KR20190064978A - Super absorbent polymer and preparation method thereof - Google Patents

Abstract

The present invention relates to a superabsorbent polymer (SAP) and a method of producing the same. According to the present invention, an SAP having high water retention ability and absorption ate may be produced by using a particular internal crosslinker. The method comprises a step in which, in the presence of a polymerization initiator and an internal crosslinker, water-soluble ethylene-based unsaturated monomers having at least partially neutralized acid groups are polymerized via crosslinking to form hydrous gel phase polymers.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a superabsorbent resin,

The present invention relates to a superabsorbent resin having a high absorption rate and a method for producing the same.

Super Absorbent Polymer (SAP) is a synthetic polymer material capable of absorbing moisture of about 500 to 1,000 times its own weight. As a result, it is possible to develop a super absorbent polymer (SAM), an absorbent gel Material), and so on. Such a superabsorbent resin has started to be put into practical use as a sanitary article, and nowadays, in addition to sanitary articles such as diapers for children, there are currently used soil restoration materials for gardening, index materials for civil engineering and construction, sheet for seedling growing, freshness- And it is widely used as a material for fomentation and the like.

In many cases, such superabsorbent resins are widely used in sanitary materials such as diapers and sanitary napkins. In such sanitary materials, it is general that the superabsorbent resin is contained in a state spread in the pulp. In recent years, efforts have been made to provide sanitary materials such as diapers having a thinner thickness, and as a part thereof, there has been proposed a so-called pulpless diaper or the like in which the pulp content is reduced or further pulp is not used at all Development is progressing actively.

As such, in the case of sanitary materials in which the pulp content is reduced or pulp is not used, relatively high superabsorbent resins are contained in a high proportion, and these superabsorbent resin particles are inevitably contained in multiple layers in the sanitary ware. In order for the entire superabsorbent resin particles contained in the multilayer to absorb liquid such as urine more efficiently, it is necessary that the superabsorbent resin basically exhibits high absorption performance and absorption rate.

On the other hand, the absorption rate, one of the important physical properties of the superabsorbent resin, is related to the surface dryness of the product which touches the skin like a diaper. Generally, this absorption rate can be improved by increasing the surface area of the superabsorbent resin.

For example, a method of forming a porous structure on the particle surface of a superabsorbent resin by using a foaming agent has been applied. However, as a general foaming agent, there is a disadvantage in that a sufficient amount of porous structure can not be formed and the increase in the absorption rate is not large.

As another example, there is a method of widening the surface area by re-assembling the fine powder obtained in the process of producing the superabsorbent resin to form irregularly shaped porous particles. However, although the absorption rate of the superabsorbent resin can be improved by such a method, there is a limit in that the water retention capacity (CRC) and the pressure absorption capacity (AUP) of the resin are relatively lowered. As a result of such a trade-off relationship between the physical properties such as the absorption rate, the water-holding ability, and the pressure absorption ability of the superabsorbent resin, there is a serious demand for a manufacturing method capable of simultaneously improving these physical properties.

The present invention is to provide a superabsorbent resin having a high absorption rate.

The present invention also provides a method of producing the superabsorbent resin.

According to the present invention,

A) crosslinking and polymerizing a water-soluble ethylenically unsaturated monomer having an acidic group at least partially neutralized in the presence of a polymerization initiator and an internal crosslinking agent to form a hydrogel polymer;

B) drying, pulverizing and classifying the hydrogel polymer to form a base resin powder; And

C) surface crosslinking the base resin powder through heat treatment in the presence of a surface crosslinking agent to form superabsorbent resin particles,

Wherein the internal cross-linking agent comprises:

a1) a diol diacrylate crosslinking agent; And

a2) an alkylene carbonate compound having 3 to 10 carbon atoms,

A method for producing a superabsorbent resin is provided.

Further, according to the present invention,

And a base resin obtained by polymerizing and cross-linking a monomer composition in which at least a part of the acidic groups is neutralized with a water-soluble ethylenically unsaturated monomer,

Wherein the base resin comprises a surface cross-linked layer formed on the surface,

EDANA Method The centrifugal separation performance (CRC) measured according to WSP 241.3 is 25 g / g or more,

(T-20) of 140 seconds or less for absorbing 20 g of sodium chloride and an alcohol ethoxylate aqueous solution having 12 to 14 carbon atoms,

Thereby providing a superabsorbent resin.

In the superabsorbent resin according to the present invention, uniform polymerization can be carried out simultaneously with internal crosslinking using a specific combination of internal crosslinking agents at the time of polymerization, so that a high water-repellent ability and an absorption rate can be exhibited.

The terminology used herein is for the purpose of describing exemplary embodiments only and is not intended to be limiting of the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, the terms "comprising," "comprising," or "having ", and the like are intended to specify the presence of stated features, But do not preclude the presence or addition of one or more other features, integers, steps, components, or combinations thereof.

Also in the present invention, when referring to each layer or element being "on" or "on" each layer or element, it is meant that each layer or element is formed directly on each layer or element, Layer or element may be additionally formed between each layer, the object, and the substrate.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the invention is not intended to be limited to the particular forms disclosed, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a superabsorbent resin and a method for producing the same according to a specific embodiment of the present invention will be described in detail.

The superabsorbent resin has been evaluated to have important properties such as water retention capacity, pressure absorption capacity and absorption rate. For this purpose, conventionally, a large amount of pores are formed in the superabsorbent resin to rapidly suck water, And the like are known.

However, there is a limit in reducing the particle size of the superabsorbent resin, and when the inner pores are formed, since the gel strength is weakened, it is difficult to thin the article.

Therefore, a method of increasing the absorption rate by controlling the size and distribution of the inner pores in the process of producing the super absorbent resin by using the low-temperature foaming agent and the high-temperature foaming agent has been proposed. However, the control of the polymerization temperature is necessary to control the size and distribution of the pores. It is difficult to produce a base resin having a high level of CRC and a vortex time and a need for a method of manufacturing a superabsorbent resin having an improved absorption capacity and absorption rate exist.

