JPH06263803A - Production and use of water-soluble (meth)acrylic acid polymer - Google Patents

Abstract

PURPOSE:To provide a method for industrially easily producing a water-soluble (meth)acrylic acid polymer with high purity. CONSTITUTION:A water-soluble (meth)acrylic acid monomer, a polymerization initiator, and hypophosphorous acid (salt) are gradually introduced into an aqueous medium to polymerize the monomer by solution polymerization. The monomer is introduced in such an amount that the polymer concentration in the reaction mixture after polymerization will be 38-72wt.% in terms of the amount of the monomer converted to the polymer. The polymer thus obtained has far higher performance than conventional ones when used as a so-called water-treating agent such as a scale inhibitor or corrosion inhibitor and as a dispersant for inorganic pigments.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a (meth) acrylic acid-based water-soluble polymer and uses of the (meth) acrylic acid-based water-soluble polymer obtained by the production method.

[0002]

2. Description of the Related Art Many methods have been conventionally proposed as a method for producing a (meth) acrylic acid-based water-soluble polymer. Many proposals have been made for a method for producing a (meth) acrylic acid-based water-soluble polymer in the presence of hypophosphorous acid (salt). For example US
No. 2,789,099, JP-A-50-15881, and JP-A-55-127413 disclose the production method. In addition, many applications of (meth) acrylic acid-based water-soluble polymers obtained in the presence of hypophosphorous acid (salt) have been proposed.

For example, JP-A-51-76184, JP-A-55-11092, JP-A-55-14900, JP-A-59-193909, and JP-A-60-174793.
JP-A-61-220794, JP-A-61-293
599, JP-A-62-207888, JP-A-62-
No. 214186 discloses the use as a scale inhibitor or a corrosion inhibitor. However, in the above-mentioned conventional production method, since a large amount of hypophosphorous acid (salt) and / or its modified product remains in the product, only a low-purity water-soluble polymer can be obtained.

Further, the production method in which copper is used in combination as a polymerization catalyst is anxious in terms of toxicity since copper remains in the final product.

Further, in these conventional production methods, the efficiency of hypophosphorous acid (salt) is low, and it is necessary to use a large amount of expensive hypophosphorous acid (salt). Therefore, it is necessary to produce a low-cost water-soluble polymer. There was a limit.

Further, since the conventional manufacturing method carries out the polymerization at a relatively low concentration, it is necessary to evaporate the solvent in order to obtain a high-concentration water-soluble polymer solution. I couldn't get it. In addition, the water-soluble polymers obtained by these conventional production methods are not sufficient in the scale-inhibiting ability and the corrosion-inhibiting ability, and improvement has been desired.

[0007]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems that conventional production methods have in obtaining a (meth) acrylic acid-based water-soluble polymer in the presence of hypophosphorous acid (salt). To do. Further, it is intended to eliminate the insufficient performance of the conventional (meth) acrylic acid-based water-soluble polymer obtained in the presence of hypophosphorous acid (salt).

[0008]

Means and Actions for Solving the Problems In the present invention, a monomer-converted concentration of a polymer in a liquid after polymerization is 38 in an aqueous medium.
(Meth) acrylic acid-based water-soluble aqueous solution characterized by successively introducing (meth) acrylic acid-based monomer, polymerization initiator and hypophosphorous acid (salt) necessary to reach ~ 72 wt% The present invention relates to a method for producing a water-soluble polymer, and use of the (meth) acrylic acid-based water-soluble polymer obtained by the production method as an inorganic pigment dispersant, a scale inhibitor, and a metal corrosion inhibitor.

In the present invention, the (meth) acrylic acid type monomer, the polymerization initiator and the hypophosphorous acid (salt) (hereinafter referred to as an additive component) are successively introduced into the aqueous medium.

When any one or all of the added components is initially charged, the (meth) acrylic acid water-soluble polymer as in the present invention cannot be obtained.

The additive components are introduced into the aqueous medium independently or as a mixture. When the additive component is a solid, it can be introduced as it is, or it can be introduced by dissolving it in water or an organic solvent such as alcohol or ketone.

As the method of successive introduction, it is also possible to introduce the added components continuously or in a divided manner.

