WO2017111210A1 - Superabsorbent polymer and preparation method therefor - Google Patents

Abstract

The present invention relates to a superabsorbent polymer having an improved absorption rate by means of micropores formed therein, and a preparation method therefor. The superabsorbent polymer comprises a base resin powder comprising a cross-linked polymer of a water-soluble ethylene-based unsaturated monomer having an acidic group of which at least one portion is neutralized, wherein the base resin powder has formed therein a plurality of pores having diameters of 1µm or greater, and the cross-linked polymer comprises layered silicate particles dispersed in the cross-linked structure thereof.

Description

 【Specification】

 [Name of invention]

 Superabsorbent polymer, and preparation method thereof

 Technical Field

Cross Citation with Related Application (s)

 This application claims the benefit of priority based on Korean Patent Application No. 10-2015-0184616 of December 23, 2015 and Korean Patent Application No. 10-2016-0044324 of April 11, 2016, and the Korean patent application All content disclosed in the literature is incorporated as part of this specification. The present invention relates to a super absorbent polymer, and a method for producing the same. More specifically, the present invention relates to a highly absorbent resin having an improved absorption rate through micropores formed therein and a method of manufacturing the same.

 [Invention and background technology]

A super absorbent polymer (SAP) is a synthetic polymer material that can absorb about 500 to 1000 times its own weight. It is a super absorbent mater (AL) and an absorbent gel mater (ALM). It is also called. Super absorbent ^' resins have been put into practical use as sanitary devices, and are currently used in various materials such as hygiene products such as paper diapers for children, horticultural soil repair agents, civil engineering materials, seedling sheets, and freshness retainers in food distribution. It is widely used.

 As a method for producing such a super absorbent polymer, a method by reverse phase suspension polymerization or a solution polymerization is known. Among them, the production of superabsorbent polymers through reverse phase suspension polymerization is disclosed in, for example, Japanese Patent Laid-Open Nos. 56-161408, 57-158209, and 57-198714. In addition, the production of superabsorbent polymers through polymerization of aqueous solution is a thermal polymerization method in which a hydrogel polymer is broken and immersed in a half-die with multiple axes, and is polymerized by irradiating ultraviolet light to a high concentration of aqueous solution on a belt. The photopolymerization method etc. which perform simultaneously and drying are known.

Meanwhile, the absorption rate, which is one of the important physical properties of the superabsorbent polymer, Similarly, the surface dryness of the product in contact with the skin. In general, this absorption rate can be improved by increasing the surface area of the superabsorbent polymer.

 For example, a method of forming a porous structure on the particle surface of the super absorbent polymer by using a blowing agent has been applied. However, there is a disadvantage in that the general foaming agent cannot form a porous structure of each layer, so that the increase in absorption rate is not large.

 As another example, there is a method of increasing the surface area by reassembling the fine powder obtained in the manufacturing process of the super absorbent polymer to form porous particles of irregular shape. However, although the absorption rate of the superabsorbent polymer can be improved through this method, there is a limit that the water retention capacity (CRC) and the pressure absorption capacity (AUP) of the resin are relatively lowered. As such, the physical properties such as absorption rate, water holding capacity, and pressure absorbing capacity of the super absorbent polymer are trade-off (f). Therefore, there is an urgent need for a manufacturing method capable of improving these properties simultaneously.

 Prior Art Documents

 [Patent literature]

 (Patent Document 1) 1. Japanese Patent Application Publication No. 56-161408

(Patent Document 2) 2. Japanese Patent Application Publication No. 57-158209

(Patent Document 3) 3. Japanese Patent Laid-Open No. 57-198714

 [Content of invention]

 Problem to be solved

 The present invention is to provide a super absorbent polymer having an improved absorption rate through the fine pores formed therein.

 In addition, the present invention is to provide a method for producing the super absorbent polymer.

 [Measures of problem]

In the present specification, a base resin powder comprising a water-soluble ethylene-based unsaturated monomer cross-linked polymer having at least a part of the neutralized acidic group, a plurality of pores of diameter 1 or more is formed in the base resin powder, Layered silica dispersed in the crosslinked structure A superabsorbent polymer is included which contains particles of particles and has a time of 60 seconds or less for removing the vortex generated when stirring at a speed of 600 rpm in 50 m of a 0.9 wt% NaCl solution.

 The present disclosure also provides a step of crosslinking and polymerizing a water-soluble ethylenically unsaturated monomer having at least a part of a neutralized acidic group in the presence of layered silicate particles, a blowing agent and an internal crosslinking agent to form a hydrogel polymer; And drying, pulverizing, and classifying the hydrogel polymer to form a base resin powder.

 Hereinafter, a super absorbent polymer according to a specific embodiment of the present invention, and a preparation method thereof will be described in detail. Unless otherwise stated throughout the specification, "including" or "containing" means including any component (or component) without limitation, except for the addition of other components (or components). In this specification, (meth) acrylate [(meth) acrylate] is an acrylate

It is meant to include both acrylates and methacrylates. According to one embodiment of the invention, at least a part comprises a base resin powder containing a cross-linked polymer of a water-soluble ethylene-based unsaturated monomer having an acidic group, a plurality of pores of diameter 1 or more is formed in the base resin powder The crosslinked polymer includes layered silicate particles dispersed in the crosslinked structure, and a superabsorbent polymer having a time of removing vortex generated when stirring at a speed of 600 rpm at a weight of 0.9 wt. Can be provided.

The present inventors can use the above-described superabsorbent polymer, by using a specific layered silicate particles, a number of micropores can be stably formed in the crosslinked polymer, the contact area to water is rapidly increased and superabsorbent Experiments confirmed that the absorption rate of the resin can be further improved and completed the invention. Specifically, the super absorbent polymer may include a base resin powder including a crosslinked polymer of a water-soluble ethylenically unsaturated monomer having at least a portion of neutralized acidic groups. The "crosslinked polymer of water-soluble ethylenically unsaturated monomer" refers to a hydrogel polymer immediately formed by thermal polymerization or photopolymerization to a composition containing a water-soluble ethylenically unsaturated monomer, as well as to a general method for producing a super absorbent polymer. The polymer having dried the hydrogel polymer, the polymer obtained by pulverizing the dried gel polymer or dried polymer, the polymer before performing the surface crosslinking reaction, or the polymer after performing the surface crosslinking reaction. As long as the ethylenically unsaturated monomer is a polymerized polymer, it can be included regardless of its form, water content, particle size, surface crosslinking or the like.

