-azobis- (N, N-dimethylene) isobutyramidine dihydrochloride), 2-

(Carbamoylazo) isobutyronitrile (2- (carbamoylazo) isobutylonitril), 2,2-azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride (2,2-azobis [ 2- (2-imidazolin-2-yl) propane] dihydrochloride), 4'4-azobis- (4-cyanovaleric acid) (4,4-azobis- (4-cyanovaleric acid)), and the like. More various thermal polymerization initiators are well specified in Odian's Principle of Polymerization (Wiley, 1981), p203, and are not limited to the examples described above.

The thermal polymerization initiator may be included in a concentration of 0.001 to 0.5% by weight based on the monomer composition. When the concentration of the thermal polymerization initiator is too low, additional thermal polymerization hardly occurs, and the effect of the addition of the thermal polymerization initiator may be insignificant. When the concentration of the thermal polymerization initiator is too high, the molecular weight of the superabsorbent polymer may be low and the physical properties may be uneven. have.

In addition, the type of the internal crosslinking agent included in the monomer composition is the same as described above, and the internal crosslinking agent is included at a concentration of 0.01 to 0.5 weight ⁰ / ^{° relative} to the monomer composition to crosslink the polymerized polymer. Can be. In addition, as described above, the internal crosslinking agent is 0.005 moles or more, or 0.005 to 0.1 moles, or 0.005 to 0.05 moles (or 100 parts by weight of acrylic acid) based on 1 mole of unneutralized acrylic acid contained in the monomer. 0.3 parts by weight or more, or 0.3 to 0.6 parts by weight). As such an internal crosslinking agent is used in this content range, a high gel strength of the base resin powder can be appropriately achieved, and a super absorbent polymer can be prepared which more appropriately stratifies the physical properties of the above-described embodiment by using this. In addition, the monomer composition may further include additives such as thickeners, plasticizers, preservative stabilizers, antioxidants, and the like, as necessary.

Raw materials such as the above-mentioned water-soluble ethylenically unsaturated monomers, photopolymerization initiators, thermal polymerization initiators, internal crosslinking agents and additives may be prepared in the form of a monomer composition solution dissolved in a solvent. The solvent that can be used at this time can be used without limitation in the composition as long as it can dissolve the above-mentioned components, for example, water, ethanol, _ Ethylene glycol, diethylene glycol, triethylene glycol, 1,4-butanedi, propylene glycol, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, methyl ethyl ketone, acetone, methyl amyl ketone 1 selected from cyclonucleanone, cyclopentanone, diethylene glycol monomethyl ether, diethylene glycol ethyl ether toluene, xylene, butyrolactone carbyl, methyl cellosolve acetate and Ν, Ν-dimethylacetamide, etc. It can use combining a species or more.

The solvent may be included in the remaining amount except for the above-described components with respect to the total content of the monomer composition.

On the other hand, if the method of forming a hydrogel polymer by thermally polymerizing or photopolymerizing such a monomer composition is also the polymerization method normally used, there will be no restriction | limiting in particular in a structure.

Specifically, the polymerization method is largely divided into thermal polymerization and photopolymerization according to the energy source of polymerization, and when the thermal polymerization is usually carried out, the polymerization method may be performed in a reactor having a stirring shaft such as a kneader. Although it can proceed in a reactor with a conveyor belt, the above-described polymerization method is an example, the present invention is not limited to the above-described polymerization method.

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

In addition, when the photopolymerization is carried out in the reaction 7 ^' with a movable conveyor belt as described above, the form of the hydrogel polymer usually obtained may be a hydrogel gel polymer on the sheet having the width of the belt. At this time, the thickness of the polymer sheet depends on the concentration and the injection rate of the monomer composition to be injected, but it is usually preferable to supply the monomer composition so that a polymer on the sheet having a thickness of 0.5 to 5 cm can be obtained. Of the polymer on the sheet When the monomer composition is supplied to such an extent that the thickness is too thin, the production efficiency is low, which is not preferable. When the polymer thickness on the sheet exceeds 5 cm, the polymerization reaction may not occur evenly over the entire thickness due to the excessively thick thickness.

The normal water content of the hydrogel polymer obtained in this way may be a 40 to 80 wt. ^_0/0. On the other hand, throughout the present specification, "water content" means the content of water to account for the total weight of the hydrogel polymer minus the weight of the polymer in the dry state. Specifically, it is defined as a value calculated by measuring the weight loss due to moisture evaporation in the polymer in the process of raising the temperature of the polymer through infrared heating and drying. At this time, the drying conditions are raised to 18C C at room temperature and maintained at 180 ^° C. The total drying time is set to 20 minutes, including 5 minutes of the temperature rise step, the moisture content is measured.

Next, the step of drying the obtained hydrogel polymer is performed.

At this time, if necessary to coarse grinding before drying to increase the efficiency of the drying step may be more rough.

At this time, the pulverizer used is not limited in configuration, specifically, a vertical pulverizer, a turbo cutter, a turbo grinder, a rotary cutter mill, a cutting machine Includes any one selected from the group of grinding machines consisting of cutter mills, disc mills, shred crushers, crushers, choppers and disc cutters Although it is possible, it is not limited to the above-mentioned example. At this time, the coarse grinding step may be pulverized so that the particle size of the hydrogel polymer is 2 to 15mm.

