A Composition of Super Absorbent Polymer and a Preparation Method Thereof

TECHNICAL FIELD

The present disclosure relates to a composition of super absorbent polymer and a preparation method thereof. Specifically, the present disclosure relates to a composition of super absorbent polymer having deodorization performance and odor-prevention performance and a preparation method thereof.

BACKGROUND ART

Super absorbent polymer (SAP) is synthetic polymer material that can absorb moisture of 500 to 1000 times of self-weight, and is also named differently as super absorbency material (SAM), absorbent gel material (AGM), etc. according to developing companies. The superabsorbent polymer began to be commercialized as sanitary items, and currently, it is being widely used as water-holding material for soil, water stop material for civil engineering and architecture, sheets for raising seedling, freshness preservatives in the field of food circulation, fomentation material, etc., besides hygienic goods such as a disposable diaper for children, and the like.

In most cases, such superabsorbent polymer is being widely used in the field of hygienic goods such as diapers or sanitary pad, and the like. In the hygienic goods, the superabsorbent polymer is generally spread in pulp and included. However, recently, in an effort to provide hygienic goods such as diapers having thinner thickness, development of diapers having decreased pulp content, or even pulpless diapers in which pulp is not used at all, is being actively progressed.

As such, in the case of hygienic goods having decreased pulp, or pulpless hygienic goods, superabsorbent polymer is included at relatively high ratio, and such superabsorbent polymer particles are included inevitably in multilayers. In order for the entire superabsorbent polymer particles included in multilayers to more efficiently absorb liquid such as urine, the superabsorbent polymer should basically exhibit high absorption performance and absorption speed. Moreover, absorbed liquid should not be leaked even under external pressure, and besides, the superabsorbent polymer should have permeability so as to properly maintain the original shape even when it absorbs liquid and is swollen.

Thus, a lot of researches are being progressed, such as surface crosslinking, for improving basic absorption force and water holding capacity.

However, super absorbent polymer may be used in hygienic products, and in this case, due to the odor of absorbed liquids such as excretion of human and pet, afterfeel may be degraded. Thus, there is an increasing demand for inhibition of odor of super absorbent polymer, as well as basic properties such as absorption force and water holding capacity. Thus, there is a demand for the preparation of super absorbent polymer having deodorization performance.

DETAILED DESCRIPTION OF THE INVENTION
Technical Problem

It is an object of the technology to provide a composition of super absorbent polymer having deodorization performance and a method for preparing the same.

More specifically, it is an object of the technology to provide a composition of super absorbent polymer and a method for preparing the same, said composition having excellent deodorization performance while minimizing property deterioration of super absorbent polymer, by mixing deodorization material with super absorbent polymer while controlling combination and mixing ratios thereof.

Technical Solution

In order to achieve the object, there is provided a composition of super absorbent polymer comprising:

- super absorbent polymer comprising a base resin comprising crosslinked polymer in which acrylic acid-based monomers having at least partially neutralized acid groups and an internal crosslinking agent are crosslinked, and a surface crosslink layer formed on the surface of the base resin, in which the crosslinked polymer is additionally crosslinked by a surface crosslinking agent; and
- sulfur-containing amino acid and metal iodide salt.

There is also provided a method for preparing a composition of super absorbent polymer, comprising steps of:

- conducting crosslinking polymerization of acrylic acid-based monomers having at least partially neutralized acid groups, in the presence of an internal crosslinking agent and a polymerization initiator, to form hydrogel polymer (step 1);
- preparing a base resin comprising crosslinked polymer by drying and grinding the hydrogel polymer (step 2);
- mixing a surface crosslinking solution with the base resin to prepare a mixture (step 3);
- heat treating the mixture to prepare super absorbent polymer in which a surface crosslink layer is formed on the surface of the base resin(step 4); and
- mixing an aqueous solution comprising sulfur-containing amino acid and metal iodide salt with the super absorbent polymer (step 5).

Advantageous Effects

As explained above, the present disclosure provides a composition of super absorbent polymer having excellent deodorization performance, and a preparation method thereof, by applying optimum rates of deodorization materials to super absorbent polymer.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The terms used herein are only to explain specific embodiments, and are not intended to limit the invention. A singular expression includes a plural expression thereof, unless it is expressly stated or obvious from the context that such is not intended. As used herein, the terms “comprise”, “equipped” or “have”, etc. are intended to designate the existence of practiced characteristic, number, step, constructional element or combinations thereof, and they are not intended to preclude the possibility of existence or addition of one or more other characteristics, numbers, steps, constructional elements or combinations thereof.

Although various modifications can be made to the invention and the invention may have various forms, specific examples will be illustrated and explained in detail below. However, it should be understood that these are not intended to limit the invention to specific disclosure, and that the invention includes all the modifications, equivalents or replacements thereof without departing from the spirit and technical scope of the invention.

Hereinafter, a composition of super absorbent polymer and a preparation method thereof according to specific embodiments of the invention will be explained more detail.

But first, technical terms used herein are only for mentioning specific embodiments, and are not intended to limit the invention. And, the singular expressions used herein include the plural expressions thereof, unless they are differently expressed contextually.

For reference, as used herein, “super absorbent polymer” means super absorbent polymer itself, or is used to include the polymer made suitable for productization through additional processes, for example, surface crosslinking, fine reassembly, drying, grinding, classification, and the like, according to the context.

And, as used herein, “base resin” or “base resin powder” means particle or powder obtained by drying and grinding polymer polymerized from acrylic acid-based monomers, before passing through surface modification or surface crosslinking step as described below.

(Composition of Super Absorbent Polymer)

According to one embodiment of the invention, there is provided a composition of super absorbent polymer.

The composition of super absorbent polymer comprises: super absorbent polymer comprising a base resin comprising crosslinked polymer in which acrylic acid-based monomers having at least partially neutralized acid groups and an internal crosslinking agent are crosslinked, and a surface crosslink layer formed on the surface of the base resin, in which the crosslinked polymer is additionally crosslinked by a surface crosslinking agent; and sulfur-containing amino acid and metal iodide salt.

The acrylic acid-based monomers may be any monomers commonly used in the preparation of superabsorbent polymer. As non-limiting examples, the acrylic acid-based monomer may be a compound represented by the following Chemical Formula 1:

R¹—COOM¹ [Chemical Formula 1]

In the Chemical Formula 1,

- R₁is a C2-5 alkyl group comprising an unsaturated bond,
- M¹is a hydrogen atom, a monovalent or divalent metal, an ammonium group or an organic amine salt.

Preferably, the monomers may be one or more selected from the group consisting of acrylic acid, methacrylic acid, and monovalent metal salts, divalent metal salts, ammonium salts and organic amine salts thereof.

The acrylic acid-based monomers may have acid groups, and at least a part of the acid groups may be neutralized. Preferably, the monomers partially neutralized with alkali substance such as sodium hydroxide, potassium hydroxide, ammonium hydroxide and the like, may be used.

Wherein, the degree of neutralization of the monomers may be 40 to 95 mol %, or 40 to 80 mol %, or 45 to 75 mol %. Although the range of the neutralization degree may vary according to the final properties, if the neutralization degree is too high, neutralized monomers may be precipitated, and thus, it may be difficult to smoothly progress polymerization, and to the contrary, if the neutralization degree is too low, absorption force of polymer may be significantly lowered, and it may exhibit elastic rubber-like properties, which is difficult to handle.

Meanwhile, the crosslinking polymerization is conducted in the presence of a crosslinking agent (“internal crosslinking agent”) so as to improve the properties of polymer obtained by the polymerization of the acrylic acid-based monomers. The crosslinking agent is for internal crosslinking of hydrogel polymer, and is used separately from “a surface crosslinking agent” as described below.

