JP2001252692A - Calcium carbonate-base scale preventive agent and method of manufacturing copolymer for calcium carbonate-base scale preventive agent - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a calcium carbonate scale preventive agent which consists of a copolymer (salt) capable of suppressing the adhesion of scale of an aqueous system and more particularly scale of a calcium carbonate system as an effective component. SOLUTION: This calcium carbonate-base scale preventive agent contains a copolymer which is obtained by aqueous solution polymerization of (a) 70 to 98 wt.% at least one monomer selected from maleic acid, maleic anhydride, phthalic acid and itaconic acid and (b) a monomer consisting of 2 to 30 wt.% water-soluble monomers exclusive of (a) and is a number average molecular weight of 400 to 1,000 or its salt.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a calcium carbonate-based scale inhibitor containing, as an active ingredient, a copolymer (salt) capable of suppressing the adhesion of an aqueous scale, particularly a calcium carbonate-based scale.

[0002]

2. Description of the Related Art Conventionally, alkaline earth metal scales, especially calcium carbonate scales, are formed on a vessel wall which comes into contact with water, such as a cooling water system or a boiler water system, particularly on an electrically heated surface. In particular, in the open-circulation type cooling water system, from the viewpoint of resource saving and energy saving, disposal (blowing) of cooling water outside the system
In the case of performing a high concentration operation while reducing the concentration, dissolved salts are highly concentrated, and calcium carbonate salts having low solubility are scaled. Heretofore, various proposals have been made as a scale inhibitor for preventing or removing such a calcium carbonate scale. For example, JP-A-2
No. 209908 discloses a scale inhibitor containing polymaleic acid and a salt thereof as a main component.
No. 20 is a scale inhibitor which comprises a copolymer of maleic anhydride and an aliphatic diene, and JP-A-5-2950.
No. 33 is a scale inhibitor mainly composed of a copolymer of maleic acid and another water-soluble polymer.
No. 36922 discloses a scale inhibitor mainly composed of a maleic acid copolymer obtained by bulk polymerization of maleic anhydride and maleic acid or fumaric acid ester. These scale inhibitors can suppress calcium carbonate-based scale itself to some extent, but polyvalent ions such as Ca ions present in the cooling water and the (co) polymer undergo gelation or insolubilization due to complexing action, as a result,
By using elementary materials continuously for a long period of time,
There has been a problem that a phenomenon such as a decrease in heat exchange ability due to adhesion to an electrically heated surface is observed.

[0003]

DISCLOSURE OF THE INVENTION The present invention has been made to solve the conventional problems, and has the same calcium carbonate scale inhibiting ability as a conventional scale inhibitor and a polyvalent metal such as calcium ion. An object of the present invention is to provide a calcium carbonate-based scale inhibitor that is hardly insoluble or gelated with ions.

[0004]

The present invention relates to (a) 70-98% by weight of at least one monomer selected from maleic acid, maleic anhydride, fumaric acid and itaconic acid; and (b) a monomer other than (a). A copolymer having a number average molecular weight in the range of 400 to 1,000 (hereinafter, referred to as a copolymer) obtained by aqueous polymerization of a monomer composed of 2 to 30% by weight of a water-soluble monomer.
Or "a specific copolymer") or a salt thereof.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The specific copolymer used for the calcium carbonate scale inhibitor of the present invention will be described.
The monomer of the component (a), which is one component of the specific copolymer, includes:
It is at least one monomer selected from maleic acid, maleic anhydride, fumaric acid and itaconic acid. These monomers may be used in the form of a carboxylic acid or in the form of a carboxylate, and are preferably an acid or a monomer in which 30 mol% or less of the carboxylic acid is a salt. Particularly preferred monomers include maleic anhydride,
And maleic acid. Another component (b)
Examples of the component monomers include water-soluble monomers,
Sulfonic acid group-containing monomers, amide group-containing monomers,
(Meth) acrylic acid monomers, hydroxyl group-containing monomers, polyoxyethylene group-containing monomers, and the like.

