JP5544706B2 - UNSATURATED CARBOXYLIC ACID CROSSLINKED POLYMER AND METHOD FOR PRODUCING THE POLYMER - Google Patents

Description

The present invention relates to an unsaturated carboxylic acid polymer widely used as a water-soluble thickener and a method for producing the same.
More specifically, the present invention relates to an unsaturated carboxylic acid-based crosslinked polymer in which the polymer has a crosslinked structure and is water-soluble, and a method for producing the same, and relates to a technique for producing an unsaturated carboxylic acid-based polymer. .

Unsaturated carboxylic acid polymers such as acrylic acid are used as a thickener for paints, adhesives, and sealants by utilizing the properties of their aqueous solutions, that is, their viscosity and ionicity. It is used in various fields as an anti-settling agent and a dispersion stabilizer for metal powder of dry batteries.
In particular, unsaturated carboxylic acid polymers having a crosslinked structure and water-soluble, which are obtained in the form of a powder in precipitation polymerization in a water-soluble organic solvent, have characteristics in their unique viscosity, that is, thixotropic properties. It is especially used in cosmetics such as creams, lotions, toothpastes, and shampoos.

The applicant has been developing the precipitation polymerization for a long time, and has made various proposals regarding the technology.
For example, JP-A-52-127993 (hereinafter referred to as Patent Document 1) proposes a method for producing a water-soluble polycarboxylic acid in which a sodium acrylate aqueous solution is polymerized in a water-soluble organic solvent.
Specifically, the problem that the polymer is in the form of a bowl and adheres to the reactor wall, or a polymer having a high water content and a large amount of insoluble matter is obtained, is the α, β-unsaturated carboxylic acid or this. This is a technique in which a mixed monomer with other copolymerizable vinyl compound mainly composed of is sequentially introduced and polymerized, and at the same time, a neutralization reaction is carried out during the polymerization by successive introduction of alkali.

Japanese Patent Laid-Open No. 55-48212 (hereinafter referred to as Patent Document 2) proposes a novel method for producing a water-soluble crosslinked copolymer in which acrylic acid, acrylic acid and a crosslinking agent are added and polymerized.
This proposal is based on the problem that only a low-viscosity product or water-insoluble material can be obtained. By using 0.5 to 15% by weight of a monomer having two or more vinyl groups as a crosslinking agent, The present invention relates to a technique for easily and economically advantageously producing a water-soluble crosslinked polymer with a small amount of insoluble matter and a viscosity reduction even with an alkali as a powder or an aqueous solution.
JP-A-52-127993 (Claims) JP-A-55-48212 (Claims)

The water-soluble crosslinked polymer has been widely used by utilizing its viscosity characteristics, that is, thixotropic properties.
As the range of use expands, there is a strong demand for improving the quality of water-soluble crosslinked polymers.
In particular,
1) More thickening effect;
For example, the Brookfield viscosity of a 0.25 mass% aqueous solution at pH 6-8 is 5,000 mPa · s or more, and the Brookfield viscosity of a 0.5 mass% aqueous solution is 10,000 mPa · s or more.
2) Clarity when made into an aqueous solution (transparency);
For example, the transmittance (420 nm) of a 0.5 mass% aqueous solution is 80% or more.
3) Less residual unreacted monomer or organic solvent;
For example, 5000 ppm or less, or 1000 ppm or less.
4) Even when stored for a long time, the viscosity of the aqueous solution is small.
Improvement of the characteristics is strongly desired.

Said 1)-4) are the characteristics calculated | required by the water-soluble crosslinked polymer.
Naturally, a method for producing a water-soluble crosslinked polymer having such characteristics should be free from the following disadvantages, which have been a problem in the past.

That is, during the precipitation of the polymer, polymer agglomeration is generated, and the produced agglomerate adheres to the wall of the reaction kettle and the stirring blade, thereby increasing the slurry viscosity of the reaction mixture and increasing the particle size of the product powder. In some cases, it cannot be pulverized as a lump.
Furthermore, the amount of unreacted monomer increases due to the decrease in heat conduction due to the deposit, the quality varies due to overheating in the deposit region, and the yield decreases.
Furthermore, the problem of operational safety during production such as bumping of the solvent due to disproportionation of heat conduction due to adhesion of the aggregates to the wall of the reaction kettle or the stirring blade is solved. Is Rukoto.

