WO2016117842A1 - Super-absorbent polymer and method for preparing same - Google Patents

Abstract

The present invention relates to a super-absorbent polymer having excellent properties, both centrifugal retention capacity (CRC) and absorption under pressure (AUP) having been improved by introducing a surface crosslinked layer crosslinked by surface-modified inorganic particles, and to a method for preparing the same. The super-absorbent polymer comprises: a base resin powder containing a crosslinked polymer of water-soluble ethylene-based unsaturated monomers having an at least partially neutralized acidic group; and a surface crosslinked layer formed on the base resin powder, wherein inorganic particles may be chemically bound to the crosslinked polymer contained in the surface crosslinked layer, via an oxygen-containing bond or a nitrogen-containing bond.

Description

 [Name of invention]

 Super Absorbent Resin and Method for Making the Same

 [Cross Citation with Related Application (s)]

 This application claims the benefit of priority based on Korean Patent Application No. 10-2015-0011037 dated January 23, 2015 and Korean Patent Application No. 10-2015-0187758 dated December 28, 2015. All content disclosed in the literature is included as part of this specification.

 Technical Field

 The present invention relates to a superabsorbent polymer having improved water-retaining capacity (CRC), pressure-absorbing capacity (AUP) and water permeability by introducing a surface crosslinked layer crosslinked with surface-modified inorganic particles, and a method for producing the same.

 Background Art

 Super Absorbent Polymer (SAP) is a synthetic polymer material capable of absorbing water of 500 to 1,000 times its own weight. Absorbent Gel Mater ial), they are named differently. Such super absorbent polymers have been put into practical use as sanitary instruments, and are currently used in sanitary products such as paper diapers and sanitary napkins for children, horticultural soil repair agents, civil engineering, building index materials, seedling sheets, and food fresheners. , And widely used as a material for steaming.

 In most cases, these superabsorbent polymers are widely used in the field of sanitary products such as diapers and sanitary napkins. For this purpose, the superabsorbent polymers need to exhibit high absorption of moisture and must not escape moisture absorbed by external pressure. In addition, it is necessary to maintain a good shape even in the state of volume expansion (swelling) by absorbing water to show excellent permeabi li ty.

By the way, it is known that the water retention capacity (CRC), which is a physical property indicating the basic absorption power and water retention capacity of the superabsorbent polymer, and the absorption power under pressure (AUP), which exhibits a property of retaining moisture absorbed well by external pressure, are difficult to improve together. . This is because, when the overall crosslinking density of the superabsorbent polymer is controlled to be low, the water-retaining ability can be relatively high, but the crosslinking structure is coarse and the gel strength is lowered, so that the absorbency under pressure can be reduced. Conversely, by controlling the crosslinking density high When the absorption ability under pressure is improved, moisture is hardly absorbed between the dense crosslinked structures, and the basic water holding ability may be lowered. For the reasons mentioned above, there has been a limitation in providing a super absorbent polymer having both a water-retaining capacity and a water-absorbing capacity under pressure.

 On the other hand, when the superabsorbent polymer is exposed to a high humidity state, a caking phenomenon occurs in which the superabsorbent polymer absorbs moisture in the air and collects into large lumps. In order to prevent such caking phenomenon, inorganic additives such as silica are mixed with the superabsorbent polymer.

 However, it is difficult to effectively disperse the inorganic additives in the superabsorbent polymer, so the effect of the inorganic additives is less than expected, and the separation of the inorganic additives physically blended with the superabsorbent polymer causes problems such as dust generation and physical property changes. .

 [Content of invention]

 [Problem to solve]

 Accordingly, the present invention is to provide a superabsorbent polymer exhibiting excellent physical properties by improving the water-retaining capacity (CRC), pressure-absorbing capacity (AUP) and water permeability by crosslinking the surface with the surface-modified inorganic particles.

 The present invention also provides a method for producing the superabsorbent polymer.

 [Measures of problem]

 The present invention provides a resin composition comprising: a base resin powder comprising a crosslinked polymer in which a water-soluble ethylenically unsaturated monomer having at least a portion of neutralized acidic groups is thickened in the presence of an internal crosslinker; And a surface crosslinking layer in which the crosslinked polymer is further crosslinked in the presence of surface modified inorganic particles, and formed on the base resin powder, wherein the crosslinked polymer included in the surface crosslinking layer contains an oxygen-containing bond or a nitrogen-containing bond. Provided is a superabsorbent polymer in which inorganic particles are chemically bonded through a bond.

In addition, the present invention comprises the steps of cross-polymerizing a water-soluble ethylenically unsaturated monomer having at least a part of the neutralized acidic group in the presence of an internal crosslinking agent to form a hydrogel polymer; Drying, pulverizing and classifying the hydrogel polymer to form a base resin powder; And epoxy, hydroxy, isocyanate and amine groups. In the presence of at least one inorganic particles surface-modified with at least one functional group selected from the group consisting of, providing a method for producing the superabsorbent polymer comprising the step of further crosslinking the surface of the base resin powder to form a surface crosslinking layer.

 Hereinafter, a super absorbent polymer according to a specific embodiment of the present invention and a manufacturing method thereof will be described in detail. However, this is presented as an example of the invention, thereby not limited to the scope of the invention, it is apparent to those skilled in the art that various modifications to the embodiment is possible within the scope of the invention. In addition, unless otherwise indicated throughout the specification, "including" or "containing" refers to the inclusion of any component (or component) without particular limitation, and the addition of another component (or component) It cannot be interpreted as excluding.

 According to one embodiment of the invention, at least a portion of the base resin powder containing a crosslinked polymer polymerized in the presence of an internal crosslinking agent is a water-soluble ethylenically unsaturated monomer having a neutralized acid group; And a surface crosslinking layer in which the crosslinked polymer is further crosslinked in the presence of surface modified inorganic particles, and formed on the base resin powder, wherein the crosslinked polymer included in the surface crosslinking layer includes an oxygen-containing bond or nitrogen Provided is a superabsorbent polymer in which inorganic particles are chemically bonded through a containing bond.

 According to the experiments of the present inventors, when the surface of the base resin powder is further crosslinked in the presence of inorganic particles surface-modified with at least one functional group selected from the group consisting of an epoxy group, a hydroxyl group, an isocyanate group, and an amine group to form a surface crosslinking layer, The inorganic particles are chemically bonded to the crosslinked polymer included in the surface crosslinking layer to prevent the inorganic particles from being separated from the superabsorbent polymer during the manufacturing and transport of the superabsorbent polymer, as well as the pressure absorbing ability and the permeability (permeabi li ty). The invention was completed, confirming that improved superabsorbent polymer) can be prepared and provided.

The superabsorbent polymer thus prepared includes, for example, a base resin powder in which the polymer chains polymerized with the water-soluble ethylenically unsaturated monomer include a crosslinked crosslinked crosslinked through a crosslinkable functional group of an internal crosslinker. Two or more crosslinking polymers per particle Possible functional groups will include a surface crosslinked layer that is further crosslinked with surface-modified inorganic particles.

 Accordingly, the super absorbent polymer of one embodiment has a surface crosslinked layer in which the crosslinked polymers present on the surface are cross-linked through the surface-modified inorganic particles, and the crosslinked polymer and the inorganic particles can crosslink the inorganic particles in the surface crosslinked layer. It has a structure that is chemically linked through an oxygen-containing bond or a nitrogen-containing bond derived from a functional group. More specifically, the crosslinked polymer and the inorganic particles in the surface crosslinking layer are oxygen-containing bonds such as -0- or -coo- or-

It may have a structure chemically linked through a nitrogen-containing bond, such as C0NR- or -NR- (R is hydrogen or an alkyl group having 1 to 3 carbon atoms).

