Title of the invention: Super absorbent polymer manufacturing method and super absorbent polymer
Technical field
[One]
Cross-reference with related application(s)
[2]
This application claims the benefit of priority based on Korean Patent Application No. 10-2018-0116453 filed on September 28, 2018, and all contents disclosed in the documents of the Korean patent application are incorporated as part of this specification.
[3]
The present invention relates to a method for producing a super absorbent polymer having excellent properties such as basic water absorption and liquid permeability by optimizing the degree of crosslinking of the base resin powder and the surface crosslinking layer, and to a super absorbent polymer prepared through the same.
Background
[4]
Super Absorbent Polymer (SAP) is a synthetic polymer material with a function of absorbing moisture of 500 to 1,000 times its own weight, and each developer has a SAM (Super Absorbency Material), AGM (Absorbent Gel). Material) and so on. Since the above-described superabsorbent resin has begun to be put into practical use as a sanitary tool, nowadays, in addition to hygiene products such as paper diapers for children, soil repair agents for horticultural use, water resistant materials for civil engineering and construction, sheets for seedlings, freshness maintenance agents in the food distribution field, and It is widely used as a material for poultice.
[5]
In most cases, such superabsorbent resins are widely used in the field of sanitary materials such as diapers and sanitary napkins, and for this purpose, it is necessary to exhibit a high absorption ability for moisture, etc., and moisture absorbed by external pressure must not escape ( High absorption capacity under pressure), 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).
[6]
In recent years, as the demand for a thin diaper increases, the content of fibrous materials such as pulp in the diaper decreases, and the proportion of the superabsorbent polymer tends to increase relatively. Therefore, there is a need for a super absorbent polymer to have the performance that was in charge of the diaper fiber material, and for this purpose, the super absorbent polymer must have a high absorption capacity as well as a high absorption rate and liquid permeability. In particular, as the diaper becomes thinner, the risk of urine leaking out of the diaper increases according to the movement of a baby who is a diaper user. Accordingly, the demand for a high absorption rate for the super absorbent polymer is increasing.
[7]
However, due to the structural characteristics of the super absorbent polymer, it is known that it is very difficult to simultaneously improve the water absorption capacity and absorption rate, and the absorption capacity and liquid permeability under high pressure. In the case of absorbency and liquid permeability under pressure, the crosslinking density of the surface crosslinked layer and the gel strength of the super absorbent polymer particles must be increased.In this case, the absorption capacity and absorption rate are increased to the internal crosslinking density of the base resin powder inside the surface crosslinked layer. This is because there is a tendency to decrease.
[8]
As a result, there is a continuous demand for the development of a technology capable of optimizing the degree of crosslinking of the base resin powder and the surface crosslinked layer, and simultaneously exhibiting excellent basic water absorption capacity and absorption rate, and liquid permeability and absorption capacity under pressure.
Detailed description of the invention
Technical challenge
[9]
The present invention provides a method for producing a super absorbent polymer having excellent properties such as basic water absorption and liquid permeability by optimizing the degree of crosslinking between the base resin powder and the surface crosslinked layer.
[10]
The present invention is also manufactured by the above manufacturing method to provide a super absorbent polymer having excellent properties such as basic water absorption and liquid permeability.
Means of solving the task
[11]
The present invention provides a crosslinking polymerization of a monomer composition comprising a water-soluble ethylenically unsaturated monomer and an internal crosslinking agent having an acidic group at least partially neutralized to form a hydrogel polymer;
[12]
Drying, pulverizing and classifying the hydrogel polymer to form a base resin powder; And
[13]
In the presence of a surface crosslinking agent, comprising the step of forming a surface crosslinking layer by further crosslinking the surface of the base resin powder,
[14]
In the step of forming the hydrogel polymer, the water-soluble ethylenically unsaturated monomer has a degree of neutralization of less than 70 mol%,
[15]
During the step of forming the surface crosslinking layer or after the step of forming the surface crosslinking layer, a method for producing a super absorbent polymer further comprising the step of further neutralizing the base resin powder by treating the base resin powder with a basic solution. to provide.
[16]
The present invention also provides a base resin powder comprising a first crosslinked polymer of a water-soluble ethylenically unsaturated monomer having an acidic group at least partially neutralized; And
[17]
A super absorbent polymer comprising a surface crosslinked layer formed on the base resin powder, wherein the first crosslinked polymer is further crosslinked via a surface crosslinking agent,
[18]
The neutralization degree measured for the water-soluble component of the super absorbent polymer is more than 70 mol%,
[19]
Centrifugation water retention capacity (CRC) for 30 minutes for physiological saline (0.9% by weight aqueous sodium chloride solution) is 28 g/g or more,
[20]
A superabsorbent polymer having a flow induction property (SFC; 10 -7 cm 3 s/g) of 30 (10 -7 cm 3 s/g) or more of physiological saline (0.685 wt% sodium chloride aqueous solution) is provided.
[21]
Hereinafter, a super absorbent polymer and a method of manufacturing the same according to a specific embodiment of the present invention will be described in more detail. However, this is presented as an example of the invention, whereby the scope of the rights of the invention is not limited, and it is obvious to those skilled in the art that various modifications to the embodiments are possible within the scope of the rights of the invention.
[22]
Additionally, unless otherwise specified, the term "comprising" or "containing" throughout the specification refers to including any component (or component) without any particular limitation, and the addition of other components (or components) It cannot be interpreted as excluding.
[23]
According to one embodiment of the present invention, crosslinking polymerization of a monomer composition comprising a water-soluble ethylenically unsaturated monomer having at least a partially neutralized acidic group and an internal crosslinking agent to form a hydrogel polymer;
[24]
Drying, pulverizing and classifying the hydrogel polymer to form a base resin powder; And
[25]
In the presence of a surface crosslinking agent, comprising the step of forming a surface crosslinking layer by further crosslinking the surface of the base resin powder,
[26]
In the step of forming the hydrogel polymer, the water-soluble ethylenically unsaturated monomer has a degree of neutralization of less than 70 mol%,
[27]
During the step of forming the surface crosslinking layer or after the step of forming the surface crosslinking layer, the method for producing a super absorbent polymer further comprises the step of further neutralizing the base resin powder by treating the base resin powder with a basic solution. Is provided.
[28]
In the method for preparing a super absorbent polymer of one embodiment, after performing an initial neutralization process for the monomer so that the neutralization degree of the monomer for crosslinking polymerization is less than 70 mol%, or 40 to 69 mol%, or 50 to 65 mol% , Crosslinking polymerization, etc. to form a base resin powder, and in performing the surface crosslinking step for the base resin powder, during the step of forming the surface crosslinking layer, after the step of forming the surface crosslinking layer, a basic solution was used. It is to proceed further with additional neutralization steps.