  In view of the present situation, an object of the present invention is to safely manufacture and provide a water-soluble crosslinked polymer having improved quality, which has been widely demanded.

The inventors have intensively studied to achieve the above object, and found that the object can be achieved by using a specific crosslinking agent in combination, and have completed the present invention.

That is, the invention according to claim 1 of the present invention is
Unsaturated carboxylic acid monomer
A crosslinking agent (A) selected from allyl acrylate, allyl methacrylate, ethylene glycol diacrylate, polyethylene glycol diacrylate, ethylene glycol dimethacrylate, polyethylene glycol dimethacrylate ;
In the presence of polyvalent allyl ether from the selected cross-linking agent (B), generated by precipitation polymerization in a water-soluble organic solvent, an unsaturated carboxylic acid-based cross-linked polymer powder, which is a water-soluble . It is.

The invention according to claim 2 of the present invention is
In the unsaturated carboxylic acid-based crosslinked polymer powder according to claim 1,
The composition ratio of the crosslinking agent (A) and the crosslinking agent (B)
The mass ratio is 1: 0.5 to 1:20.

The invention according to claim 3 of the present invention is
In the unsaturated carboxylic acid-based crosslinked polymer powder according to claim 1 or 2 ,
The unsaturated carboxylic acid monomer is
It is composed of an olefinically unsaturated carboxylic acid having 3 to 5 carbon atoms or a salt thereof and a monomer capable of copolymerization of 30% by mass or less.

The invention according to claim 4 of the present invention is
In the unsaturated carboxylic acid-based crosslinked polymer powder according to claim 3,
The olefinically unsaturated carboxylic acid or salt thereof is
20 to 100 mol% thereof is a salt of an olefinic unsaturated carboxylic acid.

The invention according to claim 5 of the present invention is
In the unsaturated carboxylic acid-based crosslinked polymer powder according to any one of claims 1 to 4,
The unsaturated carboxylic acid-based crosslinked polymer is
The transmittance (420 nm) of a 0.5 mass% aqueous solution at pH 6-8 is 80% or more,
Brookfield viscosity of 0.25 mass% aqueous solution at pH 6-8 is 5,000 mPa · s or more,
The Brookfield viscosity of the 0.5% by mass aqueous solution is 10,000 mPa · s or more.

Furthermore, the invention according to claim 6 of the present invention is
Unsaturated carboxylic acid monomer
A crosslinking agent (A) selected from allyl acrylate, allyl methacrylate, ethylene glycol diacrylate, polyethylene glycol diacrylate, ethylene glycol dimethacrylate, polyethylene glycol dimethacrylate ;
The coexistence of a polyvalent allyl ether selected from the crosslinker (B), water-soluble organic solvent, is polymerized using a radical polymerization initiator,
It is a method for producing an unsaturated carboxylic acid-based crosslinked polymer, wherein the obtained water-soluble polymer is obtained in a powder state.

The invention according to claim 7 of the present invention is
In the manufacturing method of the unsaturated carboxylic acid type crosslinked polymer of Claim 6,
The water-soluble organic solvent is
It is characterized by being methanol, ethanol, isopropanol, acetone or methyl ethyl ketone.

The invention according to claim 8 of the present invention provides
In the manufacturing method of the unsaturated carboxylic acid type crosslinked polymer of Claim 6 or 7,
The amount of the radical polymerization initiator used is
The amount is 0.10 parts by mass or less per 100 parts by mass of the monomer.

The unsaturated carboxylic acid-based crosslinked polymer of the present invention has the following quality and characteristics.
1) Excellent thickening effect that the Brookfield viscosity of a 0.25 mass% aqueous solution at pH 6 to 8 is 5,000 mPa · s or more and the Brookfield viscosity of a 0.5 mass% aqueous solution is 10,000 mPa · s or more. Have.
2) An aqueous solution excellent in clarity (transparency) in which the transmittance (420 nm) of a 0.5 mass% aqueous solution is 80% or more can be prepared.
3) The remaining unreacted monomer and organic solvent are as low as 5000 ppm or less, and further 1000 ppm or less.
4) There is little decrease in the viscosity of the aqueous solution even during long-term storage.
5) Both the mixed solvent and the single solvent system have little variation in quality and can be operated safely.
In addition, the method for producing an unsaturated carboxylic acid-based crosslinked polymer of the present invention is a commercially effective method that can be operated with a single solvent and the management of the recovered solvent is simplified.