The (meth) acrylic acid type monomer used in the present invention includes acrylic acid, methacrylic acid, acrylic acid salt and methacrylic acid salt in an amount of 50 wt% or more, preferably 70 w.
It means a polymerizable monomer containing t% or more. Examples of the (meth) acrylic acid salt include alkali metal salts of (meth) acrylic acid such as sodium, potassium, and lithium; alkaline such as ammonia, monomethylamine, dimethylamine, trimethylamine, diethylamine, monoethanolamine, diethanolamine, and triethanolamine. Examples thereof include inorganic or organic ammonium salts obtained by neutralizing with a substance. Of these, use of acrylic acid is particularly preferable. The polymerization initiator is not particularly limited, and various kinds of catalysts can be used. For example, persulfates such as sodium persulfate and potassium persulfate; hydrogen peroxide, water-soluble azo such as 2,2′-azobis (2-amidinopropane) hydrochloride and 4,4′-azobis-4-cyanovaleric acid. Compounds: Organic peroxides such as benzoyl peroxide, lauroyl peroxide and peracetic acid; Oil-soluble azo such as azobisisobutyronitrile and 2,2'-azobis (4-methoxy-2,4-dimethylvaleronitrile) Compounds and the like are used, but among them, persulfate which is inexpensive and has high initiator efficiency is particularly preferable. These polymerization initiators are preferably used in an amount of 0.001 to 0.1 mol based on 1 mol of the (meth) acrylic acid water-soluble monomer.

As hypophosphorous acid (salt), hypophosphorous acid,
Alkali metal salts of sodium, potassium, lithium, etc. of hypophosphite; obtained by neutralizing with alkaline substances such as ammonia, monomethylamine, dimethylamine, trimethylamine, diethylamine, monoethanolamine, diethanolamine, triethanolamine Other examples include inorganic or organic ammonium salts. Of these, sodium hypophosphite is particularly preferable because it is inexpensive and industrially available. These hypophosphorous acid (salt) is 0.0 per 1 mol of (meth) acrylic acid-based water-soluble monomer.
It is preferable to use 1 to 0.5 molar amount. In the present invention, the addition components are successively introduced into an aqueous medium for polymerization. The aqueous catalyst means water or a mixed solvent of water and an inorganic or organic solvent soluble in water. The use of an inorganic or organic solvent is useful for controlling the molecular weight, but these solvents must be removed in order to obtain the final product. Therefore, it is preferable not to use them except in special cases.

In the present invention, it is necessary that the monomer-converted concentration of the polymer in the liquid after polymerization is 38 to 72% by weight.
It is preferably 40 to 60% by weight. Even if the reaction is carried out at a low monomer conversion concentration of less than 38% by weight, a high-purity, low-cost and highly safe (meth) acrylic acid-based water-soluble polymer as in the present invention cannot be obtained.

Even when the reaction is carried out at a low monomer conversion concentration of less than 38% by weight, the inorganic pigment dispersant, the scale inhibitor and the metal corrosion inhibitor can be remarkably excellent as in the present invention ( A meth) acrylic acid-based water-soluble polymer cannot be obtained. When the monomer is produced at a high monomer conversion concentration of more than 72% by weight, the viscosity of the polymerization system becomes extremely high, which makes production substantially difficult. In the present invention, the converted concentration of the polymer monomer in the liquid after polymerization is expressed by weight% of the polymerized (meth) acrylic acid-based water-soluble monomer content in the liquid at the time when the polymerization is substantially completed. It is a thing. Further, as long as the effect of the invention is not impaired, at least one of the (meth) acrylic acid-based water-soluble monomer, the polymerization initiator and the hypophosphorous acid (salt) or a small amount of all the components is used as the initial charge. It is of course possible to polymerize.

Other production conditions are not particularly limited, and ordinary polymerization conditions are applied. For example, the polymerization temperature is 2
The temperature may be 0 to 150 ° C, preferably 70 to 110 ° C. Further, the pH of the system at the time of polymerization is 0.5 to 13.
The range of 5 to 1 is preferable. In addition, it is of course possible to produce it in the presence of a reducing agent such as L-ascorbic acid (salt), (bis) sulfite (salt), and iron during polymerization.

