WO2015088242A1 - Super-absorbent resin and method for preparing same - Google Patents

Abstract

The present invention relates to a method for preparing a super-absorbent resin and a super-absorbent resin prepared by the method, wherein the super-absorbent resin comprises a reassembly reassembled using particles having a particle size of 450 ㎛ or smaller. The present invention has an advantage of improving both the absorption rate and the water permeability, when compared with existing super-absorbent resins.

Description

Super Absorbent Resin and Manufacturing Method Thereof

The present invention relates to a super absorbent polymer and a method for manufacturing the same, and more particularly, to a super absorbent polymer having improved absorption rate and water permeability and a method for producing the same.

Super Absorbent Polymer (SAP) is a synthetic polymer material capable of absorbing water of 500 to 1,000 times its own weight.It has been put into practical use as a sanitary device and is now a paper diaper for children. In addition to sanitary products, it is widely used as a material for horticultural soil repair, civil engineering, building index material, seedling sheet, freshness retainer in food distribution, and for steaming.

The absorption mechanism of the superabsorbent polymer has the interaction between the penetration pressure due to the difference in electrical attraction force of the charge of the polymer electrolyte, the affinity between water and the polymer electrolyte, the expansion of the molecule due to the repulsive force between the polymer electrolyte ions, and the expansion inhibition due to crosslinking. Is ruled by That is, the absorbency of the absorbent polymer depends on the affinity and molecular expansion described above, and the rate of absorption is largely dependent on the penetration pressure of the absorbent polymer itself.

In order to improve the absorption rate of such superabsorbent polymers, many studies are being conducted. For example, Korean Patent Publication No. 2007-0012623 A discloses limiting the content ratio according to the size of resin particles. And there was a problem that it is not enough to improve the permeability at the same time.

The present invention is to solve the problems of the prior art as described above,

Absorption rate and permeability by increasing the amount of fine powder reassembly to the existing particles by more than 15% and reducing the content of particles of 600 ~ 850㎛ and 150 ~ 300㎛ and increasing the content of particles of 300 ~ 600㎛ It is an object of the present invention to provide a super absorbent polymer which can improve the properties of the polymer.

The present invention to achieve the above object,

a) preparing a hydrogel polymer by thermally polymerizing or photopolymerizing a monomer composition comprising a water-soluble ethylenically unsaturated monomer and a polymerization initiator; b) drying the hydrogel polymer; c) milling the dried polymer; d) the pulverized hydrogel polymer having a particle size of less than 150 μm, a particle size of 150 μm or more and less than 300 μm, a particle size of 300 μm or more and less than 450 μm, a particle size of 450 μm or more and 600 μm or less, and a particle size of 600 μm or more and 850 μm or less Classifying into particles; e) The particles having a size of 450 μm or less are used in the pulverized hydrogel polymer, which is a particle having a particle size of 600 μm or more and 850 μm or less, a particle size of 300 μm or more and 600 μm or less, and a particle having a particle size of 150 μm or more and less than 300 μm mixed. Mixing the reassembled reassembled; f) adding a surface crosslinking agent to each of said mixed hydrogel polymers; And g) performing a surface crosslinking reaction of the hydrogel polymer, wherein the hydrogel polymer of step e) is based on the total weight of the normal particles and the reassembly, and has a particle size of 600 to 850 μm. 15 to 30% by weight of particles of 300 to 600 µm in particle size, 1 to 25% by weight of particles in particle size of 150 to 300 µm and 15 to 30 µm of particle size of 450 µm or less It provides a method for producing a super absorbent polymer comprising 30% by weight.

The present invention also relates to a superabsorbent polymer comprising a pulverized hydrogel polymer in which a water-soluble ethylenically unsaturated monomer is polymerized, wherein the pulverized hydrogel polymer has a particle size of 600 µm or more and 850 µm or less, and a particle size of 300 µm or more and 600 µm or less. Normal particles mixed with particles and particles having a particle size of 150 µm or more and less than 300 µm and a reassembled reassembled particle having a particle size of 450 µm or less are surface crosslinked, and based on the total total weight of the normal particles and the reassembly, 0.01 ~ 3% by weight of particles of 600 ~ 850㎛ size, 50 ~ 80% by weight of particles of 300 ~ 600㎛ particle size, 1 ~ 25% by weight of particles of 150 ~ 300㎛ particle size and particles of particle size of 450㎛ or less It provides a super absorbent polymer comprising 15 to 30% by weight of the reassembled by reassembling.

According to the super absorbent polymer according to the present invention, there is an advantage in that the absorption rate and the water permeability characteristics can be improved together as compared with the super absorbent polymers used in the prior art.

1 is a graph showing the water permeability characteristics of the super absorbent polymer prepared in Examples and Comparative Examples according to the present invention.

