KR100409069B1 - A method of preparing resin absorbing water - Google Patents

Abstract

The present invention relates to a method for preparing a water absorbent resin, and more particularly, in a method for preparing a water absorbent resin by reacting a monomer by reverse phase suspension, a monomer, a compound represented by the formula (1), a compound represented by the formula (2), and these The present invention relates to a method for producing an amorphous absorbent resin having an average particle size of 850 µm or less by continuously reacting an anionic emulsifier, an initiator, and an aqueous monomer solution containing water with a solvent, followed by drying.

[Formula 1]

[Formula 2]

(In Formulas 1 and 2, R ₁ is a hydrophobic alkyl or alkylallyl group, and has 6 to 22 carbon atoms, and M is hydrogen (H), sodium (Na), potassium (K), lithium (Li) from the group consisting of Is selected, R ₂ is ethylene or propylene and n is an integer from 2 to 50.)

Description

A method of preparing resin absorbing water

[TECHNICAL FIELD OF THE INVENTION]

The present invention relates to a method for producing a water absorbent resin, and more particularly, in a method for preparing a water absorbent resin by reverse phase suspension polymerization, the absorption amount, absorption rate and particle size can be easily controlled and have a narrow particle distribution. In particular, the present invention relates to a method for producing a water absorbent resin capable of mass production.

[Private Technology]

Absorbent resins are used for hygiene products, such as disposable diapers and sanitary napkins, and for agriculture, such as soil modifiers that prevent loss of repair materials or fertilizers. In recent years, the use as a blocker for preventing the propagation of fire in the case of fire has been widely used.

In general, the water absorbent resin can be roughly classified into the following four types depending on the chemical structure. First, a crosslinked (co) polymer of acrylate or acrylamide. Second, acrylonitrile graft copolymer of cellulose or starch. Thirdly, a crosslinked copolymer of maleic anhydride. Fourth, crosslinked polyethylene oxide.

Most of the commercially available water absorbent resins are prepared by a solution polymerization method using water as a solvent and a reverse phase suspension polymerization method using a solvent having a very low solubility in water. The reverse phase suspension polymerization method has a smaller particle size distribution than the solution polymerization method, less residual monomers harmful to the human body, and is not widely used commercially in spite of easy optimization of physical properties. This is because there is a problem that it is difficult to manufacture amorphous particles. In addition, the reverse phase suspension polymerization method has a problem in that the production cost increases because a large amount of a solvent in which the absorbent resin is not dissolved.

US Pat. No. 5,180,798 introduces a multistage polymerization process as an example of preparing absorbent resins. The patent discloses dispersing a nonionic emulsifier in n-heptane in n-heptane at a relatively high temperature. After preparing the water absorbent resin using a monomer solution, the reaction product was cooled to 10 ° C. according to the type of emulsifier used, and then the remaining monomer solution was absorbed into the water absorbent resin prepared in the first step, and the monomer solution was raised to the second step. It is presented how to complete it. However, this method is not commercially efficient.

In addition, US Pat. No. 5,652,309 also introduces a multi-stage polymerization method, which prepares an absorbent resin using an emulsifier having a hydrophile lipophile balance (HLB) of 1-9 in the first step and then cools it to 50 ° C. In the second step, after the cooling, an emulsifier having a higher HLB (HLB is 9-12) than that used in the first step is dissolved in the remaining monomers and then absorbed into the absorbent resin prepared in the first step to prepare amorphous particles. The method has a relatively high absorption temperature compared to US Pat. No. 5,180,798, but still has a disadvantage in that the productivity is low.

In general, when preparing the absorbent resin by the reverse phase suspension polymerization method, it is necessary to obtain amorphous particles in addition to the above problems, and to minimize the decrease in the absorption rate due to the nonionic or polymer emulsifier mainly used to impart the stability of the particles. There is a problem that must be done. In addition, the monomers used to prepare the absorbent resins, for example, acrylic acid or acrylamide and monomers copolymerizable therewith, have a very high heat of reaction, making it difficult to terminate the reaction in a short time and having a low ratio of monomers and solvents.