 The super absorbent polymer of the above embodiment basically includes a polymer obtained by crosslinking polymerization of the water-soluble ethylenically unsaturated monomer as a base resin powder, as in the previous super absorbent polymer.

In the super absorbent polymer of this embodiment, the water-soluble ethylene-based unsaturated monomer, acrylic acid, methacrylic acid, maleic anhydride, fumaric acid, crotonic acid, itaconic acid, 2-acryloylethane sulfonic acid, 2-methacrylo Anionic monomers of monoethanesulfonic acid, 2- (meth) acryloylpropanesulfonic acid, or 2- (meth) acrylamide-2-methyl propane sulfonic acid and salts thereof; (Meth) acrylamide, N-substituted (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, mesopolyethylene glycol (meth) acrylate or polyethylene Nonionic hydrophilic-containing monomers of glycol (meth) acrylates; And amino group-containing unsaturated monomers of (Ν, Ν) -dimethylaminoethyl (meth) acrylate or (Ν, Ν) -dimethylaminopropyl (meth) acrylamide and quaternized products thereof; 1 selected from the group consisting of More than one species can be used. Among these, alkali metal salts such as acrylic acid or salts thereof, for example, acrylic acid and / or sodium salts of which at least a portion of acrylic acid is neutralized may be used, and such monomers may be used for superabsorbent polymers having superior physical properties. Manufacturing becomes possible. When the alkali metal salt of acrylic acid is used as a monomer, acrylic acid can be neutralized with a basic compound such as caustic soda (NaOH). In addition, the crosslinked polymer included in the base resin powder may include a crosslinked structure in which polymer chains of the water-soluble ethylenically unsaturated monomer are crosslinked through a crosslinkable functional group of an internal crosslinking agent. As the internal crosslinking agent for introducing a basic crosslinking structure into the crosslinked polymer and the base resin powder, any internal crosslinking agent having a crosslinkable functional group, which has been conventionally used in the production of superabsorbent polymers, can be used without particular limitation. However, in order to improve the physical properties of the superabsorbent polymer by introducing an appropriate crosslinking structure into the crosslinked polymer and the base resin powder, a multifunctional acrylate compound having a plurality of ethylene oxide groups may be used as the internal crosslinking agent. More specific examples of such internal crosslinking agents include polyethylene glycol diacrylate (PEGDA), glycerin diacrylate, glycerin triacrylate, ungalzal or ethylated trimethylol triacrylate (TMPTA), nucleic acid diol diacrylate, And triethylene glycol diacrylate. On the other hand, a plurality of pores of diameter 1 / ai or more may be formed in the base resin powder. The pores are implemented by a blowing agent added together in the monomer composition, as shown in the method of preparing a superabsorbent polymer, which will be described later. As shown in FIG. 2, a plurality of pores having a minimum diameter of 1 or more are formed on the base powder. It can be confirmed that it is formed. The pores may be present in a single or plural form, evenly dispersed in the base resin powder.

 In particular, among the plurality of pores of diameter 1 / or more contained in the base resin powder may include micropores having a diameter of 10 to 100. The micropores having a diameter of 10 to 100 im may be formed by adding a blowing agent and inorganic particles together when forming a polymer, as will be described later. As the micropores are stably formed, the microporosity is increased. The absorption rate of the water absorbent resin can be further improved.

In addition, the crosslinked polymer included in the base resin powder may include layered silicate particles dispersed in the crosslinked structure. The layered silicate-based particles include a metal oxide layer including a metal oxide and a silica layer formed on at least one surface of the metal oxide layer and include silica. Particles containing unit crystals can be used.

 The unit crystal refers to a periodic unit of crystalline particles having three-dimensional periodicity, and particles may be formed through repetition of the unit crystal.

 The unit crystal of the layered silicate-based particles may be formed on at least one surface of the metal oxide worm including a metal oxide and the metal oxide layer, and may include a silica layer including silica. That is, the silica layer may be formed on one or both surfaces of the metal oxide layer in the unit crystal of the layered silicate particles.

 Specifically, the metal oxide layer and the silica layer may be combined through siloxane bonding. The siloxane (si loxane) bond means a covalent bond between a silicon atom (Si) and an oxygen atom (0), and more specifically, an octahedral form, such as a unit crystal structure shown in FIG. 1. A bond between the metal oxide and the silica layer may be formed through a covalent bond between an oxygen atom included in the metal oxide filling of the silicon atom and a silicon atom included in the silica layer of the tetrahydral (Tet rahedra l) form.

 In the metal oxide layer, the metal oxide may exist in a state in which a metal atom and an oxygen atom are combined, and examples of the metal atom are not particularly limited, and lithium, sodium, potassium, and the like are group 1 or group 2 elements of the periodic table. Beryllium, magnesium, calcium and the like.

 Accordingly, the packed silicate-based particles can stably maintain fine pores in the crosslinked polymer, thereby increasing the contact area with water and further improving the absorption rate of the super absorbent polymer.

 The layered silicate particles have a maximum diameter of 1 nm to 100 nm in straight section, and a height of 0. It may have a light structure of 1 nm to 20 nm. The columnar structure means a three-dimensional shape in which the upper and lower surfaces are parallel to each other. Although the specific shape of the column structure is not limited, for example, depending on the type of cross section in which the layered silicate particles are cut in a direction parallel to the ground, that is, depending on the type of figure represented by the straight cross section, an ellipsoid, etc. , Diversification, and the like.

