WO2015016643A1 - Super absorbent polymer - Google Patents

Abstract

The present invention relates to a super absorbent polymer which has excellent initial water absorption and which is watertight under pressure, even after time has elapsed, and concurrently optimizes, to predetermined ranges, centrifuge repair capability (CRC), absorbency under load (AUL), gel bed permeability (GBP), and absorption rate under pressure, etc. of the super absorbent polymer, thereby being capable of improving the physical properties of the final diaper, and thereby being capable of manufacturing a diaper to which ultra-thin technology has been applied.

Description

 【Specification】

 [Name of invention]

 Superabsorbent polymer

 Technical Field

 The present invention relates to a superabsorbent polymer which is excellent in basic physical properties such as absorbency and exhibits a fast absorption rate under pressure.

 [Technique to become background of invention]

Super Absorbent Polymer (SAP) is a synthetic polymer material capable of absorbing water of 500 to 1,000 times its own weight. It is named after Absorbent Gel Mater i al). Such superabsorbent polymers have been put into practical use as sanitary instruments, and are currently used in gardening, soil repair agents, civil engineering and building index materials in addition to sanitary products such as paper diapers for children _. It is widely used as a material for raising seedlings, seedling sheets, freshness retainers in food distribution, and for steaming.

 As a method for producing such a super absorbent polymer, a method by reverse phase suspension polymerization or a method by aqueous solution polymerization is known. Reverse phase suspension polymerization is disclosed in, for example, Japanese Patent Laid-Open No. 56-161408, Japanese Patent Laid-Open No. 158209, Japanese Patent Laid-Open No. 57-198714, and the like.

As a method of aqueous solution polymerization, a thermal polymerization method is carried out by breaking and polymerizing a polymer gel in a kneader having several shafts, and a photopolymerization method which simultaneously performs polymerization and drying by irradiating ultraviolet rays or the like on a belt with a high concentration of aqueous solution. Etc This is known.

 The hydrous gel polymer obtained through the polymerization reaction as described above is generally pulverized through a drying process and commercially available as a powder product.

 In products with superabsorbent polymers, permeability is a measure of the fluidity of the absorbed liquid. The transmittance may vary depending on the characteristics of the particle size distribution of the crosslinked resin, the particle shape and the connectivity of the openings between the particles, the surface modification of the swollen gel, and the like. The fluidity of the liquid passing through the swollen particles depends on the transmittance of the superabsorbent polymer composition. When the transmittance is low, the liquid cannot easily flow through the super absorbent polymer composition.

 One method of increasing the transmittance in a super absorbent polymer is to perform a surface crosslinking reaction after polymerization of the resin, and at this time, a method of adding silica (si Π ca) or clay (cl ay) together with the surface crosslinking agent has been used. . For example, US Pat. Nos. 5,140, 076 and 4,734,478 disclose the addition of silica of surface crosslinking of dry superabsorbent resin powders.

 However, as the silica or clay is added, the transmittance is improved. However, there is a problem in that the water retention capacity or the pressure absorption capacity is decreased in proportion to the silica, and the clay is easily separated from the superabsorbent polymer due to the external physical lamination. In addition, the superabsorbent water retention ability and the pressure-absorbing capacity is above a certain level, but has not been developed a superabsorbent polymer that exhibits a fast absorption characteristics under pressure and exhibits a substantially fast absorption characteristics when applied to an actual diaper.

[Content of invention] Problem to be solved

 The present invention is excellent in the physical properties through the surface treatment of the super absorbent polymer, in particular excellent in the initial absorbency, after a long time the water is hardly coming out under pressure under the excellent absorbency, the superabsorbent resin showing a fast absorption rate under pressure To provide.

 The present invention also provides a method for producing the superabsorbent polymer. [Measures of problem]

 The present invention relates to a crosslinked polymer obtained by surface-crosslinking a base resin in a powder form obtained by polymerizing a water-soluble ethylene-based unsaturated monomer containing an acidic group and at least partially neutralized with two or more internal crosslinking agents with a di- or glycol-based compound having 2 to 8 carbon atoms. It has a centrifugal water retention capacity (CRC) of 28 g / g or more and a pressure absorption capacity of 0.9 psi (AU).

L) is at least 18 g / g, gel bed permeability (GBP) is at least 45 darcy, and 0.3 ps i pressurized absorption rate of 30 ps. do.

The present invention also provides a water-soluble ethylenically unsaturated monomer containing an acidic group and at least partially neutralized, two or more internal crosslinkers, photopolymerization initiators, and thermal polymerization initiators having a cure dose of from 0.1 to 0.35 J / cuf. Thermally polymerizing and photopolymerizing the monomer composition to form a hydrogel polymer; Drying the hydrogel polymer; Pulverizing the dried polymer; And adding a compound represented by the following Chemical Formula 1 and a polyvalent metal cation to the ground polymer to perform surface crosslinking reaction. [Formula 1]

Rr (CH ₂ ) _n -R ₂

 In Chemical Formula 1,

And R ₂ is the same or different and is each independently a hydroxyl group, an amine group, an epoxide group or an isocyanate group;

 n is an integer of 1-3.

Hereinafter, a super absorbent polymer and a method of preparing the same according to specific embodiments of the present invention 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 ¹ " refers to the inclusion of any component (or component) without particular limitation, and other components (or components). The inventors of the present invention have excellent initial absorbency, and after a long period of time, water absorbed hardly under pressure under a long period of time, and thus the superabsorbent polymer has been excellently absorbed. When the resin's centrifugation water retention capacity (CRC), pressure absorption capacity (AUU), gel bed permeability (GBP), and pressure absorption rate are all optimized at the same time, the properties of the final diaper can be improved. The present invention was completed by confirming that the diaper to which the technique was applied can be produced. Accordingly, according to one embodiment of the present invention, a superabsorbent polymer having excellent initial absorbency and hardly coming out of moisture under a pressurized state even after a long time is provided has an excellent absorbency. The superabsorbent polymer of the present invention has a centrifugal water retention capacity (CRC) of 28 g / g or more, a 0.9 ps i pressure absorption capacity (AUL) of 18 g / g or more, a gel bed transmittance (GBP) of 45 darcy or more , The pressurized absorption rate of 0.3 psi is 30 to 200 seconds upon tertiary injection with 0.9 wt% saline.

 In particular, the superabsorbent polymer of the present invention is photopolymerized and thermally polymerized by using two or more kinds of polyethyleneglycol diacrylate as an internal crosslinking agent, as described below. Even after the elapse of time under the pressurized state hardly comes out of the moisture can exhibit excellent absorption ability. Accordingly, superabsorbent polymers that satisfy certain parameter properties of the present invention are not only various hygiene products; It is widely used for materials such as horticultural soil repair, civil engineering, construction index, seedling sheet, freshness keeping in food distribution, and steaming.

 As described above, the synergistic effect of the superabsorbent polymer can be synergistically achieved through the combination of physical properties that simultaneously optimize both centrifugal water retention capacity (CRC), pressure absorption capacity (AUL), gel bed permeability (GBP), and pressure absorption rate. Can provide. Therefore, the present invention can induce excellent physical properties and comfortable fit in manufacturing the absorber.

 In the superabsorbent polymer of the present invention, the centrifugal water retention capacity (C RC) for the physiological saline may be represented by the following Equation 1.

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

 In Formula 1,

W ₀ (g) is the weight of water absorbent resin (g), W g) is the weight of the device measured after dehydration at 250G for 3 minutes using a centrifuge without using water absorbent resin, Ψ ₂ (g) Is the device weight including the absorbent resin after immersion of the absorbent resin in 0.9 mass% physiological saline at room temperature for 30 minutes, followed by dehydration at 250 G for 3 minutes using a centrifuge. In particular, the absorbent weight W ₀ (g) can be measured by the weight of the absorbent resin classified to 300 to 600 micrometers (미).

 The centrifugal water retention capacity (CRC) of the superabsorbent polymer for physiological saline may be 28 gig or more or 28 g / g to 34 g / g, preferably 29 g / g or more, more preferably 30 g. It can be more than / g. When the centrifugal water-retaining capacity (CRC) for the saline solution is less than 28 g / g, the diaper water-retaining ability is lowered, which may cause a problem of bad diaper physical properties.

 In addition, in the super absorbent polymer of the present invention 0. The pressure absorption capacity (AUL) of 9 ps i may be represented by the following formula (2).

