[One]Cross-Citation with Related Application(s)
[2]This application claims the benefit of priority based on Korean Patent Application No. 10-2019-0121171 dated September 30, 2019, and all contents disclosed in the literature of the Korean patent application are incorporated as a part of this specification.
[3]
The present invention relates to a superabsorbent polymer composition exhibiting excellent water absorption performance and a method for preparing the same.
[4]
background
[5]
Super Absorbent Polymer (SAP) is a synthetic polymer material that can absorb water 500 to 1,000 times its own weight. Material), etc., are named differently. The superabsorbent polymer as described above started to be put to practical use as a sanitary tool, and is now widely used as a soil repair agent for horticulture, water-retaining material for civil engineering and construction, sheets for seedlings, freshness maintenance agent in the food distribution field, and materials for poultice. .
[6]
[7]
In most cases, these superabsorbent polymers are widely used in sanitary materials such as diapers and sanitary napkins. In addition, it is necessary to exhibit excellent permeability by absorbing water and maintaining its shape well even in a state of volume expansion (swelling).
[8]
[9]
However, it is known that it is difficult to improve both the water holding capacity (CRC), which is a physical property representing the basic water absorption and water holding power of the superabsorbent polymer, and the water absorption capacity under pressure (AUL), which shows the property of well retaining water absorbed even under external pressure. . This is because, when the overall crosslinking density of the superabsorbent polymer is controlled to be low, the water holding capacity can be relatively high, but the crosslinked structure is sparse and the gel strength is lowered, so that the absorbency under pressure can be reduced. Conversely, when the absorbency under pressure is improved by controlling the crosslinking density to be high, moisture may be difficult to be absorbed between the dense crosslinked structures, and the basic water holding capacity may be lowered. For the above reasons, there is a limitation in providing a super absorbent polymer having improved water holding capacity and absorbency under pressure.
[10]
[11]
However, as sanitary materials such as diapers and sanitary napkins are thinned in recent years, higher absorption performance is required for superabsorbent polymers. Among these, the simultaneous improvement of water holding capacity and absorbency under pressure, which are opposite physical properties, and improvement of liquid permeability, etc. are emerging as important issues.
[12]
[13]
In addition, the surface of the superabsorbent polymer applied to sanitary materials such as diapers or sanitary napkins may become moist after absorbing the liquid and may give an unpleasant feeling of use. The faster the initial absorption rate, the more comfortable the use state can be maintained because the surface remains dry even after swelling by the liquid.
[14]
[15]
In general, the absorption rate can be improved by increasing the surface area of ​​the superabsorbent polymer. For example, a method of using a foaming agent to form a porous structure on the particle surface of the superabsorbent polymer or to reduce the chopper hole size has been applied. However, in this case, a problem occurs in that the amount of fine powder in the product increases, and the strength of the superabsorbent polymer is lowered, which causes deterioration of physical properties.
[16]
[17]
Accordingly, there is a continuous need for research on a method for improving the initial absorption rate while minimizing deterioration in physical properties due to an increase in the fine powder content.
[18]
DETAILED DESCRIPTION OF THE INVENTION
technical challenge
[19]
Accordingly, an object of the present invention is to provide a superabsorbent polymer composition exhibiting excellent water absorption performance by using a specific compound in combination in the surface crosslinking step, and a method for preparing the same.
[20]
means of solving the problem
[21]
The present invention in order to solve the above problems,
[22]
forming a hydrogel polymer by crosslinking and polymerizing a water-soluble ethylenically unsaturated monomer having an acidic group at least partially neutralized in the presence of an internal crosslinking agent;
[23]
drying, pulverizing, and classifying the hydrogel polymer to obtain a base resin powder; and
[24]
Forming superabsorbent polymer particles by surface-crosslinking the base resin powder in the presence of a surface crosslinking solution containing a cyclic carbonate-based surface crosslinking agent and sodium dodecyl sulfate;
[25]
A method for preparing a super absorbent polymer composition is provided.
[26]
[27]
In addition, the present invention provides a superabsorbent polymer composition prepared by the above-described method.
[28]
Specifically, the superabsorbent polymer composition includes: superabsorbent polymer particles comprising a cross-linked polymer of a water-soluble ethylenically unsaturated monomer having at least a partially neutralized acidic group;
[29]
A surface crosslinking layer formed by additional crosslinking of the crosslinked polymer via a cyclic carbonate-based surface crosslinking agent and sodium dodecyl sulfate is further included on a part of the surface of the superabsorbent polymer particles.
[30]
Effects of the Invention
[31]
According to the present invention, a superabsorbent polymer composition exhibiting excellent water absorption performance can be prepared.
[32]
Modes for carrying out the invention
[33]
The terminology used herein is used to describe exemplary embodiments only, and is not intended to limit the present invention.
[34]
The singular expression includes the plural expression unless the context clearly dictates otherwise. In the present specification, terms such as "comprise", "comprising" or "having" are intended to designate that an embodied feature, step, element, or a combination thereof is present, and includes one or more other features or steps; It should be understood that the possibility of the presence or addition of components, or combinations thereof, is not precluded in advance.
[35]
Terms such as first, second, third, etc. are used to describe various elements, and the terms are used only for the purpose of distinguishing one element from other elements.
[36]
Since the present invention may have various changes and may have various forms, specific embodiments will be illustrated and described in detail below. However, this is not intended to limit the present invention to the specific disclosed form, it should be understood to include all modifications, equivalents and substitutes included in the spirit and scope of the present invention.
[37]
As used herein, the term "polymer" or "polymer" refers to a polymerized state of a water-soluble ethylenically unsaturated monomer, and may cover all water content ranges or particle size ranges. Among the above polymers, a polymer having a water content (moisture content) of about 40% by weight or more in a state before drying after polymerization may be referred to as a hydrogel polymer, and particles obtained by pulverizing and drying the hydrogel polymer may be referred to as a crosslinked polymer. have.
[38]
In addition, the term "superabsorbent polymer particles" refers to a particulate material comprising an acidic group and a crosslinked polymer in which a water-soluble ethylenically unsaturated monomer in which at least a portion of the acidic group is neutralized is polymerized and crosslinked by an internal crosslinking agent.