As described above, the columnar structure of the layered silicate particles is It can be formed through the repetition of the unit crystal, the maximum diameter of the straight cross-section in the lamp structure means the largest value among the diameter that the cross section cut the layered silicate particles in a direction parallel to the ground.

 As described above, the layered silicate particles have a maximum diameter of 1 nm to 100 ran in a straight section, and a height of 0. As having a structure of lnm to 20 nm, the layered silicate-based particles in the cross-linked polymer of the embodiment can implement functionality in the cross-linked polymer through a fine particle size, as well as monomers when forming the cross-linked polymer. It is possible to stabilize the micropores formed by the blowing agent in the composition.

 Examples of the layered silicate-based particles are not particularly limited, for example, nuclear lite (Laponi te RD, Laponi te XLG, Laponi te D, Laponi te DF, Laponi te RS, Laponi te XLS, Laponi te DS, Laponi te Te S and Laponi te JS, etc.), and Laponi te RD is more preferable.

 In addition, the layered silicate-based particles described above may be included in an amount of 0.01 parts by weight to 5 parts by weight based on 100 parts by weight of the base resin powder. Thus, the degree of formation of micropores in the crosslinked polymer is optimized, so that the superabsorbent polymer of one embodiment may have an improved absorption rate.

 Specifically, the superabsorbent polymer of the embodiment has a time for removing vortex generated when stirring at a speed of 600 rpm at 50% of 0.9 wt% NaCl solution at 60 seconds or less, or 40 seconds to 60 seconds, or 50 seconds to It may be 58 seconds. When stirring at a speed of 600 rpm at 50 m of the 0.9 wt. NaCl solution, the superabsorbent resin of the embodiment is added to the 0.9 wt.% NaCl solution, and the vortex is absorbed by the superabsorbent polymer. Can be removed.

 More specifically, the time to remove the vortex is added to the superabsorbent resin 2.00 g of the embodiment, while stirring 50 ra £ of 0.9% by weight of NaCl solution at 600 rpm using a stirrer, the vortex of the liquid generated by stirring This can be obtained by measuring the time until the vortex disappears and a smooth surface is obtained.

The time for removing the vortex generated when stirring the superabsorbent polymer of the embodiment at a speed of 600 rpm in a NaCl solution 50 of 0.9 wt. When added, as the absorption rate of the superabsorbent polymer is slowed down, it may be difficult to realize rapid absorption when applied to a product such as a diaper. In the prior art, an attempt was made to increase the surface area through the porous structure by applying a blowing agent to improve the absorption rate of the super absorbent polymer. Levels of absorption can be achieved.

 In addition, the superabsorbent polymer may have a water-retaining capacity of 45 g / g or more, or 45 g / g to 60 g / g for physiological saline measured according to the EDANA WSP 241.2 method. Centrifuge water capacity (CRC) for physiological saline can be measured according to the method of EDANA method WSP 241.2. More specifically, the water retention capacity may be calculated by Equation 1 after absorbing the superabsorbent polymer in physiological saline over 30 minutes.

 [Calculation 1]

CRC (g / g) =. {[W ₂ (g)-W ₁ (g)] / W ₀ (g)}-1

 In the above formula 1,

W ₀ (g) is the initial weight (g) of the superabsorbent polymer, W g) is the weight of the device measured after dehydration at 250 G for 3 minutes using a centrifuge without using the superabsorbent polymer, (g) Is the weight of the device, including the superabsorbent resin, after absorbing the superabsorbent polymer by immersion in 0.9 wt% physiological saline for 30 minutes at room temperature for 30 minutes and then dehydrating it at 250 G for 3 minutes using a centrifuge.

In addition, the superabsorbent polymer of the above-described embodiment may have a spherical or amorphous particle shape having a particle diameter of about 150 μΐ ̃ 850 / m. On the other hand, according to another embodiment of the present invention, in the presence of the layered silicate-based particles, the blowing agent and the internal crosslinking agent, the step of cross-polymerizing a water-soluble ethylenically unsaturated monomer having an acidic group at least partially neutralized to form a hydrogel polymer ; And drying, grinding and classifying the hydrogel polymer to form a base resin powder. In the production method of this another embodiment, the layered silicate particles are used together with conventional blowing agents and internal crosslinking agents, to form a water-soluble ethylene-based The crosslinking polymerization of the unsaturated monomer may be carried out, followed by drying, pulverization, classification, surface crosslinking, and the like according to a general manufacturing method of the superabsorbent polymer to prepare a superabsorbent polymer. As such, in the crosslinking polymerization step of the water-soluble ethylenically unsaturated monomer, as the layered silicate particles and the blowing agent are used together, fine bubbles generated by the blowing agent can be stably maintained by the layered silicate particles. The absorption rate of the superabsorbent polymer to be prepared can be improved more, and the base resin powder having the crosslinked structure already formed by the use of an internal crosslinking agent can be prepared, thereby realizing various physical properties such as excellent water retention.

 The superabsorbent polymer of one embodiment may be prepared by the method of preparing the superabsorbent polymer of another embodiment.

 Specifically, the method of preparing the superabsorbent polymer includes forming a hydrogel polymer by crosslinking and polymerizing a water-soluble ethylenically unsaturated monomer having at least a part of a neutralized acidic group in the presence of a packed silicate particle, a blowing agent, and an internal crosslinking agent. It may include.

 As the layered silicate-based particles, particles including a metal oxide layer containing a metal oxide and unit crystals formed on at least one surface of the metal oxide layer and including a silica layer containing silica may be used.

 The unit crystal refers to a periodic unit of crystalline particles having a three-dimensional periodicity, particles may be formed through the repeating of the unit crystal.

 The unit crystal of the layered silicate particles may be formed on at least one surface of the metal oxide layer including the metal oxide and the metal oxide layer, and may include a silica layer including silica. That is, the silica layer may be formed on one or both surfaces of the metal oxide layer in the unit crystal of the layered silicate particles.

