【Technical field】

Mutual citation with the relevant application(s)

This application claims the benefit of priority based on Korean Patent Application No. 10-2017-0172277 filed on December 14, 2017, and all contents disclosed in the documents of the relevant Korean patent application are included as part of this specification.

The present invention relates to a super absorbent polymer having excellent water absorption performance and a method for producing the same.

【Background description】

Super Absorbent Polymer (SAP) is a synthetic polymer material that has the ability to absorb moisture of 500 to 1,000 times its own weight, and each developer has SM (Super Absorbent Polymer), AGM (Absorbent Gel). They are named with different names such as l ing Mater ial ). Since the above superabsorbent resins have begun to be put into practical use as sanitary tools, nowadays, in addition to hygiene products such as paper diapers for children, soil repair agents for gardening, civil engineering, construction materials, nursery sheets, freshness maintenance agents in the food distribution field, and It is widely used as a material for poultice.

In most cases, such super absorbent polymers are widely used in the field of sanitary materials such as diapers and sanitary napkins. In these sanitary materials, it is common that the superabsorbent polymer is contained in a state spread in pulp. However, in recent years, efforts have been made to provide sanitary materials such as diapers having a thinner thickness. As the demand for thin sanitary materials increases, the proportion of water absorbent resin in the sanitary materials tends to increase. For this, there is a need for a water absorbent resin to combine the performance of the pulp in the sanitary material. Therefore, it must have a high absorption rate as well as high liquid permeability and absorption rate.

In order to improve the absorption rate, generally, a foaming agent is used or the hydrogel is pulverized with high energy. In this case, a porous structure is formed on the surface and inside, which is easily crushed by external force. During the manufacturing process, dust is generated, making it difficult to work.

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There is a problem that causes clogging in the middle.

In order to solve such problems of dust generation and process clogging, conventionally, the strength of the fine powder reassembly was improved (Korean Patent No. 10-1559081), or the amount of dust generated was reduced by increasing the moisture content (International Application No.

?07汗2013八） 82503) This method is insufficient to ensure the recently required level of permeable fish 卵 and absorption rate (\¾ 6幻). In addition, a method of mixing inorganic particles has also been proposed to solve the problem of process clogging only (US Patent Publication No. 2013/0130895), but inorganic particles are separated from the surface of the water absorbent resin particles, increasing dust and reducing the physical properties of the top water-based resin. there is a problem.

【Detailed description of the invention】

【Technical task】

The present invention is a super absorbent polymer that has no pressure/pressure absorption, liquid permeability, and absorption rate suitable for application to thin sanitary materials, while suppressing the generation of dust in the sanitary material manufacturing process and also without clogging in the manufacturing process of the water absorbent resin. It is to provide.

【Technical solution】

In order to solve the above problems, the present invention provides the following super absorbent polymer:

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

It is formed on the base resin powder, the first cross-linking polymer is a high-top water-based resin comprising a surface cross-linking layer containing a second cross-linked polymer additionally cross-linked with a surface cross-linking agent,

Centrifugal separation capacity (0¾：) is 26 or higher,

18 or older,

ego,

The absorption rate measured according to the muscle measurement method is less than 80 seconds, and the size efficiency is more than 30%,

High top water resin.

In the present invention, no pressure/pressure absorption amount suitable for application to a thin sanitary material,

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In order to provide a super absorbent polymer that has flowability and absorption rate, suppresses the generation of dust in the sanitary material manufacturing process, and does not clog during the manufacturing process of the absorbent resin. It is confirmed that the above effects can be achieved when hydrophilic inorganic particles and hydrophobic inorganic particles are used for surface crosslinking and post-treatment thereof.

Hereinafter, the present invention will be described in detail.

Super absorbent polymer

The water-soluble ethylenically unsaturated monomer constituting the additive first crosslinked polymer may be any monomer commonly used in the production of a super absorbent polymer. As a non-limiting example, the water-soluble ethylenically unsaturated monomer may be a compound represented by the following Formula 1:

[Formula 1]

· 1

In Formula 1,

¾ is an alkyl group having 2 to 5 carbon atoms containing an unsaturated bond,

II 1 is a hydrogen atom, a monovalent or divalent metal, an ammonium group or an organic amine salt.

Preferably, the monomer is acrylic acid, methacrylic acid, and these acids

It may be one or more selected from the group consisting of monovalent metal salts, divalent metal salts, ammonium salts and organic amine salts. Thus, when acrylic acid or its salt is used as a water-soluble ethylenically unsaturated monomer, it is advantageous because a super absorbent polymer with improved water absorption can be obtained. In addition, the above monomers include maleic anhydride, fumaric acid, crotonic acid, itaconic acid, 2-acryloylethane sulfonic acid, 2-methacryloylethanesulfonic acid, 2-(meth)acryloylpropanesulfonic acid or 2-(meth). Acrylamide-2 -methyl propane sulfonic acid, (meth)acrylamide,
(meth)acrylate, 2 -hydroxyethyl

(Meth)acrylate, 2-hydroxypropyl (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, polyethylene glycol (meth)acrylate, (_dimethylaminoethyl (meth)acrylate, uh, non- Dimethylaminopropyl (meth)acrylamide, etc. can be used.

