JPH01299700A - Simultaneous preventing agent for corrosion and scale of metals in water system - Google Patents

Abstract

PURPOSE:To economically prevent the corrosion of piping, etc., with a low concn. and the eliminate the need for pH adjustment by combining phosphoric acids, zinc salt and/or molybdate, and a specific copolymer. CONSTITUTION:The water soluble org. phosphorus compd. such as water soluble org. phosphoric acids having a carbon-phosphorus bond and the water soluble zinc salt and/or molybdate are used as the scale suppressing agent for metallic materials such as pipings of a water system. The copolymer which is a water soluble copolymer contg. (meth)acrylic acid and contains 10-70wt.% monomer expressed by the formula I (R1 in H or methyl group, R2, R3 are alkyl groups of 1-4C) as N-substd. methacrylic amide is combined therewith. The corrosion is then prevented by the synergistic effect even if the concn. is low and the need for the pH adjustment is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION Human and industrial fields of application The present invention relates to a synergistic composition for preventing corrosion and inhibiting scale of metal materials such as heat exchangers and piping in aqueous systems including cooling water systems. Regarding.

B. Conventional Technology Various water treatment agents are used to prevent corrosion of metal materials and suppress scale in water systems such as cooling water systems. Among these water treatment agents, chromate,
Heavy metal salts such as zinc salts and phosphoric acid compounds are used, but the use of chromates has been restricted in recent years to prevent pollution.

Among phosphoric acid compounds, polymerized phosphoric acids are easily hydrolyzed in water systems, so they easily turn into scales such as calcium phosphate, and if wastewater is discharged without any treatment, it causes eutrophication of lakes and oceans and disturbs the ecosystem. becomes.

Therefore, instead of polymerized phosphoric acids, phosphonic acids have recently been frequently used because they are less susceptible to hydrolysis in aqueous systems and are less likely to scale, and because they can reduce the phosphorus concentration in wastewater.

It is thought that these phosphonic acids react with calcium in water to form a metal protective film of calcium phosphonate, exhibiting an anti-corrosion effect, but since phosphonic acids alone do not have sufficient anti-corrosion properties, zinc salts etc. are added. This strengthens the anti-corrosion ability.

Furthermore, phosphonic acids are known to have the effect of suppressing calcium carbonate scale at low concentrations. Phosphonic acids commonly used in cooling water systems include 1-hydroxyethylidene-1,1-diphosphonic acid, 2-hydroxyphosphonoacetic acid, aminotrimethylenephosphonic acid, and 2-hydroxyethylidene-1,1-diphosphonic acid.
Examples include phosphonobutane-1t2t41'licarboxylic acid. Although these phosphonic acids have excellent anti-corrosion effects, they tend to react with calcium and zinc ions in water and precipitate as calcium phosphonate and zinc phosphonate due to the increase in pH and hardness components. Corrosion protection and scaling inhibition may be lost due to decreased acid and zinc concentrations.

Problems to be Solved by the C0 Invention It is an object of the present invention to solve the above-mentioned drawbacks and problems.

The present inventors have completed the present invention as a result of intensive research on improving the anticorrosive effect when using phosphonic acids and zinc salts together, methods for inhibiting scale and staining, and synergistic compositions. did it. That is, the object of the present invention is to prevent the scale deposition caused by the reaction of phosphonic acid with calcium and zinc ions in water, as well as the precipitation and deposition of other sparingly soluble salts in water, and also to suppress the scale of metals in an aqueous system. A water treatment composition for preventing corrosion, and by adding an acid to prevent scale p
1. To provide a composition that does not require any H control.

Means for Solving the D0 Problem The inhibitor of the present invention has (a) a carbon-phosphorus bond. At least one water-soluble organic phosphorus compound selected from water-soluble organic phosphonic acids and water-soluble organic phosphinic acids; (b) At least one salt selected from water-soluble zinc salts and molybdates; ( C) A water-soluble copolymer containing (meth)acrylic acid and N-substituted (meth)acrylamide as constituent units, wherein the N-substituted (meth)acrylamide has the formula: [wherein R1 is hydrogen or a methyl group] R2 and R3 are each independently hydrogen or an alkyl group having 1 to 4 carbon atoms, and the total number of carbon atoms of R: and R3 is 2 to 6. ] at least one selected from the monomers represented by and (meth)acryloylmorpholine, and the composition ratio of the N-substituted (meth)acrylamide in the copolymer is 10 to 7.
0% by weight of a copolymer as an active ingredient.