In the present invention, a monomer other than the (meth) acrylic acid-based water-soluble monomer may be used together with the (meth) acrylic acid-based water-soluble monomer as long as the effects of the invention are not impaired. Of course it is possible. Examples of such a monomer include amide-based monomers such as (meth) acrylamide and t-butyl (meth) acrylamide; and hydrophobicity such as (meth) acrylic acid ester, styrene, 2-methylstyrene and vinyl acetate. Monomer: vinyl sulfonic acid, allyl sulfonic acid, methallyl sulfonic acid, styrene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, 3-allyloxy-2-hydroxypropane sulfonic acid, sulfoethyl (meth) acrylate, sulfo Propyl (meta)
Acrylate, 2-hydroxysulfopropyl (meth)
Unsaturated sulfonic acid type monomer such as acrylate, sulfoethylmaleimide or monovalent metal or divalent metal thereof, ammonia, partially neutralized product or completely neutralized product with organic amine; 3-methyl-3-butene- 1-ol (isobrenol), 3-methyl-2-buten-1-ol (brenol), 2-methyl-3-buten-2-ol (isoprene alcohol), 2-hydroxyethyl (meth) acrylate, polyethylene glycol mono (Meth) acrylate, polypropylene glycol mono (meth) acrylate, polyethylene glycol monoisoprenol ether, polypropylene glycol monoisoprenol ether, polyethylene glycol monoallyl ether, polypropylene glycol monoallyl ether, glycerol monoant Unsaturated hydroxyl group-containing monomers such as ether, α-hydroxyacrylic acid, N-methylol (meth) acrylamide, glycerol mono (meth) acrylate, vinyl alcohol; dimethylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylamide Cationic monomers such as; (meth)
Nitrile-based monomers such as acrylonitrile; phosphorus-containing monomers such as (meth) acrylamidomethanesulfonic acid, (meth) acrylamidomethanesulfonic acid methyl ester, 2- (meth) acrylamido-2-methylpropanephosphonic acid; itaconic acid , Dicarboxylic acid type monomers such as maleic acid, citraconic acid and fumaric acid; and crotonic acid.

The amount of these copolymerizable monomers to be used is preferably less than 30 mol% with respect to all the monomers.

Although it is not clear whether the production method of the present invention or the product obtained by the production method has a significantly excellent effect, it is presumed as follows.

That is, in the production method of the present invention, the hypophosphorous acid (salt) acts efficiently in order to carry out the polymerization at a higher concentration and in a specific method than in the conventional production method. )
It is believed that it will be possible to produce a highly pure product having a low content of hypophosphorous acid (salt) and / or its modified product.

Further, the product of the present invention has a high purity, so that when it is used as, for example, a scale inhibitor or a metal corrosion inhibitor, initial scale nucleation based on hypophosphorous acid (salt) and / or its modified product. It is presumed that this is due to the significant suppression of Further, the (meth) acrylic acid-based water-soluble polymer of the present invention also exhibits excellent effects as an inorganic pigment dispersant. Such inorganic pigments include kaolin, clay, calcium carbonate, satin white, titanium dioxide,
Pigment for coated paper such as aluminum hydroxide; suitably used as a dispersant for industrial materials such as red iron oxide, magnesium hydroxide, magnetic powder, slaked lime, cement, silica and calcium sulfate.

[0023]

Industrial Applicability According to the method for producing a (meth) acrylic acid-based water-soluble polymer according to the present invention, a (meth) acrylic acid-based water-soluble polymer having high purity, low cost and high safety is industrially produced. It can be easily manufactured. Further, surprisingly, when it is used as a so-called water treatment agent such as a scale inhibitor and a corrosion inhibitor, and an inorganic pigment dispersant, the function is remarkably superior to that of conventional products.

As described above, the present invention has extremely high industrial utility value.

[0025]

EXAMPLES The present invention will now be described in detail with reference to examples, but the present invention is not limited to these examples. In addition, part and% in an example show a weight part and weight%.