[39]
In addition, the term "super absorbent polymer" refers to a crosslinked polymer obtained by polymerizing a water-soluble ethylenically unsaturated monomer containing an acidic group and neutralizing at least a portion of the acidic group, or powder consisting of particles of a superabsorbent polymer obtained by pulverizing the crosslinked polymer, depending on the context. It means a base resin in the form of (powder), or the crosslinked polymer or the base resin is subjected to additional processes, such as surface crosslinking, fine powder reassembly, drying, pulverization, classification, etc., to a state suitable for commercialization. used to be all-inclusive. Accordingly, the term “super absorbent polymer composition” may be interpreted as including a composition including a super absorbent polymer, that is, a plurality of super absorbent polymer particles.
[40]
[41]
Hereinafter, a method for manufacturing a super absorbent polymer and a super absorbent polymer according to specific embodiments of the present invention will be described in more detail.
[42]
[43]
Method for preparing super absorbent polymer composition
[44]
According to one embodiment of the invention, in the presence of an internal cross-linking agent, cross-linking polymerization of a water-soluble ethylenically unsaturated monomer having an acidic group at least partially neutralized to form a hydrogel polymer; drying, pulverizing, and classifying the hydrogel polymer to obtain a base resin powder; and forming superabsorbent polymer particles by surface crosslinking the base resin powder in the presence of a surface crosslinking solution containing a cyclic carbonate-based surface crosslinking agent and sodium dodecyl sulfate; provided
[45]
[46]
In conventional products to which the superabsorbent polymer is applied, a method of increasing the surface area of ​​the superabsorbent polymer is used to improve the absorption rate. A method of reducing the size is being applied. However, in this case, there is a problem in that the amount of fine powder generated in the product increases, and there is a problem in that the strength of the superabsorbent polymer is lowered, thereby reducing the physical properties.
[47]
Accordingly, the present inventors do not use a foaming agent during the polymerization process, and by using a combination of a specific compound in the surface crosslinking step, the fine powder (particles having an average particle diameter of less than about 150 μm) generated by the foaming agent during the polymerization process increases without increasing. It was confirmed that excellent absorption performance can be implemented, and the present invention was completed.
[48]
Specifically, by using a cyclic carbonate-based compound as a surface crosslinking agent and sodium dodecyl sulfate, the basic physical properties of the superabsorbent polymer, water holding capacity and pressure, through the crosslinking mechanism between the cyclic carbonate and the carboxyl group of the superabsorbent polymer It improves the absorption capacity and exhibits excellent liquid permeability with a fast initial absorption rate through the action of hydrophilic groups of cyclic carbonate and sodium dodecyl sulfate. At the same time, it was confirmed that excellent absorption performance can be realized. In particular, the sodium dodecyl sulfate was used as a blowing agent in the conventional polymerization step, but when it is used in the surface crosslinking step instead of the polymerization step, the degree of fine powder generation is not increased. It was confirmed that the objective effect of
[49]
[50]
surface crosslinking agent
[51]
The surface cross-linking agent is a cyclic carbonate-based compound, which allows water to be rapidly absorbed through a hydrophilic mechanism of action in the surface cross-linking step, and when used in combination with sodium dodecyl sulfate to be described later, it is possible to further improve the absorption rate.
[52]
Specific examples of the surface crosslinking agent include ethylene carbonate, propylene carbonate, and glycerol carbonate, and these may be used alone or in combination of two or more. Preferably, it is preferable to use all of ethylene carbonate, propylene carbonate, and glycerol carbonate in combination to improve absorption performance, and in particular, it is preferable because it can maximize the synergistic effect with sodium dodecyl sulfate, which will be described later.
[53]
The surface crosslinking agent may be included in an amount of 0.5 to 5.0 parts by weight, preferably 1.0 to 3.0 parts by weight, based on 100 parts by weight of the base resin. When included in the above content range, excellent absorption performance can be realized, and excellent synergistic effect with sodium dodecyl sulfate component, which will be described later, can be realized.
[54]
Here, the content of the surface crosslinking agent means a mixed content of two or more of the corresponding compounds.
[55]
On the other hand, when the surface crosslinking agent is included in a small amount outside the above content, the surface crosslinking reaction is not sufficiently performed, so it is difficult to realize the water holding capacity and absorbency under pressure properties to the desired degree in the product. If it is included, there may be a problem that the water holding capacity and the absorbency under pressure decrease rapidly.
[56]
When all of ethylene carbonate, propylene carbonate, and glycerol carbonate are used in combination as the surface crosslinking agent, they are based on 100 parts by weight of the total surface crosslinking agent, 10 to 50 parts by weight of ethylene carbonate, 10 to 50 parts by weight of propylene carbonate, and glycerol 10 to 50 parts by weight of carbonate. Preferably, 10 to 20 parts by weight of ethylene carbonate, 10 to 20 parts by weight of propylene carbonate, and 10 to 20 parts by weight of glycerol carbonate are included.
[57]
By being used in combination within the above content range, if excellent absorption performance can be realized, excellent synergistic effect with sodium dodecyl sulfate component, which will be described later, can be realized.
[58]
On the other hand, when ethylene carbonate is included in excess beyond the above content range, there may be a problem that the water holding capacity and the water holding capacity under pressure decrease rapidly, and the pressurized water holding capacity that is contained in excess beyond the content range of propylene carbonate is lowered Problems can arise. In addition, when glycerol carbonate is included in excess beyond the above content range, there may be a problem in that the water holding capacity under pressure decreases.
[59]
[60]
The sodium dodecyl sulfate (SDS), which was used as a foaming agent in the polymerization step of the base resin in the prior art, is used in the surface crosslinking step to improve the effect of improving the absorption rate through a hydrophilic group action mechanism. When sodium sulfate is used in the polymerization step, the generation of fine powder in the base resin powder increases and there is a problem of lowering the absorption rate. It is economical because the absorption rate can be improved through the mechanism of action of the hydrophilic group, and the yield of the final product can be increased because the generation of fine powder is not increased. In particular, when used in combination with the cyclic carbonate compound, which is the above-mentioned surface crosslinking agent, the effect of improving the absorption rate can be maximized.
