JPH01113406A - Manufacture of highly water-absorptive polymer - Google Patents

Abstract

PURPOSE:To produce the title polymer which is highly water-absorptive, whose water-containing gel has a high strength, and which is excellent in water absorbing rate and suitable, for example, as absorbent for sanitary materials or as water-retaining agent for agriculture and horticulture, by mixing specific hydrophilic polymer particles with a specific crosslinking agent, and bringing them into contact with water vapor to crosslink the polymer. CONSTITUTION:Carboxyl- or carboxylate-containing hydrophilic polymer particles [e.g., particles of a polymer obtained by polymerizing (meth)acrylic acid, etc.] is mixed with a crosslinking agent containing two or more functional groups (e.g., ethylene glycol diglycidyl ether), and they are brought into contact with water vapor to crosslink the polymer. A highly water-absorptive polymer is obtained which is highly water-absorptive, whose water-containing gel has a high strength, and which is excellent in water absorbing rate, and can absorb a large amount of water under load. It can be suitably used, for example, as absorbent for sanitary materials, water-retaining agent for agriculture and horticulture, or water-stopping agent in public works or architecture.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a body fluid absorbent for sanitary napkins, disposable diapers, etc.
Absorbent polymers that have a wide range of uses such as soil water retention agents, seed coating agents, water stoppers, and dew prevention agents.In particular, they are highly absorbent polymers that have a high absorbent gel strength (and a high water absorption rate). The present invention relates to a method for producing a synthetic polymer.

[Conventional technology]

Water-absorbing materials such as water-absorbing polymers made of hydrophilic polymers having carboxyl groups and carboxylate groups have been proposed as an alternative to paper, pulp, etc., which have been conventionally used as water-absorbing materials in the fields of sanitary materials and agriculture and horticulture. It's here. In addition, various improvements have been made to further improve the water absorption performance of these polymers. For example, in order to improve the wettability of water-absorbing polymers, when producing water-absorbing resins by polymerizing vinyl monomers by reverse-phase suspension polymerization or emulsion polymerization, water-soluble polymers (JP 57-167307) or A method of adding a surfactant (JP-A No. 58-32641) has been used. However, the performance of the polymer obtained by these methods as a water absorbing agent is still insufficient.

Furthermore, in order to improve the water absorption rate, there is a method of cross-linking a water-absorbing resin in a mixed solvent of water and a hydrophilic organic solvent (Japanese Patent Laid-Open No. 57-44627), and a method of inactivating a water-absorbing resin in the presence of water. Method of crosslinking in an organic solvent (JP-A-58-1172
No. 22) has been proposed, but there is a problem that the improvement in water absorption performance is insufficient. JP-A-59-62665 discloses a method for producing a super absorbent polymer with excellent water absorption rate by adjusting the water content of a hydrophilic polymer to 10 to 40% by weight and then crosslinking with a crosslinking agent. However, in this method, since an aqueous solution containing a crosslinking agent is added to the polymer by spraying or the like, there is a problem that crosslinking tends to be non-uniform and it is difficult to exhibit sufficient performance. Also, JP-A-59-1
No. 89103 discloses a technique for producing a super absorbent resin by mixing a crosslinking agent with a water absorbent resin powder and subjecting it to heat treatment if necessary. However, the crosslinking reaction is still insufficient, and the water absorption capacity of the resulting resin is still insufficient.

[Problem to be solved by the invention]

Therefore, an object of the present invention is to provide a method for producing a water-absorbing polymer that has higher water absorption than conventional water-absorbing polymers and has superior water-absorbing gel strength.

[Means to solve the problem]

In crosslinking the surface of hydrophilic polymer particles having a carboxyl group and/or carboxylate group in the molecule, the present invention provides that when the surface of the polymer is crosslinked using a crosslinking agent in the presence of water vapor on the polymer surface. This was done based on the knowledge that surface crosslinking can be carried out extremely efficiently and that the above problems can be effectively solved.

That is, the present invention is characterized in that hydrophilic polymer particles having a carboxyl group or carboxylate group are mixed with a crosslinking agent having two or more functional groups, and the polymer is crosslinked by contacting with water vapor. A method for producing a superabsorbent polymer is provided.