The present inventors have found that when a polymerization and an internal cross-linking reaction are carried out, a specific combination of internal cross-linking agents is used to generate more stable and evenly bubbles at the same time as the internal cross-linking reaction, resulting in a high water- And thus the present invention has been completed.

Hereinafter, the superabsorbent resin of the present invention and its production method will be described in detail.

For reference, in the present specification, the term "polymer" or "polymer" means that the ethylenically unsaturated monomer is in a polymerized state, and may cover all moisture content ranges or particle diameter ranges. Among the above polymers, a polymer having a moisture content (moisture content) of about 40% by weight or more and being in a state before drying after polymerization can be referred to as a hydrogel polymer.

In addition, "base resin" or "base resin powder" means that the polymer is dried and pulverized into a powder form.

In the method for producing a superabsorbent resin according to an embodiment of the present invention, a monomer composition having an acidic group and including at least a part of the acidic groups neutralized, an ethylenically unsaturated monomer, a polymerization initiator, and an internal cross- To form a gel-like polymer.

The ethylenically unsaturated monomer may have an acidic group and at least a part of the acidic group is neutralized. Preferably, the monomer is partially neutralized with an alkali substance such as sodium hydroxide, potassium hydroxide, ammonium hydroxide or the like. At this time, the degree of neutralization of the ethylenically unsaturated monomer may be 40 to 95 mol%, or 40 to 80 mol%, or 45 to 75 mol%. The range of the degree of neutralization can be adjusted according to the final properties. However, if the degree of neutralization is too high, neutralized monomers may precipitate and polymerization may not be smoothly proceeded. On the other hand, if the degree of neutralization is too low, the absorption capacity of the polymer is greatly lowered, have.

Preferably, the ethylenically unsaturated monomer is a compound represented by the following formula (1): < EMI ID =

[Chemical Formula 1]

R ¹ -COOM ¹

In Formula 1,

R ¹ is an alkyl group having 2 to 5 carbon atoms containing an unsaturated bond,

M ¹ is a hydrogen atom, a monovalent or divalent metal, an ammonium group or an organic amine salt.

Preferably, the ethylenically unsaturated monomer includes at least one selected from the group consisting of acrylic acid, methacrylic acid, and monovalent metal salts, bivalent metal salts, ammonium salts, and organic amine salts thereof.

In addition, the concentration of the ethylenically unsaturated monomer in the monomer composition may be appropriately adjusted in consideration of the polymerization time and the reaction conditions, and preferably about 20 to about 90 wt%, or about 40 to about 70 wt% . Such a concentration range may be advantageous in controlling the grinding efficiency of the subsequent process polymer, while eliminating the need to remove unreacted monomers after polymerization using the gel phenomenon that occurs in the polymerization of high concentration aqueous solutions. However, if the concentration of the monomer is excessively low, the yield of the superabsorbent resin may be lowered. On the other hand, if the concentration of the monomer is excessively high, a part of the monomer may precipitate or the pulverization efficiency may be lowered upon pulverization of the polymer gel, and the physical properties of the superabsorbent resin may be deteriorated.

On the other hand, the monomer composition includes an internal crosslinking agent for improving the physical properties of the hydrogel polymer. The cross-linking agent is a cross-linking agent for forming cross-linking in the hydrous gel-like polymer, and is distinguished from a surface cross-linking agent for cross-linking the surface of the hydrous gel-like polymer in a subsequent step.

In the method for producing a superabsorbent resin according to an embodiment of the present invention,

a1) a diol diacrylate crosslinking agent; And

a2) an internal crosslinking agent comprising at least one alkylene carbonate compound having 3 to 10 carbon atoms is used.

The internal crosslinking agent enables introduction of crosslinking in the polymerization of the water-soluble ethylenically unsaturated monomer, and in general, a multifunctional functionalizing compound is used without any particular limitation.

However, in the present invention, a specific combination of internal crosslinking agents is used as described above.

Examples of the diol diacrylate compound include ethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, butane diol (meth) acrylate, (Meth) acrylate, diethylene glycol di (meth) acrylate, hexanediol di (meth) acrylate, triethylene glycol di (meth) acrylate, tripropylene glycol di (Meth) acrylate. Of these, polyethylene glycol diacrylate may be most preferably used.

Examples of the alkylene carbonate compound having 3 to 10 carbon atoms include a compound containing a linear or branched divalent alkylene group such as ethylene carbonate, propylene carbonate, and butylene carbonate, and a carbonate unit, Of these, ethylene carbonate and / or propylene carbonate can be preferably used, and it is most preferable to use ethylene carbonate and propylene carbonate at the same time.

Particularly, the ethylene carbonate and the propylene carbonate introduce internal crosslinking into the hydrous gel polymer and generate carbon dioxide. Stable control of the generation of air bubbles during the internal crosslinking reaction enables uniform foaming in the hydrogel polymer .

When a separate foaming agent is used in the production of a superabsorbent resin, a sufficient amount of foaming agent should be used in order to achieve a high absorption rate of the superabsorbent resin. However, as the foaming proceeds unevenly due to the amount of the foaming agent used, The problem of asymmetrically increasing may occur.

However, in the case of the present invention, it is possible to produce carbon dioxide at the same time as internal crosslinking by using a specific combination of internal crosslinking agent, so that a more uniform foamed polymer can be produced.

Further, in the subsequent surface cross-linking step, the crosslinking efficiency becomes high, and the surface cross-linking reaction can proceed even at a relatively low temperature. These results suggest that some of the alkylene carbonate used as an internal crosslinking agent may react only in one side and may be uniformly distributed in the dangling base resin to act in the surface reaction step .

Such an internal cross-linking agent may be used at about 1000 to about 10,000 ppm based on the above-described monomer weight. If the concentration of the internal cross-linking agent is too low, the absorption rate of the resin may be lowered and the gel strength may be weakened. On the contrary, when the concentration of the internal cross-linking agent is too high, the absorption power of the resin is lowered, which may be undesirable as an absorber.