[29]
As a result of continuous experiments of the present inventors, after preparing the base resin powder by controlling the degree of neutralization of the monomer to be relatively low as described above, when forming the surface crosslinking layer or performing an additional neutralization step after formation, the base resin powder and It was found that the degree of crosslinking of the surface crosslinked layer was optimized together, and it was found that it was possible to manufacture a superabsorbent polymer having improved basic absorption capacity and absorption rate, and water permeability and absorption capacity under pressure at the same time.
[30]
This seems to be because the degree of neutralization of the monomer, the base resin powder, and/or the surface crosslinked superabsorbent polymer for the production of the super absorbent polymer may affect the progression of the crosslinking reaction or the degree of crosslinking. However, in the existing process, since the neutralization process was performed only on the monomer before crosslinking polymerization, it was difficult to control the degree of neutralization during/after surface crosslinking.
[31]
However, in the manufacturing method of one embodiment, as the additional neutralization process is performed after the initiation of the surface crosslinking reaction, the degree of neutralization during/after surface crosslinking can be appropriately controlled. As a result, not only the base resin powder, but also the surface crosslinked The degree of crosslinking of the surface crosslinked layer in the super absorbent polymer can also be controlled to a desirable level.
[32]
As a result, the super absorbent polymer prepared by the method of one embodiment is controlled not only the degree of neutralization/crosslinking inside the base resin powder, but also the degree of neutralization/crosslinking of the surface crosslinked layer to a desirable level, and thus, not only the basic absorption capacity and absorption rate , It seems that the liquid permeability and absorption under pressure can exhibit improved properties together.
[33]
Therefore, unlike the conventional common knowledge that it is difficult to improve both the absorption capacity / absorption rate and the absorption capacity / liquid permeability under pressure, the super absorbent polymer prepared by the method of one embodiment can exhibit excellent physical properties of both sides, It can be preferably applied to sanitary materials such as diapers having a thinner thickness.
[34]
Hereinafter, the manufacturing method of one embodiment will be described in more detail for each step.
[35]
In the method of manufacturing a super absorbent polymer of one embodiment, first, the monomer composition, which is a raw material of the super absorbent polymer, has an acidic group and a monomer composition comprising an acrylic acid-based monomer in which at least a part of the acidic group is neutralized, an internal crosslinking agent, and a polymerization initiator Polymerization to obtain a hydrogel polymer, which is dried, pulverized, and classified to form a base resin powder.
[36]
This will be described in more detail below.
[37]
The monomer composition as a raw material of the super absorbent polymer may include an acidic group and a water-soluble ethylenically unsaturated monomer in which at least a part of the acidic group is neutralized, more specifically, an acrylic acid-based monomer and a polymerization initiator.
[38]
The acrylic acid-based monomer is a compound represented by the following Formula 1:
[39]
[Formula 1]
[40]

[41]
In Formula 1,
[42]
R1 is an alkyl group having 2 to 5 carbon atoms containing an unsaturated bond,
[43]
M1 is a hydrogen atom, a monovalent or divalent metal, an ammonium group, or an organic amine salt.
[44]
Preferably, the acrylic acid-based monomer includes at least one selected from the group consisting of acrylic acid, methacrylic acid and monovalent metal salts, divalent metal salts, ammonium salts, and organic amine salts thereof.
[45]
Here, the acrylic acid-based monomer may have an acidic group and at least part of the acidic group is neutralized. Preferably, the monomer partially neutralized with a basic substance such as sodium hydroxide, potassium hydroxide, ammonium hydroxide, or the like may be used. In this case, the degree of neutralization of the acrylic acid-based monomer may be adjusted to less than 70 mol%, or 40 to 69 mol%, or 50 to 65 mol%.
[46]
However, if the degree of neutralization is too high, the polymerization may be difficult to proceed smoothly due to precipitation of neutralized monomers.Moreover, the effect of additional neutralization after the initiation of surface crosslinking is substantially eliminated, and the degree of crosslinking of the surface crosslinking layer is optimized It may not be possible, and the liquid permeability of the super absorbent polymer may not be sufficient. On the contrary, if the degree of neutralization is too low, not only the absorption power of the polymer is greatly reduced, but also it may exhibit properties such as elastic rubber that are difficult to handle.
[47]
The concentration of the monomer may be 20 to 60% by weight, or 30 to 55% by weight, or 40 to 50% by weight, based on the monomer composition including the raw material and the solvent of the super absorbent polymer, and polymerization time and reaction It can be made into an appropriate concentration considering conditions, etc. However, if the concentration of the monomer is too low, the yield of the superabsorbent polymer may be low and economical problems may occur. On the contrary, if the concentration is too high, a part of the monomer is precipitated or the pulverization efficiency is low when the polymerized hydrogel polymer is pulverized. In the process, problems may occur, and the properties of the super absorbent polymer may be deteriorated.
[48]
The polymerization initiator used in the polymerization in the method for preparing the super absorbent polymer of the embodiment is not particularly limited as long as it is generally used for preparing the super absorbent polymer.
[49]
Specifically, the polymerization initiator may be a thermal polymerization initiator or a photopolymerization initiator according to UV irradiation depending on the polymerization method. However, even by the photopolymerization method, a certain amount of heat is generated by irradiation such as UV irradiation, and a certain amount of heat is generated according to the progress of the polymerization reaction, which is an exothermic reaction.
[50]
The photopolymerization initiator may be used without limitation of its configuration as long as it is a compound capable of forming a radical by light such as ultraviolet rays.
[51]
Examples of the photopolymerization initiator include benzoin ether, dialkyl acetophenone, hydroxyl alkylketone, phenyl glyoxylate, and benzyl dimethyl ketone. Ketal), acyl phosphine, and alpha-aminoketone may be used at least one selected from the group consisting of (α-aminoketone). Meanwhile, as a specific example of acylphosphine, a commercially available lucirin TPO, that is, 2,4,6-trimethyl-benzoyl-trimethyl phosphine oxide (2,4,6-trimethyl-benzoyl-trimethyl phosphine oxide) may be used. . More various photoinitiators are well specified in p115 of Reinhold Schwalm's book'UV Coatings: Basics, Recent Developments and New Application (Elsevier 2007)', and are not limited to the above examples.
[52]
The photopolymerization initiator may be included in a concentration of 0.01 to 1.0% by weight, or 0.1 to 0.9% by weight, or 0.3 to 0.7% by weight based on the monomer composition. If the concentration of the photopolymerization initiator is too low, the polymerization rate may be slow, and if the concentration of the photopolymerization initiator is too high, the molecular weight of the superabsorbent polymer may be small and physical properties may become uneven.