In order to overcome the above problems, the present inventors are polymerized by a reverse phase suspension polymerization method, and the particle size and its distribution can be controlled by continuously adding a monomer aqueous solution without having to lower the temperature. It is an object of the present invention to provide a method for producing an absorbent resin capable of mass-producing the absorbent resin in a short time.

In order to achieve the above object, the present invention provides a method for preparing a water absorbent resin by reacting a monomer by a reverse phase suspension polymerization method,

(a) an anionic emulsifier selected from the group consisting of (i) a monomer, ii) a compound represented by the formula (1), a compound represented by the formula (2), and a mixture thereof; (iv) an aqueous monomer solution containing an initiator and iii) water; and

(b) solvent

It provides a method for producing a water absorbent resin comprising the step of reacting.

[Formula 1]

[Formula 2]

(In Formula 1 and Formula 2, R ₁ is a hydrophobic alkyl or alkyl aryl group and has 6 to 22 carbon atoms, M is hydrogen (H), sodium (Na), potassium (K), and lithium (Li). Is selected from the group consisting of R ₂ is ethylene or propylene and n is an integer from 2 to 50.

Hereinafter, the present invention will be described in detail.

The present invention continuously adds an aqueous monomer solution comprising a phosphorus anionic emulsifier, an initiator and water selected from a monomer, a compound represented by the formula (1), a compound represented by the formula (2), and a mixture thereof to a solvent to form amorphous particles. To prepare absorbent resin.

In the present invention, the monomer may be an ionic water-soluble monomer, a nonionic monomer and an unsaturated monomer having an amino group. Examples of the ionic water-soluble monomers include (meth) acrylic acid, alkali salts of (meth) acrylic acid, ammonium salts of (meth) acrylic acid, and 2- (meth) acrylamide-2-methyl sulfonate (2 It is preferable that it is at least 1 sort (s) chosen from the group which consists of alkali metal salts of-(meth) acrylamide-2-methyl sulfonate) and 2- (meth) acrylamide-2-methyl sulfonate. In addition, the nonionic monomers (meth) acrylamide ((meth) acrylamide), N, N-dimethylacrylamide (N, N-dimethylacrylamide), 2-hydroxyethyl (meth) acrylate (2-hydroxyethyl (meth (acrylate) and N-metholol (meth) acrylamide (N-methylol (meth) acrylamide) is preferably at least one member selected from the group consisting of. In addition, the unsaturated monomer having an amino group is selected from the group consisting of diethylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylate and their quaternary salts. It is preferable that it is 1 or more types. In addition, the ionic water-soluble monomer, the nonionic monomer and the unsaturated monomer having an amino group may be used alone or a mixture of two or more thereof may be used. In the above, (meth) acryl means methacryl or acryl. In addition, the monomer concentration in the aqueous monomer solution is preferably 20% by weight or more, and the degree of neutralization is preferably 30 mol% or more.

In the present invention, an anionic emulsifier of phosphorus selected from the group consisting of a compound represented by the formula (1), a compound represented by the formula (2), and a mixture thereof is used.

[Formula 1]

[Formula 2]

In Formula 1 and Formula 2, R ₁ is a hydrophobic alkyl or alkylallyl group, and an appropriate size has 6 to 22 carbon atoms. In addition, n is preferably 2 to 50, more preferably 3 to 10 as the number (molar number) of the hydrophilic ethylene oxide and propylene oxide alone or a mixture thereof. M may be one of hydrogen (H), sodium (Na), potassium (K), lithium (Li), or a mixture thereof. It is preferable that the amount of the anionic emulsifier of the phosphorus based on 0.01 to 10 parts by weight per 100 parts by weight of the monomer is used in order to obtain amorphous particles and excellent absorbent particles. More preferably 0.1-5 parts by weight is appropriate.

