WO2017171208A1

WO2017171208A1 - Superabsorbent resin and method for producing same

Info

Publication number: WO2017171208A1
Application number: PCT/KR2017/000054
Authority: WO
Inventors: 이혜민; 서성종; 윤형기
Original assignee: 주식회사 엘지화학
Priority date: 2016-03-31
Filing date: 2017-01-03
Publication date: 2017-10-05

Abstract

The present invention relates to a superabsorbent resin exhibiting more improved liquid permeability while maintaining excellent absorption performance, and a method for producing the same. The superabsorbent resin comprises: a base resin powder comprising a first crosslinked polymer of a water-soluble ethylenically unsaturated monomer having at least partially neutralized acidic groups; and a surface crosslinked layer formed on the base resin powder and comprising a second crosslinked polymer in which the first crosslinked polymer is further crosslinked through an alkylene carbonate having two to five carbon atoms. The superabsorbent resin satisfies predetermined physical properties.

Description

【Specification】

[Name of invention]

Super Absorbent Resin and Method for Making the Same

Technical Field

Cross Citation with Related Application (s)

This application claims the benefit of priority based on Korean Patent Application No. 10-2016-0039244 dated March 31, 2016 and Korean Patent Application No. 10-2016-0063524 dated May 24, 2016. All content disclosed in the literature is included as part of this specification.

The present invention relates to a super absorbent polymer and a method for producing the same, which exhibits improved liquid permeability while maintaining good absorption performance.

Background Art

Super Absorbent Polymer (SAP) is a synthetic polymer material capable of absorbing water of 500 to 1,000 times its own weight.As a developer, super absorbent material (SAM) and absorbent gel (AGM) They are named differently. Such super absorbent polymers have been put into practical use as physiological devices, and are currently used in sanitary products such as paper diapers for children, horticultural soil repair agents, civil engineering, building index materials, seedling sheets, freshness-retaining agents in food distribution, and It is 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 the shape well even in the state where the water is absorbed by volume expansion (swelling) to exhibit excellent permeability.

On the other hand, efforts have recently been made to provide thinner diapers. Accordingly, the content of pulp is significantly reduced than that of conventional diapers, or furthermore, for so-called pulpless diapers which immobilize the superabsorbent polymer through other means such as spots and adhesives without using pulp. There is a great deal of interest. Thus, it is known that for a pulpless diaper in which the content of pulp is greatly reduced or the pulps are not used, the application of a super absorbent polymer which exhibits more improved fluidity and gel strength than previously known is required.

This is because, in order for a pulpless diaper having a reduced pulp content or eliminating the use of pulpless to have an excellent fit from the user's point of view, the superabsorbent resin included therein needs to exhibit higher liquid permeability.

In addition, in this type of diaper, as the content of the pulp that completes / protects the superabsorbent polymer particles from the outer layer is reduced, or the pulp itself is excluded, the superabsorbent resin is not limited to the outer layer and has excellent physical properties. In order to maintain shape, it is necessary to have a higher gel strength on its own,

Furthermore, in order for the superabsorbent polymer to express and maintain the above-mentioned high liquid permeability, the superabsorbent polymer particles need to maintain their shape even after they have absorbed water and swelled to maintain voids between the particles and the particles. This is because the voids between the particles act as flow paths to ensure excellent liquid permeability of the superabsorbent polymer. For this reason, in order to provide the superabsorbent polymer which exhibits the improved fluid permeability and other outstanding physical properties as mentioned above, such a superabsorbent resin needs to exhibit higher gel strength. Due to the tendency of the diaper development as described above, the characteristics of the superabsorbent resin required for this, the interest in improving the gel strength and liquid permeability of the superabsorbent polymer in recent years has been focused more. However, in order to increase the gel strength of the superabsorbent polymer, it is generally known that the basic absorbent capacity of the superabsorbent polymer is lowered. There was a technical difficulty, and research to solve this problem continues.

Due to the above technical requirements, various attempts have been made to improve the fluid permeability or gel strength of superabsorbent polymers, and representative examples thereof include water-soluble polyvalent metal compounds and surface-insoluble inorganic compounds in surface-crosslinked high-hop polymer resins. The method of adding a microparticle or a cationic high molecular compound as an additive for improving fluid permeability is mentioned.

However, even by such a conventional method, the liquid permeability or gel strength improvement of the super absorbent polymer was not sufficiently improved. Furthermore, as the additive is separated from the surface of the super absorbent polymer particles with time, the liquid permeability is greatly reduced. It is true that there was a trend. Moreover, when the above-mentioned conventional method is applied, there is a problem that, despite the improvement of the fluid permeability, the deterioration of basic absorption ability such as absorption under pressure.

Accordingly, there is a continuous demand for the development of a technology capable of providing a super absorbent polymer that exhibits more improved liquid permeability and gel strength while maintaining excellent absorption performance.

[Contents of the Invention]

[Achievement to be solved] ^"

The present invention is to provide a super absorbent polymer and a method for producing the same, which exhibits improved liquid permeability and strength while maintaining excellent absorption performance. [Measures of problem]

The present invention includes a base resin powder comprising a first crosslinked polymer of a water-soluble ethylenically unsaturated monomer having at least a portion of neutralized acid groups; And

A superabsorbent polymer formed on the base resin powder, the first crosslinked polymer comprising a surface crosslinked layer comprising a second crosslinked polymer further crosslinked through an alkylene carbonate having 2 to 5 carbon atoms,

Absorbance represented by the following formula 1 is 45 to 65g / g,

Saline induced flow (0.685 weight ^_0/0 aqueous sodium chloride solution) (SFC;

^• 1 (r ⁷ cm ³ s / g) is 70 to 190 (10 ^"7 cm ³ 's / g),

A superabsorbent polymer having a gel strength (G ′) of 9,000 to 18,000 Pa is provided: [Formula 1]

Absorbance = CRC + AUP

The CRC and the physiological saline of the water-absorbent resin (0.9 parts by weight ⁰ /. Sodium chloride Aqueous solution) for 30 minutes.

AUP shows the pressure-absorbing capacity of the superabsorbent polymer under a pressure of 0.7 psi for 1 hour under physiological saline (0.9 weight ⁰ /. Sodium chloride aqueous solution),

Gel strength (G ') is the high after swelling by absorbing the physiological saline solution (0.9 weight ^_0/0 aqueous sodium chloride solution) for 1 hour in the water-absorbent resin, a horizontal gel strength of the superabsorbent resin measured by using a rheometer Indicates.

In addition, the present invention provides a super absorbent polymer further comprising an inorganic particle, for example, hydrophobic inorganic particles and hydrophilic inorganic particles dispersed on the surface crosslinking layer in the superabsorbent polymer.