 [Calculation 2]

AUL (g / g) = [W ₄ (g)-W ₃ (g)] / ₀ (g)

 In the formula 2,

W ₀ (g) is the weight of the absorbent resin (g), W ₃ (g) is the sum of the weight of the absorbent resin and the weight of the device capable of applying a load to the absorbent resin, and W ₄ (g) is the load ( 0.9 psi) is the sum of the weight of the absorbent resin absorbed by the moisture after supplying the absorbent resin with water for 1 hour and the weight of the device capable of applying a load to the absorbent resin.

In one example of the invention, the 0.9 ps i of a pressure absorbent capacity (AUL) is 300 to 600 micrometers (; Mil) classified into a pressure absorbing capacity (AUL) measurement kit and weighed 0.9 psi It can be measured after pressure swelling for 1 hour under 0.9% salt water in the state of raising the weight. At this time, after 1 hour, the cell can be weighed to measure the absorbency (AUL) under pressure. In this case, the absorbent weight W ₀ (g) can be measured by the weight of the absorbent resin classified as 300 to 600 micrometer / m).

 0.9 psi of pressure-absorbing capacity (AUL) of the superabsorbent polymer in physiological saline is

18 g / g or more, preferably 18.5 g / g or more, more preferably 19 g / g or more. The higher the pressure absorption capacity is better, but the pressure absorption capacity is a property opposite to the water retention capacity, if the pressure absorption capacity is too high, the water retention capacity may decrease. Improving the pressure absorption capacity and water retention capacity at the same time is an important technical factor.

In the present invention, W ₀ (g) described in Formulas 1 to 2 corresponds to the weight (g) of the absorbent resin applied to each property value, and may be the same or different.

In the present invention, the gel permeability (GB P) of the superabsorbent polymer to the saline solution may be 45 darcy or more, preferably 48 darcy or more, and more preferably 55 darcy or more. Higher gel bed transmittance is better, but too high gel bed transmittance In this case, deterioration of water-retaining capacity or pressure-absorbing capacity may occur. Here, the gel bed permeability (GBP) is expressed as "darcy" which is the CGS unit for permeability. For example, when the pressure difference between two cross sections of a solid is 1 atm, the fluid 1 cm ² having a viscosity of 1 cps is the transmittance of the solid flowing within 1 second through the cross section thickness 1 cm and the cross section area 1 cm ² . Since the transmittance has no SI unit for transmittance, it has the same unit as the area and _m ² is used. 1 different time is about 0. 98692 X 10 ^"12 m ² or about 0.998692 10 ^{" 8} cm ² . A method for measuring such gel bed permeability is specified in US Pat. No. 7, 7,179, 851.

 The gel bed permeability (GBP) is a measure of the permeability of the swelling bed of gel particles (e.g., surface treated absorbent material or superabsorbent material prior to surface treatment), especially under conditions referred to as "free swelling" conditions. will be. However, gel particles (eg, superabsorbent materials as used herein) under " loaded " conditions normally matched by the wearer to the wearer's normal use load (eg, sitting, walking, bending, etc.). When measuring the permeability of the swelling bed of a polymeric or absorbent material, i.e. the gel bed permeability (0.3 ps i GBP or 0.3 GBP) under load is at least 2.5 darcy, preferably at least 2.8 da rcy, more preferably at 3.0 It can be more than darcy. The high permeability of the gel bed under subdivision means that the gel strength is high, which may be an indicator that simulates the permeability of the baby after pressing urine weight.

In addition, the superabsorbent polymer of the present invention exhibits a fast absorption rate under pressure while the liquid-permeable, water-retaining ability, and pressure-absorbing ability as described above are above a certain level. It has a characteristic to appear. In particular, the superabsorbent polymer has a pressure absorption rate of 0.3 ps i at the third injection of 0.9 wt% physiological saline is 30 to 200 seconds (sec), preferably 40 to 190 seconds, more preferably 50 To 180 seconds. The faster the absorption rate under pressure, the better. However, if the pressure absorption rate is slower than 200 seconds, urine leakage may occur due to the slow absorption of urine in the diaper. In particular, the pressure-absorbing rate of the superabsorbent polymer is 2 g of an absorbent resin under a pressurized condition of 0.3 ps i and 10 mL of 0.9 wt. ¾> saline solution is repeated three times at three minute intervals. The rate of absorption for saline is measured.

In the present invention, the pressure absorption rate may be measured using a device as shown in FIG. 1, and includes a cylinder (cyl inder, w / o-ring: Mesh # 400) and a plunger (pi Linger, Mesh # 100), It can be measured with 0.9 wt% physiological saline solution using a device equipped with a weight. In particular, the device for measuring the absorption rate under pressure in the present invention is unlike the conventional superabsorbent resin measured by sucking the brine, etc., the superabsorbent resin (layer) It is characterized by measuring by injecting from the top of the). In addition, the absorption rate under pressure can be measured by repeated experiments over three or more times. In a more specific example, first spread the filter paper (Whatman paper 4) at the bottom of the cylinder of Figure 1, evenly by quantifying 2 g of the super absorbent polymer of the present invention. The plunger is then removed, 0.3 psi weight, load is added and 10 mL of 0.9% salt ine solut ion is poured into the hole of the plunger, and the plunger Looks into the hole of Measure the time the brine disappears completely. In the present invention, this operation is repeated three times or more, and the time (second, sec) measured in the third trial is defined as the pressure absorption rate. In particular, the conventional method of absorbing brine under pressure is a method of diffusion absorption from the bottom up, whereas the method of measuring the rate of absorption under pressure according to the present invention is a method of injecting salt water from above. This is a very important measurement because it can best simulate the actual diaper, for example, it can best simulate the way the child peees and the diaper absorbs, and can also predict the diaper performance between products with different physical properties. It can be the way.

 At this time, looking at the process of measuring the pressure absorption rate of the super absorbent polymer by the method described above, the super absorbent polymer will absorb the physiological saline at a very fast rate in the first and second experiments. Thus, when the water swelling degree of the resin is increased due to the moisture absorption in the first and second experiments, the pressure absorption rate in the third experiment can be differentiated according to the performance of each super absorbent polymer. As in the superabsorbent polymer of the present invention, the pressure absorption rate of 0.3 psi in the third injection into 0.9 wt% physiological saline should be maintained in an optimized range of 30 to 200 seconds (sec). Even if the absorbent capacity is above a certain level, it exhibits a fast absorption characteristic under pressure, and can exhibit a substantially fast absorption characteristic when applied to an actual diaper.

On the other hand, the superabsorbent polymer of the present invention is a di- or glycol-based base resin having a powder form in which a water-soluble ethylenically unsaturated monomer containing an acidic group and at least partially neutralized is polymerized with two or more complex internal crosslinking agents. With compound And crosslinked polymers surface-crosslinked.

 In addition, the crosslinking density of the crosslinked polymer may be a factor influencing the pressure absorption capacity (AUL) value, and it is preferable to surface crosslink the base resin according to the method of the present invention.

 The water-soluble ethylenically unsaturated monomer is acrylic acid, methacrylic acid, maleic anhydride, fumaric acid, crotonic acid, itaconic acid, 2-acryloylethane sulfonic acid 2-methacryloyl ethanesulfonic acid, 2 '(meth) acryloyl Anionic monomers of propanesulfonic 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 glycol (meth) acrylate Hydrophilic containing monomers; And amino group-containing unsaturated monomers of (Ν, Ν) -dimethylaminoethyl (meth) acrylate or (Ν, Ν) -dimethylaminopropyl (meth) acrylamide and quaternary compounds thereof; It may include. Among these, acrylic acid in which at least part of an acidic group is neutralized by strong bases, such as sodium hydroxide, and its salt can be used suitably as said monomer. In such a monomer, the acrylic acid may be at least about 50 mol%, or at least about 60 mol%, or at least about 70 mol%, and may be neutralized, whereby the overall physical properties of the present invention may be more effectively achieved. That is, the water-soluble ethylenically unsaturated monomer may have a neutralization degree of about 50 mol or more for acid groups.

On the other hand, according to another embodiment of the invention, there is provided a method for producing a super absorbent polymer as described above. The manufacturing method of the super absorbent polymer includes an acid group. High temperature at least partially neutralized water-soluble ethylenically unsaturated monomer, thermal polymerization to a monomer composition comprising two or more internal crosslinkers, a photopolymerization initiator, and a thermal polymerization initiator having a cure dose of from 0. 16 to 0.35 J / citf. And photopolymerization to form a hydrogel polymer; Drying the hydrogel polymer; Pulverizing the dried polymer; And adding a compound represented by the following Chemical Formula 1 and a polyvalent metal cation to the ground polymer to perform a surface crosslinking reaction.

