JPH05310806A - Production of hydrophilic polymer - Google Patents

Abstract

PURPOSE:To produce a hydrophilic polymer which has a low coarse particle content, is less apt to generate a fine powder upon grinding, has a reduced residual monomer content, and is useful particularly as a water-absorbing resin. CONSTITUTION:An aqueous monomer solution which yields a polymer in water- based gel form is polymerized in a reactor while pulverizing the polymer gel by the shear generated by the rotation of a rotating arm (a) or agitating element (b). The polymerization is conducted under such shearing conditions that a function expressed by the amount of the solution introduced, the radius of the circle formed by the rotation of the arm (a) or element (b), the rotational speed and the width of the arm (a) or element (b), and the space between the arm (a) or element (b) and the inner wall of the reactor has a value within a specific range. After the polymerization, the resulting polymer in a water- based gel form is heated at 60-120 deg.C under a reduced pressure to reduce the water content from 40-70 to 10-35wt.%.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing a hydrophilic polymer. More specifically, the present invention relates to a method for producing a hydrophilic polymer having a uniform particle size distribution and a small amount of unreacted residual monomer by polymerizing an aqueous solution of a monomer which becomes a hydrogel polymer by polymerization.

[0002]

2. Description of the Related Art Conventionally, as a method for obtaining a hydrophilic polymer by polymerizing an aqueous solution of a water-soluble ethylenically unsaturated monomer, which is a hydrogel polymer by polymerization, into a hydrogel polymer and drying it. Are known, such as a method of polymerizing a monomer aqueous solution by reverse phase emulsification or a reverse phase suspension in a hydrophobic organic solvent, and a method of casting polymerization of a monomer aqueous solution.

However, since a large amount of organic solvent is used in the inverse emulsion polymerization method and the inverse suspension polymerization method, it is dangerous in terms of disaster prevention and also causes toxicity to workers. Further, since the obtained hydrogel polymer has a very small particle size and a large amount of fine powder, it is difficult to handle, and the dried product has a problem such as generation of dust.

On the other hand, the method of casting polymerization of an aqueous monomer solution is superior to the former in that no organic solvent is used.
Special polymerization equipment is required to remove the heat of reaction during polymerization. Further, in order to obtain a dried polymer, it is inefficient to dry the hydrogel polymer produced by the polymerization as it is, so it is necessary to mechanically subdivide the surface area to increase the surface area. As a method for subdividing the water-containing gel-like polymer, there are methods such as cutting and extruding, but in any case, the water-containing gel-like polymer has strong rubber-like elasticity, so that it cannot be subdivided well, or There were problems such as requiring energy.

In order to solve the above problems, the inventors of the present invention subdivide a hydrous gel polymer produced in a container having a rotating stirring shaft with the progress of polymerization by a shearing force generated by the rotation of the stirring shaft. Meanwhile, a method of aqueous solution polymerization (JP-A-57-34101 and JP-A-60-55002) was proposed. These methods are superior to the reverse phase emulsion polymerization method and the reverse phase suspension polymerization method in that an organic solvent is not used, and further, by evaporation of water from the surface of the water-containing gel polymer produced as the polymerization proceeds, the reaction It is characterized in that heat can be easily removed and particles of the hydrogel polymer can be obtained all at once at the end of the polymerization reaction. However, even with this method,
The hydrogel polymer particles discharged from the container after the polymerization sometimes contained a large amount of coarse particles. If the particle size is large, it takes a long time to dry to the center of the particle, so that the product may contain undried particles. Since the undried particles have rubber-like elasticity, there is a problem that not only the load at the time of crushing increases but also the crushing cannot be performed in a severe case. Further, if the pulverization time is lengthened, the amount of fine powder generated during pulverization increases, which is not preferable in terms of environmental hygiene. In particular, when the water-containing gel polymer is a water-absorbent resin, if the amount of coarse particles or fine powder increases, not only the problem of undriedness and environmental hygiene, but also the so-called "Mamako" at the time of water absorption, the water absorption rate decreases, In addition, the water-soluble portion increased and the quality deteriorated.

[0006] More recently, from the viewpoint of safety, reduction of unreacted monomer remaining in the water-absorbent resin has been demanded. If there are many coarse particles and the particle size distribution varies, the drying is uneven. Therefore, there has been a problem that the residual monomer cannot be reduced sufficiently.

[0007]

SUMMARY OF THE INVENTION The present invention solves the above problems of the prior art. Therefore, an object of the present invention is to provide a method for efficiently producing a hydrophilic polymer having a uniform particle size distribution and less residual monomers. Especially when the hydrophilic polymer is a water absorbent resin, the purpose of the present invention is to
It is also intended to provide a product having a high water absorption rate that does not cause "mamako" with a low water-soluble content.