The present invention also provides a step of crosslinking and polymerizing a water-soluble ethylene-based unsaturated monomer having at least a part of a neutralized acidic group in the presence of an internal crosslinking agent to form a hydrogel polymer comprising a first crosslinked polymer;

Drying, pulverizing and classifying the hydrogel polymer to form a base resin powder having a gel strength (G ′) of at least 5,000 Pa;

Adding hydrophobic inorganic particles having a contact angle of ^at least 50 ^° with respect to water on the base resin powder; And

In the presence of a surface crosslinking liquid containing a hydrophilic inorganic particle having a contact angle of 10 ^° or less with respect to water and a surface crosslinking agent of alkylene carbonate having 2 to 5 carbon atoms, the base resin powder to which the hydrophobic inorganic particle is added is subjected to a surface treatment. It provides a method for producing a super absorbent polymer of the present invention comprising the step of crosslinking. Hereinafter, a super absorbent polymer according to a specific embodiment of the present invention and a manufacturing method thereof will be described in more detail. However, this is presented as an example of the invention, whereby the scope of the invention is not limited, it is apparent to those skilled in the art that various modifications to the embodiments are 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) To be interpreted as Can't.

According to one embodiment of the invention, at least a portion of the base resin powder comprising a first cross-linked polymer of a water-soluble ethylenically unsaturated monomer having a neutralized acid group; And

As a super absorbent polymer formed on the said base resin powder, The said 1st crosslinked polymer includes the surface crosslinking layer containing the 2nd crosslinked polymer further bridge | crosslinked through the C2-C5 alkylene carbonate,

Absorbance represented by the following formula 1 is 45 to 65g / g,

Flow-inducible (SFC; -1 (r ⁷ cm ³ s / g) of physiological saline (0.685 weight ⁰ /. Aqueous sodium chloride solution) is 70 to 190 (1 Cr ⁷ cm ³ s / g),

Absorbance = CRC + AUP

CRC represents the centrifugal water retention capacity for 30 minutes with respect to the physiological saline solution (0.9 weight ⁰ /. Sodium chloride aqueous solution) of the super absorbent polymer,

AUP shows the pressure-absorbing capacity for 1 hour under o.7psi for the physiological saline solution (0.9 weight ⁰ /. Sodium chloride solution) of the super absorbent polymer,

Gel strength (G ′) is the horizontal gel strength of the superabsorbent polymer measured using a rheometer after swelling by absorbing physiological saline (0.9 wt% aqueous sodium chloride solution) for 1 hour to the superabsorbent polymer.

The superabsorbent polymer of the embodiment may further include inorganic particles, for example, hydrophobic inorganic particles and hydrophilic inorganic particles dispersed on the surface crosslinking layer.

The inventors of the present invention continually studied to further improve the liquid permeability of the superabsorbent polymer, and as a result, the conditions of the manufacturing process of the superabsorbent polymer described later _. For example, the type and content of the internal crosslinking agent described below and the polymerization conditions are optimized to obtain a base resin powder having a high gel strength, and specific surface crosslinking conditions (for example, two specific inorganic particles are used in sequence, and the surface Preferred cross-linking temperature conditions As the surface crosslinking proceeds under the above), it has been found that a superabsorbent polymer can be provided that exhibits significantly improved liquid permeability than previously known while maintaining excellent absorption performance.

In particular, the hydrophobic inorganic particles defined in the predetermined contact angle range are pretreated on the base resin powder, and surface crosslinking is carried out under specific elevated temperature conditions by adding a surface crosslinking solution containing hydrophilic inorganic particles and a specific surface crosslinking agent. It is believed that the surface crosslinking layer having a thickness of a predetermined level or more may be uniformly formed on the base resin powder having the same.

This allows the inorganic particles, more specifically the hydrophobic and hydrophilic inorganic particles, to be contained on the surface crosslinking layer (eg, in the crosslinking structure of the second crosslinked polymer of the surface crosslinking layer) to make this crosslinking structure more firm. In addition, it is expected that the surface crosslinking reaction occurs appropriately around each inorganic particle during the surface crosslinking so that the second crosslinked polymer can be effectively formed.

Accordingly, the surface cross-linking layer can further increase the gel strength of each of the superabsorbent polymer particles, the superabsorbent polymer of one embodiment has a very high gel strength of 9,000 to 18,000 Pa, the 70 to 190 ('1 (T ⁷ cm ³ s / g) can exhibit a significantly improved liquid permeability, In addition, the super absorbent polymer of one embodiment is the absorption of the 45 to 65g / g, as the internal cross-linked structure and the surface cross-linked structure is optimized It can exhibit a good absorption performance defined by degrees.

Therefore, the super absorbent polymer of one embodiment exhibits significantly improved liquid permeability and excellent absorption performance than previously known, and thus can be very preferably applied to various sanitary materials such as diapers having a reduced pulp content. On the other hand, the superabsorbent polymer is surface cross-linked when the inorganic particles, more specifically, the hydrophobic inorganic particles having a contact angle of more than 50 ^°, or 50 ^° to 175 ^° for water and less than 10 ^° against water, or from 1 to 10 Hydrophilic inorganic particles having a contact angle of ^° can be used. Accordingly, the super absorbent polymer of one embodiment may further include inorganic particles dispersed on the surface crosslinked worm. see Specifically, the superabsorbent polymer may further include hydrophobic inorganic particles dispersed on the base resin powder and hydrophilic inorganic particles dispersed on the surface crosslinking layer. Such hydrophobic inorganic particles may, for example, be at least partially present on the surface of the base resin powder (eg, in the surface crosslinked layer), and the remainder embedded in or embedded in the surface of the base resin powder. May exist. In addition, the hydrophilic inorganic particles may be present in the crosslinked structure of the second crosslinked polymer of the surface crosslinked layer or embedded in the surface of the surface crosslinked layer.

In this way, as the inorganic particles for improving the liquid permeability are present at least on the surface crosslinked layer, it is possible to maintain the liquid permeability improvement by the passage of time, and in particular, even if an external force is applied, high gel strength and Improved fluidity can be maintained.

As the hydrophobic inorganic particles, one or more selected from the group consisting of silica particles, titania particles, and zirconia particles having the aforementioned contact angle range may be used, and the hydrophilic inorganic particles may have silica having a contact angle range of 10 ^° or less. At least one selected from the group consisting of particles, titania particles, zirconia particles, and laponite particles can be used.

In addition, a contact angle with respect to water that separates the hydrophilic and hydrophobic inorganic particles may be defined as a contact angle with respect to water of the inorganic particles coated on the glass substrate. Specific methods of measuring such contact angles are described in the Examples below.

On the other hand, the super absorbent polymer may have a centrifugal water retention capacity (CRC) of 24 to 35 g / g and black to 25 to 32 g / g.

At this time, the centrifugal water retention capacity (CRC) for the physiological saline can be calculated by the following formula 1 after absorbing the superabsorbent resin in physiological saline over 30 minutes:

[Calculation 1]

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

In the above formula 1,

W ₀ (g) is the initial weight (g) of the superabsorbent polymer, and W ^ g) is the superabsorbent polymer. Without using, absorbed by immersion in physiological saline for 30 minutes, and then dehydrated at 250G for 3 minutes using a centrifuge, the weight of the device, W ₂ (g) is a superabsorbent resin in physiological saline at room temperature 30 This is the device weight measured, including the superabsorbent resin, after immersion for minutes to absorb, followed by dehydration at 250 G for 3 minutes using a centrifuge.