[61]
The sodium dodecyl sulfate may be included in an amount of 0.001 to 1.0 parts by weight, preferably 0.05 to 0.5 parts by weight or 0.01 to 0.3 parts by weight, based on 100 parts by weight of the total base resin. When included in the above content range, excellent absorption performance can be realized, and excellent synergistic effect with the surface crosslinking agent component to be described later can be realized. In particular, it is preferable to implement a mechanism of action of a hydrophilic group.
[62]
On the other hand, when the sodium dodecyl sulfate is contained in a small amount outside the above content, it is difficult to achieve the desired effect in a very small amount, the absorption rate is not improved, and also, when it is contained in excess outside the content range, the surface tension If this falls, the absorption rate may be slowed down.
[63]
[64]
Hereinafter, each step of the method for preparing the superabsorbent polymer composition of one embodiment will be described in more detail.
[65]
[66]
Hydrogel polymer formation step (polymerization step)
[67]
In the method for producing a superabsorbent polymer according to one embodiment, first, in the presence of an internal crosslinking agent and a polymerization initiator, a step of crosslinking and polymerizing a water-soluble ethylenically unsaturated monomer having an acidic group at least partially neutralized to form a hydrogel polymer is performed. .
[68]
[69]
The step includes preparing a monomer composition by mixing the water-soluble ethylenically unsaturated monomer, an internal crosslinking agent, and a polymerization initiator, and thermally or photopolymerizing the monomer composition to form a hydrogel polymer.
[70]
[71]
The water-soluble ethylenically unsaturated monomer may be any monomer commonly used in the preparation of super absorbent polymers. As a non-limiting example, the water-soluble ethylenically unsaturated monomer may be a compound represented by the following Chemical Formula 1:
[72]
[Formula 1]
[73]
R 1 -COOM 1
[74]
In Formula 1,
[75]
R 1 is an alkyl group having 2 to 5 carbon atoms including an unsaturated bond,
[76]
M 1 is a hydrogen atom, a monovalent or divalent metal, an ammonium group, or an organic amine salt.
[77]
[78]
Preferably, the monomer may be at least one selected from the group consisting of (meth)acrylic acid and monovalent (alkali) metal salts, divalent metal salts, ammonium salts and organic amine salts of these acids.
[79]
[80]
As such, when (meth)acrylic acid and/or a salt thereof is used as the water-soluble ethylenically unsaturated monomer, it is advantageous because a superabsorbent polymer with improved water absorption can be obtained. In addition, the monomer includes 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, N-substituted (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, methoxypolyethylene Glycol (meth)acrylate, polyethylene glycol (meth)acrylate, (N,N)-dimethylaminoethyl (meth)acrylate, (N,N)-dimethylaminopropyl (meth)acrylamide and the like can be used.
[81]
[82]
Here, the water-soluble ethylenically unsaturated monomer may have an acidic group, and at least a portion of the acidic group may be neutralized by a neutralizing agent. Specifically, in the mixing of the water-soluble ethylenically unsaturated monomer having an acidic group, the internal crosslinking agent, the polymerization initiator, and the neutralizing agent, at least a portion of the acidic groups of the water-soluble ethylenically unsaturated monomer may be neutralized. In this case, as the neutralizing agent, a basic material such as sodium hydroxide, potassium hydroxide, ammonium hydroxide, etc. that can neutralize an acidic group may be used.
[83]
[84]
In addition, the degree of neutralization of the water-soluble ethylenically unsaturated monomer, which refers to the degree of neutralization by the neutralizing agent among the acidic groups included in the water-soluble ethylenically unsaturated monomer, is 50 to 90 mol%, or, 60 to 85 mol%, or 65 to 85 mole %, or 70 to 80 mole %. 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 is precipitated and it may be difficult for polymerization to proceed smoothly. It can exhibit properties like elastic rubber, which is difficult to handle.
[85]
[86]
In addition, the term 'internal crosslinking agent' used in this specification is a term used to distinguish it from a surface crosslinking agent for crosslinking the surface of the base resin, which will be described later. do The crosslinking in the above step proceeds without a surface or an internal division, but by the surface crosslinking process of the base resin to be described later, the surface of the particles of the superabsorbent polymer finally produced has a structure crosslinked by a surface crosslinking agent, and the inside is the inside A crosslinked structure is formed by the crosslinking agent.
[87]
[88]
As the internal crosslinking agent, any compound may be used as long as it enables the introduction of crosslinking during polymerization of the water-soluble ethylenically unsaturated monomer. As a non-limiting example, the internal crosslinking agent is N,N'-methylenebisacrylamide, trimethylolpropane tri(meth)acrylate, ethylene glycol di(meth)acrylate, polyethylene glycol (meth)acrylate, propylene glycol di( Meth) acrylate, polypropylene glycol (meth) acrylate, butanediol di (meth) acrylate, butylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, hexanediol di (meth) ) acrylate, triethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, dipentaerythritol pentaacrylate, glycerin tri(meth)acrylate, penta A polyfunctional crosslinking agent such as erythol tetraacrylate, triarylamine, ethylene glycol diglycidyl ether, propylene glycol, glycerin, or ethylene carbonate may be used alone or in combination of two or more, but is not limited thereto. Preferably, among them, ethylene glycol diglycidyl ether may be used.
[89]
[90]
The internal crosslinking agent may be used in an amount of 0.01 to 5 parts by weight based on 100 parts by weight of the water-soluble ethylenically unsaturated monomer. For example, the internal crosslinking agent is 0.01 parts by weight or more, 0.05 parts by weight or more, 0.1 parts by weight, or 0.45 parts by weight or more, and 5 parts by weight or less, 3 parts by weight or less, 2 parts by weight based on 100 parts by weight of the water-soluble ethylenically unsaturated monomer part by weight or less, 1 part by weight or less, or 0.7 part by weight or less. If the content of the upper internal crosslinking agent is too low, crosslinking does not occur sufficiently, and it may be difficult to implement strength above an appropriate level.
