JPH10323697A - Antiscaling agent and scale-preventing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an antiscaling agent and method which has a large preventive effect against adhesion of various kinds of scale generated in a cooling water system, a boiler water system, or the like, exhibiting an excellent preventive effect against adhesion of silica and calcium scale in particular. SOLUTION: This antiscaling agent contains a polymer containing at least 50 mol.% of N-vinyl formamide or N-vinyl acetamide and a nonionic aqueous polymer containing less than 50 mol.% of N-vinyl formamide or N-vinyl acetamide. Scale is prevented by adding a polymer containing at least 50 mol.% of N-vinyl formamide or N-vinyl acetamide and a nonionic aqueous polymer containing less than 50 mol.% of N-vinyl formamide or N-vinyl acetamide into an aqueous solution.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a scale inhibitor and a scale prevention method. More specifically, the present invention relates to a scale inhibitor and a scale prevention method which can effectively prevent scales in a cooling water system, a boiler water system, and the like, and are particularly effective in preventing silica-based and calcium-based scales.

[0002]

2. Description of the Related Art Scale disturbances occur in heat transfer surfaces and pipes that come into contact with water, such as cooling water systems and boiler water systems. Especially,
In the open-circulation type cooling water system, from the standpoint of saving resources and energy, when performing high concentration operation with less discharge (blowing) of cooling water outside the system, dissolved salts are concentrated,
The heat transfer surface becomes easily corroded and becomes a hardly soluble salt to be scaled. The generated scale causes serious problems in the operation of the boiler and the heat exchanger, such as a decrease in thermal efficiency and a blockage of piping. Examples of scale species to be generated include calcium carbonate, calcium sulfate, calcium sulfite, calcium phosphate, calcium silicate, magnesium silicate, magnesium hydroxide, zinc phosphate, zinc hydroxide, and basic zinc carbonate. For calcium and magnesium scales, a polymer having a carboxyl group obtained by polymerizing maleic acid, acrylic acid, itaconic acid, etc. is effective as a scale inhibitor, and a monomer having a carboxyl group and vinyl sulfone Copolymers obtained by combining monomers having a sulfonic acid group such as acid, allylsulfonic acid, and 2-acrylamido-2-methylpropanesulfonic acid are generally used as scale inhibitors depending on the target water quality. . For silica-based scales, a scale inhibitor containing an acrylamide-based polymer, a cationic polymer, polyethylene glycol, or the like has been proposed, and polymers are properly used depending on the scale type. Since the water used in the cooling water system is usually industrial water or tap water, various ionic species are present in the water. Therefore, especially when performing a high concentration operation, a scale inhibitor which can effectively cope with all scale types is necessary.However, at present, there is no scale inhibitor which satisfies such conditions, and in particular, a silica-based scale. There is no effective scale inhibitor to prevent adhesion. For example, Japanese Unexamined Patent Publication (Kokai) No. 61-107998 proposes a scale inhibitor containing an acrylamide polymer and an acrylic acid polymer as a scale inhibitor having an excellent effect of preventing silica scale. However, while the acrylamide polymer has a scale preventing effect when the silica concentration is low, the effect decreases when the silica concentration is high. Further, Japanese Patent Application Laid-Open No. 7-256266 proposes a water treatment method in which a water-soluble cationic polymer, a halogenated aliphatic nitro alcohol, a low-molecular-weight carboxylic acid-based polymer or phosphonic acid is added. However, since the cationic polymer proposed here is a quaternary ammonium salt, it has a very strong cationic property, and easily forms a gel-like reaction product with silica or microorganism-derived stain (slime) in water. However, there is a drawback that troubles such as clogging are easily generated in the piping. Further, Japanese Unexamined Patent Publication No. Hei.
In Japanese Patent Application Laid-Open Publication No. Hei 9 (1999) -176, a scale inhibitor containing polyethylene glycol and a low molecular weight carboxylic acid-based polymer or phosphonic acid is proposed. However, polyethylene glycol has an effect of suppressing the adhesion of scale when the silica concentration is low, but has a problem that it is easily affected by other ions and the effect is not stable.

[0003]

SUMMARY OF THE INVENTION The present invention provides a cooling water system,
The purpose of the present invention is to provide a scale inhibitor and a scale prevention method which have a large effect in preventing the adhesion of various scales generated in a boiler water system and the like, and particularly exhibit an excellent effect in preventing the adhesion of silica and calcium scales. It is a thing.

