JPS6260000B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to scale inhibitors.
More specifically, it is an inhibitor of scale that occurs due to the deposition of metal salts on the heat transfer surfaces and pipes of cooling water systems such as water-cooled industrial heat exchangers, or heating evaporation systems such as boilers and evaporative desalination equipment. It is related to. Water supplied to cooling water systems such as water-cooled industrial heat exchangers, industrial water used in boilers and evaporative desalination equipment, seawater, natural salt water, etc., and dust collection water generated at steel plants, etc., contain calcium, Contains dissolved ions that tend to form relatively insoluble metal salts, such as magnesium, zinc, and iron. In the cooling water system, in recent years, in order to save and use water effectively, some of the circulating water has been evaporated and replenished as it passes through the cooling tower, but this is because the circulating water is used repeatedly over a long period of time. At this time, the ions dissolved in the make-up water that tend to form the relatively poorly soluble metal salts mentioned above are concentrated in the circulating water and deposited as metal salts on the heat transfer surface of the heat exchanger. It becomes a scale. In addition, in boilers, evaporative desalination equipment, etc., as a result of salt concentration and heating associated with water evaporation, relatively insoluble metal salts such as those mentioned above and reaction products due to heating are deposited on heat transfer surfaces, etc. It adheres and becomes scale. Furthermore, collected dust water generated at steel works, etc.
After removing suspended solids, the water is reused as dust collection water, but since it is difficult to completely remove the relatively insoluble metal salts mentioned above, it is difficult to completely remove the relatively insoluble metal salts mentioned above. Precipitates and adheres as scale. Such scale adhesion inhibits heat transfer on heat transfer surfaces, increases pressure loss in the cooling water system, reduces cooling efficiency, reduces the effectiveness of corrosion inhibitors, and causes localized corrosion. This can lead to serious problems such as blockages in the water circulation system and leakage accidents due to corrosion, which require unscheduled suspension of operations. Conventionally, various scale inhibitors have been used for the purpose of preventing such scale precipitation and adhesion. As such scale inhibitors, lignin derivatives such as sodium lignin sulfonate, sodium poly(meth)acrylate, or phosphorus compounds such as inorganic polyphosphates, phosphonates, and organic phosphate esters are used. There is. However, since the lignin derivative is a natural product, it is difficult to obtain one of a constant quality, and the effects of sodium poly(meth)acrylate are not fully satisfactory. On the other hand, phosphorus compounds act not only as scale inhibitors but also as corrosion inhibitors, and are used alone or in combination with polyvalent metal salts such as zinc salts and nickel salts. However, phosphorus compounds easily hydrolyze in circulating water, reducing their anti-corrosion effect, and reacting with calcium ions, magnesium ions, etc. dissolved in circulating water to produce poorly soluble salts that precipitate and adhere. and scale it. In addition, when phosphorus compounds are used together with polyvalent metal salts such as zinc salts and nickel salts, polyvalent metal ions precipitate as hydroxides, phosphates, phosphonates, etc. in alkaline circulating water with a high pH. Precipitation not only reduces the concentration of polyvalent metal ions, making it impossible to exhibit sufficient corrosion protection, but also causes problems such as scale adhesion. The present inventors have arrived at the present invention as a result of intensive studies to solve the various problems of conventional scale inhibitors as described above. Therefore, an object of the present invention is to provide a scale inhibitor that has excellent scale prevention effects and can fully exhibit its excellent performance even when used in combination with various known corrosion inhibitors and other water treatment agents. That is, the present invention is derived from (meth)acrylic acid and/or its salt () and sulfoethyl (meth)acrylate and/or its salt () as main components, and the monomer () and the monomer body()
The present invention relates to a scale inhibitor comprising a copolymer (A) having a molar ratio of 85:15 to 15:85. (meth)acrylic acid and/or used in the present invention
Examples of salts thereof include acrylic acid, methacrylic acid, and metal salts, ammonium salts, and organic amine salts of these acids. One or more of these can be used. Furthermore, examples of sulfoethyl (meth)acrylate and/or its salts include sulfoethyl esters of acrylic acid and methacrylic acid, and metal salts, ammonium salts, and organic amine salts of these acids. One or more of these can be used. Furthermore, when producing the above-mentioned copolymer (A), there is no problem in copolymerizing a third component within a range that does not significantly reduce its performance. The proportion thereof is preferably 40 mol% or less of the total. That is, the third component is (meta)
Esters obtained from acrylic acid and alcohol,
Examples include hydroxyethyl (meth)acrylate, (meth)acrylamide, and vinyl acetate. Copolymer (A) is derived from monomers () and () as main components, and the molar ratio of monomer () and monomer () is 85:15 to 15:85. If the ratio is outside this range, a scale inhibitor with excellent performance cannot be obtained. In order to produce the copolymer (A), the monomer components may be copolymerized using a polymerization initiator. Copolymerization can be carried out by various methods such as polymerization in a solvent or bulk polymerization, but polymerization in a solvent is more preferable from the viewpoint of ease of controlling the reaction. Polymerization in a solvent can be carried out either batchwise or continuously. In this case, various solvents can be selected as the solvent to be used, but in view of the solubility of the monomers () and () in the solvent, water and lower alcohols are preferred because they are easy to handle.