As the internal crosslinking agent, any compounds can be used as long as they enable the introduction of crosslink during polymerization of the acrylic acid-based monomers. As non-limiting examples, as the internal crosslinking agent, multifunctional crosslinking agents such as N,N′-methylenebisacrylamide, trimethylolpropane tri(meth)acrylate, ethyleneglycol di(meth)acrylate, polyethyleneglycol (meth)acrylate, propyleneglycol di(meth)acrylate, polypropyleneglycol (meth)acrylate, butanediol di(meth)acrylate, butyleneglycol di(meth)acrylate, diethyleneglycol di(meth)acrylate, hexanediol di(meth)acrylate, triethyleneglycol di(meth)acrylate, tripropyleneglycol di(meth)acrylate, tetraethyleneglycol di(meth)acrylate, dipentaerythritol pentaacrylate, glycerin tri(meth)acrylate, pentaerythritol tetraacrylate, triarylamine, ethyleneglycol diglycidyl ether, propyleneglycol, glycerin, or ethylenecarbonate may be used alone or in combinations, but it is not limited thereto.

Such an internal crosslinking agent may be used at the concentration of 0.001 to 1 wt %, or 0.01 to 0.8 wt %, or 0.1 to 0.7 wt %, based on the monomer composition. If the concentration of the internal crosslinking agent is too low, absorption speed of polymer may decrease, and gel strength may become weak. To the contrary, if the concentration of the internal crosslinking agent is too high, absorption force of superabsorbent polymer may decrease, and it may not be preferable as an absorbent.

Besides, the monomer composition may further comprise additives such as a thickener, a plasticizer, a preservation stabilizer, an antioxidant, etc., as necessary.

The surface crosslink layer is formed by additional crosslinking of the crosslinked polymer by a surface crosslinking agent, wherein the surface crosslinking agent is not specifically limited as long as it is commonly used for surface crosslinking of super absorbent polymer and is a compound capable of reacting with the functional groups of the polymer.

Preferably, in order to improve the properties of produced super absorbent polymer, as the surface crosslinking agent, one or more selected from the group consisting of polyhydric alcohol compounds; epoxy compounds; polyamine compounds; haloepoxy compounds; condensation products of haloepoxy compounds; oxazoline compounds; mono-, di- or polyoxazolidinone compounds; cyclic urea compounds; multivalent metal salts; and alkylene carbonate compounds may be used.

Specifically, as the examples of the polyhydric alcohol compound, one or more selected from the group consisting of mono-, di-, tri- tetra- or polyethylene glycol, monopropylene glycol, 1,3-propanediol, dipropylene glycol, 2,3,4-trimethyl-1,3-pentanediol, polypropylene glycol, glycerol, polyglycerol, 2-butene-1,4-diol, 1,4-butanediol, 1,3-butanediol, 1,5-pentanediol, 1,6-hexandiol, and 1,2-cyclohexanedimethanol may be used.

And, as the epoxy compound, ethylene glycol diglycidyl ether and glycidol, and the like may be used, and as the polyamine compound, one or more selected from the group consisting of ethylenediamine, diethylenetriamine, triethylenetriamine, tetraethylenepentamine, pentaethylenehexamine, polyethyleneamine, and polyamidepolyamine may be used.

And, as the haloepoxy compound, epichlorohydrin, epibromohydrin, and α-methylepichlorohydrin may be used, and as the mono-, di- or polyoxazolidinone compound, for example, 2-oxazolidinone, and the like may be used.

And, as the alkylene carbonate compound, ethylene carbonate, and the like may be used. These compounds may be used alone or in combinations. Meanwhile, in order to increase the efficiency of the surface crosslinking process, among these surface crosslinking agents, one or more kinds of C2-10 polyhydric alcohol compounds may be included.

The content of the surface crosslinking agent added may be appropriately selected according to the kind of the surface crosslinking agent added and reaction conditions, but commonly, it may be used in the amount of about 0.001 to about 5 parts by weight, preferably about 0.01 to about 3 parts by weight, more preferably about 0.05 to about 2 parts by weight, based on 100 parts by weight of the polymer.

If the content of the surface crosslinking agent is too small, a surface crosslinking reaction may hardly occur, and if it is greater than 5 parts by weight, based on 100 parts by weight of the polymer, due to the progression of excessive surface crosslinking reaction, absorption capacity and properties may be deteriorated.

Meanwhile, the surface crosslinking agent may further comprise inorganic materials. As such inorganic material, one or more selected from the group consisting of silica, clay, alumina, silica-alumina composite material, titania, zinc oxide and aluminum sulfate may be used. The inorganic material may be used in the form of powder or liquid, and particularly, alumina powder, silica-alumina powder, titania powder, or a nano silica solution. And, the inorganic material may be used in the content of about 0.001 to about 1 part by weight, based on 100 parts by weight of the base resin.

And, the surface crosslinking agent may further comprise a thickener. If the surface of base resin powder is additionally crosslinked in the presence of a thickener, property deterioration may be minimized even after grinding. Specifically, as the thickener, one or more selected from polysaccharide and hydroxy-containing polymer may be used. As the polysaccharide, a gum-based thickener and a cellulose-based thickener, and the like may be used. As specific examples of the gum-based thickener, xanthan gum, arabic gum, karaya gum, tragacanth gum, ghatti gum, guar gum, locust bean gum and psyllium seed gum, and the like may be mentioned, and as specific examples of the cellulose-based thickener, hyrdoxypropylmethylcellulose, carboxymethylcellulose, methylcellulose, hydroxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, hydroxyethylmethylcellulose, hydroxymethylpropylcellulose, hydroxyethylhydroxypropylcellulose, ethylhydroxyethylcellulose and methylhydroxypropylcellulose, and the like may be mentioned. Meanwhile, as specific examples of the hydroxy-containing polymer, polyethyleneglycol and polyvinylalcohol, and the like may be mentioned.

The sulfur-containing amino acid and metal iodide salt may be included respectively in the content of 0.1 to 1.5 parts by weight and 0.001 to 0.05 parts by weight, based on 100 parts by weight of the base resin. The sulfur-containing amino acid may be added to super absorbent polymer to endow deodorization property. Specifically, the sulfur-containing amino acid may comprise one or more selected from the group consisting of cysteine, cystine, and methionine. More specifically, the sulfur-containing amino acid may comprise cysteine or methionine.

The metal iodide salt has the form in which one or more selected from the group consisting of CuI, NaI and KI are dissolved together with I₂in water. The metal iodide salt may be also added to super absorbent polymer to endow deodorization property, like sulfur-containing amino acid.

The sulfur-containing amino acid may chemically react with malodorous substance to capture it. Malodorous substance generally has low molecular weight, and by the reaction with sulfur-containing amino acid, it may become substance with decreased or no odor, thus effectively removing odor. Particularly, the sulfur-containing amino acid is effective for reducing odors of aldehyde and ketone compounds.

The metal iodide salt oxidizes malodorous substance to remove it, and it acts on most malodorous substances and works in general.

The sulfur-containing amino acid may be included in the content of 0.1 to 1.5 parts by weight, based on 100 parts by weight of the base resin. Specifically, the sulfur-containing amino acid may be included in the content of 0.1 parts by weight or more, 0.13 parts by weight or more, or 0.15 parts by weight or more and 1.5 parts by weight or less, 1.2 parts by weight or less, 1.0 parts by weight or less, 0.8 parts by weight or less, 0.6 parts by weight or less, 0.5 parts by weight or less, 0.4 parts by weight or less, 0.3 parts by weight or less, or 0.2 parts by weight or less.

The metal iodide salt may be included in the content of 0.001 to 0.05 parts by weight, based on 100 parts by weight of the base resin. Specifically, the metal iodide salt may be included in the content of 0.001 parts by weight or more, 0.005 parts by weight or more, 0.01 parts by weight or more, 0.015 parts by weight or more or 0.02 parts by weight or more and 0.05 parts by weight or less, 0.04 parts by weight or less, 0.03 parts by weight or less, or 0.025 parts by weight or less.

If the content of the sulfur-containing amino acid is too small, deodorization property may not be realized, and if it is too large, unique properties of super absorbent polymer may be deteriorated, and there may be a process problem due to incomplete dissolution.

And, if the content of the metal iodide salt is too small, deodorization property may not be sufficiently realized, and if it is too large, unique properties of super absorbent polymer may be deteriorated, and it may be supplied as a solution in the process to increase tailings, and thus, deodorization capacity may decrease to the contrary.

The sulfur-containing amino acid and metal iodide salt are mixed with super absorbent polymer as an aqueous solution in water solvent, and they exist in super absorbent polymer while mixed and physically contained in super absorbent polymer. The metal iodide salt solution may be a solution with metal iodide salt concentration of 1% or less.