[0004]

The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, the content of N-vinylformamide units or N-vinylacetamide units is 50 mol% or more. When the content of the polymer and the N-vinylformamide unit or the N-vinylacetamide unit is 50
It has been found that a scale inhibitor containing a nonionic water-soluble polymer of less than mol% is excellent in scale prevention effect, particularly silica and calcium scale prevention effect, and based on this finding, completes the present invention. Reached.
That is, according to the present invention, (1) the content of (A) the N-vinylformamide unit or the N-vinylacetamide unit is 5%;
A scale comprising: a polymer of 0 mol% or more; and (B) a nonionic water-soluble polymer having a content of N-vinylformamide units or N-vinylacetamide units of less than 50 mol%. Inhibitor and (2)
(A) a polymer having a content of N-vinylformamide units or N-vinylacetamide units of 50 mol% or more, and (B) a content of N-vinylformamide units or N-vinylacetamide units of less than 50 mol% Wherein a nonionic water-soluble polymer is added to an aqueous system.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, as the component (A), N-vinylformamide represented by the formula [1] or N-vinylacetamide represented by the formula [2] constitutes a polymer. A polymer having 50 mol% or more as a monomer unit is used. _{HCONHCH = CH 2 ... [1]} CH 3 CONHCH = CH 2 ... [2] The method for producing N- vinylformamide and N- vinylacetamide not particularly limited, for example, obtained by reacting acetaldehyde with formamide or acetamide N- (α-hydroxyethyl) formamide or N- (α
-Hydroxyethyl) acetamide is reacted with an alcohol to etherify it, and the etherified product is thermally decomposed at a high temperature in the gas phase, or N-vinylformamide or N-vinylacetamide formed by heating in the liquid phase is distilled off. It can be manufactured by pyrolysis while heating. The N- used as the component (A) in the present invention
Examples of the polymer having a content of vinylformamide units or N-vinylacetamide units of 50 mol% or more include, for example, homopolymers of N-vinylformamide, homopolymers of N-vinylacetamide, N-vinylformamide and N-vinylformamide. Copolymer of vinyl acetamide, partial hydrolyzate of homopolymer of N-vinylformamide, partial hydrolyzate of homopolymer of N-vinylacetamide, partial hydrolysis of copolymer of N-vinylformamide and N-vinylacetamide Examples thereof include a decomposition product, a copolymer of N-vinylformamide or N-vinylacetamide with a copolymerizable vinyl monomer, and the like. When the polymer is a copolymer of N-vinylformamide and N-vinylacetamide,
If the total of the N-vinylformamide units and the N-vinylacetamide units is at least 50 mol%, it can be used as the component (A) of the scale inhibitor of the present invention.

The vinyl monomer copolymerizable with N-vinylformamide or N-vinylacetamide can be used without any particular limitation as long as the copolymer obtained or further obtained by hydrolysis has water solubility. can do. Examples of such a vinyl monomer include, for example,
(Meth) acrylamide, (meth) acrylonitrile, N-
Methyl (meth) acrylamide, N, N-dimethyl (meth)
Acrylamide, methyl (meth) acrylate, ethyl
(Meth) acrylate, styrene, allyl alcohol, nonionic monomers such as hydroxyethyl (meth) acrylate, (meth) acrylic acid, α-hydroxy acrylic acid,
Crotonic acid, maleic acid, fumaric acid, itaconic acid and their alkali metal salts, vinylsulfonic acid, styrenesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, hydroxyallyloxypropanesulfonic acid, isoprenesulfonic acid and their salts Anionic monomers such as alkali metal salts, allylamine, dimethylaminoethyl (meth) acrylate and diethylaminoethyl
(Meth) quaternary ammonium salts or tertiary salts of acrylates,
Cationic monomers such as diallyldimethylammonium chloride can be exemplified.

In the present invention, the method of homopolymerization or copolymerization of N-vinylformamide or N-vinylacetamide is not particularly limited, and may be solution polymerization, bulk polymerization, or the like. Homopolymer of vinylacetamide and N-
Since the copolymer of vinylformamide or N-vinylacetamide is water-soluble or hydrophilic, aqueous polymerization using water as a medium can be suitably used. In the aqueous polymerization, an aqueous monomer solution or aqueous dispersion is prepared, the pH is adjusted if necessary, the atmosphere is replaced with an inert gas, and then the mixture is heated to 50 to 100 ° C. to form a water-soluble polymerization initiator. Polymerization can be carried out by adding. Examples of the water-soluble polymerization initiator include 2,2′-azobis (2-amidinopropane) dihydrochloride, azobis-N, N′-dimethyleneisobutylamidine dihydrochloride, 4,4′-azobis (4
Azo compounds such as -cyanovaleric acid) -2-sodium,
Persulfates such as ammonium persulfate, sodium persulfate and potassium persulfate; peroxides such as hydrogen peroxide and sodium periodate; The polymerization is usually completed in 3 to 6 hours, and by allowing to cool, an aqueous polymer solution or aqueous dispersion can be obtained. The polymerization can be carried out not only in an aqueous medium but also by a solution polymerization, a suspension polymerization, an emulsion polymerization or the like in a general organic solvent.