The hydrophilic polymer to be used in the present invention may be any type of polymer and any polymerization method as long as it has a carboxyl group and/or a carboxylate group in its constituent units. For example, polymers obtained by polymerizing one or more of unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, fumaric acid, and itaconic acid or water-soluble salts thereof, and water-soluble polymers that can be copolymerized with the above monomers. (
A polymer obtained by copolymerizing meth)acrylamide, a dimethyl or diethylaminoethyl ester tertiary salt, or a quaternary salt of (meth)acrylic acid, and further having an alkyl group having 1 to 24 carbon atoms to an extent that does not reduce the effects of the present invention. Hydrophilic products made by copolymerizing unsaturated carboxylic acid esters such as acrylic acid and methacrylic acid, alkyl vinyl ethers having an alkyl group having 1 to 24 carbon atoms, α-olefins having 1 to 24 carbon atoms, and hydrophobic monomers such as styrene. Examples include saponified starch-acrylic acid graft copolymers and their salts, saponified starch-acrylonyl-IJ graft copolymers, carboxymethyl cellulose, saponified vinyl acetate-acrylic acid ester copolymers and their salts, etc. . In addition, when producing these polymers and/or after polymerization, crosslinking is performed by adding a small amount of crosslinking agent within a range that does not reduce the effect of the present invention, or those in which two or more types of initiators are used in combination, Self-crosslinked materials are also included. The above-mentioned salts include alkali metal salts, alkaline earth metal salts, ammonium salts, and the like. Further, a part of the carboxyl groups in the molecule may be carboxylate groups.

These hydrophilic polymers are synthesized by known polymerization methods such as solution polymerization and reversed-phase suspension polymerization. Polymers obtained by polymerization methods are preferred. Particularly preferred is a porous polymer obtained by polymerizing an O/W10 type emulsion in which a phase containing the monomer is arranged as an intermediate phase.

Specifically, first, a water-soluble surfactant or a water-soluble polymeric dispersant, such as partially saponified polyvinyl alcohol, is used, and the inner phase is a hydrophobic phase such as cyclohexane, and the outer phase is a carboxyl compound such as a neutralized acrylic acid. After preparing an O/W emulsion, which is an aqueous phase containing a monomer having a carboxylate group and a polymerization initiator such as ammonium persulfate, this emulsion is mixed with ethyl cellulose or the polyethylene glycol disclosed in Japanese Patent Application No. 62-25739. An acrylic copolymer having a chain, that is, a copolymer of a vinyl monomer A having a polyethylene glycol chain and/or a polypropylene glycol chain in the molecule and a monomer B copolymerizable with the monomer, and having an average molecular weight of 1,000. In addition to an oil-soluble polymer dispersant such as a copolymer in the range of ~1.000.000, or a hydrophobic dispersion medium such as cyclohexane containing an oil-soluble surfactant, ○/W
It is a porous polymer with many pores in the particles obtained by creating an emulsion and polymerizing monomers.
Since this polymer has a very large surface area, it can exhibit the effects of the present invention the most.

The water content of the hydrophilic polymer particles during crosslinking according to the present invention may be any amount, but is preferably 0.1% to 6%.
0% by weight (hereinafter abbreviated as %), more preferably 0
．． It is 5% to 40%, more preferably 1% to 10%. When the water content is within the above range, a water-absorbing resin with high water absorption and excellent water-absorbing gel strength can be obtained. However, if the water content is too much outside the above range, drying will take much effort and will be impractical.

In the present invention, any particle size can be used as the hydrophilic polymer particles, but from the viewpoint of uniform mixability with the crosslinking agent and the performance of the resulting polymer,
Preferably, one having a diameter of 10 to 300 μm is used.

The crosslinking agent used in the present invention may be any crosslinking agent as long as it reacts with the carboxyl group or carboxylate group in the hydrophilic polymer. For example, polyglycidyl ethers such as ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, sorbitol polyglycidyl ether, epichlorohydrin,
Haloepoxy compounds such as α-methylchlorohydrin, polyamines such as ethylenediamine, chitosan, polyethyleneimine, polyaldehydes such as glyoxanopeglutaraldehyde, polyvalent metal salts such as aluminum salts, hexamethylene diisocyanate, toluene diisocyanate, etc. Examples include polyvalent incyanates. Furthermore, in addition to the above compounds, crosslinking agents having an amino group and two or more epoxy groups in the molecule as described in Japanese Patent Application No. 62-30412, such as the reaction product of polyglycidyl ether and diethalamine, and the Polyvalent epoxy compounds described in No. 199010/1982, for example, those made into epoxy compounds by reacting imidazoles with epichlorohydrin and then treating with alkali, γ-glycidoxypropyltrimethoxysilane, vinyltrimethoxysilane, etc. Examples include silane coupling agents.