[91]
[92]
In addition, the polymerization initiator may be appropriately selected depending on the polymerization method. When using the thermal polymerization method, a thermal polymerization initiator is used, and when using the photopolymerization method, a photopolymerization initiator is used, and a hybrid polymerization method (thermal and light). both of the thermal polymerization initiator and the photopolymerization initiator can be used. However, even by the photopolymerization method, a certain amount of heat is generated by light irradiation such as ultraviolet irradiation, and a certain amount of heat is generated according to the progress of the polymerization reaction, which is an exothermic reaction, so a thermal polymerization initiator may be additionally used.
[93]
[94]
The photopolymerization initiator may be used without limitation in its composition as long as it is a compound capable of forming radicals by light such as ultraviolet rays.
[95]
[96]
As the photopolymerization initiator, for example, benzoin ether, dialkyl acetophenone, hydroxyl alkylketone, phenyl glyoxylate, benzyl dimethyl ketal Ketal), acyl phosphine (acyl phosphine) and alpha-aminoketone (α-aminoketone) may be used at least one selected from the group consisting of. On the other hand, specific examples of acylphosphine include diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide, phenylbis (2,4,6-trimethylbenzoyl) phosphine oxide, ethyl (2,4,6- trimethylbenzoyl)phenylphosphinate etc. are mentioned. A more diverse photoinitiator is well described in Reinhold Schwalm's book "UV Coatings: Basics, Recent Developments and New Application (Elsevier 2007)" p115, but is not limited to the above-described examples.
[97]
[98]
In addition, as the thermal polymerization initiator, at least one selected from the group consisting of a persulfate-based initiator, an azo-based initiator, hydrogen peroxide, and ascorbic acid may be used. Specifically, examples of the persulfate-based initiator include sodium persulfate (Na 2 S 2 O 8 ), potassium persulfate (K 2 S 2 O 8 ), ammonium persulfate (Ammonium persulfate; (NH 4 ) 2 S 2 O 8) and the like, and examples of the azo initiator include 2,2-azobis-(2-amidinopropane) dihydrochloride (2,2-azobis(2-amidinopropane) dihydrochloride), 2,2-azobis -(N,N-dimethylene)isobutyramidine dihydrochloride (2,2-azobis-(N,N-dimethylene)isobutyramidine dihydrochloride), 2-(carbamoylazo)isobutyronitrile (2-(carbamoylazo) )isobutylonitril), 2,2-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride (2,2-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride ), 4,4-azobis-(4-cyanovaleric acid) (4,4-azobis-(4-cyanovaleric acid)) and the like. More various thermal polymerization initiators are well described in Odian's book 'Principle of Polymerization (Wiley, 1981)', p203, and are not limited to the above-described examples.
[99]
[100]
The polymerization initiator may be used in an amount of 2 parts by weight or less based on 100 parts by weight of the water-soluble ethylenically unsaturated monomer. That is, when the concentration of the polymerization initiator is too low, the polymerization rate may be slowed and the residual monomer may be extracted in a large amount 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 constituting the network is shortened, so that the content of the water-soluble component is increased and the physical properties of the resin may be lowered, such as lowered absorbency under pressure, which is not preferable.
[101]
[102]
The monomer composition may further include additives such as a thickener, a plasticizer, a preservation stabilizer, and an antioxidant, if necessary.
[103]
[104]
In addition, the monomer composition including the monomer may be in a solution state dissolved in a solvent such as water, and the solid content in the monomer composition in the solution state, that is, the concentration of the monomer, the internal crosslinking agent, and the polymerization initiator It may be appropriately adjusted in consideration of time and reaction conditions. For example, the solid content in the monomer composition may be 10 to 80% by weight, or 15 to 60% by weight, or 20 to 40% by weight.
[105]
[106]
When the monomer composition has a solid content in the above range, it is not necessary to remove unreacted monomers after polymerization by using the gel effect phenomenon that occurs in the polymerization reaction of a high concentration aqueous solution. It can be advantageous to control.
[107]
[108]
The solvent that can be used at this time can be used without limitation in its composition as long as it can dissolve the above-mentioned components, for example, water, 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, diethylene glycol ethyl At least one selected from ether, toluene, xylene, butyrolactone, carbitol, methyl cellosolve acetate and N,N-dimethylacetamide may be used in combination.
[109]
[110]
On the other hand, cross-linking polymerization of a water-soluble ethylenically unsaturated monomer having at least a partially neutralized acidic group may be carried out without particular limitation on the structure, as long as the hydrogel polymer can be formed by thermal polymerization, photopolymerization, or hybrid polymerization.
[111]
[112]
Specifically, the polymerization method is largely divided into thermal polymerization and photopolymerization depending on the polymerization energy source. In general, when thermal polymerization is carried out, it may be carried out in a reactor having a stirring shaft such as a kneader. The process may be carried out in a reactor equipped with a conveyor belt or in a flat-bottomed vessel, but the polymerization method described above is an example, and the present invention is not limited to the polymerization method described above.
[113]
[114]
For example, as described above, the hydrogel polymer obtained by thermal polymerization by supplying hot air or heating the reactor to a reactor such as a kneader having a stirring shaft is fed to the reactor outlet according to the shape of the stirring shaft provided in the reactor. The discharged hydrogel polymer may be in the form of several centimeters to several millimeters. Specifically, the size of the hydrogel polymer obtained may vary depending on the concentration and injection rate of the monomer composition to be injected, and usually, a hydrogel polymer having a weight average particle diameter of 2 to 50 mm can be obtained.
[115]
[116]
In addition, as described above, when photopolymerization is carried out in a reactor equipped with a movable conveyor belt or in a flat-bottomed container, the generally obtained hydrogel polymer may be a sheet-like hydrogel polymer having the width of the belt. At this time, the thickness of the polymer sheet varies depending on the concentration of the injected monomer composition and the injection rate or injection amount, but it is preferable to supply the monomer composition so that a polymer sheet having a thickness of about 0.5 to about 5 cm can be obtained. . When the monomer composition is supplied so that the thickness of the polymer on the sheet is too thin, the production efficiency is low, which is not preferable. it may not be
[117]
[118]
In this case, the typical water content of the hydrogel polymer obtained by this method may be about 40 to about 80 wt%. Meanwhile, in the present specification, "moisture content" refers to the amount of moisture occupied with respect to the total weight of the hydrogel polymer, and refers to a value obtained by subtracting the weight of the polymer in a dry state from the weight of the hydrogel polymer. Specifically, it is defined as a value calculated by measuring the weight loss due to evaporation of moisture in the polymer during drying by raising the temperature of the polymer in the crumb state through infrared heating. At this time, the drying conditions are set to 40 minutes including 5 minutes of the temperature rise step in such a way that the temperature is raised from room temperature to about 180° C. and then maintained at 180° C., and the moisture content is measured.