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Here, the water-soluble ethylenically unsaturated monomer may have an acidic group, and at least a part of the acidic group may be neutralized. Preferably, the monomer partially neutralized with an alkaline substance such as sodium hydroxide, potassium hydroxide, ammonium hydroxide, etc. may be used.

At this time, the degree of neutralization of the monomer may be 40 to 95 mol%, or 40 to 90 mol%, or 45 to 85 mol%. The range of the degree of neutralization may vary depending on the final physical properties, but if the degree of neutralization is too high, the neutralized monomer may be precipitated and the polymerization may be difficult to proceed smoothly. It can exhibit properties such as elastic rubber that are difficult to handle.

Preferably, the surface crosslinked layer includes hydrophilic inorganic particles, and the surface of the surface crosslinked layer includes hydrophobic inorganic particles. That is, the surface crosslinking layer includes a second crosslinked polymer and hydrophilic inorganic particles whose surface of the base resin powder is additionally crosslinked through a surface crosslinking agent, and a surface crosslinking agent and a surface crosslinking method will be described later. In addition, hydrophobic inorganic particles are included on the surface crosslinked layer.

As the hydrophilic inorganic particles, silica particles or metal oxide particles may be used. The metal oxide particles may be aluminum oxide particles or titanium oxide particles. The hydrophilic inorganic particles are those of silica particles or metal oxide particles that have not been subjected to any chemical treatment, and the surfaces thereof exhibit hydrophilicity.

The hydrophobic inorganic particles are inorganic particles that exhibit hydrophobicity by treating the surface of silica particles or metal oxide particles with a compound having a hydrophobic group, specifically, a compound of siloxane, silane, or silazane. Preferably, the surface of the hydrophobic inorganic particles is hexamethyldisilazane (1 16 X 311161 :1 17 1 (11 1 32 6 ), polydimethylsiloxane ( 0 1 ⌀ 11161 :) 17 1 1 ( ¾31½ ) or Dimethyldichlorosilane

(!1161; 1171 (1 11101'0 18116)). That is, the hydrophobic inorganic particles are surface-treated with a compound having a hydrophobic group on the surface of the hydrophilic inorganic particles.

In addition, the hydrophilic inorganic particles or hydrophobic inorganic particles may have a specific surface area of ​​5 to 500
450 or 50 to 400 mi 2 , respectively.

On the other hand, the superabsorbent polymer according to the present invention has a centrifugal water retention capacity (CRC) of 26 g/g or more for 30 minutes in physiological saline (0.9 wt% sodium chloride aqueous solution). The centrifugal water holding capacity means the ability to retain moisture absorbed by the super absorbent polymer as it is. The specific measurement method thereof is more specific in the following examples.

Preferably, the centrifugation water holding capacity is 27 g/g or more, or 28 g/g or more. The centrifugal water holding capacity is higher as the value is higher, and theoretically there is no upper limit, but, for example, 45 g/g or less or 44 g/g or less.

In addition, the super absorbent polymer according to the present invention has an absorption capacity (0.7AUP) under pressure of 0.7 psi of 18 g/g or more. The 0.7AUP refers to the amount of brine absorbed for 1 hour under pressure of 0.7 psi, which refers to the total amount of water that the superabsorbent polymer can absorb. The specific measurement method thereof is further specified in the following examples.

Preferably, the 0.7AUP is 19 g/g or more, or 20 g/g or more. In addition, since 0.7AUP of the additive value is superior as the value increases, there is no theoretical upper limit, but, for example, it is 29 g/g or less, or 28 g/g or less.

In addition, the super absorbent polymer according to the present invention has a Permeability Dependent Absorption Under Pressure (PDAUP) of 15 g/g or more. The PDAUP is similar to the show, but by increasing the amount of super absorbent polymer to be measured

It means the amount of brine absorbed in 1 hour, and evaluates AUP considering liquid permeability. The specific measurement method thereof is more specific in the following examples.

Preferably, the PDAUP is 15 g/g or more, or 16 g/g or more. In addition, since the PDAUP is superior as its value is higher, there is no theoretical upper limit, but for example, it is 24 g/g or less or 23 g/g or less.

In addition, the super absorbent polymer according to the present invention has an absorption rate measured according to the Vortex measurement method . It is less than 80 seconds. The absorption rate refers to a time when a superabsorbent polymer is added to the physiological saline and stirred, and the vortex of the liquid disappears due to rapid absorption, and means the rapid absorption ability of the superabsorbent polymer. The specific measurement method thereof is more specific in the following examples.

Preferably, the absorption rate measured according to the Vortex measurement method is

It is 80 seconds or less, or 75 seconds or less. In addition, since the saw speed measured according to the Vortex measurement method is superior as its value decreases, the theoretical lower limit is 0 seconds, but, for example, 25 seconds or more, or 30 seconds or more.

In addition, the super absorbent polymer according to the present invention has an ant l eaking efficiency of 30% or more. The ant i caking efficiency is to evaluate the degree of hardening of each other when storing the super absorbent polymer, and is measured according to Equation 1 below, and a specific measurement method thereof is further specified in the following examples.