[53]
In addition, as the thermal polymerization initiator, at least one selected from the group of initiators consisting of persulfate-based initiators, azo-based initiators, hydrogen peroxide and ascorbic acid may be used. Specifically, examples of persulfate-based initiators include sodium persulfate (Na 2 S 2 O 8 ), potassium persulfate (Potassium persulfate; K 2 S 2 O 8 ), and ammonium persulfate (Ammonium persulfate; (NH 4 )) 2 S 2 O 8), and examples of azo-based initiators 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- (carbamoyl azo) isobutyronitrile (2-(carbamoylazo) )isobutylonitril), 2, 2-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride (2,2-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride ), 4,4-azobis-(4-cyanovaleric acid) (4,4-azobis-(4-cyanovaleric acid)) and the like. More various thermal polymerization initiators are well specified in Odian's'Principle of Polymerization (Wiley, 1981)', p203, and are not limited to the above-described examples.
[54]
According to an embodiment of the present invention, the monomer composition includes an internal crosslinking agent as a raw material of the super absorbent polymer. This internal crosslinking agent is for crosslinking the interior of a polymer in which an acrylic acid-based monomer is polymerized, that is, a base resin, and is distinguished from a surface crosslinking agent for crosslinking the surface of the polymer.
[55]
The type of the internal crosslinking agent is not particularly limited, and any internal crosslinking agent may be used as it can be used in the manufacture of a super absorbent polymer. Specific examples of such an internal crosslinking agent include a poly(meth)acrylate-based compound of a polyol having 2 to 20 carbon atoms, a polyglycidyl ether-based compound of a polyol having 2 to 20 carbon atoms, or an allyl (meth)acrylate having 2 to 20 carbon atoms. System compounds, etc. are mentioned.
[56]
More specific examples of these internal crosslinking agents include trimethylolpropane tri(meth)acrylate, ethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, and polypropylene glycol di. (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, pentaerythritol tetraacrylate, ethylene glycol diglycylate Ethyleneglycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerol polyglycidyl ether, propylene glycol diglycidyl ether, or polypropylene glycol diglycidyl ether. In addition, various polyfunctional compounds Can be used as an internal crosslinking agent.
[57]
These internal crosslinking agents are included in a concentration of 0.01 to 1% by weight, or 0.05 to 0.8% by weight, or 0.2 to 0.7% by weight with respect to the monomer composition, to form a crosslinked structure inside the hydrogel polymer and the base resin powder formed therefrom. Can be introduced. If the content of the internal crosslinking agent is too small, the superabsorbent polymer
[58]
Meanwhile, in the manufacturing method of the above-described exemplary embodiment, the monomer composition may further include additives such as a thickener, a plasticizer, a storage stabilizer, and an antioxidant, if necessary.
[59]
Raw materials such as a monomer having an acidic group and at least a part of the acidic group neutralized, a photopolymerization initiator, a thermal polymerization initiator, an internal crosslinking agent, and an additive may be prepared in the form of a monomer composition solution dissolved in a solvent.
[60]
The solvent that can be used at this time can be used without limitation of its composition as long as it can dissolve the above-described 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 One or more selected from ethyl ether, toluene, xylene, butyrolactone, carbitol, methyl cellosolve acetate, and N,N-dimethylacetamide may be used in combination.
[61]
The solvent may be included in a residual amount excluding the above-described components with respect to the total content of the monomer composition.
[62]
On the other hand, as long as the method of forming a hydrogel polymer by thermal polymerization or photopolymerization of such a monomer composition is also a polymerization method commonly used, there is no particular limitation on the configuration.
[63]
Specifically, the polymerization method is largely divided into thermal polymerization and photopolymerization depending on the polymerization energy source, and when thermal polymerization is usually performed, it can be performed in a reactor having a stirring axis such as a kneader, and when photopolymerization is performed, it is possible to move. Although it may proceed in a reactor equipped with a conveyor belt, the polymerization method described above is an example, and the invention is not limited to the polymerization method described above.
[64]
As an example, the hydrogel polymer obtained by thermal polymerization by supplying hot air or heating the reactor to a reactor such as a kneader equipped with a stirring shaft as described above, according to the shape of the stirring shaft provided in the reactor, to the reactor outlet. The discharged hydrogel polymer may be in the form of several centimeters to several millimeters. Specifically, the size of the resulting hydrogel polymer may vary depending on the concentration and injection speed of the monomer composition to be injected, and a hydrogel polymer having a weight average particle diameter of 2 to 50 mm, or 3 to 30 mm can be obtained. .
[65]
In addition, when photopolymerization is carried out in a reactor equipped with a movable conveyor belt as described above, the form of the hydrogel polymer usually obtained may be a hydrogel polymer in a sheet form having the width of the belt. At this time, the thickness of the polymer sheet varies depending on the concentration and injection speed of the monomer composition to be injected, but it is preferable to supply the monomer composition so that a sheet-like polymer having a thickness of usually 0.5 to 5 cm, or 1 to 3 cm can be obtained. Do. In the case of supplying the monomer composition to the extent that the thickness of the polymer on the sheet is too thin, the production efficiency is not preferable, and when the thickness of the polymer on the sheet exceeds 5 cm, the polymerization reaction does not occur evenly over the entire thickness due to the excessive thickness I can't.
[66]
At this time, the water content of the hydrogel polymer obtained by this method may be 40 to 80% by weight, or 50 to 70% by weight. Meanwhile, in the entire specification, "water content" refers to a value obtained by subtracting the weight of the dried polymer from the weight of the hydrogel polymer as the content of moisture occupied by the total weight of the hydrogel polymer. Specifically, it is defined as a calculated value by measuring the weight loss due to evaporation of moisture in the polymer during drying by raising the temperature of the polymer through infrared heating. At this time, the drying condition is a method of increasing the temperature from room temperature to about 180°C and then maintaining it at 180°C. The total drying time is set to 20 minutes including 5 minutes in the temperature raising step, and the moisture content is measured.
[67]
Next, a step of drying the obtained hydrogel polymer is performed.
[68]
In this case, if necessary, a step of coarsely pulverizing before drying may be further performed in order to increase the efficiency of the drying step.
[69]
At this time, the grinder used is not limited in configuration, but specifically, a vertical pulverizer, a turbo cutter, a turbo grinder, a rotary cutter mill, and cutting Cutter mill, disc mill, shred crusher, crusher, chopper, and disc cutter. However, it is not limited to the above-described example.
[70]
At this time, the pulverization step may be pulverized so that the particle diameter of the hydrogel polymer is 2 to 10 mm, or 3 to 8 mm. The particle diameter of the hydrogel polymer may be defined as the longest distance among linear distances connecting arbitrary points on the surface of the hydrogel polymer.
[71]
Grinding with a particle diameter of less than 2 mm is not technically easy due to the high moisture content of the hydrogel polymer, and the pulverized particles may aggregate with each other. On the other hand, when the particle diameter is pulverized to exceed 10 mm, the effect of increasing the efficiency of the subsequent drying step is insignificant.