 [Formula 1]

 In Chemical Formula 1,

And R ₂ is the same or different and is each independently a hydroxyl group, an amine group, an epoxide group or an isocyanate group;

 n is an integer of 1-3.

Particularly, in the present invention, as described above, the polymerization proceeds using two or more kinds of polyethylene glycol diacrylate as the internal crosslinking agent, and the surface crosslinking temperature conditions are optimized and applied in a specific range, thereby providing excellent physical properties and particularly initial absorbency. It is excellent, it is possible to produce a superabsorbent polymer having excellent properties of water absorption since moisture does not come out from the pressurized state even after a long time. The synergistic effect can be provided by a combination of physical properties that simultaneously optimizes the centrifugal water retention capacity (CRC), the pressure absorption capacity (AUL), and the gel bed permeability (GB P) of the high absorbent resin thus prepared. In the manufacturing process of the super absorbent polymer of the present invention, a substance whose δ _ρ defined by the Hansen solubility parameter satisfies δ _ρ <11 (J / cm ³ ) ^1/2 and δ _Η is δ _Η <4.5 (J / The surface crosslinking reaction may be performed by further adding one or more materials selected from the group consisting of materials satisfying cm ³ ) ^1/2 .

 According to the manufacturing method of the super absorbent polymer, it is possible to manufacture a superabsorbent polymer having improved physical properties without improving water retention or pressurized absorbent capacity while having improved liquid permeability.

 In addition, in the manufacturing method of the super absorbent polymer of the present invention, the monomer composition which is a raw material of the super absorbent polymer includes a water-soluble ethylenically unsaturated monomer, a photopolymerization initiator, and a thermal polymerization initiator.

 The water-soluble ethylenically unsaturated monomer may be used without any limitation any monomers commonly used in the production of superabsorbent polymers. Any one or more monomers selected from the group consisting of anionic monomers and salts thereof, nonionic hydrophilic containing monomers and amino group-containing unsaturated monomers and quaternized compounds thereof can be used.

Specifically, (meth) acrylic acid, maleic anhydride, fumaric acid, crotonic acid, itaconic acid, 2-acryloylethane sulfonic acid, 2-methacryloylethanesulfonic acid, 2- (meth) acryloyl propanesulfonic acid or 2 음이온 anionic monomers of (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 Non-silver-based hydrophilic monomers of (meth) acrylate or pulley ethylene glycol (meth) acrylate; And amino group-containing unsaturated monomers of (Ν, Ν) -dimethylaminoethyl (meth) acrylate or (Ν, Ν) ᅳ dimethylaminopropyl (meth) acrylamide, and quaternary compounds thereof. Can be.

More preferably contains acrylic acid or ^its' salts, for example, may be used an alkali metal salt such as acrylic acid or its sodium salt, and becomes possible to manufacture the water-absorbent resin using these monomers are beams having excellent physical properties come. 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).

 The concentration of the water-soluble ethylenically unsaturated monomer may be about 20 to about 60% by weight, preferably about 40 to about 50% by weight relative to the monomer composition including the raw material and the solvent of the superabsorbent polymer. The concentration may be appropriate in consideration of the reaction time, 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 economic problems may occur. On the contrary, when the concentration is too high, a part of the monomer may be precipitated or the grinding efficiency of the polymerized hydrogel polymer may be low. It may cause process problems such as appearing, and the physical properties of the super absorbent polymer may decrease.

In the superabsorbent polymer production method of the present invention, by including a thermal polymerization initiator together with a photopolymerization initiator, a certain amount of heat is generated by irradiation such as ultraviolet irradiation, and a certain amount of heat is generated as the polymerization reaction is exothermic. Light into generation At the same time as the polymerization, thermal polymerization can proceed.

 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 e, phenylglyoxylate, and benzyldimethyl ketal (for example, benzoin ether). One or more selected from the group consisting of Benzyl Dimethyl Ke etal, acyl phosphine and alpha -aminoketone can be used. On the other hand, specific examples of acyl phosphine include commercially available luci r in TP0, that is, 2, 4, 6_trimethyl-benzoyl-trimethyl phosphine oxide (2, 4, 6-tr imethyl benzoyl- tr imethyl phosphine oxide) Can be used. A wider variety of photopolymerization initiators are well specified in Reinhold Schwa lm, "UV Coat ings: Basics, Recent Developments and New Application (Elsevier 2007) p 115", and are not limited to the examples described above.

 The photopolymerization initiator may be included in a concentration of 40 to 200 ppm with respect to the monomer composition, preferably 45 to 180 ppm, more preferably may be included in a concentration of 50 to 170 ppm. 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, a persulfate-based initiator containing sulfur may be used as the thermal polymerization initiator. Specifically, examples of persulfate-based initiators include sodium persulfate (Sodium pe rsul fate; Na ₂ S ₂ 0 ₈ ), potassium persulfate (K ₂ S ₂ 0 ₈ ), and ammonium persulfate (AH onium persul fate; (NH ₄ ) ₂ S ₂ 0 ₈ ) There may be more than one selected.

 The thermal polymerization initiator may be included in an amount of about 0.05 to about 0.3% by weight based on the monomer composition, preferably 0.08 to 0.25 weight ¾ (wt>), more preferably 0.1 to 0.2 weight It may be included at a concentration of%. When the content of the thermal polymerization initiator is too low, additional thermal polymerization hardly occurs, so that the effect of adding the thermal polymerization initiator may be insignificant. When the content of the thermal polymerization initiator is excessively large, the molecular weight of the superabsorbent polymer is small and the physical properties are uneven. Can be done. According to an embodiment of the present invention, the monomer composition may include a composite internal crosslinking agent using two or more internal crosslinking agents as a raw material of the super absorbent polymer. The internal crosslinking agent may include at least one functional group capable of reacting with the water-soluble substituent of the water-soluble ethylenically unsaturated monomer and at least one ethylenically unsaturated group; Or the water-soluble substituent of the said monomer and / or the water-soluble substituent formed by the hydrolysis of the monomer, and the crosslinking agent which has 2 or more of the functional groups which can react can be used in combination of 2 or more types. In this case, the internal crosslinking agent may be one having two to three functional groups as described above.

In particular, the two or more internal crosslinking agents may be selected from the group consisting of polyfunctional acrylate compounds each having a plurality of ethylene oxide groups. The polyfunctional acrylate compound having a plurality of alkylene oxide groups is polyethylenegly Polyethyl diacrylate (PEGDA), ethoxylated trimethyl propane triacrylate (Ethoxylated-TMPTA), may be selected from the group consisting of nucleic acid diol diacrylate triethylene glycol diacrylate. In addition, the internal crosslinking agent may have a curing amount of 80% or more to 180% or less relative to the curing amount (acrylic acid) of the curing amount (acrylic acid) in terms of uniformity of the internal crosslinking. Furthermore, the internal crosslinking agent is preferably a curing amount of 90% or more to 160% or less, more preferably 95% or more to 155% or less of the cure dose of acrylic acid (acrylic acid) It may have an amount. For example, the internal crosslinking agent may have a curing dose of 0.16 to 0.35 J / cu, preferably 0.18 to 0.32 J / cuf, more preferably 0.2 to 0.3 J / ciif. Herein, the amount of curing of the internal crosslinking agent is an amount of energy required for curing. That is, the same number indicating the _cure dose ( _cure dose) is required to increase the energy required for the ksutok curing. In addition, the values expressed as the cure dose may be measured using a photometer. For example, the illuminance of the lamp may be set in a predetermined curing device accessory, and the sample may be sent on the belt of the curing machine and evaluated through the UV curing machine. At this time, it can be measured by evaluating how many times the curing machine has passed based on the speed and light quantity of the conveyor of the curing machine, and calculating the total energy after the surface has been cured. Therefore, there is no limitation on the amount of separate sample when measuring the cure dose. Also, as a more specific example, when making such a measurement, a solution of about 0.5 cm in 100 mm saale is applied to the conveyor belt. It can be measured by operating the high belt.

The _cure dose values for some materials that can be used as internal crosslinkers are shown in Table 1 below.