Figure 2 is a graph showing the absorption rate characteristics of the super absorbent polymer prepared in Examples and Comparative Examples according to the present invention.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

Method for producing a super absorbent polymer according to the present invention comprises the steps of: a) preparing a hydrogel polymer by thermal polymerization or photopolymerization of a monomer composition comprising a water-soluble ethylenically unsaturated monomer and a polymerization initiator; b) drying the hydrogel polymer; c) milling the dried polymer; d) the pulverized hydrogel polymer having a particle size of less than 150 μm, a particle size of 150 μm or more and less than 300 μm, a particle size of 300 μm or more and less than 450 μm, a particle size of 450 μm or more and 600 μm or less, and a particle size of 600 μm or more and 850 μm or less Classifying into particles; e) The particles having a size of 450 μm or less are used in the pulverized hydrogel polymer, which is a particle having a particle size of 600 μm or more and 850 μm or less, a particle size of 300 μm or more and 600 μm or less, and a particle having a particle size of 150 μm or more and less than 300 μm mixed. Mixing the reassembled reassembled; f) adding a surface crosslinking agent to each of said mixed hydrogel polymers; And g) performing a surface crosslinking reaction of the hydrogel polymer, wherein the hydrogel polymer of step e) is based on the total weight of the normal particles and the reassembly, and has a particle size of 600 to 850 μm. 15 to 30% by weight of particles of 300 to 600 µm in particle size, 1 to 25% by weight of particles in particle size of 150 to 300 µm and 15 to 30 µm of particle size of 450 µm or less Characterized in that it comprises 30% by weight.

First, the method for preparing a super absorbent polymer according to the present invention is a) undergoing a step of preparing a hydrogel polymer by thermal polymerization or photopolymerization of a monomer composition comprising a water-soluble ethylenically unsaturated monomer and a polymerization initiator.

For preparing the super absorbent polymer of the present invention, the polymer may be prepared by the steps and methods commonly used in the art. Specifically, in the preparation of the super absorbent polymer of the present invention, the monomer composition includes a polymerization initiator, the photopolymerization initiator is included in the photopolymerization method according to the polymerization method, and the thermal polymerization is performed in the thermal polymerization method. Initiator and the like. However, even with the photopolymerization method, since a certain amount of heat is generated by irradiation such as ultraviolet irradiation, and a certain amount of heat is generated in accordance with the progress of the polymerization reaction, which is an exothermic reaction, a thermal polymerization initiator may be additionally included.

The thermal polymerization initiator used in the method for preparing the superabsorbent polymer according to the present invention is not particularly limited, and preferably at least one selected from the group consisting of an initiator group consisting of persulfate-based initiator, azo-based initiator, hydrogen peroxide, and ascorbic acid. Can be used. Specifically, examples of persulfate-based initiators include sodium persulfate (Na2S2O8), potassium persulfate (K2S2O8), ammonium persulfate (NH4) 2S2O8, and the like. Examples of 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-azo Bis [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)) etc. can be used.

In addition, the photopolymerization initiator used in the method for preparing the superabsorbent polymer according to the present invention is not particularly limited, but is preferably benzoin ether, dialkyl acetophenone, or hydroxyl alkyl ketone. At least one selected from the group consisting of alkylketone, phenyl glyoxylate, benzyl dimethyl ketal, acyl phosphine and alpha-aminoketone can be used. . Meanwhile, as an example of acylphosphine, a commercially available lucirin TPO, that is, 2,4,6-trimethyl-benzoyl-trimethyl phosphine oxide can be used. .

In addition, in the manufacturing method of the superabsorbent polymer according to the present invention, the water-soluble ethylenically unsaturated monomer is not particularly limited as long as it is a monomer normally used in the preparation of the superabsorbent polymer, but preferably an anionic monomer and salts thereof, Any one or more selected from the group consisting of ionic hydrophilic-containing monomers, amino group-containing unsaturated monomers and quaternized compounds thereof can be used. Specifically, acrylic acid, methacrylic acid, maleic anhydride, fumaric acid, crotonic acid, itaconic acid, 2-acryloylethanesulfonic acid, 2-methacryloylethanesulfonic acid, 2- (meth) acryloylpropanesulfonic acid, or 2 Anionic monomers of-(meth) acrylamide-2-methylpropane sulfonic acid and salts thereof; (Meth) acrylamide, N-substituted (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, methoxy polyethylene glycol (meth) acrylate or polyethylene glycol ( Nonionic hydrophilic-containing monomers of meth) acrylate; And an amino group-containing unsaturated monomer of (N, N) -dimethylaminoethyl (meth) acrylate or (N, N) -dimethylaminopropyl (meth) acrylamide and a quaternized product thereof. It can be used easily, and more preferably acrylic acid or salts thereof may be used. In the case of using acrylic acid or salts thereof as a monomer, there is an advantage in that a super absorbent polymer having improved water absorption can be obtained.

In the method for preparing a super absorbent polymer according to the present invention, the monomer composition may include a predetermined amount of fine powder, that is, a polymer or resin powder having a particle size of less than 150 μm, in the prepared superabsorbent polymer powder for the effect of resource recycling. In detail, specifically, the polymer or resin powder having the particle size of less than 150 μm may be added at the initial, middle, and end stages before the start of the polymerization reaction of the monomer composition or after the start of the polymerization reaction. In this case, the amount that can be added is not limited, but it is preferable to add 1 to 10 parts by weight based on 100 parts by weight of the monomer included in the monomer resin composition in order to prevent the deterioration of physical properties of the superabsorbent polymer.