[0008]

Means for Solving the Problems In the present invention, an aqueous solution of a water-soluble ethylenically unsaturated monomer, which becomes a hydrogel polymer by polymerization, and a polymerizable monomer containing a crosslinking agent, is rotated or stirred. In a method of polymerizing a hydrogel polymer, which is formed with the progress of polymerization in a reaction vessel having blades, by subdividing by a shearing force generated by the rotation of the rotating arm or stirring blade, it is defined by the following mathematical formula (I). H value is 0.0
After polymerizing under shear conditions in the range of 005 to 1.0,
The present invention relates to a method for producing a hydrophilic polymer, characterized in that the water content of the hydrogel polymer is reduced from 40 to 70% by weight to 10 to 35% by weight at a temperature of 60 to 120 ° C under reduced pressure.

[0009]

[Equation 2]

[0010]

In the formula (I), W is the charged amount of the aqueous monomer solution [kg], which corresponds to the initial charged amount in the batch polymerization, and the monomer aqueous solution supply rate [kg / in the continuous polymerization.
sec] and residence time [sec]. Usually, it is a value of 1 to 5000. When it is less than 1, productivity of the hydrogel polymer is remarkably low, and when it exceeds 5000, not only a very large reaction vessel is required, but also control of the polymerization reaction becomes difficult. ..

N is the number of rotary shafts provided with rotary arms or stirring blades, and is usually a value of 1-10. A minimum of 1 is required to subdivide the hydrous gel polymer produced as the polymerization progresses, and when it exceeds 10, the structure of the reaction vessel having the rotating shaft becomes complicated, resulting in high cost and cleaning. It may be difficult to remove.

The origin is the inner wall of the reaction vessel with a rotating shaft provided with a rotating arm or a stirring blade (however, when the inner walls of a plurality of reaction vessels are opposed to each other, the inner wall of one of the reaction vessels is the origin). , Considering a cylindrical coordinate system in which the rotation axis is the Z axis, the radial direction is r, and the angle is θ, the tip of the rotating arm or the stirring blade can be represented by (r, θ, z).

Zi is [m] which represents the position of a point on the i-th rotation axis, and is usually a value of 0-10. 10
If it exceeds the above range, the reaction vessel having a rotating shaft becomes extremely long, which may cause problems in the strength of the reaction vessel, the installation location and the like.

Θi is the angle [rad] of the tip of the rotating arm or the stirring blade at the position zi of the i-th rotating shaft,
It is a value of 0 to 2π.

Ri [zi] is the position zi of the i-th rotation axis
The radius of gyration [m] when the tip of the rotary arm or the stirring blade moves close to the inner wall of the reaction vessel which is not orthogonal to the rotation axis in the reaction vessel, and is usually a value of 0.01 to 2. 0.
When it is less than 01, the hydrogel polymer produced with the progress of polymerization is difficult to be subdivided by the rotating arm or stirring blade, and when it exceeds 2, a large amount of energy is required to rotate the rotating arm or stirring blade. Not only is it necessary, but also an extremely large reaction vessel is required, making it difficult to control the polymerization reaction.

Li is a rotating arm or agitator that is sheared when the tip of a rotating arm or a stirring blade attached to the i-th rotating shaft moves closer to the inner wall of the reaction container that is not perpendicular to the rotating shaft in the reaction container. The width [m] of the tip of the blade, and when a plurality of rotary arms or stirring blades are attached to the rotary shaft, it is represented by the sum of the widths of the tips, usually 0.
It is a value of 001-10. When it is less than 0.001, the sheared portion for subdividing the hydrogel polymer produced with the progress of polymerization becomes remarkably small, and the hydrogel polymer becomes difficult to subdivide. On the other hand, when it exceeds 10, the reaction container having the rotating arm or the stirring blade becomes extremely long,
There may be a problem with the strength of the reaction container or the installation location.

Ni is the rotation speed [rps] of the i-th rotating shaft.
And is usually a value of 0.01 to 10. When it is less than 0.01, the water-containing gel-like polymer produced as the polymerization proceeds is less likely to be fragmented. On the other hand, when it exceeds 10, the rotation speed becomes high, not only a large amount of energy is required, but also an effect commensurate with it is not obtained, and further the performance of the obtained product, for example, a water-absorbent resin, may be deteriorated.