Grinding to a particle diameter of less than 2 mm is not technically easy due to the high water content of the hydrogel polymer, and may also cause agglomeration between the milled particles. On the other hand, when the particle size is pulverized more than 15 mm, the effect of increasing the efficiency of the subsequent drying step may be insignificant.

As described above, drying is performed on the hydrogel polymer immediately after the polymerization which is coarsely crushed or not subjected to the coarsely crushing step. At this time, the drying of the drying step The temperature may be 150 to 250 ^° C. If the drying temperature is less than 150 ^° C, the drying time may be too long and the physical properties of the final superabsorbent polymer may be lowered. If the drying temperature exceeds 250 ^C C, only the polymer surface may be dried excessively. Fine powder may occur in the grinding step, and there is a fear that the physical properties of the superabsorbent polymer to be finally formed decrease. Therefore, preferably, the drying may be performed at a temperature of 150 to 200 ^° C, more preferably at a temperature of 160 to 180 ^° C.

On the other hand, in the case of drying time, in consideration of the process efficiency, etc., it may proceed for 20 to 90 minutes, but is not limited thereto.

If the drying method of the drying step is also commonly used as a drying step of the hydrogel polymer, it can be selected and used without limitation of the configuration. Specifically, the drying step may be performed by a method such as hot air supply infrared irradiation microwave irradiation or ultraviolet irradiation. The water content of the polymer after such a drying step may be about 0.1 to about 10 weight ⁰ /.

Next, a step of pulverizing the dried polymer obtained through such a drying step is performed.

The polymer powder obtained after the grinding step may have a particle diameter of 150 to 850 / im. Grinders used to grind to such particle diameters are specifically pin mills, hammer mills, screw mills, mills, disc mills or jogs. A jog mill or the like may be used, but is not limited to the example described above.

In addition, in order to manage the physical properties of the super absorbent polymer powder to be finalized after such a grinding step, a separate process of classifying the polymer powder obtained after grinding according to the particle diameter may be performed. Preferably, a polymer having a particle size of 150 to 850 m may be classified, and only a polymer powder having such a particle size may be produced through a surface crosslinking reaction step. Since the particle size distribution of the base resin powder obtained through the above process has already been described above, further detailed description thereof will be omitted.

On the other hand, after obtaining the base resin powder through the above-mentioned grinding and / or classification process, it is possible to produce a super absorbent polymer of one embodiment through a surface crosslinking process. have. Since the kind of hydrophilic and / or hydrophobic silica particles which can be used in such a surface crosslinking process is already mentioned above, the related description is abbreviate | omitted.

In such a surface crosslinking process, in one example, in the presence of a surface crosslinking solution containing the hydrophobic silica particles, the hydrophilic silica particles, and the surface crosslinking agent, the base resin powder may be thermally treated to surface crosslink. In another example, the hydrophobic silica particles are first mixed and added to the base resin powder, and then the base resin powder is heat-treated in the presence of a surface crosslinking solution including the hydrophilic silica particles and the surface crosslinking agent. It may also proceed by a method of crosslinking.

In the method according to the above example, in order to properly disperse the hydrophobic silica particles in the surface crosslinking liquid, particles having a contact angle of more than 10 ° and 50 ° or less (that is, silica particles exhibiting relatively small hydrophobicity) are used. Alternatively, particles having a contact angle of 50 ^° to 150 ^° or less may be used together with a separate dispersant. As the dispersant, any dispersant used to disperse the hydrophobic silica particles in a polar solvent such as a water-soluble solvent can be used without any particular limitation, and for example, a Tween dispersant, a Span dispersant, or a polysaccharide dispersant can be used. .

And, in another example method of separately treating the hydrophobic silica particles first, the hydrophobic silica particles may be mixed with the base resin powder in a solid state, and the surface thereof may be subjected to dry treatment. Or a method of mixing.

In addition, the hydrophobic silica particles and hydrophilic silica particles may be used in an amount of 0.0001 to 0.3 parts by weight, or 0.001 to 0.1 parts by weight based on 100 parts by weight of the base resin powder, respectively. Thereby, according to the use of each silica particle, the fluid permeability and the absorption rate of a super absorbent polymer can be improved more effectively.

The method for adding the surface crosslinking liquid containing the hydrophilic silica particles and the surface crosslinking agent and optionally the hydrophobic silica particles to the base resin powder is not particularly limited. For example, the surface crosslinking liquid, The base resin powder may be mixed in a semi-permanent mixture, or the surface crosslinking solution may be sprayed onto the base resin powder, or the base resin powder and the surface crosslinking solution may be continuously supplied to the mixer to be operated continuously. Further, in the surface crosslinking step, more suitable examples of the alkylene carbonate having 2 to 5 carbon atoms that can be used as the surface crosslinking agent include ethylene carbonate, propylene carbonate, butylene carbonate, and the like. Of course, it can also be used.