 Due to the surface cross-linking structure comprising such inorganic particles, the superabsorbent resin of one embodiment is basically difficult to form between particles, so that the superabsorbent resin absorbs moisture in the air and aggregates into a large mass. Caking phenomenon can be effectively prevented. In addition, the inorganic particles occupy a certain space between the surface crosslinked structures. For this reason, the superabsorbent polymer exhibits an improved water absorption rate and can maintain excellent shape even in the state of volume expansion (swelling) by absorbing water, thereby exhibiting excellent permeability. In particular, unlike the conventional common knowledge that the water-absorbing capacity and the water-absorbing capacity are inversely related to each other due to the new surface-crosslinked structure described above, the superabsorbent polymers have all excellent properties such as water-retaining capacity and pressure-absorbing capacity. Can be represented. As a result, the super absorbent polymer of one embodiment fundamentally solves the problems of the existing superabsorbent polymers and technical requirements in the art, and may exhibit more excellent physical properties.

 Hereinafter, a structure and a manufacturing method of the super absorbent polymer of one embodiment will be described in more detail.

 The super absorbent polymer of the embodiment basically includes a crosslinked polymer obtained by crosslinking and polymerizing the water-soluble ethylenically unsaturated monomer as a base resin powder, and includes a surface crosslinked layer formed on the base resin powder. .

In addition, the superabsorbent polymer of the embodiment may be crosslinkable as described above in the process for surface crosslinking of the crosslinked polymer and the base resin powder. As the inorganic particles surface-modified with functional groups are used, the inorganic particles are chemically bonded to the polymer chains of the crosslinked polymer in which the inorganic particles are present on the surface of the base resin powder through an oxygen-containing or nitrogen-containing bond derived from the crosslinkable functional group ( For example, a covalent bond or a crosslinking bond) is carried out. Thereby, it is possible to exhibit the overall excellent physical properties as described above (especially at the same time improved water holding capacity and pressure absorption capacity).

 In the super absorbent polymer of this embodiment, the water-soluble ethylenically unsaturated monomer, acrylic acid, methacrylic acid, maleic anhydride, fumaric acid, crotonic acid, itaconic acid, 2-acryloylethanesulfonic acid ᅳ 2-methacryloyl Anionic monomers of ethanesulfonic acid, 2- (meth) acryloylpropanesulfonic acid, or 2- (meth) acrylamide-2-methyl propane sulfonic acid and salts thereof; (Meth) acrylamide, N-substituted (meth) acrylamide, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, methoxypolyethylene glycol (meth) acrylate or polyethylene glycol ( Nonionic hydrophilic-containing monomers of meth) acrylate; And an amino group-containing unsaturated monomer of (Ν, Ν) -dimethylaminoethyl (meth) acrylate or (Ν, Ν) -dimethylaminopropyl (meth) acrylamide and its quaternized product; 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 part of acrylic acid is neutralized may be used. The production of superabsorbent polymers having superior physical properties using such monomers may be used. Becomes possible. When the alkali metal salt of acrylic acid is used as a monomer, acrylic acid may be neutralized with a basic compound such as caustic soda (NaOH). In this case, the degree of neutralization of the water-soluble ethylenically unsaturated monomer may be adjusted to about 50 to 95% or about 70 to 85%, and can provide a super absorbent polymer having excellent water retention capability without fear of precipitation during neutralization within this range. have.

In addition, as the internal crosslinking agent for introducing the 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 for the production of superabsorbent polymers, can be used without particular limitation. However, in order to introduce an appropriate crosslinked structure into the crosslinked polymer and the base resin powder to further improve the physical properties of the super absorbent polymer, a plurality of ethylene oxide groups may be used. The polyfunctional acrylate compound having can be used as the internal crosslinking agent. More specific examples of such internal crosslinking agents include polyethylene glycol diacrylate (PEGDA), glycerin diacrylate, glycerin triacrylate, unmodified or ethylated trimethylolpropane triacrylate (TMPTA), nucleic acid didi diacrylate, And triethyleneglycol diacrylate.

 In addition, in the superabsorbent polymer of the above-described embodiment, the surface-modified inorganic particles for forming the surface crosslinked layer formed on the base resin powder may use inorganic particles surface-modified with the above-mentioned crosslinkable functional groups.

The inorganic particles may have a specific surface area of 5 to 600 m ² / g or 100 to 300 m ² / g. Within this range the inorganic particles may be surface modified with an appropriate number of crosslinkable functional groups. And, the inorganic particles have a diameter of 5 to 500nm, it is economical because the inorganic particles of the appropriate number of particles compared to the same weight can be well dispersed in the surface crosslinking layer.

 More specifically, such inorganic particles may be used, such as silica particles or alumina particles.

 In addition, the above-described inorganic particles may be bonded to about 0.01 to 2 parts by weight based on 100 parts by weight of the super absorbent polymer. As a result, a crosslinked structure including an appropriate amount of inorganic particles may be introduced into the surface crosslinking layer, so that the superabsorbent polymer of one embodiment may have more improved physical properties, for example, water retention and absorption under pressure. On the other hand, regarding the more specific kind of the above-mentioned surface-modified inorganic particles, a manufacturing method thereof, and the like, reference may be made to the contents described in the manufacturing method described later.

In the superabsorbent polymer of the above embodiment, the surface crosslinked layer formed on the base resin powder may be formed using a surface crosslinking agent that has been used in the conventional production of superabsorbent polymer together with the surface modified inorganic particles. As the surface crosslinking agent, all known in the art may be used without any particular limitation. More specific examples thereof include ethylene glycol, 1,4-butanediol, 1,6-nucleic acid dipropylene, propylene glycol, 1,2-nucleic acid diol, 1,3-nucleic acid diol, 2-methyl ᅳ 1, 3-propanediol, 2,5-nucleic acid diol, 2 핵산 methyl-1, 3-pentanediol, 2-methyl-2,4-pentanedi, tripropylene glycol, glycerol, ethylene carbonate and propylene carbonate 1 or more types are mentioned.

 In addition, the superabsorbent polymer of the above-described embodiment has a centrifugal water retention capacity (CRC) of about 30 to 40 g / g for physiological saline, and a pressure absorption capacity (AUP) of 0.7 psi to physiological saline about 10 to 26. g / g or about 20 to 26 g / g, and a free swelling gel bet permeability (GBP; gel bed permeabi 1ity) may be about 5 to 120 darcy or about 9 to 120 darcy.

 As the superabsorbent polymer of the above-described embodiment is introduced with a surface crosslinked structure including inorganic particles in the surface crosslinked worm, the superabsorbent polymer may exhibit excellent water-retaining ability with improved penetration and pressure-absorbing ability. Therefore, such a super absorbent polymer may be preferably applied to various sanitary articles such as diapers, and may exhibit very excellent physical properties as a whole.

 On the other hand, the centrifugal water retention capacity (CRC) for the physiological saline can be measured according to the method of the EDANA method WSP 241.2. More specifically, the water retention capacity can be calculated by the following formula 1 after absorbing the super absorbent polymer in physiological saline over 30 minutes:

 [Calculation 1]

 CRC (g / g) = {[W2 (g) ― Wl (g)] / W0 (g)}-1

 In the above formula 1,

 W0 (g) is the initial weight (g) of the superabsorbent polymer, and Wl (g) is the bag measured after immersing an empty bag in physiological saline for 30 minutes at room temperature and then dehydrating it at 250 G for 3 minutes using a centrifuge. W2 (g) is the weight of the bag containing the superabsorbent polymer, measured after immersing the bag containing superabsorbent polymer at room temperature in physiological saline for 30 minutes and then dehydrating it for 3 minutes at 250 G using a centrifuge. .

 In addition, the pressure absorption capacity (AUP) of 0.7 psi can be measured according to the method of the EDANA method WSP 242.2. More specifically, the pressure-absorbing capacity may be calculated according to the following formula 2 after absorbing the superabsorbent polymer in physiological saline under a pressure of about 0.7 ps i over 1 hour:

 [Calculation 2]

 AUP (g / g) = [W4 (g)-W3 (g)] / W0 (g)

In the formula 2, W0 ( _g ) is the initial weight (g) of the superabsorbent polymer, W3 (g) is the sum of the weight of the superabsorbent polymer and the weight of the device that can be applied to the superabsorbent polymer, and W4 (g) is the load After absorbing physiological saline to the superabsorbent resin for 1 hour under (0.7 psi), the sum of the weight of the superabsorbent resin and the weight of the device capable of applying a load to the superabsorbent resin.