The monomer constituting the unsaturated carboxylic acid-based crosslinked polymer in this invention is mainly composed of an unsaturated carboxylic acid-based monomer.
Examples of the unsaturated carboxylic acid monomer include olefinic unsaturated carboxylic acids having 3 to 5 carbon atoms and salts thereof as preferred for the present invention.

Examples of the carboxylic acid include acrylic acid, methacrylic acid, maleic acid, itaconic acid, crotonic acid and the like.
Such salts include sodium, potassium, ammonium salts and the like.
Among these, acrylic acid and its sodium salt are particularly preferable because of their good performance as a thickener for the resulting polymer, and acrylic acid is more preferable because it is easily available from the market.

  As a monomer constituting the unsaturated carboxylic acid-based crosslinked polymer, a monomer that can be copolymerized with the unsaturated carboxylic acid-based monomer described above is used together with the unsaturated carboxylic acid-based monomer.

Examples of the monomer that can be copolymerized with the unsaturated carboxylic acid monomer include monomers that are generally widely used.
Specifically, for example, styrene, alkyl vinyl ether, vinylidene chloride, acrylic acid esters, methacrylic acid esters, acrylamides, methacrylamides, N-vinylformamide, N-vinylacetamide, vinyl acetate, vinylpyrrolidone, acrylonitrile Methacrylonitrile and the like.

  Specific examples of the acrylic esters and methacrylic esters include esters such as methyl, ethyl, butyl, isobutyl and octyl, and esters having an ether bond such as 2-methoxyethyl acrylate and 2-ethoxyethyl acrylate. , Hydroxy group-containing esters such as 2-hydroxyethyl acrylate and 2-hydroxypropyl methacrylate.

  Specific examples of the acrylamides and methacrylamides include acrylamide, methacrylamide, dimethylacrylamide, diethylacrylamide, dimethylaminopropylacrylamide, isopropylacrylamide and the like.

  Furthermore, as monomers constituting the unsaturated carboxylic acid-based crosslinked polymer, macromonomers such as terminal methacrylate polymethyl methacrylate, terminal styryl polymethyl methacrylate, terminal methacrylate polystyrene, terminal methacrylate polyethylene glycol, terminal methacrylate acrylonitrile styrene copolymer, etc. Kinds can also be used.

Similarly, maleic acid, fumaric acid, itaconic acid, and esters thereof can be used.
Furthermore, if necessary, trimethoxyvinylsilane, triethoxyvinylsilane, γ-methacryloxypropyltrimethoxysilane, and the like can be used.

The amount of the monomer that can be copolymerized with the unsaturated carboxylic acid monomer is determined according to the characteristics required for the unsaturated carboxylic acid crosslinked polymer.
Usually, it is used at 30% by mass or less in the monomer constituting the unsaturated carboxylic acid-based crosslinked polymer.
When the amount is exceeded, problems such as impaired water solubility and difficulty in obtaining a product having a high viscosity may occur.

In order to achieve the object of the present invention, it is preferable that 20 to 100 mol% of the monomer constituting the unsaturated carboxylic acid-based crosslinked polymer is a salt of unsaturated carboxylic acid, and the amount thereof is 40 to 95 mol. % Is more preferable.
If the salt of the unsaturated carboxylic acid is small, the polymer precipitated in the water-soluble organic solvent tends to aggregate, which causes various problems in production, and tends to be agglomerated. It becomes difficult to obtain.

In the present invention, the following two kinds of cross-linking agents are used in combination, and by using these two kinds of cross-linking agents in combination, the above-described effects are produced .
(A) A crosslinking agent selected from a polyvalent vinyl ester, a polyvalent allyl ester and a polyvalent vinyl amide.
( B ) A crosslinking agent selected from polyvalent allyl ethers .

Specific examples of these crosslinking agents include the following.
( A )
Examples include allyl acrylate, allyl methacrylate , diallyl phthalate , ethylene glycol diacrylate, polyethylene glycol diacrylate, ethylene glycol dimethacrylate, and polyethylene glycol dimethacrylate.
In the present invention, allyl acrylate, allyl methacrylate, ethylene glycol diacrylate, polyethylene glycol diacrylate, ethylene glycol dimethacrylate, and polyethylene glycol dimethacrylate are selected.