In addition, the surface crosslinking solution may further include a polycarboxylic acid copolymer disclosed in Korean Patent Application Publication No. 2015-0143167 (Korean Patent Application No. 2014-0072343), and the copolymer may further include the base resin powder. Based on 100 parts by weight, it may be included in the surface crosslinking liquid in an amount of 0.01 to 0.1. According to the use of this specific surface crosslinking liquid, the excellent particle strength, liquid permeability and absorption performance of one embodiment, etc. can be more effectively achieved.

In addition, the surface crosslinking liquid may further include water and / or methanol as a medium. Thereby, there is an advantage that the surface crosslinking agent and the silica particles can be evenly dispersed on the base resin powder. At this time, the content of water and methanol is to 100 parts by weight of the base resin powder for the purpose of inducing even dispersion of the surface crosslinking agent and silica particles, preventing aggregation of the base resin powder and optimizing the surface penetration depth of the surface crosslinking agent. It can be applied by adjusting the addition ratio.

On the other hand, the surface crosslinking step, 5 minutes to 80 minutes, or 10 minutes to a maximum reaction temperature of 140 ^° C to 20 C C, or 150 ^° C to 190 ^° C with respect to the base resin powder to which the surface cross-linking solution is added The heat treatment may be performed for 70 minutes or 20 minutes to 65 minutes to proceed with the surface crosslinking reaction. More specifically, the surface cross-linking step is the temperature rise to the reaction maximum temperature over 10 minutes to 40 minutes at an initial temperature of 20 ° C to 130 ^° C, or 40 ^° C to 120 ^° C, the maximum temperature is 5 It can be carried out by maintaining the heat treatment for minutes to 80 minutes.

These surface crosslinking process conditions (especially elevated temperature conditions and reaction maximum The superabsorbent polymer which suitably stratifies the excellent liquid permeability, the absorption rate, etc. can be manufactured by layer reaction of reaction conditions at temperature).

The temperature raising means for surface crosslinking reaction is not specifically limited. It can be heated by supplying a heat medium or by directly supplying a heat source. In this case, as the type of heat medium that can be used, a heated fluid such as steam, hot air, or hot oil may be used. Consideration can be made as appropriate. On the other hand, the heat source directly supplied may be a heating method through electricity, a gas heating method, but is not limited to the above-described example. On the other hand, the superabsorbent polymer prepared by the above-described method is a base resin powder comprising a first crosslinked polymer of a water-soluble ethylenically unsaturated monomer having at least a part of the neutralized acid group; A surface crosslinking layer formed on the base resin powder, wherein the first crosslinking polymer comprises a second crosslinking polymer further crosslinked through a surface crosslinking agent; And hydrophilic silica particles dispersed on the surface crosslinking layer and having a contact angle of 10 ^° or less with respect to water. Such super-absorbent resin is spread on the surface cross-linked layer, it may further comprise a hydrophobic silica particles having a contact angle of 10 ^° or less than 150 ^° for water.

In addition, as described above, the hydrophilic and / or hydrophobic silica particles may be included in the crosslinked structure in the surface crosslinked layer and dispersed, or may be present in the surface crosslinked layer.

Such superabsorbent polymers have hydrophilic and / or hydrophobic silica particles upon surface crosslinking, a base resin powder is prepared under the above-described predetermined conditions, and as the surface crosslinking process proceeds, hydrophilic and / or hydrophobicity on the surface crosslinking layer. The silica particles may have a uniformly dispersed form, and furthermore, may exhibit excellent absorption performance with improved liquid permeability, gel strength and absorption rate. Various physical properties of such a super absorbent polymer may be defined by respective property values described below. First, the superabsorbent polymer may have a centrifugal water retention capacity (CRC) of 25 to 35 g / g, or 26 to 31 g / g. As such, the superabsorbent values obtained by the method of the embodiment may exhibit excellent absorbency under no pressure. At this time, the centrifugal water retention capacity (CRC) for the physiological saline can be calculated by the following formula 1 after absorbing the superabsorbent resin in physiological saline over 30 minutes:

[Calculation 1]

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

In the above formula 1,

W ₀ (g) is the initial weight of superabsorbent polymer (g), W ^ g) is absorbed by immersion in physiological saline for 30 minutes without using superabsorbent resin, and then centrifuge to 250G 3 The weight of the device measured after dehydration for a minute, W ₂ (g) is absorbed by immersing the superabsorbent resin in physiological saline for 30 minutes at room temperature, and then dehydrated at 250G for 3 minutes using a centrifuge, superabsorbent resin Including the measured device weight.

In addition, the superabsorbent polymer may have a pressure absorption capacity (AUP) of 24 to 30 g / g, or 24.2 to 27 g / g. As such, the superabsorbent polymer may exhibit excellent absorbency even under pressure.

This pressurized absorbent capacity (AUP) can be calculated according to Formula 2 after absorbing the superabsorbent resin in physiological saline under a pressurization of 0.7 psi over 1 hour:

[Calculation 2]

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

In Formula 2,

W ₀ (g) is the initial weight (g) of the superabsorbent polymer, W ₃ (g) is the sum of the weight of the superabsorbent polymer and the weight of the device capable of applying a load to the superabsorbent polymer, and W ₄ (g ) Is the sum of the weight of the superabsorbent resin and the weight of the device capable of applying a load to the superabsorbent resin after absorbing physiological saline to the superabsorbent resin for 1 hour under a load (0.7 psi).