It is particularly preferable to use water as a solvent in terms of solubility and ease of handling. When polymerization is carried out in an aqueous medium, a water-soluble polymerization initiator such as ammonium or alkali metal persulfate or hydrogen peroxide is used as the polymerization initiator. At this time, an accelerator such as sodium hydrogen sulfite can also be used in combination. In addition, when lower alcohols or other solvents are used, peroxides such as benzoyl peroxide and lauroyl peroxide; hydroperoxides such as cumene hydroperoxide; and aliphatic azo compounds such as azobisisobutyronitrile are polymerized. Used as an initiator. At this time, a promoter such as an amine compound can also be used in combination. Furthermore, when a water-lower alcohol mixed solvent is used, it can be appropriately selected from among the various polymerization initiators or combinations of polymerization initiators and accelerators mentioned above. The polymerization temperature is appropriately determined depending on the solvent and polymerization initiator used, but it is usually carried out within the range of 0 to 120°C. The copolymer (A) thus obtained can be used as it is as a scale inhibitor in the present invention, but it may be further neutralized with an alkaline substance if necessary. Preferred examples of such alkaline substances include hydroxides, chlorides, or carbonates of monovalent metals or divalent metals; ammonia; and organic amines. The scale inhibitor of the present invention is sufficiently effective when used alone, but if necessary, other scale inhibitors such as lignin derivatives such as sodium lignin sulfonate, phosphorus compounds such as inorganic polyphosphates, etc.
It can also be used in combination with a chelating agent such as EDTA. Furthermore, it can also be used in combination with ordinary water treatment agents such as anti-corrosion agents and slime control agents. The scale inhibitors of the present invention can be used in the same manner as conventional scale inhibitors. For example, it can be added directly to circulating water, either continuously or intermittently. Also, the amount added depends on the application and
Although it cannot be determined unconditionally depending on the purpose, etc., in general, 1 to 100 ppm of circulating water is sufficiently effective. As specifically exemplified in the Examples below, (meth)acrylic acid and/or its salt (), sulfoethyl (meth)acrylate and/or its salt (), () component or a homopolymer of each of the () components However, although it is recognized that it is effective in inhibiting and preventing certain scales, it does not show a satisfactory effect as a scale inhibitor in an aqueous system in which many kinds of metal salts are dissolved, or it does not show any effect at all. However, although the copolymer (A) constituting the scale inhibitor of the present invention is obtained by copolymerizing monomers () and () as main components within a certain range, the scale It is surprising that the preventive effects are so excellent that it would be hard to imagine that they would be obtained from a homopolymer. By using the scale inhibitor of the present invention, scale formation can be prevented even when relatively insoluble metal salts such as calcium, magnesium, zinc, iron, etc. are contained or when the PH value is high, as described above. It also maintains excellent scale prevention effect when used in combination with water treatment agents such as corrosion inhibitors and slime control agents. The present invention will be described below with reference to Reference Examples and Examples, but the present invention is not limited to these Examples. Further, in the examples, unless otherwise specified, all parts are by weight, and all percentages are by weight. All viscosities in the reference examples were measured using a Bismethron viscometer manufactured by Precision Industrial Research Institute at 25° C. and 60 rpm. Moreover, the molecular weight was measured using high performance liquid chromatography (manufactured by Waters, Model 242). Reference example 1 323.2 ml of water was placed in a glass reaction vessel equipped with a thermometer, stirrer, dropping funnel, gas inlet pipe, and reflux condenser.