 Table 1

In the present invention, by using two or more kinds of components having a cure dose of 60% or less based on acrylic acid (AA) among various acrylic hydrocarbon compounds listed in Table 1 above, In particular, it is possible to prepare a super absorbent polymer having excellent initial absorbency and excellent water absorption since water hardly comes out under pressure even after a long time.

Such a composite internal crosslinking agent is about 0.05 to about the monomer composition It can be included at a concentration of about 3% by weight to crosslink the polymerized polymer. The composite internal crosslinking agent may preferably be included in an amount of about 0.01 to 2.5 wt%, more preferably about 0.1 to 2 wt%.

 In the production method of the present invention, the monomer composition of the super absorbent polymer may further include additives such as thickeners, plasticizers, preservative 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 of the composition as long as it can dissolve the above-mentioned components, for example, water, ethanol, ethylene glycol, diethylene glycol, triethylene glycol, 1, 4-butanedi , 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, and carby may be used in combination of one or more selected from methyl cellosolve acetate, Ν, Ν-dimethylacetamide, and the like.

 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, hydrogel polymerization by thermal polymerization or photopolymerization of such a monomer composition There is no restriction | limiting in particular if the method of forming a sieve is also the polymerization method normally used.

 Specifically, the polymerization method is largely divided into thermal polymerization and photopolymerization according to the polymerization energy source, when the thermal polymerization is usually carried out, it can be carried out in a semi-unggi with a stirring shaft 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, the polymerization process is carried out at a polymerization temperature of about 35 ^° C or more or 35 to 90 ° C thermal polymerization process, and together with the photopolymerization by irradiation of light in the ultraviolet (UV) region of about 100 to 400 ηηι Can be done.

 In addition, as described above, the hydrous gel polymer obtained by supplying hot air or by thermal polymerization by heating the reaction machine according to the shape of the stirring shaft provided in the reaction machine, may be used in a reaction vessel such as a kneader having a stirring shaft. The hydrogel polymer discharged into the form may be in the form of several centimeters to several millimeters. Specifically, the size of the obtained water-containing gel polymer may vary depending on the concentration and the injection speed of the monomer composition to be injected, and a hydrogel polymer having a weight average particle diameter of 2 to 50 ™ may be obtained.

On the other hand, when the photopolymerization is carried out in a semi-unggi equipped with a movable conveyor belt as described above, the form of the hydrous gel polymer generally obtained may be a sheet-like hydrogel polymer having a width of the belt. At this time, the thickness of the polymer sheet Depending on the concentration of the monomer composition introduced and the rate of injection, it is usually desirable to feed the monomer composition so that a polymer on a sheet having a thickness of about 0.5 to about 5 cm can be obtained. When supplying the monomer composition to such an extent that the thickness of the polymer on the sheet is too thin, it is not preferable because of low production efficiency, and when the polymer thickness on the sheet exceeds 5 cm, due to the excessively thick thickness, the polymerization reaction is carried over the entire thickness. It may not happen evenly.

In this case, the water content of the hydrogel polymer obtained by the above method may be about 40 to about 80% by weight. On the other hand, the "water content" as used throughout the specification means the value of the moisture content of the total water-containing gel-like polymer is the weight of the water-containing gel polymer minus the increase in the dry polymer. Specifically, it is defined as a value calculated by measuring the weight loss according to the water vaporization of the evaporator during the process of drying the temperature of the evaporator through infrared heating. At this time, the drying conditions are raised to about 1 80 ^° C at room temperature and then maintained at 180 ^° C. The total drying time is set to 20 minutes, including 5 minutes of temperature rise step, the water content is measured.

 Next, the step of drying the obtained hydrogel polymer is carried out.

 At this time, if necessary to coarse grinding before drying to increase the efficiency of the drying step may be more rough.

At this time, the pulverizer used is not limited in configuration, but specifically, a vertical pulverizer, a turbo cutter, a turbo grinder, a rotary cutter, and a rotary cutter. mi ll), cutter mi ll, It may include any one selected from a group of crushing machines consisting of a disc crusher, a shred crusher, a crusher, a chopper, and a di sc cutter. However, it is not limited to the example mentioned above.

 In this case, the coarsely pulverizing step may be pulverized so that the particle size of the hydrogel polymer is about 2 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 milled particles cross each other. On the other hand, in the case where the particle size is pulverized more than 10 mm 3, the effect of increasing the efficiency of the subsequent drying step may be minimal.

As described above, drying is performed on the hydrous gel polymer immediately after the coarse grinding or the black is not subjected to the coarse grinding step. At this time, the drying temperature of the drying step may be about 150 to about 250 ^° C. If the drying temperature is less than 150 ^° C, the drying time may be too long and the properties of the final superabsorbent polymer may be lowered. If the drying temperature exceeds 250 ^° C, only the polymer surface is dried excessively. Fine powder may generate | occur | produce in the post grinding process, and there exists a possibility that the physical property of the superabsorbent polymer formed finally may fall. Thus, preferably, the drying may be carried out ^at a temperature of about 150 to about 200 ^° C, more preferably at a temperature of about 160 to about 180 ^° C.

On the other hand, in the case of drying time, in consideration of the process efficiency, etc., it may proceed for about 20 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, it can be selected and used without limitation of the configuration. Specifically, the drying step may be performed by a method such as hot air supply, infrared irradiation, microwave irradiation, or ultraviolet irradiation. The water content of the polymer after the drying step may be about 0.1 to about 10% by weight.

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

The polymer powder obtained after the milling step may have a particle diameter of about 150 to about 850 mm 3. The mill which particle size is used to crush the same specifically, pin mill (pin mill), a hammer mill (hammer mill), switch ^'keuryu mill (screw mi 11), a roll mill (roll mill), disc mill (disc mill ) Or a jog mill, etc., but the present invention is not limited to the above examples.

 In addition, in order to manage the physical properties of the super absorbent polymer powder to be finalized after such a grinding step, the polymer powder obtained after grinding may be subjected to a separate process of classifying according to the particle size. Preferably, the polymer having a particle size of about 150 to about 850 / m may be classified, and only a polymer powder having such a particle size may be produced through a surface crosslinking reaction step.

 Next, a surface crosslinking reaction is performed by adding a compound represented by the following formula (1) and a polyvalent metal cation to the ground polymer.

[Formula 1] Rr (CH ₂ ) _n -R ₂

 In Chemical Formula l,

And R ₂ is the same or different and is each independently a hydroxyl group, an amine group, an epoxide group or an isocyanate group;

 n is an integer of 1-3.

 Surface crosslinking is the step of increasing the crosslink density near the surface of the superabsorbent polymer particles with respect to the crosslink density inside the particles. Generally, the surface crosslinking agent is applied to the surface of the super absorbent polymer particles. Thus, this reaction occurs on the surface of the superabsorbent resin particles, which improves the crosslinkability on the surface of the particles without substantially affecting the interior of the particles. Thus, surface crosslinked superabsorbent polymer particles have a higher degree of crosslinking in the vicinity of the surface than in the interior.

 According to the present invention, the surface crosslinking agent includes a compound represented by the following Formula 1 and a polyvalent metal cation. Compounds represented by the following formula (1) and polyvalent metal cations may be used alone or in combination of two or more materials.

 [Formula 1]

 In Chemical Formula 1,

And ¾ are the same or different and each independently represent a hydroxyl group, an amine group, Epoxide group or isocyanate group;

 n is an integer of 1-3.

 According to the present invention, by adding a polyvalent metal cation as the surface crosslinking agent, the crosslinking distance can be further reduced by forming a chelate with the carboxyl group (C00H) of the superabsorbent polymer.

According to one embodiment of the invention, the δ _ρ it defined by the Hansen solubility parameters _{δ ρ <11 (J / cm} 3) The material and δ _Η satisfying _{^{172 δ Η <4.5 (J /}} cm 3) 1 / ^The surface crosslinking reaction may be performed by further adding one or more materials selected from the group consisting of two satisfying materials.

Examples of the material satisfying δ _ρ <ll (J / cm ³ ) ^1/2 include 1,6-nucleic acid diol, propylene glycol, 1,2-nucleic acid di, 1,3-butanediol, 2-methyl-1, 3-propanediol, 2,5-nucleic acid di-, 2-methyl-1,3-pentanediol, or 2-methyl-2,4-pentanediol, and the above δ _Η <4.5 (J / cm ³ ) Substances satisfying ^1/2 include 1,2-propylene carbonate. However, the present invention is not limited thereto, and as long as the substance satisfies the range of the parameter, a substance not shown in Table 2 may be used.