On the other hand, in the method for producing a super absorbent polymer according to the present invention, the concentration of the water-soluble ethylenically unsaturated monomer in the monomer composition may be appropriately selected in consideration of the polymerization time and reaction conditions, but preferably 40 to 55% by weight. You can do When the concentration of the water-soluble ethylenically unsaturated monomer is less than 40% by weight, it is disadvantageous in terms of economy, and when it exceeds 55% by weight, the grinding efficiency may be low when the polymerized hydrous gel polymer is pulverized.

The method of preparing a hydrogel polymer by thermally polymerizing or photopolymerizing such a monomer composition is not limited as long as it is a polymerization method that is commonly used. Specifically, the polymerization method is largely divided into thermal polymerization and photopolymerization according to the polymerization energy source, when the thermal polymerization is usually carried out, it can be carried out in a reactor having a stirring shaft, such as kneader, and when the polymerization proceeds, Although it can proceed in a reactor with a conveyor belt possible, the above-described polymerization method is an example, the present invention is not limited to the above-described polymerization method.

For example, the hydrogel polymer obtained by supplying hot air to a reactor such as a kneader having a stirring shaft as described above or by heating the reactor to be thermally polymerized has a reactor outlet according to the shape of the stirring shaft provided in the reactor. The hydrogel polymer discharged into may be in the form of several centimeters to several millimeters. Specifically, the size of the hydrous gel polymer obtained may vary depending on the concentration and the injection speed of the monomer composition to be injected, the hydrogel polymer having a particle size of 2 to 50 mm can be obtained.

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

The light source that can be used in the photopolymerization step is not particularly limited, and an ultraviolet light source known to cause a photopolymerization reaction may be used without particular limitation. For example, light having a wavelength of about 200 to 400 nm may be used, and an ultraviolet light source such as an Xe lamp, a mercury lamp, or a metal halide lamp may be used. The photopolymerization step may be performed for about 5 seconds to about 10 minutes at an intensity of about 0.1 mw / cm 2 to about 1 kw / cm 2. When the intensity and time of the light applied to the photopolymerization reaction is too small or short, the polymerization reaction may not occur sufficiently, and when too large or long, the quality of the superabsorbent polymer may be degraded.

Thereafter, the method for preparing a super absorbent polymer according to the present invention is subject to b) drying the hydrogel polymer.

Normal water content of the hydrogel polymer obtained in step a) is 30 to 60% by weight. On the other hand, throughout the present specification, "water content" means the weight of the water-containing gel polymer subtracted from the weight of the dry polymer by the amount of water occupied with respect to the total weight of the water-containing gel polymer (specifically, through infrared heating It is defined as a value calculated by measuring the weight loss according to the evaporation of water in the polymer during drying by raising the temperature of the polymer, wherein the drying conditions are raised by raising the temperature from room temperature to 180 ° C. and maintaining the temperature at 180 ° C. The drying time is set to 20 minutes, including 5 minutes of temperature rise, and the moisture content is measured.)

The hydrogel polymer obtained in step a) is subjected to a drying step. Preferably, the drying temperature of the drying step may be 150 ° C to 250 ° C. On the other hand, the "drying temperature" throughout this specification may be defined as the temperature of the heating reactor including the heat medium and the polymer in the temperature of the heat medium supplied for drying or the drying process.

If the drying temperature is less than 150 ° C., the drying time may be too long, and the physical properties of the final superabsorbent polymer may be lowered. If the drying temperature exceeds 250 ° C., only the surface of the polymer is dried too much, and a subsequent grinding step is performed. Fine powder may occur, and there is a fear that the physical properties of the superabsorbent polymer to be finally formed decrease. Preferably the drying may be carried out at a temperature of 150 ℃ to 250 ℃, more preferably at a temperature of 160 ℃ to 200 ℃.

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

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

On the other hand, the method for producing a super absorbent polymer according to the present invention may be further subjected to a simple grinding step before the drying step, if necessary, in order to increase the efficiency of the drying step. The simple grinding step before the drying step may be such that the particle size of the polymer of the hydrous gel polymer is 1 mm to 15 mm, and it is technically difficult to grind the particle size of the polymer to less than 1 mm due to the high water content of the hydrogel polymer. In addition, the phenomenon of agglomeration between the pulverized particles may appear, and when pulverizing so that the particle size exceeds 15 mm, the effect of increasing the efficiency of the subsequent drying step due to pulverization becomes insignificant.

In the simple grinding step before the drying step, the pulverizer used is not limited in configuration, but specifically, a vertical pulverizer, a turbo cutter, a turbo grinder, and a rotary machine are used. It consists of rotary cutter mill, cutter mill, disc mill, shred crusher, crusher, chopper and disc cutter It may include any one selected from the group of grinding devices, but is not limited to the above examples.

As such, when the grinding step is performed in order to increase the drying efficiency before the drying step, the polymer may be stuck to the surface of the grinder due to the high moisture content polymer. Therefore, in order to increase the efficiency of the pulverization step before drying of the hydrous gel polymer, additives that can prevent sticking during pulverization may be further used. Specific types of additives that can be used are not particularly limited, but may include fine powder aggregation inhibitors such as steam, water, surfactants, inorganic powders such as Clay and Silica; Thermal polymerization initiators such as persulfate initiators, azo initiators, hydrogen peroxide, and ascorbic acid, epoxy crosslinkers, diol crosslinkers, crosslinking agents including acrylates of difunctional or trifunctional or polyfunctional groups or more, and hydroxyl groups. It may be a crosslinking agent such as a compound of a monofunctional group to be included, but is not limited to the examples described above.