The inside of the reaction vessel was replaced with nitrogen while stirring.
Heated to 95°C. Thereafter, a monomer mixed solution consisting of 194.6 parts of a 37% sodium acrylate aqueous solution, 88 parts of sodium salt of sulfoethyl methacrylate, and 117.4 parts of water, and 64 parts of a 5% ammonium persulfate aqueous solution were each added over 120 minutes. Then, 12.8 parts of a 5% aqueous ammonium persulfate solution was added over 20 minutes. After completion of monomer addition, 120
The temperature was maintained at 95° C. for minutes to complete the polymerization reaction, and an aqueous solution of copolymer (1) was obtained. 40% of this copolymer (1)
The pH of the aqueous solution was 7.0 and the viscosity was 282 cps. Moreover, the molecular weight was 3000. Reference Example 2 339.2 parts of water was charged into the same reaction vessel as in Reference Example 1, and while stirring, the inside of the reaction vessel was purged with nitrogen and heated to the boiling point. Thereafter, a monomer mixed solution consisting of 60 parts of a 40% aqueous sodium methacrylate solution and 340 parts of a 40% aqueous sodium salt solution of sulfoethyl methacrylate and 50.7 parts of a 5% aqueous ammonium persulfate solution were added.
After addition, 10.1 parts of a 5% ammonium persulfate aqueous solution was added over 20 minutes. After the monomer addition is completed, the temperature is maintained at the boiling point for 120 minutes to complete the polymerization reaction, and the copolymer is
An aqueous solution of (2) was obtained. A 40% aqueous solution of this copolymer (2) had a pH of 7.1 and a viscosity of 477 cps. Moreover, the molecular weight was 5300. Reference Example 3 In the same reaction vessel as in Reference Example 1, 395.2 parts of an azeotropic composition of isopropyl alcohol (hereinafter abbreviated as IPA) and water (IPA/water = 87.4/12.6 (weight ratio)) was charged, and the mixture was stirred. The inside of the reaction vessel was purged with nitrogen and heated to the boiling point. After that, 72 parts of acrylic acid, 32 parts of methacrylic acid, 56 parts of sulfoethyl methacrylate,
A mixture of 4.8 parts of benzoyl peroxide and 240 parts of IPA-water azeotrope was added over 120 minutes. After the addition was complete, the temperature was maintained at the boiling point for 120 minutes to complete the polymerization reaction. Then, 40% caustic soda aqueous solution
Neutralization was performed at 161.0 parts, water was added, and IPA was distilled off to obtain an aqueous solution of copolymer (3). This copolymer (3)
The 40% aqueous solution had a pH of 7.5 and a viscosity of 420 cps.
Moreover, the molecular weight was 4800. Reference Example 4 186.7 parts of water was charged into the same reaction vessel as in Reference Example 1, and the inside of the reaction vessel was purged with nitrogen while stirring, and heated to 95°C. Then, 151.4 parts of 37% sodium acrylate aqueous solution, 88.0 parts of sodium salt of sulfoethyl methacrylate, 16.0 parts of acrylamide and water were added.
A monomer mixed solution consisting of 242.7 parts and 96.0 parts of a 5% ammonium persulfate aqueous solution were each added over 120 minutes, and after the addition was completed, an additional 19.2 parts of a 5% ammonium persulfate aqueous solution was added over 20 minutes. After the addition of the monomers was completed, the temperature was maintained at 95° C. for 120 minutes to complete the polymerization reaction, and an aqueous solution of copolymer (4) was obtained. A 40% aqueous solution of this copolymer (4) has a pH of 7.5 and a viscosity of
It was 524cps. Moreover, the molecular weight was 6000. Reference Example 5 284.8 parts of water was charged into the same reaction vessel as in Reference Example 1, and the interior of the reaction vessel was replaced with nitrogen while stirring, and heated to 95°C. Thereafter, a monomer aqueous solution consisting of 160 parts of sodium salt of sulfoethyl methacrylate and 240 parts of water and 96 parts of a 5% ammonium persulfate aqueous solution were each added over 120 minutes, and after the addition was completed, further
19.2 parts of 5% ammonium persulfate aqueous solution was added over 20 minutes. After completion of monomer addition, 95°C for 120 minutes
The polymerization reaction was completed by maintaining the temperature at , and an aqueous solution of polymer (5) was obtained. The pH of a 40% aqueous solution of this polymer (5) is
8.5, and the viscosity was 415 cps. Also, the molecular weight is
It was 4200. Example 1 In a beaker, 750 ml of deionized water, 50 ml of a 0.58% aqueous solution of calcium chloride, and an aqueous solution containing 200 ppm of the copolymer (1) obtained in Reference Example 1 as a scale inhibitor.