The internal cross-linking agent is a mixture of a1) 100 parts by weight of a diol diacrylate cross-linking agent,

a2) from about 1 to about 50 parts by weight of an alkylene carbonate compound having from 3 to 10 carbon atoms.

When the diol diacrylate cross-linking agent and the alkylene carbonate compound having 3 to 10 carbon atoms are used in the above range, the cross-linking formed by the diol diacrylate cross-linking agent causes the cross-linking of the carbon dioxide The amount can be effectively controlled, uniform foaming can be achieved, and the foaming efficiency can be improved.

The internal cross-linking agent may be used together with the polycarboxylic acid-based copolymer.

The polycarboxylic acid-based copolymer can improve the dispersibility of the alkylene carbonate compound having 3 to 10 carbon atoms contained in the internal cross-linking agent. Thus, in the hydrogel polymer formed by cross-linking, the internal cross- Can be achieved. In addition, the polycarboxylic acid-based copolymer can alleviate the internal cross-linking reaction rate by the internal cross-linking agent and can produce a hydrogel polymer having a low water-soluble component. In the subsequent pulverization, a uniform, The resin powder can be produced.

Such polycarboxylic acid-based copolymers include polyacrylate-polyalkylene oxide-graft copolymers including repeating units represented by the following general formulas (1a) and (2a).

[Chemical Formula 1-a]

[Chemical Formula 1-b]

In the above formulas (1-a) and (1-b)

R 1, R 2 and R 3 are each independently hydrogen or an alkyl group having 1 to 6 carbon atoms,

RO is an oxyalkylene group having 2 to 4 carbon atoms,

M1 is hydrogen or sodium,

X is - (CO) O-,

m is an integer of 1 to 100,

n is an integer of 1 to 1000,

p is an integer of 1 to 150, and when p is 2 or more, -RO-, which is repeated two or more times, may be the same or different from each other.

According to an embodiment of the present invention, it is preferable that the polycarboxylic acid copolymer is used in an amount of about 1 to about 50 parts by weight per 100 parts by weight of the alkylene carbonate compound having 3 to 10 carbon atoms. When the polycarboxylic acid-based copolymer is used in a small amount, the alkylene carbonate compound may not be dispersed properly and may not uniformly progress during internal cross-linking and foaming. When the polycarboxylic acid-based copolymer is used in an excessively large amount, There is a problem that the absorption characteristic of the absorbent article is deteriorated.

It is preferable that the polycarboxylic acid-based copolymer has a weight average molecular weight of about 40,000 g / mol or less, about 25,000 to about 40,000 g / mol, or about 30,000 to about 35,000 g / mol, It may be preferable in terms of controlling the internal crosslinking and foaming properties.

As the polymerization initiator, a thermal polymerization initiator or a photopolymerization initiator may be used depending on the polymerization method. However, even with the photopolymerization method, a certain amount of heat is generated by ultraviolet irradiation or the like, and a certain amount of heat is generated as the polymerization reaction, which is an exothermic reaction, proceeds. .

Examples of the photopolymerization initiator include benzoin ether, dialkyl acetophenone, hydroxyl alkylketone, phenyl glyoxylate, benzyl dimethyl ketal ( at least one compound selected from the group consisting of benzyl dimethyl ketal, acyl phosphine, and alpha-aminoketone may be used. As a specific example of the acylphosphine, a commonly used lucyrin TPO, i.e., 2,4,6-trimethyl-benzoyl-trimethyl phosphine oxide can be used . More light polymerization initiators are disclosed in Reinhold Schwalm, "UV Coatings: Basics, Recent Developments and New Application (Elsevier 2007), "

As the thermal polymerization initiator, at least one compound selected from the group consisting of a persulfate-based initiator, an azo-based initiator, hydrogen peroxide, and ascorbic acid may be used. Specifically, examples of the persulfate-based initiator include sodium persulfate (Na2S2O8), potassium persulfate (K2S2O8), and ammonium persulfate (NH4) 2S2O8.

Azo-based initiators include 2,2-azobis (2-amidinopropane) dihydrochloride, 2,2-azobis- (N, N-dimethylene isobutyramidine dihydrochloride, 2- (carbamoylazo) isobutylonitrile, 2,2-azobis- (N, N-dimethylene) isobutyramidine dihydrochloride, Azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride), 4,2-diazabicyclo [ 4-azobis- (4-cyanovaleric acid), and the like. A wide variety of thermal polymerization initiators are described in the Odian book, " Principle of Polymerization (Wiley, 1981), " page 203, which is incorporated herein by reference.

The polymerization initiator may be added at a concentration of about 0.001 to about 1 part by weight based on 100 parts by weight of the ethylenically unsaturated monomer. That is, if the concentration of the polymerization initiator is too low, the polymerization rate may be slowed and the remaining monomer may be extracted in the final product in a large amount, which is not preferable. On the contrary, when the concentration of the polymerization initiator is too high, the chain of the polymer forming the network is shortened, and the physical properties of the resin may be lowered, such that the content of the water-soluble component is increased and the pressure absorption capacity is lowered.

In addition, the monomer composition may further contain additives such as a thickener, a plasticizer, a storage stabilizer, and an antioxidant, if necessary.

Such a monomer composition may be prepared in the form of a solution in which a raw material such as the above-mentioned monomer, polymerization initiator, internal cross-linking agent, etc. is dissolved in a solvent. At this time, usable solvents may be used without limitation of the constitution as long as they can dissolve the above-mentioned raw materials. Examples of the solvent include water, ethanol, ethylene glycol, diethylene glycol, triethylene glycol, 1,4-butanediol, propylene glycol, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate Methyl ethyl ketone, acetone, methyl amyl ketone, cyclohexanone, cyclopentanone, diethylene glycol monomethyl ether, diethylene glycol ethyl ether, toluene, xylene, butyrolactone, carbitol, methyl cellosolve acetate, N, N-dimethylacetamide, or a mixture thereof.