[72]
Drying is performed on the hydrogel polymer immediately after polymerization, which is pulverized as described above or has not undergone a pulverization step. In this case, the drying temperature in the drying step may be 150 to 250°C. When the drying temperature is less than 150°C, the drying time may be too long and the physical properties of the finally formed super absorbent polymer may be deteriorated. When the drying temperature exceeds 250°C, only the polymer surface is excessively dried, and a subsequent grinding process Fine powder may be generated in, and there is a concern that physical properties of the finally formed super absorbent polymer may be deteriorated. Therefore, preferably, the drying may be performed at a temperature of 150 to 200°C, more preferably 160 to 180°C.
[73]
Meanwhile, in the case of the drying time, the process may be performed for 20 to 90 minutes or 30 to 70 minutes in consideration of process efficiency, but is not limited thereto.
[74]
The drying method in the drying step may also be selected and used without limitation of its configuration as long as it is usually used as a drying process of the hydrogel polymer. Specifically, the drying step may be performed by a method such as hot air supply, infrared irradiation, microwave irradiation, or ultraviolet irradiation. The moisture content of the polymer after such a drying step may be 0.1 to 10% by weight, or 1 to 8% by weight. If the moisture content after drying is too low, the hydrogel polymer may deteriorate during the drying process and the physical properties of the super absorbent polymer may be deteriorated.On the contrary, if the moisture content is too high, the water absorption performance may decrease due to a large amount of moisture in the super absorbent polymer, or subsequent processing Can make progress difficult.
[75]
Next, a step of pulverizing the dried polymer obtained through such a drying step is performed.
[76]
The polymer powder obtained after the grinding step may have a particle diameter of 150 to 850 μm. The pulverizer used to pulverize to such a particle size is specifically, a pin mill, a hammer mill, a screw mill, a roll mill, a disc mill, or a jog. Mill (jog mill) or the like may be used, but the invention is not limited to the above-described examples.
[77]
In addition, in order to manage the physical properties of the super absorbent polymer powder that is finally commercialized after the pulverization step, a separate process of classifying the polymer powder obtained after pulverization according to the particle size may be performed, and a certain weight ratio of the polymer powder according to the particle size range. It can be classified so as to be.
[78]
Meanwhile, after the base resin is obtained in powder form through the above-described classification step, the base resin powder is heated in the presence of a surface crosslinking agent to perform surface crosslinking of the base resin powder.
[79]
In a general method for producing a super absorbent polymer, a dried, pulverized and classified polymer, i.e., a surface crosslinking solution containing a surface crosslinking agent is mixed with the base resin powder, and then the mixture is heated to raise the surface of the base resin powder. The crosslinking reaction is carried out.
[80]
The surface crosslinking step is a step of forming a super absorbent polymer having improved physical properties by inducing a crosslinking reaction on the surface of the pulverized polymer in the presence of a surface crosslinking agent. A surface crosslinking layer is formed on the surface of the pulverized and classified base resin powder through such surface crosslinking.
[81]
In general, since the surface crosslinking agent is applied to the surface of the base resin powder, the surface crosslinking reaction occurs on the surface of the base resin powder, which substantially does not affect the inside of the particles and improves the crosslinkability on the surface of the particles. Accordingly, the surface crosslinked superabsorbent polymer particles have a higher degree of crosslinking near the surface than at the inside by further crosslinking the crosslinked polymer on the surface of the base resin powder.
[82]
On the other hand, as the surface crosslinking agent, a compound capable of reacting with a functional group of the base resin is used, for example a polyalcohol compound, a polyepoxy compound, a polyamine compound, a haloepoxy compound, a condensation product of a haloepoxy compound, oxazoline compounds , Or an alkylene carbonate-based compound may be used without any particular limitation.
[83]
Specifically, examples of the polyhydric alcohol-based compound include di-, tri-, tetra- or polyethylene 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-hexanediol, and 1,2-cyclohexane One or more selected from the group consisting of dimethanol may be used.
[84]
In addition, ethylene glycol diglycidyl ether and glycidol may be used as polyvalent epoxy compounds, and as polyamine compounds, ethylenediamine, diethylenetriamine, triethylenetetraamine, tetraethylenepentamine, pentaethylenehexa One or more selected from the group consisting of min, polyethyleneimine, and polyamide polyamine may be used.
[85]
And as the haloepoxy compound, epichlorohydrin, epibromohydrin, and α-methylepichlorohydrin may be used. Meanwhile, as the mono-, di- or polyoxazolidinone compound, for example, 2-oxazolidinone may be used.
[86]
And, as the alkylene carbonate-based compound, ethylene carbonate or propylene carbonate may be used. These may be used alone or in combination with each other.
[87]
The amount of the added surface crosslinking agent may be appropriately selected depending on the type of the surface crosslinking agent added or reaction conditions, but usually 0.001 to 5 parts by weight, or 0.01 to 3 parts by weight, based on 100 parts by weight of the base resin powder, Alternatively, 0.05 to 2 parts by weight may be used.
[88]
If the content of the surface crosslinking agent is too small, the surface crosslinking reaction hardly occurs, and if it exceeds 5 parts by weight per 100 parts by weight of the polymer, basic absorption properties such as water holding capacity may be deteriorated due to excessive surface crosslinking reaction. have.
[89]
When the surface crosslinking agent is added, water may be mixed together and added in the form of a surface crosslinking solution. When water is added, there is an advantage that the surface crosslinking agent can be evenly dispersed in the polymer. At this time, the amount of water added is a ratio of 1 to 10 parts by weight per 100 parts by weight of the polymer for the purpose of inducing even dispersion of the surface crosslinking agent and preventing agglomeration of the polymer powder and optimizing the surface penetration depth of the surface crosslinking agent. It is preferably added as.
[90]
On the other hand, the above-described surface cross-linking step further uses one or more selected from the group consisting of a polyvalent metal salt, for example, an aluminum salt, more specifically aluminum sulfate, potassium salt, ammonium salt, sodium salt, and hydrochloride in addition to the surface cross-linking agent. You can proceed.
[91]
As these polyvalent metal salts are additionally used, the liquid permeability of the super absorbent polymer prepared by the method of one embodiment may be further improved. These polyvalent metal salts may be added to the surface crosslinking solution together with the surface crosslinking agent, and may be used in an amount of 0.01 to 4 parts by weight based on 100 parts by weight of the base resin powder.
[92]
Meanwhile, a surface modification step is performed on the base resin powder by heating the mixture of the base resin powder and the surface crosslinking solution to increase the temperature.