[119]
[120]
Base resin powder forming step
[121]
Next, the hydrogel polymer is dried, pulverized, and classified to obtain a base resin powder.
[122]
[123]
In the above step, the hydrogel polymer is dried and pulverized to have a particulate form, and thus, the prepared base resin is in the form of a powder composed of crosslinked polymer particles. Specifically, the base resin powder may be a crosslinked polymer particle having a particle diameter of about 150 μm to about 850 μm, based on the total weight of 75 wt% or more, preferably 80 wt% or more, or 90 wt% or more. On the other hand, when the sodium dodecyl sulfate compound used in the surface crosslinking step to be described later is used in the polymerization step of the base resin, the fine powder having a particle diameter of less than about 150 μm increases, and the strength of the superabsorbent polymer is increased by the fine powder. In addition, as the fine powder increases, the yield of the superabsorbent polymer finally manufactured may be relatively reduced, and thus economic efficiency may be somewhat deteriorated.
[124]
[125]
On the other hand, the step of preparing the base resin powder may include a step of coarsely pulverizing the hydrogel polymer before drying in order to increase drying efficiency.
[126]
[127]
At this time, the grinder used is not limited in configuration, and specifically, a vertical pulverizer, a turbo cutter, a turbo grinder, a rotary cutter mill, a cutting Including any one selected from the group of crushing devices consisting of a cutter mill, a disc mill, a shred crusher, a crusher, a chopper, and a disc cutter However, it is not limited to the above-described example.
[128]
[129]
Through this coarse grinding process, the particle diameter of the hydrogel polymer can be adjusted to about 0.1 to about 10 mm. Grinding so that the particle diameter is less than 0.1 mm is not technically easy due to the high moisture content of the hydrogel polymer, and a phenomenon of agglomeration between the pulverized particles may occur. On the other hand, when pulverizing so that the particle diameter exceeds 10 mm, the effect of increasing the efficiency of the subsequent drying step may be insignificant.
[130]
[131]
Drying is performed on the hydrogel polymer immediately after polymerization that has not been subjected to the coarse grinding process or to the coarse grinding process as described above. At this time, the drying temperature may be about 60 ℃ to about 250 ℃. At this time, if the drying temperature is less than about 70 ℃, the drying time may be too long, if the drying temperature exceeds about 250 ℃, only the surface of the polymer is excessively dried, fine powder may occur in the subsequent grinding process, and final formation There is a possibility that the physical properties of the superabsorbent polymer to be used may decrease. Therefore, preferably, the drying may be carried out at a temperature of about 100 °C to about 240 °C, more preferably at a temperature of about 110 °C to about 220 °C.
[132]
[133]
In addition, the drying time may be carried out for about 20 minutes to about 12 hours in consideration of process efficiency and the like. For example, it may be dried for about 10 minutes to about 100 minutes, or about 20 minutes to about 60 minutes.
[134]
[135]
If the drying method of the drying step is also commonly used, it may be selected and used without limitation in its configuration. Specifically, the drying step may be performed by a method such as hot air supply, infrared irradiation, microwave irradiation, or ultraviolet irradiation. After the drying step, the moisture content of the polymer may be about 0.1 to about 10% by weight.
[136]
[137]
Thereafter, a step of pulverizing the dried polymer obtained through the drying step may be performed. The pulverizing step is a step for optimizing the surface area of ​​the dried polymer, and the pulverized cross-linked polymer may have a particle diameter of about 150 μm to about 850 μm. Here, the particle size of the pulverized crosslinked polymer may be measured according to the European Disposables and Nonwovens Association (EDANA) standard EDANA WSP 220.3 method.
[138]
[139]
At this time, the pulverizer used for pulverization is specifically, a pin mill, a hammer mill, a screw mill, a roll mill, a disc mill, or a jog mill ( jog mill), but is not limited to the above-described example.
[140]
[141]
Formation of superabsorbent polymer particles (surface crosslinking step)
[142]
Next, a step of surface-crosslinking the prepared base resin powder in the presence of a surface crosslinking solution containing a cyclic carbonate-based surface crosslinking agent and sodium dodecyl sulfate to form superabsorbent polymer particles is performed.
[143]
Here, as for the components, content, and mechanism of action of the cyclic carbonate-based surface crosslinking agent and sodium dodecyl sulfate, all of the above contents may be equally applied.
[144]
[145]
On the other hand, the method of mixing the cyclic carbonate-based surface crosslinking agent and the sodium dodecyl sulfate to the base resin powder is not particularly limited as long as they can be mixed evenly and may be appropriately adopted and used.
[146]
[147]
For example, the cyclic carbonate-based surface crosslinking agent and sodium dodecyl sulfate may be mixed with the base resin powder in a solution state, specifically, in a surface crosslinking solution state dissolved in water. At this time, the surface crosslinking solution is prepared by mixing the surface crosslinking agent, sodium dodecyl sulfate compound and the base resin powder in a reaction tank, or by putting the base resin powder in a mixer and spraying the surface crosslinking agent and sodium dodecyl sulfate compound in a continuously operated mixer. A method of continuously supplying and mixing the base resin powder, the surface crosslinking agent, and the sodium dodecyl sulfate compound may be used.
[148]
[149]
In this case, when the content of solids in the surface crosslinking solution is 1 wt% or more, 3 wt% or more, 5 wt% or more, 10 wt% or more, or 50 wt% or less, 30 wt% or less, or 20 wt% or less, the base resin It is suitable to be uniformly dispersed in the powder, and at the same time, it is possible to prevent agglomeration of the base resin powder.