Ci (zi, θi) is the inner wall of the reaction vessel in which the tip of the rotating arm or stirring blade attached to the i-th rotating shaft at the position zi of the i-th rotating shaft is not perpendicular to the rotating shaft in the reaction container. A gap [m] between the tip of the rotary arm or the stirring blade and the inner wall of the reaction vessel when the position of the tip of the rotary arm or the stirring blade is in the direction of the angle θi when moving closely;
Usually, it is a value of 0.0001 to 0.05. 0.0001
When the amount is less than the above, the hydrous gel polymer produced as the polymerization proceeds becomes difficult to be caught in the gap between the container wall and the rotary arm, and the hydrous gel polymer is less likely to be fragmented. On the other hand, when it exceeds 0.05, the shearing force applied to the hydrous gel polymer becomes small, and the hydrous gel polymer becomes difficult to be fragmented.

Equation (I) is θi at the i-th rotation axis.
And zi are double-integrated and summed over all rotation axes.

The reaction vessel having a rotating arm or a stirring blade used in the present invention may be one capable of imparting a shearing force, a cutting force or a shredding force to the hydrogel polymer produced by the rotation of the rotating arm or the stirring blade. There is no particular limitation. Examples of such a reaction vessel include various kneaders, extruders, kneaders, and the like having a large shearing force, and a double-arm kneader having a structure shown in FIG. 1 is particularly preferable. ..

FIG. 1 shows the respective dimensions in the case of a dual-arm kneader. In such a dual-arm kneader, the tip of the rotary arm approaches the inner wall of the reaction vessel which is not perpendicular to the rotary shaft in the reaction vessel. Radius of rotation Ri (zi) and the gap between the tip of the rotating arm and the inner wall of the reaction vessel Ci (zi, θi)
Is constant regardless of zi, and Ci (zi, θ
In many cases, the angle at which the rotary arm moves while i) is kept sufficiently small, that is, the angle at which an effective shearing force is generated, is limited to φ in the case of FIG. In such a case, the above formula (I) is simplified and represented as the following formula (II).

[0022]

[Equation 3]

According to the production method of the present invention, the resulting hydrophilic polymer has an extremely small content of coarse particles and a small amount of residual monomer. Since the content of coarse particles is small and the particles are uniformly dried in a short time, generation of fine powder during pulverization can be suppressed. By suppressing the generation of fine powder, environmental hygiene problems do not occur.

The water-soluble ethylenically unsaturated monomer used in the present invention is not particularly limited as long as it is a water-soluble ethylenically unsaturated monomer, and examples thereof include (meth) acrylic acid and maleic anhydride. , Fumaric acid, itaconic acid, 2-
(Meth) acryloylethanesulfonic acid, 2- (meth)
Acryloyl propane sulfonic acid, 2- (meth) acrylamide 2-methyl propane sulfonic acid, vinyl sulfonic acid, styrene sulfonic acid and other acid group-containing monomers; metal salts of the acid group-containing monomers; ammonium salts or amine salts ;
Nonionic hydrophilic group-containing monomers such as (meth) acrylamide, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, polyethylene glycol (meth) acrylate, and alkoxy polyethylene glycol (meth) acrylate; diethylaminoethyl Amino group-containing monomers such as (meth) acrylate, diethylaminopropyl (meth) acrylate, and dimethylaminopropyl (meth) acrylamide; quaternized products of the amino group-containing monomer and the like can be mentioned. One kind or two or more kinds selected can be used. Preferred monomers are acid group-containing monomers, particularly preferably acrylic acid and methacrylic acid and their alkali metal salts, ammonium salts or amine salts. Further, other monomers may be used in combination so long as the performance of the hydrophilic polymer obtained in the present invention is not significantly impaired.

The cross-linking agent used in the present invention is for forming a cross-linking structure during polymerization. Examples of such a cross-linking agent include compounds having two or more unsaturated bonds in the molecule, water-soluble ethylenic A compound having two or more groups that react with a functional group such as an acid group, a hydroxyl group, an amino group, etc., in a saturated monomer, an unsaturated bond in a molecule and a group that reacts with a functional group of a monomer A compound having one or more each, a compound having two or more points reacting with a functional group of a monomer in the molecule, or a hydrophilic compound having a hydrophilic structure capable of forming a crosslinked structure by a graft bond or the like when a monomer component is polymerized. A molecule etc. can be mentioned.

Examples of these crosslinking agents include, for example, N,
Polyvalent (meth) acrylamide compounds such as N'-methylenebis (meth) acrylamide; (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, glycerin di (meth) acrylate, glycerin acrylate methacrylate , Trimethylolpropane di (meth) acrylate, trimethylolpropane acrylate methacrylate, pentaerythritol di (meth) acrylate, glycerin tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol Poly (meth) acrylates such as tetra (meth) acrylate; triallylamine, poly (meth) allyloxyalkane, triallyl isocyanate Rate, triallyl cyanurate, polyvalent allyl compounds such as triallyl phosphate;
(Poly) ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, and other polyvalent glycidyl compounds; 2,4-toluylene diisocyanate, hexamethylene diisocyanate, and other polyvalent isocyanate compounds; poly Oxazoline compounds;
Reactive group-containing (meth) acrylamide or (meth) acrylate such as N-methylol (meth) acrylamide, glycidyl (meth) acrylate; polyvalent metal such as aluminum chloride, magnesium chloride, calcium chloride, aluminum sulfate, magnesium sulfate, calcium sulfate Salts: hydrophilic polymers such as starch, cellulose, polyvinyl alcohol, poly (meth) acrylic acid and cross-linked products thereof, and the like, and one or more kinds selected from these groups or two or more kinds that do not react with each other Can be used.