[93]
The surface crosslinking step may be performed under well-known conditions depending on the type of surface crosslinking agent, for example, it may be performed at a temperature of 100 to 200°C for 20 to 60 minutes. In a more specific example, the surface crosslinking step is performed by adding a surface crosslinking agent to the base resin powder having an initial temperature of 20°C to 80°C, and at a maximum temperature of 140°C to 200°C over 10 to 30 minutes. It can be carried out by raising the temperature and maintaining the maximum temperature for 5 to 60 minutes to heat treatment.
[94]
Depending on the surface crosslinking conditions, basic absorption characteristics such as water holding capacity of the super absorbent polymer, and liquid permeability and/or pressure absorption capacity may be optimized together.
[95]
The means for increasing the temperature for the surface crosslinking reaction is not particularly limited. It can be heated by supplying a heat medium or by directly supplying a heat source. At this time, as the type of the heat medium that can be used, a heated fluid such as steam, hot air, or hot oil may be used, but is not limited thereto, and the temperature of the supplied heat medium is the means of the heat medium, the heating rate, and the target temperature increase You can choose appropriately in consideration. Meanwhile, as a heat source directly supplied, heating through electricity and heating through gas may be mentioned, but the present invention is not limited to the above-described examples.
[96]
On the other hand, in the manufacturing method of one embodiment, during the step of forming the surface crosslinking layer or after the step of forming the surface crosslinking layer, further neutralizing the base resin powder by treating the base resin powder with a basic solution You can proceed. More specifically, in the additional neutralization step, after the surface crosslinking reaction is initiated by adding a surface crosslinking agent to the base resin powder and raising the temperature to 100°C or higher, or after the surface crosslinking reaction is completed, the base resin powder is Na + It can be further neutralized by treating with a basic solution containing ions.
[97]
In this way, as the further neutralization proceeds from the start of the surface crosslinking reaction to the completion of the surface crosslinking reaction, as well as the degree of neutralization/crosslinking inside the base resin powder, as well as the degree of neutralization of the surface crosslinking layer/ The degree of crosslinking is also controlled to a desirable level, so that the finally prepared superabsorbent polymer may exhibit improved properties in addition to basic water absorption capacity and absorption rate, as well as liquid permeability and absorption capacity under pressure.
[98]
In this additional neutralization process, as the basic solution, any basic solution that can be used in the process of neutralizing the monomer may be used, but more preferably , a basic aqueous solution containing Na + ions, more specifically, an aqueous sodium hydroxide solution, and sodium hydrogen carbonate An aqueous solution or an aqueous sodium carbonate solution can be used.
[99]
In addition, this basic solution contains 0.1 to 20 parts by weight, or 1 to 10 parts by weight based on 100 parts by weight of the base resin powder so that the neutralization degree of the surface crosslinked layer and the surface crosslinked super absorbent polymer can be controlled in an appropriate range. Can be used as
[100]
The super absorbent polymer finally prepared through such an additional neutralization step may have a neutralization degree of more than 70 mol%, or 70.5 to 80 mol%, or 70.5 to 75 mol%, measured for the water-soluble component of the super absorbent polymer. . As a result, the degree of neutralization and crosslinking of the surface crosslinked layer and the surface crosslinked superabsorbent polymer are optimized, so that the superabsorbent polymer maintains excellent absorption capacity and/or liquid permeability under pressure as well as basic absorption performance/absorption rate. Can show characteristics.
[101]
The super absorbent polymer prepared by the above-described method may include a base resin powder comprising a first crosslinked polymer of a water-soluble ethylenically unsaturated monomer having an acidic group at least partially neutralized; And a surface crosslinked layer formed on the base resin powder, wherein the first crosslinked polymer is further crosslinked through a surface crosslinking agent,
[102]
The neutralization degree measured for the water-soluble component of the super absorbent polymer is more than 70 mol%,
[103]
Centrifugation water retention capacity (CRC) for 30 minutes for physiological saline (0.9% by weight aqueous sodium chloride solution) is 28 g/g or more,
[104]
The flow induction property (SFC;·10 -7 cm 3 ·s/g) of physiological saline (0.685 wt% sodium chloride aqueous solution) may be 30 (·10 -7 cm 3 ·s/g) or more.
[105]
In a more specific example, the superabsorbent polymer has a water holding capacity (CRC) of 28 g/g or more, or 29 g/g or more, or 30 g/g or more, measured according to the EDANA method WSP 241.3, and 40 g/g/ g or less, or 36 g/g or less, or 34 g/g or less.
[106]
In addition, the superabsorbent polymer of one embodiment has a flow induction property (SFC, 10 -7 cm 3 ·s/g) of physiological saline (0.685 wt% sodium chloride aqueous solution) of 30 (·10 -7 cm 3 ·s/g) or more. , Or 50 (10 -7 cm 3 s/g) or more, 100 (10 -7 cm 3 s/g) or less, or 70 (10 -7 cm 3 s/g) or less Can be indicated.
[107]
The physiological saline flow induction (SFC) can be measured and calculated according to a method well known to those skilled in the art from before, for example, a method disclosed in columns 54 to 59 of U.S. Patent No. 5562646.
[108]
As described above, the super absorbent polymer prepared by the method of one embodiment can simultaneously exhibit excellent liquid permeability and water-retaining ability.
[109]
In addition, the superabsorbent polymer has a T-20 indicating the time required for 1 g of the resin to absorb 20 g of sodium chloride and 20 g of an alcohol ethoxylate aqueous solution having 12 to 14 carbon atoms, while being 170 seconds or less, or 165 seconds or less, or 161 seconds or less, and 100 It may exhibit a characteristic of more than a second, more than 110 seconds, or more than 130 seconds. This may reflect the high absorption rate of the super absorbent polymer.
[110]
In addition, the super absorbent polymer has a pressure absorption capacity (AUP) of 0.7psi measured according to the EDANA method WSP 242.3-10, 23 to 27 g/g, or 23.5 to 26.5 g/g, or 24 to 26 g/g. And the absorbency under pressure may reflect the excellent absorbency under pressure of the super absorbent polymer.
[111]
In addition, the super absorbent polymer may contain resin particles having a particle diameter of 150 to 850 μm in an amount of 90% by weight or more, or 90 to 98% by weight, and particles having a particle diameter of less than 150 μm may contain less than 2% by weight. , Or may be included in an amount of 0 to 1% by weight.
[112]
As described above, the superabsorbent polymer obtained according to the manufacturing method of one embodiment maintains excellent absorption performance and absorption rate, such as water holding capacity, and at the same time, satisfies excellent liquid permeability and absorption capacity under pressure. It can satisfy all physical properties. As a result, the super absorbent polymer may be suitably used as a sanitary material such as a diaper, and in particular, an ultra-thin sanitary material having a reduced pulp content.
Effects of the Invention
[113]
The superabsorbent polymer according to the present invention can exhibit a more improved absorption rate and liquid permeability while maintaining excellent basic absorption performance, and can be preferably applied to hygiene materials such as diapers having a thinner thickness.