Specifically, the metal oxide layer and the silica layer may be bonded through a siloxane (si loxane) bond. The siloxane (si loxane) bond means a covalent bond between a silicon atom (Si) and an oxygen atom (0), and more specifically, as shown in the unit crystal structure shown in FIG. 1, in the form of an octahedral Oxygen atoms contained in the metal oxide layer and tetrahedral silica layer Covalent bonding between the silicon atoms included may form a bond between the metal oxide and the silica layer.

 In the metal oxide layer, the metal oxide may exist in a state where a metal atom and an oxygen atom are combined, and examples of the metal atom are not particularly limited, but lithium, sodium, potassium, and the like are group 1 or group 2 elements of the periodic table. Beryllium, magnesium, calcium and the like.

 The layered silicate particles may have a structure having a maximum diameter of 1 nm to 100 ran and a height of O.lnm to 20 ran, or O.lnm to 20 ran. The columnar structure means a three-dimensional figure in which the upper and lower surfaces are parallel to each other. Although the specific shape of the column structure is not limited, for example, depending on the type of cross section in which the layered silicate particles are cut in a direction parallel to the ground, that is, depending on the type of figure represented by the straight cross section, an ellipsoid, etc. Polygonal column etc. are mentioned.

 As described above, the columnar structure of the layered silicate particles may be formed through repetition of the unit crystal, and the maximum diameter of the straight section in the lamp structure is a cross section of the layered silicate particles cut in a direction parallel to the ground. It means the largest value among the diameters it can have.

 As the layered silicate particles have a structure having a maximum diameter of 1 nm to 100 ran and a height of O.lnm to 20 ran, the layered silicate particles in the crosslinked polymer of the present embodiment are The fine particle size may not only implement functionality in the crosslinked polymer, but also stabilize the fine pores formed by the blowing agent in the monomer composition when the crosslinked polymer is formed.

 Examples of the layered silicate-based particles are not particularly limited, for example, hackite (Laponite RD, Laponite XLG, Laponite D, Laponite DF, Laponite RS, Laponite XLS, Laponite DS, Laponite S and Laponite JS, etc.). A more preferable example is Laponite RD.

Examples of the blowing agent are not particularly limited, and various blowing agents well known in the art may be used without limitation. Specifically, for example, azodi carbonamide, azodicarboxyamide, benzenesulfonylhydrazide, dinitrosopenta And at least one selected from the group consisting of methylenetetramine, toluenesulfonylhydrazide, azobisisobutyronitrile, azo dicarboxylic acid barium and sodium bicarbonate.

 As described above, the step of cross-polymerizing the water-soluble ethylene-based unsaturated monomer having at least a part of the neutralized acid group to form a hydrogel polymer may be carried out in the presence of the layered silicate particles, the blowing agent and the internal crosslinking agent.

 As such, instead of forming the hydrogel polymer and then adding the layered silicate particles and the blowing agent, the fine pores even inside the hydrogel polymer by adding the layered silicate particles and the blowing agent to the monomer composition for forming the hydrogel polymer. Can be formed.

 At this time, the content of the layered silicate particles based on 100 parts by weight of the blowing agent is 1 to 1000 parts by weight, or 1 to 500 parts by weight, or 1 to 100 parts by weight, or 1 to 50 parts by weight. Or, 10 parts by weight to 30 parts by weight. When the content of the layered silicate particles is excessively reduced based on the blowing agent content, the pore stabilization effect by the layered silicate particles may be reduced to reduce the absorbency of the super absorbent polymer.

 On the other hand, if the content of the layered silicate particles is excessively increased based on the content of the blowing agent, as the viscosity of the solution in which the layered silicate particles are dispersed rapidly increases, it may be difficult to transfer the superabsorbent polymer manufacturing process.

 On the other hand, the step of forming the hydrogel polymer, more specifically, forming a crab 1 solution containing an internal crosslinking agent and a water-soluble ethylenically unsaturated monomer having at least a part of the neutralized acid group; Forming a crab dilute solution comprising a packed silicate-based particle and a foaming agent; And crosslinking and polymerizing the monomer composition including the first solution and the second solution.

At least a part of the internal crosslinking agent may include a water-soluble ethylene-based unsaturated monomer, a layered silicate-based particle, and a blowing agent having a neutralized acidic group, as described above in one embodiment. Specifically, in the step of forming a system 1 solution containing the internal crosslinking agent and a water-soluble ethylenically unsaturated monomer having at least a part of the neutralized acidic group, the content of the internal crosslinking agent is 0.01 weight based on 100 parts by weight of the water-soluble ethylenically unsaturated monomer Parts to 5 parts by weight.

 In addition, in the forming of the second solution including the layered silicate particles and the blowing agent, the content of the layered silicate particles is 1 part by weight to 1000 parts by weight or 1 part by weight based on 100 parts by weight of the blowing agent as described above. 500 parts by weight, or 1 part by weight to 100 parts by weight, or 1 part by weight to 50 parts by weight, or 10 parts by weight to 30 parts by weight.

 In addition, in the step of crosslinking and polymerizing the monomer composition including the first solution and the second solution, the content of the second solution is 1 part by weight to 100 parts by weight relative to 100 parts by weight of the first solution included in the monomer composition. Or, 50 parts by weight to 100 parts by weight, or 80 parts by weight to 100 parts by weight.

 The first solution, the second solution, and the monomer composition may further each independently include a polymerization initiator generally used for preparing a super absorbent polymer.

 Specifically, the polymerization initiator may use a thermal polymerization initiator or a photopolymerization initiator according to UV irradiation depending on the polymerization method. However, even by the photopolymerization method, since a certain amount of heat is generated by irradiation of ultraviolet rays or the like, and a certain amount of heat is generated in accordance with the progress of the polymerization reaction, which is an exothermic reaction, it may additionally include a thermal polymerization initiator. have.

 The photopolymerization initiator may be used without any limitation as long as it is a compound capable of forming radicals by light such as ultraviolet rays.