Superabsorbent polymers prepared by the method of one embodiment of the above-mentioned range As the centrifugal water retention capacity (CRC) and the pressure absorption capacity (AUP) are shown, the superabsorbent polymer may have an EFFC of 24 to 28 g / g and a black color of 24.6 to 28 g / g.

[Equation 1]

EFFC = (CRC + AUP) / 2

CRC is the high-centrifuged for half an hour for a normal saline solution (0.9 ^weight-0 /. Aqueous sodium chloride solution) of a water-absorbent resin exhibits an SAT correction,

AUP represents the absorption capacity of the pressure for one hour under a 0.7psi for physiological saline solution (0.9 weight ^_0/0 aqueous sodium chloride solution) of the superabsorbent polymer.

As such, the superabsorbent polymer may have excellent absorption performance such as basic absorption and absorption under pressure.

Further, a super-absorbent resin mentioned above is induced Saline Flow (SFC) for a physiological saline solution of 30 to ^{^{160 1 (T 7 cm 3 s}} / g, or 85 to ^{^{160 10- 7 cm 3 's /}} g, or 85 To 120 ^' 1 (T ⁷ cm ^3' s / g. As such, the superabsorbent polymer may exhibit improved fluid permeability than previously known. This may include silica particles or the like in the surface crosslinking layer. The surface crosslinking layer having a thickness of a predetermined level or more appears to be uniformly formed.

Such physiological saline flow inducibility (SFC) is a method well known to those skilled in the art, for example, column 16 of US Patent Publication No. 2009-0131255

According to the method disclosed in [0184] to [0189], it can be measured and calculated.

Then, the above-mentioned super-absorbent resin has such a high saline solution (0.9 weight ^_0/0 aqueous sodium chloride solution), after swelling by absorbing the horizontal direction, the gel strength of the superabsorbent polymer by using a rheometer for 1 hour, the water-absorbent resin (G When measuring '), the gel strength (G') can be 9,000 to 15,000 Pa, or 9,000 to 13,000 Pa.

The horizontal gel strength G 'can better reflect the excellent liquid permeability under the actual use environment of the super absorbent polymer. In other words, the liquid permeability of the super absorbent polymer is generally included in sanitary materials such as diapers. At the same time, it can be determined to be more relevant depending on whether the force applied in the horizontal direction is excellent and whether it exhibits good shape retention and high gel strength. The horizontal gel strength may well reflect the gel strength directly related to the liquid permeability. Can be. Therefore _; As the superabsorbent polymer having such a horizontal gel strength G 'satisfying the above-mentioned range exhibits excellent liquid permeability, it has been found that the superabsorbent polymer can be used very favorably in sanitary materials such as diapers.

This horizontal gel strength G 'can be measured by absorbing physiological saline in the superabsorbent resin for 1 hour and then using a commercialized rheometer in a method comprising each of the following steps:

1) swelling by absorbing physiological saline to the super absorbent polymer;

2) placing the swollen superabsorbent resin between the plates of the rheometer having a predetermined interval and pressing both plate surfaces;

3) using the rheometer under vibration to increase the shear strain, to identify the shear strain in a linear viscoelastic regime section in which the storage modulus and loss modulus are constant;

4) measuring the storage elasticity of the swelled superabsorbent resin and the loss modulus, respectively, and the average value of the storage elastic modulus as the gel strength under the identified shear deformation. As described above, the superabsorbent polymer obtained according to the method of the embodiment maintains excellent water absorption performance such as water retention capacity and pressure absorption capacity, and can achieve improved fluid permeability, gel strength and absorption rate. Therefore, hygiene materials such as diapers, in particular, ultra-thin hygiene materials having a reduced content of the peel can be used as appropriate.

【Effects of the Invention】

According to the present invention, a superabsorbent performance such as water-retaining capacity and pressure-absorbing capacity can be maintained excellent, and a superabsorbent polymer can be produced and provided with more improved fluid permeability, gel strength and absorption rate.

Such superabsorbent polymers have a high content of sanitary materials, especially diapers, such as diapers. Reduced ultra-thin hygiene and the like can be used as appropriate.

[Specific contents to carry out invention]

Hereinafter, one preferred embodiment for the purpose of understanding the present invention, the following examples are merely to illustrate the present invention is not limited to the scope of the following examples. Examples below. And in the comparative examples, the contact angles of the hydrophobic silica particles and the hydrophilic silica particles with respect to water were measured as follows.

First, a hydrophobic silica particle was used as a coating liquid dispersed in a methylene chloride solvent at a concentration of 5 weight ⁰ /. After the coating solution was spin coated on the wafer, the contact angle was measured by dropwise dropping water on the coating layer. The measured contact angle is defined as the contact angle of the hydrophobic silica particles with respect to water, and the measured values are shown in Table 1 below.

In addition, in the case of hydrophilic silica particles, except that a coating liquid dispersed in water at a concentration of 20 weight ⁰ /.