In the present invention, the homopolymer or copolymer of N-vinylformamide or N-vinylacetamide is hydrolyzed to give N-vinylformamide units or N-vinylformamide units.
When the vinylacetamide unit is an N-vinylamine unit, a polymer in which the total of the N-vinylformamide unit and the N-vinylacetamide unit remains at 50 mol% or more can be used as the component (A), A polymer in which the total of N-vinylformamide units and N-vinylacetamide units is less than 50 mol% can be used as the component (B). The conditions for the hydrolysis are not particularly limited.For example, after adding ammonia, a primary amine, a secondary amine, etc. to an aqueous solution or dispersion of a polymer, sodium hydroxide is added, and the mixture is hydrolyzed under basic conditions. It can be decomposed, or it can be hydrolyzed under acidic conditions by adding a mineral acid such as hydrochloric acid to an aqueous solution or aqueous dispersion of the polymer and heating. In the present invention,
The molecular weight of the polymer having a content of N-vinylformamide unit or N-vinylacetamide unit of 50 mol% or more used as the component (A) is preferably from 2,000 to 1,000,000. The molecular weight of the polymer is 2,000
If it is less than 0, a sufficient scale prevention effect may not be exhibited. On the other hand, if the molecular weight of the polymer exceeds 1,000,000, the viscosity of the solution at the time of use may be too high, which may make it difficult to handle. The molecular weight of the polymer can be determined by gel permeation chromatography. In the present invention, one kind of a polymer having a component (A) content of 50 mol% or more of N-vinylformamide units or N-vinylacetamide units can be used alone, or two or more kinds can be used in combination. Can also be used.

In the present invention, as the component (B), N-
A nonionic water-soluble polymer having a content of vinylformamide units or N-vinylacetamide units of less than 50 mol% is used. N-vinylformamide unit or N
Polymers containing less than 50 mol% of vinylacetamide units include N-vinylformamide units or N-vinylformamide units.
A polymer containing no vinylacetamide units,
-A polymer containing a fixed amount of less than 50 mol% of vinylformamide units or N-vinylacetamide units. Examples of the nonionic water-soluble polymer having a content of N-vinylformamide units or N-vinylacetamide units of less than 50 mol% used as the component (B) in the present invention include, for example, polyvinyl alcohol and polyethylene glycol. Water-soluble polymer, (meth) acrylamide, N-methylacrylamide, N, N-dimethylacrylamide, allyl alcohol, hydroxyethyl (meth) acrylate, mono (meth) acrylate of (poly) ethylene oxide having 1 to 30 moles of addition , Addition mole number 1
(Poly) monoallyl ether of (poly) ethylene oxide, homopolymers and copolymers such as monovinyl ether of (poly) ethylene oxide having 1 to 30 moles of addition, these monomers and methyl (meth) acrylate, Examples thereof include copolymers with ethyl (meth) acrylate, styrene, (meth) acrylonitrile, and the like, and copolymers obtained by copolymerizing N-vinylformamide or N-vinylacetamide at less than 50 mol%.

In the present invention, the molecular weight of the polymer used as the component (B), in which the content of N-vinylformamide units or N-vinylacetamide units is less than 50 mol%, is from 2,000 to 1,000,000. Preferably, there is. If the molecular weight of the polymer is less than 2,000, a sufficient scale prevention effect may not be exhibited. On the other hand, if the molecular weight of the polymer exceeds 1,000,000, the viscosity of the solution at the time of use may be too high, which may make it difficult to handle. The molecular weight of the polymer can be determined by gel permeation chromatography. There is no particular limitation on the form of the scale inhibitor of the present invention.
(B) A nonionic water-soluble polymer having a content of N-vinylformamide units or N-vinylacetamide units of less than 50 mol% as a mixed powder may be used by dissolving it in water before use. A polymer having a component (A) content of at least 50 mol% of N-vinylformamide units or N-vinylacetamide units;
An aqueous solution containing both a nonionic water-soluble polymer having a vinylformamide unit content or an N-vinylacetamide unit content of less than 50 mol%, or an N-vinylformamide unit of the component (A) Or N-
An aqueous solution of a polymer having a vinylacetamide unit content of 50 mol% or more, and a component (B) having an N-vinylformamide unit or an N-vinylacetamide unit having a content of 50 mol%
It may be a two-pack type of an aqueous solution of a nonionic water-soluble polymer in an amount of less than mol%.