[Equation 1]

ant i caking efficiency (%) = (Wi)/(Wi + W 2 ) X 100

In Equation 1,

Wi is a super absorbent polymer 2 for 95 ■ After spraying evenly on the inner diameter glass petr i di sh, moisturize it in a thermo-hygrostat at 40 °C and 80% relative humidity for 1 ◦ minute, take it out and turn it over for 5 minutes It is the weight of the superabsorbent polymer that fell off, and the bib 2 is the weight of the superabsorbent polymer remaining in the glass petr i di sh.

Preferably, the ant leaking efficiency is 35% or more, or 40% or more. In addition, the higher the ant l eaking efficiency, the higher the value, the better, and the theoretical upper limit is 100%, but for example, it is 99% or less, or 98% or less.

Also preferably, the super absorbent polymer according to the present invention has an average particle diameter of 300 to 600
. In addition, preferably, 10 to 90% by weight of a super absorbent polymer having a particle diameter of 300 to 600 _ among the super absorbent polymer according to the present invention is included. In addition, preferably, 10% by weight or more of a super absorbent polymer having a particle diameter of 300 m or less is included in the super absorbent polymer.

In addition, the superabsorbent polymer according to the present invention can suppress the generation of dust in the sanitary material manufacturing process because the degree of dust generation is small, as in the examples to be described later.

Manufacturing method of super absorbent polymer

The present invention provides a method for producing the above-described super absorbent polymer, comprising the following steps:

Cross-polymerizing a water-soluble ethylene-based unsaturated monomer having an acidic group at least partially neutralized in the presence of an internal cross-linking agent to form a hydrogel polymer containing the first cross-linking polymer (Step 1);

Coarse pulverization, drying, and pulverization of the hydrogel polymer to prepare a base resin powder (step 2);

In the presence of a surface crosslinking liquid containing hydrophilic inorganic particles, heat-treating the base resin powder to crosslink the surface to produce super absorbent polymer particles (step 3), and

Applying hydrophobic inorganic particles to the super absorbent polymer particles (step 4).

Hereinafter, the above manufacturing method for each step will be described in detail.

(Step 1)

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Step 1 is a step of forming a hydrogel polymer, a step of cross-polymerizing a monomer composition containing a water-soluble ethylenically unsaturated monomer having an acidic group at least partially neutralized in the presence of an internal crosslinking agent.

At this time, the water-soluble ethylenically unsaturated monomer is as described above. In addition, the concentration of the water-soluble ethylenically unsaturated monomer in the monomer composition may be appropriately adjusted in consideration of the polymerization time and reaction conditions, and may be preferably 20 to 90% by weight, or 40 to 65% by weight. This concentration range may be advantageous in order to control the pulverization efficiency during pulverization of the polymer, which will be described later, while eliminating the need to remove the unreacted monomer after polymerization by using the gel effect phenomenon occurring in the polymerization reaction of the high concentration aqueous solution. However, if the concentration of the monomer is too low, the yield of the super absorbent polymer may be lowered. On the contrary, if the concentration of the monomer is too high, there may be problems in the process, such as lowering the pulverization efficiency when part of the monomer is precipitated or the pulverization of the polymerized hydrogel polymer, and the physical properties of the super absorbent polymer may be deteriorated.

In addition, as the internal crosslinking agent, any compound may be used as long as it allows the introduction of a crosslinking bond during polymerization of the water-soluble ethylenically unsaturated monomer. As a non-limiting example, the internal crosslinking agent is polyethylene glycol diacrylate, -methylenebisacrylamide, trimethylolpropane tri(meth)acrylate, ethylene glycol di(meth)acrylate, polyethylene glycol (meth)acrylate, propylene glycol Di(meth)acrylate, polypropylene glycol(meth)acrylate, butanedioldi(meth)acrylate, butylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, nucleic acid diol die (Meth)acrylate, triethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, dipentaerythritol pentaacrylate, glycerin tri(meth)acrylic Polyfunctional crosslinking agents such as acrylate, pentaerythritol tetraacrylate, triarylamine, allyl (meth)acrylate, propane diol, ethylene glycol diglycidyl ether, propylene glycol, glycerin, or ethylene carbonate, or two or more May be used together, but is not limited thereto.

These internal crosslinking agents may be added in a concentration of about 0.001 to 1% by weight based on the monomer composition. That is, when the concentration of the internal crosslinking agent is too low, the absorption rate of the resin may be lowered and the gel strength may be weakened, which is not preferable. Conversely, if the concentration of the internal crosslinking agent is too high, the absorption power of the resin may be lowered, making it undesirable as an absorber.

In addition, in step 1, a polymerization initiator generally used in the manufacture of a super absorbent polymer may be included. As a non-limiting example, as the polymerization initiator, a thermal polymerization initiator or a photo polymerization initiator may be used depending on the polymerization method, and in particular, a thermal polymerization initiator may be used. However, even by the photopolymerization method, since a certain amount of heat is generated by UV irradiation, and a certain amount of heat is generated according to the progress of the polymerization reaction, which is an exothermic reaction, a thermal polymerization initiator may be additionally included.