TABLE 1

In addition, in the following Example and the comparative example, the physical property of each super absorbent polymer was measured and evaluated by the following method.

(1) Grain size evaluation

The particle diameters of the base resin powder and the super absorbent polymer used in the examples and the comparative examples were measured according to the European Disposables and Nonwovens Association (EDANA) standard EDANA WSP 220.3 method. (2) Centrifuge Retention Capacity (CRC)

According to the European Disposables and Nonwovens Association (EDANA) standard EDANA WSP 241.3, for the superabsorbent polymers of the Examples and Comparative Examples, the centrifugal water-retaining capacity (CRC) by unloaded absorption ratio was measured.

That is, the resin of Examples and Comparative Examples W ₀ (g, about 0.2g) after the insert uniformly in the envelope of the nonwoven fabric is sealed _(se al), 0.9 at room temperature. It was immersed in the physiological saline solution which becomes the sodium chloride aqueous solution of the weight of ⁰ /. After 30 minutes, the envelope was centrifuged and drained at 250 G for 3 minutes, and then the mass W ₂ (g) of the envelope was measured. Moreover, after performing the same operation without using resin, the mass W ^ g at that time was measured.

Using each mass thus obtained, CRC (g / g) was calculated according to the following equation 1 to confirm the water holding capacity.

[Calculation 1]

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

In the above formula 1,

W ₀ (g) is the initial weight (g) of the super absorbent polymer,

W ^ g) is the weight of the device measured after immersion in physiological saline for 30 minutes without using a super absorbent polymer, and then dehydrated at 250 G for 3 minutes using a centrifuge,

W ₂ (g) is the weight of the device, including the super absorbent polymer, after absorbing the superabsorbent polymer in physiological saline at room temperature for 30 minutes and then dehydrating it at 250 G for 3 minutes using a centrifuge. (3) Absorbing under Pressure (AUP)

For the superabsorbent polymers of Examples and Comparative Examples, Absorbency under Pressure (AUP) was measured according to the method of European Disposables and Nonwovens Association standard EDANA WSP 242.3.

First, a stainless steel 400 mesh on a cylindrical bottom of plastic with an inner diameter of 60 mm The wire mesh was fitted. Evenly spread the resin W ₀ (g, 0.90 g) obtained in Examples 1 to 6 and Comparative Examples 1 to 3 on a wire mesh under conditions of silver of 23 ± 2 ° C. and relative humidity of 45% and thereon 4.83 kPa ( The piston, which can give a uniform load of 0.7 psi), has an outer diameter of slightly smaller than 60 mm, no gap with the inner wall of the cylinder, and unhindered movement of up and down. At this time, the weight W ₃ (g) of the apparatus was measured.

A glass filter having a diameter of 125 mm and a thickness of 5 mm was placed on the inside of the petri dish having a diameter of 150 mm, and the physiological saline composed of 0.90 weight ⁰ / ^° sodium chloride was brought to the same level as the upper surface of the glass filter. One sheet of filter paper 120 mm in diameter was loaded thereon. The measuring device was placed on the filter paper and the liquid was absorbed for 1 hour under load. After 1 hour, the measuring device was lifted up and the weight W ₄ (g) was measured.

Using each mass thus obtained, AUP (g / g) was calculated according to the following equation 2 to confirm the pressure absorbing ability.

[Calculation 2]

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

In Formula 2,

W ₀ (g) is the initial weight (g) of the superabsorbent polymer,

W ₃ (g) is the sum of the weight of the superabsorbent polymer and the weight of the device capable of applying a load to the superabsorbent polymer,

W ₄ (g) is the sum of the weight of the superabsorbent resin and the device weight capable of applying a load to the superabsorbent resin after absorbing physiological saline into the superabsorbent resin for 1 hour under a load (0.7 psi). (4) saline flow conductivity (SFC)

It was measured according to the method disclosed in [0184] to [0189] of column 16 of US Patent Publication No. 2009-0131255.

(5) Gel Strength (G ')

Horizontal with respect to the super absorbent polymer / base resin powder of Examples and Comparative Examples Aroma Gel Strength was measured.

First, 0.5 g of the superabsorbent polymer samples (30-50 Mesh) of Examples and Comparative Examples were sieved through a sieve. The weighed sample was swollen in 50 g of saline solution for 1 hour. Thereafter, unabsorbed solvent was removed using an aspirator for 4 minutes, and the external solvent was evenly distributed over filter paper and wiped off once.

2.5 g of the swollen superabsorbent polymer sample is placed between the rheometer and two parallel plates (25 mm in diameter with a wall on the bottom to prevent 2 mm of sample from escaping), and the distance between the two parallel plates is 1 mm was adjusted. At this time, the swelled superabsorbent polymer sample was pressed with a force of about 3 N so as to contact all of the parallel plate surface to adjust the gap between the parallel plates.

Award 7 | The rheometer is used to identify the shear strain in a linear viscoelastic regime with constant storage modulus and loss modulus at an oscilation frequency of 10 rad / s with increasing shear strain. It was. Generally in a swollen superabsorbent polymer sample, 0.1% shear strain is within the linear viscoelastic state section.