 W0 (g) described in Formulas 1 to 2 corresponds to an initial weight (g) before the superabsorbent polymer is absorbed into physiological saline, and may be the same or different.

The gel bed permeability (GBP) for physiological saline can be measured in units of Darcy or cm ² according to the following method described in Patent Application No. 2014-7018005. Ldarcy means that a liquid with a viscosity of lcP flows through 1 _cm ² per ^second under a pressure gradient of 1 atmosphere per _cm . Gel bed permeability has the same units as area ldarcy are as 0.98692 x 10 ^{~ 12} m ² or 0.98692 X 10- ⁸ cm ^2.

 More specifically, GBP herein refers to the penetration (or permeability) of the gel layer (or bed) swelled under a condition called free swelling of 0 ps i (Gel Bed Permeabi li ty (GBP) Under Opsi Swel l Pressure Test), and the GBP may be measured using the apparatus shown in FIGS. 1 to 3.

1-3, the test device assembly 528 in the apparatus 500 for measuring GBP includes a sample container 530 and a plunger 536. The plunger includes a shaft 538 having a cylinder hole drilled down the longitudinal axis and a head 550 located at the bottom of the shaft. The diameter of the shaft hole 562 is about 16 mm. The plunger head is attached to the shaft by an adhesive, for example. Twelve holes 544 are drilled in the radial axis of the shaft, and the diameter of three holes located every 90 ^° is about 6.4 mm. The shaft 538 is machined from a LEXAN rod or equivalent material and has an outer diameter of about 2.2 cm and an inner diameter of about 16 mm 3. Plunger head 550 has seven inner holes 560 and fourteen outer holes 554, all of which are about 8.8 mm in diameter. In addition, a hole of about 16 mm is aligned with the shaft. The plunger head 550 is machined from a LEXAN rod or equivalent material, is about 16 mm high, and has a diameter that fits inside the cylinder 534 with a minimum wall gap (wal lc learance) but still It's sized to move freely. The total length of the plunger head 550 and shaft 538 is about 8.25 cm, but can be machined at the top of the shaft to obtain the desired size of the plunger 536. The plunger 536 is biaxially stretched and includes a 100 mesh stainless steel cloth screen 564 attached to the bottom of the plunger 536. Attach the screen to the plunger head 550 using a suitable solvent that will securely attach the screen to the plunger head 550. Care must be taken to avoid excess solvent moving into the openings of the screen, reducing the pore area for liquid flow. Acrylic solvent Weld-on 4 from IPS Corporat ion (place of business, Gardena, California, USA) may suitably be used. The sample vessel 530 includes a cylinder 534 and a 400 mesh stainless steel cloth screen 566 which is biaxially stretched and taut and attached to the bottom of the cylinder 534. The screen is attached to the cylinder using a suitable solvent to securely adhere to the cylinder. Care must be taken to avoid excess solvent moving into the openings of the screen, reducing the pore area for liquid flow. Acrylic solvent Weld-on 4 from IPS Corporat ion (place of business, Gardena, California, USA) may suitably be used. The gel particle sample (swelled superabsorbent resin), indicated at 568 in FIG. 2, was supported on the screen 566 inside the cylinder 534 during the test.

The cylinder 534 may be drilled in a transparent LEXAN rod or even material, or cut into a LEXAN tubing or even material, having an inner diameter of about 6 cm (e.g., about 28.27 cm ^{2 in} cross-section) and a wall thickness. About 0.5 cm, about 7.95 cm high. The step may be formed by machining the outer diameter of the cylinder 534 such that the portion 534a having an outer diameter of 66 mm is present at the bottom 31 mm of the cylinder 534. An o-ring 540 may be placed at the top of the step to match the diameter of the region 534a.

The annul ar weight 548 has counter-bored holes of about 2.2 cm in diameter and 1.3 cm in depth, so it freely slides onto the shaft 538. The annular weight also has a thru-bore 548a of about 16 mm 3. The annular weight 548 can be made of stainless steel or other suitable material that can resist corrosion by 0.9 weight percent physiological saline (aqueous sodium chloride solution). The combined increase of the plunger 536 and the annular weight 548 is equal to about 596 g, which means that the pressure applied to the sample 568 is about 0.3 psi or over a sample area of about 28.27 cm ² . Corresponds to about 20.7 dyne / cm ² (2.07 kPa).

 As the test solution flows through the test apparatus during testing of the GBP, the sample vessel 530 is generally placed on a weir 600. The purpose of the weir is to divert the overflowing liquid at the top of the sample vessel 530, and the overflow liquid is diverted to a separate collection device 601. The weir may be placed on the balance 602 in which the beaker 603 is placed to collect physiological saline passing through the swollen sample 568.

 In order to perform the gel bed permeability test under “free swelling” conditions, a plunger 536 equipped with a weight 548 is placed in an empty sample vessel 530 and a weight of 548 up to 0.01 mm with a suitable gauge. The height from the top of the c) to the bottom of the sample vessel 530 is measured. The force exerted by the thickness gauge during the measurement should be as small as possible, preferably less than about 0.74 N. When using a multiple test apparatus, it is important to maintain each empty sample container 530, plunger 536 and weight 548 and the tracks in which they are used.

Also, the base on which the sample container 530 is placed is flat, and the surface of the weight 548 is preferably parallel to the bottom surface of the sample container 530. Then, prepare a sample to be tested from the super absorbent polymer to measure GBP. In one example, a test sample is prepared from a superabsorbent resin having a particle size of about 300 to about 600 m that passes through a US standard 30 mesh screen and is maintained on a US standard 50 mesh screen. About 2.0 g of sample is placed in sample vessel 530 and evenly spread over the bottom of the sample vessel. Subsequently, the vessel containing 2.0 g of sample without the puller 536 and weight 548 was immersed in 0.9 weight percent physiological saline for about 60 minutes to allow the sample to swell under pressure. At this time, the sample vessel ₅₃₀ is placed on a mesh located in the liquid reservoir so that the sample vessel 530 is slightly above the bottom of the liquid reservoir. The mesh may be one that does not affect the movement of physiological saline to the sample container 530. Such mesh may be part number 7308 from Eagle Supply and Pl ast ic, Appleton, Wisconsin, USA. The height of physiological saline during saturation can be adjusted such that the surface in the sample container is defined by the sample, not physiological saline.

At the end of this period, the assembly of the plunger 536 and the weight 548 is removed from the sample container 530. The sample container 530, the plunger 536, the weight 548 and the sample 568 are removed from the solution after resting on the saturated sample 568 in the chamber. The sample vessel 530, plunger 536, weight 548 and sample 568 are then left on a flat, large grid, uniform thickness, non-deformation plate for about 30 seconds, prior to GBP measurements. The plate will prevent liquid in the sample vessel from releasing onto a flat surface due to surface tension. This plate has a total dimension of 7.6 cm x 7.6 cm and each grid dimension may be 1.59 cm long by 1.59 cm wide by 1.12 cm deep. A suitable plate material is a parabolic diffuser, catalog number 1624K27, available from McMaster Carr Sup ly Company (place of business, Chicago, Illinois, USA), which can be cut to suitable dimensions and used.

 Then, if the zero point has not changed from the initial height measurement, the height from the top of the weight 548 to the bottom of the sample vessel 530 is measured again using the same thickness gauge as previously used. Height measurements should be made as soon as possible after the thickness gauge is fitted. The height measurement of the empty assembly with the plunger 536 and weight 548 positioned in the empty sample container 530 should be subtracted from the height measurement obtained after saturating the sample 568. The resulting value is the thickness or height 'Ή' of the saturated sample 568. Also, if a plate is included in the assembly comprising the saturated sample 568, the plate is also included in the height measurement of the empty assembly. The height shall be measured.

