JPS6223640B2 - - Google Patents

Description

[Detailed description of the invention]

This invention relates to scale inhibitors. Specifically, the present invention relates to a scale inhibitor containing an organic synthetic polymer as an active ingredient. Scale generation has long been considered a problem in various industrial water systems. Most industrial water is used for heat exchange such as cooling and heating, so it becomes hot water.
Also, since it comes into contact with a heat transfer surface, scale is likely to occur.
In particular, when using water containing a large amount of hardness components, when alkali or alkaline earth metal compounds enter the water system due to factory operations or environmental reasons, the use of anticorrosives, etc. The problem of scale generation is always present when the concentration of heavy metal ions increases. Typical examples of these scales include calcium carbonate scale, phosphorous calcium scale, zinc scale, etc. Among these scales, various effective scale inhibitors have already been proposed and used for calcium carbonate scale. However, there are few effective scale inhibitors for calcium phosphate scale, zinc scale, etc., and even if there are scale inhibitors that are effective for each of the above-mentioned scales individually, there are almost no known scale inhibitors that are effective for all of the various scales. In view of these points, the inventors of this invention conducted extensive research on scale inhibitors that are uniformly effective on various scales, and as a result, they discovered that a specific organic synthetic polymer is used as the active ingredient of a scale inhibitor. The present inventors have discovered that, by doing so, the generation of calcium phosphate scale is significantly suppressed, as well as the generation of various scales such as calcium carbonate scale and zinc scale. Thus, according to the invention, the general formula (): A scale inhibitor containing a homopolymer of an alkylolamide compound represented by the formula or a copolymer of two or more thereof as an active ingredient is provided. In the above general formula (), R ₁ and R ₂ are each independently a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and X is one bond or having 1 to 8 carbon atoms, preferably 1 to 8 carbon atoms. 5, more preferably 1 to 3 alkylene groups, and these alkylene groups may have a branch. Among such homopolymers or copolymers of alkylolamide compounds,
It is known that high-molecular-weight resins are used as ion exchange resins and exhibit coagulation-sedimentation effects in water, but they are not known to exhibit scale-preventing effects at all. Specific examples of the alkylolamide compound used in this invention include N-hydroxymethacrylamide, N-hydroxymethacrylamide, N-methyl-N-hydroxyacrylamide, N-methylolacrylamide, N-methylolmethacrylamide, N-methyl- N-methylolacrylamide, N-methyl-N-methylolmethacrylamide, N-ethyl-N-methylolmethacrylamide, N-ethyl-N-methylolmethacrylamide, N-hydroxyethylacrylamide, N-
Hydroxyethyl methacrylamide, N-methyl-N-hydroxyethylacrylamide, N-ethyl-N-hydroxyethylacrylamide, N
-Propyl-N-hydroxyethylacrylamide, N-hydroxypropylacrylamide, N
-Hydroxypropyl methacrylamide, N-hydroxyisopropylacrylamide, N-hydroxyisopropyl methacrylamide, and the like. Among these, N-methylol acrylamide, N-methylol methacrylamide, N-hydroxyethylacrylamide, N-hydroxyethyl methacrylamide, etc. can be preferably used from the viewpoint of ease of synthesis, cost, etc. The specific organic synthetic polymer in this invention is a homopolymer of the above-mentioned alkylolamide compound or a copolymer of two or more thereof, each obtained by subjecting it to known polymerization conditions, and various Those with molecular weights can be used, but those with too high molecular weights are not preferred because they cause aggregation.
It is usually about 500 to 100,000, preferably about 500 to 20,000. A particularly preferred molecular weight is about
2000-5000. These polymers or copolymers can be prepared by, for example, adding one or more of the alkylolamide compounds to a polymerization initiator (e.g., in water or an organic solvent (e.g., alcohol, dioxane, aromatic solvent, etc.)).
It can be obtained by heating with inorganic and organic peroxides such as persulfates and benzoyl peroxide, azobisisobutyronitrile, redox catalysts, etc.). In addition, if the polymerization reaction is carried out or under acidic conditions, crosslinking is likely to occur, resulting in a three-dimensional structure, which may reduce the solubility and dispersibility of the resulting polymer. Therefore, it is desirable to carry out the polymerization reaction under alkaline conditions by adding sodium hydroxide or the like. However, any conditions can be used as long as the obtained polymer or copolymer exhibits desired solubility and dispersibility. The polymer or copolymer of this invention is usually used in the form of a powder or liquid preparation. As the liquid preparation, it is convenient and preferable to use an aqueous liquid containing the polymer obtained by the above-mentioned polymerization reaction as it is. In this case, since the polymerization reaction further proceeds in the liquid preparation, it is desirable to add a polymerization inhibitor such as hydroquinone. When using the polymer or copolymer of the present invention as a scale inhibitor, it can be added in exactly the same manner as for ordinary scale inhibitors, and the amount added varies depending on the target aqueous system. Usually, the purpose can be achieved by adding 0.5 to 300 ppm of the active ingredient. In addition, the scale inhibitor of the present invention can be used in combination with conventional scale inhibitors such as sulfonic acid, phosphonocarboxylic acid, EDTA, NTA, lignin sulfonic acid,
It is also possible to use it in combination with polyacrylic acid, polymaleic acid, etc. Furthermore, the scale inhibitor of the present invention may be used in combination with a commonly used corrosion inhibitor; in this case, it will not have any adverse effects on the corrosion inhibitor, and will also simultaneously exhibit the effect of preventing scale caused by the corrosion inhibitor itself. Therefore, even more favorable results can be obtained. In this case, the anticorrosive agents used in combination include polymerized phosphates, salts of heavy metals such as zinc, manganese, and nickel.
Examples include molybdate, oxycarboxylate, and the like. The scale inhibitor of the present invention is effective in preventing the generation of not only calcium phosphate scale but also calcium carbonate scale, and is also effective in preventing the generation of various other scales. Therefore, it is effective in preventing not only single scale but also multi-component scale in various industrial water systems, making it an industrially useful agent. Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited thereby. Example 1 Polymers of alkylolamide compounds shown in Table 1 were synthesized by known methods, and a calcium carbonate scale prevention test was conducted using these polymers. Note that the molecular weight of each polymer is an approximate value determined by the viscosity method.