The sulfonic acid group-containing monomer is not particularly limited as long as it is a monomer containing a sulfonic acid group and having a polymerizable double bond. For example, a conjugated diene sulfone represented by the following general formula (I) Acids (eg, 2-methyl-
1,3-butadiene-1-sulfonic acid)

[0007]

Embedded image (Wherein, R ^{1 to} R ⁶ are a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, an aryl group having 6 to 20 carbon atoms or —SO ₃ X, wherein X is a hydrogen atom, a metal atom, ammonium Or at least one of R ^{1 to} R ⁶ is —SO ₃ X) or the following general formula (II)
(E.g., 3-allyloxy-2-hydroxypropanesulfonic acid, 3-methallyloxy-2-hydroxypropanesulfonic acid)

[0008]

Embedded image ..... (II)

[Wherein R ⁷ is a hydrogen atom or a carbon atom having 1 to
8 represents an alkyl group, ad is the same or different, and 0
Or an integer of 1 to 100 (however, a + b + c +
d = 0 to 100), the OC ₂ H ₄ unit and the OC ₃ H ₆ unit are bonded in an arbitrary order, Y and Z are sulfonic acid groups or hydroxyl groups, and at least one of Y and Z is sulfonic acid. Group. ] (Meth) acrylamido-2-methylpropanesulfonic acid, 2-hydroxy-3-acrylamidopropanesulfonic acid, styrenesulfonic acid, methallylsulfonic acid, vinylsulfonic acid, allylsulfonic acid, isoamylenesulfonic acid, or a mixture thereof And the like. Preferably, 2-methyl-1,3-butadiene-1-sulfonic acid, (meth) acrylamido-2-methylpropanesulfonic acid, 3- (meth) allyloxy-2-hydroxypropanesulfonic acid, styrenesulfonic acid, or these These salts are good.

The monomer having an amide group is not particularly limited as long as it is a monomer having an amide group and having a polymerizable double bond. For example, (meth) acrylamide, dimethyl (meth) acrylamide, monomethyl ( Examples thereof include (meth) acrylamide, diethyl (meth) acrylamide, and isopropyl (meth) acrylamide. Further, the monomer having a hydroxyl group is not particularly limited as long as it is a monomer having a hydroxyl group and having a polymerizable double bond, for example, vinyl alcohol, allyl alcohol, methyl vinyl alcohol, ethyl vinyl alcohol, vinyl glycolic acid And hydroxyl-containing (meth) acrylates such as hydroxymethyl (meth) acrylate, hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate and glycerol mono (meth) acrylate.

The monomer having a polyoxyethylene chain is not particularly limited as long as it is a monomer having a polyoxyethylene chain and having a polymerizable double bond.
For example, (alkoxy) polyethylene glycol mono (meth) acrylate, (alkoxy) polypropylene glycol mono (meth) acrylate, (alkoxy)
Polyethylene glycol polypropylene glycol mono (meth) acrylate, (alkoxy) polyethylene glycol polytetramethylene glycol mono (meth) acrylate, (alkoxy) polypropylene glycol polytetramethylene glycol mono (meth) acrylate, polyoxyethylene (meth) allyl ether, poly Oxypropylene (meth) allyl ether and the like can be mentioned. Preferred are (alkoxy) polyethylene glycol mono (meth) acrylate and polyoxyethylene (meth) allyl ether. These water-soluble monomers of component (b) may be used alone or in combination of two or more.

The amount of the monomer (a) used is 70 to 98% by weight, preferably 80 to 95% by weight, and more preferably 85 to 90% by weight in the specific copolymer.
When the amount of the component (a) is less than 70% by weight, the ability of the obtained specific copolymer to inhibit calcium carbonate scale is not sufficient. On the other hand, when the amount exceeds 98% by weight, gelation and insolubilization are caused by polyvalent ions such as calcium. This is not preferred.
The weight average molecular weight of the specific copolymer composed of the component (a) and the component (b) is 400 to 1,000, preferably 450 to 800, and more preferably 500 to 700. If the weight-average molecular weight is less than 400, the calcium carbonate-based scale-inhibiting ability decreases, which is not preferable. On the other hand, if the weight-average molecular weight exceeds 1,000, gelation and insolubility tend to occur due to polyvalent ions such as calcium, which is not preferable.

The specific copolymer of the present invention can be obtained by copolymerizing the components (a) and (b) in an aqueous solution using a radical polymerization initiator. Examples of the polymerization initiator that can be used here include azo 例 え ば -based initiators such as hydrogen peroxide, sodium persulfate, potassium persulfate, and 2,2′-azobis (2-amidinopropane) hydrochloride; Reaction temperature, usually in the range of 20 to 200C, preferably 40 to 150C, in the presence of a known radical polymerization initiator such as -butylhydroperoxide.
The specific copolymer can be produced by a polymerization reaction for 1 to 20 hours. The amount of the radical polymerization initiator to be used is generally 0.1 to 50% by weight, preferably 1 to 10% by weight, based on all monomer components.