As the photopolymerization initiator, for example, benzoin ether, dialkyl acetophenone, hydroxyl alkylketone, phenylglyoxylate, benzyldimethyl ketal Dimethyl Ketal), acyl phosphine and alpha-aminoketone ((1-& 1 ^ 1101 101) may be used.One embodiment of acylphosphine is commercially available. Lucir in TP0, ie, 2,4,6-trimethyl-benzoyl-trimethyl phosphine oxide (2,4,6-trimethyl-benzoyl-trimethylphosphine oxide) can be used. Reinhold Schwa lm, "UV Coatings: Basics, Recent Developments and New Application (Elsevier 2007)" pll5, as well as, but not limited to, the examples described above.

 The photopolymerization initiator may be included in a concentration of about 0.01% by weight to about 1.0% by weight based on the monomer composition. When the concentration of the photopolymerization initiator is too low, the polymerization rate may be slow. When the concentration of the photopolymerization initiator is too high, the molecular weight of the superabsorbent polymer may be low and the physical properties may be uneven.

In addition, the thermal polymerization initiator may be used at least one selected from the group consisting of persulfate initiator, azo initiator, hydrogen peroxide and ascorbic acid. Specifically, examples of persulfate-based initiators include sodium persulfate (NasS), potassium persulfate (K2S208), ammonium persulfate (NH ₄ ) ₂ S ₂ 0 ₈ , and the like. . Examples of azo initiators include 2, 2-azobis- (2-amidinopropane) dihydrochloride (2, 2- azob is (2-am idi nopr opane) dihydrochlor ide), 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-yDpropane] dihydrochlor ide), 4,4-azobis- (4-cyanovaleric acid) (4,4-azobis- (4-cyanovaleric acid)), etc. For more thermal polymerization initiators, see Odian's Principle. of Polymer izat ion (Wi ley, 1981) ¹ , p203, and is not limited to the above examples.

The thermal polymerization initiator may be included in a concentration of about 0.001% to about 0.5% by weight based on the monomer composition. If the concentration of the thermal polymerization initiator is too low, additional thermal polymerization hardly occurs, and the effect of adding the thermal polymerization initiator may be insignificant. If the concentration of the thermal polymerization initiator is excessively high, the molecular weight of the superabsorbent polymer is small and the physical properties are uneven. Can be done. In the monomer composition including the first solution and the second solution, the concentration of the water-soluble ethylenically unsaturated monomer includes each of the above-described raw materials and solvents. 20 wt% to about 60 wt%, or 40 wt% to about 50 wt% with respect to the total monomer composition, and may be appropriate concentration in consideration of polymerization time and reaction conditions. However, if the concentration of the monomer is too low, the yield of the superabsorbent polymer may be low and there may be a problem in economics. On the contrary, if the concentration is too high, some of the monomer may precipitate or the grinding efficiency of the polymerized hydrogel polymer may be low. This may cause problems in the process, and the physical properties of the super absorbent polymer may be reduced.

 The crab 1 solution, the system 2 solution, and the monomer composition may each independently include additives such as thickeners, plasticizers, preservative stabilizers, antioxidants, and neutralizers, as necessary.

 The neutralizing agent is added to prevent the pH decrease due to the water-soluble ethylenically unsaturated monomer, it can be used without a great restriction as long as the basic material of pH7 or more. Examples of the neutralizing agent include caustic soda (NaOH) and the like.

 Examples of the method of adding the neutralizing agent to the monomer composition are not particularly limited, but, for example, a neutralizing agent is added to a crab 1 solution including an internal crosslinking agent and a water-soluble ethylenically unsaturated monomer having at least a partially acidified acidic group, and then layered silicate. A second solution containing system particles and blowing agent can be added.

 Raw materials such as the above-mentioned water-soluble ethylenically unsaturated monomers, silicate particles, photopolymerization initiators, thermal polymerization initiators, internal crosslinking agents and additives may be added in a dissolved form in a solvent.

The solvent that can be used at this time can be used without limitation the composition as long as it can dissolve the above-mentioned components, for example, water, ethanol, ethylene glycol, diethylene glycol, triethylene glycol, 1, 4- Butanediol, propylene glycol, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, methyl ethyl ketone, acetone, methyl amyl ketone, cyclonucleanone, cyclopentanone, diethylene glycol monomethyl Ether, diethylene glycol ethyl ether, toluene, xylene, butyrolactone, carbye may be used in combination of one or more selected from methyl cellosolve acetate and Ν, Ν-dimethylacetamide. On the other hand, the method of forming a hydrogel by thermal polymerization or photopolymerization of such a monomer composition is not particularly limited as long as it is a commonly used polymerization method.

 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 semi-unggi having a stirring axis such as kneader, when the photopolymerization, Although it can proceed in a semi-unggi equipped with a movable conveyor belt, the above-described polymerization method is an example, the present invention is not limited to the above-described polymerization method.

 For example, as described above, the water-containing gel polymer obtained by thermal polymerization by supplying hot air or by heating the reactor to a reactor such as a kneader equipped with a stirred shaft may be a semi-unggi machine. The hydrogel polymer discharged to the outlet may be in the form of several centimeters to several millimeters. Specifically, the size of the hydrogel polymer obtained may vary depending on the concentration and injection speed of the monomer composition to be injected, and a hydrogel polymer having a weight average particle diameter of about 2 mm to about 50 mm 3 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. In this case, the thickness of the polymer sheet depends on the concentration and the injection speed of the monomer composition to be injected, but it is usually preferable to supply the monomer composition so that a polymer on the sheet having a thickness of about 0.5 cm to about 5 cm can be obtained. Do. When supplying the monomer composition to such an extent that the thickness of the polymer on the sheet is too thin, the production efficiency is not preferable, and when the polymer thickness on the sheet exceeds 5 cm, due to the excessively thick thickness, the polymerization reaction spreads over the entire thickness. It may not happen evenly.