Although the amount of the crosslinking agent used in the present invention is arbitrary, it is usually 0.001 to 10%, preferably 0.005 to 5%, based on the hydrophilic polymer particles. That is, if the amount of the crosslinking agent added is less than 0.001%, sufficient effects will not be exhibited, whereas if it is more than 10%, the amount of water absorption tends to decrease, which is undesirable.

In the present invention, the crosslinking agent may be added to the hydrophilic polymer by any method. For example, a crosslinking agent may be added to a hydrophilic polymer, dissolved or dispersed in a solvent that dissolves the crosslinking agent, or the crosslinking agent may be added to a hydrophilic polymer and then an organic solvent is added. It's good too,
The crosslinking agent may be added after adding the organic solvent to the hydrophilic polymer. If necessary, in an organic solvent, ethyl cellulose or an acrylic copolymer having a polyethylene glycol chain as shown in Japanese Patent Application No. 62''-25739, that is, a vinyl monomer A having a polyethylene glycol chain in the molecule, and the monomer A copolymer of copolymerizable monomer B with an average molecular weight of 1.000 to 1.00
0. (An oil-soluble polymer dispersant such as a copolymer and/or an oil-soluble surfactant in the range of 100% may be added.

The solvent includes n-pentane, cyclopenkune, n-
- Aliphatic hydrocarbons such as hexane, cyclohexane, n-hebutane, methylcyclohexane, kerosene, aromatic hydrocarbons such as benzene, toluene, xylene, aliphatic ketones such as methyl ethyl ketone, aliphatic esters such as ethyl acetate, etc. These can be used singly or as a mixture of two or more. The amount of these solvents is 0.1 to 1 part of the hydrophilic polymer.
It is recommended to use 5 parts, preferably 0.1 to 2 parts. Note that the mixing time is preferably within 12 hours. This is because if it exceeds this, there will be no economic advantage. Note that it is preferable to remove these organic solvents by distillation or the like before contacting with water vapor.

According to the present invention, it is essential to mix a crosslinking agent having two or more functional groups with the hydrophilic polymer particles, and to contact them with water vapor before, after, or at the same time. Then, if necessary, heat is applied at the same time or afterwards to effect crosslinking. That is, by using water vapor, it is possible to prevent non-uniform crosslinking that tends to occur when water is directly sprayed, and to perform surface crosslinking more effectively.

In the present invention, various methods can be used for crosslinking by contacting with water vapor. For example, after or simultaneously with adding the crosslinking agent to the hydrophilic polymer particles, while stirring the hydrophilic polymer particles using a conventional mixer or stirrer,
Here, water vapor led from a steam generator is supplied to the polymer through a nozzle, and crosslinking is carried out by heating with the steam or heating from the outside. , a method of heating using a rotary dryer, a groove type stirring dryer, etc. Although heating is not essential for carrying out the crosslinking reaction, it is preferable to heat it so that the crosslinking reaction is carried out at 20 to 200°C.

The amount of water vapor supplied to the hydrophilic polymer particles may be any amount, but the weight increase due to supply is up to about 0.7 parts by weight, preferably 0.02 to 0.4 parts by weight per 1 part by weight of dry hydrophilic polymer particles. , more preferably 0.02
It is preferable to set the amount to 0.1 parts by weight from the viewpoint of drying efficiency leading to commercialization.

After the crosslinking treatment according to the present invention, the polymer particles can be further subjected to drying, pulverization, or granulation treatment, if necessary, before use.

〔Effect of the invention〕

According to the present invention, it is possible to produce a superabsorbent polymer that is highly water absorbent, has a high gel strength after absorbing water, and has an excellent water absorption rate. Furthermore, a superabsorbent polymer with excellent water absorption under load can be produced.

Therefore, it can be suitably used as a water-absorbing agent for sanitary materials such as disposable diapers and sanitary napkins that need to quickly absorb large amounts of urine and blood, as well as water-retaining agents for agriculture and horticulture, water-stopping agents for civil engineering and construction, and the like.