The amount of these cross-linking agents used is not particularly limited, but when the hydrophilic polymer is a water-absorbing resin, depending on the type of cross-linking agent used, the amount of the water-soluble ethylenically unsaturated monomer is 0.001 to 20% by weight, preferably 0.005
It is preferably used in the range of ˜5% by weight. If the amount used is less than 0.001% by weight, the crosslink density of the resulting hydrogel polymer will be small, and the uncrosslinked portion will be remarkably large, making it difficult for the hydrogel polymer to be fragmented. Again 2
If the amount exceeds 0% by weight, the water absorption capacity of the resulting water absorbent resin may be remarkably small.

The monomer concentration of the water-soluble ethylenically unsaturated monomer aqueous solution in the present invention is in the range of 30 to 80% by weight. When the monomer concentration is less than 30% by weight, the productivity may be deteriorated and the residual monomer may be insufficiently reduced. On the other hand, if it exceeds 80% by weight, the particle size of the resulting hydrogel polymer may become large or the control of polymerization may become difficult, resulting in a decrease in water absorption performance.

As a method for polymerizing the aqueous monomer solution in the present invention, a usual polymerization method can be used. Examples of such a method include a radical polymerization method and a polymerization method using an active energy ray, but a method using a water-soluble radical polymerization initiator is preferable. As the water-soluble radical polymerization initiator, known ones can be used, and examples thereof include persulfates such as potassium persulfate, sodium persulfate and ammonium persulfate; hydrogen peroxide, t-butyl hydroperoxide, Peroxides such as cumene hydroperoxide; 2,2'-azobis-
Examples thereof include water-soluble azo compounds such as 2-amidinopropane hydrochloride. Further, these may be used in combination with sulfite, hydrogen sulfite, thiosulfate, 1-ascorbic acid and the like as a redox initiator. The amount of these polymerization initiators used is not particularly limited, but is usually 0.001 to 10% by weight, preferably 0.0
It is from 02 to 5% by weight.

The reaction container having a rotating arm or a stirring blade used in the present invention can impart a shearing force, a cutting force, or a shredding force to the hydrogel polymer produced by the rotation of the rotating arm or the stirring blade. There is a need. As such a reaction vessel, various kneading machines such as an internal mixer and a Banbury mixer, an extruder, a kneader and the like having a large shearing force are required. Preferable ones are kneader-like ones, especially double-arm type kneader-like ones. In addition, these reaction vessels may have a compression pressurizing function and a vacuum degassing function.

When using the double arm type kneader, 2
The rotating arms of the rotating shaft of the book are used by rotating them at a constant speed or a non-uniform speed. The rotary arm of the rotary shaft may be any of sigma type, S type, Banbury type and the like. The reaction vessel is preferably provided with a jacket for heating the aqueous monomer solution and removing heat of polymerization. Furthermore, it is desirable that the reaction vessel can be depressurized.

The most important requirement in the present invention is that the value of H defined by the above formula (I) is 0.0005-1.
After polymerizing in the range of 0, preferably 0.001 to 0.3, the water content of the hydrogel polymer is reduced from 40 to 70% by weight to 10 to 35% by weight at a temperature of 60 to 120 ° C. under reduced pressure. Is. When the H value is less than 0.0005, the amount of coarse particles of the hydrophilic polymer increases, and when the H value exceeds 1.0, not only the amount of fine powder increases, but also the hydrophilic polymer In some cases, deterioration of performance such as increase in water-soluble portion may be observed. At a temperature of less than 60 ° C, it may take a long time to reach a water content of 10 to 35% by weight, and reduction of the residual monomer may not be observed. It is difficult to decrease and the water-soluble content may increase. Further, the water content of the water-containing gel polymer is 40 to
If it is out of the range of 70% by weight, it is necessary to add water or predry it to adjust the water content. After adjusting the water content, by adjusting the water content to 10 to 35% by weight at a temperature of 60 to 120 ° C. under reduced pressure, the residual monomer amount of the obtained hydrophilic polymer can be significantly reduced. However, even if the water content is reduced to less than 10% by weight, it takes more time than necessary and it is difficult to further reduce the residual monomer. If the water content exceeds 35% by weight, the reduction of the residual monomer will be insufficient. The water content is 10 to 35
After the weight%, it may be further dried by an ordinary dryer such as a hot air dryer.