Mode for carrying out the invention
[114]
Hereinafter, preferred embodiments are presented to aid in understanding the invention. However, the following examples are only for illustrating the present invention, and the present invention is not limited thereto.
[115]
[Comparative Example 1]: Preparation of super absorbent polymer
[116]
To prepare an aqueous monomer solution containing acrylic acid, caustic soda, and polyethylene glycol diacrylate (Mw=523; 0.55% by weight based on acrylic acid) as an internal crosslinking agent, and having a neutralization degree of 70 mol% and a monomer concentration of 45% by weight. I did.
[117]
Thereafter, to 1 kg of the aqueous monomer solution, 31.0 g of a 0.18% by weight ascorbic acid solution and 33 g of a 1% by weight sodium persulfate solution were mixed, and then mixed with 32 g of a 0.15% by weight hydrogen peroxide solution, followed by kneading while continuously polymerizing. Polymerization was carried out by introducing it through the supply part of a polymerization reactor capable of. At this time, the temperature of the polymerization reactor was maintained at 80°C, the maximum temperature for polymerization was 112°C, and the polymerization time was 58 seconds. After that, kneading was continued to perform polymerization and kneading for 20 minutes. At this time, the moisture content of the finally formed hydrogel polymer was 50.4% by weight.
[118]
Subsequently, the hydrogel polymer was dried for 30 minutes in a hot air dryer at a temperature of 190°C, and the dried hydrogel polymer was pulverized with a pin mill. Then, a polymer having a particle size of less than 150 µm and a polymer having a particle size of 150 µm to 850 µm were classified using a sieve.
[119]
Thereafter, a surface treatment solution containing 1.5 parts by weight of ethylene carbonate was sprayed to 100 parts by weight of the prepared base polymer to treat the surface of the super absorbent polymer. In addition, in the step of treating the surface, the classified base resin powder was supplied to one surface crosslinking reactor, and the surface crosslinking reaction was performed at a temperature of 190°C or higher for 35 minutes.
[120]
Thereafter, the surface-crosslinked super absorbent polymer was naturally cooled to 40° C. and then gradually dried, and a surface-treated super absorbent polymer having a particle diameter of 150 to 850 μm was obtained using a sieve. The fine powder content of less than 150 μm contained in the super absorbent polymer was less than 2% by weight.
[121]
[Example 1]: Preparation of super absorbent polymer
[122]
A base resin powder was prepared in the same manner as in Comparative Example 1, and the surface treatment process using ethylene carbonate was also carried out in the same manner as in Comparative Example 1.
[123]
After the surface treatment, the temperature of the super absorbent polymer was cooled to 90° C., and then 2.0 g of a 5% by weight caustic soda solution compared to 100 g of the super absorbent polymer was mixed to perform an additional neutralization process.
[124]
Thereafter, the additionally neutralized super absorbent polymer was dried in an oven at 40° C. for 30 minutes, and then a surface-treated super absorbent polymer having a particle diameter of 150 to 850 μm was obtained using a sieve. The fine powder content of less than 150 μm contained in the super absorbent polymer was less than 2% by weight.
[125]
[Example 2]: Preparation of super absorbent polymer
[126]
A base resin powder was prepared in the same manner as in Comparative Example 1, and the surface treatment process using ethylene carbonate was also carried out in the same manner as in Comparative Example 1.
[127]
After the surface treatment, the temperature of the super absorbent polymer was cooled to 90° C., and then 10.0 g of a 5 wt% caustic soda solution relative to 100 g of the super absorbent polymer was mixed to perform an additional neutralization process.
[128]
Thereafter, the additionally neutralized super absorbent polymer was dried in an oven at 40° C. for 30 minutes, and then a surface-treated super absorbent polymer having a particle diameter of 150 to 850 μm was obtained using a sieve. The fine powder content of less than 150 μm contained in the super absorbent polymer was less than 2% by weight.
[129]
[Example 3]: Preparation of super absorbent polymer
[130]
A base resin powder was prepared in the same manner as in Comparative Example 1, and the surface treatment process using ethylene carbonate was also carried out in the same manner as in Comparative Example 1.
[131]
After the surface treatment, the temperature of the super absorbent polymer was cooled to 90° C., and then 20.0 g of a 5% by weight caustic soda solution compared to 100 g of the super absorbent polymer was mixed to perform an additional neutralization process.
[132]
Thereafter, the additionally neutralized super absorbent polymer was dried in an oven at 40° C. for 30 minutes, and then a surface-treated super absorbent polymer having a particle diameter of 150 to 850 μm was obtained using a sieve. The fine powder content of less than 150 μm contained in the super absorbent polymer was less than 2% by weight.
[133]
[Example 4]: Preparation of super absorbent polymer
[134]
A base resin powder was prepared in the same manner as in Comparative Example 1, and the surface treatment process using ethylene carbonate was also carried out in the same manner as in Comparative Example 1.
[135]
After the surface treatment, the temperature of the super absorbent polymer was cooled to 90° C., and then 2.0 g of a 7.2 wt% sodium carbonate solution relative to 100 g of the super absorbent polymer was mixed to perform an additional neutralization process.
[136]
Thereafter, the additionally neutralized super absorbent polymer was dried in an oven at 40° C. for 30 minutes, and then a surface-treated super absorbent polymer having a particle diameter of 150 to 850 μm was obtained using a sieve. The fine powder content of less than 150 μm contained in the super absorbent polymer was less than 2% by weight.
[137]
[Example 5]: Preparation of super absorbent polymer
[138]
A base resin powder was prepared in the same manner as in Comparative Example 1, and the surface treatment process using ethylene carbonate was also carried out in the same manner as in Comparative Example 1.
[139]
After the surface treatment, the temperature of the super absorbent polymer was cooled to 90° C., and then 4.0 g of a 7.2 wt% sodium carbonate solution relative to 100 g of the super absorbent polymer was mixed to perform an additional neutralization process.
[140]
Thereafter, the additionally neutralized super absorbent polymer was dried in an oven at 40° C. for 30 minutes, and then a surface-treated super absorbent polymer having a particle diameter of 150 to 850 μm was obtained using a sieve. The fine powder content of less than 150 μm contained in the super absorbent polymer was less than 2% by weight.
[141]
[Example 6]: Preparation of super absorbent polymer
[142]
Acrylic acid, caustic soda, polyethylene glycol diacrylate (Mw = 523; 0.5% by weight based on acrylic acid) as an internal crosslinking agent, and 0.033 g of diphenyl (2,4,6-trimethylbenzoyl)-phosphine oxide as a UV initiator Then, an aqueous monomer solution having an acrylic acid neutralization of 72 mol% and a monomer concentration of 45% by weight was prepared.
