JP2000143722A - Continuous neutralization of acid type water-containing gel polymer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for effectively and uniformly carrying out continuous neutralization of an acid type water-containing gel polymer by employing a single-screw kneader having a particular function. SOLUTION: This method is to continuously neutralize an acid type water- containing gel polymer by using a single-screw kneader equipped with a single screw and a cutter and grating both interlocked to the screw. The polymer is pref. obtained by subjecting, as the main monomer, a polymerizable monomer having an acid group of e.g. carboxylic acid group, sulfonic acid group or phosphoric acid group to water-solution polymerization. The single-screw kneader is formed by e.g. mounting an outer frame on a meat chopper used for producing minced meat, inserting a screw into the inner side, engaging one end of the screw with a rotating section of the motor, and fitting the cutter and grating to the other end of the rotating section of the motor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for continuously neutralizing an acid-type hydrogel polymer. More specifically, the present invention relates to an efficient continuous neutralization method of an acid-type hydrogel polymer having high viscoelasticity with a low-viscosity alkaline substance.

[0002]

2. Description of the Related Art Conventionally, even if an attempt is made to neutralize a highly viscoelastic acid-type hydrogel polymer, it cannot be stirred with a normal stirrer because the acid-type hydrogel has strong viscoelasticity and cannot be neutralized itself. Met. As a method for neutralizing this acid-type hydrogel polymer,
A method using an extruder (JP-A-49-17668) and a double-arm kneader (JP-A-1-131209) has been proposed.

[0003]

However, although neutralization by an extruder is relatively effective for neutralizing a hydrogel polymer having high viscosity and plastic deformation, the hydrogel polymer has elasticity, For a hydrogel polymer that is unlikely to undergo plastic deformation, contact between the hydrogel and the alkaline substance during neutralization is not successful, resulting in non-uniform neutralization, increasing the shear force, and attempting to forcibly neutralize. For example, there is a problem in that a large amount of shear is applied to the hydrogel polymer at the time of neutralization, the polymer is cut at the time of neutralization, and a long time is required for the neutralization. On the other hand, the neutralization of a hydrogel polymer using a machine such as a double-arm kneader having a multiaxial stirrer is performed, for example, in a hydrogel polymer in which the gel is brittle and the gel is easily fragmented by shearing force. Regarding the neutralization of water-containing gel-like polymer, although it can be neutralized relatively easily, the hydrogel polymer having high viscoelasticity and which cannot be easily fragmented only by deforming the gel even if a slight shearing force is applied is medium. It becomes difficult to sum up and spends a lot of time neutralizing. Further, with respect to the gel having adhesiveness, there has been a problem that the preliminarily fragmented gel is integrated at the time of stirring, and the gel is wrapped around the stirring blade and cannot be neutralized.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, by using a single-screw kneader having a special function, uniform neutralization can be performed efficiently and continuously. The present inventors have found that the present invention can be performed in a specific manner, and have reached the present invention. That is, the present invention is characterized in that the neutralization of the acid-type hydrogel polymer is continuously performed by a uniaxial kneader having a function of extruding, shredding and kneading, and the continuation of the acid-type hydrogel polymer. This is a neutralization method.

The functions of the single-screw extruder having extruding, shredding, and kneading functions used in the method of the present invention for continuously and uniformly neutralizing a hydrogel polymer having high viscoelasticity are as follows. . A hydrogel polymer having high viscoelasticity is continuously supplied together with an aqueous solution of an alkali substance from an inlet of the single screw extruder. A hydrogel and an aqueous solution of an alkali substance are continuously supplied to a perforated plate having a number of small holes in a kneader under a pressurized state by a screw having an extruding function. The hydrogel is further deformed under pressure by the resistance of a perforated plate having a number of small holes in the kneader, and a part of the hydrogel enters the perforated plate. The hydrogel that has entered the small hole of the eye plate is cut into small pieces by a rotary cutter installed adjacent to the front of the eye plate,
Contact with an aqueous alkaline solution supplied with the gel. The size of the small piece of gel depends on the diameter of the small hole in the eye plate,
Since the gel is usually cut into pieces of 5 mm or less, the surface area of the gel is large, and efficient and short-time neutralization occurs by contact with an aqueous alkali solution. Furthermore, when the shredded gel pieces and the alkaline aqueous solution pass through the perforated plate, moderate kneading occurs due to the wall resistance in the small holes, and further promotes neutralization. The processing time of the gel in the uniaxial kneader of the present invention is as described above.
In general, the processing is completed within one minute, and at most three minutes. Accordingly, since the polymer can be neutralized uniformly in a short time, the polymer can be prevented from being cut or hydrolyzed due to excessive shearing of the polymer, and the hydrogel can be shredded by the shredding function of the kneading machine. Then, the subsequent hydrogel can be efficiently dried.