Example 1 A SUS316 separable flask having a volume of 5 l was charged with 321.9 parts of ion-exchanged water, the temperature was raised to 100 ° C., the atmosphere was replaced with nitrogen, and then 587.5 parts of 80% acrylic acid aqueous solution, 15% was added.
68.7 parts of sodium persulfate aqueous solution (0.0066 mol / 1 mol of acrylic acid) and 21.9 parts of 30% sodium hypophosphite aqueous solution (0.0095 mol / 1 mol of acrylic acid) are respectively added to separate dropping ports. It was added dropwise over 2 hours.
During this time, the temperature of the system maintained the boiling point of the system throughout. Further, aging was carried out for 10 minutes at the same temperature to complete the polymerization, and a (meth) acrylic acid-based water-soluble polymer (1) having a concentration of 47% in terms of acrylic acid in the liquid after the polymerization was obtained. The (meth) acrylic acid-based water-soluble polymer (1) was neutralized (pH = 8) with a 48% sodium hydroxide aqueous solution, and the performance of the neutralized product obtained was evaluated as follows. .

Inorganic pigment dispersive capacity 1 liter (material SUS304, inner diameter 90 mm, height 16)
0.2 parts of the neutralized product of the (meth) acrylic acid-based water-soluble polymer (1) as a dispersant and water were added to a 0 mm) beaker to make the total amount 100 parts. While stirring at low speed with a dissolver stirring blade (50 mmφ), 100 parts of kaolin (Sieglite for MC, Siege for MC) was added over 3 minutes. Then, the mixture was dispersed at 3000 rpm for 10 minutes.

The viscosities of the thus-obtained kaolin 50% slurries were measured with a B type viscometer, and the results are shown in Tables 1 and 2.

Scale prevention capacity 170 parts of water was put into a glass bottle having a capacity of 225 ml, and 10 parts of a 1.56% calcium chloride dihydrate aqueous solution and (meth) were added.
0.02% of the neutralized product of acrylic acid-based water-soluble polymer (1)
Calcium carbonate 5 obtained by mixing 1 part of an aqueous solution (1 ppm with respect to the obtained calcium carbonate supersaturated aqueous solution) and further adding 10 parts of a 3% aqueous solution of sodium bicarbonate and mixing
A 30 ppm supersaturated solution was sealed and heat-treated at 70 ° C. for 3 hours. Then, after cooling, the precipitate was filtered through a 0.2 μ Mengran filter, the filtrate was analyzed according to JISK0101, and the scale inhibition rate (%) was calculated according to the following formula.

[0030] A: CaCO ₃ concentration before heat treatment (= 530 ppm) B: CaCO ₃ concentration in the filtrate after the additive-free test (= 195)
ppm) C: CaCO ₃ concentration in the filtrate after the test The obtained results are shown in Tables 1 and 2.

Corrosion Inhibition Ability of Metal In a separable flask made of SUS316 having a capacity of 500 cc, 445 ml of synthetic water having the properties shown in Table 5 (corresponding to 4-fold concentration of water in Himeji City) was taken, and as a corrosion inhibitor (meta). A neutralized product of the acrylic acid-based water-soluble polymer (1) was added to synthetic water at 60 ppm in terms of solid content, the pH was adjusted to 8.5 with sodium hydroxide, and then deionized water was added. The total amount was 450 ml and a test solution was prepared. Next, in the obtained test liquid, 25 mm × 40 mm × 1 mm
2 SS-41 test pieces were suspended and heat-treated at 40 ° C. for 40 hours while flowing 25 ml / min of air over the test solution. After the heat treatment, the weight loss of the test piece was measured by removing the corrosion products on the test piece. As a result, the average value of weight loss of two test pieces was calculated by MDD (mg / dm ² / d
ay) conversion and shown in Table 1 and Table 2.

Example 2 In Example 1, the initially charged ion-exchanged water 321.9 was used.
A (meth) acrylic acid-based water-soluble polymer (2) having an acrylic acid equivalent concentration of 38% was obtained in the same manner as in Example 1 except that 558.7 parts of ion-exchanged water was used instead of the parts. The (meth) acrylic acid-based water-soluble polymer (2) was neutralized in the same manner as in Example 1, and the performance of the resulting neutralized product was evaluated in exactly the same manner as in Example 1. The obtained results are shown in Tables 1 and 2.