The water-soluble organic phosphonic acids having a carbon-phosphorus bond used in the present invention are compounds having a structural unit represented by the formula; acid,
1-Phosphonopropane-2,,3:←Dicarboxylic acid, phosphonosuccinic acid, μm methylphosphonosuccinic acid, phosphonocarbo/acids such as 1-phosphonopropane-1,2,3-tricarboxylic acid, aminotrimethylenephosphonic acid ,
Aminophosphonic acids such as ethylenediaminetetramethylenephosphonic acid, hexamethylenediaminenato-2methylenephosphonic acid, diethylenetriaminepentamethylenephosphonic acid, 1-hydroxyethylidene-1°1-disulfonic acid, 1-hydroxypropyritine-1,1-disulfonic acid and hydroxy-substituted lower alkylenephosphonic acids such as 2-hydroxyphosphonoacetic acid. The most preferred water-soluble organic phosphonic acids are 2-phosphonobutane-
1,2,4-) IJ carboxylic acid, 1-hydroxyethylidene-1,1-disulfonic acid, 2-hydroxyphosphonoacetic acid and aminotrimethylenephosphonic acid.

The water-soluble organic phosphonic acids used in the present invention refer to phosphonic acids and water-soluble salts thereof.

The water-soluble salts mentioned here are those in which part or all of the protons of the phosphoric acid group and/or carboxyl group are substituted with an alkali metal, alkaline earth metal, zinc, ammonia, and/or amino acids, etc. , refers to substances that can be dissolved at the concentration used.

The water-soluble organic phosphinic acids having a carbon-phosphorus bond used in the present invention are compounds having a constitutional unit represented by the formula; -H#OH is independently an alcohol residue having 1 to 4 carbon atoms or a ketone residue having 3 to 4 carbon atoms, R,, R1,, R4, R1, represent hydrogen or a carboxy group, R2 and R, 3 cannot be hydrogen at the same time, and the same is true for R4 and Rs, mI!
, n each represent an integer from 1 to 20. ] Compounds represented by these can be mentioned. More preferred water-soluble organic phosphinic acids are acrylic acid and hypophosphorous acid in the presence of a reaction initiator! It is a compound obtained by reacting, and the reaction molar ratio of acrylic acid and hypophosphorous acid is 2:1
The range is preferably from 16:1 to 16:1, more preferably from 3:1 to 8:19. The above-mentioned organic phosphinic acid can be produced, for example, by the method described in JP-A-55-14900.

The water-soluble organic phosphinic acids used in the present invention refer to phosphinic acids and water-soluble salts thereof. The water-soluble salts herein refer to those in which part or all of the protons of the phosphoric acid group and/or carboxyl group are substituted with an alkali metal, alkaline earth metal, zinc, ammonia, and/or amines, etc. Refers to substances that can be dissolved at the concentration used.

The water-soluble organic phosphorus compound used in the present invention is 2
You may use a mixture of more than one species. A preferred combination of water-soluble organophosphorus compounds is 1-hydroxyethylidene-
One or more selected from 1,1-diphosphonic acid and 2-hydroxyphosphonoacetic acid and 2-phosphonobutane-1s
It is a combination with one or more selected from 2 p 4-tricarbo/acid and phosphinic acid obtained by reacting acrylic acid and hypophosphorous acid.

The zinc compound used in the present invention may be anything as long as it dissolves at the concentration used in the zinc aqueous system and releases zinc ions, but preferably zinc chloride, zinc sulfate, zinc nitrate, zinc acetate, Examples include zinc malate and zinc citrate.