In addition, ( B )
Tetraallyloxyethane, pentaerythritol tetraallyl ether, pentaerythritol triallyl ether, pentaerythritol diallyl ether, allyl saccharose, trimethylolpropane diallyl ether, trimethylolpropane triallyl ether, ethylene glycol diallyl ether, glyceryl diallyl ether, glyceryl triallyl Ether and the like .

In this invention, the combined ratio of the crosslinking agent ( A ) and ( B ) depends on the thickening properties of the target water-soluble crosslinked copolymer, but ( A ) :( B ) = 1: 0.5-1 : 20 is preferable.
A ratio of 1: 1 to 1:10 is more preferable, and a ratio of 1: 2 to 1: 8 is particularly preferable .

When the amount ( A ) is large in this combined ratio, the heat resistance of the thickened aqueous solution is inferior, the stability to ultraviolet light is inferior, and the viscosity is liable to decrease particularly in the alkali region.
On the contrary, when there is much ( B ), the transparency of the thickened aqueous solution is inferior, and it becomes easy to become low viscosity.

Moreover, the usage-amount of the said crosslinkable monomer is 0.1-2.0 mass parts with respect to 100 mass parts of monomers with the total amount of ( A ) and ( B ).
More preferably, it is 0.2-1.5 mass parts. Particularly preferred is 0.3 to 1.2 parts by mass.
If the amount used is less than 0.1 parts by mass, the dissolved aqueous solution will not be thickened and will tend to be in a stringing state.

  In the present invention, the unsaturated carboxylic acid-based crosslinked polymer is produced by precipitation polymerization using a water-soluble organic solvent as a medium.

As the water-soluble organic solvent used, a solvent that dissolves the monomer but does not dissolve the polymer is used.
Specific solvents include those shown by the prior art described above, but are ketones, esters, alcohols, aliphatic hydrocarbons having 4 to 12 carbon atoms, and aromatic hydrocarbons having 6 to 8 carbon atoms. And a solvent composed of at least one selected from the group consisting of:

From the viewpoint of reuse of the recovered solvent, a single solvent is preferable, and methanol, ethanol, and isopropanol are preferably used from the market availability.
In particular, methanol with less chain transfer is preferable, and a polymer with a long polymer chain is obtained by having less chain transfer, and it is easy to achieve high viscosity.
Also, ketones such as acetone and methyl ethyl ketone are generally preferable for obtaining a high molecular weight polymer because of less chain transfer.

In the present invention, a radical initiator is preferably used for polymerization of the unsaturated carboxylic acid monomer, and one or a mixture of two or more selected from radical initiators such as peroxides and azos. Can be used.
The amount used is preferably 0.001 to 0.10 parts by mass, and more preferably 0.002 to 0.05 parts by mass with respect to 100 parts by mass of the monomer.

When there are few radical initiators, a polymerization reaction does not advance and therefore a polymer powder cannot be obtained.
Even if the polymerization reaction starts, the yield is poor and problems occur in the drying process, and drying cannot be performed sufficiently, and a large amount of unreacted monomer remains in the powder product, and the product value is not likely to occur. .

When there are many radical initiators, superposition | polymerization advances rapidly and it is easy to control a polymerization reaction, and the situation which cannot be controlled may arise depending on the case.
Even if the polymerization reaction can be controlled, since the polymer chain is shortened, the viscosity of the thickened aqueous solution tends to be low.
These radical initiators are preferably used in the range that can be dissolved in the water-soluble organic solvent by examining the combination of the amount used and the solvent used.

Specific examples of the radical initiator include benzoyl peroxide, lauroyl peroxide, t-butyl hydroperoxide, and di (2-ethylhexyl) peroxydicarbonate as peroxides.
Examples of the azo group include 2,2′-azobisisobutyronitrile, 4,4′-azobis-4-cyanovaleric acid, 2,2′-azobis (2-amidinopropane) dihydrochloride, and the like.

  As described above, as described above, 20 to 100 mol% of the monomer is an unsaturated carboxylic acid salt, and further the amount is 40 to 95 mol%. In addition, polymerization can be carried out satisfactorily and a polymer can be obtained by polymerization in which the polymerization initiator is dividedly added or polymerization in which the monomer and the polymerization initiator are continuously added.

In addition, in the polymerization, the produced polymer does not aggregate and adhere to the wall of the reaction vessel or the stirring blade, and the slurry viscosity of the reaction mixture does not become very high.
In addition, the particle size of the product powder is increased, the polymer is agglomerated and cannot be pulverized, the amount of unreacted monomer increases due to reduced heat conduction due to deposits, quality variation due to overheating in the deposit area, and yield It does not cause problems such as lowering, nor does it cause operational safety problems such as solvent boiling due to disproportionated heat conduction.