[143]
Then, to 1 kg of the monomer aqueous solution, first, 0.17% by weight sodium hydrogencarbonate solution 3.0 is mixed, and the composition is introduced through the supply unit of a polymerization reactor consisting of a conveyor belt continuously moving, and ultraviolet rays are irradiated through a UV irradiation device ( Irradiation amount: 2mW/cm2) and UV polymerization was performed for 2 minutes to prepare a hydrogel polymer. After the hydrogel polymer was transferred to a cutter, it was cut to a maximum length of 0.2 cm. At this time, the water content of the cut hydrogel polymer was 50% by weight.
[144]
Subsequently, the hydrogel polymer was dried for 30 minutes in a hot air dryer at a temperature of 190°C, and the dried hydrogel polymer was pulverized with a pin mill. Then, a polymer having a particle size of less than 150 µm and a polymer having a particle size of 150 µm to 850 µm were classified using a sieve.
[145]
Thereafter, a surface treatment solution containing 1.5 parts by weight of ethylene carbonate was sprayed to 100 parts by weight of the prepared base polymer to treat the surface of the super absorbent polymer. In addition, in the step of treating the surface, the classified base resin powder was supplied to one surface crosslinking reactor, and the surface crosslinking reaction was performed at a temperature of 190°C or higher for 35 minutes.
[146]
Thereafter, after the surface treatment, the temperature of the super absorbent polymer was cooled to 90° C., and then 2.0 g of a 10 wt% caustic soda solution was mixed with 100 g of the super absorbent polymer to perform an additional neutralization process.
[147]
Thereafter, the additionally neutralized super absorbent polymer was dried in an oven at 40° C. for 30 minutes, and then a surface-treated super absorbent polymer having a particle diameter of 150 to 850 μm was obtained using a sieve. The fine powder content of less than 150 μm contained in the super absorbent polymer was less than 2% by weight.
[148]
[Example 7]: Preparation of super absorbent polymer
[149]
A base resin powder was prepared in the same manner as in Example 6, and the surface treatment process using ethylene carbonate was also carried out in the same manner as in Example 6.
[150]
After the surface treatment, the temperature of the super absorbent polymer was cooled to 90° C., and then 10.0 g of a 10 wt% caustic soda solution relative to 100 g of the super absorbent polymer was mixed to perform an additional neutralization process.
[151]
Thereafter, the additionally neutralized super absorbent polymer was dried in an oven at 80° C. for 30 minutes, and then a surface-treated super absorbent polymer having a particle diameter of 150 to 850 μm was obtained using a sieve. The fine powder content of less than 150 μm contained in the super absorbent polymer was less than 2% by weight.
[152]
[Example 8]: Preparation of super absorbent polymer
[153]
A base resin powder was prepared in the same manner as in Example 6, and the surface treatment process using ethylene carbonate was also carried out in the same manner as in Example 6.
[154]
After the surface treatment, the temperature of the super absorbent polymer was cooled to 90° C., and then 2.0 g of a 7.2 wt% sodium carbonate solution relative to 100 g of the super absorbent polymer was mixed to perform an additional neutralization process.
[155]
Thereafter, the additionally neutralized super absorbent polymer was dried in an oven at 40° C. for 30 minutes, and then a surface-treated super absorbent polymer having a particle diameter of 150 to 850 μm was obtained using a sieve. The fine powder content of less than 150 μm contained in the super absorbent polymer was less than 2% by weight.
[156]
[Example 9]: Preparation of super absorbent polymer
[157]
A base resin powder was prepared in the same manner as in Example 6, and the surface treatment process using ethylene carbonate was also carried out in the same manner as in Example 6.
[158]
After the surface treatment, the temperature of the super absorbent polymer was cooled to 90° C., and then 2.0 g of a 15.0 wt% sodium carbonate solution relative to 100 g of the super absorbent polymer was mixed to perform an additional neutralization process.
[159]
Thereafter, the additionally neutralized super absorbent polymer was dried in an oven at 40° C. for 30 minutes, and then a surface-treated super absorbent polymer having a particle diameter of 150 to 850 μm was obtained using a sieve. The fine powder content of less than 150 μm contained in the super absorbent polymer was less than 2% by weight.
[160]
Experimental example
[161]
The physical properties of each super absorbent polymer prepared in Examples and Comparative Examples, and all physical properties during the manufacturing process were measured and evaluated by the following methods.
[162]
(1) Grain size evaluation
[163]
The particle diameters of the base resin powder and superabsorbent polymer used in Examples and Comparative Examples were measured according to the European Disposables and Nonwovens Association (EDANA) standard EDANA WSP 220.3 method.
[164]
(2) Centrifuge Retention Capacity (CRC)
[165]
In accordance with the European Disposables and Nonwovens Association (EDANA) standard EDANA WSP 241.3, the centrifugal separation capacity (CRC) was measured by the absorption rate under no load. The super absorbent polymer W 0 (g, about 0.2 g) was uniformly placed in a nonwoven bag and sealed, and then immersed in physiological saline solution of 0.9 wt% sodium chloride aqueous solution at room temperature. After 30 minutes, the bag was centrifuged and dried at 250 G for 3 minutes, and the mass W 2 (g) of the bag was measured. Further, the mass W 1 (g) at that time was measured after performing the same operation without using a super absorbent polymer . Using each of the masses thus obtained, CRC (g/g) was calculated according to the following formula 1 to confirm the water holding capacity.
[166]
[Calculation 1]
[167]

[168]
(3) Absorbing under Pressure (AUP)
[169]
For the superabsorbent polymers of Examples and Comparative Examples, Absorbency under Pressure (AUP) was measured according to the method of EDANA WSP 242.3-10 of the European Disposables and Nonwovens Association.
[170]
First, a stainless steel 400 mesh wire mesh was mounted on the bottom of a plastic cylinder having an inner diameter of 60 mm. The resin W 0 (g, 0.90 g) obtained in Examples and Comparative Examples was evenly sprayed on a wire mesh under a temperature of 23±2℃ and a relative humidity of 45%, and a load of 4.83 kPa (0.7 psi) was uniformly applied thereto. The piston, which can be further imparted, has an outer diameter of a little less than 60 mm, and there is no gap with the inner wall of the cylinder, and the vertical movement is not disturbed. At this time, the weight W 3 (g) of the device was measured.
[171]
A glass filter having a diameter of 125 mm and a thickness of 5 mm was placed on the inside of a 150 mm diameter PET dish, and a physiological saline solution composed of 0.90 wt% sodium chloride was at the same level as the upper surface of the glass filter. The measuring device was mounted on a glass filter, and the liquid was absorbed for 1 hour under load. After 1 hour, the measuring device was lifted and the weight W 4 (g) was measured.
[172]
Using each of the masses thus obtained, AUP (g/g) was calculated according to the following calculation formula 2, and the absorbency under pressure was confirmed.