In addition, the initiator used in the present invention is hydrogen peroxide, tert-butyl hydroperoxide, tungsten persulfate (potassium persulfate), sodium persulfate (sodium persulfate), ammonium persulfate (ammonium persulfate), 2-2'-azobis- (2-aminodipropane) dihydrochloride, 2,2'-azobis- as an azo compound N, N'-dimethyleneisobutylamidine dihydrochloride (2,2'-azobis- (N, N'-dimethyleneisobutylamidine) dihydrochloride) and 2,2'-azobis {2-methyl-N- [1 , 1-bis (hydroxymethyl) -2-hydroxy-ethyl] propionamide} (2,2'-azobis {2-methyl-N- [1,1-bis (hydroxymethyl) -2-hydroxy-ethyl] propionamide}) is preferably one or more selected from the group consisting of. In addition, hydrogen peroxide, tertiary butyl hydroperoxide and persulfate-based can be used as a redox-based display agent with reducing agents such as persulfide-based, L- ascorbic acid or amine. The amount of the initiator is preferably used 0.001 to 5 parts by weight per 100 parts by weight of the monomer. More preferably 0.1 to 1 part by weight is appropriate.

In addition, solvents usable in the present invention include n-pentane, n-hexane, n-heptane, n-heptane, ligroin, cyclopentane, methylcyclopentane (methylcyclopentane), cyclohexane (cyclohexane), methylcyclohexane (methylcyclohexane), benzene (benzene), toluene (toluene), xylene (xylene) and mixtures thereof.

In addition, in the method for preparing the water absorbent resin of the present invention, in addition to the anionic emulsifier of the phosphorus, the non-ionic compound may be used in the monomer aqueous solution. Representative nonionic emulsifiers usable in the present invention include sorbitan fatty acid esters of sorbitan, polyoxysorbitan fatty acid esters, and sucrose fatty acid esters of sucrose. , Polyglycerin fatty acid ester of polyglycerin, polyoxyethylene alkylphenyl ether, ethyl cellulose, ethyl hydroxycellulose, polyethylene oxide, anhydrous polyethylene Mali Anhydrous polyethylene maleate, anhydrous polybutadiene maleate, anhydrous ethylene maleate-propylene-diene terpolymer, a copolymer of alphaolefin and maleic anhydride, or Derivatives thereof, polyoxyethylene-polyoxypropylene It is preferably selected from the group consisting of rock copolymers (polyoxyethylene-polyoxypropylene block polymer) and mixtures thereof. The amount of the nonionic emulsifier is preferably 0.01 to 10 parts by weight per 100 parts by weight of the monomers used in the present invention in order to obtain amorphous and excellent safety particles. More preferably 0.1 to 5 parts by weight is appropriate.

In the present invention, a crosslinking agent may be used. The crosslinking agent may be mixed in the aqueous monomer solution or added after the completion of the polymerization reaction. The crosslinking agent is a compound having at least two or more polymerizable unsaturated groups or a diglycidyl ether compound having two or more reactive functional groups capable of reacting with a monomer, a halo epoxy compound, Isocyanate compounds and the like can be used. Representative examples of the crosslinking agent having at least two polymerizable unsaturated groups include ethylene glycol diacrylate, ethylene glycol dimethacrylate, and diethylene glycol diacryl. Diethylene glycol diacrylate, diethylene glycol dimethacrylate, propylene glycol diacrylate, propylene glycol dimethacrylate, and polystyrene glycol dimethacryl Polyethylene glycol dimethacrylate, polyethylene glycol diacrylate, diallyl phthalate, triaryl isocyanate (N, N ', N' '-triallyl isocyanate), methylene bisacrylamide ( N, N'-methylene bisacrylamide). In addition, the diglycidyl ether compounds include (poly) ethylene glycol diglycidyl ether ((poly) ethylene glycol diglycidyl ether), (poly) propylene glycol glycidyl ether ((poly) propylene glycol glycidyl ether), (poly ) Glycerin glycidyl ether (poly) glycerin glycidyl ether and the like, examples of the halo epoxy compound epichlorohydrin (epichlorohydrin), epibromohydrin (epibromohydrin), alphamethyl epicrohydrin (α- methylepichlorohydrin) and the like, and examples of the isocyanate compound include 2,4-tolylene diisocyanate and hexamethylene diisocyanate. Compounds having two or more polymerizable unsaturated groups, diglycidyl ether compounds, halo epoxy compounds or isocyanate compounds may be used alone or in mixture of two or more thereof. The amount of the crosslinking agent used in the present invention is preferably used within the range of 10 parts by weight per 100 parts by weight of the monomer used in the present invention, more preferably 0.001 to 5 parts by weight is appropriate.