The extrusion used in the method of the present invention,
The single-screw extruder having the shredding and kneading functions is not particularly limited as long as it is a model having the above functions, and specifically, a meat chopper used for making minced meat and the like can be exemplified. it can.

[0007] The diameter of the gel inlet of the extruder used in the present invention is not particularly limited. However, from the viewpoint of the size of the equipment from the mechanical side and the handleability of the gel, the diameter is usually 5 to 1.
Use a 50 cm one. The method of supplying the gel to the inlet is not particularly limited, but a lobe pump, a snake pump,
It is better to use a vane pump, comet pump, piston pump, or other pump that can ensure a constant supply of gel.
It is preferable from the viewpoint of securing the degree of neutralization and uniformity. on the other hand,
The alkali aqueous solution is supplied from a gel inlet or the like at the same time as the hydrogel by a usual metering pump.

[0008] The extruder used in the present invention has a screw in the extruder, and usually has a structure in which the pitch of the screw is smaller at the rear than at the front in order to press the hydrogel. .

The extruder used in the present invention is provided with a perforated plate having a number of small holes at the end of the screw.
The number of small holes in the perforated plate varies depending on the size of the perforated plate, but is usually 10 or more, preferably 20 or more. If the number of the small holes is less than 10, the diameter of the small holes becomes relatively large, and the size of the gel to be subsequently shredded becomes large. The diameter of the small hole of the perforated plate is usually 1 to 50 mm, preferably 3 to 30 mm. If it is less than 1 mm, when the hydrogel is compressed by the resistance of the perforated portion and deforms into the small hole, a large amount of shear is applied to the hydrogel and the polymer is cut, which is not preferable. On the other hand, if the diameter of the perforated plate is 50 mm or more, the size of the gel to be subsequently subdivided increases, and it takes a long time to dry. The thickness of the perforated plate is not particularly limited, but is usually 1 to 100 mm, preferably 2 to 50 mm. If the thickness of the perforated plate is less than 1 mm, kneading in the small hole of the perforated plate cannot be performed well, and if the thickness exceeds 100 mm,
When the gel advances through the small holes in the eye plate, a large share is applied to the gel due to the resistance to the wall surface.

[0010] Since the cutter installed at the end of the screw and adjacent to the front of the perforated plate usually has a structure connected to the screw, when the screw is rotated, the cutter also rotates. The distance between the perforated plate and the cutter is usually 10 mm or less. It is preferable that the gap between the perforated plate and the cutter is in contact with the perforated plate and the cutter because the narrower the gel is easily shredded by the principle of scissors,
When the perforated plate and the cutter are in contact, the perforated plate gradually wears with the rotation time of the cutter, and the thickness of the perforated plate may gradually decrease, so that the gel can be shredded within a range of 10 mm.
The following gaps may be provided.

In the present invention, in order to further improve the uniformity of neutralization, two or more single screw extruders of the present invention may be connected as necessary.

In the method of the present invention, the acid-type hydrogel polymer to be neutralized is an aqueous solution containing a polymerizable monomer having an acid group such as a carboxylic acid group, a sulfonic acid group and a phosphoric acid group as a main monomer. Obtained by polymerization. In the present invention, as the polymerizable monomer having a carboxylic acid group, unsaturated mono- or polycarboxylic acid [(meth) acrylic acid (acrylic acid and / or
Or methacrylic acid. Hereinafter, the same description is used. ), (Eta) acrylic acid, crotonic acid, sorbic acid, maleic acid, itaconic acid, cinnamic acid, etc.], and their anhydrides (maleic anhydride, etc.). Examples of the polymerizable monomer having a sulfonic acid group include aliphatic or aromatic vinyl sulfonic acid (vinyl sulfonic acid, allyl sulfonic acid, vinyl toluene sulfonic acid, styrene sulfonic acid, etc.), (meth) acryl sulfonic acid [(meth) )
Sulfoethyl acrylate, sulfopropyl (meth) acrylate], (meth) acrylamidosulfonic acid [2
-Acrylamide-2-methylpropanesulfonic acid and the like]. Examples of the polymerizable monomer having a phosphoric acid group include (meth) acrylic acid hydroxyalkyl phosphate monoester [2-hydroxyethyl acryloyl phosphate, 2-hydroxyethyl methacryloyl phosphate, phenyl-2-acryloyloxyethyl phosphate, etc.] Is raised. Among these, preferred are polymerizable monomers having a carboxylic acid group or a sulfonic acid group, and particularly preferred are polymerizable monomers having a carboxylic acid group. These monomers having an acid group may be used alone or in combination of two or more.