The GBP measurement begins with delivering 0.9% physiological saline into the sample vessel 530 containing the saturated sample 568, plunger 536 and weight 548. Adjust the f low rate of physiological saline into the vessel so that the physiological saline overflows to the top of the cylinder 534, thereby resulting in a consistent head pressure equivalent to the height of the sample vessel 530. Physiological saline can be added by any means sufficient to ensure a small but consistent amount of overflow from the top of the cylinder with instrument pump 604 or the like. The overflow liquid is diverted into a separate collection device 601. Using a balance 602 and beaker 603, the amount versus time of solution passing through sample 568 is measured gravimetrically. Once the overflow begins, data points are collected from the balance 602 every second for at least 60 seconds. Data collection can be obtained manually or using data collection software. The flow rate Q through the swollen sample 568 is in g / sec by the linear least-square fit of liquid (g) versus time (sec) passing through the sample 568. Decide on

Using the data thus obtained, the GBP (cm ² ) can be calculated according to the following Equation 3 to confirm the gel bed transmittance.

 [Calculation 3]

 K = [Q * H * μ] / [Α * ρ * Ρ]

 In the above formula 3,

Κ is the gel bed transmission (cm ² ) ，

 Q is the flow rate (g / sec),

 H is the height (cm) of the swollen sample,

 y is the liquid viscosity (P) (the viscosity of the test solution used in this test is about lcP),

 A is the cross-sectional area for the liquid flow (28.27 ciif for the sample vessel used in this test),

p is the liquid density (g / cm ³ ) (about 1 g / cm ^{3 for} the test solution used in this test),

P is the hydrostatic pressure (dyne / cm ²⁾ (normally approximately 7, 797dyne / cm ^2).

The hydrostatic pressure is calculated from the equation P = p * g * h, where p is the liquid density (g / cm ³ ), g is the acceleration of gravity (nominally 981 cm / sec ² ), and h is the liquid height (e.g. For example, for the GBP test described herein, 7.95 cm).

 The superabsorbent polymer of the above-described embodiment may have a particle shape such as spherical or amorphous having a particle diameter of about 150 to 850.

On the other hand, according to another embodiment of the invention, there is provided a manufacturing method of the super absorbent polymer described above. A method for preparing such a super absorbent polymer may include crosslinking and polymerizing a water-soluble ethylenically unsaturated monomer having at least a portion of neutralized acidic groups in the presence of an internal crosslinking agent to form a hydrogel polymer; Drying, pulverizing and classifying the hydrogel polymer to form a base resin powder; And in the presence of inorganic particles surface-modified with at least one functional group selected from the group consisting of an epoxy group, a hydroxyl group, an isocyanate group and an amine group, Further crosslinking the surface to form a surface crosslinking layer.

 In the manufacturing method of this other embodiment, according to the general manufacturing method of the super absorbent polymer, the crosslinking polymerization of the water-soluble ethylenically unsaturated monomer in the presence of an internal crosslinking agent, and dried, pulverized and classified to form a base resin powder, Unlike the conventional, the superabsorbent polymer may be prepared by further crosslinking the surface of the base resin powder using inorganic particles that are surface-modified with a crosslinkable functional group such as an epoxy group, a hydroxyl group, an isocyanate group, or an amine group.

 That is, in the manufacturing method of this other embodiment, except that the surface-modified inorganic particles are used in the surface crosslinking, it is possible to follow the conventional manufacturing method of the superabsorbent polymer, hereinafter the surface-modified inorganic particles first And after specifically salping about the manufacturing method thereof, it will be briefly examined for each step for the manufacturing method of the super absorbent polymer using the same.

 The surface modified inorganic particles may be prepared by reacting a surface modifier having the crosslinkable functional group with inorganic particles such as silica particles or alumina particles. In this case, specific examples of the surface modifier may include a compound represented by Formula 1 below.

[Formula 1]

In Formula 1, R _i to are each independently an alkyl group of 1 to 10 carbon atoms, an alkoxy group or halogen of 1 to 10 carbon atoms, at least one of which is not an alkyl group, 4 is an epoxy group, a hydroxyl group, an isocyanate group and an amine group And a substituent having 2 to 10 carbon atoms having at least one functional group selected from the group consisting of.

In the surface-modified inorganic particles, about 2 to 200, or about 10 to 150, or about 20 to 100 crosslinkable functional groups are introduced based on one of the inorganic particles, and thus surface modified. An appropriate crosslinked structure may be introduced into the super absorbent polymer finally prepared by the above manufacturing method. In consideration of the appropriate number of crosslinkable functional groups introduced per each inorganic particle, the surface-modified inorganic particles may be prepared by reacting the inorganic particles and the surface modifier with an appropriate content ratio.

In a more specific example, as the inorganic particles, silica particles such as fumed silica or colloidal silica may be representatively used. In the case of the humed silica, the surface may be modified due to the crosslinkable functional groups at a ratio of about 0.008 to 0.8 umol / m ² , or about 0.04 to 0.4 umol / m ² , based on 1 m ² of the surface area of the silica particles. The inorganic particles and the surface modifiers can be reacted to make them. On the other hand, in the case of the colloidal silica, the surface-modified due to the crosslinkable functional group at a ratio of about 0.014 to 1.4 umol / m ² , or about 0.07 to 0.7 umol / m ² based on the surface area of the silica particles 1 m ² The inorganic particles and the surface modifier may be reacted to make it possible.

 On the other hand, in the method of preparing a super absorbent polymer of another embodiment, first, in the presence of an internal crosslinking agent, at least part of the water-soluble ethylenically unsaturated monomer having a neutralized acidic group may be cross-polymerized to form a hydrogel polymer.

 At 1 °, since the internal crosslinking agent and the type and structure of the water-soluble ethylenically unsaturated monomer are as described above, further description thereof will be omitted.

 In addition, in the monomer composition including the water-soluble ethylenically unsaturated monomer and the internal crosslinking agent, the concentration of the water-soluble ethylenically unsaturated monomer is about 20 to about 60% by weight relative to the total monomer composition including each of the above-described raw materials and solvents, The black may be about 40 to about 50% by weight, and may be in an appropriate concentration in consideration of polymerization time and reaction conditions. However, when 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, when the concentration is too high, a part of the monomer may precipitate or the grinding efficiency of the polymerized hydrogel polymer may be low. Etc. may cause problems in the process and may decrease the physical properties of the super absorbent polymer.

 In addition, the monomer composition may further include a polymerization initiator generally used in the preparation of a super absorbent polymer.

Specifically, the polymerization initiator may be a thermal polymerization initiator or The photoinitiator according to uv irradiation can be used. However, even with the photopolymerization method, since a certain amount of heat is generated by irradiation of ultraviolet radiation 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 further include a thermal polymerization initiator.

 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.

Examples of the photopolymerization initiator include benzoin ether, dialkyl acetophenone, hydroxyl alkylketone, phenyl glyoxylate, and benzyl dimethyl ketal. Ketal), acyl phosphine and alpha-aminoketone can be used at least one selected from the group consisting of. Among these, acylphosphine may be used as the photopolymerization initiator, and diphenyl (2,4,6_trimethylbenzoyl) phosphine oxide and phenylbis (2,4,6-trimethylbenzoyl) force may be used as the acylphosphine. Fin oxide, ethyl (2,4, 6-trimethylbenzoyl) phenylphosphineate and the like can be used. For more photoinitiators, see Reinhold Schwalm, author ^{. "UV Coatings' - Basics, Recent} Developments and New Application (Elsevier 2007 years)" are well stated in the pll5, but are not limited to the above example.