In the copolymerization, it is preferred that the monomer (a) and water are first charged into a reactor, the temperature is raised to a required temperature, and then the monomer (b) is successively added. The time required for the sequential addition can be appropriately selected depending on the type of the monomer used, but is usually 1 to 20 hours. Further, it is preferable that the radical initiator be sequentially added as in the case of the component (b). In the present invention, the solid concentration at the time of polymerization is usually 5 to 60% by weight. The pH of the aqueous solution at the time of polymerization is 0.3 to 3.0, and preferably,
0.4 to 1. Particularly preferably, the pH is 0.4 to 0.7 so that the carboxylic acid monomer and the sulfonic acid monomer used as the monomer of the component (a) and the monomer of the component (b) can be polymerized in an acid form.
When the pH of the aqueous solution at the time of polymerization exceeds 3, gelling and insolubility tends to occur due to polyvalent ions such as calcium, and it is not preferable. When the pH is less than 0.3, it is necessary to add a strong acid to lower the pH. It is not only economically cost-effective, but also unfavorable because there is no corresponding effect.

In the above polymerization reaction, if necessary, a polymerization solvent other than water can be used in combination to smoothly carry out the reaction. Examples of the polymerization solvent include methanol, ethanol, propyl alcohol and butanol. Alcohols, aromatic hydrocarbons such as benzene, toluene, xylene and ethylbenzene, n-pentane and n-
Examples thereof include aliphatic hydrocarbons such as hexane, cyclohexane, n-heptane, and octane; and ethers such as diethyl ether, tetrahydrofuran, and 1,4-dioxane. Here, when a polymerization solvent other than water is used in combination, the content is 30% by weight or less of water.

When the specific copolymer used in the present invention is a salt, the cationic species is not particularly limited, but may be hydrogen, an alkali metal, an alkaline earth metal, ammonium,
Amines and the like are preferred. Examples of the alkali metal include sodium and potassium, examples of the alkaline earth metal include calcium and magnesium, and examples of the amine include methylamine, ethylamine, propylamine, dimethylamine, diethylamine, triethylamine, butylamine, dibutylamine, and tributylamine. And polyamines such as ethylenediamine, diethylenetriamine and triethylenetetramine, morpholine, piperidine and the like. It is preferable that 70 mol% or more of the total acid groups of the carboxyl group or the sulfonic acid group is in a hydrogen form, more preferably 90%.
More than mol% is in the hydrogen form.

The calcium carbonate-based scale inhibitor of the present invention can be used as it is or dissolved in water or the like, for boiler water-based,
It is added to water systems such as geothermal water systems, open or closed circulation cooling water systems, and transient cooling water systems to prevent scale. The amount of the calcium carbonate-based scale inhibitor of the present invention varies depending on the concentration of polyvalent ions such as calcium in the target aqueous system.
It is about 200 mg / L. The calcium carbonate-based scale inhibitor of the present invention suppresses the formation of calcium carbonate-based scale in the target aqueous system, and is less likely to gel and insolubilize with respect to polyvalent ions. . Other scale inhibitors, anticorrosives, slime inhibitors and the like can be used in combination with the scale inhibitor of the present invention.

[0018]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to the following examples. The percentages and parts in the examples are on a weight basis unless otherwise specified. Further, the weight average molecular weight (Mw) in the examples is obtained by converting the result determined by gel permeation chromatography (GPC) using a calibration curve prepared using sodium polystyrene sulfonate as a standard sample. Here, the measurement conditions of GPC are as follows. Column: G3000PWXL [manufactured by Tosoh Corporation] Column: GMPWXL [manufactured by Tosoh Corporation] Column: GMPWXL [manufactured by Tosoh Corporation] The columns are connected in series in the order of 〜, and a sample is introduced from the column side. Detector: Differential refractometer RI-8021 [Tosoh Corporation
Eluent: water / acetonitrile / sodium sulfate = 2,1
00/900/15 (weight ratio) Flow rate; 1.0 ml / min Temperature; 40 ° C. Sample concentration; 0.2% Sample injection volume; 400 μl

REFERENCE EXAMPLE 1 316 g of water and maleic anhydride 32 were placed in a 2 L container.
4 g were charged. After the internal temperature was raised to 100 ° C. and maleic anhydride was completely dissolved, 120 g of a 30% aqueous solution of acrylamido-2-methylpropanesulfonic acid, 80 g of a 30% aqueous hydrogen peroxide solution, and 40 g of a 30% sodium persulfate solution
While maintaining the internal temperature at 100 ° C. and pH 0.3-0.6.
It was added sequentially over time. After addition, continue stirring for 2 hours,
A specific copolymer A was obtained. As a result of GPC analysis, almost 100% of the monomer had disappeared. The weight average molecular weight of the obtained specific copolymer was 720.