The acid-type hydrogel polymer can be used together with a monomer having an acid group, if necessary, with another polymerizable monomer. Examples of the polymerizable monomer include (meth) acrylate , Isobutylene, vinyl acetate, acrylamide and the like. This amount is usually 90% or less based on the total weight of all polymerizable monomers and copolymerizable crosslinking agents,
Preferably it is 70% or less. The polymerization may be carried out in the presence of starch and a cellulose derivative.

In the present invention, if necessary, a crosslinking agent (a) having at least two double bonds copolymerizable with the monomer can be copolymerized. Examples of the cross-linking agent (a) include bis (meth) acrylamide, a di- or polyester, a carbamyl ester, a di- or polyvinyl compound of a polyol and an unsaturated mono- or polycarboxylic acid,
Di- or poly- (meth) allyl ethers of polyols, di- or poly-allyl esters of polycarboxylic acids, esters and polyaryls of unsaturated mono- or poly-carboxylic acids with mono (meth) allyl ethers of polyols Roxyalkanes and the like. Among these, preferred crosslinking agents (a) are N, N'-methylenebisacrylamide, ethylene glycol diacrylate, trimethylolpropane triacrylate, tetraallyloxyethane and neopentyl glycol triallyl ether. Particularly preferred crosslinking agents (a) are tetraallyloxyethane, neopentyl glycol triallyl ether, pentaelastomer, and the like, because they do not contain a bonding mode such as an amide group or an ester group which is easily hydrolyzed during neutralization. Litol triallyl ether.

The amount of the crosslinking agent (a) is usually at most 5%, preferably at most 3%, more preferably at most 1%, based on the total weight of the polymerizable monomers. The hydrogel polymer obtained by polymerization in the presence of a crosslinking agent is used as a raw material of a superabsorbent resin, and the hydrogel polymer obtained by polymerization in the absence of a crosslinking agent is a polymer flocculant. Used as a raw material for

The acid-type hydrogel polymer of the present invention may comprise, if necessary, a second crosslinking agent having at least two functional groups capable of covalently bonding to a carboxylic acid group, a sulfonic acid group and a phosphoric acid group in the uniaxial kneader. (B) is added and further crosslinked.
Examples of the crosslinking agent (b) include a polyglycidyl ether compound, a polyol compound, and a polyamine compound. Among these, preferred crosslinking agents (b) are polyglycidyl ether compounds, polyol compounds and polyamine compounds. Particularly preferred crosslinking agent (b) forms a strong covalent bond with a carboxylic acid group to obtain a water-absorbent resin having excellent elastic modulus after shearing, and allows the crosslinking reaction to be carried out at a relatively low temperature, thereby being economical. Ethylene glycol diglycidyl ether, glycerin-1,
3-diglycidyl ether, polyamide polyamine epichlorohydrin resin, and polyamine epichlorohydrin resin.

The amount of the crosslinking agent (b) is usually at most 3%, preferably at most 2%, more preferably at most 1%, based on the total weight of the monomers. If the amount of the crosslinking agent (b) exceeds 3% by weight, the gel becomes too hard and the neutralization becomes uneven.

In the present invention, the elastic modulus of the gel of the gel polymer having a high viscoelasticity to neutralize is usually from 10,000 to
5,000,000 dyne / cm2, preferably 5
It is from 3,000 to 3,000,000 dyne / cm2. If the hydrogel has an elastic modulus of less than 10,000 dyne / cm 2, neutralization is possible without using the uniaxial kneader of the present invention, and the elastic modulus is 5,000,000 d.
If it exceeds yne / cm 2, the gel is too hard and the neutralization becomes uneven.