In the method for preventing scale of the present invention,
A polymer in which the content of the N-vinylformamide unit or the N-vinylacetamide unit of the component (A) is 50 mol% or more; and the N-vinylformamide unit or the N-
A nonionic water-soluble polymer having a vinylacetamide unit content of less than 50 mol% is added to an aqueous system. The polymer having a content of the N-vinylformamide unit or the N-vinylacetamide unit of the component (A) of 50 mol% or more is as follows:
One type may be used alone, or two or more types may be used in combination. A nonionic water-soluble polymer having a component (B) content of less than 50 mol% of N-vinylformamide units or N-vinylacetamide units,
One type may be used alone, or two or more types may be used in combination. In the method of the present invention, (A)
A polymer having a component content of N-vinylformamide units or N-vinylacetamide units of 50 mol% or more and a component (B) having a content of N-vinylformamide units or N-vinylacetamide units of less than 50 mol% There is no particular limitation on the method of adding the nonionic water-soluble polymer to the aqueous system, for example, the polymer of the component (A) and the polymer of the component (B) can be separately added, or The polymer of the component (A) and the polymer of the component (B) can also be added as a pre-blended composition. (A) a polymer of the component
When the polymers of the component (B) are added separately, the order of addition is not particularly limited, and either one may be added first or both may be added simultaneously.

In the method of the present invention, a polymer having a component (A) content of at least 50 mol% of N-vinylformamide units or N-vinylacetamide units;
The ratio of the amount of the nonionic water-soluble polymer having a content of -vinylformamide unit or N-vinylacetamide unit of less than 50 mol% is not particularly limited, but the polymer of the component (A) and the polymer of the component (B) The ratio of the added amount of the component polymers is 1: 9 to 9: 1.
And more preferably 2: 8 to 8: 2. The scale inhibitor of the present invention can be added to an applied aqueous system as an aqueous solution adjusted to an arbitrary concentration. Usually, the polymer of the component (A) in the applied water and
It is preferable to add the component (B) so that the total concentration of the polymer is 1 to 100 mg / liter. The scale inhibitor of the present invention can be used in combination with another scale inhibitor as needed. As the scale inhibitor used in combination, for example, polyacrylic acid, polymaleic acid, a copolymer of acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid, N, N, N ', N'-tetramethylethylenediamine and Reaction products with epichlorohydrin,
Reaction products of N, N, N ', N'-tetramethylethylenediamine and dichloroethyl ether can be mentioned. The scale inhibitor of the present invention can be added to the same solution as an anticorrosive such as an organic phosphonate, a bactericide such as hydrazine, etc., if necessary,
Alternatively, these agents can be separately injected. There are no particular restrictions on the water quality conditions and the operating conditions of the boiler and heat exchanger when the scale inhibitor and scale prevention method of the present invention are applied, and the present invention is applied to ordinary boilers and heat exchanger operating conditions and water quality. be able to. The scale inhibitor and scale prevention method of the present invention are calcium carbonate, calcium sulfate, calcium phosphate, zinc phosphate,
Zinc hydroxide, magnesium silicate, silica, etc., which are generated in boilers and cooling water systems and can effectively prevent scale from adhering to heat transfer surfaces and pipe wall surfaces, are particularly effective in preventing silica-based scale from adhering. is there. The action mechanism in which the scale inhibitor and the scale prevention method of the present invention are particularly effective in preventing silica-based scale is unknown, but the N-vinylformamide unit or the N-vinylacetamide unit of the polymer of the component (A) is unknown. It is thought that the amide group and the hydroxyl group, ether group, amide group, etc. of the nonionic water-soluble polymer used in combination act on the silica hydroxyl group synergistically, effectively preventing adhesion to the wall surface of the silica-based scale. .