Next, the present invention will be explained with reference to Examples, but the present invention is not limited thereto.

〔Example〕

In Examples, the water absorption amount, water absorption rate, and strength of the water-absorbing gel were measured as follows.

Water Absorption Amount 0.3 g of water-absorbent resin was sealed in a non-woven fabric bag, and the bag was held horizontally so that the sample was evenly sprinkled on it. Next, the sample was immersed horizontally in a petri dish containing 300 g of physiological saline for 30 minutes, then pulled out and drained on a wire mesh for 1 minute, and its weight was measured. On the other hand, the weight obtained by testing a non-woven bag that does not contain water absorbent resin in the same manner is used as a blank, and the value obtained by subtracting the blank from the above measurement value and converting it to the weight per 1 g of water absorbent resin. was taken as the water absorption amount. The larger the number, the higher the water absorption.

0.3 g of polymer was placed in a paper tea bag type bag with an initial water absorption rate of 6 x 8 cm, the bag was stood upright, and the bottom was lightly filled with polymer. The bag was immersed in physiological saline in a 300 d beaker for 1 minute in an upright position. The condensate was immersed for 1 minute and the weight was measured. The amount of water absorbed by the tare was subtracted from this value and converted into the amount of water absorbed per 1 g of polymer. The larger this value is, the faster the water absorption rate is.

Measurement of Gel Strength 2 g of water absorbent resin was placed in a 100 ml beaker, and 2 g of methanol was added to sufficiently wet the water absorbent resin. 40 g of ion-exchanged water was added to the mixture at once, and the mixture was shaken to avoid clumping, and the mixture was uniformly absorbed to prepare a sample. Next, using a rheometer (manufactured by Fudo Kogyo, NRM-2002J), this sample was raised at a speed of 2 cm/min,
The stress 10 seconds after the adapter (Φ10 mm, on a disc) came into contact with the gel surface was measured, and this was taken as the gel strength. The larger this value is, the stronger the water-absorbing gel is.

Water absorption amount under load 0.1 g of water absorbent resin (particle size 0.2 mm or more) was placed in a cell (
Sprinkle it evenly on the bottom of a φ20mm cylinder, mesh 0.2111[0], and add a 62.8g weight (20g/cnO) to it.
was used as a sample. Next, this sample was measured using a water absorption measuring device (
(KM350, manufactured by Kyowa Seiko) was placed on a perforated plate filled with artificial urine, and the amount of water absorbed 60 minutes later was measured. This value was converted into the amount of water absorbed per 1 g of polymer. The larger this value is, the better the amount of water absorption under load is.

Example 1 II! equipped with a stirrer, reflux condenser, dropping funnel and nitrogen gas inlet tube! Add 3 cyclohexane to a four-bottle flask.
00 g and 3 g of ethyl cellulose (manufactured by Harkiniles, trade name N-50) were added, stirred, nitrogen gas was blown in to drive out dissolved oxygen, and the temperature was raised to 70°C. In another flask, 43 g of sodium hydroxide was dissolved in 130 g of water, and 100 g of acrylic acid (AA) was added to the resulting aqueous solution, and 0.16 g of ammonium persulfate (APS) was added to the solution.
1.2 g of partially saponified polyvinyl alcohol (manufactured by Nippon Gosei Co., Ltd., trade name CH-17) and 0.061 g of ethylene glycol diglycidyl ether (EGDG) were dissolved in 34 g of water and added, and further 80 g of cyclohexane was added and stirred. A monomer aqueous solution (○/W emulsion) was prepared by blowing nitrogen gas to drive out dissolved oxygen (monomer concentration 40% vs. aqueous phase). Next, while sufficiently stirring the dispersion medium in the four-roof flask at a speed of 4 oorpm, O
/W emulsion was added dropwise over 1 hour, and polymerization was further continued for 3 hours.

After that, the dispersion medium was removed by decantation, and the
After drying at .degree. C. for 3 hours, porous hydrophilic polymer particles (average particle size: 150 .mu.m) with a moisture content of 4% were obtained.