The formation of the hydrogel polymer through polymerization of the monomer composition can be carried out by a conventional polymerization method, and the process is not particularly limited. As a non-limiting example, the polymerization method is divided into thermal polymerization and photopolymerization depending on the type of polymerization energy source. In the case of conducting the thermal polymerization, the polymerization may proceed in a reactor having a stirring axis such as a kneader, It is possible to proceed in a reactor equipped with a movable conveyor belt.

For example, the hydrogel polymer may be obtained by introducing the monomer composition into a reactor such as a kneader equipped with a stirring shaft and supplying hot air thereto or by heating the reactor to heat-polymerize. At this time, the hydrogel polymer discharged to the reactor outlet depending on the shape of the stirring shaft provided in the reactor can be obtained as particles of several millimeters to several centimeters. Specifically, the resulting hydrogel polymer can be obtained in various forms depending on the concentration and the injection rate of the monomer composition to be injected, and a hydrogel polymer having a particle diameter of about 2 to about 50 mm (weight average) can be obtained.

And, as another example, in the case of carrying out photopolymerization on the monomer composition in a reactor equipped with a movable conveyor belt, a hydrogel polymer in the form of a sheet can be obtained. The thickness of the sheet may vary depending on the concentration of the monomer composition to be injected and the rate of injection. Usually, the thickness of the sheet is adjusted to about 0.5 to about 5 cm in order to uniformly polymerize the entire sheet, .

The hydrogel polymer formed by such a method may exhibit a water content of about 40 to 80% by weight. Here, the moisture content may be the weight of water in the total weight of the hydrogel polymer, minus the weight of the hydrogel polymer in dry state. Specifically, it can be defined as a value calculated by measuring weight loss due to moisture evaporation in the polymer in the process of raising the temperature of the polymer through infrared heating. At this time, the drying condition may be set to a temperature of about 180 at room temperature and then maintained at about 180, and a total drying time may be set to about 20 minutes including about 5 minutes of temperature rising.

On the other hand, the method of producing the superabsorbent resin includes a step of drying the hydrogel polymer formed through the above-mentioned steps.

Here, if necessary, a step of pulverizing (coarsely crushing) the hydrogel polymer may be further performed before the drying in order to increase the efficiency of the drying step.

As a non-limiting example, the pulverizers usable for the above-mentioned coarse grinding include a vertical pulverizer, a turbo cutter, a turbo grinder, a rotary cutter mill, For example, a cutter mill, a disc mill, a shred crusher, a crusher, a chopper, a disc cutter, and the like.

At this time, the coarse pulverization may be performed such that the diameter of the hydrogel polymer is about 2 to about 10 mm. That is, in order to increase the drying efficiency, the hydrogel polymer is preferably pulverized into particles of 10 mm or less. However, since excessive aggregation may occur during the pulverization, the hydrogel polymer is preferably pulverized into particles of about 2 mm or more.

And, when the coarse pulverization step is performed before the drying step of the hydrogel polymer, the polymer has a high water content, so that the polymer may stick to the surface of the pulverizer. In order to minimize such a phenomenon, the crude pulverization step may be carried out by adding steam, water, a surfactant, an anti-flocculation inhibitor such as Clay or Silica, A crosslinking agent comprising a hydroxyl group-containing initiator, an azo-based initiator, an azo-based initiator, hydrogen peroxide and a thermal polymerization initiator such as ascorbic acid, an epoxy crosslinking agent, a diol crosslinking agent, an acrylate of a bifunctional group or a polyfunctional group having three or more functional groups, A crosslinking agent such as a compound of a monofunctional group may be added.

On the other hand, the drying of the hydrogel polymer immediately after the coarse pulverization or polymerization as described above can be carried out at a temperature of about 120 to about 250, or about 150 to about 200, or about 160 to about 180, The temperature of the thermal medium supplied for drying or the temperature inside the drying reactor including the thermal medium and the polymer in the drying process). That is, when the drying temperature is low and the drying time is long, the physical properties of the final resin may be deteriorated. To prevent this, the drying temperature is preferably 120 or more. In addition, when the drying temperature is higher than necessary, only the surface of the hydrogel polymer is dried, so that the generation of fine powder may be increased in the pulverizing step to be described later, and the physical properties of the final resin may be lowered. .

In this case, the drying time in the drying step is not particularly limited, but may be adjusted to 20 to 90 minutes under the drying temperature in consideration of process efficiency and the like.

The drying method of the drying step may be applied to the drying method of the hydrogel polymer as long as it can be used normally. Specifically, the drying step may be performed by hot air supply, infrared irradiation, microwave irradiation, ultraviolet irradiation, or the like.

The polymer dried in this way may exhibit a water content of from about 0.1 to about 10 weight percent. That is, when the water content of the polymer is less than about 0.1% by weight, an increase in manufacturing cost due to excessive drying and degradation of the cross-linking polymer may occur, which is not advantageous. If the water content of the polymer exceeds about 10% by weight, defects may occur in the subsequent process, which is undesirable.

Thereafter, a step of pulverizing the dried polymer is carried out. The milling step may be performed to optimize the surface area of the dried polymer so that the milled polymer has a particle size of about 150 to about 850 탆.

The pulverizer may be a conventional pulverizer such as a pin mill, a hammer mill, a screw mill, a roll mill, a disc mill, and a jog mill. . Further, in order to manage the physical properties of the superabsorbent resin to be finally produced, the step of selectively classifying the particles having a particle diameter of about 150 to about 850 탆 in the polymer particles obtained through the above-mentioned pulverization step may be further performed.

Through the above-mentioned steps, the step of surface-crosslinking the pulverized polymer, that is, the base resin powder, with the surface cross-linking agent is carried out.

The surface crosslinking is a step of inducing a crosslinking reaction on the surface of the pulverized polymer in the presence of a surface crosslinking agent to form a superabsorbent resin having improved physical properties. Through such surface crosslinking, a surface cross-linked layer is formed on the surface of the ground polymer particles.