Example 3 In Example 1, ion-exchanged water 321.9 initially charged was used.
84.3 parts of deionized water instead of 80 parts acrylic acid water-soluble 587.5 parts 100% acrylic acid 470 instead of 587.5 parts
Parts and 68.2 parts of 30% aqueous solution of hypophosphorous acid were used instead of 21.9 parts of 30% aqueous solution of sodium hypophosphite, respectively.
% (Meth) acrylic acid-based water-soluble polymer (3) was obtained. The (meth) acrylic acid-based water-soluble polymer (3) was neutralized in the same manner as in Example 1, and the neutralized product thus obtained was tested for performance in Example 1.
It evaluated in exactly the same manner as. The obtained results are shown in Tables 1 and 2.

Example 4 The methacrylic acid equivalent concentration was 4 in the same manner as in Example 1 except that 587.5 parts of an 80% methacrylic acid aqueous solution was used in place of 587.5 parts of an 80% acrylic acid aqueous solution.
A 7% (meth) acrylic acid-based water-soluble polymer (4) was obtained. The (meth) acrylic acid polymer (4) was neutralized in the same manner as in Example 1, and the performance of the neutralized product obtained was evaluated in exactly the same manner as in Example 1. The obtained results are shown in Tables 1 and 2.

Example 5 Ion-exchanged water 3 was placed in the same polymerization vessel as used in Example 1.
Charge 5.1 parts, raise the temperature to 100 ° C., replace with nitrogen, and then 4
89.2% acrylic acid aqueous solution 979.2 parts, 48% sodium hydroxide aqueous solution 543.9 parts, 30% sodium persulfate aqueous solution 34.4 parts (0.0066 mol / sodium acrylate 1 mol) and 30% hypophosphorous acid Aqueous sodium solution 2
1.9 parts (0.0095 mol / sodium acrylate 1
Mol) was added dropwise over 2 hours. The 48% aqueous solution of acrylic acid and the 48% aqueous solution of sodium hydroxide were added dropwise just before the dropping port and introduced into the polymerization system as an aqueous solution of sodium acrylate. Others were introduced into the polymerization system through separate dropping ports. During this time, the temperature of the system maintained the boiling point throughout. Further, aging was carried out for 10 minutes at the same temperature to complete the polymerization, and a (meth) acrylic acid-based water-soluble polymer (5) having a concentration of sodium acrylate in the liquid after the polymerization of 38% was obtained. The performance of the (meth) acrylic acid-based water-soluble polymer (5) is shown in Example 1.
It evaluated in exactly the same manner as. The obtained results are shown in Tables 1 and 2.

Example 6 In Example 1, 80% acrylic acid aqueous solution 587.5
Parts, 68.7 parts of 15% aqueous sodium persulfate solution and 30 parts
% Aqueous sodium hypophosphite solution (21.9 parts) was dividedly introduced into the polymerization system every 1 minute in an amount of 1/24 and reacted. Aging was performed in the same manner as in Example 1, and the acrylic acid conversion concentration was 47.
% (Meth) acrylic acid-based water-soluble polymer (6) was obtained. The (meth) acrylic acid-based water-soluble polymer (6) was neutralized in the same manner as in Example 1, and the neutralized product thus obtained was tested for performance in Example 1.
It evaluated similarly to. The obtained results are shown in Tables 1 and 2.

Example 7 Ion-exchanged water 28 was placed in the same polymerization vessel as used in Example 1.
Charge 5 parts, raise the temperature to 100 ° C., replace with nitrogen, then 80%
Acrylic acid aqueous solution 587.5 parts, 37% sodium acrylate aqueous solution 236.9 parts, 50% 3-allyloxy-2
-Sodium hydroxypropane sulfonate (HAP
S) Aqueous solution 813 parts, 15% sodium persulfate aqueous solution 9
7.6 parts (0.0066 mol / monomer 1 mol) and 30
% Aqueous solution of sodium hypophosphite 31.3 parts (0.009
5 mol / monomer 1 mol) was added dropwise from separate dropping ports over 2 hours. The same aging as in Example 1 was performed to obtain a (meth) acrylic acid-based water-soluble polymer (7) having a concentration of 47% as a monomer after polymerization. The (meth) acrylic acid-based water-soluble polymer (7) was neutralized in the same manner as in Example 1, and the performance of the resulting neutralized product was evaluated in exactly the same manner as in Example 1.
The obtained results are shown in Tables 1 and 2.

