JP2991579B2 - Scale inhibitor and scale prevention method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aqueous scale inhibitor. More specifically, a maleic anhydride-isobutylene copolymer hydrolyzate and maleic anhydride-
And a hydrolyzate of a copolymer of an aliphatic conjugated diene.

[0002]

2. Description of the Related Art Natural water, tap water, industrial water and the like generally contain various impurities. The impurities include cations such as calcium, magnesium, iron and barium, and anions such as carbonate ion, hydrogen carbonate ion, sulfate ion and silicate ion. Further, in some cases, a zinc ion or a phosphate ion may be contained as an anticorrosive. These waters are used as circulating water for devices such as boilers, cooling towers, evaporators, and heat exchangers. However, in these apparatuses, the ions contained in the water are heated or cooled, and sometimes the ions contained in the water become insoluble salts due to a change in pH, and are deposited and adhered to the inner wall of the apparatus, often forming scale. The formation of scale causes a decrease in heat transfer efficiency and cooling effect, an increase in flow path resistance, and causes corrosion of the device.

[0003] Thus, as a scale inhibitor, for example, lignin compounds, phosphorus compounds, acrylic acid polymer compounds, maleic acid polymer compounds and the like are used. Among them, a maleic acid-based polymer compound, for example, a hydrolyzate of a maleic anhydride homopolymer or a hydrolyzate of a maleic anhydride-monoolefin copolymer is known to have an excellent scale-inhibiting effect ( Japanese Patent Publication No. 53-2047
5, No. 54-29998).

[0004]

However, the conventionally used hydrolyzate of maleic anhydride homopolymer or hydrolyzate of maleic anhydride and unsaturated monomer has recently been used in the cooling water system. In severe conditions such as high concentration operation of, or the effect is insufficient, especially in silica-containing water system,
Satisfactory effects may not always be obtained, such as producing a gel compound insoluble with polyvalent metal ions. The present invention solves the problems of the conventional methods and provides a scale inhibitor and a scale prevention method that exhibit particularly excellent effects not only on calcium-based and magnesium-based but also on silica-based scales. It is an object.

[0005]

That is, the present invention provides a scale inhibitor comprising a hydrolyzate of a maleic anhydride-isobutylene copolymer and a hydrolyzate of a maleic anhydride-aliphatic conjugated diene copolymer. A boiler characterized by adding a hydrolyzate of these copolymers to water,
The present invention relates to a method for preventing scale in a device such as a cooling tower, an evaporator, and a heat exchanger.

The maleic anhydride-isobutylene copolymer hydrolyzate, which is the first essential component of the scale inhibitor of the present invention, has a mean molecular weight of 1,000 to 60,000, preferably about 10,000 to 30,000. It is a hydrolyzate of a polymer. The molar ratio of maleic anhydride to isobutylene in the copolymer is from 20:80 to 80:
20, preferably from 40:60 to 60:40.

The hydrolyzate of the maleic anhydride-aliphatic conjugated diene copolymer, which is the second essential component of the scale inhibitor of the present invention, has an average molecular weight of 500 to 10,000, preferably about 700 to 5,000. It is a hydrolyzate of a maleic acid-aliphatic conjugated diene copolymer. The molar ratio of maleic anhydride to aliphatic conjugated diene in the copolymer is 40: 6.
0 to 85:15, preferably 50:50 to 70:30 is suitable. The aliphatic conjugated diene constituting the copolymer is an aliphatic conjugated diene having 4 to 12, preferably 4 to 7, and more preferably 4 to 5 carbon atoms. In particular,
1,3-butadiene, 1,3-pentadiene, isoprene, 1,3-hexadiene, 2,3-dimethyl-1,3
-Butadiene, 2-ethyl-1,3-butadiene, 1,3-heptadiene and the like. In particular, 1,3-butadiene and isoprene are preferred because they have high reactivity with maleic anhydride, are easily available industrially, and are inexpensive.

The hydrolyzate of the copolymer is usually a complete hydrolyzate, but may be a partial hydrolyzate as long as it is water-soluble. The hydrolyzate of the copolymer of the present invention may be a salt of an alkali metal such as sodium or potassium, an alkaline earth metal such as calcium or barium, or a salt of ammonia or an alkylamine. Among them, sodium salts and ammonium salts are preferred.

In the present invention, the maleic anhydride-isobutylene copolymer and the maleic anhydride-aliphatic conjugated diene copolymer are mixed at a weight ratio of 1: 9 to 9: 1, preferably 3: 7. By setting the ratio to 7: 3, an excellent scale prevention effect is exhibited. In addition, these two types of polymers may be previously mixed at a predetermined ratio, or may be separately injected into the target aqueous system.

The amount of the scale inhibitor of the present invention may be appropriately added according to the target aqueous system.
The standard is about 0 mg / l, preferably about 5 to 100 mg / l.

The scale inhibitor of the present invention may be a pH adjuster such as sodium hydroxide or sodium carbonate, a phosphoric acid such as a phosphate compound, a hexametaphosphate compound or a phosphonic acid compound, or a salt thereof, or a zinc compound. , Azole compounds such as benzotriazole and tolyltriazole, chlorine compounds, quaternary ammonium compounds, organic nitrogen sulfur compounds, and germicidal compounds such as aldehyde compounds. It can be used in combination with, or mixed with, an agent.

The water system which is the object of the scale inhibitor of the present invention is an open or closed circulation type cooling water system, a transient type cooling water system, a boiler water system , and other water systems which generally cause corrosion and scale obstacles. As in the case of performing a high concentration operation in a type cooling water system, an aqueous system in which dissolved salts are highly concentrated to be corrosive and silica-based scale is likely to be generated.