And, the base resin may further comprise polymerizable antibacterial monomers in the content of 5 parts by weight or less, based on 100 parts by weight of the acrylic acid-based monomer, thus endowing super absorbent polymer with antibacterial property as well as deodorization property. The polymerizable antibacterial monomer may be in the form of polymerizable quaternary ammonium salt represented by the following Chemical Formula 2.

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In the Chemical Formula 2, R2 and R3 may be substituted or unsubstituted C_1-30alkylene, C_1-30alkoxylene, C_6-30arylene or C_5-30heteroarylene comprising one or more selected from the group consisting of N, O and S and R₄and R₅may be substituted or unsubstituted C_1-30alkyl, C_1-30alkoxy, C_6-30aryl or C_5-30heteroaryl comprising one or more selected from the group consisting of N, O and S.

Specifically, the polymerizable quaternary ammonium salt may be one or more selected from the group consisting of cetethyldimonium bromide, myristyl betaine, and octenidine HCl.

And, the polymerizable antibacterial monomers may be included in the content of 0.5 parts by weight or more, 1 part by weight or more, 1.5 parts by weight or more or 1.8 parts by weight or more and 5 parts by weight or less, 4 parts by weight or less, 3 parts by weight or less, or 2 parts by weight or less, based on 100 parts by weight of the acrylic acid-based monomer. In case antibacterial effect is not aimed, polymerizable antibacterial monomers may not be included, but in case antibacterial effect is aimed, the effect cannot be obtained if the content of polymerizable antibacterial monomers mixed is too small. On the other hand, if the content of polymerizable antibacterial monomers is too large, water holding capacity and absorption capacity required for super absorbent polymer may be deteriorated.

And, zirconium phosphate may be further included in the content of 5.0 parts by weight or less, based on 100 parts by weight of the base resin. Wherein, zirconium phosphate may be previously dry mixed in the step of drying and grinding of the base resin. Namely, zirconium phosphate may be physically dry mixed as solid contents with the base resin before surface crosslinking. Zirconium phosphate is material capable of physically adsorbing malodorous substance. Thus, by further mixing base resin powders with zirconium phosphate, additional deodorization effect may be obtained.

Wherein, the zirconium phosphate may be included in the content of 5.0 parts by weight or less, based on 100 parts by weight of the base resin. The zirconium phosphate is for additional deodorization capacity increase, and may not be included, but in case it is included, it may be specifically included in the content of 0.5 parts by weight or more, 0.8 parts by weight or more, 1.0 parts by weight or more, 1.3 parts by weight or more, 1.5 parts by weight or more, or 1.8 parts by weight or more and 5.0 parts by weight or less, 4.0 parts by weight or less, 3.0 parts by weight or less or 2.0 parts by weight or less. If the content of zirconium phosphate mixed is too small, deodorization effect obtained thereby may be insignificant, and if the content is too large, surface crosslinking may not be sufficiently conducted, and thus, absorbency under pressure, and the like may be deteriorated.

And, the surface crosslink layer may further comprise tannin solids. Tannin may chemically bond with volatile malodorous substance such as aldehyde-based material, thus endowing super absorbent polymer with deodorization performance.

The tannin solids may be included in the content of 0.05 parts by weight or less, based on 100 parts by weight of the base resin. The tannin is intended to endow super absorbent polymer with additional deodorization property, and may not be included, but in case it is included, it may be specifically included in the content of 0.005 parts by weight or more, 0.015 parts by weight or more, or 0.025 parts by weight or more and 0.05 parts by weight or less, 0.04 parts by weight or less or 0.03 parts by weight or less, based on 100 parts by weight of the base resin. If the content of tannin mixed is too small, deodorization effect obtained thereby may be insignificant, and if it is too large, the properties of super absorbent polymer, such as absorption capacity, absorbency under pressure, and the like may be deteriorated.

(Preparation Method of Composition of Super Absorbent Polymer)

According to one embodiment of the invention, there is provided a method for preparing a composition of super absorbent polymer.

The method for preparing a composition of superabsorbent polymer comprises steps of:

- conducting crosslinking polymerization of acrylic acid-based monomers having at least partially neutralized acid groups, in the presence of an internal crosslinking agent and a polymerization initiator, to form hydrogel polymer; preparing a base resin comprising crosslinked polymer by drying and grinding the hydrogel polymer; mixing a surface crosslinking solution with the base resin to prepare a mixture; heat treating the mixture to prepare super absorbent polymer in which a surface crosslink layer is formed on the surface of the base resin; and mixing an aqueous solution comprising sulfur-containing amino acid and metal iodide salt with the super absorbent polymer.

The method for preparing super absorbent polymer largely comprises a step of polymerizing acrylic acid-based monomers to prepare hydrogel polymer, and a step of grinding it. And, in order to improve various properties of super absorbent polymer, the surface of prepared super absorbent polymer is crosslinked.

The present disclosure is aimed at providing a composition of super absorbent polymer having deodorization property, by mixing deodorization material with the surface crosslinked super absorbent polymer.

Hereinafter, the technology will be explained in detail according to steps.

(Step 1)

The step 1 is a step of preparing hydrogel polymer, and specifically, a step wherein a monomer composition comprising acrylic acid-based monomers having at least partially neutralized acid groups is crosslinked to form hydrogel polymer.

The acrylic acid-based monomers may be any monomers commonly used in the preparation of superabsorbent polymer. Specifically, the acrylic acid-based monomer may be a compound represented by the following Chemical Formula 1:

R¹—COOM¹ [Chemical Formula 1]

In the Chemical Formula 1,

- R¹is a C2-5 alkyl group comprising an unsaturated bond,
- M¹is a hydrogen atom, a monovalent or divalent metal, an ammonium group or an organic amine salt.

And, in the present disclosure, in order to endow super absorbent polymer with antibacterial property as well as deodorization property, polymerizable antibacterial monomers may be further included. Specifically, the polymerizable antibacterial monomers may be included in the content of 5 parts by weight or less, based on 100 parts by weight of the acrylic acid-based monomer. The polymerizable antibacterial monomers may be in the form of polymerizable quaternary ammonium salts represented by the following Chemical Formula 2.

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In the Chemical Formula 2, R₂and R₃may be substituted or unsubstituted C_1-30alkylene, C_1-30alkoxylene, C_6-30arylene or C_5-30heteroarylene comprising one or more selected from the group consisting of N, O and S and R₄and R₅may be substituted or unsubstituted C_1-30alkyl, C_1-30alkoxy, C_6-30aryl or C_5-30heteroaryl comprising one or more selected from the group consisting of N, O and S.

Specifically, the polymerizable quaternary ammonium salt may be one or more selected from the group consisting of cetethyldimonium bromide, myristyl betaine, and octenidine HCl.

In the monomer composition, a polymerization initiator commonly used for the preparation of super absorbent polymer may be included.

As the polymerization initiator, a thermal polymerization initiator or a photopolymeirzation initiator may be used according to polymerization method. However, even when photopolymerization is progressed, since a certain amount of heat is generated by UV irradiation, etc., and heat is generated to some degree according to the progression of an exothermic polymerization reaction, a thermal polymerization initiator may be additionally included.

As the photopolymerization initiator, one or more selected from the group consisting of benzoin ether, dialkyl acetophenone, hydroxyl alkylketone, phenyl glyoxylate, benzyl dimethyl Ketal, acyl phosphine, and α-aminoketone may be used. Among them, as specific examples of acyl phosphine, commercially available lucirin TPO, i.e., 2,4,6-trimethyl-benzoyl-trimethyl phosphine oxide may be used. More various photopolymerization initiators are described in Reinhold Schwalm, “UV Coatings: Basics, Recent Developments and New Application (Elsevier 2007)”, page 115, which may be referred to.