As a further preferred embodiment of the present invention,
By carrying out the polymerization under reduced pressure, the amount of coarse particles is further reduced, the particle size distribution becomes uniform, pulverization becomes easy or unnecessary, and generation of fine powder is suppressed. In addition, since the water-soluble portion also decreases, it is preferable to polymerize under reduced pressure. The degree of reduced pressure for carrying out the polymerization is more preferably 1 to 500 mmHg. If the pressure in the reaction vessel is less than 1 mmHg, not only will the monomer be scattered and a decompression device with a large decompression capability will be required, but it will be economically disadvantageous, and the effect commensurate with it will not be recognized.

When the aqueous monomer solution is polymerized in the present invention, various additives which do not affect the polymerization reaction may be added in order to appropriately adjust the performance of the resulting hydrophilic polymer. The additive may be added to the monomer aqueous solution in advance prior to the polymerization, or may be added to the hydrogel polymer during or after the polymerization or the polymer after drying. Examples of such additives include hydrophilic fibers, organic fine particles and inorganic fine particles. For example, when the hydrophilic polymer is a water-absorbent resin, when pulp is added as a hydrophilic fiber to the monomer aqueous solution and polymerized, not only the effect of removing the heat of polymerization is improved, but also fine powder generated during pulverization The amount decreases, and the water absorption rate of the resulting water absorbent resin also increases.

When the hydrophilic polymer obtained in the present invention is a water absorbent resin, it may be surface-crosslinked. Since the hydrophilic polymer obtained in the present invention has few coarse particles and a uniform particle size distribution, it can be uniformly mixed even if a surface cross-linking agent usually used for surface cross-linking of the water-absorbent resin is added, resulting in uniform surface cross-linking. it can. Particularly in the present invention, the value of H defined by the above formula (I) is 0.0005 to 1.0, preferably 0.00.
Add a surface cross-linking agent after polymerization in the range of 1 to 0.3,
By adjusting the water content of the hydrogel polymer at a temperature of 60 to 120 ° C. under reduced pressure from 40 to 70% by weight to 10 to 35% by weight, a surface-crosslinked water-absorbent resin can be obtained from the monomer at a stretch. It is possible and the process can be simplified.

In carrying out the present invention, if necessary, a surfactant may be added in advance to the aqueous monomer solution or to the hydrogel polymer during or after the polymerization. By adding the surfactant, the mutual adhesiveness of the water-containing gel-like polymer particles is reduced, and the discharge from the reaction vessel and the handling during drying become easy. Examples of such a surfactant include polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene acyl ester, oxyethyleneoxypropylene block copolymer, Nonionic surfactants such as sugar fatty acid ester; anionic surfactants such as sodium laurate, sodium dialkylsulfosuccinate, sodium polyoxyethylene lauryl ether sulfate, and the like. Among these, one kind or two or more kinds can be used.

[0037]

EXAMPLES The present invention will be described in more detail below with reference to Examples and Comparative Examples, but the scope of the present invention is not limited to these Examples. In addition, (1) of Examples and Comparative Examples
The water absorption ratio, (2) water-soluble portion, (3) residual monomer, (4) particle size distribution, (5) water content were measured by the following methods.

(1) Water absorption capacity: about 0.2 g of water-absorbent resin powder
A non-woven tea bag bag (40 mm x 150 m
m), was uniformly dipped in 0.9% saline and weighed after 30 minutes. The water absorption capacity when only the tea bag type bag was immersed was set as a blank, and the water absorption capacity of the water absorbent resin powder was determined according to the following mathematical formula (III).

[0039]

[Equation 4]

(2) Water-soluble portion; 0.5 g of water-absorbent resin powder
Was dispersed in 1000 ml of deionized water, stirred for 12 hours and then filtered through filter paper, and the solid content of the filtrate was measured to obtain a water-soluble portion according to the following mathematical formula (IV).

[0041]

[Equation 5]

(3) Residual monomer; 0.5 g of water-absorbent resin powder
Was dispersed in 1000 ml of deionized water, stirred for 2 hours, filtered with a filter paper, and the amount of residual monomer in the filtrate was measured by high performance liquid chromatography. The amount of residual monomer in the water absorbent resin powder was determined from the measured value.

(4) Particle size distribution: According to JIS standard sieve.

(5) Moisture content: Determined from the weight loss when dried at 150 ° C. for 2 hours with a hot air dryer.