As the thermal polymerization initiator, at least one compound selected from the group consisting of a persulfate-based initiator, an azo-based initiator, hydrogen peroxide, and ascorbic acid may be used. Specifically, as the persulfate-based initiator, sodium persulfate (Sodium persul fate; Na 2 S 2 ¾), potassium persulfate (Potassium persul fate;

K 2 S 2 O 8)， Ammonium persulfate (Ammonium persul fate; (NH 4)2 S 2 ¾) etc. are examples. In addition, as an azo initiator, 2, 2 -azobis- (2 -amidinopropane) dihydrochloride (2,2-azobi s (2-ami dinopropane) dihydrochlor ide), 2,2-azobis- (N,N_dimethylene)isobutyramide dihydrochloride (2, 2-azobi s-(N, N-dimethylene) i sobutyr ami dine dihydrochlor ide), 2-(carbamoyl azo)isobutyronitrile (2 -(carbamoylazo) i sobutyloni tr i 1 )， 2, 2 -azobis [2-(2 -imidazoline-2 -yl)propane] dihydrochloride (2， 2-azobi s [2-(2-imidazol) in-2-yl )propane] dihydrochlor ide), 4, 4-azobis- (4-cyanovaleric acid) (4,4-azobi s_(4-cyanovaler ic acid)) and the like. For a wider variety of thermal polymerization initiators, see the Odian book "Pr inciple of

Polymer i zat ion (Wi ley, 1981)" on page 203,

You can refer to it.

As the photopolymerization initiator, for example, benzoin ether, dialkyl acetophenone, hydroxyl alkylketone, phenyl glyoxyl ate, benzyl dimethyl ketal One or more compounds selected from the group consisting of (Benzyl Dimethyl Ketal), acyl phosphine, and alpha-aminoketone (a-aminoketone) may be used. Among them, as a specific example of acylphosphine, a commercially available luci r in TP0, that is, 2, 4,6 -trimethyl-benzoyl-trimethyl phosphine oxide (2,4,6-tr imethy卜 benzoyl-tr imethyl phosphine oxide) lyrics Can be used. A wider variety of photopolymerization initiators are disclosed in Reinhold Schwa lm's book “UV Coat ings: Basics, Recent Developments and New Appl i cat ion (El sevier 2007)” on page 115, which can be referred to.

This polymerization initiator may be added in a concentration of about 0.001 to 1% by weight based on the monomer composition. That is, if the concentration of the polymerization initiator is too low, the polymerization rate may be slowed and a large amount of residual monomer may be extracted in the final product, which is not preferable. Conversely, when the concentration of the polymerization initiator is higher than the above range, the polymer chain forming the network is shortened, so that the content of the water-soluble component increases and the absorption capacity under pressure may decrease, which is not preferable.

In addition, the monomer composition may further contain additives such as a foaming agent, a surfactant, a thickener, a plasticizer, a storage stabilizer, and an antioxidant, if necessary.

And, such a monomer composition may be prepared in the form of a solution in which raw materials such as the above-described monomers are dissolved in a solvent. At this time, the usable solvent may be used without limitation of its composition as long as it can dissolve the aforementioned raw materials. For example, as the solvent, water, ethanol, ethylene glycol, diethylene glycol, triethylene glycol, 1,4-butanediol, propylene glycol, ethylene glycol monobutyl ether, propylene glycol monomethyl ether,

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Propylene glycol monomethyl ether acetate, methyl ethyl ketone, acetone, methyl amyl ketone, cyclohexanone, cyclopentanone, diethylene glycol monomethyl ether, diethylene glycol ethyl ether, toluene, xylene, butyrolactone, carbitol, Methyl cellosolve acetate, -dimethylacetamide, or a mixture thereof may be used.

In addition, the formation of the hydrogel polymer through polymerization of the monomer composition may be carried out by a conventional polymerization method, and the process is not particularly limited. As a non-limiting example, the polymerization method is largely divided into thermal polymerization and photopolymerization according to the type of polymerization energy source, and in the case of performing the thermal polymerization, it can be carried out in a reactor having a stirring axis such as a kneader (Nyokksunra), In the case of photopolymerization, it can be carried out in a reactor equipped with a movable conveyor belt.

For example, the monomer composition may be added to a reactor such as a kneader equipped with a stirring shaft, and hot air may be supplied thereto, or the reactor may be heated to perform thermal polymerization to obtain a hydrogel polymer. At this time, the hydrogel polymer discharged to the reactor outlet according to the shape of the stirring shaft provided in the reactor may be obtained as particles of several millimeters to several centimeters . Specifically , the resulting hydrogel polymer can be obtained in various forms depending on the concentration and injection speed of the monomer composition to be injected, and a hydrogel polymer having a particle diameter of 2 to 50 _ (weight average) can be obtained.

And, as another example, when the photopolymerization of the monomer composition is performed in a reactor equipped with a movable conveyor belt, a sheet-shaped hydrous gel polymer may be obtained. At this time, the thickness of the sheet may vary depending on the concentration of the monomer composition to be injected and the injection speed. In order to ensure the production speed and the like while allowing the entire sheet to be polymerized evenly, it is usually adjusted to a thickness of 0.5 to 5 ( desirable.