And, as the thermal polymerization initiator, one or more selected from the group consisting of a persulfate initiator, an azo initiator, hydrogen peroxide, and ascorbic acid may be used. Specific examples of the persulfate initiator may include sodium persulfate (Na₂S₂O₈), potassium persulfate (K₂S₂O₈), ammonium persulfate ((NH₄)₂S₂O₈), etc., and, specific examples of the azo initiator may include 2,2-azobis(2-amidinopropane)dihydrochloride, 2,2-azobis-(N,N-dimethylene)isobutyramidinedihydrochloride, 2-(carbamoylazo)isobutyronitril, 2,2-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride, 4,4-azobis-(4-cyanovalericacid), etc. More various thermal initiators are described in “Principle of Polymerization (Wiley, 1981)”, Odian, page 203, which may be referred to.

Such a polymerization initiator may be added at the concentration of 0.001 to 1 wt %, or 0.005 to 0.1 wt %, based on the monomer composition. If the concentration of the polymerization initiator is too low, polymerization speed may become slow, and remaining monomers may be extracted in a large quantity in the final product. And, if the concentration of the polymerization initiator is too high, polymer chains making up the network of superabsorbent polymer may become short, and thus, extractable contents may increase, and absorbency under pressure of superabsorbent polymer may be lowered, thereby deteriorating the properties of polymer.

Meanwhile, the polymerization of the monomer composition is conducted in the presence of a crosslinking agent (“internal crosslinking agent”) so as to improve the properties of polymer obtained by the polymerization of the acrylic acid-based monomers. The crosslinking agent is for internal crosslinking of hydrogel polymer, and is used separately from “a surface crosslinking agent” as described below.

Such an internal crosslinking agent may be used at the concentration of 0.001 to 1 wt %, or 0.01 to 0.8 wt %, or 0.1 to 0.7 wt %, based on the monomer composition. If the concentration of the internal crosslinking agent is too low, absorption speed of polymer may decrease, and gel strength may be weak. To the contrary, if the concentration of the internal crosslinking agent is too high, absorption force of superabsorbent polymer may decrease, and it may not be preferable as an absorbent.

And, the crosslinking polymerization of the monomer composition may be conducted in the presence of a blowing agent, according to the necessity and degree of improvement in absorption speed. Such a blowing agent may be decomposed during the crosslinking polymerization reaction and generate gas, thus forming pores in the hydrogel polymer. As the result, when such a blowing agent is additionally used, more developed porous structure is formed in super absorbent polymer, and thus, absorption speed of super absorbent polymer may be further improved.

As non-limiting examples, the blowing agent may comprise one or more compounds selected from the group consisting of sodium bicarbonate, sodium carbonate, potassium bicarbonate, potassium carbonate, calcium bicarbonate, calcium carbonate, magnesium bicarbonate, magnesium carbonate, azodicarbonamide (ADCA), dinitroso pentamethylene tetramine (DPT), p,p′-oxybis(benzenesulfonyl hydrazide) (OBSH), p-toluenesulfonyl hydrazide (TSH), sucrose stearate, sucrose palmitate, and sucrose laurate.

The blowing agent may be included in the monomer composition in the content of 1000 to 4000 ppmw, and more specifically, in the content of 1000 ppm or more, or 1100 ppmw or more, or 1200 ppmw or more; and 4000 ppmw or less, or 3500 ppmw or less, or 3000 ppmw or less.

Besides, the monomer composition may further comprise a thickener, a plasticizer, a preservation stabilizer, an antioxidant, and the like, as necessary.

And, the monomer composition may be prepared in the form of a solution in which the above-explained raw materials including acrylic acid-based monomers, polymerization initiator, internal crosslinking agent, blowing agent, and the like are dissolved in a solvent.

Wherein, the solvent that can be used is not limited in terms of its construction as long as it can dissolve the above explained raw materials. For example, as the solvent, water, ethanol, ethyleneglycol, diethyleneglycol, triethyleneglycol, 1,4-butanediol, propyleneglycol, ethyleneglycol monobutyl ether, propyleneglycol monomethyl ether, propyleneglycol monomethyl ether acetate, methylethylketone, acetone, methylamylketone, cyclohexanone, cyclopentanone, diethyleneglycol monomethyl ether, diethyleneglycol ethyl ether, toluene, xylene, butyrolactone, carbitol, methylcellosolve acetate, N,N-dimethylacetamide, or a mixture thereof may be used.

The formation of hydrogel polymer through the polymerization of the monomer composition may be conducted by a common polymerization method, and the process is not specifically limited.

As non-limiting examples, the polymerization method is largely classified into thermal polymerization and photopolymerization according to the kind of energy source, and thermal polymerization may be progressed in a reactor equipped with a stirring axis such as a kneader, and photopolymerization may be progressed in a reactor equipped with a movable conveyer belt.

For example, hydrogel polymer may be obtained by introducing the above-described monomer composition into a reactor such as a kneader equipped with a stirring axis, and supplying hot air or heating the reactor to progress thermal polymerization. Wherein, the hydrogel polymer discharged to the outlet of the reactor may be in the size of a few centimeters to a few millimeters according to the shape of the stirring axis equipped in the reactor. Specifically, the size of obtained hydrogel polymer may vary according to the concentration of the introduced monomer composition and the introduction speed, etc., and commonly, hydrogel polymer with particle diameter of 2 to 50 mm may be obtained.

And, for another example, in case photopolymerization of the monomer composition is progressed in a reactor equipped with a movable conveyer belt as explained above, hydrogel polymer in the form of a sheet may be obtained. Wherein, the thickness of the sheet may vary according to the concentration of the introduced monomer composition and the introduction speed, but commonly, it is preferable that the thickness of the sheet is controlled to 0.5 to 10 cm, so as to enable uniform polymerization of the entire sheet, and simultaneously, secure production speed, and the like.

Hydrogel polymer thus obtained may have a moisture content of 40 to 80 wt %. Wherein, the “moisture content” is the content of moisture occupied based on the total weight of hydrogel polymer, and it means a value obtained by subtracting the weight of polymer of a dry state from the weight of hydrogel polymer. Specifically, it is defined as a value calculated by measuring the weight loss according to moisture evaporation in the polymer while raising the temperature of polymer through infrared heating to dry. Wherein, the temperature is raised from room temperature to about 180° C. and then maintained at 180° C., and the total drying time may be set to 20 minutes including a temperature raising step of 5 minutes.

(Step 2)

The step 2 of the present disclosure is a step of drying, grinding and classifying the hydrogel polymer prepared in step 1, to form base resin powders.

Specifically, in order to increase drying efficiency of hydrogel polymer and affect the morphology of super absorbent polymer, thus affecting various properties of super absorbent polymer including absorption speed, particularly in order to improve absorption speed of super absorbent polymer, in the present disclosure, a step of coarse grinding may be further included before drying the hydrogel polymer. Hereinafter, in order to distinguish it from grinding after drying, the grinding before drying is referred to as ‘coarse grinding’ herein for convenience.

The grinder used for the grinding is not limited in terms of its construction, but specifically, it may include anyone selected from the group consisting of vertical pulverizer, turbo cutter, turbo grinder, rotary cutter mill, cutter mill, disc mill, shred crusher, crusher, chopper and disc cutter, but is not limited thereto.

Wherein, the coarse grinding step may be conducted such that the particle diameter of hydrogel polymer may become about 2 mm to about 10 mm. Grinding to particle diameter less than 2 mm would not be technically easy due to high moisture content of hydrogel polymer, and it may cause aggregation between ground particles. Meanwhile, if grinding to particle diameter greater than 10 mm, the effect for increasing the efficiency of the subsequent drying step may be insignificant.

The drying may be conducted at a temperature of 120 to 250° C., 140 to 200° C., or 150 to 190° C. Wherein, the drying temperature may be defined as the temperature of a heat transfer medium supplied for drying or the temperature inside a drying reactor containing a heat transfer medium and polymer in the drying process. If the drying temperature is too low and drying time is lengthened, process efficiency may be deteriorated, and thus, in order to prevent the same, the drying temperature is preferably 120° C. or more. And, if the drying temperature is higher than needed, the surface of hydrogel polymer may be excessively dried, and thus, generation of fines may increase in the subsequent grinding step, and the properties of the final polymer may be deteriorated, and thus, in order to prevent the same, the drying temperature is preferably 250° C. or less.

Wherein, the drying time in the drying step is not specifically limited, but considering process efficiency and properties of polymer, and the like, it may be controlled to 20 minutes to 90 minutes under the above-described drying temperature.