[0045]

Example 1 A stainless steel dual-arm kneader with a jacket and a lid having a sigma-type rotating arm and two two rotating shafts for constant-speed rotation was used as a reaction vessel. The radius of rotation of the rotating arm in this reaction vessel is constant.
3 mm, the gap when the rotating arm moves close to the inner wall of the reaction container within the reaction container is constant 1.5 mm, and the width and angle at which effective shearing is performed by moving the rotating arm while maintaining the gap is constant. 360 mm and 2.52 rad
And was used to carry out polymerization.

2957.6 g of partially neutralized acrylic acid, 75 mol% of which was neutralized with caustic soda, 1.54 g of methylenebisacrylamide and 4969 of water in the kneader.
An aqueous monomer solution consisting of g was charged, and nitrogen gas was blown into the reaction system to replace the inside of the reaction system with nitrogen.

Then, the two sigma-type rotating arms are set to 0.83r.
While rotating at a speed of ps and heating the jacket with warm water of 30 ° C., 33.4 g of a 12 wt% potassium persulfate aqueous solution and 33.4 g of a 0.5 wt% 1-ascorbic acid aqueous solution were added as polymerization initiators. Polymerization started 1 minute after the addition of the polymerization initiator. The hydrogel polymer produced as the polymerization proceeded was gradually subdivided by the rotation of the rotating arm.

The value of H defined by the formula (I) at the time of polymerization is
In the case of this kneader, it was given by the simplified formula (II) and was 0.041. 100 from the start of polymerization
After a minute, the lid was removed and the hydrogel polymer was taken out. The water content of the obtained water-containing gel polymer was 62% by weight.

The hydrogel polymer was dried under reduced pressure at 100 ° C. and 100 mmHg for 2 hours under reduced pressure with a stirrer to make the water content 20% by weight, and then 120 ° C.
It was dried with hot air for 1 hour. When the aggregate in the obtained dried product was lightly disentangled and the particle size distribution was measured, the amount of 4.7 mesh sieve product was 20% by weight based on the total amount.

The dried product was pulverized using a coffee mill until it was passed through a 20-mesh screen to obtain a water-absorbent resin powder. When the particle size distribution of the water-absorbent resin powder obtained was measured, the amount of fine powder passing through a 100-mesh sieve was 8% by weight. The water absorption capacity was 51 times, the water-soluble portion was 11% by weight, and the amount of residual monomer was 160 ppm.

[0051]

Example 2 The same as Example 1 except that 3.46 g of trimethylolpropane triacrylate was used in place of methylenebisacrylamide and the pressure in the reaction system was set to 100 mmHg at the same time as the initiation of polymerization. Polymerization (The value of H in the formula (I) at the time of polymerization is 0.04
1) I did. After 50 minutes from the start of the polymerization, the pressure inside the kneader was returned to normal pressure, and after aging for 50 minutes at normal pressure, the lid was removed and the hydrogel polymer was taken out. The water content of the obtained water-containing gel polymer was 60% by weight.

The hydrous gel polymer thus obtained was dried under reduced pressure at 80 ° C. and 100 mmHg for 2 hours in a vacuum dryer equipped with a stirrer to a water content of 24% by weight, and then 120
It was dried with hot air at ℃ for 1 hour. When the aggregate in the obtained dried product was lightly disentangled and the particle size distribution was measured, the amount of the 4.7 mesh sieve product was 16% by weight based on the total amount.

The dried product was pulverized using a coffee mill until it was passed through a 20-mesh sieve to obtain a water-absorbent resin powder. When the particle size distribution of the water-absorbent resin powder obtained was measured, the amount of fine powder passing through a 100-mesh sieve was 5% by weight. The water absorption capacity was 56 times, the water-soluble portion was 9.7% by weight, and the residual monomer amount was 170 ppm.

[0054]

Example 3 Polymerization was carried out in the same manner as in Example 1 except that the pressure in the reaction system was set to 100 mmHg at the same time as the initiation of polymerization (the value of H in the formula (I) at the time of polymerization was 0.041). did. 35 minutes after the start of polymerization, 14.8 g of sodium polyoxyethylene lauryl ether sulfate (surfactant Emar 20C manufactured by Kao) was added,
Further, the water content of the hydrogel polymer was removed under reduced pressure at 80 ° C. for 115 minutes. Then return the kneader system to normal pressure,
The lid was removed and the hydrogel polymer was taken out. The water content of the obtained water-containing gel polymer was 15% by weight. It was further dried with hot air at 120 ° C. for 1 hour. When the particle size distribution was measured by lightly disaggregating the aggregate in the obtained dried product,
The amount of the 4.7 mesh sieve product was 13% by weight based on the whole amount.