The polymerization method in the present invention is preferably carried out at a polymerization temperature of 50 ° C. or higher and a boiling point temperature under atmospheric pressure of the solvent system to be used.
When the polymerization temperature is less than 50 ° C., decomposition of the radical initiator does not proceed and it is difficult to improve the yield.

In general, the polymerization is preferably performed while the solvent system used is refluxed.
At that time, by applying some pressure reduction, the reflux temperature of the solvent can be lowered, and the bumping of the solvent due to the generation of polymer aggregates can be more effectively suppressed.

Of course, the polymerization is possible even under self-pressurization in a closed container or under forced pressurization, but it is not preferable because the solvent easily bumps easily.

Hereinafter, the unsaturated carboxylic acid-based crosslinked polymer of the present invention and the method for producing the polymer will be described in more detail based on examples.
The characteristics of the polymer were evaluated by the following method.

<Brookfield viscosity>
The 0.2 wt% and 0.5 wt% aqueous solution viscosities were quickly confirmed by confirming that the polymer powder was completely dissolved in ion-exchanged water, and then held in a thermostatic bath at a temperature of 25 ° C for 1 hour or more. It was measured with a type viscometer.
The following rotor numbers and rotational speeds were used.
0 to 2,000 mPa · s: H3 rotor, 20 rpm
2,000 to 10,000 mPa · s: H5 rotor, 20 rpm
10,000 mPa · s or more: H6 rotor, 20 rpm

<Transmissivity (420 nm and 600 nm)>
Using an aqueous solution obtained by dissolving 0.5% by mass of polymer powder in ion-exchanged water, transmittance was measured at wavelengths of 420 nm and 600 nm with a spectrophotometer UV-1650PC manufactured by Shimadzu Corporation.
As a control liquid, ion-exchanged water used for dissolving the polymer powder was used.

<Example 1>
A 1 L flask was charged with 290 g of methanol, 100 g of acrylic acid, 0.20 g of allyl methacrylate and 1.10 g of trimethylolpropane diallyl ether (Neoallyl T-20 <manufactured by Daiso Corporation>), and 18 g of caustic soda flakes. And 9 g of ion exchange water was slowly added so that the internal temperature was kept at 40 ° C. or lower.
The temperature of the 1 L flask was raised while sufficiently substituting with nitrogen, and when the internal temperature was maintained at 68 ° C., 0.008 g of initiator ACVA (4,4′-azobiscyanovaleric acid) was added.
The polymerization was continued by controlling the external temperature so that the reflux of the solvent was not cured for 8 hours from the start of the reaction when the reaction solution became cloudy.
Thereafter, the internal temperature was cooled to a temperature of 30 ° C., and 33 g of caustic soda flakes was slowly added so that the internal temperature did not exceed 50 ° C.
The reaction slurry was filtered and washed and then vacuum dried at a temperature of 100 ° C. for 6 hours to obtain a polymer powder.

<Examples 2-18 and Comparative Examples 1-8>
Under the conditions shown in Tables 1, 2 and 3, a polymer powder was obtained in the same manner as in Example 1.
However, in Example 6, a part of the monomer was continuously added and polymerized as follows.
A 1 L flask was charged with 250 g of methanol, 70 g of acrylic acid, 0.09 g of allyl methacrylate and 0.47 g of pentaerythritol triallyl ether (Neoallyl P-30M <manufactured by Daiso Corporation>), and 8 g of caustic soda. Flakes and 15 g of ion exchange water were slowly added so that the internal temperature was kept at a temperature of 40 ° C. or lower.
Separately, 30 g of acrylic acid and 0.08 g of allyl methacrylate were mixed in a 100 ml beaker, and 21 g of 48 mass% NaOH aqueous solution was prepared in a 50 ml beaker.
When the temperature of the 1 L flask was sufficiently increased while purging with nitrogen and the internal temperature was maintained at 68 ° C., 0.005 g of initiator ABAH was added.
The reaction was started when the reaction solution became cloudy, and 10 minutes later, the previously prepared monomer solution and NaOH aqueous solution were continuously added from separate ports over 2.5 hours.
Polymerization was continued by controlling the external temperature so that the reflux of the solvent was not cured for 6 hours after the completion of the addition.
Thereafter, the internal temperature was cooled to a temperature of 30 ° C., and 33 g of caustic soda flakes was slowly added so that the internal temperature did not exceed 50 ° C.
The reaction slurry was filtered and washed and then vacuum dried at a temperature of 100 ° C. for 6 hours to obtain a polymer powder.