The Hansen solubility parameter was proposed by Charles Hansen as a method of predicting when one substance is dissolved in another to form a solution. This is for example INDUSTRIAL SOLVENT S HANDBOOKj (published by pp. 35-68, Marcel Dekker, Inc., 1996) or "() I RECTORY OF SOLVENTSj (pp.22-29, Blackie Academic & Professional, 1996). Etc Parameters described in.

 Generally, in order to calculate the solubility parameter, the cohesive energy must be obtained. In the Hansen solubility parameter, the cohesive energy affecting the solubility constant is classified into three categories.

δ ₀ : Solubility constant due to nonpolar dispersion energy (Unit: (J / cm ³ ) ^1/2 ) δ _Ρ : Solubility constant due to dipole polar energy (Unit: (J / cm ³ ) ^1/2 ) δ _Η : Solubility constant due to hydrogen bonding energy (Unit: (J / cm ³ ) ^1/2 )

5 _tot : ((δ ₀ ) ² + (δ _Ρ ) ² + (δ _Η ) ² ) ^1/2

By obtaining the above parameters, the similarity of the solubility of the two substances can be calculated by the difference of the Hansen solubility parameter of the two substances. For example, for the two ^' materials of A and B, each Hansen solubility parameter value is A for each (S _D ^A , δ _Ρ ^Α , δ _Η ^Α ) ᅳ Β (δΛ δ _Ρ ^Β , δ _Η Assuming that ^Β ), the difference (Ra) between the Hansen solubility parameter values of the two materials can be calculated by the following equation.

Ra = (4 * (5 _D ^A ᅳ δ _D ^B ) ² + (δ P ^A -δ _Ρ ^Β ) ² + (δ _Η ^Α -δ _Η ^Β ) ² ) ¹⁷²

 The higher the Ra value, the lower the similarity between the two in terms of solubility.

For some materials that can be used as crosslinkers, A HSPiP (Hansen Solubility Parameters in Practice, 3 rd edition version 3.1 published by Hansen-Solubility.com) the Hansen solubility calculated based on the program parameters values developed by Hansen group are as shown in Table 2 below. Table 2

According to an embodiment of the present invention, in addition to the surface crosslinking agent, porous inorganic materials such as silica, clay, alumina, silica-alumina composite, nanosilica, titania, zinc oxide, aluminum cellulose, etc. It can be added to carry out the surface crosslinking reaction. The porous inorganic material may be used in powder form or in liquid form, and in particular, may be used as alumina powder, silica 미나 alumina powder, titania powder, or nanosilica solution. In addition, the porous inorganic material may be included in an amount of about 0.05 to about 2% by weight relative to the monomer composition, preferably 0.08 to 0.18% by weight (wt%), more preferably used in 0.1 to 0.15% by weight Can be. There is no limitation in the structure about the method of adding the said surface crosslinking agent to a built-in body. The surface crosslinking agent and the polymer powder may be mixed in a semi-permanent mixture, or the surface crosslinking agent may be sprayed onto the polymer powder, or the polymer and surface crosslinking agent may be continuously supplied to the mixer to be mixed and mixed.

 When the surface crosslinking agent is added, water and methane may be further mixed and added together. When water and methanol are added, there is an advantage that the surface crosslinker can be evenly dispersed in the polymer. At this time, the content of water and methane added is added to 100 parts by weight of polymer for the purpose of inducing even dispersion of the surface crosslinking agent and preventing aggregation of the polymer powder and optimizing the surface penetration depth of the crosslinking agent. It can be applied by adjusting the rate.

The surface crosslinking reaction may be achieved by heating the polymer particles to which the surface crosslinking agent is added at about 160 ^° C. for at least 20 minutes. In particular, the surface crosslinking process conditions of the present invention can be carried out while maintaining a maximum reaction temperature 190 to 200 ^° C, a total reaction time 0.5 to 1 hour, a reaction temperature of 160 ^° C or more 25 minutes or more. 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, or hot oil may be used, but the present invention is not limited thereto, and the temperature of the heat medium to be supplied is a means of heating medium, a rate of temperature increase, and a temperature increase. It may be appropriately selected in consideration of the target temperature. On the other hand, the heat source directly supplied may be a method of heating by electricity or heating by gas. However, the present invention is not limited to the above examples. In addition, before or after the surface cross-linking reaction may be carried out to include a step of cross-linking, or before or after the surface cross-linking reaction may include a step of mixing the cross-linked inorganic (inorgani c) material. In general, a method of mixing silica in a dry manner is carried out by injecting a silica powder into a plastic bag in a powdered product and shaking it from side to side to obtain a dry product easily. In the commercial process, silica-dried products can be obtained by quantitatively injecting silica in the process of rapidly stirring the stirring shaft with paddles capable of mixing the powder in the process of flowing the product onto the line. As described above, the superabsorbent polymer obtained according to the preparation method of the present invention may have improved fluid permeability without deteriorating physical properties such as water-retaining capacity and pressure-absorbing capacity, and may exhibit a fast absorption rate under pressure. In the present invention, matters other than those described above can be added or subtracted as necessary, and therefore the present invention is not particularly limited.

 Effect of the Invention According to the present invention, centrifugal water-retaining capacity (CRC) and pressure-absorbing capacity

By simultaneously optimizing (AUL) and gel bed permeability (GBP) to excellent ranges at the same time, it is possible to improve the physical properties of the final diaper, thereby producing a basal ear to which ultra-thin technology is applied.

_. In particular, the superabsorbent polymer of the present invention can be applied to the production of hygiene products having a comfortable and comfortable fit due to a small amount of moisture (content of rewet ting) that is cut off even after a certain time. [Brief Description of Drawings]

 1 is a schematic diagram showing an example of an apparatus for measuring the pressure absorption rate for the super absorbent polymer according to one embodiment of the present invention.

 2 is a schematic diagram showing an example of a gel bed permeability (GBP) measuring apparatus according to an embodiment of the present invention, Figure 3 and Figure 4 is an example of the gel bed permeability measurement cylinder and mesh arrangement, respectively It is a schematic diagram showing.

 [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.

Example 1

In a 2 L glass reactor surrounded by a jacket in which a heat medium pre-cooled to 25 ^° C. was circulated, 500 g of acrylic acid was mixed with 11 g of 0.5% IRGACURE 819 initiated with acrylic acid (110 ppm for the monomer composition), Inject 26 g of 5% polyethylene glycol diacrylate (PEGDA, molecular weight 400, Cure Dose 200 mJ / cm ² ) diluted in acrylic acid into a mixed solution (A solution), and 5% ethylene oxide diluted in acrylic acid 9 mol% trimethyl containing propane triacrylate (Ethoxyl ated-TMPTA, TMP (E0) 9TA, M-3190 Miwon Specialty Chemicals, Cure Dose 200 mJ / cm ² ) 14 g mixed solution (B solution) Was added and 800 g (C solution) of 24% caustic soda solution was slowly added dropwise to mix. Soluble from sodium acrylate as the water-soluble ethylenically unsaturated monomer thus obtained Krylic acid neutralization was 70 mol%.

After confirming that the temperature of the mixture rises above 80 ^° C due to the heat of neutralization during the mixing of the two solutions, wait for the silver to be reduced to 40 ^° C and then dilute in water when the reaction reaches 40 ^° C. 54 g of sodium persulfate solution were injected.

The solution was poured into a Vat-shaped tray (15 cm x 15 cm) mounted in a square polymerizer equipped with a light irradiation device on the top and preheated to 80 ^° C., and photo-initiated by light irradiation. After about 25 seconds of light irradiation, the gel is generated from the surface, and after 50 seconds, the polymerization reaction occurs at the same time as the foaming. After cutting, a chopping process was performed using a meat chopper to prepare a powder.

The crumb was dried in Aubonn, which was capable of transferring air volume up and down. The hot air ^at 18 0 ^° C was dried uniformly by flowing 15 minutes downwards and upwards and 15 minutes upwards and downwards, and after drying, the water content of the dried body was 2% or less.

 After drying, the resultant was pulverized with a grinder and classified to prepare a base resin by selecting 150 to 850 sizes. The water-retaining capacity of the base resin thus prepared was 36.5 g / g, and the content of aqueous pen was 12.5 weight ¾>.