At this time, the water content of the hydrogel polymer obtained by this method may be 40 to 80% by weight. Meanwhile, in the entire specification, the ``water content'' refers to the content of water to be charged with respect to the total weight of the hydrogel polymer, and means a value obtained by subtracting the weight of the dried polymer from the weight of the hydrogel polymer. Specifically, it is defined as a value calculated by measuring the weight loss due to moisture evaporation of the polymer pack in the process of drying by raising the temperature of the polymer through infrared heating. At this time, the drying condition is a method of raising the temperature from room temperature to about 18CTC and then maintaining it at 180 °C. The total drying time is set to 20 minutes including 5 minutes of the temperature increase step, and the moisture content is measured.

(Step 2)

The above step . 2 is a step of coarsely pulverizing, low tide, and pulverizing the hydrogel polymer prepared in step 1 to form a base resin powder.

First, the hydrogel polymer prepared in step 1 is coarsely pulverized to prepare a hydrogel polymer having small particles.

At this time, the grinder used is not limited in configuration, but specifically, a vertical type cutter (Vert ical pulver i zer), a turbo cutter, a turbo grinder, and a rotary cutting type grinder (Rotary Cutter mi ll), Cutter mi ll, Disc shredder (Di sc mi ll), Shred crusher, Crusher, Chopper and Di sc cutter It may include any one selected from the group of grinding devices, but is not limited to the above-described example.

At this time, the coarse pulverization step may be pulverized so that the particle diameter of the hydrous gel polymer is about 2 mm to about 10™. Grinding with a particle diameter of less than 2 mm is not technically easy due to the high water content of the hydrogel polymer, and a phenomenon of agglomeration between the pulverized particles may appear. On the other hand, when the particle diameter is pulverized to exceed 10 mm, the effect of increasing the efficiency of the subsequent drying step may be insignificant.

Subsequently, drying is performed on the hydrogel polymer coarsely pulverized as described above. At this time, the drying temperature in the drying step may be 50 to 250 °C. Drying temperature is 50 ° C

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If it is less than, the drying time will be too long and the properties of the finally formed super absorbent polymer may be deteriorated. It may occur, and there is a concern that the physical properties of the finally formed super absorbent polymer may be deteriorated. More preferably, the drying may be performed at a temperature of 150 to 2001:, more preferably 160 to 190° (:). On the other hand, in the case of the drying time, in consideration of process efficiency, etc., it may be performed for 20 minutes to 15 hours, but is not limited thereto.

As long as it is normally used in the drying process, it may be selected and used without limitation of its configuration . Specifically, the drying step may be performed by a method such as hot air supply, infrared irradiation, microwave irradiation, or ultraviolet irradiation. The moisture content of the polymer after proceeding with such a drying step may be 0.05 to 10% by weight.

Then, a step of pulverizing the dried polymer as described above is performed.

It is preferable that the polymer powder obtained after the pulverization step has a particle size of 150 to 850 _ of 90% or more. The grinder used to pulverize into such a particle size is specifically a ball mill 0)^ 1 11), a pin mill ( 11 11), a hammer mill (1 _ 111111), a screw mill (111111), a roll mill ( 1 01 1 111111). ）, disk mill (% 11 1 1 1 1 ),
etc. can be used, but this is not limited to the above example.

And, in order to manage the physical properties of the highly water-soluble resin powder that is finally commercialized after the pulverization step, a separate process of classifying the polymer powder obtained after pulverization according to the particle size may be performed. Preferably, a polymer having a particle diameter of 150 to 850 is classified, and only a polymer powder having such a particle diameter can be commercialized through a surface crosslinking reaction step to be described later. More preferably, it is preferable that the content of the particle size of 150 to 850 / pad in the polymer powder is 90% or more.

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(Step 3)

The step 3 is a step of crosslinking the surface of the base resin prepared in step 2, in the presence of a surface crosslinking liquid containing hydrophilic inorganic particles, by heat-treating the base resin powder to form a superabsorbent resin particle This is the step.

Here, the type of the surface crosslinking agent contained in the surface crosslinking liquid is not particularly limited. As a non-limiting example, the surface crosslinking agent is ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerol polyglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, ethylene Carbonate, ethylene glycol, diethylene glycol, propylene glycol, triethylene glycol, tetraethylene glycol, propane diol, dipropylene glycol, polypropylene glycol, glycerin, polyglycerin, butanediol, heptanediol, nucleic acid diol trimethylol It may be one or more compounds selected from the group consisting of propane, pentaerythritol, sorbitol, calcium hydroxide, magnesium hydroxide, aluminum hydroxide, iron hydroxide, calcium chloride, magnesium chloride, aluminum chloride, and iron chloride.

At this time, the content of the surface crosslinking agent may be appropriately adjusted according to the type or reaction conditions thereof, and preferably may be adjusted to 0.001 to 5 parts by weight based on 100 parts by weight of the base resin. If the content of the surface crosslinking agent is too low, the surface crosslinking agent may not be properly introduced, and the physical properties of the final superabsorbent polymer may be deteriorated. On the contrary, if an excessively large amount of the surface crosslinking agent is used, the absorbency of the superabsorbent polymer may be rather lowered due to excessive surface crosslinking reaction, which is not preferable.