In addition, the superabsorbent polymer may have a pressure absorption capacity (AUP) of 22 to 27 g / g, or 22 to 26 g / g.

This pressurized absorbent capacity (AUP) can be calculated according to Formula 2 after absorbing the superabsorbent resin in physiological saline under a pressurization of 0.7 psi over 1 hour:

[Calculation 2]

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

In Formula 2,

W ₀ (g) is the initial weight (g) of the superabsorbent polymer, W ₃ (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, and W ₄ (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 1 hour under a load (0.7 psi).

As the super absorbent polymer of one embodiment exhibits centrifugal water retention (CRC) and pressurized absorbent capacity (AUP) in the above-mentioned range, the superabsorbent resin has an absorbency of 45 to 65 g / g, or 50, defined by Equation 1. To 60 g / g. Accordingly, the superabsorbent polymer of one embodiment exhibits excellent absorption performance such as basic absorption force and absorption holding force under pressure, and thus can be suitably used for various sanitary materials.

On the other hand, the super absorbent polymer of the embodiment may exhibit a characteristic in which the horizontal gel strength G 'is 9,000 to 18,000 Pa, or 9,500 to 15,000 Pa, together with the above-described absorption performance.

The horizontal gel strength G 'can better reflect the excellent liquid permeability under the actual use environment of the super absorbent polymer. In other words, the liquid permeability of the super absorbent polymer is generally included in sanitary materials such as diapers. At the same time, it can be determined to be more relevant depending on whether the force applied in the horizontal direction is excellent and exhibits good shape retention and high gel strength. The horizontal gel strength may well reflect the gel strength directly related to the liquid permeability. Can be. Therefore, the superabsorbent polymer of one embodiment in which such horizontal gel strength G 'satisfies the above-mentioned range exhibits excellent liquid permeability, and thus, it has been found that it can be very preferably used for hygiene materials such as diapers.

This horizontal gel strength G 'can be measured by absorbing physiological saline in the superabsorbent resin for 1 hour and then using a commercialized rheometer in a method comprising each of the following steps:

1) swelling by absorbing physiological saline to the super absorbent polymer;

2) placing the swollen superabsorbent resin between the plates of the rheometer having a predetermined interval and pressing both plate surfaces;

3) using the rheometer under vibration to increase the shear strain, identifying shear strain in a linear viscoelastic regime where the storage modulus and loss modulus are constant;

4) measuring the storage modulus and loss modulus of the swelled superabsorbent resin under the identified shear deformation, respectively, and measuring the average value of the storage modulus as gel strength.

In addition, the super absorbent polymer of one embodiment has a physiological saline flow inducibility (SFC) for physiological saline of 70 to 190 1 (T ⁷ cm ³ s / g or 70 to 150 1 (T ⁷ cm ³ s / g black silver 80) to ^{^{130 -. 10- 7 cm 3 s}} / g may be in such a saline flow induced (SFC) is well known to those skilled in the art from the previous room, for example, in US Patent Publication No. 2009-0131255 arc column 16. [0184 ] Can be measured and calculated according to the methods disclosed in [0189].

On the other hand, the super absorbent polymer of one embodiment is a water-soluble ethylenically unsaturated monomer having an acidic group at least partially neutralized, such as a mixture of acrylic acid and its sodium salt, at least some of the carboxylic acid is neutralized with sodium salt or the like, the presence of an internal crosslinking agent It can be obtained by polymerization under. More specifically, the super absorbent polymer may be used to convert the monomer in the presence of an internal crosslinking agent. It can obtain by crosslinking-polymerizing and obtaining a base resin powder, and manufacturing the crosslinked polymer which surface-crosslinked the said base resin powder in presence of a predetermined surface crosslinking agent and inorganic particle.

More specifically, by adjusting the type and content of the internal crosslinking agent, polymerization conditions and the like to obtain a base resin powder having a high gel strength, for example, using a specific two kinds of inorganic particles sequentially, surface cross-linking temperature rising conditions As the surface crosslinking proceeds under specific conditions such as, it was confirmed that the superabsorbent polymer of one embodiment exhibiting the above-described general physical properties can be prepared.

According to another embodiment of the present invention, there is provided a method for preparing a super absorbent polymer of the above embodiment. This preparation method comprises crosslinking polymerization of 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 comprising a first crosslinked polymer;

In the presence of a surface crosslinking liquid containing hydrophilic inorganic particles having a contact angle of 10 ^° or less with respect to water and a surface crosslinking agent of alkylene carbonates having 2 to 5 carbon atoms, the base resin powder to which the hydrophobic inorganic particles are added is subjected to a surface treatment. It may include the step of crosslinking.

According to the production method of this other embodiment, after obtaining the base resin powder having a high gel strength, and at the time of surface crosslinking, first, the aforementioned hydrophobic inorganic particles are mixed with the base resin powder in a solid state and treated on the surface thereof, Surface crosslinking is performed using the surface crosslinking liquid containing the hydrophilic inorganic particles and the alkylene carbonate-based surface crosslinking agent. As a result, a surface crosslinking layer having a thickness of a predetermined level or more may be uniformly formed, and a super absorbent polymer of one embodiment which exhibits excellent absorption performance with improved gel strength and liquid permeability may be prepared.

In such a super absorbent polymer, the water-soluble ethylenically unsaturated monomer is Acrylic acid, methacrylic acid, maleic anhydride, fumaric acid, crotonic acid, itaconic acid, 2-acryloylethane sulfonic acid, 2-methacryloylethanesulfonic acid, 2-

Anionic monomers of (meth) acryloylpropanesulfonic acid or 2- (meth) acrylamide-2-methyl propane sulfonic acid and salts thereof; (Meth) acrylamide, N-substituted (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate,

Nonionic hydrophilic-containing monomers of mesoxypolyethylene glycol (meth) acrylate or polyethylene glycol (meth) acrylate; And amino group-containing unsaturated monomers of (Ν, Ν) -dimethylaminoethyl (meth) acrylate or (Ν, N-dimethylaminopropyl (meth) acrylamide) and quaternary compounds thereof; Among these, it is possible to use acrylic acid or its salts, for example alkali metal salts of acrylic acid and / or its sodium salt ^, in which at least a portion of the acrylic acid is neutralized, and such monomers can be used to achieve high physical properties. When the acrylic acid and its alkali metal salt are used as monomers, at least a part of the acrylic acid can be neutralized with a basic compound such as caustic soda (NaOH).