Next, 104.2 g of the polymer particles were transferred to a 500-meter tube equipped with a nozzle led from a steam generator, a thermometer, and an external heating device.
00-Pour into a four-bottle flask and add glycerol polyglycidyl ether (Denacol Ex-31 manufactured by Nagase Chemical Industries).
3) Added 0.1 g and stirred and mixed well. After that, stirring was continued for 3 minutes while blowing steam through the nozzle (
reaction temperature 105°C). After 3 minutes, the polymer particles were taken out from the four-loop flask and the weight was measured, and the result was 107.5.
It was g. The polymer particles were further heated at 110° C. for 3 hours in a hot air dryer to obtain spherical porous polymer particles.

Example 2 0.1 g of ethylene glycol diglycidyl ether (Denacol Ex-810 manufactured by Nagase Chemical Industries, Ltd.) was used instead of glycerol polyglycidyl ether, and water vapor was
Polymerization and mulberry bridge were carried out in the same manner as in Example 1, except that the weight was 111 g.
Spherical porous polymer particles were obtained.

Example 3 Polymerization was carried out in the same manner as in Example 1, and then, using a dehydration tube, the external temperature of the heating bath was raised to 85°C to perform azeotropic dehydration.
Water was removed until the water content of the resulting polymer was 10%. Subsequently, cyclohexane was removed to obtain porous hydrophilic polymer particles (average particle size: 150 μm). 111 g of these polymer particles were transferred to a 500 m1 unit equipped with a nozzle led from a steam generator, a thermometer, and an external heating device! Place sorbitol polyglycidyl ether (
Nagase Chemical Industries Denacol Ex-6148) 0.01
g and stirred well to mix. Next, the mixture was stirred for 15 minutes while blowing steam through a nozzle (reaction temperature: 105°C).
). Thereafter, the polymer particles were taken out from the four-hole flask, and the weight was measured to be 125 g. The polymer particles were further heated at 110° C. for 3 hours in a hot air dryer to obtain spherical porous polymer particles.

Example 4 Acrylic copolymer having polyethylene glycol instead of ethyl cellulose (methoxypolyethylene glycol methacrylate EO addition number 23 and Stair IJ)
3g of rare acrylate 1:9 (mole ratio) copolymer)
Polymerization was carried out in the same manner as in Example 1, except that the polymer was used, and then, using a dehydration tube, the external temperature of the heating bath was raised to 85 ° C., and azeotropic dehydration was carried out, so that the water content of the produced polymer was 15%. Water was removed until Subsequently, cyclohexane was removed to obtain porous hydrophilic polymer particles (average particle size: 200 μm). 118g of this polymer was introduced into a 500mj vessel equipped with a nozzle, a thermometer, and an external heating device that led from a steam generator!
Add ethylene glycol diglycidyl ether (Denacol Ex-81 manufactured by Nagase Chemical Industries, Ltd.) to a four-bottle flask.
0) 0.02 g was added and mixed well with stirring. next,
The mixture was stirred for 23 minutes while blowing steam through a nozzle (
reaction temperature 90°C). Thereafter, the polymer was taken out from the four-hole flask and its weight was measured, and it was found to be 143 g. This polymer was further heated at 110° C. for 3 hours in a hot air dryer to obtain spherical porous polymer particles.

Example 5 Into 11 four-necked flasks equipped with a stirrer, reflux condenser, dropping funnel and nitrogen gas inlet tube, 30 ml of cyclohexane was added.
0 g and 3 g of ethyl cellulose (manufactured by Vercules, trade name N-50) were added and stirred, nitrogen gas was blown in to drive out dissolved oxygen, and the temperature was raised to 70°C. In addition, in another flask, 43 g of sodium hydroxide was dissolved in 130 g of water, and 100 g of acrylic acid (AA) was added thereto. .02
4 g was dissolved in 1 g of water and added, and nitrogen gas was blown in to drive out the dissolved oxygen to prepare an aqueous seven-mer solution. Next, while stirring the dispersion medium in the four-hole flask sufficiently at a speed of 40 rpm, the monomer aqueous solution was added dropwise over a period of 1 hour, and polymerization was further carried out for 3 hours. Then, using a dehydration tube, raise the external temperature of the heating bath to 85°C to perform azeotropic dehydration.
Water was removed until the water content of the resulting polymer was 28%. Subsequently, cyclohexane was also removed to obtain a particulate hydrophilic polymer (average particle size: 150 μm). 139 g of the polymer particles were placed in a 500 square meter four-bottle flask equipped with a nozzle led from a steam generator, a thermometer, and an external heating device, and 0.01 g of ethylene glycol diglycidyl ether (Denacono Kano X-810 manufactured by Nagase Chemical Industries, Ltd.) was added.
g and stirred well to mix. Next, add 8 4-bottle flasks.
The mixture was heated in a 0°C water bath and stirred for 14 minutes while blowing steam through a nozzle. After that, the polymer particles were taken out from the four-loaf flask and the weight was measured, which was 154g.
Met. This polymer was further heated at 110°C for 3 hours in a hot air dryer to obtain particulate polymer.