The neutralizing agent used in the present invention is usually 5
Used as ~ 80% aqueous solution. If it is less than 5% by weight, the amount of water becomes too large and the subsequent drying becomes inefficient, while if it exceeds 80% by weight, it is difficult to uniformly neutralize.

The neutralizing agent used in the present invention includes alkali metal compounds (such as sodium hydroxide and potassium hydroxide) and alkali metal carbonates (such as sodium carbonate,
Sodium bicarbonate, etc.), ammonia, amine compounds (alkylamines such as methylamine and trimethylamine; alkanolamines such as triethanolamine and diethanolamine) and two or more of these. The degree of neutralization varies depending on the application, but when used as a raw material of a superabsorbent resin, it is usually 60 to 90.
Mol%, preferably 65 to 80 mol%. When the degree of neutralization is less than 60 mol%, the pH of the resulting superabsorbent resin becomes acidic, while when it exceeds 90 mol%, the pH becomes alkaline, and in any case, it is preferable in terms of safety to human skin. Therefore, it is not suitable as a component of the absorbent composition for disposable diapers.

The method of polymerizing the acid-type hydrogel polymer of the present invention may be a conventionally known method, for example, a method of polymerizing using a radical polymerization catalyst or a method of irradiating with radiation, electron beam, ultraviolet ray or the like. Method. The polymerization is carried out by aqueous solution polymerization using water as a solvent. Usually, the solvent is water alone, but if necessary, it may be carried out in a mixed solvent of water and a hydrophilic solvent. Examples of the hydrophilic solvent include methanol, ethanol, acetone, N, N-dimethylformamide, dimethyl sulfoxide, and methyl ethyl ketone. The concentration of the aqueous solution of the polymerizable monomer is usually 10% by weight or more, preferably 15 to 8%.
0% by weight. If it is less than 10% by weight, the molecular weight of the obtained resin tends to be low.

The drying method is usually a method of drying by heating with hot air at a temperature of 50 to 230 ° C., a method of drying a thin film by using a drum dryer or the like usually heated to 50 to 230 ° C., a reduced pressure drying method, a freeze drying method. For example, a normal method may be used. There is also no particular limitation on the pulverizing method, and ordinary apparatuses such as a hammer pulverizer, an impact pulverizer, a roll pulverizer, and a jet air pulverizer can be used.

[0023]

The present invention will be further described with reference to the following examples and comparative examples, but the present invention is not limited to these examples. The elastic modulus of the hydrogel polymer, the amount of pressure-absorbed polymer after drying, the water-soluble component (above the superabsorbent resin), and the intrinsic viscosity [η] (polymer flocculant) were measured by the following methods. Hereinafter, unless otherwise specified,% indicates% by weight.

The measuring method is as follows. Elastic modulus of hydrogel polymer: about 2 for acid type hydrogel polymer
Cut into cm square. This gel is heated to 20-30 ° C,
Place it at the center of the support table of the creep meter (manufactured by Yamaden Corporation). Next, the plunger (plunger NO.
Lower the upper cylinder connected to 2) to 50
The gel was compressed until a load of 0 g was applied, and the creep curve of the gel was measured. The viscosity and elasticity of the hydrogel were calculated using an automatic analyzer attached to the creep meter, and the value of the elasticity was defined as the elastic modulus of the acid-type hydrogel polymer.

Absorption under pressure: (Crosslinked polymer-highly water-absorbent resin) 0.1 g of dried polymer is placed in a cylindrical plastic tube (inner diameter 30 mm, height 60 mm) having a 250 mesh nylon net attached to the bottom surface. The sample was spread evenly, and a weight having an outer diameter of 30 mm was placed on the sample so as to give a load of 20 g / cm 2. Petri dish containing 60 ml of artificial urine (diameter:
12 cm) was immersed for 30 minutes with the nylon mesh side facing down, and the 10-fold increase in weight after 30 minutes was taken as the absorption under pressure.