 The photopolymerization initiator may be included in a concentration of about 0.001 to about 1.0 wt% 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 (Na ₂ ¾0 ₈ ), potassium persulfate ( ₂ S ₂ 0 ₈ ), ammonium persulfate (NH ₄ ) ₂ S ₂ 0 ₈ ), and examples of azo initiators include 2,2-azobis- (2-amidinopropane) dihydrochloride (2,2-320 ^ 3 (2-amidinopropane) di hydrochloride), 2 , 2-1-azobis- (1 dimethylene) isobutyramidine dihydrochloride

lS dimethylene) isobutyramidine dihydrochlor ide), 2-

(Carbamoylazo) isobutyronitrile (2- (carbamoylazo) isobutylonitril), 2,2- azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride (2, 2-azobis [ 2- (2-imidazolin-2-yl) propane] dihydrochlor ide), 4,4— ^ό 1 · ^zobis一 (4—shi ⁰ ], ^novaleric acid) (4，4 ᅳ & 20 3- (4- 0 3! 10 3161 ^" ^ acid)), etc. For more various thermal polymerization initiators, the Odian book 'Principle of Polymerization (Wi ley, 1981)', p203, is well defined 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. When the concentration of the thermal polymerization initiator is too low, additional thermal polymerization hardly occurs, and the effect of the addition of the thermal polymerization initiator may be insignificant. When the concentration of the thermal polymerization initiator is too high, the molecular weight of the superabsorbent polymer is low, and The higher the ratio, the lower the pressure-absorbing capacity of the final superabsorbent polymer product.

 In addition, the type of the internal crosslinking agent included in the monomer composition is the same as described above, and the internal crosslinking agent is included at a concentration of about 0.01 to about 0.5% by weight relative to the monomer composition to crosslink the polymerized polymer. Can be. In particular, since such an internal crosslinking agent is used in an amount of about 0.3 parts by weight or more, and about 0.3 to 0.6 parts by weight with respect to 100 parts by weight of the aforementioned monomer, for example, unneutralized acrylic acid, the physical properties of the above-described embodiments are Superabsorbent resins that more suitably meet can be produced.

 In addition, the monomer composition may further include additives such as thickeners, plasticizers, storage stabilizers, antioxidants, and the like, as necessary.

 Raw materials such as the above-mentioned water-soluble ethylenically unsaturated monomers, photopolymerization initiators, thermal polymerization initiators, internal crosslinking agents and additives may be prepared in the form of a monomer composition solution dissolved in a solvent.

The solvent that can be used at this time can be used without limitation in the composition as long as it can dissolve the above-mentioned components, for example, water, ethane, ethylene glycol, diethylene glycol, triethylene glycol, 1,4-butane Diul, propylene glycol, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, methyl ethyl ketone, acetone, methyl amyl ketone, 1 type selected from cyclonucleanone, cyclopentanone, diethylene glycol monomethyl ether, diethylene glycol ethyl ether, toluene xylene, butyrolactone, carbyl, methyl cellosolve acetate, and Ν, Ν-dimethylacetamide The above can be used in combination.

 The solvent may be included in the remaining amount except for the above-described components with respect to the total content of the monomer composition.

 On the other hand, if the method of forming a hydrogel polymer by thermally polymerizing or photopolymerizing such a monomer composition is also the polymerization method normally used, there will be no restriction | limiting in particular in a structure.

 Specifically, the polymerization method is largely divided into thermal polymerization and photopolymerization according to the polymerization energy source, and when the thermal polymerization is usually carried out, it can be carried out in a semi-unggi with a stirring shaft such as kneader, when the photopolymerization, Although it can be carried out in a semi-unggi equipped 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, as described above, the monomer composition may be thermally polymerized by supplying hot air to a reaction device such as a kneader having a stirring shaft or by heating the reaction device. Thus, the hydrogel polymer obtained by thermal polymerization is discharged to the outlet of the reaction vessel, and may have a size of several centimeters to several millimeters depending on the shape of the stirring shaft provided in the reaction vessel. 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, it is usually the weight average _. A hydrogel polymer having a particle diameter of about 2 to 50 mm can be obtained.

In addition, when the photopolymerization is carried out in a semi-unggi equipped with 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 to about 5 cm can be obtained. In the case of supplying the monomer composition to such an extent that the thickness of the polymer on the sheet is too thin, the production efficiency is low, which is not preferable, and when the thickness of the polymer on the sheet exceeds 5 cm, due to the excessively thick thickness, The polymerization reaction may not occur evenly over the entire thickness.

 The light source that can be used in the photopolymerization method is not particularly limited, and as a non-limiting example, a light source such as an Xe lamp, a mercury lamp, or a metal halide lamp may be used.

 On the other hand, the monomer composition may be thermally polymerized after photopolymerization. In this case, a movable conveyor belt, an ultraviolet light source, and a semi-unggi capable of supplying hot air may be used, and the photopolymerization and thermal polymerization methods may be sequentially performed.

Typical water content of the hydrogel polymer obtained in this manner may be about 40 to about 80 weight ¾>. On the other hand, throughout the present specification "water content"'is the amount of water to the total weight of the hydrogel gel polymer means the weight of the hydrogel polymer minus the weight of the dry polymer. It is defined as a value calculated by measuring the weight loss according to the water evaporation in the polymer during drying by drying the temperature of the polymer, wherein the drying condition is raised to about 180 ^° C at room temperature and then maintained at 180 ^° C. In this way, the total drying time is set to 20 minutes, including 5 minutes of silver rising step, and the moisture content is measured.

 After the crosslinking polymerization of the monomer, it is possible to obtain a base resin powder through a process such as drying, pulverization and classification. Through such a process as pulverization and classification, the base resin powder and the super absorbent polymer obtained therefrom Suitably manufactured and provided with a particle size of about 150 to 850. More specifically, at least about 95% by weight or more of the base resin powder and the superabsorbent polymer obtained therefrom will have a particle size of about 150 to 850 / ΛΠ, and the fine powder having a particle size of less than about 150 will be less than about 3 weight ¾. Can be.

 As the particle size distribution of the base resin powder and the super absorbent polymer is adjusted to a preferred range, the superabsorbent resin thus prepared may exhibit the above-described physical properties and better water 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, coarsely pulverizing before drying to increase the efficiency of the drying step, if necessary.

At this time, the grinder used is not limited in configuration, specifically, the vertical type Vertical pulverizer, Turbo cutter, Turbo grinder, Rotary cutter mill, Cutter mill, Disc mill, Piece shredder ( It may include any one selected from the group of crushing devices consisting of a shred crusher, a crusher, a chopper, and a disc cutter, but is not limited thereto.

 At this time, the coarse grinding step may be pulverized so that the particle size of the hydrogel polymer is about 2 to about 10 내지.

 Grinding to a particle diameter of less than 2 GPa is technically not easy due to the high water content of the hydrogel polymer, and may also cause a phenomenon in which the milled particles cross each other. On the other hand, when the particle size is more than 10 mm 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 100 to about 250 ^° C.

If the drying temperature is less than about 100 ^° 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 ^' C, only the polymer surface may be excessively dried. Fine powder may generate | occur | produce in a subsequent grinding | pulverization process, and there exists a possibility that the physical property of the superabsorbent polymer formed finally may fall.

 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 moisture content of the polymer after such a drying step is about

0.1 to about 10 weight ¾>.

 Next, a step of pulverizing the dried polymer obtained through such a drying step is performed.

The polymer powder obtained after the grinding step may have a particle diameter of about 150 to about 850 mm 3. Mills used to grind to such particle diameters are specifically pin mills, hammer mills, screw mills, mills, disc mills or jogs. A jog mill or the like may be used. It is not limited to the example.

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

 On the other hand, after the above-described process of forming the base resin powder, in the presence of the surface-modified inorganic particles described above, the surface of the base resin powder can be further crosslinked to form a surface crosslinking layer, thereby superabsorbent resin Can be prepared.

 At this time, the type and structure of the surface-modified inorganic particles, as described above, as described above, further description thereof will be omitted.

 The surface-modified inorganic particles may be used in an amount of 0.01 to 10 parts by weight, 0.01 to 5 parts by weight, or 0.01 to 3 parts by weight based on 100 parts by weight of the base resin powder. Within this range, it is possible to produce a super absorbent polymer having excellent water holding capacity and pressure absorbing ability, and having improved permeability.

 In addition, for proper surface crosslinking density of the surface crosslinking layer, it is possible to use a surface crosslinking agent that has been used for surface crosslinking of superabsorbent polymers with surface-modified inorganic particles. The type of the surface crosslinking agent has already been described above, and thus, further description thereof will be omitted.