The characteristics of the polymer powders obtained in Examples 1 to 18 and Comparative Examples 1 to 8 were measured by the evaluation method and are shown in Tables 1, 2 and 3.
In addition, the symbol in a table | surface shows the following.
ATBS: 2-acryloylamino-2-methylpropanesulfonic acid AMA: allyl methacrylate Neolyl T-20 <manufactured by Daiso Corporation>: trimethylolpropane diallyl ether Neoallyl T-30M <manufactured by Daiso Corporation>: Pentaerythritol tri Allyl ether TAE: Tetraallyloxyethane TAIC: Triallyl isocyanurate ACVA: 4,4′-azobiscyanovaleric acid ABAH: 2,2′-azobis (2-amidinopropane) dihydrochloride AIBN: 2,2′-azobis Isobutyronitrile AVDN: 2,2′-azobis-2,4-dimethylvaleronitrile

The unsaturated carboxylic acid-based crosslinked polymer of the present invention is water-soluble, has thixotropic properties, and can impart high viscosity.
Therefore, in addition to being in powder form, it has the potential to be widely used in the cosmetics industry such as creams, lotions, toothpastes, shampoos, and other industries such as paints, adhesives, and sealing agents. As a result, it is widely used in the chemical industry for producing polymers.

Claims (8)

Unsaturated carboxylic acid monomer
A crosslinking agent (A) selected from allyl acrylate, allyl methacrylate, ethylene glycol diacrylate, polyethylene glycol diacrylate, ethylene glycol dimethacrylate, polyethylene glycol dimethacrylate ;
In the presence of polyvalent allyl ether from the selected cross-linking agent (B), generated by precipitation polymerization in a water-soluble organic solvent, an unsaturated carboxylic acid-based cross-linked polymer powder, which is a water-soluble . The composition ratio of the crosslinking agent (A) and the crosslinking agent (B)
The unsaturated carboxylic acid-based crosslinked polymer powder according to claim 1, wherein the weight ratio is 1: 0.5 to 1:20. The unsaturated carboxylic acid monomer is
The olefinic unsaturated carboxylic acid having 3 to 5 carbon atoms or a salt thereof and a monomer capable of copolymerization of 30% by mass or less, and the copolymerized monomer. Unsaturated carboxylic acid-based crosslinked polymer powder . The olefinically unsaturated carboxylic acid or salt thereof is
The unsaturated carboxylic acid-based crosslinked polymer powder according to claim 3, wherein 20 to 100 mol% thereof is a salt of an olefinically unsaturated carboxylic acid. The unsaturated carboxylic acid-based crosslinked polymer is
The transmittance (420 nm) of a 0.5 mass% aqueous solution at pH 6-8 is 80% or more,
Brookfield viscosity of 0.25 mass% aqueous solution at pH 6-8 is 5,000 mPa · s or more,
The unsaturated carboxylic acid-based crosslinked polymer powder according to any one of claims 1 to 4, wherein the 0.5 mass% aqueous solution has a Brookfield viscosity of 10,000 mPa · s or more. Unsaturated carboxylic acid monomer
A crosslinking agent (A) selected from allyl acrylate, allyl methacrylate, ethylene glycol diacrylate, polyethylene glycol diacrylate, ethylene glycol dimethacrylate, polyethylene glycol dimethacrylate ;
The coexistence of a polyvalent allyl ether selected from the crosslinker (B), water-soluble organic solvent, is polymerized using a radical polymerization initiator,
A method for producing an unsaturated carboxylic acid-based crosslinked polymer, wherein the obtained water-soluble polymer is obtained in a powder state. The water-soluble organic solvent is
It is methanol, ethanol, isopropanol, acetone, or methyl ethyl ketone, The manufacturing method of the unsaturated carboxylic acid type crosslinked polymer of Claim 6 characterized by the above-mentioned. The amount of the radical polymerization initiator used is
The method for producing an unsaturated carboxylic acid-based crosslinked polymer according to claim 6 or 7, wherein the amount is 0.10 parts by mass or less per 100 parts by mass of the monomer.