[Table] (Test method) 100 ppm of calcium ions and sodium bicarbonate were added to pure water to give an M alkalinity of 600 ppm to prepare a test solution. Add each of the above compounds to test solution 1 to a predetermined concentration,
Stirring was continued for 2 hours at 200 rpm using a magnetic stirrer while maintaining the temperature at 50°C. Next, separate the test liquid with paper (Toyoguchi No. 6),
The calcium ion concentration of the liquid was measured. The amount of calcium ions precipitated during the test was determined from the difference in calcium ion concentration in the test solution before and after the test, and from this the amount of calcium carbonate (CaCO ₃ ) scale deposited per test solution was calculated. The results are shown in Table 2.

[Table] Example 2 A calcium phosphate scale prevention test was conducted using 3 times concentrated Osaka city water. Table 3 shows the quality of the water used. Table 3 PH 7.50 Electrical conductivity (μs/cm) 750 P alkalinity (ppm) 0 M alkalinity (ppm) 61.5 Calcium hardness (ppm) 98.6 Total hardness (ppm) 157.0 Sulfate ion (ppm) 39.5 Chlorine ion (ppm) 69.1 Silica (SiO ₂ ) (ppm) 10.5 Total iron (ppm) 0.5 20 ppm of sodium hexametaphosphate as PO ₄ ^3- and 20 ppm of monobasic sodium phosphate as PO ₄ ^3- were added to the above concentrated water 1 to prepare Example 1. Add each of the compounds used in step 1 to the specified concentration, and use a stirrer while maintaining the temperature at 50℃.
Stirring was continued for 24 hours at 10 rpm. Thereafter, the amounts of precipitated calcium ions and total phosphoric acid were determined in the same manner as in Examples, and the sum was defined and calculated as a calcium phosphate scale. The results are shown in Table 4.

【table】

[Table] Example 3 The scale inhibiting effect of the combined use of the scale inhibitor of the present invention and various anticorrosive agents was tested. The 3-fold concentrated water 1 of Example 2 was used as the water used, and each compound was added thereto to a predetermined concentration. Mild steel plate (SPCC;
30 x 50 x 1 mm), the mild steel plate is immersed in the solution, and the mild steel plate is kept at a constant temperature of 50°C.
Stirring was continued for 5 days at 100 rpm. Magnesium, calcium, zinc, and total phosphate ions before and after the test were measured in the same manner as in Example 1, and the total was taken as the amount of precipitated ions per test solution. The results are shown in Table 5.

【table】

Claims (1)

[Claims] 1 General formula (): (In the formula, R ₁ and R ₂ are each independently a hydrogen atom or an alkyl group having 1 to 3 carbon atoms; X is an alkylene group which may have one bond or a branch having 1 to 8 carbon atoms) A scale inhibitor containing a homopolymer of an alkylolamide compound represented by the following or a copolymer of two or more thereof as an active ingredient. 2 The alkylolamide compound is N-hydroxyacrylamide, N-hydroxymethacrylamide, N-methyl-N-hydroxyacrylamide, N-methylolacrylamide, N-methylolmethacrylamide, N-methyl-N-methylolacrylamide, N-methyl -N-methylolmethacrylamide, N-ethyl-N-methylolmethacrylamide, N-ethyl-N-methylolmethacrylamide, N-hydroxyethylacrylamide, N-hydroxyethylmethacrylamide, N-methyl-N-hydroxyethylacrylamide, N -ethyl-N-hydroxyethylacrylamide, N-propyl-N-hydroxyethylacrylamide, N-hydroxypropylacrylamide, N-hydroxypropylmethacrylamide, N-hydroxyisopropylacrylamide, or N-hydroxyisopropylmethacrylamide. The scale inhibitor according to scope 1. 3. The scale inhibitor according to any one of claims 1 to 2, wherein the alkylolamide compound is N-methylol acrylamide, N-methylol methacrylamide, N-hydroxyethyl acrylamide, or N-hydroxyethyl methacrylamide. . 4 The molecular weight of the homopolymer or copolymer is approximately 500 ~
100,000, the scale inhibitor according to any one of claims 1 to 3. 5 The molecular weight of the homopolymer or copolymer is approximately 500~
20,000, the scale inhibitor according to any one of claims 1 to 3.