In addition, in the present invention, the monomer aqueous solution may further include a molecular weight regulator for controlling the appropriate molecular weight. The molecular weight modifiers include mercaptan-based and sodium hypophosphite, but mercaptan-based is not preferable because of the possibility of causing odor, sodium hypophosphite having a small amount and excellent in effect is more suitable. The amount of the chain transfer agent used in the present invention is appropriately 0.0001 to 0.1 parts by weight per 100 parts by weight of the monomer.

Hereinafter, examples of the present invention will be described. However, the following examples are intended to illustrate the invention and the present invention is not limited by the following examples.

Example 1

A suitable amount of cyclohexane is added to a 1.0 L reactor with a heating jacket and two baffles, circulated for 40 minutes with water while replacing air with nitrogen, set at 70 ° C, and monomer, anionic and nonionic systems exist simultaneously. Aqueous monomer solution including emulsifier, initiator, molecular weight regulator and water was added for at least 25 minutes using a pump. For mixing, a paddle type stirrer with an angle of 45 ° was used and the stirring speed was 400 rpm per minute. After the addition of the aqueous monomer solution was aged for 20 minutes, the temperature of the jacket was raised to achieve azeotropy. The water absorbent resin prepared through the reaction was dehydrated for 4 hours to adjust the water content of the water absorbent resin to 25%. After the dehydration, the temperature of the reactor was cooled to 70 ° C., and then 4 g of 10% by weight of EX-851 * aqueous solution was added for 15 minutes to complete the crosslinking reaction for 2 hours, and then the solvent was separated. It dried and obtained white powder.

[Examples 2-6]

Examples 2 to 6 were carried out in the same manner as in Example 1, except that the concentration of the anionic emulsifier was changed from Table 1 below.

TABLE 1

Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Cyclohexane (g) 330 330 330 330 330 330 Monomer (g) 208.33 208.33 208.33 208.33 208.33 208.33 Water (g) 20 20 20 20 20 20 RE-610 1) (g) 0.25 0.5 One 1.5 2 5 RS-610 2) (g) 0.05 0.05 0.05 0.05 0.05 0.05 KPS 3) (g) 0.5 0.5 0.5 0.5 0.5 0.5 NHP 4) (g) 0.01 0.01 0.01 0.01 0.01 0.01 Neutrality (mol%) 70 70 70 70 70 70

In Table 1, RE-610 is an emulsifier having an anionic and nonionic system having 9 moles of ethylene oxide (Ethylene Oxide) as a cyclic phosphate ester under Rh ne-Poulenc's trade name.

RS-610 is a linear alkyl phosphate ester under the trade name of Rh ne-Poulenc, which is an emulsifier in which both anionic and nonionic systems having 6 moles of ethylene oxide are present.

Potassisium persulfate (KPS) is a water soluble initiator,

Sodium hypophosphite monohydrate (NHP) is a molecular weight regulator,

EX-851 is a trade name of Nagase Chemical Co., Ltd., a polyethylene glycol diglycidyl ether.

[Experiment 1] Measurement of Physical Properties of Absorbent Resin

In order to determine the physical properties of the absorbent polymer prepared according to the above example, the absorbed amount of absorbent resin, absorbed rate 1, absorbed rate 2 and urine amount were measured. The measuring method of physical property is as follows.

Absorption amount

1 g of the water absorbent resin was dispersed in 0.9% by weight of an aqueous sodium chloride solution, swollen for 40 minutes, filtered through a 200 mesh metal network, and calculated by the following Formula 1.