Water-soluble component: (Crosslinked polymer-superabsorbent resin) 2 g of a sample was added to 300 g of 1% saline solution to sufficiently swell, and stirring was continued for 5 hours. Thereafter, the solution was filtered through a 0.2-micron membrane filter, and the filtrate (ag) was evaporated to dryness to measure the residual weight (bg). The water-soluble component was calculated by the following equation. Water-soluble component (%) = b / a × 150 × 100

Intrinsic viscosity [η]: (Non-crosslinked body-polymer flocculant) 1.0 g of the neutralized acid-type hydrogel polymer was precisely weighed, and 200
into a volumetric flask. About 1 pure water in a volumetric flask
To the mixture, 00 ml was added, and the mixture was slowly stirred with a stirrer for 12 hours in a cool and dark place (at 20 ° C. or less, with light blocking). 100 ml of a 4N aqueous sodium hydroxide solution was added to the stirred solution, and stirring was continued for about 1 hour to completely dissolve. 0.08%, 0.05% using whole pipette and volumetric flask
And 2N sodium hydroxide solution was added so as to obtain a polymer pure content of 0.02%. 3
A Cannon-Fenske viscometer is set vertically in water in a thermostat adjusted to 0 ± 0.1 ° C., and 10 ml of each concentration solution is put into the Canon-Fenske viscometer. After adjusting the temperature of the sample solution for about 30 minutes, the outflow time (t0) of use and the outflow time (t) of 2N sodium hydroxide were measured three times and an average value was obtained. The reduced viscosity (ηsp / C) was obtained by the following equation. Was calculated. ηsp / C = (t−t0) / t0 × 1 / C The concentration C (%) of each sample solution is plotted on the horizontal axis of the graph, and the reduced viscosity (ηsp / C) is plotted on the vertical axis, and each measured value is plotted. ,
A straight line passing through each measured value is drawn, and a point that intersects the vertical axis, that is, C
The value of ηsp / C at = 0 is the intrinsic viscosity [η].
Note that the intrinsic [η] indicates that the molecular weight of the polymer is
It is generally used as an index of the molecular weight of a high molecular weight substance whose molecular weight cannot be measured due to the above factors.

Production Example 1 [Production of acid-type hydrogel polymer (A)] Acrylic acid 175 was placed in a glass reactor having a capacity of 1 liter.
g, N, N'-methylenebisacrylamide 0.03 g
And 320 g of deionized water.
C. Nitrogen is introduced into the contents to reduce the amount of dissolved oxygen to 0.1.
After adjusting the concentration to 3 ppm or less, 1 g of a 0.11% aqueous solution of hydrogen peroxide, 1.2 g of a 0.1% aqueous solution of ascorbic acid, and 2% aqueous solution of 4,4′-azobis (4-cyanoarenic acid) 2. Add 5 g to initiate polymerization,
After standing polymerization for about 5 hours, an acid-type hydrogel polymer (A) was obtained. When the viscoelasticity of this hydrogel polymer was measured using a creep meter, the elastic modulus of the gel was about 380,000 dyne / cm 2.

Production Example 2 [Production of acid-type hydrogel polymer (B)] Acrylic acid 50 was placed in a 1-liter glass reaction vessel.
g, 50 g of acrylamide and 400 g of deionized water, and the temperature of the contents was kept at 5 ° C. After nitrogen was introduced into the contents to reduce the amount of dissolved oxygen to 0.3 ppm or less, 1 g of a 0.11% aqueous solution of hydrogen peroxide and 0.1 g of ascorbic acid were added.
The polymerization was started by adding 1.2 g of a 1% aqueous solution and 2.5 g of a 2% aqueous solution of 2,2′-azobis (2-methylpropionamide) dihydrochloride, followed by polymerization for about 5 hours, thereby obtaining an acid-type hydrogel. A polymer (B) was obtained. When the viscoelasticity of this hydrogel polymer was measured using a creep meter, the elastic modulus of the gel was about 120,000 d.
yne / cm2. The intrinsic viscosity [η] was measured as an index of the molecular weight of the hydrogel polymer (B).