[150]
[151]
Specifically, in the surface crosslinking step, a mixture of a surface crosslinking solution and a base resin powder is heat treated to form a surface crosslinking layer on the surface of the base resin powder to form superabsorbent polymer particles. Accordingly, the prepared superabsorbent polymer particles may have a surface cross-linked layer formed on a portion of the surface of the cross-linked polymer by additional cross-linking via a cyclic carbonate-based surface cross-linking agent and sodium dodecyl sulfate.
[152]
[153]
On the other hand, in the surface crosslinking step, the unsaturated bonds of the water-soluble ethylenically unsaturated monomer remaining on the surface without being crosslinked in the hydrogel polymer formation step are crosslinked by the surface crosslinking agent, thereby forming a superabsorbent polymer with increased surface crosslinking density. can The surface cross-linking density, that is, the external cross-linking density, is increased by this temperature increase, that is, the heat treatment process, while the internal cross-linking density is not changed. do.
[154]
[155]
Meanwhile, the step of forming a surface cross-linking layer by adding an inorganic material to the mixture may be performed. As the inorganic material, at least one inorganic material selected from the group consisting of silica, clay, alumina, silica-alumina composite, titania, zinc oxide, and aluminum sulfate may be used. The inorganic material may be used in powder form or liquid form, and in particular, may be used as alumina powder, silica-alumina powder, titania powder, or nano silica solution. In addition, the inorganic material may be used in an amount of about 0.001 to about 1 part by weight based on 100 parts by weight of the base resin.
[156]
[157]
The temperature of the heat treatment of the mixture, that is, the step of surface crosslinking to form superabsorbent polymer particles is not particularly limited, but may be performed, for example, at 150° C. to 200° C. for 40 to 100 minutes, preferably At 160 °C to 190 °C, 50 to 90 minutes, or 170 °C to 180 °C, 50 to 70 minutes may be performed.
[158]
[159]
When the above-mentioned surface crosslinking process temperature conditions are satisfied, the surface of the base resin powder is sufficiently crosslinked, and the generation of fine powder is reduced by using a cyclic carbonate-based surface crosslinking agent and sodium dodecyl sulfate at the same time, and the absorption capacity and initial absorption rate of the superabsorbent polymer etc. are improved, and excellent effects such as improvement of liquid permeability and suppression of re-wetting can be obtained.
[160]
[161]
A means for increasing the temperature for the heat treatment of the mixture is not particularly limited. It can be heated by supplying a heating medium or by directly supplying a heat source. At this time, as the type of heating medium that can be used, a fluid having an elevated temperature such as steam, hot air, or hot oil may be used, but the present invention is not limited thereto. Considering it, it can be appropriately selected. On the other hand, the directly supplied heat source may be a heating method through electricity or a heating method through a gas, but is not limited to the above-described example.
[162]
[163]
Meanwhile, the manufacturing method may further include classifying the base resin powder made of the crosslinked polymer having the surface crosslinked layer formed thereon.
[164]
[165]
It is possible to manage the physical properties of the superabsorbent polymer powder to be finally manufactured through the step of classifying the base resin powder made of the crosslinked polymer having the surface crosslinking layer formed thereon according to the particle size. It is appropriate that the superabsorbent polymer obtained therefrom through a process such as pulverization and classification is prepared and provided to have a particle diameter of about 150 to 850 μm. More specifically, about 90 wt%, preferably 95 wt% or more of the base resin on which the surface crosslinking layer is formed has a particle diameter of about 150 to 850 μm.
[166]
[167]
As described above, as the particle size distribution of the superabsorbent polymer particles is adjusted to a desirable range, the final manufactured superabsorbent polymer may exhibit excellent absorbent properties. Accordingly, in the classification step, the polymer having a particle diameter of about 150 to about 850 μm may be classified and commercialized.
[168]
[169]
The superabsorbent polymer prepared according to the above-described manufacturing method uses the cyclic carbonate-based compound and sodium dodecyl sulfate at the same time in the surface crosslinking step to improve the water holding capacity and absorbency under pressure, which are basic physical properties of the superabsorbent polymer, Excellent liquid permeability can be exhibited with a fast initial absorption rate.
[170]
[171]
Super absorbent resin composition
[172]
Meanwhile, according to another embodiment of the present invention, there is provided a superabsorbent polymer composition prepared according to the above-described manufacturing method.
[173]
[174]
The superabsorbent polymer composition includes: superabsorbent polymer particles comprising a crosslinked polymer of a water-soluble ethylenically unsaturated monomer having at least a partially neutralized acidic group;
[175]
A surface crosslinking layer formed by additional crosslinking of the crosslinked polymer via a cyclic carbonate-based surface crosslinking agent and sodium dodecyl sulfate is further included on a part of the surface of the superabsorbent polymer particles.
[176]
[177]
For the description of the water-soluble ethylenically unsaturated monomer, the internal crosslinking agent, the cyclic carbonate-based surface crosslinking agent, and sodium dodecyl sulfate used in the superabsorbent polymer, refer to the above bar.
[178]
[179]
On the other hand, the super absorbent polymer may have a fast absorption rate by reducing the generation of fine powder without reducing physical properties such as water holding capacity and absorbency under pressure.
[180]
[181]
For example, the superabsorbent polymer (meaning the form of particles) may have a vortex time of 50 seconds to 65 seconds, preferably 50 seconds to 60 seconds, or 50 seconds to 55 seconds. The absorption rate is excellent, so that the value is small.
[182]
The absorption rate was measured in seconds according to the method described in International Patent Publication No. 1987-003208. Specifically, the absorption rate (or vortex time) is determined by adding 2 g of superabsorbent resin to 50 mL of physiological saline at 23 ° C to 24 ° C, and stirring a magnetic bar (diameter 8 mm, length 31.8 mm) at 600 rpm to vortex ( It was calculated by measuring the time until the vortex) disappears in seconds. It can be seen that the shorter the time, the faster the superabsorbent polymer has an initial absorption rate.