[Calculation 1]

Absorption amount = (Swelled absorbent resin weight (g)-sample weight (g)) / sample weight (g)

Absorption rate 1

Sprinkle 0.3 g of water-absorbent resin thinly on a paper filter (No. 2, 3.3 cm in diameter) placed on a sintered glass filter and measure the amount of physiological saline absorbed for 1 minute and 5 minutes, respectively. Absorption rate was measured by measuring the positional reduction of graduated burettes (length: 33cm) connected to the same height.

Absorption rate 2

The method used the same method as the absorption rate 1 but measured the absorption rate in the presence of a load by placing a 150 g weight made of stainless steel on the sample. Absorption rate measurement in the presence of a load can simultaneously measure the absorption rate when the actual earrings are worn and the gel blocking due to the relatively uncrosslinked absorbent resin.

Urinary capacity

The method is put 1 g of the absorbent resin in a nonwoven fabric and swelled in physiological saline for 1 hour and then taken out, left for 30 seconds and dehydrated for 5 minutes in a centrifuge fixed at 1000 rpm to calculate the weight of the final swollen absorbent resin The amount of urination was measured.

The results of the measurements are shown in Table 2 below.

TABLE 2

Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Absorption rate (ml / 1 min) 5 6 8 10 12 11 Absorption rate (ml / 5 minutes) 12 12 12 16 15 16 Absorption rate under load (ml / min) 4.5 4.8 4.6 4.3 4.4 4.5 Absorption rate under load (ml / 5 min) 10 12 10 12 12 12 Absorption amount (g / g) 68 70 72 66 62 62 Amount of urine (g / g) 33 32 34 33 33 31

Experiment 2 Measurement of Average Particle Size and Particle Distribution

50 g of water absorbent resin was placed at the top of a particle size classifier consisting of 20, 40, 60, 80, and 100 mesh diameters of 20 cm, shaken for 5 minutes, and the particle size and distribution were measured. . The apparent density was measured using only particles of 20 mesh or less and 100 mesh or more. The results of the measurements are shown in Table 3 below.

TABLE 3

Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Particle Distribution (㎛) More than 850 5 5 3 2 0 0 425-850 95 92 95 40 50 30 250-425 0 3 2 53 42 50 180-250 0 0 0 4 5 16 150-180 0 0 0 One 3 3 150 or less 0 0 0 0 0 One Apparent density (g / cc) 0.76 0.74 0.75 0.68 0.70 0.63 Particle shape Amorphous Amorphous Amorphous Amorphous Amorphous Amorphous

As shown in Table 3, except for Example 6, it can be seen that small particles of 150 μm or less do not exist. The above results demonstrate that the particle size of the water absorbent resin prepared according to the present invention is intensively distributed between 150 and 850 μm, so that the efficiency is excellent. In addition, it was found that the particle form was sufficiently fused in an amorphous form and excellent in strength.

As described above, in the method of preparing the absorbent polymer according to the present invention, the monomer is polymerized using a reverse phase suspension polymerization method, and the particle size and its distribution can be controlled by continuously adding the aqueous monomer solution without lowering the temperature. In addition, it was possible to mass-produce a water absorbent resin having an amorphous amorphous form in a short time.

Claims (10)