In addition, the internal crosslinking agent for crosslinking polymerization of such monomers includes bis (meth) acrylamide having 8 to 12 carbon atoms, poly (meth) acrylate of polyol having 2 to 10 carbon atoms and poly (meth) of polyol having 2 to 10 carbon atoms. One or more types selected from the group consisting of allyl ether can be used. More specifically, the internal crosslinking agent is one selected from the group consisting of polyethylene glycol di (meth) acrylate, polypropyleneoxy di (meth) acrylate, glycerin diacrylate, glycerin triacrylate and trimethy triacrylate The poly (meth) acrylate of the above polyol can be used suitably. Among these, as the internal crosslinking agent such as polyethylene glycol di (meth) acrylate is used, an internal crosslinking structure may be optimized and a base resin powder having a high gel strength may be obtained. A super absorbent polymer can be obtained more appropriately. More specifically, by using a specific content of such a specific internal crosslinking agent, the gel strength (G ′; Pa) of the base resin powder before surface crosslinking may be prepared to be 5,000 Pa or more, or 5,000 to 10,000 Pa, or 5,500 to 8,000 Pa. As it proceeds to the surface crosslinking step under certain conditions, it is possible to obtain a super absorbent polymer of one embodiment.

For example, the specific internal crosslinking agent is 0.0005 mol or more, or 0.0005 to 0.002 mol (or 0.4 weight part or more relative to 100 weight parts of acrylic acid, based on 1 mol of unneutralized acrylic acid included in the monomer, black is 0.4 to 1.5 parts by weight). According to the content range of such an internal crosslinking agent, a base resin powder having a gel strength (G ′; Pa) of 5,000 Pa or more before surface crosslinking can be appropriately obtained, and a super absorbent polymer of one embodiment can be obtained.

On the other hand, the gel strength of the base resin powder can be measured under the same method and conditions as the gel strength of the superabsorbent polymer described above.

After the crosslinking polymerization of the monomer using the internal crosslinking agent, a base resin powder can be obtained through a process such as drying, pulverization and classification. The superabsorbent polymer obtained is suitably manufactured and provided to have a particle size of 150 to 850 // m, or 150 to 710 zm. More preferably, the base resin powder and has a high, at least 95 weight ⁰ /. Particle size of more than 150 to 710 ^ 1 of the water-absorbent resin obtained therefrom, and 3 is a differential having a particle size of less than 150 parts by weight ⁰ / less than _0, The black may be less than 1.5 weight ⁰ /.

Thus, as the particle size distribution of the base resin powder and the super absorbent polymer is adjusted to a preferred range, the super absorbent polymer of the embodiment may more properly exhibit the above-described physical properties.

In addition, the super absorbent polymer of one embodiment includes a base resin powder comprising a first crosslinked polymer prepared by the above-described method, and a surface crosslinking comprising a second crosslinked polymer in which the first crosslinked polymer 'is further crosslinked by surface crosslinking. It may comprise a layer. Surface crosslinking for forming the surface crosslinking layer is carried out by dry treatment on the base resin powder by adding the hydrophobic inorganic particles, and then the surfaces of the hydrophilic inorganic particles and alkylene carbonates having 2 to 5 carbon atoms. In the presence of a surface crosslinking solution containing a crosslinking agent, the hydrophobic inorganic particles may be added to a method of heat-treating the base resin powder. In this case, since the hydrophobic and hydrophilic inorganic particles that can be used are as described above, further description thereof will be omitted.

Further, more suitable examples of the alkylene carbonate having 2 to 5 carbon atoms that can be used as the surface crosslinking agent include ethylene carbonate, propylene carbonate, butylene carbonate, and the like. to be.

On the other hand, it will be described in more detail with respect to each step for a method for producing a super absorbent polymer of the above-described embodiment. However, the above-described monomer, internal crosslinking agent, surface crosslinking agent, inorganic particles, particle size distribution, and the like will not be repeated, and the remaining process configurations and conditions will be described step by step.

The method of preparing the superabsorbent polymer may include forming a hydrogel polymer including a first crosslinked polymer by thermally polymerizing or photopolymerizing a monomer composition including a water-soluble ethylenically unsaturated monomer, an internal crosslinking agent, and a polymerization initiator; Drying the hydrogel polymer; Grinding and classifying the dried polymer to form a base resin powder; And treating the hydrophobic inorganic particles with respect to the base resin powder, and performing surface crosslinking using the surface crosslinking liquid including the hydrophilic inorganic particles and the surface crosslinking agent described above.

In such a production method, the monomer composition includes a water-soluble ethylenically unsaturated monomer, an internal crosslinking agent and a polymerization initiator, and the type of the monomer is as described above.

In addition, such compositions in the concentration of the water-soluble ethylenically block saturated monomers, 20 to 60 parts by weight ⁰ / for the total monomer composition comprising the respective raw materials and the solvent described above, or 40 to 50 parts by weight ⁰ /. To be in It may be made to an appropriate concentration in consideration of the 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 may cause a problem in economics. Process problems such as low grinding efficiency of the precipitated or polymerized hydrogel polymer may occur, and physical properties of the superabsorbent polymer may be degraded.

In addition, the said polymerization initiator will not be specifically limited if it is generally used for manufacture of a super absorbent polymer.

Specifically, the polymerization initiator may use a thermal polymerization initiator or a photopolymerization initiator according to UV irradiation depending on the polymerization method. However, even with the photopolymerization method, since a certain amount of heat is generated by irradiation such as ultraviolet irradiation, and a certain amount of heat is generated in accordance with the progress of the polymerization reaction, which is an exothermic reaction, 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. Meanwhile, as an example of acylphosphine, a commercially available lucirin TPO, that is, 2,4,6-trimethyl- benzoyl-trimethyl phosphine oxide (2,4,6-trimethyl-benzoyl-trimethyl phosphine oxide) can be used. . A wider variety of photoinitiators is well specified in Reinh d Schwalm's book "UV Coatings: Basics, Recent Developments and New Application (Elsevier 2007)" p115, and is not limited to the examples described above.

The photopolymerization initiator may be included in a concentration of 0.0005 to 0.05% by weight based on the monomer composition. When the concentration of the photopolymerization initiator is too low, the polymerization rate may be slow. When the concentration of the photopolymerization initiator is too high, the molecular weight of the superabsorbent polymer may be low and the physical properties may be uneven.

In addition, the thermal polymerization initiator may be used at least one selected from the group consisting of persulfate initiator, azo initiator, hydrogen peroxide and ascorbic acid. Specifically, examples of persulfate-based initiators include sodium persulfate (Na ₂ S ₂ O ₈ ), potassium persulfate (Potassium persulfate; K2S208), Ammonium persulfate; (NH ₄ ) ₂ S ₂ 0 ₈ ), and examples of azo initiators include 2, 2-azobis- (2-amidinopropane) dihydrochloride ( 2, 2- azobis (2-amidinopropane ) dihydrochloride), 2, 2- azobis - ^(N, N- di-methylene) isobutoxy Thira Mai Dean dihydrochloride (2,2-azobis- (N, N- dimethylene) isobutyramidine dihydrochloride), 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] dihydrochloride), 4,4-azobis- (4-cyanovaleric acid) (4,4-azobis- (4-cyanovaleric acid)), and the like. More various thermal polymerization initiators are well specified in Odian's Principle of Polymerization (Wiley, 1981), p203, and are not limited to the examples described above.