In this case, the normal water content of the hydrogel polymer obtained by the above method may be 40 to 80% by weight. On the other hand, throughout the present specification "water content" means the amount of water to account for the total amount of water-containing gel polymer weight minus the weight of the polymer in the dry state. Specifically, the moisture vapor in the polymer during the process of raising the temperature of the polymer through infrared heating to dry The weight loss along the foot is measured and defined as the calculated value. At this time, the drying condition is to increase the temperature to about 180 ° C at room temperature and then maintained at 180 ° C total drying time is set to 20 minutes, including 5 minutes of temperature rise step, the moisture content is measured.

 After the crosslinking polymerization of the monomer, the base resin powder may be obtained through drying, pulverization and classification, and the like, and the base resin powder and the super absorbent water obtained therefrom through such a pulverization and classification process. Paper is suitably prepared and provided to have a particle size of about 150 prn to 850. More specifically, at least about 95% by weight or more of the base resin powder and the super absorbent polymer obtained therefrom have a particle size of about 150 rn to 850, and the fine powder having a particle size of less than about 150 urn may be less than about 3% by weight. Can be. Thus, as the particle size distribution of the base resin powder and the super absorbent polymer is adjusted to a preferred range, the final manufactured super absorbent polymer may exhibit the above-described physical properties and better liquid permeability.

 On the other hand, it will be described in more detail with respect to the progress of the drying, grinding and classification as follows.

 First, in drying the hydrogel polymer, if necessary, the step of coarsely pulverizing before drying may be further increased to increase the efficiency of the drying step.

 At this time, the pulverizer used is not limited in configuration, and specifically, a vertical pulverizer, a turbo cutter, a turbo grinder, a rotary cutter mill, a cutting machine Selected from the group of crushing machines consisting of cutter mill, disc mill, shred crusher, hammer mill crusher, crusher, chopper and disc cutter It may include any one, but is not limited to the above-described example.

At this time, the coarse grinding step may be pulverized so that the particle size of the hydrogel polymer is about 2 mm to about 10 mm 3. Grinding to a particle diameter of less than 2 mm is not technically easy due to the high water content of the hydrogel polymer, and may also cause a phenomenon in which the pulverized particles cross each other. On the other hand, the particle diameter is more than 10 mm In the case of pulverization, the effect of increasing the efficiency of the subsequent drying step may be insignificant.

As described above, drying is performed on the hydrogel polymer immediately after polymerization, which is coarsely pulverized or not subjected to the coarsely pulverized step. At this time, the drying temperature of the drying step may be about 150 ^° C to about 250 ^° C. If the drying temperature is less than about 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 about 250 t, only the polymer surface is dried excessively. Fine powder may generate | occur | produce in the grinding | pulverization process made and there exists a possibility that the physical property of the superabsorbent polymer formed finally may fall. Thus preferably the drying can be carried out at a temperature of about 150 ^° C to about 200 ^° C.

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

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

 Next, a step of pulverizing the dried polymer obtained through this drying step is carried out.

 The polymer powder obtained after the milling step may have a particle diameter of about 150 to about 850 mm 3. The grinder used to grind to such a particle size is specifically a pin mill, hammer mill, screw mill, roU mill, disc mill, A jog mill or a sieve may be used, but is not limited to the example described above.

In addition, in order to manage the physical properties of the super absorbent polymer powder to be finalized after such a grinding step, a separate process of classifying the polymer powder obtained after grinding according to the particle diameter may be performed. Preferably, the polymer having a particle size of about 150 to about 850 is classified, and only a polymer powder having such a particle size may be further commercialized through a surface crosslinking reaction step as necessary. Can be. Since the particle size distribution of the base resin powder obtained through this process has already been described above, further detailed description thereof will be omitted.

 【Effects of the Invention】

 According to the present invention, a super absorbent polymer having an improved absorption rate through micropores formed therein, and a method of manufacturing the same may be provided.

 [Brief Description of Drawings]

 Figure 1 schematically shows the structure of the unit crystal of the layered silicate particles used in the example.

 Figure 2 is a SEM image of the surface of the super absorbent polymer prepared in Example.

 [Specific contents to carry out invention]

 The invention is explained in more detail in the following examples. However, the following examples are only for exemplifying the present invention, and the contents of the present invention are not limited to the following examples.

<Examples 1 to 2: Preparation of Super Absorbent Polymer>

 practice

 To 226 g of acrylic acid, add 0.1 g of bis (2,4,6-trimethylbenzoyl) -phenyl phosphine oxide (IGRARCURE 819) as a photopolymerization initiator, and mix for 5 minutes, and then polyethylene glycol diacrylate (Mi ramer M280) 5.2 as a crosslinking agent. g was added and mixed for 10 minutes to prepare a monomer solution.

 3.5 g of sodium persulfate, a thermal polymerization initiator, was added to 156 g of ionized water, dissolved until completely dissolved in this warm water, and 3.2 g of laponite RD, a layered silicate-based particle, was added to the inorganic particles and mixed for 30 minutes. Thereafter, 17.7 g of sodium hydrogen carbonate was added as a blowing agent and mixed for 10 minutes to prepare a mixed aqueous solution.

 A caustic soda solution was prepared by mixing 195 g of ionized water with 661 g of 32% caustic soda (NaOH).

483g acrylic acid in 20 ^° C angle 2L double jacketed glass reaction machine 55 g of the monomer solution was added and mixed for 5 minutes. Thereafter, the caustic soda solution was added for 10 minutes and neutralized. The temperature was raised to about 65 ^° C by the heat of neutralization, and waited until the ^{angle of} 42 ^° C., 54.8 g of the mixed aqueous solution was added and mixed for 1 minute to prepare a monomer composition.

 The monomer composition was introduced into a supply unit of a polymerizer consisting of a continuously moving conveyor belt, irradiated with ultraviolet rays for 1 minute (irradiation amount: 2 mW / ciif) with a UV irradiation device having a 10 mW illuminance, and then waited for 2 minutes, 5 cm * After cutting to 5 cm in size, ion water was added and absorbed to obtain a hydrous gel polymer.