 In addition, in the surface crosslinking process, as the surface crosslinking is performed by adding a polyvalent metal cation together with the surface modified inorganic particles, the surface crosslinking structure of the superabsorbent polymer may be further optimized. This is expected because this metal cation can further reduce the crosslinking distance by forming a chelate with the carboxyl group (C00H) of the superabsorbent resin.

Moreover, the structure is not limited about the method of adding the said surface modified inorganic particle to a base resin powder. For example, the surface-modified inorganic particles and the base resin powder may be mixed in a semi-aperture, or may be surface-modified on the base resin powder. A method of spraying inorganic particles, a method of continuously supplying and mixing a base resin powder and surface modified inorganic particles to a mixer that is continuously operated, and the like can be used.

 Upon addition of the surface modified inorganic particles, water and methanol may be additionally mixed together. The addition of water and methanol has the advantage that the surface modified inorganic particles can be evenly dispersed in the base resin powder. In this case, the added water and the content of methane may be appropriately adjusted to induce even dispersion of the surface-modified inorganic particles and to prevent aggregation of the base resin powder and to optimize the surface penetration depth of the inorganic particles.

When the surface-modified inorganic particles are added to the base resin powder, they may be heated at about 100 ^° C. to 200 ^° C. for about 1 minute to 120 minutes to perform surface crosslinking reaction. More specifically, the surface crosslinking reaction may be performed for about 1 minute to 120 minutes, about 5 minutes to 100 minutes, or about 10 minutes to 80 minutes after reaching the target temperature for the reaction. If the crosslinking reaction time is too short than the above-mentioned range, a sufficient degree of crosslinking reaction may not occur. If the crosslinking reaction time is too long, the physical properties of the superabsorbent polymer may be deteriorated due to excessive surface crosslinking reaction. Prolonged residence in the reaction period can lead to polymer crushing.

 The temperature raising means for surface crosslinking reaction is not specifically limited. It can be heated by supplying a heat medium or by directly supplying a heat source. In this case, as the type of heat medium that can be used, a heated fluid such as steam, hot air, and hot oil may be used, but the present invention is not limited thereto, and the temperature of the heat medium to be supplied may be a means of heating medium, a rate of temperature increase, and a target temperature for heating. Consideration can be made as appropriate. On the other hand, the heat source directly supplied may be a heating method through electricity, a gas heating method, but is not limited to the above examples.

 The superabsorbent polymer obtained according to the above-described manufacturing method may exhibit very excellent properties with improved physical properties such as water retention capacity and pressure absorption capacity, and may exhibit excellent general properties that can be suitably used for hygiene products such as diapers.

 【Effects of the Invention】

According to the present invention, the water holding capacity and the pressure absorbing capacity are inversely related to each other. Unlike conventional common sense, a super absorbent polymer and a method for producing the same may be provided in which all physical properties such as water-retaining capacity and pressure-absorbing capacity are improved together to exhibit excellent properties.

 The superabsorbent polymer of the present invention fundamentally solves the problems of the existing superabsorbent polymers and the technical demands of the art, and may exhibit more excellent physical properties, and can be very preferably applied to various sanitary products. [Brief Description of Drawings]

Figure 1 to Figure ^'3 is a schematic view of the components included in the exemplary device and the device for measuring the gel layer chimtudo.

 [Specific contents to carry out invention]

 Hereinafter, preferred examples are provided to help understanding of the present invention, but the following examples are merely to illustrate the present invention, and the scope of the present invention is not limited to the following examples. Preparation Example 1 Preparation of Surface-Modified Inorganic Particles (Epoxy Group Introduction)

100 g of solution was prepared by dispersing Aerosil 200 (Evonik) in water at 5% by weight. Subsequently, 1 mL of acetic acid was added to the solution to adjust the pH to 3, followed by 2 g of (3- (glycidyloxy) propyl) trimethoxysilane. Then, 70 g of 1 腿 bead (Zr0 ₂ ) was added to the resulting solution, followed by mixing for about 24 hours to modify the surface of the inorganic particles. Thereafter, the obtained product was washed with n-butyl acetate to obtain surface-modified inorganic particles. Preparation Example 2 Preparation of Surface-Modified Inorganic Particles (Epoxy Group Introduction)

200 g of IPA (iso-propyl alcohol) and 12 g of (3- (glycidyloxy) propyl) trimethoxysilane were added to 100 g of Ludox HSA (silica content 30 wt%). Then, 70 g of 1 醒 bead (Zr0 ₂ ) was added to the resulting solution, followed by mixing for about 24 hours to modify the surface of the inorganic particles. Thereafter, the obtained product was washed with n-butyl acetate to obtain surface-modified inorganic particles.

(Ludox HSA is a Colloidal Silica with a particle size of 12 nm and has a specific surface area of 215 m ² / g.) Example 1 Preparation of Super Absorbent Polymer

100 g of acrylic acid, 38.9 g of caustic soda (NaOH), and 103.9 g of water are mixed, and diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide 0.01 g sodium persulfate, which is a thermal polymerization initiator, is mixed with the mixture. The monomer composition was prepared by adding 18 _g and 0.35 g of polyethyleneglycol diacrylate as an internal crosslinking agent. The temperature of the monomer composition was maintained at 40 ^° C. using a thermostat.

On the other hand, the monomer composition to photopolymerization and thermal polymerization, and is provided with a mercury lamp, located on a _second rotary axis silicone belt and the belt, and then ultraviolet radiation was used as an apparatus which can supply hot air to the heat-insulating space.

The temperature-controlled monomer composition in the thermostat was injected into the belt of the device, and the monomer composition placed on the belt was irradiated with ultraviolet light for 60 seconds at an intensity of 10 mW through a mercury lamp located above the belt. After ultraviolet irradiation, hot air was supplied to the photopolymerized polymer to maintain the temperature at 90 ^° C. to conduct a thermal polymerization reaction. Then, the hydrogel polymer discharged through the cutter was dried in a hot air dryer at 180 ^° C for 1 hour.

 The dried hydrogel polymer was pulverized with a pin mill grinder. Then, sieve was used to classify the polymer having a particle size of less than about 150 rn and the polymer having a particle size of about 150 to 850 mm 3.

 Thereafter, the surface treatment solution was sprayed containing 1.0 part by weight of 1, 3-propanedi, 1 part by weight of water and 0.01 part by weight of the surface-modified inorganic particles prepared in Preparation Example 1, based on 100 parts by weight of the prepared base resin powder. The mixture was stirred at room temperature and mixed to uniformly distribute the surface crosslinking agent and the surface treatment solution in the base resin powder.

Subsequently, the mixture was placed in a surface crosslinking reactor set at about 180 ^° C., and the surface crosslinking reaction was performed. Within this surface crosslinking reaction vessel, the base resin powder was found to gradually increase in temperature at an initial temperature near about 160 ^° C., and after about 30 minutes, the maximum reaction temperature of about 180 ^° C. was reached. After reaching this maximum reaction temperature, a further reaction was performed for about 20 minutes before the final prepared superabsorbent polymer sample was taken. After the surface crosslinking process, a surface crosslinked superabsorbent polymer having a particle size of about 150 to 850 / m was obtained using sieve. The content of fine powder having a particle diameter of about 150 μα or less contained in the superabsorbent polymer was less than about 2 wt% ¾. Example 2: Preparation of Super Absorbent Polymer

A superabsorbent polymer was prepared in the same manner as in Example 1, except that the content of the surface-modified inorganic particles was adjusted to 0.3 parts by weight based on 100 parts by weight of the base resin powder. The content of fine powder having a particle diameter of about 150 _m or less contained in the superabsorbent polymer was less than about 2% by weight. Comparative Example 1: Preparation of Super Absorbent Polymer

 Superabsorbent polymer was prepared in the same manner as in Example 1, except that the surface-modified inorganic particles were not used in Example 1. Comparative Example 2: Preparation of Super Absorbent Polymer

 Aerosil 200 to 100 parts by weight of the super absorbent polymer prepared in Comparative Example 1

0.1 parts by weight of Evonik was added and mixed. Comparative Example 3: Preparation of Super Absorbent Polymer

 0.3 parts by weight of Aerosil 200 (Evonik) was added to 100 parts by weight of the super absorbent polymer prepared in Comparative Example 1, and mixed. Test example: Evaluation of physical properties of super absorbent polymer

 Part of the superabsorbent polymers prepared in Examples 1, 2, Comparative Example 2, and Comparative Example 3 were collected and classified for 10 minutes using a testing sieve of mesh size # 100 to remove dust from the superabsorbent polymer ( Dedusting process).