The drying may be conducted using a common medium, and for example, the drying may be conducted by hot air supply, infrared irradiation, microwave irradiation or UV irradiation to the ground hydrogel polymer, and the like.

And, preferably, drying is conducted such that dried polymer may have a moisture content of 0.1 to 10 wt %. Namely, in case the moisture content of dried polymer is less than 0.1 wt %, due to excessive drying, production cost may increase and crosslinked polymer may be degraded. And, if the moisture content of dried polymer is greater than 10 wt %, defects may be generated in the subsequent process.

Subsequently, the dried hydrogel polymer may be ground. It is a step for optimizing the surface area of base resin powder and super absorbent polymer. The grinding may be conducted such that the particle diameter of ground polymer may become 150 to 850 μm.

Wherein, as a grinder, common grinders such as a pin mill, a hammer mill, a screw mill, a roll mill, a disc mill, a jog mill, and the like may be used.

And, in order to manage the properties of the finally productized super absorbent polymer, a step of selectively classifying particles having particle diameter range of 150 to 850 μm in the polymer particles obtained through the grinding step, is conducted.

Passing through the classification step, base resin powders may be obtained. Such base resin powders may have particle diameter range of 150 to 850 μm, and may comprise fines with particle diameter less than 150 μm in the content of 2 wt % or less, or 1 wt % or less.

And, after base resin powder are obtained by drying and grinding, a step of mixing zirconium phosphate may be further included. Wherein, zirconium phosphate may be previously dry mixed. Namely, zirconium phosphate may be physically dry mixed as solid contents with the base resin before surface crosslinking. Zirconium phosphate is material capable of physically adsorbing malodorous substance. Thus, by further mixing base resin powders with zirconium phosphate, additional deodorization effect may be obtained.

Wherein, the zirconium phosphate may be included in the content of 5.0 parts by weight or less, based on 100 parts by weight of the base resin. The zirconium phosphate is for additional deodorization capacity increase, and may not be included, but in case it is included, it may be specifically included in the content of 0.5 parts by weight or more, 0.8 parts by weight or more, 1.0 parts by weight or more, 1.3 parts by weight or more, 1.5 parts by weight or more, or 1.8 parts by weight or more and 5.0 parts by weight or less, 4.0 parts by weight or less, 3.0 parts by weight or less or 2.0 parts by weight or less. If the content of zirconium phosphate mixed is too small, deodorization effect obtained thereby may be insignificant, and if the content is too large, surface crosslinking may not be sufficiently conducted, and thus, absorption under pressure, and the like may be deteriorated.

(Step 3)

The step 3 of the present disclosure is a step of mixing the base resin powders prepared in the step 2 with a surface crosslinking solution.

The surface crosslinking solution used in step 3 comprises a surface crosslinking agent, and the surface crosslinking agent is not specifically limited as long as it is commonly used for surface crosslinking of super absorbent polymer and is a compound capable of reacting with the functional groups of the polymer.

Preferably, in order to improve the properties of product super absorbent polymer, as the surface crosslinking agent, one or more selected from the group consisting of polyhydric alcohol compounds; epoxy compounds; polyamine compounds; haloepoxy compounds; condensation products of haloepoxy compounds; oxazoline compounds; mono-, di- or polyoxazolidinone compounds; cyclic urea compounds; multivalent metal salts; and alkylene carbonate compounds may be used.

The content of the surface crosslinking agent added may be appropriately selected according to the kind of the surface crosslinking agent added and reaction conditions, but commonly, it may be about 0.001 to about 5 parts by weight, preferably about 0.01 to about 3 parts by weight, more preferably about 0.05 to about 2 parts by weight, based on 100 parts by weight of the polymer.

Meanwhile, the step of forming a surface crosslink layer may be conducted while the surface crosslinking solution further comprises inorganic materials. As such inorganic material, one or more selected from the group consisting of silica, clay, alumina, silica-alumina composite material, titania, zinc oxide and aluminum sulfate may be used. The inorganic material may be used in the form of powder or liquid, and particularly, alumina powder, silica-alumina powder, titania powder, or a nano silica solution. And, the inorganic material may be used in the content of about 0.001 to about 1 part by weight, based on 100 parts by weight of the base resin.

And, the surface crosslinking solution may further comprise a thickener. If the surface of base resin powder is additionally crosslinked in the presence of a thickener, property deterioration may be minimized even after grinding. Specifically, as the thickener, one or more selected from polysaccharide and hydroxy-containing polymer may be used. As the polysaccharide, gum-based thickener and cellulose-based thickener, and the like may be used. As specific examples of the gum-based thickener, xanthan gum, arabic gum, karaya gum, tragacanth gum, ghatti gum, guar gum, locust bean gum and psyllium seed gum, and the like may be mentioned, and as specific examples of the cellulose-based thickener, hyrdoxypropylmethylcellulose, carboxymethylcellulose, methylcellulose, hydroxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, hydroxyethylmethylcellulose, hydroxymethylpropylcellulose, hydroxyethylhydroxypropylcellulose, ethylhydroxyethylcellulose and methylhydroxypropylcellulose, and the like may be mentioned. Meanwhile, as specific examples of the hydroxy-containing polymer, polyethyleneglycol and polyvinylalcohol, and the like may be mentioned.

And, the surface crosslinking solution may further comprise a tannin solution, besides the surface crosslinking agent. Tannin may chemically bond with volatile malodorous substances such as aldehyde-based materials, thus endowing super absorbent polymer with deodorization performance.

The tannin solution may be included in the content of 1.0 part by weight or less, based on 100 parts by weight of the base resin. The tannin is intended to endow super absorbent polymer with additional deodorization property, and may not be included, but in case it is included, it may be specifically included in the content of 0.1 parts by weight or more, 0.3 parts by weight or more, or 0.5 parts by weight or more and 1.0 parts by weight or less, 0.8 parts by weight or less or 0.6 parts by weight or less, based on 100 parts by weight of the base resin. If the content of tannin mixed is too small, deodorization effect obtained thereby may be insignificant, and if it is too large, the properties of super absorbent polymer, such as absorption capacity, absorbency under pressure, and the like may be deteriorated. Wherein, the solids concentration of the tannin solution may be 0.1 wt % or more to 5 wt % or less.

Specifically, the tannin solids content may be 0.005 parts by weight or more, 0.015 parts by weight or more, or 0.025 parts by weight or more and 0.05 parts by weight or less, 0.04 parts by weight or less or 0.03 parts by weight or less, based on 100 parts by weight of the base resin.

Meanwhile, a method for mixing the base resin with the surface crosslinking solution may be appropriately selected without specific limitations, as long as it can uniformly mix them.

For example, a method of putting the surface crosslinking solution and the base resin in a reactor and mixing them, a method of spraying the surface crosslinking solution to the base resin, a method of continuously feeding the base resin and the surface crosslinking solution to a continuously operated mixer and mixed, and the like may be used.

Wherein, the surface crosslinking solution may be a solution, and in case the solid content in the solution is 1 wt % or more, 3 wt % or more, 5 wt % or more, 10 wt % or more, and 50 wt % or less, 30 wt % or less, or 20 wt % or less, it may be appropriately to uniformly disperse in the base resin, and simultaneously agglomeration of the base resin may be prevented.

(Step 4)

The step 4 is a step of reacting the base resin with the surface crosslinking solution to form an interpenetrating polymer network on the surface of the crosslinked polymer included in the base resin, thereby further improving the properties of super absorbent polymer. Through such surface modification, on the surface of the ground base resin particles, a surface crosslink layer is formed.

The formation of the surface crosslink layer may be conducted by a common method of increasing the crosslinking density of polymer particle surface, and for example, it may be conducted by mixing the ground polymer with a surface crosslinking solution comprising a surface crosslinking agent, and heat treating the mixture to conduct a crosslink reaction.

The step 4 may be conducted at a temperature of about 80° C. to about 250° C. More specifically, the surface crosslinking process may be conducted at a temperature of about 100° C. to about 220° C., or about 110° C. to about 200° C., or about 120° C. to about 190° C., for about 10 minutes to about 2 hours, or about 20 minutes to about 60 minutes. If the crosslinking reaction temperature is less than 80° C. or the reaction time is too short, a surface crosslinking reaction may not sufficiently occur, and thus, penetration degree may be lowered, and if the crosslinking reaction temperature is greater than 200° C. or the reaction time is too long, centrifuge retention capacity may be lowered.