After transferring the hydrogel polymer to a cutter, it was ground at 25 ^° C, 15.8hz conditions. Subsequently, the pulverized hydrogel polymer was dried in a hot air dryer at 180 ^° C. for 40 minutes, and the dried hydrogel polymer was pulverized with a hammer mill grinder. Subsequently, a sieve was used to classify a polymer having a particle size (average particle diameter size) of 150 to 850 m, and a polymer having a particle size (average particle size size) of 300 urn to 600 was classified to prepare a super absorbent polymer. _^ Example 2

 A super absorbent polymer was prepared in the same manner as in Example 1, except that 3.4 g of polyethylene diacrylate (Mw = 280) was added as a crosslinking agent when the mixed aqueous solution was prepared.

Comparative Examples 1 to 3: Preparation of Super Absorbent Polymers

 Comparative Example 1

 Super absorbent polymer was prepared in the same manner as in Example 1, except that 3.2 g of laponite RD and 17.7 g of sodium bicarbonate were not added when the monomer solution was prepared. Compare ^] 2

A superabsorbent polymer was prepared in the same manner as in Example 1, except that 17.7 g of sodium bicarbonate was not added when the monomer solution was prepared. Comparative Example 3

 To 200 g of acrylic acid was added 0.43 g of bis (2, 4, 6-trimethylbenzoyl) -phenyl phosphine oxide [IGARCURE 819] as a photopolymerization initiator and mixed for 5 minutes to prepare a photoinitiator solution.

 Polyethylene glycol diacrylate as crosslinking agent in acrylic acid 164.

5.2 g of [Mi ramer M280] was added and mixed for 5 minutes to prepare a crosslinker solution.

 10.7 g of sodium persulfate, a thermal polymerization initiator, was added to 96.7 g of ionized water and dissolved until completely dissolved in ionized water to prepare an initiator solution.

 Sodium hydrogen carbonate 1.6 g was added to 76.7 g of ionized water as a blowing agent and dissolved until it completely dissolved in ionized water, thereby preparing a blowing agent solution.

 A caustic soda solution was prepared by mixing 120 g of ionized water with 653 g of 32% caustic soda (NaOH).

501 g of acrylic acid was added to a 2L double-jacketed glass reaction vessel flowing ^at 20 ^° C., and 20 g of the photoinitiator solution and 18.3 g of the crosslinker solution were mixed for 5 minutes. Thereafter, the caustic soda solution was added for 10 minutes and neutralized. The temperature was raised to about 65 ^° C by the heat of neutralization, and waited until the ^angle was 42 ^° C, 10.8 g of the thermal initiator solution and 78.3 g of the blowing agent solution was added and mixed for 1 minute to prepare a monomer composition.

In a supply portion of the polymerization reactor made of a conveyor belt to continuously move the said monomer composition, and investigation for 1 minute with ultraviolet rays by a UV irradiation apparatus having a lOmW illumination (dose: ² mW / cm 2) and, after waiting two minutes, 5cm After cutting to 5 cm in size, water was added and absorbed to obtain a hydrous gel polymer.

The hydrogel polymer was transferred to a cutter and then ground at 25 t: 15.8 Hz. Subsequently, the pulverized hydrogel polymer was dried in a hot air dryer at 180 ^° C. for 40 minutes, and the dried hydrogel polymer was pulverized with a hammer mill grinder. Subsequently, a sieve was used to classify a polymer having a particle size (average particle size) of 150 jum to 850 p, and a polymer having a particle size (average particle size) of 300 IM to 600 was classified to prepare a super absorbent polymer. . <Experimental Example: Measurement of Physical Properties of Super Absorbent Polymers Obtained in Examples and Comparative Examples> Physical properties of the superabsorbent polymers prepared in Examples and Comparative Examples were measured by the following methods, and the results are shown in Tables 1 and 2 below. Shown in Experimental Example 1. Centrifugal water retention capacity for physiological saline (CRC, Centr i fuge

Retent ion Capac i ty)

 In accordance with the European Di sposables and Nonwovens Associ at ion (EDANA) standard EDANA WSP 241.2, for the high absorbent resins of the Examples and Comparative Examples, the centrifugal water-retaining capacity (CRC) was measured by the unloaded absorption ratio. The results are shown in Table 1 below.

That is, after the resin W ₀ (g, about 0.2 g) of the above Examples and Comparative Examples was evenly placed in a non-woven bag and sealed, it was added to a physiological saline solution of 0.9 wt. Flooded. After 30 minutes, the bag was centrifuged and drained at 250 G for 3 minutes, and then the mass W ₂ (g) of the bag was measured. Moreover, the mass Wg) at that time was measured after performing the same operation without using resin.

 Using each mass thus obtained, CRC (g / g) was calculated according to the following equation 1 to confirm the water holding capacity.

 [Calculation 1]

CRC (g / g) = {[W ₂ (g)-Wi (g)] / W ₀ (g)}-1

 In the above formula 1,

W ₀ (g) is the initial weight (g) of the superabsorbent polymer,

 Kg) is the weight of the device measured after dehydration at 250G for 3 minutes using a centrifuge without using a super absorbent polymer,

W ₂ (g) is obtained by submerging and absorbing superabsorbent polymer in 0.9 weight physiological saline solution for 30 minutes at room temperature, dehydrating it at 250G for 3 minutes using a centrifuge, and then measuring the weight of the device including superabsorbent polymer. to be. Experimental Example 2. Extractable content (EC)

Superabsorbent polymers of the Examples and Comparative Examples according to EDANA method WSP 270.3 For the content of the water-soluble component was measured, the results are shown in Table 1 below. Experimental Example 3. Absorption rate (Vortex-test)

 In a 100 M beaker, 0.9 wt> of NaCl solution 50 ^ was added, followed by stirring at 600 rpm using a stirrer, and 2.00 g of superabsorbent polymers according to the examples and the comparative example were added, respectively. Then, the time required until the vortex of the liquid generated by stirring disappeared and a smooth surface was measured, and the results are shown in Table 1 below.