Example 1 A commercially available meat chopper (Type, manufactured by Iizuka Kogyo Co., Ltd.)
e: 12RF) on the outer layer (inner diameter 70mm, T-shaped cylindrical)
And a screw (screw length: 12)
cm) and one end of the screw was fitted into the rotating part of the motor. At the other end of the screw, a rotary cutter and a perforated plate (number of perforated holes: 50, small hole diameter 5 m)
m, thickness 8 mm, made of SUS) and fixed to the exterior part with a screw-on lid. 500 g of the acid-type hydrogel polymer (A) cut into 3 to 8 cm using scissors and 292 g of a 48% aqueous sodium hydroxide solution were put into the meat chopper through the inlet of the gel and connected by rotating the motor. Rotate the screw at 100 rpm,
The gel was compressed and pushed in the direction of the cutter and the dish. Immediately, an uddon-like gel in which a hydrogel having a size of about 2 mm square, which had been shredded with a rotary cutter and aggregated, was discharged from a small hole in a perforated plate serving as a gel outlet. When the discharged gel was again put into the inlet of the meat chopper, a substantially uniform powdery gel was discharged from a small hole in the perforated plate serving as the outlet. The time from the introduction of the gel to the discharge thereof was about 30 seconds in one operation, and about 1 minute in total. In this gel,
When the phenolphthalein solution was added, no red coloring was observed in any of the gel portions. This gel was stretched on a drum dryer having a surface temperature of 150 ° C. and dried for about 5 minutes. The dried product is 18 to 10 using an impact-type pulverizer.
It was pulverized to 0 mesh, and the amount of dried product under pressure and the soluble component were measured.

Example 2 500 g of the acid-type hydrogel polymer (A) cut into 3 to 8 cm with scissors from the inlet of the gel of the meat chopper used in Example 1 and 55 g of a 48% aqueous sodium hydroxide solution , And the connected screw was rotated at 100 rpm by rotating the motor to compress and push the gel in the direction of the cutter and the dish. Immediately, a substantially uniform oudon-like gel was discharged from a small hole in the eye plate serving as the outlet for the gel. The time from the introduction of the gel to the discharge thereof was about 30 seconds. The gel was taken out and the intrinsic viscosity [η] of the polymer was measured.

Comparative Example 1 The rotary cutter was removed from the meat chopper used in Example 1 and used as a single screw extruder. The acid cut into 3 to 8 cm from the gel inlet of the single screw extruder with scissors was used. 500 g of the hydrated gel polymer (A) and 292 g of a 48% aqueous sodium hydroxide solution were charged, and the connected screw was rotated by rotating the motor to compress and push the gel in the direction of the plate. The gel was hardly discharged from the small hole in the eye plate, which is the outlet of the gel, and the motor was overloaded and the rotation of the motor was stopped. It took about 5 hours to complete. When a phenolphthalein solution was added to this gel, the surface of the discharged gel was colored red. This gel was stretched on a drum dryer having a surface temperature of 150 ° C. and dried for about 5 minutes. The dried product was pulverized to 18 to 100 mesh using an impact-type pulverizer, and the amount of pressure absorption and the soluble component of the dried product were measured.

Comparative Example 2 The rotary cutter was removed from the meat chopper used in Example 1 and used as a single screw extruder. The acid cut into 3 to 8 cm from the gel inlet of the single screw extruder with scissors was used. 500 g of the type hydrogel polymer (B) and 55 g of a 48% aqueous sodium hydroxide solution were charged, and the connected screw was rotated by rotating the motor to compress and push the gel in the direction of the plate. The gel was hardly discharged from the small hole in the eye plate, which is the outlet of the gel, and the motor was overloaded and the rotation of the motor was stopped. It took about 3 hours to complete. When a phenolphthalein solution was added to this gel, the surface of any discharged gel was colored red. The gel was taken out and the intrinsic viscosity [η] of the polymer was measured.

Comparative Example 3 Content 2000 ml, opening 160 mm × 150 mm,
500 g of the hydrogel polymer (A) cut into 3 to 8 cm and 297 g of a 48% aqueous sodium hydroxide solution were added to a double-arm kneader having two sigma-type blades having a depth of 135 mm and a blade diameter of 70 mm. The two sigma-type springs were rotated at 50 rpm and 70 rpm, respectively, for 2 hours. However, the hydrogel polymer was hardly subdivided and the aqueous sodium hydroxide solution was collected at the lower part of the double arm kneader. When the rotation was continued, the rotation was terminated because the lower portion of the aqueous sodium hydroxide solution was almost gone. This gel was laminated on a hot air dryer having a surface temperature of 150 ° C., and dried for about 60 minutes. The dried product was pulverized to 18 to 100 mesh using an impact-type pulverizer, and the amount of pressure absorption and the soluble component of the dried product were measured.