[0013]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the present invention. N used in Examples and Comparative Examples
Polymers having 50 mol% or more of vinylformamide units or N-vinylacetamide units (N-vinylamide polymers), nonionic water-soluble polymers, anionic water-soluble polymers, and scale adhesion test methods are described below. Shown in [N-vinylamide polymer] A-1: poly-N-vinylformamide, molecular weight 80,
000. A-2: 10 mol% hydrolyzate of poly-N-vinylformamide, molecular weight 90,000. A-3: a copolymer of N-vinylformamide and acrylamide at a molar ratio of 6: 4, molecular weight 45,000. [Nonionic water-soluble polymer] N-1: polyvinyl alcohol, molecular weight 20,000. N-2: polyacrylamide, molecular weight 12,000. N-3: a copolymer of N-vinylformamide and acrylamide in a molar ratio of 4: 6, molecular weight 25,000. [Anionic water-soluble polymer] P-1: sodium polyacrylate, molecular weight 9,000
0. [Scale adhesion test method] In an open-circulating cooling water system having a heat exchanger with a heat transfer area of about 0.25 m ² and a water volume of 0.45 m ³ , pure water and salts added to Atsugi City water were circulated. The operation was continued for 30 days while the water quality was constantly controlled. The material of the heat exchanger tube is SUS
At 304, an outer diameter of 19 mm was used. The circulating water inlet temperature is 30 ° C., the circulating water outlet temperature is 50 ° C., and the circulating water flow rate is 0.5 m / s. A predetermined amount of the scale inhibitor was added to the aqueous system, and after 30 days, the scale attached to the heat exchanger tube was collected and ashed at 600 ° C., and the CaO and SiO ₂ amounts were measured by chemical analysis. The deposition rate was determined in (mg / cm ² / month). Example 1 N-vinylamide polymer A-1 was added to water having a water quality of pH 9.0, calcium hardness of 150 mg / l, M alkalinity of 150 mg / l, silica of 200 mg / l, and magnesium hardness of 200 mg / l, at a concentration of 10 mg / l. The test was performed by adding 10 mg / liter of a nonionic water-soluble polymer N-1. The scale deposition rate is
CaO is 2mg / cm ² / month, SiO ₂ is 1mg / cm ² /
It was the moon. Example 2 A test was performed by adding 15 mg / L of the N-vinylamide polymer A-2 and 5 mg / L of the nonionic water-soluble polymer N-1 to water having the same water quality as in Example 1. The scale deposition rate was 2 mg / cm ² / month for CaO and
O ₂ was 2 mg / cm ² / month. Example 3 A test was carried out by adding 12 mg / L of N-vinylamide polymer A-3 and 8 mg / L of nonionic water-soluble polymer N-2 to water having the same water quality as in Example 1. The scale deposition rate was as follows: CaO was 1 mg / cm ² / month;
O ₂ was 2 mg / cm ² / month. Comparative Example 1 An N-vinylamide polymer A-1 was added to water of the same water quality as in Example 1 at 20 mg / liter, and a test was conducted. The scale deposition rate was 9 mg / cm ² / month for CaO,
iO ₂ was 6 mg / cm ² / month. Comparative Example 2 A nonionic water-soluble polymer N-1 was added to water of the same water quality as in Example 1 at 20 mg / liter, and a test was carried out. The scale deposition rate is 15 mg / cm ² / month for CaO,
SiO ₂ was 53 mg / cm ² / month. Comparative Example 3 A nonionic water-soluble polymer N-3 was added to water having the same water quality as in Example 1 at a concentration of 20 mg / L, and a test was performed. The scale deposition rate was 18 mg / cm ² / month for CaO,
SiO ₂ was 48 mg / cm ² / month. Comparative Example 4 An anionic water-soluble polymer P-1 was added to water of the same water quality as in Example 1 at a concentration of 20 mg / L, and a test was conducted. The scale deposition rate is 17 mg / cm ² / month for CaO,
SiO ₂ was 89 mg / cm ² / month. Table 1 shows the results of Examples 1 to 3 and Comparative Examples 1 to 4.