Example 6 43g of sodium hydroxide and 130g of water in an Erlenmeyer flask
0.3 g of ammonium persulfate and 0.06 g of ethylene glycol diglycidyl ether were added to an aqueous solution prepared by adding 100 g of acrylic acid thereto, and nitrogen gas was blown in to drive out dissolved oxygen to prepare an aqueous monomer solution. This aqueous monomer solution was poured onto a Teflon plate, formed into a thin film, and polymerized and dried in a hot air dryer at 120° C. for 3 hours. 100 to 300 of the generated plate-like polymer
It was crushed to about μ size. The water content of this polymer was 10%. 111 g of the obtained polymer was placed in a 500 m1 four-bottle flask equipped with a nozzle led from a steam generator, a thermometer, and an external heating device, and γ-glycidoxyprobyltrimethoxysilane, a silane coupling agent, was added to .2g was added and mixed well with stirring. Next, the mixture was stirred for 13 minutes while blowing steam through a nozzle (reaction temperature: 75°C).

Thereafter, the polymer was taken out from the round flask and its weight was measured and found to be 125 g. Add one more layer of this polymer
It was heated in a hot air dryer at 10° C. for 3 hours to obtain a powdery polymer.

Comparative Example 1 Polymerization and subsequent treatments were carried out in the same manner as in Example 1, except that water vapor was not blown into the polymer.

Comparative Example 2 Polymerization and subsequent treatments were carried out in the same manner as in Example 3, except that water vapor was not blown into the polymer.

Comparative Example 3 Polymerization and subsequent treatments were performed in the same manner as in Example 5, except that water vapor was not blown into the polymer.

Table 1 summarizes the performance of each polymer.

Table 1 As is clear from Table 1, it can be seen that according to the present invention, a polymer exhibiting good performance in terms of water absorption amount, water absorption rate, and water absorption gel strength can be obtained.

Example 7 II equipped with a stirrer, reflux condenser, dropping funnel and nitrogen gas inlet tube! To the four-round flask, to the cyclo-1-4
300 g of 11-ton and 1.5 g of ethyl cellulose (manufactured by Harkiniles, trade name N-50) were added and stirred, nitrogen gas was blown in to drive out dissolved oxygen, and the temperature was raised to 70°C. In another flask, 43 g of sodium hydroxide was dissolved in 189 g of water, and 100 g of acrylic acid was added to the resulting aqueous solution. 158 mg of ammonium persulfate was added and stirred, and nitrogen gas was blown in to drive out the dissolved oxygen. A monomer aqueous solution was prepared. Next, while thoroughly stirring the dispersion medium in the four-bottle flask at a speed of 40 rpm, the monomer aqueous solution was added dropwise over 1 hour, and the mixture was aged for 1 hour.
After adding 23 mg and aging for 2 hours, the solvent was distilled off and dried at 110° C. under reduced pressure to obtain spherical polymer particles with a water content of 2%.

Next, 120 g of this polymer was transferred to a 500-meter tube equipped with a nozzle led from a steam generator, a thermometer, and an external heating device.
mji! Put 12 cyclohexane into a four-loaf flask.
0g and ethylene glycol diglycidyl ether 123
mg was added and mixed by stirring at a speed of 2 rpm for 1 hour.

Then, after distilling off the cyclohexane, steam was blown through a nozzle to make the total water content of the polymer 5% (polymer weight 123.8 g), and then heated in a hot air dryer at 110°C for 3 hours to form a spherical polymer. Particles were obtained.

Example 8 An experiment was carried out in the same manner as in Example 7, except that the weight increase of the polymer due to water vapor blown from the nozzle was changed from 3.8 g to 6.5 g, and the total water content of the polymer was changed to 7%. This was done to obtain spherical polymer particles.