The dried product was crushed using a coffee mill until it was passed through a 20-mesh sieve to obtain a water-absorbent resin powder. When the particle size distribution of the water-absorbent resin powder obtained was measured, the amount of fine powder passing through a 100-mesh sieve was 4% by weight. The water absorption capacity was 55 times, the water-soluble portion was 9.0% by weight, and the residual monomer amount was 180 ppm.

[0056]

Example 4 Instead of the sigma type rotating arm in Example 1, polymerization was performed using a stainless steel double arm type kneader with a jacket having a Banbury type rotating arm and two rotating shafts rotating at constant speed. went. The radius of rotation of the rotating arm is constant at 73.5 mm, and the gap when the rotating arm moves close to the inner wall of the reaction container in the reaction container is also constant at 1.0 mm, which is effective because the rotating arm moves while maintaining this gap. The width and angle at which shearing is performed are constant at 420 mm and 3.
It was 14 rad.

Polymerization was conducted in the same manner as in Example 1 except that 3.46 g of trimethylolpropane triacrylate was used instead of methylenebisacrylamide as the crosslinking agent in Example 1. The number of rotations of the two rotating arms at the time of polymerization is 1 rps, and the value of H defined by the formula (I) is 0.1.
It was 3. A hydrogel polymer having a water content of 62% by weight was obtained, which was dried under reduced pressure at 100 ° C. and 100 mmHg for 3 hours under reduced pressure to a water content of 20% by weight, and then dried at 120 ° C. for 1 hour with hot air. did. The aggregate in the obtained dried product was lightly disentangled to measure the particle size distribution, which was 4.7.
The amount of the sieved mesh product was 15% by weight based on the whole amount.

The dried product was crushed using a coffee mill until it was passed through a 20-mesh screen to obtain a water-absorbent resin powder. When the particle size distribution of the water-absorbent resin powder obtained was measured, the amount of fine powder passing through a 100-mesh sieve was 7% by weight. Further, the water absorption capacity was 53 times, the water-soluble portion was 10% by weight, and the residual monomer amount was 150 ppm.

[0059]

Comparative Example 1 A stainless steel dual-arm kneader with a jacket and a lid having a sigma-type rotating arm and two rotating shafts for constant-speed rotation was used as a reaction vessel. The radius of rotation of the rotating arm in this reaction vessel is constant and is 3
6.5 mm, the gap when the rotating arm moves close to the inner wall of the reaction container in the reaction container is constant at 1.5 mm, and the width and angle at which effective shearing is performed by moving the rotating arm while maintaining the gap. Constantly 360mm and 2.52r respectively
It was ad, and it was used for the polymerization. A monomer aqueous solution consisting of 3922.8 g of partially neutralized acrylic acid having 75 mol% neutralized with caustic soda, 4.59 g of trimethylolpropane triacrylate and 6591 g of water was put into the kneader, and a nitrogen gas was blown into the reaction system. The inside was replaced with nitrogen.

Next, the two sigma type rotating arms are set to 0.17r.
While rotating at a speed of ps and heating the jacket with warm water of 30 ° C., 44.3 g of a 12 wt% potassium persulfate aqueous solution and 44.3 g of a 0.5 wt% 1-ascorbic acid aqueous solution were added as polymerization initiators. Polymerization started 1 minute after the addition of the polymerization initiator. The hydrogel polymer produced as the polymerization proceeded was gradually subdivided by the rotation of the rotating arm.

The value of H defined by the formula (I) at the time of polymerization is
It was 0.00016. 100 minutes after the polymerization started, the lid was removed and the hydrogel polymer was taken out. The water content of the obtained water-containing gel polymer was 63% by weight.

When the hydrogel polymer was dried with hot air at 150 ° C. for 2 hours, there was an undried portion. Therefore, it was further dried with hot air at 150 ° C. for 2 hours.

When the aggregate in the obtained dried product was lightly disentangled and the particle size distribution was measured, the amount of the 4.7 mesh sieve product was 77% by weight based on the total amount.

The dried product was pulverized using a coffee mill until it was passed through a 20-mesh screen to obtain a water-absorbent resin powder. The particle size distribution of the resulting water-absorbent resin powder was measured, and it was found that the amount of fine powder passing through a 100-mesh sieve was 18
% By weight. The water absorption capacity was 55 times, the water-soluble portion was 16% by weight, and the amount of residual monomer was 430 ppm.

[0065]

Comparative Example 2 A stainless steel dual-arm kneader with a jacket and a lid having a sigma-type rotating arm and two two rotating shafts for constant speed rotation was used as a reaction vessel. The radius of rotation of the rotating arm in this reaction vessel is constant 8
3 mm, the gap when the rotating arm moves close to the inner wall of the reaction container within the reaction container is constant 1.5 mm, and the width and angle at which effective shearing is performed by moving the rotating arm while maintaining the gap is constant. 360 mm and 2.52 rad
And was used to carry out polymerization.