In the method for producing a water absorbent resin by reacting a monomer by a reverse phase suspension method, (a) an anionic emulsifier selected from (i) a monomer, ii) a compound represented by the formula (1), a compound represented by the formula (2), and mixtures thereof, iii) an aqueous monomer solution containing an initiator and iii) water; and (b) reacting the solvent to produce a water absorbent resin, the method comprising: [Formula 1] [Formula 2] In Formula 1 and Formula 2, R ₁ is a hydrophobic alkyl or alkyl aryl group and has 6 to 22 carbon atoms, M is hydrogen (H), sodium (Na), potassium (K), and lithium (Li). It is selected from the group consisting of R <_2> is ethylene or propylene and n is an integer of 2-50. The method of claim 1, wherein the aqueous monomer solution further comprises a nonionic emulsifier. The monomer of claim 1 or 2, wherein the monomer is (meth) acrylic acid, an alkali salt of (meth) acrylic acid, an ammonium salt of (meth) acrylic acid, or 2- (meth) acrylamide-2-. At least one ionic water-soluble monomer selected from the group consisting of alkali metal salts of methyl sulfonate (2- (meth) acrylamide-2-methyl sulfonate) and 2- (meth) acrylamide-2-methyl sulfonate; (Meth) acrylamide, N, N-dimethylacrylamide, 2-hydroxyethyl (meth) acrylate and N-meth At least one nonionic monomer selected from the group consisting of tyrol (meth) acrylamide (N-methylol (meth) acrylamide); And Unsaturated having at least one amino group selected from the group consisting of diethylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylate and their quaternary salts Monomers; It is 1 type compound chosen from the group which consists of these, or 2 or more types of mixtures The manufacturing method of the water absorbing resin characterized by the above-mentioned. The method of claim 1 or 2, wherein the concentration of the monomer in the aqueous monomer solution is 20% by weight or more, and the degree of neutralization is 30 mol% or more. The method of claim 1 or 2, wherein the amount of the anionic emulsifier is 0.01 to 10 parts by weight per 100 parts by weight of the monomer. The method according to claim 1 or 2, wherein the initiator is hydrogen peroxide, tert-butyl hydroperoxide, potassium persulfate as persulfate, sodium persulfate ), Ammonium persulfate, 2-2'-azobis (2-aminodipropane) dihydrochloride (2,2'-azobis- (2-aminodipropane) dihydrochloride) as azo compound, 2,2 '-Azobis-N, N'-dimethyleneisobutylamidine dihydrochloride (2,2'-azobis- (N, N'-dimethyleneisobutylamidine) dihydrochloride) and 2,2'-azobis {2-methyl -N- [1,1-bis (hydroxymethyl) -2-hydroxy-ethyl] propionamide} (2,2'-azobis {2-methyl-N- [1,1-bis (hydroxymethyl) -2 -hydroxy-ethyl] propionamide}), or a compound selected from the group consisting of two or more thereof, and the amount of initiator used is within 0.001 per 100 parts by weight of monomer. 5 method for producing a water absorbent resin which is characterized by using parts by weight. The method of claim 1 or 2, wherein the solvent is n-pentane (n-pentane), n-hexane (n-hexane), n-heptane (n-heptane), ligroin (cyclogrone), cyclopentane (cyclopentane) , Methylcyclopentane, cyclohexane, methylcyclohexane, benzene, toluene, xylene, and mixtures thereof. Method for producing a water absorbent resin. According to claim 1 or 2, wherein the aqueous monomer solution further comprises a crosslinking agent or after the completion of the reaction of the monomer aqueous solution and the solvent is added to the crosslinking agent, the crosslinking agent is at least two polymerizable unsaturated groups (polymerizable unsaturated groups) It is selected from the group consisting of a diglycidyl ether compound, a halo epoxy compound and an isocyanate compound having two or more reactive functional groups capable of reacting with a compound having a monomer or a monomer, wherein the amount of the crosslinking agent is A method for producing an absorbent polymer, characterized in that used within the range of 10 parts by weight per 100 parts by weight. The method of claim 1 or 2, wherein the aqueous monomer solution further comprises sodium hypophosphite, and the amount of sodium hypophosphite used is 0.0001 to 0.1 parts by weight per 100 parts by weight of the monomer. . The nonionic emulsifier is sorbitan fatty acid ester of sorbitan, polyoxysorbitan fatty acid ester of polyoxysorbitan, sucrose fatty acid ester. ), Polyglycerin fatty acid ester, polyoxyethylene alkylphenyl ether, ethyl cellulose, ethyl hydroxycellulose, polyethylene oxide, anhydrous Anhydrous polyethylene maleate, anhydrous polybutadiene maleate, anhydrous ethylene maleate-propylene-diene terpolymer, an alpha olefin and maleic anhydride Block copolymers of copolymers or derivatives thereof, polyoxyethylene-polyoxypropylene Sieve (polyoxyethylene-polyoxypropylene block polymer) and are selected from the group consisting of and mixtures thereof, the amount of the non-ionic emulsifying agent A method of manufacturing a water-absorbent resin, characterized in that the monomer per 100 parts by weight of 0.01 to 10 parts by weight.