After, 100 g of water in the base resin 3 g, methanol, 3 g, 1, 3 propane dieul 0.3 g, Aerosil 200 (aerosol 200) 0. 1 g in a common cross-linker solution after the combined common and combined 190 ^° C The surface crosslinking reaction for 30 minutes, using a sieve after grinding to obtain a surface-treated superabsorbent polymer having a particle size of 150 ~ 850 卿.

 Silica dry-treated samples were prepared by mixing 0.08 g of Aerosil 200 in a dry manner to the obtained 100 g surface-treated superabsorbent polymer. Example 2

Super absorbent polymer was prepared in the same manner as in Example 1, except that 0.2 g of ^' cerite (Ceiite) was used in place of the aerosol 200 used in the dry process. Example 3

For the base resin obtained in Example 1, 3 g of water, 1.0 g of ethylene carbonate, and 0.1 g of aerosil 200 were mixed with 100 g of the base resin in a surface crosslinking treatment. Subsequently, surface crosslinking reaction was carried out at 190 ^° C. for 30 minutes, and after grinding, a sieve was used to obtain a surface-treated superabsorbent polymer having a particle size of 150 to 850 jm. Others manufactured the high water absorbing resin in the same manner as in Example 1. Example 4

The base resin obtained in Example 1 was subjected to a surface crosslinking treatment. A super absorbent polymer was prepared in the same manner as in Example 1, except that 3 g of water, 1.0 g of 1,3-propanedi and 0.5 g of propylene glycol were used relative to 100 g of the base resin. Example 5

In performing the same polymerization as in Example 1, a solution (A solution) containing 33 g of 5% polyethylene glycol diacrylate (PEGDA, molecular weight 400, Cure Dose 200 mJ / cm ² ) diluted in acrylic acid was injected as an internal crosslinking agent. Then, 3 g of 5% hexanediol diacrylate (HDDA, Hexanedi ol diacrylate, Cure Dose 320 mJ / cm ² ) diluted in acrylic acid was injected with a mixed solution (B solution). The water holding capacity of the base resin thus obtained was 37.2 g / g. Thereafter, the surface cross-linking treatment was performed in the same manner as in Example 3. Comparative Example 1

For example, an internal crosslinking agent was used as a single component, and a base was prepared by mixing 55 g of 5% polyethylene glycol diacrylate (PEGDA, molecular weight 400, Cure Dose 200 mJ / cm ² ) diluted in the acrylic acid-containing solution (A solution). It was. The water retention capacity of the base resin thus obtained was 36.2 g / g. Other surface treatment procedures were prepared in the same manner as in Example 1. Comparative Example 2 For example, an internal crosslinking agent is used as a single component, and 5% polyethylene glycol diacrylate (PEGDA, molecular weight 400, Cure Dose 200 mJ / cm ² ) is not used in the acrylic acid-containing solution (A solution), and diluted 5% ethylene oxide is used. 38 g of trimethylolpropane triacrylate (Ethoxyl ated-TMPTA, TMP (E0) 9TA, M-3190 US Specialty Chemical, Cure Dose 200 mJ / cm ² ) containing 9 mol Solutions) were combined. The water holding capacity of the base resin thus obtained was 33.2 g / g. Other surface treatment process was prepared in the same manner as in Example 1 superabsorbent polymer. Comparative Example 3

5% polyethyleneglycol diacrylate (PEGDA, molecular weight 400, Cure Dose 200 mJ / cm ² ) diluted in the acrylic acid-containing solution (A solution) was mixed at 55 g and 5 g of D-sorbetle was added at the same time. Except that a high water-absorbent resin was prepared in the same manner as in Comparative Example 1. The water holding capacity of the base resin thus obtained was 35.5 g / g. Comparative Example 4

In the same polymerization as in Example 1, a solution (A solution) containing 26 g of 5% polyethylene glycol diacrylate (PEGDA, molecular weight 400, Cure Dose 200 mJ / cm ² ) diluted with an internal crosslinking agent was injected. , Trimethylolpropane triacrylate containing 5 mol% of diluted 5% propylene oxide (Propoxyl ated-TMPTA, TMP (P0) 5TA, Miwonspae 16 g of Shirty Chemical, Cure Dose 490 mJ / cm ² ) were injected with a mixed solution (B solution). The water holding capacity of the base resin thus obtained was 38.4 g / g. Thereafter, the surface cross-linking treatment was performed in the same manner as in Example 1.

Comparative Example 5

In the same polymerization as in Example 1, a solution (A solution) mixed with 26 g of 5% polyethylene glycol diacrylate (PEGDA, molecular weight 400 and Cure Dose 200 mJ / cm ² ) distilled with an internal crosslinking agent was injected. Then, 12 g of dilute 5% pentaerythritol tetraacrylate (PETTA, Miwon Specialty Chemicals, Cure Dose 158 m J / cm ² ) was mixed with a solution (B solution). Injected. The water holding capacity of the base resin thus obtained was 34.3 g / g. Thereafter, the surface cross-linking treatment proceeded in the same manner as in Example 1.

Test Example

 Evaluation of physical properties of the superabsorbent polymers prepared according to Examples 1-5 and Comparative Examples 1 to 5 was carried out in the following manner, and the measured physical properties are shown in Table 3 below.

(1) particle size evaluation

Of the base polymer and the super absorbent polymer used in Examples 1-5 and Comparative Examples 1-5 Particle size was measured according to the European Disposables and Nonwovens Association (EDANA) standard EDANA WSP 220.2 method.

(2) Centrifuge Retention Capacity (CRC)

 European Disposables and Nonwovens Association, E

DANA) With respect to the water absorbent resins of Examples 1-5 and Comparative Example 1-5 according to the standard EDANA WSP 241.2, the water-retaining capacity by the unloaded absorption ratio was measured.

That is, after the resin W ₀ (g, ^' about 0.2g) obtained in Example 1-5 and Comparative Example 1-5 was uniformly sealed in a non-woven bag and sealed, 0.9 mass% of physiological saline was added to the silver. Flooded in. After 30 minutes, the envelope was centrifuged and drained at 250 G for 3 minutes, and then the mass W ₂ (g) of the envelope was measured. In addition, after performing the same operation without using resin, the mass Kg at that time was measured.

 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)-W ₁ (g)] / W ₀ (g)>-1

 In the above formula 1,

W ₀ (g) is the weight of the absorbent resin (g),

Kg) is the weight of the device measured after dehydration at 250G for 3 minutes using a centrifuge, without using a water absorbent resin, W ₂ (g) is the device weight measured after absorbing the absorbent resin in 0.9 mass% physiological saline at room temperature for 30 minutes, followed by dehydration at 250 G for 3 minutes using a centrifuge. (3) Absorbency under Load (AUL)

 For the superabsorbent polymers of Examples 1-5 and Comparative Examples 1-5, Absorbency under Load (AUL) of 0.9 psi was measured by the following method.

First, a stainless steel 400 mesh wire was mounted on the bottom of a plastic cylinder having an inner diameter of 25 画. The resin W ₀ (g, 0. 16 g) obtained in Example 1-7 and Comparative Example 1-4 was uniformly sprayed on a wire mesh under conditions of a room temperature and a humidity of 50%, and 5. 1 kPa (0.9 ps i) thereon. Piston, which can give more uniform load, has an outer diameter of less than 25 醒 and is not equal to the inner wall of the cylinder. At this time, the weight W ₃ (g) of the apparatus was measured.

 A glass filter having a diameter of 90 mm and a 5 mm thick glass filter was placed inside the petri dish having a diameter of 150 mm 3, and the physiological saline consisting of 0.90 wt% sodium chloride was made at the same level as the upper surface of the glass filter. One sheet of filter paper 90 mm in diameter was loaded thereon. The measuring device was placed on the filter paper and the liquid was absorbed for 1 hour under load.

After 1 hour, the measuring device was lifted and the weight W ₄ (g) was measured.

Using each mass thus obtained, AUL (g / g) was calculated according to the following equation 2 to confirm the pressure absorbing ability. [Calculation 2]

AUL (g / g) = [W ₄ (g) _-3 (g)] / W ₀ (g)

 In the formula 2,

W ₀ (g) is the weight of the absorbent resin (g) ，

W ₃ (g) is the sum of the weight of the absorbent resin and the weight of the device capable of applying a load to the absorbent resin,

W ₄ (g) is the sum of the weight of the absorbent resin absorbed by the moisture after supplying the absorbent resin for 1 hour under a load (0.9 psi) and the weight of the device capable of applying a load to the absorbent resin.