[183]
[184]
In addition, the superabsorbent polymer has a water holding capacity (CRC) of about 27 g/g or more, or about 29 g/g or more, or about 30 g/g or more, measured according to EDANA method WSP 241.3, and about 40 g/g/g/g or more. g or less, or about 38 g/g or less, or about 35 g/g or less.
[185]
[186]
In addition, the superabsorbent polymer has an absorbency under pressure (AUP) of 0.7 psi measured according to the method of WSP 242.3 of the EDANA method of 23 g/g or more, and 29 g/g or less, 26 g/g or less, or 23 g/g or less. can
[187]
[188]
As described above, the superabsorbent polymer composition of the present invention has excellent absorbency and has a fast initial absorption rate, so that a high-quality sanitary material can be provided.
[189]
[190]
Hereinafter, through specific examples of the invention, the operation and effect of the invention will be described in more detail. However, these embodiments are merely presented as an example of the invention, and the scope of the invention is not defined thereby.
[191]
[192]
[Example]
[193]

[194]
Example 1
[195]
In a 3L glass container equipped with a stirrer and a thermometer, 450 g of acrylic acid, 2000 ppm of polyethylene glycol diacrylate (PEGDA 400, Mw=400) as an internal crosslinking agent, and diphenyl (2,4,6-trimethylbenzoyl)-phosphine oxide as a photoinitiator After dissolution by adding 80 ppm of seeds, 618 g of 31.5% sodium oxide solution was added to prepare a water-soluble unsaturated monomer aqueous solution (degree of neutralization: 73 mol%; solid content: 45.1 wt%). When the temperature of the water-soluble unsaturated monomer aqueous solution rises to 40° C. due to heat of neutralization, the mixture is placed in a container containing 2400 ppm of sodium persulfate (SPS), a thermal polymerization initiator, and then irradiated with ultraviolet light for 1 minute ( Irradiation dose: 10 mV/cm 2 ), UV polymerization was carried out, and aging was performed by applying heat in an oven at 80° C. for 120 seconds to obtain a hydrogel polymer sheet. The obtained hydrogel polymer sheet was passed through a chopper having a hole size of 16 mm to prepare crumb. The crumb was dried in an oven capable of transferring air volume up and down. Hot air at 185° C. was flowed from the bottom to the top for 15 minutes and from the top to the bottom for 15 minutes to dry uniformly, and the moisture content of the dried body after drying was made to be 2% or less. Through the drying process in this way, the base resin powder having a particle size of 150 to 850 μm was obtained by classifying through a standard mesh sieve of ASTM standard.
[196]
[197]
Then, based on 100 parts by weight of the prepared base resin powder, ethylene carbonate 0.6 parts by weight, propylene carbonate 0.6 parts by weight, propylene glycol 0.6 parts by weight, glycerol carbonate 0.6 parts by weight, aluminum sulfate 0.4 parts by weight, sodium dodecyl sulfate 0.005 parts by weight and 5.4 parts by weight of water to prepare a surface crosslinking solution.
[198]
[199]
Thereafter, the surface crosslinking solution was sprayed on the base resin powder and stirred at room temperature to evenly distribute the surface crosslinking solution on the base resin powder, followed by mixing at 1000 rpm for 30 seconds. Then, the base resin powder mixed with the surface crosslinking solution was put into a surface crosslinking reactor, and a surface crosslinking reaction was performed. In this surface crosslinking reactor, it was confirmed that the temperature of the base resin powder was gradually increased from the initial temperature of around 80°C, and it was operated to reach the maximum reaction temperature of 188°C after 40 minutes. After reaching the maximum reaction temperature, a sample of the final prepared superabsorbent polymer was taken after further reaction for 30 minutes. After the surface crosslinking process, the superabsorbent polymer was classified with a standard mesh sieve according to ASTM standards to have a particle diameter of 150 μm to 850 μm.
[200]
[201]
Examples 2 to 10 and Comparative Examples 1 to 4
[202]
A superabsorbent polymer composition was prepared in the same manner as in Example 1, except that the components and contents of Table 1 were used.
[203]
[204]
[Table 1]
division surface crosslinking agent* Surfactants Other additives*
EC PC GC SDS 1,3-PD
Example 1 0.6 0.6 0.6 0.005 -
Example 2 0.6 0.6 0.6 0.01 -
Example 3 0.6 0.6 0.6 0.02 -
Example 4 0.8 0.6 0.6 0.01 -
Example 5 0.6 0.8 0.6 0.01 -
Example 6 0.6 0.6 0.8 0.01 -
Example 7 1.8 - - 0.01 -
Example 8 - - 1.8 0.01 -
Example 9 0.9 0.9 - 0.01 -
Example 10 - 0.9 0.9 0.01 -
Comparative Example 1 0.6 0.6 0.6 - -
Comparative Example 2 - - - 0.01 -
Comparative Example 3 - - - 0.01 0.3
Comparative Example 4 0.6 0.6 0.6 - 0.3
The components of the surface crosslinking agent, surfactant and other additives are based on 100 parts by weight of the base resin. EC: Etylene carbonatePC: Propylene carbonateGC: Glycerol carbonateSDS: Sodium dodecyl sulfate1,3-PD: 1,3-propanediol
[205]

[206]
Even when the physical properties of the superabsorbent polymer compositions prepared in Examples and Comparative Examples were evaluated in the following manner, the results are shown in Table 2.
[207]
[208]
Unless otherwise indicated, all of the following physical property evaluations were performed at room temperature (25° C.), and physiological saline or saline means 0.9 wt% sodium chloride (NaCl) aqueous solution.
[209]
(1) Centrifuge Retention Capacity (CRC)
[210]
Among the superabsorbent polymers, those having a particle diameter of 150 to 850 μm were taken, and centrifugal retention capacity (CRC) was measured according to the absorption magnification under no load according to the European Disposables and Nonwovens Association (EDANA) standard EDANA WSP 241.3. .