Reference Example 2 In Reference Example 1, a 30% aqueous solution of acrylamide-2-methylpropanesulfonic acid was replaced with a 30% aqueous solution of acrylamide.
The procedure was performed in the same manner as in Reference Example 1 except that the aqueous solution was replaced. The pH during the polymerization was 0.4 to 0.5. The weight average molecular weight of the specific copolymer was 700. The obtained specific copolymer is referred to as specific copolymer B. Reference Example 3 In Reference Example 1, 120 g of a 30% aqueous solution of acrylamido-2-methylpropanesulfonic acid was added to 3 g of acrylic acid.
It carried out similarly to Reference Example 1 except having replaced with 240 g of 0% aqueous solutions. The pH during the polymerization was from 0.4 to 0.5. The weight average molecular weight of the specific copolymer was 650. The obtained specific copolymer is referred to as specific copolymer C. Reference Example 4 The same operation as in Reference Example 1 was carried out except that in Example 1, 120 g of a 30% aqueous solution of acrylamido-2-methylpropanesulfonic acid was changed to 240 g of a 30% aqueous solution of polyethylene glycol monoallyl ether. PH during polymerization
Was from 0.4 to 0.5. The weight average molecular weight of the specific copolymer was 550. The obtained specific copolymer is referred to as specific copolymer D.

Reference Example 5 The procedure of Reference Example 1 was repeated, except that 120 g of a 30% aqueous solution of acrylamido-2-methylpropanesulfonic acid was replaced with 240 g of a 30% aqueous solution of glycerin monoallyl ether. The pH during the polymerization was from 0.4 to 0.5. The weight average molecular weight of the copolymer was 600. The obtained copolymer is called copolymer E. Reference Example 6 The procedure of Reference Example 1 was repeated, except that 324 g of maleic anhydride was replaced with 360 g of maleic acid.
The pH during the polymerization was 0.3 to 0.5. The weight average molecular weight of the copolymer was 650. The obtained copolymer is called copolymer F. Reference Example 7 The same operation as in Reference Example 1 was carried out except that 324 g of maleic anhydride was replaced with 324 g of itaconic acid.
The pH during the polymerization was 0.3 to 0.5. The weight average molecular weight of the specific copolymer was 700. The obtained specific copolymer is referred to as specific copolymer G. Reference Example 8 In Reference Example 1, 324 g of maleic anhydride was added to 238 g.
, And 120 g of a 30% aqueous solution of acrylamido-2-methylpropanesulfonic acid was replaced with a 30% aqueous solution of acrylamido-2-methylpropanesulfonic acid.
The same operation was performed as in Reference Example 1 except that the amount was changed to 08 g. The pH during the polymerization was from 0.3 to 0.6. The weight average molecular weight of the specific copolymer was 950. The obtained specific copolymer is referred to as specific copolymer Z.

REFERENCE EXAMPLE 9 In Reference Example 1, 80 g of 30% hydrogen peroxide solution and 40 g of 30% sodium persulfate were added to 30% hydrogen peroxide solution 1
The same operation was performed as in Reference Example 1 except that the amount was changed to 20 g. The pH during the polymerization was 0.3 to 0.5. The weight average molecular weight of the specific copolymer was 1,400. The obtained specific copolymer is referred to as specific copolymer Y. Reference Example 10 In a container having an inner volume of 2 L, 640 g of water and 32 maleic anhydride were added.
4 g and 216 g of sodium hydroxide were charged. 1 internal temperature
After the temperature was raised to 00 ° C and the maleic anhydride was completely dissolved, 30% of acrylamido-2-methylpropanesulfonic acid was added.
120 g of an aqueous solution, 80 g of a 30% hydrogen peroxide solution, and 3
40 g of 0% sodium persulfate was sequentially added over 8 hours while maintaining the internal temperature at 100 ° C. After the addition, stirring was continued for 2 hours. As a result of GPC analysis, almost 100% of the monomer was
Had disappeared. The pH at the time of the polymerization was 3.5 to 3.8. The weight average molecular weight of the specific copolymer was 1,000. The obtained specific copolymer is referred to as a specific copolymer X. Reference Example 11 In a container having an inner volume of 2 L, 316 g of water and 32 maleic anhydride were added.
4 g and 120 g of a 30% aqueous solution of acrylamido-2-methylpropanesulfonic acid were charged. After raising the internal temperature to 100 ° C., 80 g of 30% aqueous hydrogen peroxide and 40 g of 30% sodium persulfate were successively added over 8 hours while maintaining the internal temperature at 100 ° C. After the addition, stirring was continued for 2 hours. As a result of GPC analysis, almost 100% of the monomer had disappeared. The pH during the polymerization was from 0.3 to 0.6. The weight average molecular weight of the specific copolymer was 900. The obtained specific copolymer is referred to as specific copolymer W.