A monomer aqueous solution containing 2957.6 g of partially neutralized acrylic acid 75 mol% of which was neutralized with caustic soda, 3.46 g of trimethylolpropane triacrylate and 4969 g of water was charged into the kneader, and nitrogen gas was added. The inside of the blowing reaction system was replaced with nitrogen.

Next, the two sigma type rotating arms are set to 4.17r.
While rotating at a speed of ps and heating the jacket with warm water of 30 ° C., 33.4 g of a 12 wt% potassium persulfate aqueous solution and 33.4 g of a 0.5 wt% 1-ascorbic acid aqueous solution were added as polymerization initiators. Polymerization started 1 minute after the addition of the polymerization initiator. The hydrous gel polymer produced as the polymerization proceeded was not subdivided by the rotation of the rotary arm, but was wrapped around the rotary arm in a roll shape, then boiled and was separated from the rotary arm and was slightly subdivided.

The value of H defined by the formula (I) at the time of polymerization is
It was 1.5. 100 minutes after the polymerization started, the lid was removed and the hydrogel polymer was taken out. The water content of the obtained water-containing gel polymer was 63% by weight.

The hydrous gel polymer thus obtained was dried under reduced pressure at 100 ° C. and 100 mmHg for 2 hours in a reduced pressure dryer equipped with a stirrer.
After drying for 13 hours to obtain a water content of 13% by weight, another 12
It was dried with hot air at 0 ° C. for 1 hour. Most of the obtained dried products were large lumps, and the particle size distribution was measured.
The amount of the 7 mesh sieve product was 100% by weight based on the total amount.

This dried product was pulverized by using a table pulverizer until all passed through a 20-mesh sieve to obtain a water-absorbent resin powder. When the particle size distribution of the resulting water absorbent resin powder was measured, the amount of fine powder passing through a 100 mesh sieve was 28% by weight. The water absorption capacity was 56 times, the water-soluble portion was 18% by weight, and the residual monomer amount was 380 ppm.

[0071]

According to the method of the present invention, since the obtained hydrophilic polymer has very few coarse particles and a small particle size, it is easy or unnecessary to grind, and the load of grinding is small. Occurrence is extremely low. Further, when the hydrophilic polymer is a water-absorbent resin, a polymer having a small amount of residual monomers and water-soluble parts and a high water-absorbing ability can be easily obtained by the method of the present invention.

[Brief description of drawings]

FIG. 1 is an explanatory view showing the structure of a double-arm kneader that is preferably used as a reaction container in the present invention, and (A) is a perspective view of an inner rotating arm seen from the front,
(B) is a perspective view of the rotation locus of the tip of the rotating arm seen from the side.

[Explanation of sign]

 1 inner wall of reaction vessel not orthogonal to the rotation axis 2 rotation axis 3 rotation arm 4 rotation trajectory of rotation arm 5 inner wall of reaction vessel with rotation axis L width of tip of rotation arm C gap between tip of rotation arm and reaction vessel inner wall φ Angle at which effective shear force occurs

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Nobuyuki Harada 5-8 Nishimitabicho Suita City, Osaka Prefecture Central Research Institute of Nihon Shokubai Co., Ltd. (72) Innovator Tadao Shimomura 5-8 Nishimitabicho Suita City, Osaka Prefecture Central Research Institute of Nippon Shokubai Co., Ltd. (72) Inventor Kunihiko Ishizaki 1 of 992 Nishioki, Nishihama, Aboshi-ku, Himeji City, Hyogo Prefecture

Claims (3)

[Claims] 1. An aqueous solution of a water-soluble ethylenically unsaturated monomer, which becomes a hydrogel polymer by polymerization, and a polymerizable monomer, which contains a crosslinking agent, is polymerized in a reaction vessel having a rotating arm or a stirring blade. In the method of polymerizing the water-containing gel-like polymer produced with the progress of the step (3) while subdividing by a shearing force generated by the rotation of the rotating arm or the stirring blade, the following numerical formula (I)
After polymerizing under a shearing condition in which the H value defined in 1. is in the range of 0.0005 to 1.0, the water content of the hydrogel polymer is 40 to 70% by weight at a temperature of 60 to 120 ° C. under reduced pressure. To 10 to 35% by weight, the method for producing a hydrophilic polymer. [Equation 1] 2. The method for producing a hydrophilic polymer according to claim 1, wherein the aqueous solution of the monomer is polymerized under reduced pressure. 3. The method for producing a hydrophilic polymer according to claim 1, wherein the aqueous solution of the monomer is polymerized in the presence of hydrophilic fibers.