The surface modification can be carried out by a conventional method for increasing the cross-linking density of the polymer particle surface, and can be carried out by, for example, a method of mixing a solution containing a surface cross-linking agent and the pulverized polymer, .

Herein, the surface cross-linking agent is a compound capable of reacting with a functional group contained in the polymer, and its composition is not particularly limited.

However, as a non-limiting example, it is preferable to use an alkylene carbonate compound having 3 to 10 carbon atoms as the surface cross-linking agent.

Specific examples of such alkylene carbonate compounds include 1,3-dioxolane-2-one, 4-methyl-1,3-dioxolane-2-one, 4,5- 4-dimethyl-1,3-dioxolane-2-one, 4-ethyl-1,3-dioxolan- Dioxan-2-one, 4-methyl-1,3-dioxan-2-one, 4,6-dimethyl- 2-one, 1,3-dioxepan-2-one, and the like.

According to an embodiment of the present invention, in addition to the alkylene carbonate compound described above, the surface cross-linking agent may further contain, in addition to the alkylene carbonate compound described above, a polyhydric alcohol having 2 to 10 carbon atoms, an amino alcohol having 1 to 10 carbon atoms, an oxetane compound having 2 to 10 carbon atoms, A magnesium hydroxide, an aluminum hydroxide, an iron hydroxide, a calcium chloride, a magnesium chloride, an aluminum chloride, and an iron chloride, and the like.

According to another embodiment of the present invention, the surface cross-linking agent is an alkoxypolyalkylene glycol mono (meth) acrylate-based monomer including methoxypolyethylene glycol monomethacrylate (MPEGMAA) and the like; And random copolymers derived from hydrophilic monomers such as (meth) acrylate-based monomers including acrylic acid and (meth) acrylic acid; And may include polycarboxylic acid-based compounds.

Specific examples of such polycarboxylic acid-based compounds are disclosed in Korean Patent Publication No. 2015-0143167.

At this time, the content of the surface cross-linking agent may be appropriately adjusted according to the type of cross-linking agent, reaction conditions, etc., and preferably about 0.001 to about 5 parts by weight with respect to 100 parts by weight of the ground polymer. If the content of the surface cross-linking agent is too low, the surface cross-linking may not be performed properly and the physical properties of the final resin may be deteriorated. On the contrary, when an excessive amount of the surface cross-linking agent is used, the absorption capacity of the resin may be lowered due to excessive surface cross-linking reaction, which is not preferable.

Further, water may be added additionally when the surface cross-linking agent is added. The addition of the surface cross-linking agent and the water in this way can induce even dispersion of the surface cross-linking agent and further optimize the penetration depth of the surface cross-linking agent to the polymer particles. In consideration of this purpose and effect, the amount of water added with the surface cross-linking agent can be adjusted to about 0.5 to about 10 parts by weight based on 100 parts by weight of the ground polymer.

Meanwhile, in the present invention, the surface cross-linking may be performed at about 180 to about 250. When the surface cross-linking is carried out at the above temperature, the surface cross-linking density can be increased, which is preferable. More preferably, the surface cross-linking is at least about 190, less than about 240, less than about 230, less than about 220, less than about 210, or less than about 200.

Also, the surface cross-linking reaction may proceed for about 50 minutes or more. That is, the surface cross-linking reaction may be carried out in order to prevent the polymer particles from being damaged due to excessive reaction while lowering the surface cross-linking reaction to a minimum. Also, the reaction can proceed in about 120 minutes or less, about 100 minutes or less, or about 60 minutes or less.

According to another embodiment of the present invention,

And a base resin obtained by polymerizing and cross-linking a monomer composition in which at least a part of the acidic groups is neutralized with a water-soluble ethylenically unsaturated monomer,

Wherein the base resin comprises a surface cross-linked layer formed on the surface,

EDANA Method The centrifugal separation performance (CRC) measured according to WSP 241.3 is 25 g / g or more,

(T-20) of 140 seconds or less for absorbing 20 g of sodium chloride and an alcohol ethoxylate aqueous solution having 12 to 14 carbon atoms,

A superabsorbent resin is provided.

In particular, the superabsorbent resin of the present invention can stably generate bubbles by using a specific combination of internal crosslinking agents during polymerization and internal crosslinking reaction, and can exhibit high water-holding ability and absorption rate.

The ethylenically unsaturated monomer is preferably a compound represented by the following formula (1): < EMI ID =

[Chemical Formula 1]

R ¹ -COOM ¹

In Formula 1,

R ¹ is an alkyl group having 2 to 5 carbon atoms containing an unsaturated bond,

M ¹ is a hydrogen atom, a monovalent or divalent metal, an ammonium group or an organic amine salt.

Preferably, the ethylenically unsaturated monomer includes at least one selected from the group consisting of acrylic acid, methacrylic acid, and monovalent metal salts, bivalent metal salts, ammonium salts, and organic amine salts thereof.

Here, the ethylenically unsaturated monomer may have an acidic group and at least a part of the acidic group may be neutralized. Preferably, the monomer is partially neutralized with an alkylene material such as sodium hydroxide, potassium hydroxide, ammonium hydroxide or the like. Wherein the degree of neutralization of the ethylenically unsaturated monomer may be about 40 to about 95 mole percent, or about 40 to about 80 mole percent, or about 45 to about 75 mole percent. The range of the degree of neutralization can be adjusted according to the final properties. However, if the degree of neutralization is too high, neutralized monomers may precipitate and polymerization may not be smoothly proceeded. On the other hand, if the degree of neutralization is too low, the absorption capacity of the polymer is greatly lowered, have.

In addition, the cross-

a1) a diol diacrylate crosslinking agent; And

a2) an internally crosslinked bond formed by at least one alkylene carbonate compound having 3 to 10 carbon atoms.

The characteristics of the internal cross-linking are as described above.