The thermal polymerization initiator may be included in a concentration of 0.001 to 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 may be low and the physical properties may be uneven. have.

And, the kind of the internal crosslinking agent included in the monomer composition is as described above. In addition, the internal crosslinking agent is 0.0005 mol or more, black is 0.0005 to 0.002 mol (black is 0.4 parts by weight or more relative to 100 parts by weight of acrylic acid, or 0.4 to 15 parts by weight based on 1 mole of unneutralized acrylic acid contained in the monomer) Can be used in the ratio. As such an internal crosslinking agent is used in this content range, it is possible to adequately stratify the gel strength range before the surface crosslinking already described above, and a superabsorbent resin which more appropriately stratifies the physical properties of the above-described embodiment can be prepared using this. .

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

Raw materials such as the above-described water-soluble ethylene-based unsaturated monomer, photopolymerization initiator, thermal polymerization initiator 1, internal crosslinking agent 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 dissolve the above-mentioned components. It can be used without limitation in composition, for example, water, ethane, ethylene glycol, diethylene glycol, triethylene glycol, 1,4-butanediol, propylene glycol, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, Propylene glycol monomethyl ether acetate, methyl ethyl ketone, acetone, methyl amyl ketone, cyclonucleanone, cyclopentanone, diethylene glycol monomethyl ether, diethylene glycol ethyl ether, toluene, xylene, butyrolactone, carbyl It may be used in combination of one or more selected from methyl cellosolve acetate and Ν, Ν-dimethylacetamide.

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, when the thermal polymerization is usually carried out, it can be carried out in a reactor having a stirring shaft, such as kneader, and, when the photopolymerization proceeds, Although it can be carried out in a semi-unggi equipped with a conveyor belt, the above-described polymerization method is an example, the present invention is not limited to the above-described polymerization method.

For example, as described above, the hydrogel polymer obtained by thermal polymerization by supplying hot air or by heating the reaction vessel is a semi-ungker, such as a kneader having a stirring shaft, according to the shape of the stirring shaft provided in the reactor. The hydrogel polymer discharged to the outlet may be in the form of several centimeters to several millimeters. Specifically, the size of the hydrogel polymer obtained may vary depending on the concentration and the injection speed of the monomer composition to be injected, it can be usually obtained a hydrogel polymer having a weight average particle diameter of 2 to 50 mm.

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

The normal water content of the hydrogel polymer obtained in this way may be a 40 to 80 wt. ^_0/0. On the other hand, throughout the present specification, "water content" means the content of water to account for the total weight of the hydrogel polymer minus the weight of the polymer in the dry state. Specifically, it is defined as a value calculated by measuring the weight loss due to moisture evaporation in the polymer in the process of raising the temperature of the polymer through infrared heating and drying. At this time, the drying conditions were a total drying time in such a manner as to keep the back in a 180 ^° C raising the temperature from room temperature to 180 ^° C is set to 20 minutes, including 5 at a temperature ramping up step, to measure the water content.

Next, the step of drying the obtained hydrogel polymer is performed.

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 mill, a cutting machine Includes any one selected from the group of grinding machines consisting of cutter mills, disc mills, shred crushers, crushers, choppers and disc cutters Although it is possible, it is not limited to the above-mentioned example. At this time, the coarse grinding step may be pulverized so that the particle diameter of the hydrogel polymer is 2 to 10mm. ·

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 crushed particles cross each other. On the other hand, in the case where the particle diameter is pulverized more than 10 mm, the effect of increasing the efficiency of the subsequent drying step may be minimal.

As described above, the coarsely pulverized or black is not subjected to the coarsely pulverized step Drying is performed on the hydrous gel polymer immediately after. At this time, the drying temperature of the drying step may be 150 to 250 ^° C. If the drying temperature is less than 150 ^° C., the drying time may be too long and the physical properties of the final superabsorbent polymer may be lowered. If the drying temperature is greater than 250 ^° C., only the polymer surface is dried excessively. Fine powder may occur in the grinding step, and there is a fear that the physical properties of the superabsorbent polymer to be finally formed decrease. Therefore, preferably, the drying may be performed at a temperature of 150 to 200 ^° C, more preferably at a temperature of 170 to 195 ^° C.

On the other hand, in the case of the drying time, in consideration of the process efficiency, etc., it may proceed for 20 to 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 grinding step may have a particle diameter of 150 to 850 /. Grinders 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, but is not limited to the example described above.

In addition, in order to manage the physical properties of the super absorbent polymer powder to be finalized after such a grinding step, a separate process of classifying the polymer powder obtained after grinding according to the particle diameter may be performed. Preferably, the polymer having a particle size of 150 to 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 this process has already been described above, further detailed description thereof will be omitted.

The horizontal gel strength (G ') before the surface crosslinking of the base resin powder described above It can be stratified in the range of 5,000 Pa or more, or 5,000 to 10,000 Pa, or 5,500 to 8,500 Pa, and if the gel strength of the base resin powder before the surface crosslinking falls within the above range, the superabsorbency prepared through the surface crosslinking reaction described later The resin may achieve the physical properties of one embodiment.

On the other hand, after obtaining the base resin powder through the above-described grinding and / or classification process, it is possible to manufacture a super absorbent polymer of one embodiment through a surface crosslinking process. Since the kind of surface crosslinking agent, hydrophobic, and hydrophilic inorganic particle which can be used at such a surface crosslinking process was already mentioned above, the related description is abbreviate | omitted.

First, the base resin powder may be mixed with hydrophobic inorganic particles in a solid state and treated on a surface thereof, and the treatment method thereof may be a dry treatment and / or a mixing method of a general inorganic powder.

Moreover, there is no special limitation of the structure also about the method of adding to the surface crosslinking liquid allol base resin powder containing a hydrophilic inorganic particle and a surface crosslinking agent. For example, the surface crosslinking solution and the base resin powder are mixed in a semi-permanent mixture, or the surface crosslinking solution is sprayed onto the base resin powder, and the base resin powder and the surface crosslinking solution are continuously supplied to the mixer which is operated continuously. Method can be used.

The hydrophobic inorganic particles and the hydrophilic inorganic particles may be used in amounts of 0.0001 to 0.3 parts by weight, and black of 0.001 to 0.2 parts by weight based on 100 parts by weight of the base resin powder, respectively. Thereby, according to the use of each inorganic particle, the fluid permeability and various characteristics of a super absorbent polymer can be improved more effectively. The superabsorbent polymer of one embodiment prepared using each of the inorganic particles having such a content may also include hydrophobic and hydrophilic inorganic particles in a content range corresponding thereto.