At a constant oscillation frequency of 10 rad / s, the storage modulus and the loss modulus of the superabsorbent polymer swollen for 60 seconds at the shear strain value of the linear viscoelastic state section were measured, respectively. The storage modulus values obtained at this time were averaged to determine the horizontal gel strength. For reference, the loss modulus is measured to be a very small value compared to the storage modulus. Example 1:

In a 2L glass reaction vessel surrounded by a jacket in which the preheated medium ^at 25 ^° C is circulated, 500 g of acrylic acid, 2 g of polyethylene glycol diacrylate (PEGDA; Mw = 500) and 0.25 g of allyl acrylate are used as internal crosslinking agents. The initiator of IRGACURE 819 was injected at a content of 100 ppmw relative to the total acrylic acid.

Subsequently, 720 g of a 24 weight ⁰ /. Caustic soda (Na-H) solution in water was gradually added to the glass reactor and mixed. At the time of dropwise addition of the caustic soda solution, The temperature of the monomer composition rose to about 72 ^° C. and waited until it cooled to about 45 ^° C. Thereafter, the neutralization rate of acrylic acid in the monomer composition obtained as described above was found to be about 70 mol%.

After the temperature of the monomer composition was sensed ^at about 45 ^° C., 28 g of a sodium persulfate solution (diluted with 4 weight ⁰ / ^{° in} water) was prepared and mixed in the mixed solution.

Subsequently, the monomer composition was irradiated with light for 1 minute, and the polymerization reaction was carried out for 3 minutes by raising the temperature of the glass reaction vessel to 75 ^° C. The polymer obtained as a result of the polymerization was passed through a hole having a diameter of about 13 mm using a meat chopper to obtain a crumpled coarse polymer.

Subsequently, the polymer in the crumb state was dried in an oven capable of transferring air volume up and down. Specifically, the hot air of 18C C was flowed downwardly upwards for 15 minutes, and further upwards downwards for 15 minutes, thereby uniformly drying the polymer in the crumb state, and the water content of the final dried polymer was about 2% by weight. It adjusted to the following.

The dried polymer was pulverized with a grinder and then classified to obtain a base resin powder having a particle size of about 150 to 850.

For 100 g of the base resin powder, 0.04 g of hydrophobic silica particles of Aerosil 200, 0.04 g of hydrophilic silica particles of ST-O, 1.5 g of ethylene carbonate, Korean Patent Application No. 2015-0143167 (Korean Patent Application No. 2014-0072343 A surface treatment liquid containing 0.05 g of the polycarboxylic acid copolymer disclosed in Preparation Example 1 of Ho) and 4.0 g of water as a solvent was formed. The surface crosslinking liquid was sprayed onto the base resin powder and stirred at room temperature, and the mixture was mixed so that the surface treatment liquid was evenly distributed in the base resin powder. Subsequently, the base resin powder was put in a surface crosslinking reaction machine and surface crosslinking reaction was performed.

Within this surface crosslinking reaction vessel, the base resin powder was found to gradually increase in temperature at an initial temperature near 18C C, and was manipulated to reach a reaction temperature of 190 ^° C. after 30 minutes. After reaching this reaction maximum temperature, the final prepared superabsorbent polymer sample was taken after further reaction for 65 minutes. After the surface crosslinking process, using a sieve (sieve) A surface crosslinked superabsorbent polymer having a particle diameter of about 150 to 850 was obtained. Example 2:

For 100 g of the base resin powder obtained in the same manner as in Example 1, 0.02 g of hydrophobic silica particles of Aerosil 200, 0.02 g of hydrophilic silica particles of ST-O, 1.5 g of ethylene carbonate, Korean Patent Application Publication No. 2015-0143167 Example 1 except that a surface treatment liquid containing 0.05 g of the polycarboxylic acid copolymer disclosed in Preparation Example 1 of Korean Patent Application No. 2014-0072343 and 4.0 g of water as a solvent was used. A super absorbent polymer was prepared in the same manner.

After the surface crosslinking process, a surface crosslinked superabsorbent polymer having a particle size of about 150 to 850 was obtained using a sieve. Example 3:

For 100 g of the base resin powder obtained in the same manner as in Example 1, 0.03 g of hydrosilic silica particles of Aerosil 200, 0.03 g of hydrophilic silica particles of ST-®, 1.5 g of ethylene carbonate, Korean Patent Application Publication No. 2015-0143167 A surface treatment liquid containing 0.05 g of the polycarboxylic acid copolymer disclosed in Preparation Example 1 of Korean Patent Application No. 2014-0072343 and 4.0 g of water as a solvent was used, and was used in the same manner as in Example 1. A super absorbent polymer was prepared by the method.

After the surface crosslinking process, a surface crosslinked superabsorbent polymer having a particle size of about 150 to 850 m was obtained using a sieve. Example 4:

With respect to 100 g of the base resin powder obtained in the same manner as in Example 1, 0.02 g of hydrosilic silica particles of Aerosil 200, 0.04 g of hydrophilic silica particles of ST-®, 1.5 g of ethylene carbonate, Korean Patent Application No. 2015-0143167 To form a surface treatment liquid containing 0.05 g of the polycarboxylic acid-based co-polymer disclosed in Preparation Example 1 of Korean Patent Application No. 2014-0072343 and 4.0 g of water as a solvent. A superabsorbent polymer was prepared in the same manner as in Example 1 except that it was used.