In the present invention, the cross-linked polymer may have a centrifugal separation capacity (CRC) of about 30 g / g or more and about 35 g / g or more as measured according to EDANA method WSP 241.3. The upper limit value of the water repellency (CRC) is not particularly limited, but may be, for example, about 50 g / g or less, or about 45 g / g or less, or about 42 g / g or less.

In addition, the crosslinked polymer may have an absorption rate by the vortex method of 42 seconds or less, or about 41 seconds or less, or about 40 seconds or less. The lower limit value of the absorption rate is not particularly limited, but may be, for example, about 15 seconds or more, or about 20 seconds or more, or about 30 seconds or more.

In this case, the storage ability and the absorption rate may be adjusted by adding a base resin, which is a cross-linked polymer in the form of a powder, after drying and crushing the monomer composition after polymerization of the monomer composition before forming the surface cross- . ≪ / RTI >

When the surface cross-linked layer is formed on the base resin, the pressure absorption capacity (AUP) generally increases and the absorption speed (vortex time) also improves, but the coverage performance (CRC) decreases. Therefore, it is very important to manufacture a base resin having a high coverage ability in order to secure the physical properties of the final product, considering the tendency of decreasing the water-holding ability. The superabsorbent resin in which the surface cross-linked layer is formed with respect to the base resin having high water retention ability is less likely to deteriorate the water repellency, and at the same time, it can have improved pressure absorption ability and absorption speed, and thus a higher quality resin can be obtained .

For example, a superabsorbent resin having a surface cross-linked layer formed on a cross-linked polymer (base resin) having the above-mentioned water-repellency and absorption rate has a centrifugal separation capacity (CRC) measured according to EDANA method WSP 241.3 of about 25 g g or more, or about 28 g / g or more, about 45 g / g or less, or about 40 g / g or less, or about 36 g / g or less.

The centrifugal separation capacity (CRC) measured according to the EDANA method WSP 241.3 can be expressed by the following equation (1)

[Equation 1]

CRC (g / g) = {[W2 (g) - W1 (g)] / W0 (g)

In the above equation (1)

W0 (g) is the weight (g) of the resin,

W1 (g) is the weight (g) of the apparatus measured after dehydration at 250G for 3 minutes using a centrifuge without using a resin,

W2 (g) is the weight (g) of the device measured by immersing the resin in 0.9% by mass of physiological saline at room temperature for 30 minutes, then dehydrating at 250G for 3 minutes using a centrifuge, and then measuring the resin.

The measurement of the absorption rate by the vortex method was carried out by adding 50 ml of saline to a 100 ml beaker together with a magnetic stirring bar, setting the stirring speed of the magnetic stirring bar at 600 rpm using a stirrer, adding 2.0 g of the resin to the stirred saline The time is measured and the time (unit: second) taken until the vortex disappears in the beaker is measured as the vortex time.

In the superabsorbent resin of one embodiment, 1 g of the superabsorbent resin has a T-20 showing a time required for absorbing 20 g of sodium chloride and an alcohol ethoxylate aqueous solution having a carbon number of 12 to 14 of 140 seconds or less, or about 90 to about 120 seconds , Preferably from about 95 to about 110 seconds.

Such T-20 can be prepared, for example, by making an aqueous solution of 9 g of sodium chloride and 1 g of Lorodac (main component: alcohol ethoxylate with 12 to 14 linear carbon atoms, CAS # 68439-50-9) dissolved in 1 L of distilled water, 1 g of resin can be calculated and measured as the time it takes to absorb 20 g of this aqueous solution. The specific measurement method of such T-20 is described in detail in European Patent Application No. 2535027 p13 to p18.

According to another embodiment of the present invention, the superabsorbent resin may have a pressure sorption capacity (AAP) of at least about 20 g / g, preferably at least about 22 g / g, or at least about 25 g / g at 0.7 psi have.

The superabsorbent resin may have a physiological saline flow conductivity (SFC) value of about 50 to about 70 (x 10 ^-7 cm ³ sec / g).

Best Mode for Carrying Out the Invention Hereinafter, the function and effect of the present invention will be described in more detail through specific examples of the present invention. It is to be understood, however, that these embodiments are merely illustrative of the invention and are not intended to limit the scope of the invention.

<Examples>

Production Example: Production of Polycarboxylic Acid Copolymer

400 parts by weight of ion exchange water was charged into a 3 L four-necked flask reactor equipped with a stirrer, a thermometer, a nitrogen inlet and a circulating condenser, and the inside of the reaction vessel was replaced with nitrogen under stirring and heated to 75 in a nitrogen atmosphere.

After adding 2 parts by weight of ammonium persulfate to the reactor, 600 parts by weight of methoxypolyethylene glycol monomethacrylate (average molar number of addition of ethylene oxide (EO): about 50 moles), 99.6 parts by weight of methacrylic acid, 190 parts by weight, a mixed solution of 5 parts by weight of 3-mercaptopropionic acid and 60 parts by weight of water, and 150 parts by weight of an aqueous ammonium persulfate solution having a concentration of 3% by weight were continuously introduced at a uniform rate for 4 hours. After completion of the addition, 5 parts by weight of an aqueous ammonium persulfate solution having a concentration of 3% by weight was added thereto at a time.

Thereafter, the internal temperature of the reactor was raised to 85, and then the temperature was maintained at 85 for 1 hour to complete the polymerization reaction.

The polycarboxylic acid copolymer thus prepared had a weight average molecular weight of 31,000 as determined by gel permeation chromatography (GPC).

&Lt; Example 1 >

42 parts by weight of caustic soda (NaOH) and 143 parts by weight of water were mixed with 100 parts by weight of acrylic acid monomer, and 0.15 part by weight of sodium persulfate as a thermal polymerization initiator and 0.15 part by weight of diphenyl (2,4,6- Trimethylbenzoyl) -phosphine oxide, 0.5 parts by weight of polyethylene glycol diacrylate as an internal cross-linking agent, 0.0201 parts by weight of ethylene carbonate, 0.2 parts by weight of sodium bicarbonate and 0.01 part by weight of sucrose were added to prepare a monomer composition.