The surface crosslinking liquid may further include water and / or a hydrophilic organic solvent as a medium. As such, there is an advantage that the surface crosslinking agent and the hydrophilic inorganic particles can be evenly dispersed on the base resin powder. At this time, the content of water and hydrophilic organic solvent induces even dispersion of the surface crosslinking agent and the hydrophilic inorganic particles, prevents agglomeration of the base resin powder and at the same time the surface penetration of the surface crosslinking agent For the purpose of optimizing the depth can be applied by adjusting the addition ratio to 100 parts by weight of the base resin powder.

5 minutes to 60 minutes, or 10 minutes to 50 minutes, or 20 minutes to 45 at a reaction maximum temperature of 140 ^° C to 200 ^° C, or 17 C C to 195 ^° C with respect to the base resin powder to which the surface crosslinking solution is added The surface crosslinking reaction can proceed for minutes. More specifically, the surface cross-linking step is the temperature of the reaction to the reaction at the initial temperature of 20 ^° C to 130 ^° C, black 40 ^° C to 120 ^° C over 10 minutes to 30 minutes, and the maximum temperature It can be carried out by maintaining the heat treatment for 5 to 60 minutes.

By satisfying such surface crosslinking process conditions (particularly, elevated temperature conditions and reaction conditions at the maximum reaction temperature), it was confirmed that a superabsorbent polymer that properly stratified the physical properties of one embodiment can be produced.

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 may be a means of heating medium, a temperature increase rate, and a target temperature increase. Consideration can be made as appropriate. On the other hand, the heat source directly supplied may be a heating method through electricity, a heating method through a gas, but is not limited to the above-described example. The superabsorbent polymer obtained according to the above-described manufacturing method maintains excellent water-absorbing performance such as water-retaining capacity and pressure-absorbing capacity, and satisfies improved horizontal gel strength and liquid permeability, and can satisfy various physical properties of one embodiment. In addition, hygiene materials such as diapers, in particular, ultra-thin hygiene materials with reduced pulp content may be appropriately used.

【Effects of the Invention】

According to the present invention, it is possible to provide a superabsorbent polymer and a method for producing the same, which maintain excellent water absorbing performance such as water-retaining capacity and pressure-absorbing capacity, and which further improves horizontal gel strength and liquid permeability.

These super absorbent polymers are diapers. Back sanitary materials, in particular, ultra-thin sanitary materials with reduced content of the peel, and the like can be suitably used. [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. In the following examples and comparative examples, the contact angles of the hydrophobic inorganic particles and the hydrophilic inorganic particles with respect to water were measured as follows.

First, a hydrophobic inorganic particle was used as a coating liquid dispersed in a methylene chloride solvent at a concentration of 5% by weight. The coating solution was spin coated onto a wafer having no surface roughness, and dried at room temperature to remove the remaining solvent. The contact angle was measured by dropwise dropping water on the coating layer. The measured contact angle is defined as the contact angle of the hydrophobic inorganic particles with respect to water, and the measured values are shown in Table 1 below.

In addition, in the case of the hydrophilic inorganic particles, the contact angle with respect to water was measured in the same manner as in the hydrophobic inorganic particles, except that the coating solution dissolved or dispersed in water at a concentration of 20% by weight ⁰ /. .

TABLE 1

In addition, in the following Example and the comparative example, the physical property of each super absorbent polymer was measured and evaluated by the following method.

(1) Grain size evaluation

Of the base resin powder and the super absorbent polymer used in Examples and Comparative Examples The particle size was measured according to the European Disposables and Nonwovens Association (EDANA) standard EDANA WSP 220.3 method.

(2) Centrifuge Retention Capacity (CRC)

European Disposables and Nonwovens Association,

EDANA) In accordance with the standard EDANA WSP 241.3, for the superabsorbent polymers of Examples and Comparative Examples, the centrifugal water retention capacity (CRC) was measured with no-load absorption ratio.

That is, the resin of Examples and Comparative Examples W ₀ into a (g, about 0.2g) uniformly on the envelope of the non-woven fabric sealed (seal) one after, immersion in physiological saline is a sodium chloride solution of 0.9 weight ⁰ /. To room temperature did. 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. Moreover, after performing the same operation without using resin, the mass W ^ g at that time was measured.

Using each mass thus obtained, CRC according to the following equation 1

(g / g) was calculated to confirm the water holding capacity.

[Calculation 1]

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

In Formula 1,

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

W ^ g) is the weight of the device measured after immersion in physiological saline for 30 minutes without using a super absorbent polymer, and then dehydrated at 250 G for 3 minutes using a centrifuge.

W ₂ (g) is the weight of the device, including the superabsorbent polymer, after absorbing the superabsorbent polymer in physiological saline at room temperature for 30 minutes and then dehydrating it at 250 G for 3 minutes using a centrifuge.

(3) Absorbing under Pressure (AUP)

Super Absorbency of Examples and Comparative Examples _. Resin, European Disposables and Nonwovens Association Standard Absorbency under Pressure (AUP) was measured according to the method of EDANA WSP 242.3.

First, a stainless steel 400 mesh wire was mounted on the bottom of a 60 mm plastic cylinder. Evenly spread the resin W ₀ (g, 0.90 g) obtained in Examples 1-6 and Comparative Examples 1-3 on a wire mesh under a temperature of 23 ± 2 ^° C. and a relative humidity of 45% and thereon 4.83 kPa ( The piston, which can give a uniform load of 0.7 psi), has an outer diameter of slightly smaller than 60 mm, no gap with the inner wall of the cylinder, and unhindered movement of up and down. At this time, the weight W ₃ (g) of the apparatus was measured.

A glass filter having a diameter of 125 mm and a thickness of 5 mm was placed inside a petri dish having a diameter of 150 mm, and a physiological saline composed of 0.90 weight ⁰ / .sodium chloride was at the same level as the upper surface of the glass filter. One sheet of filter paper 120 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 up and the weight W ₄ (g) was measured.

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

[Calculation 2]

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

In Formula 2,

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

W ₃ (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,

W ₄ (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 1 hour under a load (0.7 psi).

(4) Gel Strength (G ')

For the superabsorbent polymer / base resin powders of Examples and Comparative Examples, the gel strength in the horizontal direction was measured. First, 0.5 g of the superabsorbent polymer samples (30-50 Mesh) of Examples and Comparative Examples were sieved through a sieve. The weighed sample was swollen in 50 g of saline solution for 1 hour. Thereafter, unabsorbed solvent was removed using an aspirator for 4 minutes, and the external solvent was evenly distributed over filter paper and wiped off once.

2.5 g of the swollen superabsorbent polymer sample is placed on a rheometer and two parallel plates (25 mm in diameter, with a wall that prevents 2 mm of sample from escaping at the bottom), and the spacing between the two parallel plates is 1 mm was adjusted. At this time, the swelled superabsorbent polymer sample was pressed with a force of about 3N so as to contact all of the parallel plate surface to adjust the distance between the parallel plate.

Using the rheometer, at the Oscilation frequency of 10 rad / s, the shear modulus of the linear viscoelastic regime section with a constant storage modulus and a loss modulus while increasing the shear strain Confirmed. Generally in a swollen superabsorbent polymer sample, 0.1% shear strain is within the linear viscoelastic state section.