In addition, the surface crosslinking solution is water, methanol, ethanol, ethylene glycol, diethylene glycol, triethylene glycol, 1,4-butanediol, propylene glycol, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monomethyl ether Acetate, methyl ethyl ketone, acetone, methyl amyl ketone, cyclohexanone, cyclopentanone, diethylene glycol monomethyl ether, 2019/117418 1»（：1^1{2018/008983

Diethylene glycol ethyl ether, toluene, xylten, butyrolactone, carbitol, methyl cellosolve acetate, and may further include one or more solvents selected from the group consisting of -dimethylacetamide. The solvent may be included in an amount of 0.5 to 15 parts by weight based on 100 parts by weight of the base resin.

In addition, the surface crosslinking solution contains hydrophilic inorganic particles.

The hydrophilic inorganic particles are as described above, and are preferably included in an amount of 0.002 to 0.25 parts by weight based on 100 parts by weight of the base resin.

On the other hand, in order to perform the surface crosslinking, a method of mixing the surface crosslinking solution and the base resin in a reaction tank, a method of spraying a surface crosslinking solution to the base resin, and a surface crosslinking with the base resin in a continuously operated mixer. A method of continuously supplying and mixing the liquid may be used.

Preferably, in the additive surface crosslinking, the base resin powder is heated to 180° (^
for 10 to 50 minutes, and heat treated at 180 or higher for 10 to 50 minutes to crosslink the surface. That is, the temperature range for surface crosslinking is substantially adjusted in two steps, and surface crosslinking is induced together with the hydrophilic inorganic particles to improve the physical properties of the highly water-based resin. The second temperature section is to be maintained above 180 °0, preferably 180 to maintain it.

(Step 4)

Step 4 is a step of applying hydrophobic inorganic particles to the super absorbent polymer particles prepared in step 3.

The hydrophobic inorganic particles are as described above. It is preferable to use 0.001 to 0.15 parts by weight of the hydrophobic inorganic particles based on 100 parts by weight of the super absorbent polymer particles.

【Effects of the Invention】

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As described above, the super absorbent polymer according to the present invention has a non-pressurized/pressurized absorption amount, liquid permeability, and absorption rate suitable for application to a thin sanitary material, while suppressing the generation of dust in the sanitary material manufacturing process, and There is no clogging phenomenon even in the manufacturing process.

【Best mode for implementing the invention】

Hereinafter, preferred embodiments are presented to aid in understanding the present invention. However, the following examples are for illustrative purposes only, and are not intended to limit the present invention.

Example 1

(Step 1)

100 parts by weight of acrylic acid, polyethylene glycol diacrylate (weight average molecular weight: 500 2 / 1) 0.2 parts by weight and ethoxylated trimethylolpropane triacrylate (weight average molecular weight: ~700 § ^ 01 ) 0.1 A monomer solution was prepared by mixing parts by weight and 0.01 parts by weight of 11¾ 0恨£ 819 as a photoinitiator. Subsequently, while continuously supplying the monomer solution to a quantitative pump, 160 parts by weight of a 24% sodium hydroxide aqueous solution was continuously line-mixed to prepare an aqueous monomer solution. At this time, the temperature increased by the neutralization heat was adjusted to 401:. In addition, 6 parts by weight of a 4% sodium persulfate aqueous solution was continuously line-mixed, and then continuously supplied to a continuous polymerization reactor having a flat polymerization belt having weirs at both ends. After that, 1 was irradiated for 1 minute, and thermal polymerization was further performed for 2 minutes to prepare a hydrogel.

(Step 2)

After cutting the hydrogel prepared in step 1 to have an average size of about 300 1 ™ or less, add a fine powder reassembly to a pulverizer (a porous plate having a plurality of holes having a diameter of 11 ™) It was added and pulverized. Here, the fine powder reassembly was used as the fine powder reassembly prepared in step 4 below, and the input ratio was 18% compared to the hydrous gel.

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(Step 3)

The hydrogel pulverized in step 2 was dried in a dryer capable of transferring air volume up and down. To make the moisture content of the dried powder less than about 2%, the hot air (^ 1· ) of 1801: flows from the bottom to the top for 15 minutes, and then flows from the top to the bottom for 15 minutes to dry the hydrous gel evenly. Made it.

(Step 4)

The resin dried in step 3 was pulverized with a grinder and then classified to obtain a base resin having a size of 150 to 850. On the other hand, through the classification, polymer particles having a particle diameter of less than 150, were granulated with water, and used as the fine powder reassembled in step 2 described above.

(Step 5)

100 parts by weight of the base resin prepared in step 4, 3 parts by weight of water, 3 parts by weight of methanol, 0.5 parts by weight of 1,3-propanediol, and hydrophilic inorganic particles Rosi 203 particles 犯射 specific surface area 130 taste 2 / §） 0.1 parts by weight of the mixed crosslinking agent solution was mixed, and then the temperature was raised from room temperature to 180° (:) for 25 minutes, and the surface crosslinking reaction was carried out by holding 180° (:) for 30 minutes. Then, the obtained product was cooled and classified to obtain a crosslinked superabsorbent polymer having a particle diameter of 150 to 850.