The molybdate used in the present invention may be any molybdate as long as it dissolves at the concentration used in the aqueous system and releases molybdate ions, but preferably alkali metals, alkaline earth metals, zinc, ammonia, etc. /or salts of amines.

Either the zinc salt or the molybdate salt may be used, or they may be used simultaneously.

Said N-substitution in the copolymer used in the present invention (
As an example of meth)acrylamide, N-ethyl(meth)
Acrylamide, N-propyl (meth)acrylamide, N-1rtcs-propyl (meth)acrylamide,
N-butyl (meth)acrylamide, N-1ho-butyl (meth)acrylamide.

N-5ec-butyl (meth)acrylamide, N-te
N-monosubstituted (meth) such as rt-butyl (meth)acrylamide, N-amyl (meth)acrylamide, N-1so-amyl (meth)acrylamide, N-methylbutyl (meth)acrylamide, N-hexyl (meth)acrylamide, etc. Acrylamides, N,N-dimethyl(meth)acrylamide.

N-Methyl-N-ethyl (meth)acrylamide.

N,N-diethyl (meth)acrylamide, N-methyl-N-propyl (meth)acrylamide.

N-methyl-N-butyl (meth)acrylamide.

N-Methyl-N-iso-butyl (meth)acrylamide, N-methyl-N-3-methylbutyl (meth)acrylamide, N-ethyl-N-propyl (meth)acrylamide, N-ethyl-N-is.

-N,N-disubstituted (meth)acrylamides such as -propyl(meth)acrylamide, N,N-dipropylacrylamide, N,N-di-1so-propyl(meth)acrylamide, and (meth)acryloylmorpholine.

The copolymerization composition ratio of N-substituted (meth)acrylamide in the water-soluble copolymer must be at least 10 to 70% by weight, and more preferably 20 to 60% by weight.

(Meth)acrylic acid, which is a constituent unit of the water-soluble copolymer, represents either acrylic acid or methacrylic acid, or both. The total copolymer composition ratio of acrylic acid and methacrylic acid in the copolymer is preferably in the range of 30 to 90% by weight, more preferably 40 to 80% by weight.
It is.

The copolymer may be a ternary or more multicomponent copolymer containing monomers other than (meth)acrylic acid and N-substituted (meth)acrylamide as constituent units. Examples of these monomers include carboxylic acids such as maleic acid, maleic anhydride, fumaric acid, itaconic acid, and crotonic acid, (meth)acrylamide, N-vinyl-N-methylacetamide, N-methylolacrylamide, and Amides such as acetone acrylamide, methyl (meth)acrylate,
(Meth)acrylic acid esters such as ethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-
Hydroxyalkyl (meth)acrylates such as methacryloxy-1,2-dihydroxypropane, allyl alcohol, 3-methyl-3-buty/-1-ol, 3-
Alcohols such as methyl-2-buten-1-ol and 2-methyl-3-buten-2-ol, sulfo/acids such as vinylsulfonic acid and (meth)allylsulfonic acid, alkyl vinyl ethers, 3-allyloxy (methallyloxy) −
Ethers such as 1,2-dihydroxypropane, allyl (methallyl) polyalkylene glycol, vinyl acetate,
(Meth)acryloxy polyalkylene/glycols and the like can be mentioned.

A preferred example of a copolymerizable component with (meth)acrylic acid and N-substituted (meth)acrylamide is the formula: Rs is represented by the following formula: In the formula, X, X2 each independently represent hydrogen, a hydroxyl group, or a methyl group, and n is an integer from 1 to 3. It is an unsaturated sulfonic acid monomer. A copolymer containing a heptanoah/ethya heptaunsaturated sulfonic acid as a structural unit is suitable because it improves product compatibility with the organic phosphorus compound and zinc salt, which are other components of the present invention. Examples of the monoethylenically unsaturated sulfonic acid monomer include 2-acrylamido-2-methylpropanesulfonic acid, 2-methacrylamido-2-methylpropanesulfonic acid,
Acid, sulfopropylacrylic acid, sulfopropyl methacrylic acid, 3-acryloxy1,2-dihydroxypropanesulfonic acid, 3-methacryloxy-1,2-dihydroxypropanesulfonic acid, 3-allyloxy1,2-dihydroxypropanesulfonic acid, 3 -Aryloxy-2-hydroxypropane sulfonate % 3-methasoroxy-2
-hydroxypropanesulfonic acid and the like, but a more preferred monomer is 2-acrylamido-2-methylpropanesulfonic acid. The polymerization composition ratio of the monoethylenically unsaturated sulfonic acid monomer in the copolymer is preferably from 0 to 40% by weight.