50 ml, and 0.44% aqueous solution of sodium bicarbonate 50
ml under stirring, then adjust the pH to 8.5 with 0.01N aqueous sodium hydroxide solution, add deionized water to make a total volume of 1000g, and store calcium carbonate at 25°C.
A 5 times supersaturated aqueous solution was prepared. This 5-times supersaturated aqueous solution was divided into four equal parts, each placed in a glass bottle, sealed tightly and allowed to stand at 60°C. After 5 hours, 10 hours, 20 hours, and 40 hours, the test liquid was taken out and cooled to 25°C, and the test solution was filtered through Toyoro paper quantitative paper No. 5C, and atomic absorption spectrometry ( 422.7 nm) to measure the concentration of calcium ions remaining in the test solution, and calculate the amount of precipitated calcium carbonate. The results are shown in Table 1. Examples 2 to 4 In Example 1, scale prevention ability was tested in the same manner as in Example 1, except that copolymers (2) to (4) obtained in Reference Examples 2 to 4 were used as scale inhibitors, respectively. . The results are shown in Table 1. Comparative Example 1 The amount of precipitated calcium carbonate was investigated in the same manner as in Example 1, except that commercially available sodium polyacrylate (molecular weight 5000) was used as a scale inhibitor. The results are shown in Table 1. Comparative Example 2 In Example 1, the amount of precipitated calcium carbonate was investigated in the same manner as in Example 1 except that the polymer (5) obtained in Reference Example 5 was used as a scale inhibitor. The results are shown in Table 1. Comparative Example 3 In Example 1, the amount of precipitated calcium carbonate was investigated in the case where no scale inhibitor was used. The results are shown in Table 1.

【table】

[Table] As is clear from the results shown in Table 1, the scale inhibitor of the present invention has an excellent scale inhibiting effect. Example 5 Put 700ml of seawater into the beaker of 1, add the copolymer (1) obtained in Reference Example 1 to 5.0ppm, and add a pipe heater (100V, 500W) as a heat source to this seawater. The mixture was immersed and evaporated while stirring. Along with evaporation and concentration, copolymer (1)
Seawater added to the solution was sequentially replenished to a concentration of 5.0 ppm. Then, the amount of scale attached to the pipe heater at the time when the concentration ratio increased to 4 times was determined. The results are shown in Table 2. Examples 6 to 8 Tests were carried out in the same manner as in Example 5, except that copolymers (2) to (4) obtained in Reference Examples 2 to 4 were used instead of copolymer (1), respectively. did. Second result
Shown in the table. Comparative Example 4 A test was carried out in the same manner as in Example 5, except that commercially available sodium polyacrylate (molecular weight 5000) was used instead of copolymer (1). Second result
Shown in the table. Comparative Example 5 A test was carried out in the same manner as in Example 5, except that the polymer (5) obtained in Reference Example 5 was used instead of the copolymer (1). The results are shown in Table 2. Comparative Example 6 In Example 5, a test was conducted in which the copolymer (1) was not used. The results are shown in Table 2.

[Table] As is clear from the results shown in Table 2, the scale inhibitor of the present invention has an excellent scale inhibiting effect.

Claims (1)

[Claims] 1 (meth)acrylic acid and/or its salt () and sulfoethyl (meth)acrylate and/or its salt () as main components, and the monomer () and the monomer () A scale inhibitor comprising a copolymer (A) having a molar ratio of 85:15 to 15:85.