Test Example Using the specific copolymer obtained in the above Reference Example, the calcium carbonate-based scale inhibiting ability and the permissible concentration of calcium insolubilization were measured by the following methods. Table 1 shows the results. 1) Calcium carbonate-based scale inhibitory capacity 200 g of distilled water was put into a 500 ml conical beaker, 5 ml of a 2.5% calcium carbonate solution was added with stirring with a stirrer, and then 1 ml of the scale inhibitor (100 ppm) of the present invention was added. . Then, after adding 5 ml of a 2.5% sodium hydrogen carbonate solution, the pH was adjusted to 8.5.
Is adjusted in a small amount with a 微量 aqueous solution of sodium hydroxide. Total content of conical beaker is 50
After adding distilled water so that the amount becomes 0 g and closing the lid, 6
Let stand in a thermostat at 0 ° C. for 20 hours. After standing, the supernatant was filtered with a 0.1 micron membrane filter. Take 8 ml of the filtrate into a 50 ml volumetric flask, add 5 ml of 5N hydrochloric acid and 1 ml of lanthanum chloride, and add 50 ml of distilled water.
I tried to be. The calcium concentration of this solution was determined by atomic absorption analysis. The calcium suppression rate was determined from the following equation. Calcium precipitation inhibition rate (%) = (actually measured calcium concentration) / (prepared calcium concentration) × 100

2) Measurement of permissible concentration of calcium insolubilization Using a 300 ml Erlenmeyer flask, a copolymer (salt) concentration of 1
Adjust so as to be 00 mg / L, calcium concentration (adjusted by calcium chloride dihydrate) 40 mg / L, and total amount to 200 ml. At this time, the pH of the aqueous solution is adjusted to 8.6 with a borate buffer. Immediately after storage in a water bath at 90 ° C. for 1 hour, the absorbance at 380 nm was measured using a spectrophotometer U.
1100 (manufactured by Hitachi, Ltd.). Calcium concentration of 100, 200, 300, 400, 500, 6
The amount was changed to 00 mg / L, and the absorbance was measured in the same manner as described above. The minimum calcium concentration at which the absorbance exceeded 0.01 was taken as the permissible concentration of calcium insolubilization.

[0025]

[Table 1]

From the results in Table 1, it can be seen that the calcium carbonate-based scale inhibitor of the present invention having a very narrow specific molecular weight range and a specific composition range is excellent in calcium carbonate-based scale-inhibiting ability and has a permissible calcium insolubilizing concentration. , The gelation and insolubilization of polyvalent ions are difficult.

[0027]

Industrial Applicability The scale inhibitor of the present invention is an excellent calcium carbonate scale inhibitor which has excellent calcium carbonate scale inhibiting ability and is hardly gelled or insolubilized by polyvalent ions.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08F 2/10 C08F 2/10 222/04 222/04 (72) Inventor Koichi Onoe Tsukiji Chuo-ku, Tokyo F-term (reference) No. 11-24, JSR Co., Ltd. 4J011 EA08 EC01 HA02 HA04 HB14 4J100 AB07Q AD01Q AD02Q AD03Q AE18Q AE26Q AJ08P AJ09P AK18P AK32P AL08Q AL09Q AM15Q AM17Q AM19Q AM19BA01 BA01Q01

Claims (4)

[Claims] 1. (a) 70 to 98% by weight of at least one monomer selected from maleic acid, maleic anhydride, fumaric acid and itaconic acid and (b) 2 to 30% by weight of a water-soluble monomer other than (a) A calcium carbonate-based scale inhibitor comprising a copolymer having a number average molecular weight of 400 to 1,000 or a salt thereof, obtained by aqueous polymerization of a monomer comprising 2. The method according to claim 1, wherein the component (b) is at least one selected from a sulfonic acid group-containing monomer, an amide group-containing monomer, a (meth) acrylic acid monomer, a hydroxyl group-containing monomer and a polyoxyethylene group-containing monomer. The calcium carbonate-based scale inhibitor according to claim 1, 3. (a) 70 to 98% by weight of at least one monomer selected from maleic acid, maleic anhydride, fumaric acid and itaconic acid and (b) 2 to 30% by weight of a water-soluble monomer other than (a) A monomer consisting of
The method for producing a copolymer for calcium carbonate inhibitor according to claim 1, wherein the aqueous solution polymerization is performed in the range of H 0.3 to 3. 4. The calcium carbonate-based scale inhibitor according to claim 3, wherein the component (b) is sequentially added to the component (a) when the component (a) and the component (b) are polymerized. A method for producing a copolymer.