The preferred molecular weight of the polymer is L00 as a weight average molecular weight.
0 to 10QOOO, more preferably 4000 to 3
QOOO. Here, the weight average molecular weight is measured by gel vermiculin chromatography (GPC) using polyethylene glycol of known molecular weight as a standard substance. Outside this molecular weight range, synergistic corrosion and scale inhibiting effects will not be exhibited.

The copolymers of the present invention may be in unneutralized acid form,
It may also be in the form of a water-soluble salt.

The water-soluble salts used here are those in which part or all of the protons of the sulfonic acid group and/or carboxyl group are substituted with alkali metals, alkaline earth metals, zinc, ammonia, and/or amines, etc. Refers to something that can be dissolved at certain concentrations.

The preferred blending ratio of the inhibitor of the present invention is (a) 10 to 80% by weight of the water-soluble organic phosphorus compound, (b) 10 to 70% by weight as the total amount of the water-soluble zinc salt and molybdate,
(C) 10 to 50% by weight of the water-soluble copolymer, more preferably (a) 46 to 65%, (b) 20 to 50%,
(c) In the range of 15-30%.

In the present invention, each component of the inhibitor may be added to the system alone, or may be added as a preparation with other compounds as necessary. These compounds and formulations are injected continuously or intermittently to maintain sufficient concentrations within the system to simultaneously achieve corrosion, scale, and fouling control.

The amount of water-soluble cloth $17 added is 0.2 to 30
ppm, more preferably 1 to 10 ppm1 The amount of water-soluble zinc salt and molybdate added is 0.2 to 30 ppm, more preferably 1 to 10 p as the total amount of Zn and MO.
pm, and the amount of the copolymer added is preferably 0.2 to 1100 ppm, more preferably 0.5 to 30 ppm.

It is also possible to add to the inhibitor according to the invention at least one of the chemicals known as further corrosion inhibitors and scale inhibitors. Examples of these chemicals include chromates, dichromates, anhydrous chromates, orthophosphoric acid and its water-soluble salts, polymerized phosphoric acid and its water-soluble salts, tungstates, nitrites, silicates, organic Phosphoric acid esters and their water-soluble salts, lignyline sulfonates, tannins, water-soluble cellulose gums such as carboxymethylcellulose and sulfonated cellulose, hydroxy acids such as citric acid, malic acid, ccurconic acid, and glucoheptonic acid, 1 ton
2t3 1'lyazole, 1,2,3-benzotriazole, tolyltriazole (i.e. 4-methyl-1,
Triazoles such as H-benzotriazole and 5-methyl-1,H-benzotriazole), 4-carboxy-1,H-benzotriazole, 4-nitro-1°H-benzotriazole, 2-mercaptobenzothiazole, 5 -chloro-2-methicaptobenzothiazole,
2-(3)-aminopropyl)-benzothiazole, 2
Thiazoles such as -(21-amino-2I-methylpropyl)-benzothiazole, 2-(51-aminopentyl)benzimidazole, 2-(2" -7mi/-2
Examples include imidazoles such as 1-methylpropyl)-bezimidazole, 2-ethyl-4-methyl-imidazole, 2-ethylimidazole, and 2-methylimidazole.

E. Examples Next, the present invention will be explained in more detail with reference to Examples.0 [Example 1. (a) Test piece A 1n thick piece of rolled steel for general structures (JIS 88-41) is cut into a disk with an outer diameter of 50tm, and a hole with a diameter of 8mm for fixing is drilled in the center. Remove dirt from the surface of the test piece and polish the entire surface with No. 320 abrasive paper.