Thereafter, the manufacturing method of the super absorbent polymer according to the present invention is subjected to the drying step, and then c) grinding the dried polymer. The particle size of the polymer obtained after the grinding step is 150 to 850㎛. In the manufacturing method of the superabsorbent polymer according to the present invention, the pulverizer used to grind to such a particle size is specifically a pin mill, a hammer mill, a screw mill, a roll mill (roll mill), disk mill (disc mill) or jog mill (jog mill) and the like can be used, but is not limited thereto.

Subsequently, the method for preparing a super absorbent polymer according to the present invention includes d) the pulverized hydrogel polymer having a particle size of less than 150 μm, a particle size of 150 μm or more and less than 300 μm, a particle size of 300 μm or more and less than 450 μm, and a particle size of 450 μm. The fine particles are classified into particles of not less than 600 µm and particles of not less than 600 µm and not more than 850 µm. In this case, the particle size that is a classification standard may be based on a specific surface area ratio per weight of the polymer particles. The larger the value of the classification step, the more uniform the distribution of the surface crosslinking agent added to the polymer particles upon addition of the surface crosslinking agent. Therefore, the method for producing a superabsorbent polymer according to the present invention includes particles of less than 150 μm, particles of particle size of 150 μm or more and less than 300 μm, particle size of 300 μm or more and 450 μm in view of securing uniformity of the surface crosslinking agent to be added and economic efficiency of the process. The particles are classified into particles having a particle size of less than 450 μm or more and 600 μm or less and particles having a particle size of 600 μm or more and 850 μm or less.

Looking specifically at the manufacturing process of the classification step, the hydrogel polymer supplied from the polymer feeder is ground in a polymer mill to a particle size of 150 to 850㎛, and then classified through a classifier according to each particle size. At this time, the fine powder having a particle size of less than 150 µm is not classified separately, and the particles having a particle size of more than 850 µm can be separately classified and sent back to the grinder.

Subsequently, the method for preparing a super absorbent polymer according to the present invention includes e) particles having a particle size of 600 μm or more and 850 μm or less, particles having a particle size of 300 μm or more and 600 μm or less, and particles having a particle size of 150 μm or more and less than 300 μm. The reassembled reassembled mixture is mixed with the mixed normal particles using particles having a size of 450 μm or less. In the step f), the normal particles are water-containing gel polymer particles are mixed with particles of 600 ~ 850㎛ size, particles of 300 ~ 600㎛ size and particles of 150 ~ 300㎛ size, the reassembly It means reassembly using a particle size of 450 μm or less in the gel polymer. The reassembly may be prepared by putting 50 to 300 parts by weight of water per 100 parts by weight of particles of less than 450 μm into a mixer rotating at high speed for 30 seconds to 5 minutes.

The hydrogel polymer of step e) is preferably 0.01 to 3% by weight of the particle size 600 ~ 850㎛ size, particle size of 300 ~ 600㎛ size 50 ~ 80 based on the total weight of the normal particles and the reassembly It may include 15 to 30% by weight of the reassembled by weight%, 1-25% by weight of the particle size of 150 ~ 300㎛ and particles of the particle size of 450㎛ or less.

In addition, the hydrogel polymer of step e) is more preferably 0.1 to 2% by weight of the particle size 600 ~ 850㎛ size, particle size 300 ~ 600㎛ 55 based on the total weight of the normal particles and the reassembly It may include 15 to 30% by weight of the reassembly re-assembled using ~ 80% by weight, 3-25% by weight of the particle size of 150 ~ 300㎛ and particles of the particle size of 450㎛ or less.

In addition, the reassembly may be reassembled using particles having a particle size of 400 μm or less.

The present invention includes at least 15% of the reassembly as described above and at the same time reduce the content of particles having a particle size of 600 ~ 850㎛ size and particles of a particle size of 150 ~ 300㎛ size, including the particles of the particle size of 300 ~ 600㎛ By increasing the content, the absorption rate and permeability can be improved together.

The method for preparing a super absorbent polymer according to the present invention is subject to f) adding a surface crosslinking agent to each of the mixed hydrogel polymers. In this step, the surface crosslinking agent is added to the hydrous gel phase polymer in which the normal particles and the reassembly are mixed, and the composition of the surface crosslinking agent added to each of the hydrous gel phase polymers according to the particle size may be the same or different in some cases. Can be added in composition.

As long as the surface crosslinking agent added in the manufacturing method of the super absorbent polymer which concerns on this invention is a compound which can react with the functional group which a polymer has, there is no limitation in the structure. As said surface crosslinking agent, Preferably, in order to improve the characteristic of the superabsorbent polymer produced | generated, a polyhydric alcohol compound; Epoxy compounds; Polyamine compounds; Haloepoxy compound; Condensation products of haloepoxy compounds; Oxazoline compounds; Mono-, di- or polyoxazolidinone compounds; Cyclic urea compounds; Polyvalent metal salts; And it may be used one or more selected from the group consisting of alkylene carbonate compounds.