A temperature rise means for the surface crosslinking reaction is not specifically limited. A heat transfer medium may be supplied, or a heat source may be directly supplied for heating. Wherein, as the kind of heat transfer media that can be used, temperature-increased fluids such as steam, hot air, hot oil, and the like may be used, but the invention is not limited thereto, and the temperature of heat transfer medium supplied may be appropriately selected considering the means of heat transfer medium, temperature rise means, and target temperature. Meanwhile, as the heat source directly supplied, electric heating, and gas heating may be mentioned, but the invention is not limited thereto.

(Step 5)

The step 5 is a step of mixing the super absorbent polymer in which a surface crosslink layer is formed on the base resin, with a solution comprising sulfur-containing amino acid and metal iodide salt. Namely, the step 5 is a step of mixing super absorbent polymer with a solution comprising sulfur-containing amino acid and metal iodide salt, to obtain a composition of super absorbent polymer.

The sulfur-containing amino acid may be added to super absorbent polymer to endow deodorization property. Specifically, the sulfur-containing amino acid may comprise one or more selected from the group consisting of cysteine, cystine, and methionine. More specifically, the sulfur-containing amino acid may comprise cysteine or methionine.

The metal iodide salt acts on most malodorous substances and works in general, by oxidizing malodorous substance to remove it.

The metal iodide salt solution may be included in the content of 0.1 to 5.0 parts by weight, based on 100 parts by weight of the base resin. Specifically, the metal iodide salt solution may be included in the content of 0.1 parts by weight or more, 0.5 parts by weight or more, 1.0 part by weight or more, 1.5 parts by weight or more or 2.0 parts by weight or more and 5.0 parts by weight or less, 4.0 parts by weight or less, 3.0 parts by weight or less, or 2.5 parts by weight or less. And, the metal iodide salt solution may be a solution with solids concentration of 1% or less.

Specifically, the metal iodide salt may be included in the content of 0.001 parts by weight or more, 0.005 parts by weight or more, 0.01 parts by weight or more, 0.015 parts by weight or more or 0.02 parts by weight or more and 0.05 parts by weight or less, 0.04 parts by weight or less, 0.03 parts by weight or less, or 0.025 parts by weight or less.

And, if the content of the metal iodide salt is too small, deodorization property may not be sufficiently realized, and if it is too large, unique properties of super absorbent polymer may be deteriorated, and it may be supplied as a solution in the process to increase tailings, and deodorization capacity may decrease to the contrary.

The sulfur-containing amino acid and metal iodide salt are mixed with super absorbent polymer as an aqueous solution in water solvent, and they exist in super absorbent polymer while being mixed and physically contained in super absorbent polymer.

After the step of mixing super absorbent polymer including a surface crosslink layer with an aqueous solution comprising sulfur-containing amino acid and metal iodide salt (hydration and post-addition step), a drying step may be further conducted.

Hereinafter, preferable examples are presented for better understanding of the invention. However, the following examples are presented only as the illustrations of the invention, and are not intended to limit the invention.

Comparative Example 1

100 g of acrylic acid, 0.37 g of N,N′-methylenebisacrylamide as a crosslinking agent, 0.15 g of sodium persulfate(SPS) as a thermal initiator, 0.008 g of benzoin ether as UV initiator, 40 g of caustic soda(NaOH), and 127 g of water were mixed, to prepare an aqueous monomer composition with a monomer concentration of 45.8 wt %. The aqueous monomer composition was introduced into a feed section of a polymerization reactor equipped with a continuously moving conveyor belt, and then, while maintaining a polymerization atmosphere temperature of 80° C., UV was irradiated with a UV irradiation device (dose: 10 mW/cm²), and UV polymerization was progressed for 2 minutes, thus preparing hydrogel polymer.

The hydrogel polymer was transferred to a meat chopper and cut to 2 mm to 10 mm. Wherein, the moisture content of cut hydrogel polymer was 47 wt %. Subsequently, the hydrogel polymer was dried in a hot air dryer of 170° C. for 30 minutes, and the dried hydrogel polymer was ground with a pin mill. Subsequently, polymers having a particle size range of 150 μm to 850 μm were classified with a sieve to prepare a base resin.

Comparative Example 2

The obtained super absorbent polymer was mixed an aqueous cysteine solution (cysteine concentration 13 wt %). Wherein, they were mixed such that the content of cysteine became 0.1 parts by weight, based on 100 parts by weight of base resin. And then, a drying step was conducted at 80° C. for 25 minutes.

Comparative Example 3

100 g of acrylic acid, 0.37 g of N,N′-methylenebisacrylamide as a crosslinking agent, 0.15 g of sodium persulfate(SPS) as a thermal initiator, 0.008 g of benzoin ether as UV initiator, 40 g of caustic soda(NaOH), and 127 g of water were mixed, to prepare an aqueous monomer composition with a monomer concentration of 45.8 wt %. The aqueous monomer composition was introduced into a feed section of a polymerization reactor equipped with a continuously moving conveyor belt, and then, while maintaining a polymerization atmosphere temperature of 80° C., UV was irradiated with a UV irradiation device(dose: 10 mW/cm²), and UV polymerization was progressed for 2 minutes, thus preparing hydrogel polymer.

The obtained super absorbent polymer was mixed with an aqueous CuI solution (CuI concentration 1 wt %). Wherein, they were mixed such that the content of CuI became 0.02 parts by weight, based on 100 parts by weight of base resin. And then, a drying step was conducted at 80° C. for 25 minutes.

Comparative Example 4

The obtained super absorbent polymer was dry mixed with Beta-cyclodextrin in the content of 1.0 part by weight, based on 100 parts by weight of super absorbent polymer.

Comparative Example 5

100 g of acrylic acid, 0.37 g of N,N′-methylenebisacrylamide as a crosslinking agent, 0.15 g of sodium persulfate(SPS) as a thermal initiator, 0.008 g of benzoin ether as UV initiator, 40 g of caustic soda(NaOH), and 127 g of water were mixed, to prepare an aqueous monomer composition with a monomer concentration of 45.8 wt %. The aqueous monomer composition was introduced into a feed section of a polymerization reactor equipped with a continuously moving conveyor belt, and then, while maintaining a polymerization atmosphere temperature of 80° C., UV was irradiated with a UV irradiation device(dose: 10 mW/cm²), and UV polymerization was progressed for 2 minutes, thus preparing hydrogel polymer.

And then, before surface crosslinking, the base resin powders were dry mixed with zirconium phosphate. The zirconium phosphate was mixed in the content of 2.0 parts by weight, based on 100 parts by weight of base resin.

And then, to 100 parts by weight of the base resin mixed with zirconium phosphate, a surface crosslinking solution (2.5 parts by weight of water, 0.1 parts by weight of ethyleneglycol diglycidyl ether(EX-810), 0.1 parts by weight of aluminum sulfate 18 hydrate(Al—S), and 0.1 parts by weight of silica(Aerosil A200)) was uniformly mixed, and then, a surface crosslinking reaction was progressed at 140° C. for 30 minutes. After completing the surface treatment, by classification with a sieve, super absorbent polymer with a particle diameter range of 150 to 850 μm was obtained.

Comparative Example 6

100 g of acrylic acid, 0.37 g of N,N′-methylenebisacrylamide as a crosslinking agent, 0.15 g of sodium persulfate(SPS) as a thermal initiator, 0.008 g of benzoin ether as UV initiator, 40 g of caustic soda(NaOH), and 127 g of water were mixed, to prepare an aqueous monomer composition with a monomer concentration of 45.8 wt %. The aqueous monomer composition was introduced into a feed section of a polymerization reactor equipped with a continuously moving conveyor belt, and then, while maintaining a polymerization atmosphere temperature of 80° C., UV was irradiated with a UV irradiation device(dose: 10 mW/cm²), and UV polymerization was progressed for 2 minutes, thus preparing hydrogel polymer.