After the surface crosslinking process, the particle size is about 150 to about 150 using a sieve.

A surface crosslinked superabsorbent polymer of 850 mm 3 was obtained. Example 5:

For 100 g of the base resin powder obtained in the same manner as in Example 1, 0.02 g of hydrophobic silica particles of Aerosil 200, 0.06 g of hydrophilic silica particles of ST-O, 1.5 g of ethylene carbonate, Korean Patent Application Publication No. 2015-0143167 Example 1 except that a surface treatment liquid containing 0.05 g of the polycarboxylic acid copolymer disclosed in Preparation Example 1 of Korean Patent Application No. 2014-0072343 and 4.0 g of water as a solvent was used. A super absorbent polymer was prepared in the same manner.

After the surface crosslinking process, a surface crosslinked superabsorbent polymer having a particle size of about 150 to 850 was obtained using a sieve. Example 6:

With respect to 100 g of the base resin powder obtained in the same manner as in Example 1, 0.04 g of hydrophobic silica particles of Aerosil 200, 0.02 g of hydrophilic silica particles of ST-®, 1.5 g of ethylene carbonate, Korean Patent Application Publication No. 2015-0143167 Example 1 except that a surface treatment liquid containing 0.05 g of the polycarboxylic acid copolymer disclosed in Preparation Example 1 of Korean Patent Application No. 2014-0072343 and 4.0 g of water as a solvent was used. A super absorbent polymer was prepared in the same manner.

A surface crosslinked superabsorbent resin of 850 was obtained. Example 7:

Hydrophilic silica particles of Aerosil 200 hydrophobic silica particles 0.06 ST-O to 100 g of base resin powder obtained in the same manner as in Example 1 above 0.02 g, 1.5 g of ethylene carbonate, 0.05 g of the polycarboxylic acid copolymer disclosed in Preparation Example 1 of Korea Patent Application No. 2015-0143167 (Korean Patent Application No. I 2014-0072343) and 4.0 g of water as a solvent A super absorbent polymer was prepared in the same manner as in Example 1, except that the surface treatment liquid was formed and used.

After the surface crosslinking process, a surface crosslinked superabsorbent polymer having a particle size of about 150 to 850 was obtained using a sieve. Comparative Example 1:

With respect to 100 g of the base resin powder obtained in the same manner as in Example 1, 1.5 g of ethylene carbonate, the polycarboxylic acid system disclosed in Preparation Example 1 of Korean Patent Application No. 2015-0143167 (Korean Patent Application No. 2014-0072343) A super absorbent polymer was prepared in the same manner as in Example 1, except that a surface treatment solution containing 0.05 g of a copolymer and 4.0 g of water as a solvent was used.

After the surface crosslinking process, a surface crosslinked superabsorbent polymer having a particle size of about 150 to 850 was obtained using a sieve. Comparative Example 2:

For 100 g of the base resin powder obtained in the same manner as in Example 1, except that a surface treatment liquid containing 0.06 g of Aerosil 200 hydrophobic silica particles, 1.5 g of ethylene carbonate, and 4.0 g of water as a solvent was formed and used. Was prepared in the same manner as in Example 1.

After the surface crosslinking process, a surface crosslinked superabsorbent polymer having a particle size of about 150 to 850 was obtained using a sieve. The physical properties of CRC, AUP, SFC and gel strength were measured and evaluated for the superabsorbent polymers of Examples 1 to 7, Comparative Examples 1 and 2, and the measured physical properties are shown in Table 2 below. In addition, the EFFC value of Equation 1 was calculated from the measured CRC and AUP and shown in Table 2 together. TABLE 2

Referring to Table 2, it was confirmed that the super absorbent polymers of Examples 1 to 7 exhibited more than equivalent level of absorption characteristics (CRC, AUP and EFFC), and improved gel strength and fluidity.

Claims

【Claims】

【Claim 1】

Cross-polymerizing a water-soluble ethylenically unsaturated monomer having at least a partially neutralized acidic group in the presence of an internal cross-linking agent to form a water-soluble gel polymer including the cross-linking polymer;

Forming a base resin powder by drying, pulverizing and classifying the water-containing gel polymer; and

Surface cross-linking comprising a surface cross-linking agent of an alkylene carbonate having 2 to ⁵ carbon atoms in the presence of hydrophobic silica particles with a contact angle with respect to water of more than 10 ^° and up to 150 ^° and hydrophilic silica particles with a contact angle with water of less than 10 ° A method for producing a superabsorbent polymer comprising the step of surface crosslinking the base resin powder using a liquid.

【Claim 2】

The method of claim 1, wherein the surface crosslinking step includes surface crosslinking the base resin powder by heat treatment in the presence of a surface crosslinking solution containing the hydrophobic silica particles, the hydrophilic silica particles, and the surface crosslinking agent. Method for producing water absorbent resin.