Example 9 The same method as in Example 7 was used except that the weight increase of the polymer due to water vapor blown from the nozzle was changed from 3.8 g to 10.7 g, and the total water content of the polymer was 10%. An experiment was conducted and spherical polymer particles were obtained.

Example 10 In Example 7, a polymer with a water content of 5% was used instead of a polymer with a water content of 2%, and the weight increase of the polymer due to water vapor blown from the nozzle was increased from 3.8 g to 6.7 g.
An experiment was conducted in the same manner as in Example 7, except that the total water content of the polymer was changed to 10%, and spherical polymer particles were obtained.

Example 11 In Example 7, a polymer with a water content of 7% was used instead of a polymer with a water content of 2%, and the weight increase of the polymer due to water vapor blown from the nozzle was increased from 3.8 g to 4.0 g.
An experiment was conducted in the same manner as in Example 7, except that the total water content of the polymer was changed to 10%, and spherical polymer particles were obtained.

Example 12 An experiment was carried out in the same manner as in Example 9, except that 120 g of cyclohexane was changed to 60 g, and spherical polymer particles were obtained.

Example 13 An experiment was conducted in the same manner as in Example 9, except that 120 g of cyclohexane was changed to 24 g, and spherical polymer particles were obtained.

Example 14 An experiment was carried out in the same manner as in Example 7 except that 123 mg of ethylene glycol diglycidyl ether was replaced with 123 mg of T-glycidoxypropyltrimethylsilane to obtain spherical polymer particles.

Example 15 Into 11 four-necked flasks equipped with a stirrer, reflux condenser, dropping funnel and nitrogen gas inlet tube, 30 g of cyclohexane was added.
0g and ethyl cellulose 2.0g (Percules Ken,
(trade name N-50) was added, stirred, nitrogen gas was blown into the mixture to drive out dissolved oxygen, and the temperature was raised to 70°C. In addition, in another flask, 43 g of sodium hydroxide was dissolved in 130 g of water, and 100 g of acrylic acid was added to the aqueous solution. 17)1
．． 2 g was dissolved in 34 g of water and added, and 135 g of cyclohexane was added, stirred, and nitrogen gas was blown to drive out dissolved oxygen to prepare an aqueous monomer solution (○/W emulsion). Next, the monomer aqueous solution (0/W emulsion) was added dropwise over 1 hour while thoroughly stirring the dispersion medium in the four-loaf flask at a speed of 40 Orpm.
After aging for 1 hour, 123 mg of ethylene glycol diglycidyl ether was added, and after aging for 2 hours, the solvent was distilled off and dried at 110°C under reduced pressure to obtain spherical porous polymer particles with a water content of 2%. Obtained.

Next, 120 g of this polymer was transferred to a 500 m
1, 120 g of cyclohexane and 123 mg of ethylene glycol diglycidyl ether were added thereto, and the mixture was stirred and mixed at a speed of 2 Q rpm for 1 hour. Then, after distilling off the cyclohexane, water vapor was blown through a nozzle to bring the total water content of the polymer to 10% (polymer weight: 130.7 g), and then heated at 110°C for 3 hours in a hot air dryer to form spherical porous Polymer particles were obtained.

Comparative Example 4 An experiment was conducted in the same manner as in Example 7, except that a polymer with a water content of 7% was used instead of a polymer with a water content of 2%, and water vapor was not blown into the polymer particles. I got it.

Comparative Example 5 An experiment was conducted in the same manner as in Example 7, except that a polymer with a water content of 10% was used instead of a polymer with a water content of 2%, and water vapor was not blown into the polymer particles. I got it.

Comparative Example 6 An experiment was carried out in the same manner as in Example 7, except that 3.79 g of water was added in addition to cyclohexane and ethylene glycol diglycidyl ether to the polymer with a water content of 2%, and no steam was blown into the polymer. spherical polymer particles were obtained.

The performance of the obtained polymer is summarized in Table 2.

Claims (1)

[Claims] Production of a super absorbent polymer characterized by mixing hydrophilic polymer particles having a carboxyl group or carboxylate group with a crosslinking agent having two or more functional groups, and crosslinking the polymer by contacting with water vapor. Method.