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

Ethylene glycol diglycidyl ether and glycidol may be used as the epoxy compound, and polyamine compounds may be ethylenediamine, diethylenetriamine, triethylenetetraamine, tetraethylenepentamine, or pentaethylenehexamine. , At least one selected from the group consisting of polyethyleneimine and polyamide polyamine can be used.

As the haloepoxy compound, epichlorohydrin, epibromohydrin and α-methyl epichlorohydrin can be used. In addition, as a mono-, di-, or a polyoxazolidinone compound, 2-oxazolidinone etc. can be used, for example. And as an alkylene carbonate compound, ethylene carbonate etc. can be used. These may be used alone or in combination with each other. On the other hand, in order to raise the efficiency of a surface crosslinking process, it is preferable to use including at least 1 type of polyhydric alcohol compounds among these surface crosslinking agents, More preferably, C2-C10 polyhydric alcohol compounds can be used.

In addition, the amount of the surface crosslinking agent added to mix the surface crosslinking agent and to surface-treat the polymer particles may be appropriately selected depending on the kind of the surface crosslinking agent to be added or the reaction conditions. 0.001 to 5 parts by weight, preferably 0.01 to 3 parts by weight, and more preferably 0.05 to 2 parts by weight.

When the content of the surface crosslinking agent is too small, the surface crosslinking reaction hardly occurs, and when it exceeds 5 parts by weight with respect to 100 parts by weight of the polymer, the physical properties of the super absorbent polymer may be lowered due to the excessive surface crosslinking reaction.

At this time, the method of adding a surface crosslinking agent to a polymer does not have the limitation of the structure. The surface crosslinking agent and the polymer powder may be mixed in a reaction tank, a method of spraying the surface crosslinking agent on the polymer powder, a method of continuously supplying and mixing the polymer and the crosslinking agent into a reaction tank such as a mixer operated continuously, and the like.

The method for preparing a super absorbent polymer according to the present invention is subjected to the step of g) performing a surface crosslinking reaction of the hydrogel polymer.

And, according to an embodiment of the present invention, in order to proceed the temperature increase to the reaction temperature for the surface crosslinking reaction after the addition of the surface crosslinking agent within 1 minute to 60 minutes, preferably, when the surface crosslinking agent is added, the temperature of the polymer itself is 20 ℃ to 80 ℃. In order to indicate the temperature of the polymer itself as described above, the process is carried out continuously after the drying step proceeds to a relatively high temperature, and if it is difficult to shorten the process time, or shorten the process time, the polymer may be heated separately. have.

In addition, the method for producing a superabsorbent polymer according to the present invention, after the addition of the surface crosslinking agent, in order to proceed the temperature rise to the reaction temperature for the surface crosslinking reaction within 1 to 60 minutes, the surface crosslinking agent itself added to the polymer is heated You may.

On the other hand, the method for producing a super absorbent polymer according to the present invention is to improve the efficiency of the surface cross-linking process, when the surface cross-linking reaction proceeds after the temperature rise to the reaction temperature for the surface cross-linking reaction within 1 to 60 minutes It is possible to minimize the residual monomer content of the final superabsorbent polymer obtained, and to obtain a superabsorbent polymer having excellent physical properties. At this time, the temperature of the surface crosslinking agent to be added can be adjusted to 5 ° C to 60 ° C, more preferably 10 ° C to 40 ° C. When the temperature of the surface crosslinking agent is less than 5 ° C, the effect of shortening the temperature increase rate to the surface crosslinking reaction according to the temperature of the surface crosslinking agent is insignificant, and when the temperature of the surface crosslinking agent exceeds 60 ° C, the surface crosslinking agent is not evenly dispersed in the polymer. You may not. Throughout this specification, the surface crosslinking reaction temperature may be defined as the total temperature of the polymer and the surface crosslinking agent added for the crosslinking reaction.

And there is no limitation in the structure as a temperature raising means for surface crosslinking reaction. Specifically, the heating medium may be supplied or directly heated by means such as electricity, but the present invention is not limited to the above-described example. Specifically, heat sources that may be used include steam, electricity, ultraviolet rays, infrared rays, and the like, and a heated thermal fluid may be used.

On the other hand, in the manufacturing method of the super absorbent polymer according to the present invention, after the temperature rise for the crosslinking reaction is made, the crosslinking reaction is 1 minute to 60 minutes, preferably 5 minutes to 50 minutes, most preferably 20 minutes to 40 minutes Can proceed. When the crosslinking reaction time is too short (less than 1 minute), a sufficient degree of crosslinking reaction may not occur, and when the crosslinking reaction time exceeds 60 minutes, the physical properties of the super absorbent polymer may deteriorate due to excessive surface crosslinking reaction, Polymer shredding may occur due to prolonged residence in the reactor.

The superabsorbent polymer of the present invention can be prepared using the above production method.

The superabsorbent polymer of the present invention is a superabsorbent polymer comprising a pulverized hydrogel polymer in which a water-soluble ethylenically unsaturated monomer is polymerized.