And then, to 100 parts by weight of the above-prepared base resin, a surface crosslinking solution (2.5 parts by weight of water, 0.1 parts by weight of ethyleneglycol diglycidyl ether(EX-810), 0.1 parts by weight of aluminum sulfate 18 hydrate(Al—S), and 0.1 parts by weight of silica(Aerosil A200)) and a tannin solution were uniformly mixed, and then, a surface crosslinking reaction was progressed at 140° C. for 30 minutes. As the tannin solution, an aqueous solution with a solid content of 5 parts by weight, based on 100 parts by weight of the solution, was used. The tannin solution was mixed in the content of 0.05 parts by weight, based on 100 parts by weight of base resin. After completing the surface treatment, by classification with a sieve, super absorbent polymer with a particle diameter range of 150 to 850 μm was obtained.

Example 1

100 g of acrylic acid, 0.37 g of N,N′-methylenebisacrylamide as a crosslinking agent, 0.15 g of sodium persulfate(SPS) as a thermal initiator, 0.008 g of benzoin ether as UV initiator, 40 g of caustic soda(NaOH), and 127 g of water were mixed, to prepare an aqueous monomer composition with a monomer concentration of 45.8 wt %. The aqueous monomer composition was introduced into a feed section of a polymerization reactor equipped with a continuously moving conveyor belt, and then, while maintaining a polymerization atmosphere temperature of 80° C., UV was irradiated with a UV irradiation device(dose: 10 mW/cm²), and UV polymerization was progressed for 2 minutes, thus preparing hydrogel polymer.

The obtained super absorbent polymer was mixed with an aqueous cysteine solution (cysteine concentration 13 wt %) and an aqueous CuI solution (CuI concentration 1 wt %). Wherein, they were mixed such that the content of cysteine became 0.1 parts by weight, based on 100 parts by weight of base resin, and the content of CuI became 0.02 parts by weight, based on 100 parts by weight of base resin. And then, a drying step was conducted at 80° C. for 25 minutes.

Example 2

The obtained super absorbent polymer was mixed with an aqueous cysteine solution (cysteine concentration 13 wt %) and an aqueous CuI solution (CuI concentration 1 wt %) were mixed. Wherein, they were mixed such that the content of cysteine became 0.15 parts by weight, based on 100 parts by weight of base resin, and the content of CuI became 0.01 parts by weight, based on 100 parts by weight of base resin. And then, a drying step was conducted at 80° C. for 25 minutes.

Example 3

The obtained super absorbent polymer was mixed with an aqueous cysteine solution (cysteine concentration 13 wt %) and an aqueous CuI solution (CuI concentration 1 wt %). Wherein, they were mixed such that the content of cysteine became 0.3 parts by weight, based on 100 parts by weight of base resin, and the content of CuI became 0.001 parts by weight, based on 100 parts by weight of base resin. And then, a drying step was conducted at 80° C. for 25 minutes.

Example 4

100 g of acrylic acid, 1.0 g of cetethyldimonium bromide as polymerizable antibacterial monomers, 0.37 g of N,N′-methylenebisacrylamide as a crosslinking agent, 0.15 g of sodium persulfate(SPS) as a thermal initiator, 0.008 g of benzoin ether as UV initiator, 40 g of caustic soda(NaOH), and 127 g of water were mixed, to prepare an aqueous monomer composition with a monomer concentration of 45.8 wt %. The aqueous monomer composition was introduced into a feed section of a polymerization reactor equipped with a continuously moving conveyor belt, and then, while maintaining a polymerization atmosphere temperature of 80° C., UV was irradiated with a UV irradiation device (dose: 10 mW/cm²), and UV polymerization was progressed for 2 minutes, thus preparing hydrogel polymer.

And then, before surface crosslinking, the base resin powders were mixed with zirconium phosphate. The zirconium phosphate was mixed such that the content became 2.0 parts by weight, based on 100 parts by weight of the base resin.

And then, to 100 parts by weight of the above-prepared base resin, a surface crosslinking solution (2.5 parts by weight of water, 0.1 parts by weight of ethyleneglycol diglycidyl ether(EX-810), 0.1 parts by weight of aluminum sulfate 18 hydrate(Al—S), and 0.1 parts by weight of silica(Aerosil A200)) and a tannin solution were uniformly mixed, and then, a surface crosslinking reaction was progressed at 140° C. for 30 minutes. As the tannin solution, an aqueous solution with a tannin solid content of 5 parts by weight, based on 100 parts by weight of the solution, was used. The tannin solution was mixed in the solid content of 0.05 parts by weight, based on 100 parts by weight of base resin. After completing the surface treatment, by classification with a sieve, super absorbent polymer with a particle diameter range of 150 to 850 μm was obtained.

The obtained super absorbent polymer was mixed with an aqueous cysteine solution (cysteine concentration 13 wt %) and an aqueous CuI solution (CuI concentration 1 wt %). Wherein, they were mixed such that the content of cysteine became 0.15 parts by weight, based on 100 parts by weight of base resin, and the content of CuI became 0.01 parts by weight, based on 100 parts by weight of base resin. And then, a drying step was conducted at 80° C. for 25 minutes.

Example 5

100 g of acrylic acid, 0.5 g of cetethyldimonium bromide as polymerizable antibacterial monomers, 0.37 g of N,N′-methylenebisacrylamide as a crosslinking agent, 0.15 g of sodium persulfate(SPS) as a thermal initiator, 0.008 g of benzoin ether as UV initiator, 40 g of caustic soda(NaOH), and 127 g of water were mixed, to prepare an aqueous monomer composition with a monomer concentration of 45.8 wt %. The aqueous monomer composition was introduced into a feed section of a polymerization reactor equipped with a continuously moving conveyor belt, and then, while maintaining a polymerization atmosphere temperature of 80° C., UV was irradiated with a UV irradiation device (dose: 10 mW/cm²), and UV polymerization was progressed for 2 minutes, thus preparing hydrogel polymer.

The hydrogel polymer was transferred to a meat chopper and cut to 2 mm to 10 mm. Wherein, the moisture content of cut hydrogel polymer was 47 wt %. Subsequently, the hydrogel polymer was dried in a hot air dryer of 170° C. for 30 minutes, and the dried hydrogel polymer was ground with a pin mill. Subsequently, polymers having a particle size range of 150 μm to 850 μm was classified with a sieve to prepare a base resin.

And then, to 100 parts by weight of the above-prepared base resin, a surface crosslinking solution (2.5 parts by weight of water, 0.1 parts by weight of ethyleneglycol diglycidyl ether(EX-810), 0.1 parts by weight of aluminum sulfate 18 hydrate(Al—S), and 0.1 parts by weight of silica(Aerosil A200)) and a tannin solution were uniformly mixed, and then, a surface crosslinking reaction was progressed at 140° C. for 30 minutes. As the tannin solution, an aqueous solution with a tannin solid content of 5 parts by weight, based on 100 parts by weight of the solution, was used. The tannin solution was mixed in the solid content of 0.05 parts by weight, based on 100 parts by weight of base resin. After completing the surface treatment, by classification with a sieve, super absorbent polymer with a particle diameter range of 150 to 850 μm was obtained.

The obtained super absorbent polymer was mixed with an aqueous cysteine solution (cysteine concentration 13 wt %) and an aqueous CuI solution (CuI concentration 1 wt %) were mixed. Wherein, they were mixed such that the content of cysteine became 0.3 parts by weight, based on 100 parts by weight of base resin, and the content of CuI became 0.001 parts by weight, based on 100 parts by weight of base resin. And then, a drying step was conducted at 80° C. for 25 minutes.

Example 6

The hydrogel polymer was transferred to a meat chopper and cut to 2 mm to 10 mm. Wherein, the moisture content of cut hydrogel polymer was 47 wt %. Subsequently, the hydrogel polymer was dried in a hot air dryer of 170° C. for 30 minutes, and the dried hydrogel polymer was ground with a pin mill. Subsequently, polymers having a particle size range of 150 μm to 850 μm was classified with a sieve to prepare a base resin.

The obtained super absorbent polymer was mixed with an aqueous methionine solution (methionine concentration 13 wt %) and an aqueous CuI solution (CuI concentration 1 wt %) were mixed. Wherein, they were mixed such that the content of methionine became 0.15 parts by weight, based on 100 parts by weight of base resin, and the content of CuI became 0.01 parts by weight, based on 100 parts by weight of base resin. And then, a drying step was conducted at 80° C. for 25 minutes.