At a constant oscillation frequency of 10 rad / s, the storage modulus and loss modulus of the superabsorbent polymer swollen for 60 seconds at the shear strain value of the linear viscoelastic state section were measured, respectively. The storage elasticity obtained at this time was averaged and the horizontal gel strength was calculated | required. For reference, the loss modulus is measured to be a very small value compared to the storage modulus.

(5) saline flow conductivity (SFC)

It was measured according to the method disclosed in [0184] to [0189] of column 16 of US Patent Publication No. 2009-0131255. Example 1

500 g of acrylic acid and 3 g of polyethylene glycol diacrylate (Mw = 523) were added and mixed, followed by dissolving by adding 0.01 g of diphenyl (2,4,6-trimethylbenzoyl) -phosphine oxide. Then, the aqueous solution of the water-soluble unsaturated monomer and the added nitrogen is continuously added to 896.4g of aqueous solution of sodium hydroxide, 24.5 parts by weight ^_0/0 Prepared. Subsequently, the temperature of the aqueous solution was cooled to 50 ^° C., and the aqueous solution was irradiated with ultraviolet rays for 90 seconds to obtain a hydrous gel polymer. The hydrous gel polymer obtained was ground using a mill. A base resin powder having a particle size of 150 to 710 / m was prepared by classifying with a standard mesh of ASTM standard. The gel strength of this base resin powder was measured at 6,588 Pa.

Thereafter, 0.05 parts by weight of the hydrophobic silica particles of VI30S were added to 100 parts by weight of the prepared base resin powder, and the mixture was stirred at room temperature to be mixed so that the base resin powder and the hydrophobic silica particles were mixed well and dried. Subsequently, 0.2 g of an aqueous solution in which hydrophilic silica particles ST-0 were dispersed in water at a concentration of 1 g of ethylene carbonate and 20 weight ⁰ / ° C was added to 3 g of water, and mixed to prepare a surface crosslinking solution. Thereafter, the surface crosslinking solution was sprayed onto the base resin powder and stirred at room temperature to mix the surface crosslinking solution evenly on the base resin powder. Subsequently, the base resin powder mixed with the surface crosslinking liquid was placed in a surface crosslinking reaction machine, and surface crosslinking reaction was performed.

Within this surface crosslinking reaction, the base resin powder was found to gradually increase in temperature at an initial temperature near 80 ^° C., and was manipulated to reach a reaction maximum temperature of 19 C C after 30 minutes. After this reaction peak temperature was reached, the reaction product was further reacted for 15 minutes, and the final prepared superabsorbent polymer sample was taken. After the surface crosslinking process, the superabsorbent polymer of Example 1 having a particle diameter of 150 to 710 / m was prepared by classifying to a standard mesh of ASTM standard. Example 2

The superabsorbent polymer of Example 2 was prepared in the same manner as in Example 1 and under the same surface crosslinking conditions, except that 0.05 parts by weight of Aerogel was added instead of the hydrophobic silica particles of I30S. Prepared.

After the surface crosslinking process, the superabsorbent polymer of Example 2 having a particle size of 150 // m to 710 was prepared by classifying to a standard mesh of ASTM standard. Example 3

For the base resin powder (gel strength: 6,588 Pa), Example 3 superabsorbent polymer was prepared in the same manner as in Example 1 and under the same surface crosslinking conditions, except that 0.05 part by weight of R972 was added instead of the 130S hydrophobic silica particles. Prepared.

After the surface crosslinking process, a superabsorbent polymer of Example 3 having a particle size of 150 / im to 710 was prepared by classifying to a standard mesh of ASTM standard. Example 4

Base resin powder (gel strength: 6,588 Pa, superabsorbent resin of Example 4 under the same method and same surface crosslinking conditions as Example 1 except that the content of the hydrophobic silica particles of 130S was added at 0.02 parts by weight) Was prepared.

After the surface crosslinking process, the superabsorbent polymer of Example 4 having a particle size of 150 im to 710 was prepared by classifying to a standard mesh of ASTM standard. Example 5

Except for the addition of 0.1 parts by weight of the hydrophobic silica particles of the above VI30S to the base resin powder (gel strength: 6,588 Pa), the same method as in Example 1 and the same surface crosslinking conditions, An absorbent resin was prepared.

After the surface crosslinking process, the superabsorbent polymer of Example 5 having a particle diameter of 710 was prepared by classifying to a standard mesh of ASTM standard. Example 6

. Example of the surface crosslinking with respect to the base resin powder (gel strength: 6,588Pa), the same method as in Example 1 and the same surface crosslinking conditions, except that the amount of the aqueous solution of the hydrophilic silica particles of ST-0 was 0.4g A super absorbent polymer of 6 was prepared.

After the surface cross-linking process, classified to a standard mesh of ASTM standards 150 The superabsorbent polymer of Example 6 having a particle size of 710 / m was prepared. Example 7

Base resin powder (gel strength: except that 0.4g of aqueous solution in which ST-AK hydrophilic silica particles were dispersed in water at a concentration of 20% by weight ⁰ /. The superabsorbent polymer of Example 7 was prepared in the same manner as in Example 1 and under the same surface crosslinking conditions.

After the surface crosslinking process, a superabsorbent polymer of Example 7 having a particle size of 150 ^η to 710 mm 3 was prepared by classifying to a standard mesh of ASTM standard. Comparative Example 1

The superabsorbent polymer of Comparative Example 1 was prepared in the same manner as in Example 1, except that the hydrophobic silica particles and the hydrophilic silica particle aqueous solution were not used during surface crosslinking with respect to the base resin powder (gel strength: 6,588 Pa). .

After the surface crosslinking process, the superabsorbent polymer of Comparative Example 1 having a particle size of 150 / to 710 / cc was prepared by classifying to a standard mesh of ASTM standard. Comparative Example 2

Base resin powder (gel strength: 6,588 Pa, compared with the same method as in Example 1, except that the hydrophobic silica particles were not added and the amount of the hydrophilic silica particles aqueous solution of ST-0 was 0.4 g at the time of surface crosslinking). The super absorbent polymer of Example 2 was prepared.

After the surface crosslinking process, the superabsorbent polymer of Comparative Example 2 having a particle size of 150 to 710 was prepared by classifying to a standard mesh of ASTM standard. Comparative Example 3

To the base resin powder (gel strength: 6,588 Pa), the hydrophobic silica particles of V130S were added in an amount of 0.05 parts by weight, and the surface crosslinking was carried out in the same manner as in Example 1 except that the aqueous hydrophilic silica particles were not used. In the same manner, the superabsorbent polymer of Comparative Example 3 was prepared.

After the surface crosslinking process, the superabsorbent polymer of Comparative Example 3 having a particle diameter of 150 zm to 710 was prepared by classifying to a standard mesh of ASTM standard. Comparative Example 4

A superabsorbent polymer of Comparative Example 3 was prepared in the same manner as in Example 1, except that the base resin powder was prepared using an amount of polyethylene glycol diacrylate (Mw = 523) as 1 g. The gel strength of this base resin powder was measured at 4,870 Pa.