 In addition, the physical properties of the superabsorbent polymer before and after the dedusting process were measured by the method described below and shown in Table 1.

(1) Centrifuge Retention Capacity (CRC)

European Disposables and Nonwovens Association, EDANA) According to the EDANA WSP 241.2 standard, centrifugal water-retaining capacity (CRC) was measured for the superabsorbent polymer with no-load absorption ratio.

 That is, the resin WO (g, about 0.2 g) was uniformly placed in a non-woven bag and sealed, and then immersed in physiological saline, which is a 0.9 wt% aqueous sodium chloride solution at room temperature. After 30 minutes, the bag was drained at 250 G for 3 minutes using a centrifugal separator, and then the mass W2 (g) of the bag was measured. Moreover, after carrying out the same operation without using resin, the mass W1 (g) at that time was measured.

 The water retention capacity (CRC (g / g)) was calculated by substituting the following formula 1 using each mass thus obtained.

 [Calculation 1]

 CRC (g / g) = {[W2 (g)-Wl (g)] / W0 (g)}-1

 In the above formula 1,

 W0 (g) is the initial weight (g) of the superabsorbent polymer,.

 Wl (g) is the weight of the bag measured after immersing an empty bag in physiological saline for 30 minutes at room temperature and then dehydrating it at 250 G for 3 minutes using a centrifuge.

W2 ( _g ) is the weight of the bag containing the superabsorbent polymer, measured after immersing the bag containing the superabsorbent polymer at room temperature in physiological saline for 30 minutes and then dehydrating it at 250 G for 3 minutes using a centrifuge. (2) Absorbing under Pressure (AUP)

 For the super absorbent polymer, Absorbency under Pressure (AUP) was immediately determined according to the method of the European Di sposables and Nonwovens Associ at ion standard EDANA WSP 242.2.

First, a stainless steel 400 mesh wire mesh was mounted on the bottom of a 60 mm diameter plastic cylinder. The phase was evenly sprayed with a superabsorbent resin W0 (g, 0.90 g) to measure the pressure absorbency on the wire mesh under a humidity of 5OT. Subsequently, a piston was added to the superabsorbent polymer to uniformly impart a load of 4.83 kPa (0.7 psi). At this time, the outer diameter of the piston is slightly smaller than 60 麵, there is no gap with the inner wall of the cylinder, was used to be able to move freely up and down. Then, the weight W3 (g) of the device thus prepared was measured. Then, a glass filter of 90 mm in diameter and 5 mm in thickness was placed inside a 150 mm diameter petri dish, and physiological saline (0.9 wt% aqueous sodium chloride solution) was poured into the petri dish. At this time, physiological saline was poured until the surface of physiological saline became horizontal with the upper surface of the glass filter. Then, one sheet of filter paper having a diameter of 90 mm was placed on the glass filter.

 Then, the prepared device was placed on the filter paper so that the superabsorbent resin in the device was swollen by physiological saline under load. After 1 hour, the weight W 4 (g) of the device containing the swollen superabsorbent polymer was measured.

 Using the weight thus measured, the pressure absorption capacity was calculated according to the following equation (2).

 [Calculation 2]

 AUP (g / g) = [W4 (g)-W3 (g)] / W0 (g)

 In the formula 2,

 W0 (g) is the initial weight (g) of the superabsorbent polymer,

 W3 (g) is the sum of the weight of the superabsorbent polymer and the weight of the device capable of applying a load to the superabsorbent polymer,

 W4 (g) is the sum of the weight of the superabsorbent resin and the weight of the device capable of applying a load to the superabsorbent resin after absorbing physiological saline to the superabsorbent resin for one hour under a load (0.7 psi).

(3) Gel Bed Permeabi l i ty

 The free swelling gel bed permeability (GBP) of the superabsorbent resin to physiological saline was measured according to the following method described in Tokken application 2014-7018005.

 Specifically, the apparatus shown in Figs. 1 to 3 was used to measure the free swelling GBP. Firstly, a plunger 536 equipped with a weight 548 is placed in an empty sample container 530, and with a suitable gauge to an accuracy of 0.01 mm, from the top of the weight 548 to the bottom of the sample container 530. The height was measured. During the measurement, the force applied by the thickness gauge was adjusted to less than about 0.74 N.

On the other hand, among the super absorbent polymers for which GBP is to be measured, the super absorbent polymer passed through the US standard 30 mesh screen and maintained on the US standard 50 mesh screen Screening was carried out to obtain a super absorbent polymer having a particle diameter of 300 to 600 / m.

About 2.0 _g of the super absorbent polymer thus classified was placed in the sample container 530 and evenly spread on the bottom of the sample container. Subsequently, the vessel without the plunger 536 and the weight 548 was immersed in 0.9 wt% aqueous sodium chloride solution for about 60 minutes to swell the superabsorbent polymer under no pressure. At this time, the sample vessel 530 was overlaid on a mesh positioned in the liquid reservoir so that the sample vessel 530 was slightly above the bottom of the liquid reservoir, and the mesh did not affect the movement of physiological saline to the sample vessel 530. Not used. During saturation the height of the physiological saline was adjusted so that the surface in the sample vessel was defined by the swollen superabsorbent resin, not physiological saline.

 At the end of this period, the assembly of the plunger 536 and the weight 8 is laid down on the swollen superabsorbent resin 568 in the sample container 530, and then the sample container 530, plunger 536, weight 548 and the swollen superabsorbent resin 568 were removed from the solution. The sample vessel 530, plunger 536, weight 548 and swollen superabsorbent resin 568 were then placed on a flat, large grid, uniform thickness, non-deformable plate, prior to GBP measurements. Leave it on for a while. Then, using the same thickness gauge as previously used, the height from the top of the weight 548 to the bottom of the sample container 530 was measured again. Then, the height measurement of the device in which the plunger 536 equipped with the weight 548 is placed in the empty sample container 530 is subtracted from the height measurement of the device containing the swollen superabsorbent resin 568. The thickness or height 'Ή' of the superabsorbent polymer was obtained.

 For GBP measurements, a 0.9 weight> aqueous sodium chloride solution of physiological saline was flowed into the sample vessel 530 containing the swollen superabsorbent resin 568, plunger 536 and weight 548. The f low rate of physiological saline into the sample vessel 530 was adjusted so that the physiological saline overflowed to the top of the cylinder 534 so that a consistent head pressure equal to the height of the sample vessel 530 was shown. Then, using the balance 602 and the beaker 603, the amount versus time of the solution passing through the swollen superabsorbent resin 568 was measured gravimetrically once the overflow began,

Data points were collected from the balance 602 every second for at least 60 seconds. The flow rate Q through the swollen superabsorbent resin 568 causes the swollen superabsorbent resin 568 to Determined in g / sec by linear least-square fit of fluid (g) versus time (sec) passing.

The GBP (cm ² ) was calculated according to the following equation 3 using the data values thus obtained.

 [Calculation 3]

 K = [Q * H * μ] / [Α * ρ * Ρ]

 In the above formula 3,

Κ is the gel bed transmission (cm ² ) ，

 Q is the flow rate (g / sec),

 H is the height (cm) of the swollen superabsorbent resin,

μ is the liquid viscosity (Ρ) (in this test ^: the viscosity of the saline solution used is about lcP),

 A is the cross-sectional area for the liquid flow (28.27cuf for the sample vessel used in this test)

p is the liquid density (g / cm ³ ) (about 1 g / cm ³ for the saline solution used in this test),

P is the hydrostatic pressure (dyne / cm ²⁾ (normally approximately 7,797dyne / cm ^2).