[173]
[Calculation 2]
[174]

[175]
In Equation 2 above,
[176]
W 0 (g) is the initial weight (g) of the super absorbent polymer,
[177]
W 3 (g) is the sum of the weight of the super absorbent polymer and the weight of the device capable of applying a load to the super absorbent polymer,
[178]
W 4 (g) is the sum of the weight of the super absorbent polymer and the weight of the device capable of imparting a load to the super absorbent polymer after absorbing physiological saline in the super absorbent polymer for 1 hour under load (0.7 psi).
[179]
(3) saline flow conductivity (SFC)
[180]
Measurements and calculations were made according to the method disclosed in column 54 to column 59 of US Patent Registration No. 5622646. It was different from the US patent that only 1.5 g of the super absorbent polymer used in the measurement was used instead of 0.9 g.
[181]
(4) The degree of neutralization of the final super absorbent polymer
[182]
In the Examples and Comparative Examples, for the super absorbent polymer finally manufactured through a surface treatment process or an additional neutralization process, a water-soluble component (in accordance with the method of the European Disposables and Nonwovens Association) standard EDANA WSP 270.3-10 ( Extractables Content) was extracted and its content was measured.
[183]
The final neutralization degree was calculated for these water-soluble components by the following method.
[184]
1) carboxylator nCOOH (moles),
[185]
nCOOH =(V NaOH ,s-V NaOH, b) c NaOH
[186]
Here, V NaOH ,s is the amount of NaOH (ml) required to titrate the filtered sample solution to pH 10.0, V NaOH, b is the amount of NaOH required to titrate the blank solution without superabsorbent polymer to pH 10.0. Each represents the amount of NaOH (ml), and c NaOH represents the concentration (mol/liter) of NaOH used for titration.
[187]
2) ntot =(V HCl ,s-V HCl, b) c HCl
[188]
Here, V HCl ,s is the amount of HCl required to titrate the filtered sample solution from pH 10.0 to pH 4.0 (ml), V HCl, b is the blank solution without super absorbent polymer at pH 10.0. , represents the amount of HCl (ml) required for titration up to pH 4.0, and c HCl represents the concentration (mol/liter) of HCl used for titration.
[189]
3) It can be calculated by nCOONa = ntot-nCOOH, and the final neutralization degree (mol%) = nCOONa/ ntot * 100 can be finally calculated.
[190]
(5) T-20
[191]
An aqueous solution was prepared by dissolving 9 g of sodium chloride and 0.1 g of Lorodac (main component: alcohol ethoxylate having 12 to 14 carbon atoms, CAS# 68439-50-9) in 1 L of distilled water, and under pressure of 0.3 psi, a super absorbent polymer It was calculated and measured as the time required for 1 g to absorb 20 g of this aqueous solution. The specific measuring method of the T-20 is described in detail on pages 13 to 18 of European Patent Publication No. 2535027.
[192]
The above physical property evaluation results are summarized and shown in Table 1 below.
[193]
[Table 1]
[194]

[195]
Referring to Table 1 above, it was confirmed that the superabsorbent polymer of the Example had a basic absorption performance equal to or higher than that of the Comparative Example, and exhibited superior liquid permeability and absorption rate compared to the Comparative Example.
Claims
[Claim 1]
Crosslinking and polymerizing a monomer composition comprising a water-soluble ethylenically unsaturated monomer having at least a partially neutralized acidic group and an internal crosslinking agent to form a hydrogel polymer; Drying, pulverizing and classifying the hydrogel polymer to form a base resin powder; And forming a surface crosslinking layer by further crosslinking the surface of the base resin powder in the presence of a surface crosslinking agent, wherein in the forming of the hydrogel polymer, the water-soluble ethylenically unsaturated monomer has a degree of neutralization of less than 70 mol%. And, during the step of forming the surface crosslinking layer or after the step of forming the surface crosslinking layer, the base resin powder is treated with a basic solution to further neutralize the base resin powder. Way.
[Claim 2]
The method of claim 1, wherein in the additional neutralization step, a surface crosslinking agent is added to the base resin powder, and after the surface crosslinking reaction is initiated by heating to a temperature of 100°C or higher, the base resin powder is treated with a basic solution containing Na + ions. Method for producing a super absorbent polymer comprising the step of further neutralizing.
[Claim 3]
The method of claim 2, wherein the basic solution is an aqueous sodium hydroxide solution, an aqueous sodium hydrogen carbonate solution, or an aqueous sodium carbonate solution.
[Claim 4]
The method of claim 2, wherein the basic solution is used in an amount of 0.1 to 20 parts by weight based on 100 parts by weight of the base resin powder.
[Claim 5]
The method of claim 1, wherein after the additional neutralization step, the degree of neutralization measured for the water-soluble component of the super absorbent polymer is greater than 70 mol%.
[Claim 6]
The method of claim 1, wherein the surface crosslinking agent is selected from the group consisting of polyhydric alcohol compounds, polyvalent epoxy compounds, polyamine compounds, haloepoxy compounds, condensation products of haloepoxy compounds, oxazoline compounds, and alkylene carbonate compounds. A method for producing a super absorbent polymer containing more than one species.
[Claim 7]
The method of claim 1, wherein the surface crosslinking step is heated from an initial temperature of 20°C to 80°C over 10 to 30 minutes to a maximum temperature of 140°C to 200°C, and the maximum temperature is maintained for 5 to 60 minutes. The method for producing a super absorbent polymer proceeds by performing heat treatment.
[Claim 8]
A base resin powder containing a first crosslinked polymer of a water-soluble ethylenically unsaturated monomer having an acidic group at least partially neutralized; And a surface crosslinked layer formed on the base resin powder, wherein the first crosslinked polymer is further crosslinked via a surface crosslinking agent, wherein the degree of neutralization measured for the water-soluble component of the super absorbent polymer Is more than 70 mol%, the centrifugation water holding capacity (CRC) for 30 minutes for physiological saline (0.9 wt% sodium chloride aqueous solution) is 28 g/g or more, and the flow of physiological saline solution (0.685 wt% sodium chloride aqueous solution) Super absorbent polymer having an inductive property (SFC;·10 -7 cm 3 ·s/g) of 30 (·10 -7 cm 3 ·s/g) or more.
[Claim 9]
The super absorbent polymer according to claim 8, wherein 1 g of the super absorbent polymer has a T-20 representing a time required for absorbing 20 g of an aqueous solution of sodium chloride and an alcohol ethoxylate having 12 to 14 carbon atoms for less than 170 seconds.
[Claim 10]
The method of claim 8, wherein the super absorbent polymer contains resin particles having a particle diameter of 150 to 850 μm in an amount of 90% by weight or more, and has a pressure absorption capacity (AUP) of 0.7 psi measured according to the EDANA method WSP 242.3-10. 23 to 27 g/g super absorbent polymer.