After the surface crosslinking process, the superabsorbent polymer of Comparative Example 4 having a particle size of 150 to 710 was prepared by classifying to a standard mesh of ASTM standard. Comparative Example 5

A superabsorbent polymer of Comparative Example 5 was prepared in the same manner as in Example 2, except that the base resin powder was prepared using an amount of polyethylene glycol diacrylate (Mw = 523) as 1 g. The gel strength of this base resin powder was measured at 4,870 Pa.

After the surface crosslinking process, the superabsorbent polymer of Comparative Example 5 having a particle diameter of 150 to 710 m was prepared by classifying to a standard mesh of ASTM standard. Comparative Example 6

A superabsorbent polymer of Comparative Example 6 was prepared in the same manner as in Example 3, except that the base resin powder was prepared using an amount of polyethylene glycol diacrylate (Mw = 523) as 1 g. The gel strength of this base resin powder was measured at 4,870 Pa.

After the surface crosslinking process, the superabsorbent polymer of Comparative Example 6 having a particle size of 150 to 710 was prepared by classifying to a standard mesh of ASTM standard. For the superabsorbent polymers of Examples 1 to 7, and Comparative Examples 1 to 6, physical properties of CRC, AUP, SFC, and gel strength (G ′) were measured and evaluated. Physical property values are as shown in Table 2 below. In addition, from the measured CRC, AUP, the absorbance value of Equation 1 was calculated and shown in Table 2 together.

TABLE 2

Referring to Table 2, it was confirmed that the superabsorbent polymers of the examples exhibited higher absorption properties than the comparative example and exhibited higher gel strength and improved fluidity such as SFC.

Claims

Claims Claim 1 Base resin powder containing the 1st crosslinked polymer of the water-soluble ethylenically unsaturated monomer which at least one part has neutralized acidic group; And a surface crosslinking layer formed on the base resin powder, the surface crosslinking layer comprising a second crosslinking polymer further crosslinked with an alkylene carbonate having 2 to 5 carbon atoms, and comprising: The absorbance represented by Equation 1 is 45 to 65 g / g, and the flow inducibility (SFC; 10-7 η3 · 5/9) of physiological saline solution (0.685 wt% aqueous sodium chloride solution) is 70 to 190 1 (T7cm3 s / g) and a superabsorbent polymer having a gel strength (G ') of 9,000 to 18,000 Pa:

[Equation 1]

Absorbance = CRC + AUP

AUP is the high pressure indicates the absorption capacity of over 1 hour at O psi for a physiological saline solution (0.9 weight ^_0/0 aqueous sodium chloride solution) of a water-absorbent resin,

[Claim 2]

The superabsorbent polymer according to claim 1, further comprising inorganic particles dispersed on the surface crosslinking layer.

[Claim 3]

The hydrophobic inorganic particles according to claim 1, which are dispersed on the base resin powder and have a contact angle of 50 ^° or more with respect to water, A superabsorbent polymer dispersed on the surface cross-linking layer, further comprising hydrophilic inorganic particles having a contact angle of 10 ^° or less with respect to water.

[Claim 4]

The method of claim 3, wherein the hydrophobic inorganic particles include one or more selected from the group consisting of silica particles, titania particles and zirconia particles, wherein the hydrophilic inorganic particles are silica particles, titania particles, zirconia particles and laponite particles. Superabsorbent polymer comprising at least one member selected from the group consisting of.

[Claim 5]

The superabsorbent polymer according to claim 1, wherein the CRC of the superabsorbent polymer is 24 to 35 g / g. .

[Claim 6]

The superabsorbent polymer according to claim 1, wherein the AUP of the superabsorbent polymer is 22 to 27 g / g. '

[Claim 7]

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-methacryloylethanesulfonic acid, 2- Anionic monomers of (meth) acryloylpropanesulfonic acid or 2- (meth) acrylamide -2-methyl propane sulfonic acid and salts thereof; (Meth) acrylamide, N-substituted (meth) acrylates, ² -hydroxyethyl (meth) acrylates, 2-hydroxypropyl (meth) acrylates, mesopolyethylene glycol (meth) acrylates or polyethylene glycols ( 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; Super absorbent Suzy

[Claim 8]

The method of claim 1, wherein the first crosslinked polymer is a bis (meth) acrylamide having 8 to 12 carbon atoms, poly (meth) acrylate of a polyol having 2 to 10 carbon atoms and poly (meth) allyl of a polyol having 2 to 10 carbon atoms A superabsorbent polymer comprising a polymer in which the monomer is crosslinked in the presence of an internal crosslinking agent of one subphase selected from the group consisting of ethers.

[Claim 9]

The superabsorbent polymer according to claim 1, having a particle size of 150 to 850β ^η .

[Claim 10]

Cross-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 comprising a first crosslinked polymer;

Drying, pulverizing and classifying the hydrogel polymer to form a base resin powder having a gel strength ⁽ 3 ') of 5,000 Pa or more;

In the presence of a surface crosslinking liquid containing a hydrophilic inorganic particle having a contact angle of 10 ^° or less with respect to water and a surface crosslinking agent of alkylene carbonate having 2 to 5 carbon atoms, the base resin powder to which the hydrophobic inorganic particle is added is subjected to a heat treatment. Method for producing a super absorbent polymer comprising the step of crosslinking.

[Claim 1 11]

The method of claim 10, 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-methacryloylethanesulfonic acid, 2- Anionic monomers of (meth) acryloylpropanesulfonic acid or 2- (meth) acrylamide -2-methyl propane sulfonic acid and salts thereof; (Meth) acrylamide, N-substituted (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, mesopolyethylene glycol (meth) acrylate or polyethylene 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; The manufacturing method of the superabsorbent polymer containing.

[Claim 12]

The method of claim 10, wherein the internal crosslinking agent is bis (meth) acrylamide having 8 to 12 carbon atoms, poly (meth) acrylate of a poly 2 to 10 carbon atoms and poly (meth) allyl ether of a polyol of 2 to 10 carbon atoms Method for producing a super absorbent polymer comprising at least one member selected from the group consisting of.

[Claim 13]

The method of claim 10, wherein the base resin powder is ground and classified to have a particle size of 150 to 850.

[Claim 14]

The method of claim 10, wherein the hydrophobic inorganic particles include one or more selected from the group consisting of silica particles, titania particles and zirconia particles, the hydrophilic inorganic particles are silica particles, titania particles, zirconia particles and laponite particles Method for producing a super absorbent polymer comprising at least one member selected from the group consisting of.

[Claim 15]

The method according to claim 10, wherein the surface crosslinking step is performed ^at an initial temperature of 20 ^° C. to 130 ^° C. to a maximum temperature of 14 CTC to 200 ^° C. over 10 to 30 minutes. The method of manufacturing a super absorbent polymer, which is heated by heating and maintaining the maximum temperature for 5 to 60 minutes.