【Claim 3】

The method of claim 2, wherein the hydrophobic silica particles have a contact angle with water of 50 ^° to 150 ^° , and the surface crosslinking liquid further includes a dispersant.

【Claim 4】

The method of claim 1, wherein the hydrophobic silica particles and the hydrophilic silica particles are each used in an amount of 0.0001 to 0.3 parts by weight based on 100 parts by weight of the base resin powder.

【Claim 5】 The method of claim 1, wherein the water-soluble ethylenically unsaturated monomer is acrylic acid, methacrylic acid, maleic anhydride, fumaric acid, crotonic acid, itaconic acid, 2-acryloylethane sulfonic acid, 2-methacryloylethanesulfonic acid, 2- (meth)acryloylpropanesulfonic acid, or anionic monomers of 2-(meth)acrylamide-2-methylpropanesulfonic acid and salts thereof; (meth)acrylamide, N-substituted (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, meroxypolyethylene glycol (meth)acrylate or polyethylene glycol ( A nonionic hydrophilic-containing monomer of meth)acrylate; and (Ν,Ν)-dimethylaminoethyl (meth)acrylate or (Ν,Ν)-dimethylaminopropyl (meth)acrylamide, an amino group-containing unsaturated monomer and its quaternary product; at least one selected from the group consisting of A method for producing a superabsorbent polymer comprising:

【Claim 6】

The method of claim 1, wherein the internal crosslinking agent is bis(meth)acrylamide having 8 to 12 carbon atoms, poly(meth)acrylate of a polyol having 2 to 10 carbon atoms, and poly(meth)allyl ether of a polyol having 2 to 10 carbon atoms. A method for producing a superabsorbent polymer comprising at least one member selected from the group consisting of:

【Claim 7】

The method of claim 1, wherein the base resin powder is pulverized and classified to have a particle size of 150 to 850.

【Claim 8】

The method of claim 1, wherein the surface crosslinking step is carried out from an initial temperature of 20 ^° C to 130 ^° C, raised to a maximum temperature of 14°C to 20°C over 10 to 40 minutes, and the maximum temperature is maintained for 5 to 80 minutes. A method of manufacturing a superabsorbent polymer that is carried out by heat treatment while maintaining it for a while. 【Claim 9】

According to claim 1,

A method for producing a superabsorbent polymer having an EFFC of 24 g/g or more and 28 g/g or less, represented by the following formula:

[Equation 1]

EFFC = (CRC + AUP)/2 In Equation 1 above,

CRC represents the water retention capacity of the superabsorbent polymer in physiological saline (0.9% by weight sodium chloride aqueous solution) after centrifugation for 30 minutes,

AUP is the physiological saline solution of the superabsorbent polymer (0.

9 Weight ⁰ /。 It represents the pressure absorption capacity for 1 hour under 0.7psi for sodium chloride aqueous solution.

[Claim 10]

The method of claim 1, wherein the flow conductivity (SFC; ᄀ ^0-7 1 ³ 5/9) of the physiological saline solution (0.685 weight ⁰ /。 sodium chloride aqueous solution) is 85 to 160 C10 ^"7 cm ^3' s/g). Method for producing superabsorbent polymer.

【Claim 1 1】

A base resin powder comprising a first cross-linked polymer of a water-soluble ethylenically unsaturated monomer having at least a portion of a neutralized acidic group;

a surface cross-linked layer formed on the base resin powder and including a second cross-linked polymer in which the first cross-linked polymer is further cross-linked via a surface cross-linking agent; and

A superabsorbent polymer comprising hydrophilic silica particles dispersed on the surface cross-linked layer and having a contact angle with water of 10 ^° or less,

The EFFC expressed by the following formula 1 is 24 to 28 g/g,

The flow conductivity (SFC; ^■ 10 ^"7 cm ³ s/g) of saline solution (0.685 weight ⁰ /。 aqueous sodium chloride solution) is 85 to 160 C 10 ^"7 cm ³ s/g),

Superabsorbent polymer with a gel strength (G') of 9,000 to 15,000 Pa: [Equation 1]

EFFC = (CRC + AUP)/2 In Equation 1 above,

CRC represents the centrifugation retention capacity of the superabsorbent polymer for 30 minutes in physiological saline solution (0.9 weight ^0/0 sodium chloride aqueous solution), and AUP represents the physiological saline solution ₍ 0.9 weight ^0/0 sodium chloride aqueous solution) of the superabsorbent polymer. ) represents the pressure absorption capacity for 1 hour under 0.7psi,

The gel strength (G') refers to the horizontal gel strength of the superabsorbent polymer measured using a rheometer after the superabsorbent polymer was swollen by absorbing physiological saline solution (0.9% by weight sodium chloride aqueous solution) for 1 hour. .

【Claim 12】

The method of claim 11, wherein the surface cross-linked layer is dispersed in water and

A superabsorbent polymer further comprising hydrophobic silica particles having a contact angle of more than 10 ^° and less than or equal to 150 ^° .

[Claim 13]

The superabsorbent polymer according to claim 1 or 12, wherein the hydrophilic silica particles or the hydrophobic silica particles are dispersed in the surface cross-linked layer or embedded in the surface of the surface cross-linked layer.