In the pulverized hydrogel polymer, particles having a particle size of 600 μm or more and 850 μm or less, particles having a particle size of 300 μm or more and 600 μm or less, and particles having a particle size of 150 μm or more and less than 300 μm are mixed, and particles having a size of 450 μm or less are used. The assembled reassembly is surface crosslinked,

0.01 to 3% by weight of particles with a particle size of 600 to 850 μm, 50 to 80% by weight of particles with a size of 300 to 600 μm, and 1 to 150 to 300 μm of particle size, based on the total weight of the normal particles and the reassembly 1 15 to 30% by weight of the reassembled material using particles having a size of ˜25% by weight and a particle size of 450 μm or less.

In addition, the superabsorbent polymer is preferably 0.1 to 2% by weight of the particle size 600 ~ 850㎛ size, 55 ~ 80% by weight particle size 300 ~ 600㎛ size based on the total weight of the normal particles and the reassembly It may include 3 to 25% by weight of particles having a particle size of 150 to 300㎛ size and 15 to 30% by weight of reassembled particles using particles having a particle size of 450㎛ or less.

In addition, the reassembly may be reassembled using particles having a particle size of 400 μm or less.

The superabsorbent polymer prepared by the method of preparing the superabsorbent polymer according to the present invention has a absorption rate of 40 seconds or less measured according to the Vortex measurement method. In addition, the superabsorbent polymer has a saline flow conductivity (SFC) of 50 × 10 ⁻⁷ cm 3 · s / g or more.

Hereinafter, the present invention will be described in more detail with reference to Examples, but embodiments of the present invention disclosed below are exemplified to the last, and the scope of the present invention is not limited to these embodiments. The scope of the invention is indicated in the appended claims, and moreover contains all modifications within the meaning and range equivalent to the claims. In addition, "%" and "part" which show content in a following example and a comparative example are a mass reference | standard unless there is particular notice.

Example

Preparation of hydrogel polymer

100 g of acrylic acid monomer, 38.9 g of caustic soda (NaOH), and 103.9 g of water are mixed, and 0.01 g of diphenyl (2,4,6-trimethylbenzoyl) -phosphine oxide, a photopolymerization initiator, and sodium fur, a thermal polymerization initiator, are mixed with the mixture. The monomer composition was prepared by adding 0.18 g of sulfate and 0.30 g of polyethylene glycol diacrylate as a crosslinking agent. The monomer composition was maintained at 40 ° C. using a thermostat, injected into a rotating belt in the form of a biaxial silicon belt, and irradiated with ultraviolet rays for 60 seconds at an intensity of 10 mW using a mercury UV lamp light source located above the belt. In addition, when the thermal polymerization is performed after the photopolymerization, the internal temperature was maintained at 90 ° C. and a hot air and a thermal insulation device were formed so that the thermal polymerization reaction could occur smoothly.

Thereafter, the hydrogel polymer discharged from the cutter was dried in a hot air dryer at 180 ° C. for 1 hour.

Next, after grinding with a pin mill grinder, particles having a particle size of less than 150 μm, particles having a particle size of 150 μm or more and less than 300 μm, particles having a particle size of 300 μm or more and less than 450 μm, particles having a particle size of 450 μm or more and 600 μm or less, And particles having a particle size of 600 µm or more and 850 µm or less.

The preparation method of the reassembled product was prepared by adding 100 parts by weight of water to 100 parts by weight of particles of less than 450 μm in the classified polymer according to the particle size and mixing them for 1 minute. The reassembly was to increase the adhesion between the particles to adhere to each other, the water content was about 50%.

Subsequently, after grinding with a pin mill grinder, the resultant was dried for 1 hour in a hot air dryer at a temperature of 180 ° C., and particles having a particle size of 150 μm or more and 600 μm or less were selected using a sieve.

The reassembled thus prepared was mixed with the normal particles (150 μm or more and less than 850 μm) classified after drying as shown in Table 1 below to prepare particles before the surface crosslinking.

Table 1

	Normal particles				Reassembly
	850 ~ 600㎛	600 ~ 300㎛	300 ~ 150㎛	content	content
Example 1	One	60	24	85%	15%
Example 2	One	60	16	77%	23%
Example 3	One	60	9	70%	30%
Comparative Example 1	35	50	15	100%	0%
Comparative Example 2	One	67	32	100%	0%
Comparative Example 3	One	60	29	90%	10%

Preparation of Super Absorbent Resin

The superabsorbent polymer was prepared by surface treatment of the particles before the surface crosslinking prepared in Examples 1 to 3 and Comparative Examples 1 to 3. A solution comprising 1.0 parts by weight of 1, 3-propanediol and 3.0 parts by weight of water per 100 parts by weight of the particles before the surface treatment was spray mixed. Thereafter, the mixture was charged into a surface crosslinking reactor, and the surface crosslinking reaction was performed for 30 minutes at 180 ° C. After the surface crosslinking reaction, a step of cooling was further obtained to obtain a super absorbent polymer powder.

Experimental Example: Evaluation of Properties

In order to evaluate the physical properties of the superabsorbent polymers according to Comparative Examples 1 to 3 and Examples 1 to 3, the following test was conducted.