[0013] The present invention provides a hydrolyzate of a copolymer of maleic anhydride and Lee isobutylene, by blending the hydrolyzate of a copolymer of maleic acid and an aliphatic conjugated diene anhydride,
These polymers are adsorbed on the scale crystal surface of calcium silicate, magnesium silicate, etc. in calcium carbonate in water, especially in high silica water systems, and effectively suppress growth and change the state of the crystal surface. And synergistically prevent scale adhesion.

[0014]

EXAMPLES Examples of the present invention will be further described below.

Example 1 Each chemical was added to a predetermined concentration in advance using synthetic water corresponding to the cooling water during the high concentration operation, and test water was added at 40 ° C. for 48 hours.
Let stand for hours. Then, the mixture was cooled to room temperature, and the supernatant was collected to measure the calcium concentration and the silica concentration. The scale deposition inhibition rate (%) was calculated by the following formula.

・ Synthetic water for calcium scale dispersion test pH 8.5 Calcium concentration 400 mg CaCO ₃ / l Magnesium concentration 200 mg CaCO ₃ / l M-alkalinity 400 mg CaCO ₃ / l ・ Synthetic water for silica scale dispersion test pH 8.5 Silica concentration 250 mg SiO ₂ / l calcium concentration 400mgCaCO ₃ / l magnesium concentration 200mgCaCO ₃ / l M- alkalinity 400mgCaCO ₃ / l · scale deposits inhibition rate (%) = ((A- B) / (C-
B)) × 100 A: Calcium concentration or silica concentration in supernatant after test B: Calcium concentration or silica concentration in supernatant after test without addition C: Calcium concentration or silica concentration before test Type of drug used Are shown in Tables (1) and (2) of Table 1, and the experimental results of the scale precipitation suppression rate are shown in Table 2.

[0017]

[Table 1]

[0018]

[Table 2]

Example 2 A heat exchanger having a heat transfer area of 0.3 m ^{2 and} a water holding amount of 0.8
The operation was performed under the following conditions so that the concentration of the circulating water became 7 times while maintaining a predetermined amount of a predetermined chemical using a laboratory open circulation type cooling device of m ³ .

Operating conditions Heat exchanger inlet temperature 30 ° C. Heat exchanger outlet temperature 45 ° C. Flow rate 1.0 m / s Makeup water quality pH 6.8 Electric conductivity 180 μS / cm silica 60 mg SiO ₂ / l Calcium 40 mg CaCO ₃ / l magnesium 10 mg CaCO ₃ / l After the operation was completed, the silica concentration and the calcium concentration of the circulating water were analyzed. Table 3 shows the experimental results.

[0021]

[Table 3]

As is clear from the results shown in Tables 2 and 3, in the case of circulating water to which the scale inhibitor of the present invention was added, the silica scale precipitation inhibiting ratio was particularly high, and the silica concentration was higher than that of the comparative example. It is significantly higher. This means that precipitation of silica scale on the heat transfer surface and the like of the used heat exchanger, adhesion is small, and the scale inhibitor of the present invention exhibits an excellent effect particularly on silica scale. You can see that. Example 3 Having a heater with a heat transfer area of 100 cm ² and holding water amount of 100
Water having the following quality, which was prepared by concentrating industrial water in advance, was placed in a liter circulation device, and a predetermined amount of a predetermined drug was added thereto, and the system was operated for 14 days.

Circulating water quality pH 8.5 Electric conductivity 1550 μS / cm Silica 180 mg SiO ₂ / l Calcium 420 mg CaCO ₃ / l Magnesium 95 mg CaCO ₃ / l After the operation was completed, the adhesion speed of the scale attached to the heater surface was measured. The results are shown in Table 4 together with Comparative Examples (in Tables 2 to 4, the same drug symbols as those in Table 1 indicate the same drugs).

[0024]

[Table 4]

Table 4 shows that the scale inhibitor of the present invention exhibits excellent effects.

[0026]

As described above, the scale inhibitor of the present invention comprises a hydrolyzate of a maleic anhydride-isobutylene copolymer and a hydrolyzate of a maleic anhydride-aliphatic conjugated diene copolymer. By doing so, it exerts an excellent preventive force not only on calcium-based and magnesium-based but also especially on silica-based scales, and not only prevents a decrease in the heat exchange rate of the heat transfer surface, but also prevents the occurrence of various obstacles, The impact on operation management in highly concentrated water systems is significant.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Akira Maho 2-33-35, Arakura, Waka-shi, Saitama (72) Inventor Toshinobu Imahama 2-2-1, Shakujii-cho, Nerima-ku, Tokyo (56) References JP-A-53-70089 (JP, A) JP-A-4-65408 (JP, A) JP-A-4-191384 (JP, A) JP-A-4-334536 (JP, A) JP-A-5-1121 (JP, A) JP-B-54-29998 (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , DB name) C02F 5/00 C02F 5/10

Claims (2)

(57) [Claims] 1. A scale inhibitor comprising a hydrolyzate of a maleic anhydride-isobutylene copolymer and a hydrolyzate of a maleic anhydride-aliphatic conjugated diene copolymer. 2. A method for preventing scale in an aqueous system, comprising adding a hydrolyzate of a maleic anhydride-isobutylene copolymer and a hydrolyzate of a maleic anhydride-aliphatic conjugated diene copolymer to water.