Table 1

 Super Absorbent Polymer Composition and Experimental Results of Examples and Comparative Examples

 * phr: Weight ratio measured based on 100 parts by weight of ethylenically unsaturated monomer (acrylic acid) As shown in Table 1, the superabsorbent polymers obtained in Examples 1 to 2 are comparative examples in which neither inorganic particles nor blowing agents were used. It was found that the water absorption rate was significantly reduced to less than 60 seconds while showing the same level of water-retaining ability for the super absorbent polymer obtained in step 1.

In addition, in the case of the super absorbent polymer obtained in Comparative Example 2, which used inorganic particles but did not use a blowing agent, and the super absorbent resin obtained in Comparative Example 3, which used a blowing agent but did not use inorganic particles, the absorption rate was 61 seconds, 75 seconds to show, obtained in Examples 1 to 2 using inorganic particles and blowing agent together It was confirmed that the super absorbent polymer had an improved absorption rate of less than 60 seconds. Accordingly, it was confirmed that the superabsorbent polymer of the example in which the blowing agent was added together with the inorganic particles can realize a remarkably improved absorption rate while maintaining an appropriate level of water retention.

Claims

[Claim]  [Claim 11  A base resin powder comprising a crosslinked polymer of a water-soluble ethylenically unsaturated monomer having at least a portion of neutralized acid groups,  In the base resin powder, a plurality of pores with a diameter of 1 mi or more are formed,  The crosslinked polymer comprises layered silicate particles dispersed in its crosslinked structure,  A superabsorbent polymer having a time of removing vortex generated when stirring at a speed of 600 rpm in 50 m £ of 0.9 wt% NaCl solution for 60 seconds or less. [Claim 2]  The method of claim 1,  A plurality of pores of diameter 1 or more formed in the base resin powder comprises micropores having a diameter of 10 to 100 im, superabsorbent resin. [Claim 3]  According to claim 1,  EDANA Act WSP 241. Superabsorbent polymers with a water retention capacity of 45 g / g or more, measured according to 2. [Claim 4]  The method of claim 1,  The layered silicate-based particles are formed on at least one surface of the metal oxide layer and the metal oxide layer, and includes a unit crystal including a silica layer containing silica. [Claim 5]  The method of claim 1, The layered silicate particles have a maximum diameter of 1 nm to 100 in cross section. nm, height is O. A super absorbent polymer having a light structure of 1 nm to 20 nm. [Claim 6]  The method of claim 1,  The layered silicate-based particles are contained in 0.01 to 5 parts by weight based on 100 parts by weight of the base resin powder. [Claim 7]  The method of claim 1,  The water-soluble ethylenically unsaturated monomer is acrylic acid, methacrylic acid, maleic anhydride, fumaric acid, crotonic acid, itaconic acid, 2-acryloylethane sulfonic acid, 2-methacryloylethanesulfonic acid, 2- (meth) acryloyl Propanesulfonic acid, or anionic monomers of 2— (meth) acrylamide-2-methyl propane sulfonic acid and salts thereof;  (Meth) acrylamide, N-substituted (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, hydroxypolyethylene glycol (meth) acrylate or polyethylene glycol Nonionic hydrophilic-containing monomers of (meth) acrylates; And  Amino group-containing unsaturated monomers of (Ν, Ν) -dimethylaminoethyl (meth) acrylate or (Ν, Ν) -dimethylamino propyl (meth) acrylamide and their quaternized compounds; Superabsorbent polymer comprising one or more selected from the group consisting of. [Claim 8]  The method of claim 1,  The crosslinked polymer is a super absorbent polymer comprising a crosslinked structure in which the polymer chains of the water-soluble ethylenically unsaturated monomer are crosslinked through a crosslinkable functional group of an internal crosslinking agent. [Claim 9]  The method of claim 1, The crosslinked polymer is a plurality of water-soluble ethylenically unsaturated monomers A super absorbent polymer comprising a crosslinked polymer polymerized in the presence of an internal crosslinking agent comprising a polyfunctional acrylate compound having an ethylene oxide group. [Claim 10]  The method according to any one of claims 8 to 9,  The internal crosslinking agent is polyethylene glycol diacrylate (PEGDA), glycerin diacrylate, glycerin triacrylate, unmodified or ethoxylated trimethylol triacrylate (TMPTA), nucleic acid diol diacrylate, and triethylene glycol Superabsorbent polymer comprising at least one member selected from the group consisting of diacrylates. [Claim 11]  Crosslinking and polymerizing a water-soluble ethylene-based unsaturated monomer having at least a part of a neutralized acidic group in the presence of the layered silicate particles, the blowing agent and the internal crosslinking agent to form a hydrogel polymer; And  Drying, pulverizing and classifying the hydrogel polymer to form a base resin powder, a method for producing a super absorbent polymer. [Claim 12]  The method of claim 11,  In the step of forming the hydrogel polymer,  1 part by weight to 1000 parts by weight of the layered silicate particles are used with respect to 100 parts by weight of the blowing agent, a method for producing a super absorbent polymer. [Claim 13]  The method of claim 11,  Forming the hydrogel polymer, Forming a crab solution comprising an internal crosslinking agent and a water-soluble ethylenically unsaturated monomer having at least a portion of neutralized acidic groups; Forming a crab bi-solution comprising layered silicate particles and a blowing agent; And  A method for producing a superabsorbent polymer, comprising the step of crosslinking-polymerizing a monomer composition including the first solution and the second solution. [Claim 14]  The method of claim 13,  Forming a first solution including the internal crosslinking agent and a water-soluble ethylenically unsaturated monomer having at least a part of which is neutralized acidic group,  The content of the said internal crosslinking agent is 0.01 weight part-5 weight part with respect to 100 weight part of water-soluble ethylenically unsaturated monomers, The manufacturing method of the super absorbent polymer. [Claim 15]  The method of claim 13,  In the step of cross-polymerizing the monomer composition containing the first solution and the second solution,  The content of the second solution is 1 part by weight to 100 parts by weight based on 100 parts by weight of the first solution contained in the monomer composition, a method for producing a super absorbent polymer.