(Step 6)

A super absorbent polymer was prepared by applying a specific surface area of ​​140 and 0.05 parts by weight of
the
particles treated with a hydrophobic inorganic particle on the surface of the superabsorbent polymer based on 100 parts by weight of the superabsorbent resin particles prepared in step 5
using a mixer.

Examples 2 to 8

Prepared in the same manner as in Example 1, but using hydrophilic inorganic particles, surface crosslinking reaction, and hydrophobic inorganic particles as shown in Table 1 below, each super absorbent polymer was prepared.

[Table 1]

Comparative Examples 1 to 8

Prepared in the same manner as in Example 1, but using hydrophilic inorganic particles, surface crosslinking reaction, and hydrophobic inorganic particles as shown in Table 2 below, each super absorbent polymer was prepared.

【Table 2】

Experimental Example: Evaluation of properties of super absorbent polymer

The physical properties of the super absorbent polymer prepared in Examples and Comparative Examples were evaluated by the following method. ·

(1) Centri fuge Retent ion Capacity (CRC)

European Di sposabl es and Nonwovens Associ at ion,

EDANA) In accordance with the standard EDANA WSP 241.3, for the superabsorbent polymers of Examples and Comparative Examples, centrifugal water retention capacity (CRC) was measured according to the absorption rate under no load.

Specifically, resin W 0 ( g, 0.1 g) of Examples and Comparative Examples was evenly placed in a nonwoven bag and sealed, and then immersed in physiological saline solution of 0.9 wt% sodium chloride aqueous solution at room temperature. After 30 minutes, the bags were centrifuged and dried for 3 minutes with 250 G, and the mass W 2 ( g) of the bags was measured. In addition, after performing the same operation without using a super absorbent polymer, the mass at that time was measured.

Using each mass thus obtained, CRC (g/g) was calculated according to the following equation.

CRC(g/g) = {[W 2( g)-Wi(g)-Wo(g)]/Wo(g)}

(2) Absorbing under Pressure (AUP)

The absorbency under pressure (AUP) of 0.7 ps i for physiological saline of the superabsorbent polymers of Examples and Comparative Examples was measured according to the EDANA method WSP 242.2.

Specifically, a stainless steel 400 mesh screen was mounted on the bottom of a plastic cylinder having an inner diameter of 60 mm. Then, a super absorbent polymer W 0 ( g, 0.9 g) to measure the absorbency under pressure was evenly sprayed on the screen at room temperature and humidity of 5OT . Subsequently, a piston capable of uniformly applying a load of 4.83 kPa (0.7 ps i) was added to the super absorbent polymer. At this time, the outer diameter of the piston is slightly smaller than 60 mm, so there is no gap with the inner wall of the cylinder, and the piston is used to move freely up and down. Then, the weight Wi (g) of the thus prepared device was immediately determined.

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Then, a glass filter having a diameter of 90 1™ and a thickness of 5 _ was placed on the inside of a 150 _ diameter PET dish, and 0.9% by weight of physiological saline was poured into the petro dish. At this time, the physiological saline was poured until the water surface of the physiological saline was level with the upper surface of the glass filter. Then, one sheet of filter paper having a diameter of 90 ■ was placed on the glass filter .

Next, the prepared device was placed on the filter paper so that the super absorbent polymer in the device was swollen by physiological saline under load. After 1 hour, the weight of the device containing the swollen water-based resin was immediately determined. The pressure absorption capacity was calculated according to the following equation using the weight determined in this way.

() = [¾)-½)] / ½)

(3) Pressurized liquidity ^0/^)

Pressure barrel-component in the Examples and Comparative Examples and the water absorbent resin eulmyo saesyo ^ ssae 3

It was measured according to the method of 243. 1.

Specifically, a 400 stainless steel wire mesh was mounted on the bottom of a plastic cylinder having an inner diameter of 60 ■ .
Piston (1)^1:011), which can evenly spray water-absorbent resin) (for 5.0) on the wire mesh under the conditions of room temperature and humidity 50%, and apply an additional 4.83 load evenly, has an outer diameter slightly less than 60 111111. It is small and there is no gap with the inner wall of the cylinder, and the vertical movement is not disturbed. At this time, the weight (yo) of the device was measured. A glass filter having a diameter of 90· and a thickness of 5· was placed on the inside of a 150 1^1 PET dish, and a physiological saline solution composed of 0.90 wt% sodium chloride was at the same level as the upper surface of the glass filter. One sheet of filter paper with a diameter of 90™ was mounted on it. The measuring device was placed on a filter paper, and the liquid was absorbed for 1 hour under load. After 1 hour, the measuring device was lifted and
measured. Pressurized absorption capacity was calculated according to Equation 3 below.