(1) no-load absorption magnification (CRC)

The superabsorbent polymer W (g) (about 0.1 g) according to Comparative Examples 1 to 3 and Examples 1 to 3 was uniformly placed in a bag made of a nonwoven fabric and sealed, and then 0.9 mass at room temperature. Immerse in% saline solution. After 30 minutes, the envelope was centrifuged and drained at 250 G for 3 minutes, and then the mass W2 (g) of the envelope was measured. Moreover, mass W1 (g) at that time was measured after carrying out the same operation without using a resin. Using each mass obtained, CRC (g / g) was computed according to the following formula.

[Equation 1]

CRC (g / g) = {(W2 (g)-W1 (g)) / W (g)}-1

(2) Absorbency under Pressure (AUP)

A stainless steel 400 mesh wire was mounted on the bottom of a plastic cylinder with an inner diameter of 60 mm. 0.90 g of the superabsorbent polymers according to Comparative Examples 1 to 3 and Examples 1 to 3 were uniformly sprayed on the wire mesh under the condition of room temperature and humidity of 50%, respectively, and thereon, 4.83 kPa (0.7 psi) The piston, which can further give a load evenly, has an outer diameter of slightly smaller than 60 mm, no gap with the inner wall of the cylinder, and prevents the movement of the upper and lower sides. At this time, the weight Wa (g) of the apparatus was measured.

A glass filter having a diameter of 90 mm and a thickness of 5 mm was placed inside a petri dish having a diameter of 150 mm, and a physiological saline composed of 0.90% by weight of sodium chloride was made at the same level as the upper surface of the glass filter. One sheet of filter paper having a diameter of 90 mm was placed thereon. The measuring device was placed on the filter paper and the liquid was absorbed for 1 hour under load. After 1 hour, the measuring device was lifted up and the weight Wb (g) was measured.

And pressure absorption capacity was computed from Wa and Wb by following Formula.

[Equation 2]

AUP (g / g) = [Wb (g)-Wa (g)] / mass of absorbent resin (g)

(3) Saline Flow conductivity (SFC)

The SFC value of the present invention is 0.69 weight at 2.07 kPa load for the super absorbent polymer according to Comparative Examples 1 to 3 and Examples 1 to 3 according to the SFC test method disclosed in U.S. Pat. Permeability of the aqueous solution of% sodium chloride was measured.

(4) Vortex-test

2.00 g of superabsorbent polymers according to Comparative Examples 1 to 3 and Examples 1 to 3 were added to a 100 ml beaker with 50 ml of 0.9 wt.% NaCl solution, followed by stirring at 600 rpm using a stirrer. Add each. The vortex (English = vortex) of the liquid which arises by stirring disappeared, and time until the smooth surface was created was measured.

The physical properties measured as described above were measured, and the results are shown in Table 2. In addition, the Vortex time value is shown in FIG. 1, and the SFC value is shown in FIG.

TABLE 2

	Properties
	CRC	0.7 AUP	SFC (10 × cm 3 · s / g)	Vortex (S)
Example 1	29.8	23.7	50.6	38.3
Example 2	29.5	23.2	62.7	34.0
Example 3	31.1	24.6	75.0	31.0
Comparative Example 1	31.0	24.9	39.0	78.0
Comparative Example 2	31.6	24.4	42.5	49.0
Comparative Example 3	30.8	24.7	43.8	42.0

As shown in Table 2, it can be seen that Examples 1 to 3 show the same level of CRC value and 0.7AUP value for Comparative Examples 1 to 3. In addition, through Table 2, Figures 1 and 2, it was found that the Vortex time of the superabsorbent polymers of Examples 1 to 3 of the present invention is much smaller, so that the absorption rate is excellent and the SFC value is also improved. It can be seen that the superabsorbent polymer of has improved permeability and absorption rate compared to the conventional superabsorbent polymer.

Claims (21)

1. a) preparing a hydrogel polymer by thermally polymerizing or photopolymerizing a monomer composition comprising a water-soluble ethylenically unsaturated monomer and a polymerization initiator;

   b) drying the hydrogel polymer;

   c) milling the dried polymer;

   d) the pulverized hydrogel polymer having a particle size of less than 150 μm, a particle size of 150 μm or more and less than 300 μm, a particle size of 300 μm or more and less than 450 μm, a particle size of 450 μm or more and 600 μm or less, and a particle size of 600 μm or more and 850 μm or less Classifying into particles;

   e) The particles having a size of 450 μm or less are used in the pulverized hydrogel polymer, which is a particle having a particle size of 600 μm or more and 850 μm or less, a particle size of 300 μm or more and 600 μm or less, and a particle having a particle size of 150 μm or more and less than 300 μm mixed. Mixing the reassembled reassembled;

   f) adding a surface crosslinking agent to each of said mixed hydrogel polymers; And

   g) performing a surface crosslinking reaction of the hydrogel polymer,

   The hydrogel polymer of step e) is based on the total weight of the normal particles and the reassembly, 0.01 to 3% by weight of the particle size 600 ~ 850㎛, 50 ~ 80% by weight of the particle size 300 ~ 600㎛, A method for producing a superabsorbent polymer comprising 1 to 25 wt% of particles having a particle size of 150 to 300 μm and 15 to 30 wt% of reassembled granules using particles having a particle size of 450 μm or less.
2. The method according to claim 1,