The monomer composition was irradiated with ultraviolet light for 1 minute while being flowed at a flow rate of 243 kg / hr on a polymerization belt of a continuous type belt polymerization reactor having an internal temperature of 40 and an ultraviolet irradiation device having an intensity of 10 mW as a mercury UV lamp light source, And the polymerization reaction was further carried out in a state of no light source for 2 minutes.

After the polymerization, the gel-type polymerized sheet was first cut using a shredder-type cutter and then coarsely crushed through a meat chopper. Thereafter, the resultant was dried at a temperature of 180 ° C for 40 minutes through a hot-air drier, pulverized using a rotary mixer, and classified into 180 μm to 850 μm to prepare a base resin.

4 wt% of water, 1 wt% of ethanol, 1 wt% of ethylene carbonate, 0.1 wt% of the polycarboxylic acid copolymer disclosed in Production Example 1 of Korean Laid-Open Patent Application No. 2015-0143167 were added to the base resin at a rate of 80 kg / %, In a high-speed mixing mixer. The resin uniformly mixed with the surface cross-linking solution was subjected to a surface treatment reaction at 185 for 1 hour in a paddle type mixer to obtain a superabsorbent resin.

&Lt; Example 2 >

In Example 1, a superabsorbent resin was obtained in the same manner as in Example 1, except that 233 parts by weight of propylene carbonate was used instead of ethylene carbonate in the internal crosslinking.

&Lt; Example 3 >

In Example 1, a superabsorbent resin was obtained in the same manner as in Example 1, except that ethylene carbonate was replaced by 101 parts by weight of ethylene carbonate and 117 parts by weight of propylene carbonate at the time of internal crosslinking.

<Example 4>

A superabsorbent resin was obtained in the same manner as in Example 1, except that 0.01 part by weight of the polycarboxylic acid-based copolymer of the preparation example was used at the time of internal crosslinking in Example 1.

&Lt; Example 5 >

A superabsorbent resin was obtained in the same manner as in Example 2, except that 0.01 part by weight of the polycarboxylic acid-based copolymer of the preparation example was used at the time of internal crosslinking in Example 2.

&Lt; Example 6 >

In Example 3, a superabsorbent resin was obtained in the same manner as in Example 3, except that 0.01 part by weight of the polycarboxylic acid-based copolymer of the preparation example was used at the time of internal crosslinking.

&Lt; Example 7 >

In Example 1, a superabsorbent resin was obtained in the same manner as in Example 1, except that 0.25 parts by weight of polyethylene glycol diacrylate and 0.1 parts by weight of ethylene carbonate were used at the time of internal crosslinking.

&Lt; Comparative Example 1 &

In Example 1 above. A superabsorbent resin was obtained in the same manner as in Example 1, except that ethylene carbonate was not used during internal crosslinking.

&Lt; Comparative Example 2 &

In Example 1, a superabsorbent resin was obtained in the same manner as in Example 1, except that 0.174 parts by weight of 1,3-propanediol was used instead of ethylene carbonate in the internal crosslinking.

&Lt; Comparative Example 3 &

In Example 1, a superabsorbent resin was obtained in the same manner as in Example 1, except that 0.288 parts by weight of allyl methacrylate was used instead of ethylene carbonate in the internal crosslinking.

Composition characteristics of each of the Examples and Comparative Examples are summarized in Table 1 below.

Internal crosslinking agent (ppm) Production Example (ppm) PEGDA 1,3-PDO AMA PC EC Example 1 5000 0 0 0 201 0 Example 2 5000 0 0 233 0 0 Example 3 5000 0 0 117 101 0 Example 4 5000 0 0 0 201 100 Example 5 5000 0 0 233 0 100 Example 6 5000 0 0 117 101 100 Example 7 2500 0 0 0 1000 0 Comparative Example 1 5000 0 0 0 0 0 Comparative Example 2 5000 174 0 0 0 0 Comparative Example 3 5000 0 288 0 0 0

* PEGDA: PEGDA 400 (Polyethylene glycol diacrylate)

* 1,3-PDO: 1,3-Propane diol

* AMA: Ally methacrylate

* EC: Ethylene carbonate

* PC: Propylene carbonate

Production Example: A polycarboxylic acid-based copolymer

The base resin and the superabsorbent resin thus prepared were measured for physical properties according to the following methods and summarized in Tables 2 and 3 below.

Function  ( CRC , Centrifugal Retention Capacity)

The measurement of water storage capacity was based on EDANA method WSP 241.3. 0.2 g of a sample of the prepared superabsorbent resin composition is put into a tea bag and precipitated in a 0.9% saline solution for 30 minutes. Then, dehydration was performed for 3 minutes with a centrifugal force of 250G (gravity), and the amount of the saline solution was measured.

Pressure Absorption capacity  (AAP, Absorption Against Pressure)

The measurement of pressure absorption capacity was based on EDANA method WSP 241.3. A 0.9 g sample of the prepared superabsorbent resin composition is placed in a cylinder specified by EDANA, and a pressure of 0.7 psi is applied between the piston and the piston. The amount of absorbed 0.9% saline solution was measured for 60 minutes.

Physiological saline flow induction ( SFC : Saline Flow Conductivity)

Was measured according to the method described in [0184] to [0189] of column 16 of U.S. Patent Publication No. 2009-0131255.

T-20

An aqueous solution was prepared by dissolving 9 g of sodium chloride and 1 g of Lorodac (main component: alcohol having 12 to 14 carbon atoms, ethoxylate, CAS # 68439-50-9) in 1 L of distilled water, and 1 g of the superabsorbent resin absorbed 20 g of this aqueous solution The time required was calculated and measured. The specific measurement method of such T-20 is described in detail in European Patent Application No. 2535027 p13 to p18.