Example 7

The hydrogel polymer was transferred to a meat chopper and cut to 2 mm to 10 mm. Wherein, the moisture content of cut hydrogel polymer was 47 wt %. Subsequently, the hydrogel polymer was dried in a hot air dryer of 170° C. for 30 minutes, and the dried hydrogel polymer was ground with a pin mill. Subsequently, polymers having a particle size range of 150 μm to 850 μm was classified with a sieve to prepare a base resin.

And then, to 100 parts by weight of the above-prepared base resin, a surface crosslinking solution (2.5 parts by weight of water, 0.1 parts by weight of ethyleneglycol diglycidyl ether(EX-810), 0.1 parts by weight of aluminum sulfate 18 hydrate(Al—S), and 0.1 parts by weight of silica(Aerosil A200)) and a tannin solution were uniformly mixed, and then, a surface crosslinking reaction was progressed at 140° C. for 30 minutes. As the tannin solution, an aqueous solution with a tannin solid content of 5 parts by weight, based on 100 parts by weight of the solution, was used. The tannin solution was mixed in the solid content of 0.05 parts by weight, based on 100 parts by weight of base resin. After completing the surface treatment, by classification with a sieve, super absorbent polymer with a particle diameter range of 150 to 850 μm was obtained.

The obtained super absorbent polymer was mixed with an aqueous cysteine solution (cysteine concentration 13 wt %) and an aqueous CuI solution (CuI concentration 1 wt %) were mixed. Wherein, they were mixed such that the content of cysteine became 0.6 parts by weight, based on 100 parts by weight of base resin, and the content of CuI became 0.01 parts by weight, based on 100 parts by weight of base resin. And then, a drying step was conducted at 80° C. for 25 minutes.

TABLE 1

Polymerizable
Tannin solid

Sulfur-

antibacterial
in Tannin

containing

monomers
solution
Zirconium

amino acid
Metal iodide
(based on
(concentration
phosphate

(based on
salt (based on
100 parts by
5%) (based on
(based on

100 parts by
100 parts by
weight of
100 parts by
100 parts by

weight of
weight of
acrylic acid-
weight of
weight of

base resin)
base resin)
based monomers)
base resin)
base resin)
Others

Example 1
0.1
0.02
—
—
—
cysteine

Example 2
0.15
0.01
—
—
—
cysteine

Example 3
0.3
0.001
—
—
—
cysteine

Example 4
0.15
0.01
1.0
0.05
2.0
cysteine

Example 5
0.3
0.001
0.5
0.05
2.0
cysteine

Example 6
0.15
0.01
—
—
—
methionine

Example 7
0.6
0.01
0.5
0.05
2.0
cysteine

Comparative
—
—
—
—
—

Example 1

Comparative
0.1
—
—
—
—
cysteine

Example 2

Comparative
—
0.02
—
—
—

Example 3

Comparative
—
—
—
—
—
Beta-

Example 4

cyclodextrin

Comparative
—
—
—
—
2.0

Example 5

Comparative
—
—
—
0.05
—

Example 6

Experimental Example

For the compositions of super absorbent polymer prepared in Examples and Comparative Examples, the properties were measured as follows.

1) Deodorization Capacity

Deodorization capacity was measured by an adsorption tube measurement method. As malodorous substances, diacetyl, 3-methylbutananl, and dimethyltrisulfide(DMTS) were selected and deodorization capacity was tested.

- Adsorption tube measurement method: Into a 500 mL glass bottle, 1 g of super absorbent polymer was put, and then, 25 mL of malodorous substance was introduced. And then, aging was progressed in a constant temperature chamber for 3 hours, followed by capturing for 20 minutes. Wherein, the temperature of the constant temperature chamber was 35° C., and N2 flow rate was 230 mL/min. The odor pushed out was then adsorbed to the connected adsorption tube, which was repeated twice per the same sample to capture. The result of capture was analyzed by GC and confirmed.
- Deodorization rate (%)=[the amount of odor of Reference sample (super absorbent polymer of Comparative Example 1) measured by GC—the amount of odor of sample measured by GC]/the amount of odor of Reference sample (super absorbent polymer of Comparative Example 1) measured by GC X 100(%)

2) Centrifuge Retention Capacity (CRC)

Centrifuge retention capacity of each polymer by absorption rate under no load was measured according to European Disposables and Nonwovens Association, (EDANA) standard EDANA WSP 241.3.

Specifically, from each polymer obtained through Examples and Comparative Examples, polymer classified to the particle diameter range of 300 μm˜500 μm was obtained. W₀(g, about 0.2 g) of such polymer was uniformly put in an envelope made of non-woven fabric, and the envelope was sealed, and then, dipped in a 0.9 wt % saline solution. After 30 minutes, the envelope was drained at 250 G for 3 minutes using a centrifuge, and the weight W₂(g) of the envelope was measured. And, the same operation was conducted using an empty envelope without polymer, and then, the weight W₁(g) at that time was measured.

Using the weights thus obtained, CRC (g/g) was confirmed by the following Mathematical Formula 1.

$\begin{matrix} CRC (g / g) = {[W_{2} (g) - W_{1} (g)] / W_{0} (g)} - 1 & [Mathematical Formula 1] \end{matrix}$

3) AUP: Absorbency Under Pressure (AUP)

For each super absorbent polymer of Examples and Comparative Examples, absorbency under pressure of 0.7 psi was measured according to EDANA method WSP 242.3.

First, when measuring absorbency under pressure, the classified polymer used to measure CRC was used.

Specifically, on the bottom of a plastic cylinder having an inner diameter of 25 mm, a 400 mesh wire netting made of stainless steel was installed. And, W₀(g) of the super absorbent polymer was uniformly scattered on the screen under conditions of room temperature and 50% humidity, and a piston capable of uniformly applying a load of 0.7 psi was put thereon, wherein a piston having an outer diameter slightly smaller than 25 mm was used such that there was no gap with the inner wall of the cylinder and the up and down movement was not hindered. At this time, the weight W₃(g) of the apparatus was measured.

Inside a petri dish having a diameter of 150 mm, a glass filter having a diameter of 90 mm and a thickness of 5 mm was laid, and a 0.9 wt % saline solution was poured to the same level as the upper side of the glass filter. And, one piece of a filter paper having a diameter of 90 mm was laid thereon. And then, the above measurement apparatus was put on the filter paper, and the solution was absorbed under pressure for 1 hour. After 1 hour, the measurement apparatus was lifted, and the weight W₄(g) was measured. Using the obtained weights, absorbency under pressure (g/g) was calculated according to the following Mathematical Formula 2.

$\begin{matrix} AUP = [W_{4} (g) - W_{3} (g)] / W_{0} (g) & [Mathematical Formula 2] \end{matrix}$

The results of deodorization capacity were shown in Table 2, and the results of centrifuge retention capacity and absorbency under pressure were shown in Table 3.

The numerical values in Table 2 indicate deodorization efficiencies in comparison with Comparative Example 1, and the higher the deodorization efficiency is, the higher the numerical value is.

TABLE 2

Deodorization

3-

efficiency (%)
Diacetyl
methylbutanal
Dimethyltrisulfide

Example 1
13
27
35

Example 2
58
58
82

Example 3
77
77
99

Example 4
66
60
82

Example 5
80
78
97

Example 6
60
53
85

Example 7
85
82
98

Comparative
0
0
0

Example 1

Comparative
13
27
28

Example 2

Comparative
0
3
40

Example 3

Comparative
0
0
30

Example 4

Comparative
20
0
22

Example 5

Comparative
11
49
51

Example 6

TABLE 3

CRC
AUP

(g/g)
(g/g)

Example 1
29.5
21.5

Example 2
30.1
21.3

Example 3
30.2
21.0

Example 4
29.4
20.9

Example 5
30.0
21.1

Example 6
29.5
20.7

Example 7
29.9
21.0

Number	Date	Country	Kind
10-2021-0182480	Dec 2021	KR	national
10-2022-0171681	Dec 2022	KR	national

A Composition of Super Absorbent Polymer and a Preparation Method Thereof

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