   In step e), the reassembled reassembly is a method for producing a super absorbent polymer, characterized in that the reassembly using a particle size of 400㎛ or less.
3. The method according to claim 1,

   The hydrogel polymer of step e) is based on the total weight of the normal particles and the reassembly, 0.1 ~ 2% by weight of the particle size 600 ~ 850㎛, 55 ~ 80% by weight of the particle size 300 ~ 600㎛, A method for producing a superabsorbent polymer, characterized by comprising 3 to 25% by weight of particles having a particle size of 150 to 300 µm and 15 to 30% by weight of reassembled particles using particles having a particle size of 450 µm or less.
4. The method according to claim 1,

   In the step e), the step of performing the surface crosslinking reaction of the hydrous gel phase polymer is a method for producing a super absorbent polymer, characterized in that the classified hydrogel phase polymer proceeds in one surface crosslinking reactor.
5. The method according to claim 1,

   Before the drying step of step b), the method of producing a super absorbent polymer, characterized in that it further comprises the step of grinding the hydrogel polymer to a particle size of 1mm to 15mm.
6. The method according to claim 1,

   The drying step of step b) is a method for producing a super absorbent polymer, characterized in that at a temperature of 150 ℃ to 250 ℃.
7. The method according to claim 1,

   The surface crosslinking agent may be a polyhydric alcohol compound; Epoxy compounds; Polyamine compounds; Haloepoxy compound; Condensation products of haloepoxy compounds; Oxazoline compounds; Mono-, di- or polyoxazolidinone compounds; Cyclic urea compounds; Polyvalent metal salts; And an alkylene carbonate compound. The method for producing superabsorbent polymer, characterized in that at least one selected from the group consisting of.
8. The method according to claim 1,

   In the step f), the surface crosslinking agent is 0.001 to 5 parts by weight based on 100 parts by weight of the pulverized polymer, characterized in that the manufacturing method of the super absorbent polymer.
9. The method according to claim 1,

   In the step f), the surface temperature of the polymer in the step of adding the surface cross-linking agent is a method for producing a super absorbent polymer, characterized in that 60 to 90 ℃.
10. The method according to claim 1,

    In the step f), the temperature of the surface cross-linking agent to be added is a method of producing a super absorbent polymer, characterized in that 5 to 40 ℃.
11. The method according to claim 1,

    In the step g), the surface crosslinking reaction is a method for producing a super absorbent polymer, characterized in that for 10 minutes to 120 minutes.
12. The method according to claim 1,

    In the step g), the method of producing a super absorbent polymer, characterized in that the temperature is raised by irradiating any one or more selected from a heat source group consisting of steam, electricity, ultraviolet rays and infrared rays.
13. The method according to claim 1,

    The super absorbent polymer has a water absorption rate of 40 seconds or less, according to the Vortex measuring method.
14. The method according to claim 1,

    The super absorbent polymer has a saline flow conductivity (SFC) of 50 × 10 ⁻⁷ cm ³ · s / g or more.
15. The method according to claim 1,

    The reassembly of step e) is prepared by mixing 50 to 300 parts by weight of water per 100 parts by weight of particles of less than 450 ㎛ in a mixer rotating at high speed for 30 seconds to 5 minutes to prepare a super absorbent polymer.
16. A superabsorbent polymer comprising a pulverized hydrogel polymer polymerized with a water-soluble ethylenically unsaturated monomer,

    In the pulverized hydrogel polymer, particles having a particle size of 600 μm or more and 850 μm or less, particles having a particle size of 300 μm or more and 600 μm or less, and particles having a particle size of 150 μm or more and less than 300 μm are mixed, and particles having a size of 450 μm or less are used. The assembled reassembly is surface crosslinked,

    0.01 to 3% by weight of particles having a particle size of 600 to 850 μm, 50 to 80% by weight of particles having a size of 300 to 600 μm, and 1 to 150 to 300 μm of particle size, based on the total weight of the normal particles and the reassembly 1 A superabsorbent polymer comprising from 15 to 30% by weight of the reassembled using particles of 25 to 25% by weight and the particle size of 450㎛ or less.
17. The method according to claim 16,

    The reassembled superabsorbent polymer, characterized in that the reassembly using a particle size of 400㎛ or less
18. The method according to claim 16,

    The super absorbent polymer,

    0.1-2% by weight of particles with a particle size of 600-850 μm, 55-80% by weight of particles with a size of 300-600 μm, and particles of 150-300 μm with a particle size, based on the total weight of the normal particles and the reassembly 3 Superabsorbent polymer, characterized in that it comprises 15 to 30% by weight of the reassembled by using the particles having a particle size of ~ 25% by weight and 450㎛ or less
19. The method according to claim 16,

    The super absorbent polymer is a super absorbent polymer, characterized in that the absorption rate measured in accordance with the Vortex measuring method is 40 seconds or less.
20. The method according to claim 16,

    The super absorbent polymer has a saline flow conductivity (SFC) of 50 × 10 ⁻⁷ cm ³ · s / g or more.
21. The method according to claim 16,

    The superabsorbent polymer is super absorbent, characterized in that produced by the method of claim 1.

Images