This was washed and degreased with A7Ton, dried, and weighed accurately to 0.1"P.

(b) Test method Immerse the test piece in 500 ml of test water at 1100 rpm.
I rotated it. The water quality of the test water is pHs, 0 to 9.0.
Oa hardness 100 ppm, Mg hardness 50 ppm%M
- Alkalinity 120 ppm. The test water to which the compounds shown in Table 1 were added was maintained at 50°C, and the test time was 18
It was time. After the test, the test piece was washed with water using a nylon brush, dried, and weighed accurately to 0.119.

The results are shown in the rightmost column of Table 1 based on the weight loss of the test piece before and after the test.

[Example 2] The dissolution and dispersion performance of the inhibitor in the present invention for calcium and zinc was evaluated.

Calcium chloride, sodium bicarbonate, and zinc sulfate were dissolved in deionized water to prepare test water with the following water quality: Ca hardness 480 ppm, HOOs 300 ppm.
(Oaoog Toshite), the compounds shown in Table 2 were added to 10 ppm Zn test water, and the pH of the test water was adjusted to 8.7. The test solution was placed in a sealed container and allowed to stand in a constant temperature bath at 50° C. for 3 days, and then the test water was filtered through quantitative P paper/166, and the calcium and zinc concentrations were measured by atomic absorption spectrometry.

The results are shown in Table-2.

In the formula: C: Calcium concentration after the test in the test water to which the test compound was added C: Calcium concentration after the test in the test water without the test compound added CO: Initial concentration of calcium Examples 1 and 2 The weight average molecular weight (G
PO, polyethylene glycol standard) are both 460
It was within the range of 0 to a800.

[Example 3] A test cooling tower with a holding water capacity of 30% and a total length of 50%! Four double-tube test heat exchangers were connected in series and circulated by a centrifugal pump at a water flow rate of 0.5 m/S. The material of the heat exchanger tube for the test was carbon steel (JISSTPG, outer diameter 12
．． 7sm) and Admiralty brass (outer diameter 12.7mm)
) and insert an electric heater inside the heat transfer tube to generate 3QO.
A heat flux of OOKcal/h was applied to heat the circulating water and the outlet temperature of the cooling water was adjusted to 45°C. The amount of evaporated water in the cooling tower is 2. Blowdown is performed using a metering pump so that the concentration of the circulating water is constant at O1/h, and the compounds shown in Table 3 are supplied using a chemical feeder so that the concentration of chemicals in the circulating water is constant. Maintained. The test period is 15 days. After the test was completed, the test heat exchanger tube was dried and weighed, and then the deposits were removed and weighed again. Judgment power of results: Here Ll: Weight of test heat exchanger tube before test [ri] L2
: Weight of test heat exchanger tube after test [■] L3: Weight of test heat exchanger tube after removing deposits [~] Sl: Surface area of test heat exchanger tube (dm”) S
2: Surface area of test heat exchanger tube (d)D:
Test Period: Day C] For the first two days of the test, initial high concentration treatment was performed at a concentration three times the test concentration shown in Table 1.

The quality of circulating water is pH 8.9 and electrical conductivity 700 μs/a.
m, M alkalinity 150 ppm, total hardness 300 t'p
pm% Oa hardness 200 ppm, silica 64 ppm,
The chloride ion content was 72 ppm.

The concentration of circulating water was 4.

The results are shown in Table-3.

As is clear from Tables 1 and 3, the corrosion inhibitor of the present invention containing a phosphonic acid, a zinc salt, and a copolymer is a comparative example lacking any one of the phosphonic acid, the zinc salt, and the copolymer. Compared to this, the corrosion prevention effect due to the synergistic effect of the three is remarkable, and the amount of deposits attached decreases in inverse proportion to this effect.

In addition, acrylic acid and N-
It is clear from Tables 2 and 3 that when a copolymer with substituted acrylamide is used instead of the copolymer of the present invention, the corrosion prevention effect and scale prevention effect are significantly inferior.