(4) Gel Bed Permeability (GBP)

 For the superabsorbent polymers of Examples 1-5 and Comparative Examples 1-5, Gel Bed Permeability (GBP) was measured. The GBP measurement method is specified in US Pat. No. 7,179,851.

In particular, the superabsorbent polymer according to the present invention exhibits certain properties or characteristics when measuring free swell gel bed permeability (GBP), gel bed permeability under load ("0.3 GBP"). The free swelling gel bed permeability test is a different measurement of the permeability of a swelling bed of superabsorbent material (eg, separation from an absorbent structure) under specified pressure, after a state usually referred to as a "free swelling" state. "Free flow"'means that the superabsorbent material swells without the swelling inhibition upon absorption of the test solution. will be. The gel bed permeability under load ("0.3 GBP") is obtained by bringing the superabsorbent polymer composition to a "prescribed pressure state of about 0.3 psi" followed by gel particles (e.g., superabsorbent or absorbent material as used herein). Means the transmittance of the swelling bed. Free Swelling Gel Bed Permeation (GBP) Test

First, the free swell gel bed permeability (GBP) test is performed under swelling of gel particles (e.g., surface treated absorbent material or superabsorbent material prior to surface treatment) under conditions commonly referred to as "free swelling" conditions. The transmission of the bed is measured. "Free swelling"'will be described as allowing the gel particles to swell without limiting load upon absorption of the test solution. "Free swelling"' will mean that the superabsorbent polymer has no swelling limiting load upon absorption of the test solution. It will be described as causing swelling. Suitable apparatus for performing the transmittance test are shown in FIGS. 3 and 4, and generally indicated as 28 in FIG. 3. Test apparatus 28 includes a sample vessel (typically labeled 30) and a piston (typically labeled 36). The piston 36 includes a cylindrical LEXANR shaft 38 having a central cylindrical hole 40 drilled below the longitudinal axis of the shaft. Both ends of the shaft 38 are machined to provide the upper and lower ends (indicated by 42 and 46, respectively). The increase (indicated by 48) is above one end 42 and has a cylindrical hole 48a drilled through at least a portion of its center. The circular piston head 50 is located above the other end 46, with an enlarged inner ring of seven holes (60, each of which has a diameter of about 0.95 cm) and fourteen holes (54, each of them). Angle is about 0.95 cm in diameter). The holes 54 and 60 are drilled from the top to the bottom of the piston head 50. The piston head 50 also has a cylindrical hole 62 drilled in its center to receive the end 46 of the shaft 38. The lower part of the piston head 50 may also be covered with a biaxially stretched 400 mesh stainless steel screen 64 ^' .

 The sample vessel 30 includes a cylinder 34 and a 400 mesh stainless steel skinned screen 66, which is taut biaxially stretched and attached to the lower end of the cylinder. The superabsorbent polymer sample (designated 68 in FIG. 3) is supported on the screen 66 inside the cylinder 34 during the test.

The cylinder 34 may be perforated with a transparent LEXANR rod or equivalent material or cut into a lexan tube or equivalent material, having an internal diameter of about 6 cm (eg, a cross-sectional area of about 28.27 _cm ² ) and a wall thickness of about It is 0.5 cm high and about 10 cm high. A drain hole (not shown) is formed in the sidewall of the cylinder 34 at a height of about 7.8 cm above the screen 66 to drain the liquid from the cylinder, so that the fluid level in the sample vessel at about 7.8 cm above the screen 66. Keep it. The piston head 50 is machined from a lexan rod or equivalent material and has a height of approximately 16 mm and a diameter of a predetermined size so that it still slides freely while fitting it to the minimum wall space inside the cylinder 34. The shaft 38 is machined from a lexan rod or equivalent material and has an outer diameter of about 2.22 cm and an inner diameter of about 0.64 cm.

The shaft upper end 42 is approximately 2.54 cm in length and approximately 1.58 cm in diameter. As a result, the annular slad 47 is formed to support the weight 48. The annular weight 48 is about 1.59 cm in internal diameter, so that it slips over the upper end 42 of the shaft 38 and is present on the annular shoulder 47 formed thereon. The annular extender 48 may be made of stainless steel or made of a corrosion resistant adult suitable material in the presence of a test solution that is 0.9 wt% sodium chloride in distilled water. The combined weight of the piston 36 and the annular weight 48 corresponds to approximately 596 g, which means that the pressure applied to the absorbent structure sample 68 is about 0.3 ps i or about 20.7 g / for a sample area of about 28.27 cm ² . It is said to be cm ² .

 When the test solution is flowed into the test apparatus during the test described below, the sample vessel 30 generally remains on a 16 mesh rigid stainless steel support screen (not shown): or the sample vessel 30 In order not to limit the flow from the bottom of the vessel, it rests on a support ring (not shown) having a diameter size substantially the same as the cylinder 34.

To perform the gel bed permeability test under “free swelling” conditions, a piston 36 with a weight 48 disposed thereon is placed in the hollow sample vessel 30 and a cylinder 34 from the bottom of the weight 48. The height up to the top of the c) is measured with a caliper with suitable measurement accuracy up to 0.01 mm. When using multiple test apparatus, it is important to measure the hollow height of each sample vessel 30 and to keep track of which piston 36 and weight 48 have been used. The same piston 36 and extension 48 should be used for the measurement when the superabsorbent polymer sample 68 is water swelled after saturation. The sample tested is made from superabsorbent material particles, which are prescreened through a US standard 30 mesh screen and held on a US standard 50 mesh screen. Thus, the test sample contains particles in the size range of about 300 to about 600. The particles can be prescreened manually or automatically. About 2.0 g of sample was placed in sample vessel 30, and then in the absence of piston 36 and weight 48, the vessel was immersed in the test solution for a period of about 60 minutes to saturate the sample and swell the sample without limiting load. All.

 At the end of this period, the piston 36 and weight 48 are placed over the saturated sample pool 68 of the sample vessel 30 and then the sample vessel 30, the piston 36, the weight 48 and the sample. (68) is removed from the solution. The thickness of the saturating sample 68 is re-established from the bottom of the weight 48 to the top of the cylinder 34, using the same clipper or meter (where the zero does not change from the initial height measurement) used previously. Is determined by. The height measurement obtained by the measurement of the hollow sample vessel 30, the piston 36 and the height 48 is subtracted from the height measurement obtained after saturation of the sample 48. The value obtained is the thickness or height ("H") of the swelling sample.

Permeability measurements are initiated by delivering a flow of test solution to a sample vessel 30 having a saturated sample 68, a piston 36, and a weight 48 therein. Adjust the flow rate of the test solution to the vessel to maintain a fluid height of about 7.8 cm above the bottom of the sample vessel. The amount versus time of solution passing through sample 68 is determined gravimetrically. The data point is maintained when the fluid level is stabilized at a height of about 7.8 cm Collect every second for more than 20 seconds. The flow rate (Q) through the swelling sample (68) is measured in g / s by a linear least squares approximation of fluid (g) versus time (seconds) through the sample 68.

 The transmittance (darsi) is calculated according to the following equation (3).

 [Calculation 3]

 K = [Q x H xMu] / [AxRho xP]

In Equation 3, K is the transmittance (cm 2), Q is the flow rate (g / speed), H is the height of the sample (cm), and Mu is the liquid viscosity (poi se) (the test solution used in the test Approximately 1 cps), A is the cross-sectional area for liquid flow (cm ² ), Rho is the liquid density (g / cm ³ ) (for the test solution used in the test), and P is hydrostatic pressure (dynes / cm ² ) (typically about 3, 923 dynes / cm ² ). The hydrostatic pressure is calculated from the following equation (4).

 [Calculation 4]

 P = Rho X g xh

In Equation 4, Rho is the liquid density (g / cm ³ ), g is the weight acceleration, typically 981 cm / sec ² , h is the fluid height (eg 7.8 cm for the permeability test described herein). )to be. Gel bed transmittance test under load

Testing gel bed permeation under load (or denoted as GBP at 0.3 ps i) is typically performed by gel particles (eg, The transmittance of the swelling bed of the superabsorbent material or absorbent material as used in the circle is measured. The term "loading" means that the swelling of the particles is limited by the loading that normally matches the normal working load (eg, sitting, walking, bending, etc.) applied to the particles by the wearer.