Comparative Example 1 Comparative Example 1 with the acrylic acid conversion concentration of 47% in the same manner as in Example 1 except that 21.9 parts of a 30% aqueous sodium hypophosphite solution was initially charged. ) An acrylic acid-based water-soluble polymer (1) was obtained. The comparative (meth) acrylic acid-based water-soluble polymer (1) was neutralized in the same manner as in Example 1, and the performance of the neutralized product thus obtained was evaluated in exactly the same manner as in Example 1. The obtained results are shown in Tables 3 and 4.

COMPARATIVE EXAMPLE 2 In Example 1, ion-exchanged water 321.9 initially charged.
1671.9 parts of ion-exchanged water were used instead of 80 parts and
% Acrylic acid aqueous solution 587.5 parts, 15% sodium persulfate aqueous solution 68.7 parts and 30% sodium hypophosphite 21.9 parts were all initially charged and reacted at 70 ° C. in the same manner as in Example 1. Polymerized to give an acrylic acid equivalent concentration of 2
A 0% (meth) acrylic acid-based water-soluble polymer (2) for comparison was obtained. The comparative (meth) acrylic acid polymer (2) was neutralized in the same manner as in Example 1, and the performance of the neutralized product thus obtained was evaluated in exactly the same manner as in Example 1. The obtained results are shown in Tables 3 and 4.

Comparative Example 3 In Example 1, the initially charged ion-exchanged water 321.9 was used.
Comparative (meth) acrylic acid-based water-soluble polymer (3) having an acrylic acid equivalent concentration of 35% was obtained in the same manner as in Example 1 except that 664.7 parts of ion-exchanged water was used instead of the parts. .
The comparative (meth) acrylic acid-based water-soluble polymer (3) was neutralized in the same manner as in Example 1, and the performance of the neutralized product thus obtained was evaluated in exactly the same manner as in Example 1. The obtained result is the third
The results are shown in Table 4 and Table 4.

Comparative Example 4 Acrylic acid equivalent concentration was 75 in the same manner as in Example 3 except that 19.8 parts of ion-exchanged water was used in place of 84.3 parts of the initially charged ion-exchanged water. % (Comparative (meth) acrylic acid-based water-soluble polymer (4) was obtained. The comparative (meth) acrylic acid-based water-soluble polymer (4) was neutralized in the same manner as in Example 3, and the neutralized product thus obtained was tested for performance in Example 3.
It evaluated in exactly the same manner as. The obtained results are shown in Tables 3 and 4.

Comparative Example 5 In the same manner as in Example 7 except that 1155.2 parts of ion-exchanged water was used in place of 285 parts of ion-exchanged water initially charged, the monomer conversion concentration was 33%. A comparative (meth) acrylic acid-based water-soluble polymer (5) was obtained. Comparative (meth) acrylic acid-based water-soluble polymer (5) was used in Example 7
Neutralization was carried out in the same manner as above, and the performance of the resulting neutralized product was evaluated in exactly the same manner as in Example 7. The obtained results are shown in Tables 3 and 4.

The (meth) acrylic acid-based water-soluble polymers (1) to (7) and the comparative (meth) acrylic acid-based water-soluble polymers (1) to (5) each have a molecular weight of 2 to 6 It was in the range of 100,000 and could be regarded as almost the same molecular weight.

[0044]

[Table 1]

[0045]

[Table 2]

[0046]

[Table 3]

[0047]

[Table 4]

[0048]

[Table 5]

Claims (4)

[Claims] 1. When a water-soluble (meth) acrylic acid-based monomer is polymerized in an aqueous solution to produce a (meth) acrylic acid-based polymer, the monomer-converted concentration of the polymer in the reaction solution after polymerization is Three
It is characterized in that a (meth) acrylic acid-based water-soluble monomer, a polymerization initiator and a hypophosphorous acid (salt) necessary to reach 8 to 72% by weight are successively introduced into an aqueous medium for polymerization. A method for producing a (meth) acrylic acid-based water-soluble polymer. 2. An inorganic pigment dispersant containing a (meth) acrylic acid-based water-soluble polymer as a main component, which is obtained by the production method according to claim 1. 3. A scale inhibitor comprising a (meth) acrylic acid-based water-soluble polymer obtained by the production method according to claim 1 as a main component. 4. A metal corrosion inhibitor containing a (meth) acrylic acid-based water-soluble polymer as a main component, which is obtained by the production method according to claim 1.