Comparative Example 4 To the double-armed kneader used in Comparative Example 3, 500 g of the hydrogel polymer (B) cut into 3 to 8 cm and 55 g of a 48% aqueous sodium hydroxide solution were added. The two sigma type springs were stirred at 50 rpm and 70 rpm, respectively.
The hydrogel polymer could not be subdivided and integrated, and the gel wound around the sigma blade. Stirring was continued for 2 hours, but the aqueous sodium hydroxide solution had accumulated at the bottom of the double-arm kneader,
Stirring was further continued for 22 hours. However, since it was confirmed that the aqueous sodium hydroxide solution still accumulated in the lower part, neutralization was abandoned.

Table 1 shows the pressure absorption and water-soluble components of Example 1, Comparative Examples 1 and 3, and the intrinsic viscosities of Example 2, Comparative Examples 2 and 4, and the hydrogel polymer (B).

[0037]

[Table 1]

From Table 1, it can be seen that, in Example 1, the superabsorbent resin had a large amount of pressure absorption and a small water-soluble component in Example 1.
In Comparative Examples 1 and 3, it can be seen that the amount of pressure absorption was small, the water-soluble component was large, and polymer cleavage occurred. In the polymer flocculant, the intrinsic viscosity of Example 2 is almost the same as the intrinsic viscosity of the hydrogel polymer (B), but the intrinsic viscosity of Comparative Example 2 is higher than the intrinsic viscosity of the hydrogel polymer (B). It can be seen that the polymer has become smaller and the polymer has been cut. In Comparative Example 4, neutralization could not be performed.

[0039]

The present invention has the following features and effects. By using a single screw extruder having the functions of extruding, shredding and kneading the gel, the acid-type hydrogel polymer having high viscoelasticity can be uniformly neutralized in a short time. The polymer can be neutralized in a short time and the shear on the gel at the time of neutralization is low, so that the polymer is not degraded and deteriorated during the neutralization. By continuously supplying the hydrogel polymer and the aqueous solution of the neutralizing agent, continuous neutralization of the acid-type hydrogel polymer is possible, and the size of the uniaxial kneader of the present invention is reduced. Suitable for.

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[Procedure amendment]

[Submission Date] January 11, 2000 (2000.1.1)
1)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0004

[Correction method] Change

[Correction contents]

[0004]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, by using a single-screw kneader having a special function, uniform neutralization can be performed efficiently and continuously. The present inventors have found that the present invention can be performed in a specific manner, and arrived at the present invention. That is, the present invention is to continuously neutralize the acid-type hydrogel polymer by a single screw kneader having a single screw, a cutter and a perforated plate, and a function of extrusion, shredding and kneading. This is a method for continuously neutralizing an acid-type hydrogel polymer, which is characterized in that the method is carried out in a continuous manner.

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Claims (9)

[Claims] 1. A method for continuously neutralizing an acid-type hydrogel polymer, wherein the neutralization of the acid-type hydrogel polymer is performed by a uniaxial kneader having functions of extrusion, shredding and kneading. . 2. The method according to claim 1, wherein the functions of the single-screw kneader are extrusion, shredding, and kneading. 3. The method according to claim 1, wherein the single-screw kneader is a meat chopper. 4. The method according to claim 1, wherein two or more uniaxial kneaders are connected for neutralization. 5. The method according to claim 1, wherein the acid-type hydrogel polymer is a gel obtained by polymerizing a polymerizable monomer having a carboxylic acid group in an aqueous solution. 6. The gel according to claim 1, wherein the acid-type hydrogel polymer is a polymer obtained by polymerizing a polymerizable monomer having a carboxylic acid group in an aqueous solution in the presence of a crosslinking agent. The method described in. 7. The acid-type hydrogel polymer having an elasticity of 10,
The method according to any one of claims 1 to 6, wherein the amount is from 000 to 5,000,000 dyne / cm2 or more. 8. The elasticity of the acid-type hydrogel polymer is 50,
The method according to any one of claims 1 to 7, wherein the molecular weight is 000 to 3,000,000 dyne / cm2 or more. 9. The method according to claim 1, wherein the neutralization is performed with an aqueous solution of an alkaline substance.