The hydrostatic pressure is calculated from the equation P = p * g * h, where p is the liquid density (g / cm ³ ), g is the acceleration of gravity (nominally 981 cm / sec ² ), and h is the fluid height (e.g. For example, for the GBP test described herein, 7.95 cm).

Test at least two samples, average the results to determine the free swelling GBP of the superabsorbent polymer, convert the units to darcy (Idarcy = 0.98692 x 10 ^'8 cm ² )

1 is shown.

 [Table 1]

 Mineral Particle Type Before Dedusting Process After Dedusting Process

(Content) _'' (After surface crosslinking)

CRC AUP GBP CRC AUP GBP

(g / g) (g / g) (darcy) (g / g) (g / g) (darcy) EXAMPLES Surface of Preparation Example 34.6 23.3 11 34.3 23.5 9

1 modified mineral mouth

 character

 (Base resin minutes

 100 parts by weight

 0.1 parts by weight)

EXAMPLES Surface of Preparation Example 32.6 21.6 41 32.4 22.2 45

2 modified mineral mouths

 character

 (Base resin minutes

 100 parts by weight

 0.3 parts by weight)

Comparative Example-34.5 22.7 3--

One

Comparative Example Aerosi l 200 35.1 21.0 8 34.1 21.6;

2 (super absorbent resin

 Based on 100 parts by weight

 0.1 parts by weight)

Comparative Example Aerosi l 200 34.6 16.7 48 33.4 17.6 31 3 (0.3 parts by weight based on 100 parts by weight of superabsorbent polymer)

Referring to Table 1, it is confirmed that the super absorbent polymer according to the embodiment of the present invention has excellent water retention, pressure absorption and water permeability. On the other hand, if the superabsorbent polymers of Comparative Examples 1 to 3 are excellent in any one of water-retaining ability, pressure-absorbing ability, and water permeability, at least the other physical property is poor.

 In addition, the superabsorbent polymers of Examples 1 and 2 do not release inorganic particles even after the dedusting process to maintain excellent physical properties, whereas the superabsorbent resins of Comparative Examples 2 and 3 exhibit physical property degradation.

 Thus, it is confirmed that the superabsorbent polymer according to the embodiment of the present invention has a surface crosslinked structure with surface-modified inorganic particles, thereby minimizing physical property deterioration in the manufacturing and transporting process of the superabsorbent polymer as well as excellent physical properties. .

[Explanation of code]

 500 GBP measuring device

 528 test device assembly

 530 sample containers

 534 cylinder

 534a: a part having an outer diameter of 66 mm

 536 plunger

 538 shift

 540 O-Ring

 544 554 ， 560 ： Hole

 548 annular weight

 548a: through-bore

550 ： Plunger Head 562 ： Shaft Hole

 564 ： 100 mesh stainless steel cloth screen 566 ： 400 mesh stainless steel cloth screen 568 ： Sample

600 ： Wear

601 ： collection device

602 ： Scale

603 ： Beaker

604 ： Instrument pump

Claims

【Claims】

【Claim 1】

A base resin powder comprising a crosslinked polymer obtained by polymerizing a water-soluble ethylenically unsaturated monomer having at least a partially neutralized acidic group in the presence of an internal crosslinking agent; And the cross-linked polymer is further cross-linked in the presence of surface-modified inorganic particles, and includes surface cross-linkers formed on the base resin powder,

A superabsorbent polymer in which inorganic particles are chemically bonded to the crosslinked polymer included in the surface crosslinked layer through oxygen-containing bonds or nitrogen-containing bonds.

【Claim 2】

The method of claim 1, wherein the water-soluble ethylenically unsaturated monomer is

Acrylic acid, methacrylic acid, maleic anhydride, fumaric acid, crotonic acid, itaconic acid, 2-acryloylethane sulfonic acid, 2-methacryloylethane sulfonic acid, 2-

Anionic monomers of (meth)acryloylpropanesulfonic acid or 2-(meth)acrylamide-2-methylpropanesulfonic acid and salts thereof;

(meth)acrylamide, N-substituted (meth)acrylamide, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, methoxypolyethylene glycol (meth)acrylate or polyethylene glycol ( A nonionic hydrophilic-containing monomer of meth)acrylate; and

(Ν,Ν)-dimethylaminoethyl (meth)acrylate' or (Ν,Ν)-dimethylaminopropyl (meth)acrylamide, an amino group-containing unsaturated monomer and its quaternary product; at least one selected from the group consisting of Containing a super absorbent polymer.

[Claim 3]

The superabsorbent resin of claim 1, wherein the cross-linked polymer comprises a cross-linked polymer in which the water-soluble ethylenically unsaturated monomer is polymerized in the presence of an internal cross-linking agent containing a multifunctional acrylate-based compound having a plurality of ethylene oxide groups.

【Claim 4】

The method of claim 1, wherein the internal crosslinking agent is polyethylene glycol diacrylate, Containing at least one selected from the group consisting of glycerin diacrylate, glycerin triacrylate, unmodified or eroxylated trimethylpropane triacrylate (TMPTA), nucleic acid diol diacrylate, and triethylene glycol diacrylate. Super absorbent resin.

【Claim 5】

The method of claim 1, wherein the inorganic particles have a specific surface area of 5 to 600 m ² /g and a diameter of 5 to 500 nm.

【Claim 6】

The superabsorbent polymer of claim 1, wherein the inorganic particles are silica particles or alumina particles.

[Claim 7]

The superabsorbent polymer of claim 1, wherein the inorganic particles are combined in an amount of 0.01 to 2 parts by weight based on 100 parts by weight of the superabsorbent polymer.

【Claim 8】

The superabsorbent polymer according to claim 1, wherein the surface cross-linking layer is formed by additional cross-linking of a cross-linking polymer in the presence of surface-modified inorganic particles and a surface cross-linking agent.

【Claim 9】

The method of claim 8, wherein the surface cross-linking agent is ethylene glycol, 1,4-butanediol, 1,6-hexanediol, propylene glycol, 1,2-hexanediol, 1,3-hexanediol, 2-methyl-1,3 - Selected from the group consisting of propanediol, 2, 5-hexanediyl, 2-methyl-1, 3-pentanediol, 2-methyl-2,4-pentanediol, tripropylene glycol, glycerol, ethylene carbonate and propylene carbonate A super absorbent resin containing one or more types.

【Claim 10】

The method of claim 1, wherein the centrifugation retention capacity for physiological saline is 30 to 40 g/g. A superabsorbent polymer having a pressure absorption capacity of 0.7 psi for physiological saline solution of 10 to 26 g/g and a free-swelling gel bed permeability of 5 to 120 darcy.

【Claim 11】

The superabsorbent polymer according to claim 1, having a particle size of 150 to 850/ΛΠ.

【Claim 12】

Cross-polymerizing a water-soluble ethylenically unsaturated monomer having at least a partially neutralized acidic group in the presence of an internal cross-linking agent to form a water-containing gel polymer;

Forming a base resin powder by drying, pulverizing and classifying the water-containing gel polymer; and

A first step comprising the step of additionally crosslinking the surface of the base resin powder to form a surface crosslinking layer in the presence of inorganic particles surface modified with at least one functional group selected from the group consisting of an epoxy group, a hydroxy group, an isocyanate group, and an amine group. Method for manufacturing superabsorbent polymer.

【Claim 13】

The method of claim 12, further comprising the step of producing surface ^- modified inorganic particles by modifying the surface of the inorganic particles with a modifier represented by the following formula (1):

[Formula 1]

R In Formula 1, to R ₃ are each independently an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, or a halogen, at least one of which is not an alkyl group, and R 4 is an epoxy group, a hydroxy group, an isocyanate group, and It is a substituent having 2 to 10 carbon atoms and having at least one functional group selected from the group consisting of amine groups.

[Claim 14]

The method of claim 12, wherein the surface-modified inorganic particles are used in an amount of 0.01 to 10 parts by weight based on 100 parts by weight of the base resin powder.

[Claim 15]

The method of claim 12, wherein a surface cross-linked layer is formed by additional cross-linking the surface of the base resin powder in the presence of the surface-modified inorganic particles and a surface cross-linking agent.