Bulk density

100 g of the superabsorbent resin was flowed through a standard fluidity measuring device orifice to a volume of 100 ml container and the superabsorbent resin was leveled to be horizontal to adjust the volume of the superabsorbent resin to 100 ml, The weight of water was measured. The apparent density corresponding to the weight of the superabsorbent resin per unit volume was obtained by dividing the weight of the superabsorbent resin by the volume of the superabsorbent resin (100 ml).

Surface tension

0.5 g of a sample of the superabsorbent resin composition was placed in 50 g of 0.9% physiological saline, stirred at 220 rpm for 3 minutes, and then the surface tension was measured using a K100 Force Tensiometer, K100.

Water-soluble component

1.0 g of the sample of the superabsorbent resin composition was placed in a 250 mL Erlenmeyer flask and placed in 200 mL of 0.9% NaCl solution. After free swelling for 16 hours with stirring at 250 rpm, the aqueous solution was filtered with a filter paper .

The filtered solution was first titrated to pH 10 with 0.1 N caustic soda solution and then back titrated to pH 2.7 with 0.1 N hydrogen chloride solution. From the obtained titration amount, the content of water-soluble component in heavy absorptive resin %) Was calculated.

(Base resin) CRC (g / g) Water content (%) Vortex (sec) Example 1 35 11 40 Example 2 36 11 40 Example 3 35 11 40 Example 4 36 10 38 Example 5 36 10 38 Example 6 36 10 38 Example 7 37 11 38 Comparative Example 1 37 12 45 Comparative Example 2 36 11 44 Comparative Example 3 34 11 44

(High absorbency resin) CRC
(g / g) AAP
(g / g) SFC
(10 ^-7
cm &lt; ³ &gt; sec / g) T20
(second) Water content (%) Apparent Specific Gravity (g / ml) Surface tension
(mN / m) Example 1 28.1 25.9 56 104 8 0.58 71 Example 2 28.3 25.8 53 105 8 0.58 71 Example 3 28.2 25.7 53 105 8 0.58 71 Example 4 28.3 25.6 58 101 7 0.58 70 Example 5 28.4 25.6 52 100 7 0.58 70 Example 6 28.4 25.5 54 100 7 0.58 70 Example 7 28.7 25.5 50 102 8 0.58 71 Comparative Example 1 28.8 25.6 42 146 8 0.59 71 Comparative Example 2 28.2 25.6 49 142 8 0.59 71 Comparative Example 3 27.9 25.5 52 147 8 0.59 71

Referring to the table, it can be seen that the base resin and the superabsorbent resin prepared according to the present example have a high CRC value and a very high absorption rate.

Particularly, it can be seen that the superabsorbent resin according to the present invention has a very high absorption rate represented by T-20, which is obtained by using a specific combination of internal crosslinking agents during internal crosslinking, And the crosslinking efficiency is increased.

In general, when dispersing using a low molecular weight dispersing agent or an emulsifying agent, the surface tension may be lowered. In the case of the superabsorbent resin according to one embodiment of the present invention, the combination of the specific internal crosslinking agent and the polycarboxyl It is possible to clearly confirm that the surface tension is not lowered.

Claims (11)

A) crosslinking and polymerizing a water-soluble ethylenically unsaturated monomer having an acidic group at least partially neutralized in the presence of a polymerization initiator and an internal crosslinking agent to form a hydrogel polymer;
B) drying, pulverizing and classifying the hydrogel polymer to form a base resin powder; And
C) surface crosslinking the base resin powder through heat treatment in the presence of a surface crosslinking agent to form superabsorbent resin particles,
Wherein the internal cross-linking agent comprises:
a1) a diol diacrylate crosslinking agent; And
a2) an alkylene carbonate compound having 3 to 10 carbon atoms,
A method for producing a superabsorbent resin.
The method according to claim 1,
Wherein the water-soluble ethylenically unsaturated monomer is a compound represented by the following formula (1): &lt; EMI ID =
[Chemical Formula 1]
R1-COOM1
In Formula 1,
R1 is an alkyl group having 2 to 5 carbon atoms containing an unsaturated bond,
M1 is a hydrogen atom, a monovalent or divalent metal, an ammonium group or an organic amine salt.
The method according to claim 1,
The internal cross-
a1) 100 parts by weight of a diol diacrylate crosslinking agent,
a2) 1 to 50 parts by weight of an alkylene carbonate compound having 3 to 10 carbon atoms;
A method for producing a superabsorbent resin.
The method according to claim 1,
Wherein the internal cross-linking agent is used at 1,000 to 10,000 ppm based on the weight of the monomer.
The method according to claim 1,
Wherein the internal cross-linking agent is used together with the polycarboxylic acid-based copolymer.
6. The method of claim 5,
Based on 100 parts by weight of the alkylene carbonate compound having 3 to 10 carbon atoms,
Wherein the polycarboxylic acid-based copolymer is used in an amount of 1 to 50 parts by weight.
The method according to claim 1,
Wherein the surface cross-linking agent comprises at least one alkylene carbonate compound having 3 to 10 carbon atoms.
The method according to claim 1,
Wherein the heat treatment temperature is from 175 to 200 ° C.
And a base resin obtained by polymerizing and cross-linking a monomer composition in which at least a part of the acidic groups is neutralized with a water-soluble ethylenically unsaturated monomer,
Wherein the base resin comprises a surface cross-linked layer formed on the surface,
EDANA Method The centrifugal separation performance (CRC) measured according to WSP 241.3 is 25 g / g or more,
(T-20) of 140 seconds or less for absorbing 20 g of sodium chloride and an alcohol ethoxylate aqueous solution having 12 to 14 carbon atoms,
Highly absorbent resin.
10. The method of claim 9,
(SFC) of physiological saline is 50 to 70 (x 10 &lt; ^-7 &gt; cm &lt; ³ &gt; sec / g).
10. The method of claim 9,
Absorbing capacity (AAP) of not less than 20 g / g at 0.7 psi.