HEDP: 1-hydroxyethylidene-1,1-diphosphonic acid PBTC: 2-phosphonobutane-1,2,4-)licarponic acid PCA: Reactant of acrylic acid and hypophosphorous acid represented by the following formula (reaction molar ratio 4 :1) By the way, m and n are integers of 1 or more, and the total of m and n is about 4.

AA Niacrylic acid DMA#n: N, N-dimethylacrylamide IPn: N-1s□-propylacrylamide TBA
Jin: N tert-butylacrylamide middle behavior: N, N-diethylacrylamide DIP: N,
N-G 1so-propylacrylamide ACMO: acryloylmo/l/holin AM'PS: 1
-Acrylamide-2-methylpropylacrylamide ACPP: N-acryloylpiperidine ACPR:
N-acryloylpyrrolidine D)lPAAm: N
, N-di(2-hydroxypropyl)acrylamide: N-methyl-N-(2-hydroxyethyl)acrylamide F0 Effects of the Invention According to the corrosion inhibitor that also functions as scale control of the present invention, cooling water systems, etc. Corrosion prevention of metal materials, especially heat exchangers and piping made of carbon steel, in water systems containing Not only are the concentrations of acid, copolymer and zinc economically achieved, but all secondary scale deposition problems due to phosphonic acids are eliminated, minimizing the concentration of phosphorus and zinc in the wastewater. Not only is this possible, but it also has great effects on operational ease, such as eliminating the need for pH adjustment by adding acid.

Claims (1)

[Scope of Claims] 1. (a) at least one water-soluble organic phosphorus compound having a carbon-phosphorus bond and selected from the group consisting of water-soluble organic phosphonic acids and water-soluble organic phosphinic acids; (b) At least one salt selected from the group consisting of water-soluble zinc salts and molybdates; and (c) a water-soluble copolymer containing (meth)acrylic acid and N-substituted (meth)acrylamide as constituent units. and the N-substituted (meth)acrylamide has the formula; ▲There are mathematical formulas, chemical formulas, tables, etc.▼ [In the formula, R_1 is hydrogen or a methyl group, and R_2 and R_
3 is each independently hydrogen or an alkyl group having 1 to 4 carbon atoms, and the total number of carbon atoms of R_2 and R_3 is 2 to 6. ] At least one member selected from the group consisting of monomers represented by and (meth)acryloylmorpholine, and the composition ratio of the N-substituted (meth)acrylamide in the copolymer is 10 to 70% by weight. An inhibitor that simultaneously prevents corrosion and scaling of metals in an aqueous system, characterized in that it contains a certain copolymer as an active ingredient. 2. At least one water-soluble organic phosphonic acid selected from the group consisting of 1-hydroxyethylidene-1,1-diphosphonic acid, 2-hydroxyphosphonoacetic acid, and 2-phosphonobutane-1,2,4-tricarboxylic acid The inhibitor according to claim 1, which is 3. Water-soluble organic phosphinic acid has the formula; ▲There are mathematical formulas, chemical formulas, tables, etc.▼ [In the formula, R_1 and R_6 are each independently -H, -OH
, is an alcohol residue having 1 to 4 carbon atoms or a ketone residue having 3 to 4 carbon atoms, R_2, R_3, R_4, and R_5 represent hydrogen or a carboxy group, and R_2 and R_3 cannot be hydrogen at the same time, The same applies to R_4 and R_5, and m and n each represent an integer from 1 to 20. ] The inhibitor according to claim 1, which is represented by: 4. The water-soluble copolymer has a weight average molecular weight of 1000
The inhibitor of claim 1 in the range of 100,000 to 100,000. 5. The first water-soluble copolymer is a copolymer containing (meth)acrylic acid, N-substituted (meth)acrylamide, and monoethylenically unsaturated sulfonic acid monomer as constituent units.
The inhibitor according to the claims. 6. A method for simultaneously preventing corrosion and scaling of metals in an aqueous system, comprising each component (a) according to claim 1,
A method characterized in that (b) and (c) are added to the aqueous system either alone or after being blended as a composition.