[211]
Specifically, from the resins obtained through Examples and Comparative Examples, a resin classified through a sieve of #30-50 was obtained. This resin W0 (g) (about 0.2 g) was uniformly put in a non-woven bag and sealed, and then immersed in physiological saline (0.9 wt %) at room temperature. After 30 minutes, the bag was drained of water for 3 minutes under the conditions of 250G using a centrifuge, and the mass W2 (g) of the bag was measured. Moreover, after performing the same operation without using resin, the mass W1 (g) at that time was measured. Using each obtained mass, CRC (g/g) was calculated according to the following formula.
[212]
[Equation 2]
[213]
CRC (g/g) = {[W2(g) - W1(g)]/W0(g)} - 1
[214]
[215]
(2) Absorbency Under Pressure (AUP)
[216]
The absorbency under pressure of 0.7 psi of each resin was measured according to the EDANA method WSP 242.3. At the time of measuring the absorbency under pressure, the resin fraction at the time of the CRC measurement was used.
[217]
Specifically, a stainless steel 400 mesh wire mesh was mounted on the bottom of a plastic cylinder having an inner diameter of 25 mm. A piston capable of uniformly spreading the absorbent resin W0(g) (0.16 g) on ​​the wire mesh under conditions of room temperature and humidity of 50% and applying a load of 0.7 psi (or 0.3, 0.9 psi) more uniformly thereon It is slightly smaller than the outer diameter of 25 mm, there is no gap with the inner wall of the cylinder, and the vertical movement is not disturbed. At this time, the weight W3 (g) of the device was measured.
[218]
A glass filter having a diameter of 90 mm and a thickness of 5 mm was placed inside a 150 mm diameter Petro dish, and physiological saline composed of 0.9 wt% sodium chloride was placed at the same level as the upper surface of the glass filter. One filter paper having a diameter of 90 mm was loaded thereon. The measuring device was placed on the filter paper, and the liquid was absorbed under load for 1 hour. After 1 hour, the measuring device was lifted and the weight W4 (g) was measured.
[219]
Using each obtained mass, absorbency under pressure (g/g) was calculated according to the following equation.
[220]
[Equation 3]
[221]
AUP(g/g) = [W4(g) - W3(g)]/W0(g)
[222]
[223]
(3) Absorption rate by vortex method (vortex time)
[224]
The absorption rates of the superabsorbent polymers of Examples and Comparative Examples were measured in seconds according to the method described in International Patent Publication No. 1987-003208.
[225]
Specifically, for the absorption rate (or vortex time), 2 g of superabsorbent polymer is added to 50 mL of physiological saline at 23°C to 24°C, and a magnetic bar (diameter 8 mm, length 31.8 mm) is stirred at 600 rpm to vortex. It was calculated by measuring the time until the (vortex) disappears in seconds.
[226]
[227]
Table 2 below shows the physical properties of the superabsorbent polymer after surface crosslinking with respect to the Examples and Comparative Examples.
[228]
[Table 2]
division CRC (g/g) Vortex time(sec) 0.7 AUP (g/g)
Example 1 32.6 61 25.2
Example 2 32.6 54 25.3
Example 3 32.5 51 25.1
Example 4 31.0 55 24.0
Example 5 31.2 56 22.0
Example 6 32.1 53 25.5
Example 7 32.3 65 24.2
Example 8 33.1 59 22.0
Example 9 32.2 63 25.5
Example 10 32.0 65 22.9
Comparative Example 1 32.1 67 25.6
Comparative Example 2 40.0 55 12.2
Comparative Example 3 32.2 62 21.1
Comparative Example 4 29.0 70 22.6
[229]
Referring to Table 2, it can be seen that the superabsorbent polymer composition prepared by using the cyclic carbonate-based surface crosslinking agent and sodium dodecyl sulfate in the crosslinking step according to the preparation method of the present application exhibits excellent absorption performance.
[230]
In the case of comparative examples in which the cyclic carbonate-based surface crosslinking agent and/or sodium dodecyl sulfate were not used in the surface crosslinking step, the centrifugal separation capacity and absorbency under pressure were lowered, and in particular, the absorption rate by the vortex method was significantly increased. could confirm that
[231]
In Comparative Examples 2 and 3, the surface crosslinking was not sufficiently performed, so the absorption rate could be equivalent to that of the Example, but it was confirmed that the absorbency under pressure was significantly reduced.

WE CLAIMS

forming a hydrogel polymer by crosslinking and polymerizing a water-soluble ethylenically unsaturated monomer having an acidic group at least partially neutralized in the presence of an internal crosslinking agent; drying, pulverizing, and classifying the hydrogel polymer to obtain a base resin powder; and surface-crosslinking the base resin powder in the presence of a surface crosslinking solution containing a cyclic carbonate-based surface crosslinking agent and sodium dodecyl sulfate to form superabsorbent polymer particles.
[Claim 2]
The method of claim 1, wherein the cyclic carbonate-based surface crosslinking agent comprises at least one selected from the group consisting of ethylene carbonate, propylene carbonate, and glycerol carbonate.
[Claim 3]
The method of claim 1 , wherein the cyclic carbonate-based surface crosslinking agent is included in an amount of 0.5 to 5 parts by weight based on 100 parts by weight of the base resin.
[Claim 4]
According to claim 1, wherein the cyclic carbonate-based surface crosslinking agent, with respect to 100 parts by weight of the surface crosslinking agent, ethylene carbonate 10 to 50 parts by weight, propylene carbonate 10 to 50 parts by weight, and glycerol carbonate 10 to 50 parts by weight comprising, A method for preparing a superabsorbent polymer composition.
[Claim 5]
The method of claim 1, wherein the sodium dodecyl sulfate is included in an amount of 0.001 to 1.0 parts by weight based on 100 parts by weight of the base resin.
[Claim 6]
The method of claim 1 , wherein the step of surface-crosslinking to form superabsorbent polymer particles is performed at 150° C. to 200° C. for 40 to 100 minutes.
[Claim 7]
Superabsorbent polymer particles comprising a crosslinked polymer of a water-soluble ethylenically unsaturated monomer having at least partially neutralized acidic groups; A superabsorbent polymer composition further comprising a surface cross-linking layer formed by additional cross-linking of the cross-linked polymer through a medium.
[Claim 8]
The superabsorbent polymer composition according to claim 7, wherein the absorption rate (vortex time) is 50 seconds to 65 seconds.