· ( § / ¾) = {(¾(-)}/ ¾)

(4) Absorption rate (root point ^ 1116)

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

Specifically, the absorption rate (or vortex time) is a superabsorbent polymer (2 g) in 50 mL of physiological saline at 23 ° C to 24 ° C, and a magnetic bar (diameter 8 mm, length

30_) was stirred at 600 rpm, and the time until the vortex disappeared was measured in seconds.

(5) Ant leaking efficiency

The anti caking efficiency of the super absorbent polymers of Examples and Comparative Examples was measured.

Specifically, a super absorbent polymer (2 g) was evenly distributed in a 95 mm diameter glass Petri-dish. Petri-dish was placed in a constant temperature and humidity chamber maintained at a temperature of 40C and a relative humidity of 80%, and allowed to stand for 10 minutes, and Petri-dish was inverted. After 5 minutes, the weight of the resin dropped on the floor () and the weight (¾) of the super absorbent polymer remaining in the Petri-dish were measured, and calculated by the following equation.

ant l eaking efficiency (%) = (W)/(ffi + ¾) X 100

(6) Dust Number

Using the Dust view II device of Palas, Germany, the Dust Number of the super absorbent polymer (30) of Examples and Comparative Examples was measured.

The results measured as described above are shown in Table 3 below.

【Table 3】

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【Scope of claim】

[Claim 1]

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

As a water-based resin formed on the base resin powder, the first cross-linking polymer comprising a surface cross-linking layer comprising a second cross-linking polymer additionally cross-linked via a surface cross-linking agent,

The centrifugal separation capacity (CRC) is 26 g/g or more,

0.7 psi pressure absorption capacity (0.7AUP) is 18 g/g or more,

Pressurized liquid permeability (PDAUP) is more than 15 g/g,

The absorption rate measured according to the Vortex measurement method is 80 seconds or less, and the ant l eaking efficiency is 30% or more,

High top water resin.

[Claim 2]

The method of claim 1,

The surface crosslinked layer includes hydrophilic inorganic particles, and includes hydrophobic inorganic particles on the surface of the surface crosslinked layer,

Super absorbent polymer.

【Claim 3】

The method of claim 1,

The dust number of the super absorbent polymer is 3 or less,

Highly water-soluble resin.

[Claim 4]

The method of claim 1,

The centrifugation water holding capacity (CRC) is 28 g/g or more,

Super absorbent polymer.

[Claim 5]

The method of claim 1,

0.7 ps i pressure absorption capacity (0.7AUP) is more than 20 g/g,

High top water resin.

[Claim 6]

The method of claim 1,

The pressurized liquid permeability (PDAUP) is 16 g/g or more,

Super absorbent polymer.

[Claim 7]

The method of claim 1,

The absorption rate measured according to the Vortex measurement method is 75 seconds or less, high-top water-based resin.

【Claim 8】

The method of claim 1,

The ant l eaking efficiency is measured according to Equation 1 below,

Super absorbent polymer:

[Equation 1]

ant i caking efficiency (%) = (Wi)/(Wi + W 2) X 100

In Equation 1,

Wi is a super absorbent polymer 2, sprayed evenly on a 95 mm inner diameter glass petr i di sh, moistened for 10 minutes in a thermo-hygrostat at 40 ° C and 80% relative humidity, and then put it upside down for 5 minutes and then dropped it on the floor. Is the weight of the super absorbent polymer,

W2 is the weight of the high-top water resin remaining in the glass petr i di sh.

[Claim 9]

The method of claim 1,

The ant l eaking efficiency is 40% or more,

High knot aqueous resin.

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【Claim 10】

Cross-polymerizing a water-soluble ethylene-based unsaturated monomer having an acidic group at least partially neutralized in the presence of an internal cross-linking agent to form a hydrogel polymer containing the first cross-linking polymer (step 1);

Coarse grinding, drying, and grinding the hydrogel polymer to prepare a base resin powder (Step 2);

In the presence of a surface crosslinking liquid containing hydrophilic inorganic particles, heat-treating the base resin powder to crosslink the surface to produce super absorbent polymer particles (step 3), and

Applying hydrophobic inorganic particles to the super absorbent polymer particles (step

Including 4),

Method for producing a super absorbent polymer.

【Claim 11】

The method of claim 10,

The hydrophilic inorganic particles are silica particles or metal oxide particles, a method for producing a super absorbent polymer.

【Claim 12】

The method of claim 10,

In the step 3, the base resin powder is heated to 1801: for 10 to 50 minutes, and heat-treated at 1801: or higher for 10 to 5 ◦ minutes to crosslink the surface,

Manufacturing method of super absorbent polymer.

【Claim 13】

The method of claim 10,

The hydrophobic inorganic particles are particles obtained by treating the surface of the silica particles or metal oxide particles with a compound having a hydrophobic group,

Method for producing a super absorbent polymer.

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【Claim 14】

The method of claim 10,

The hydrophilic inorganic particles are used in an amount of 0.002 to 0.25 parts by weight based on 100 parts by weight of the base resin,

5 Manufacturing method of super absorbent polymer.

【Claim 15】

The method of claim 10,

The hydrophobic inorganic particles are used in an amount of 0.001 to 0.15 parts by weight of 10 based on 100 parts by weight of the base resin ,

Manufacturing method of super absorbent polymer.