 More specifically, the gel bed permeation test under load is substantially the same as the free swelled gel bed permeability test described previously, except for the following. About 2.0 g of sample is placed in the sample vessel 30, uniformly dispersed in the bottom of the sample vessel, the piston 36 and the weight 48 are placed on the sample inside the sample vessel, and then the sample vessel (the piston and weight inside Submerged) in a test solution (0.9 wt% NaCl saline) for about 60 minutes. As a result, a 0.3 psi limit load is applied to the sample as the sample saturates and swells.

(5) Pressurized absorption speed

 For the superabsorbent polymers of Examples 1-5 and Comparative Examples 1-5, the pressure absorption rate (Strike thru timeime under load, the welding rate of SAP under load) was measured by the following method.

First, as shown in FIG. 1, a cylinder (cyl inder, w / oring: Mesh # 400), a plunger (plunger, Mesh # 100), and a weight (weight, 0.3 psi) were used. The test apparatus used was a free swelled gel bed permeability (GBP) test equipment shown in FIG. The weight used was 2.07 kPa (0.3 psi) In order to give more load evenly, there is no inner wall of the outer cylinder and the movement of the upper and lower sides is not disturbed. In addition, the mandarin paper (What man paper 4) was laid on the bottom of the cylinder of the device, the superabsorbent resin was weighed and evenly spread by 2 g. Subsequently, raise the plunger (p lunger), apply a 0.3 psi weight (load, load), and then 10 mL of 0.9% salt ine solut ion set to 22 ^' C in the plunger ho le. Pour the water, and measure the time that the brine seen through the hole of the plunger disappears completely. Repeat this three times at 5 minute intervals, 10 mL each for the 1st, 2nd, and 3rd times, respectively. We measured the time (in seconds, sec) that the brine disappeared.

Table 3

As shown in Table 3, the superabsorbent polymer of Example 1-5 according to the present invention exhibits improved fluid permeability, water retention, and pressure absorption ability as compared to Comparative Example 1-5, and has quick absorption characteristics under pressure. And excellent absorbency, and can produce diapers and the like to which ultra-thin technology is applied.

Claims

[Patent Claims]

 [Claim 1]

 A base resin in the form of a powder obtained by polymerizing a water-soluble ethylenically unsaturated monomer including an acidic group and at least partially neutralized with two or more internal crosslinking agents, and a crosslinked polymer obtained by surface crosslinking with a diol or a glycol compound having 2 to 8 carbon atoms, More than 28 g / g centrifugal water retention (CRC), more than 0.9 gs g of pressure-absorbing capacity (AUL) of 18 g / g, gel bed permeability (GBP) of 45 darcy or greater, 0.9 weight ¾> Superabsorbent resin with a pressurized absorption rate of 0.3 ps i of 30 to 200 seconds in the third injection into brine.

 [Claim 2]

 The method of claim 1,

 The pressure absorption rate of the 0.3 ps i, the physiological at the third injection when 0.95% by weight of 5 to 70 mL of 0.9% by weight saline solution at intervals of 1 to 20 minutes Superabsorbent resin, measured by the rate of absorption in saline.

 [Claim 3]

 The method of claim 1,

The water-soluble ethylenically unsaturated monomers are acrylic acid, methacrylic acid, maleic anhydride, fumaric acid, crotonic acid, itaconic acid, 2-acryloylethane sulfonic acid, 2'methacryloyl ethanesulfonic acid, 2- (meth) acrylo Anionic monomers of monopropanesulfonic acid or 2- (meth) acrylamide-2-methyl propane sulfonic acid and salts thereof; (Meth) acrylamide, N-substituted Nonionics of (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, methoxypolyethylene glycol (meth) acrylate or polyethylene glycol (meth) acrylate Hydrophilic containing monomers; And amino group-containing unsaturated monomers of (Ν, Ν) -dimethylaminoethyl (meth) acrylate or (Ν, Ν) -dimethylaminopropyl (meth) acrylamide and their quaternized compounds; at least one member selected from the group consisting of Super absorbent resin comprising a.

 [Claim 4]

 According to claim 1,

 The two or more internal crosslinking agents each have a cure dose of from 0.16 to 0.35 J / cui '.

 [Claim 5]

 The method of claim 4,

 The two or more internal crosslinking agent is a super absorbent polymer selected from the group consisting of polyfunctional acrylate compounds each having a plurality of ethylene oxide groups.

 [Q. Port 6]

 The method of claim 5,

The polyfunctional acrylate compound having a plurality of alkylene oxide groups is polyethylene glycol diacrylate Uyethyl enegl y acyl di acrylate PEGDA), ethoxylated trimethylolpropane triacrylate (Ethoxyl ated-TMPTA), nucleic acid didiadia Selected from the group consisting of acrylate and triethylene glycol diacrylate Superabsorbent polymer.

 [Claim 7]

 The method of claim 1,

 The centrifugal water retention capacity (CRC) is a super absorbent polymer represented by the following formula 1:

 [Calculation 1]

CRC (g / g) = {(W ₂ (g)-WM l / WoCg))-1

 In the above formula 1,

W ₀ (g) is the weight of the absorbent resin (g) ，

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

W ₂ (g) is the device weight measured after absorbing the water absorbent resin in 0.9 mass% physiological saline at room temperature for 30 minutes, followed by dehydration at 250 G for 3 minutes using a centrifuge.

 [Claim 8]

 The method of claim 1,

 Pressurized absorbent capacity of 0.9 psi (AUU is a super absorbent polymer represented by the following formula 2:

 [Calculation 2]

AUL (g / g) = [W ₄ (g)-W ₃ (g)] / W ₀ (g) In the formula 2,

W ₀ (g) is the weight (g) of the absorbent resin.

W ₃ (g) is the sum of the weight of the absorbent resin and the weight of the device capable of applying a load to the absorbent resin,

W ₄ (g) is the sum of the weight of the absorbed water absorbed resin after supplying the absorbent resin with water for one hour under a load (0.9 ps i) and the weight of the device capable of applying a load to the absorbent resin.

 [Claim 9]

 A monomer composition comprising an acidic group and at least partially neutralized with a water-soluble ethylenically unsaturated monomer, two or more internal crosslinking agents having a cure dose of 0.1 to 0.35 J / cuf, a photopolymerization initiator, and a thermal polymerization initiator. Thermal polymerization and photopolymerization to form a hydrogel polymer;

 Drying the hydrogel polymer; Pulverizing the dried polymer; And

 Performing a surface crosslinking reaction by adding a compound represented by Chemical Formula 1 and a polyvalent metal cation to the pulverized polymer;

 Method for producing a super absorbent polymer comprising a.

 [Formula 1]

In Chemical Formula 1, Ri and ¾ are the same or different and each independently represent a hydroxyl group, an amine group, an epoxide group or an isocyanate group;

 n is an integer from 1 to 3.

 [Claim 10]

 The method of claim 9,

 The internal crosslinking agent is a method for producing a super absorbent polymer, which is contained in an amount of 0.05 to 3% by weight based on the monomer composition.

 [Claim 11]

 The method of claim 9,

 The method for producing a super absorbent polymer, wherein the two or more internal crosslinking agents are selected from the group consisting of polyfunctional acrylate compounds each having a plurality of ethylene oxide groups.

 [Claim 12]

 The method of claim 11,

 remind. Polyfunctional acrylate compounds having a plurality of alkylene oxide groups include polyethylene glycol diacrylate Oyethyleneglycol di acrylate PEGDA, ethoxylated trimethyl, propane triacrylate, hexanedidiadia acrylate, and triethylene. A method for producing a super absorbent polymer, which is selected from the group consisting of glycol diacrylates.

[Claim 13] The method of claim 9,

 The photopolymerization initiator is a method for producing a super absorbent polymer is contained in 40 to 200 ppm relative to the monomer composition.

 [Claim 14]

 The method of claim 9,

 The thermal polymerization initiator is a method for producing a super absorbent polymer containing from 0.05 to 0.3% by weight relative to the monomer composition.

 [Claim 15]

 The method of claim 9,

 The thermal polymerization initiator is a persulfate compound containing sulfur, a method for producing a super absorbent polymer

 [Claim 16]

 The method of claim 9

 A water-soluble ethylenically unsaturated monomer containing the acidic group and at least partially neutralized has a neutralization degree of 50 mol% or more with respect to the acidic group. [Claim 17]

 The method of claim 9,

 The surface cross-linking reaction is carried out by the addition of a porous inorganic material in addition to a method for producing a super absorbent polymer.