[0014]

[Table 1]

Example 4 N-vinylamide polymer A-1 was added to water having a water quality of pH 9.0, calcium hardness of 150 mg / l, M alkalinity of 150 mg / l, silica of 300 mg / l, and magnesium hardness of 300 mg / l. The test was performed by adding 10 mg / liter of the nonionic water-soluble polymer N-1 at 10 mg / liter. The scale deposition rate is
CaO is 2mg / cm ² / month, SiO ₂ is 1mg / cm ² /
It was the moon. Example 5 A test was carried out by adding 10 mg / L of the N-vinylamide polymer A-2 and 10 mg / L of the nonionic water-soluble polymer N-2 to water having the same water quality as in Example 4. The scale deposition rate was 2 mg / cm ² / month for CaO,
iO ₂ was 2 mg / cm ² / month. Example 6 A test was performed by adding 15 mg / L of the N-vinylamide polymer A-3 and 5 mg / L of the nonionic water-soluble polymer N-3 to water having the same water quality as in Example 4. The scale deposition rate was 2 mg / cm ² / month for CaO and
O ₂ was 1 mg / cm ² / month. Comparative Example 5 An N-vinylamide polymer A-2 was added to water of the same water quality as in Example 4 at a concentration of 20 mg / L, and a test was conducted. The scale deposition rate was 13 mg / cm ² / month for CaO,
SiO ₂ was 14 mg / cm ² / month. Comparative Example 6 A nonionic water-soluble polymer N-2 was added to water having the same water quality as in Example 4 at a concentration of 20 mg / L, and a test was conducted. The scale deposition rate was 18 mg / cm ² / month for CaO,
SiO ₂ was 49 mg / cm ² / month. Comparative Example 7 A test was carried out by adding 20 mg / liter of nonionic water-soluble polymer N-3 to water having the same water quality as in Example 4. The scale deposition rate is 21 mg / cm ² / month for CaO,
SiO ₂ was 81 mg / cm ² / month. Comparative Example 8 An anionic water-soluble polymer P-1 was added to water having the same water quality as in Example 4 at a concentration of 20 mg / L, and a test was carried out. The scale deposition rate is 23 mg / cm ² / month for CaO,
SiO ₂ was 94 mg / cm ² / month. Table 2 shows the results of Examples 4 to 6 and Comparative Examples 5 to 8.

[0016]

[Table 2]

From the results shown in Tables 1 and 2, polymer (A) containing 100 mol% of N-vinylformamide units as component (A) and 90 mol of N-vinylformamide units were used. % Polymer A-2 or polymer A having a content of N-vinylformamide units of 60 mol%
-3 and poly (vinyl alcohol N-1 having no N-vinylamide unit as component (B), polyacrylamide N-2 having no N-vinylamide unit or N-vinylformamide unit having a content of 40 mol%. Combined N-
It can be seen that, in the example in which No. 3 was used, the scale adhesion speed of CaO and SiO ₂ was low, and an excellent scale prevention effect was exhibited. On the other hand, Comparative Example 1 and Comparative Example 5 in which only the polymer A-1 or A-2 of the component (A) was added without adding the polymer of the component (B), Without adding the coalescence, the polymer N-
1, Comparative Example 2, Comparative Example 3, Comparative Example 6, and Comparative Example 7, in which only N-2 or N-3 was added, had a high scale adhesion rate, and the polymer of the component (A) and the polymer of the component (B) It can be seen that an excellent scale prevention effect is exhibited only when the polymer is used in combination. Also, in Comparative Examples 4 and 8 using sodium polyacrylate P-1 which has been widely used as a scale inhibitor, the scale adhesion rate was higher than that of the Examples, and the scale inhibitor of the present invention was used. It can be seen that is superior in the scale prevention effect to the conventional scale inhibitor.

[0018]

The scale inhibitor of the present invention has an excellent effect of preventing the adhesion of scale as compared with the conventional scale inhibitor, and is particularly effective in preventing the adhesion of silica-based and calcium-based scales.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI C23F 11/14 101 C23F 11/14 101 (72) Inventor Shigeru Sato 3-4-7 Nishishinjuku, Shinjuku-ku, Tokyo Kurita Industrial Co., Ltd. Inside the company (72) Inventor Rei Usui 3-4-7 Nishi-Shinjuku, Shinjuku-ku, Tokyo Kurita Kogyo Co., Ltd. (72) Inventor Aya Sakaguchi 3-4-2, Nishi-Shinjuku, Shinjuku-ku, Tokyo Kurita Kogyo

Claims (2)

[Claims] (A) N-vinylformamide unit or N
A polymer having a vinylacetamide unit content of 50 mol% or more and a nonionic water-soluble polymer (B) having a N-vinylformamide unit or N-vinylacetamide unit content of less than 50 mol%. A scale inhibitor characterized by containing. (A) N-vinylformamide unit or N
A polymer having a vinylacetamide unit content of 50 mol% or more and a nonionic water-soluble polymer (B) having a N-vinylformamide unit or N-vinylacetamide unit content of less than 50 mol%. A scale prevention method characterized by being added to an aqueous system.