JP2001081184A - Polyepoxysuccinic acid derivative or its water-soluble salt and scale inhibitor in water system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a new compound having biodegradability, useful as a scale inhibitor in a circulating water system such as an open circulating system. SOLUTION: This polyepoxysuccinic acid derivative is represented by the structural formula (n is a repeating structure) or its water-soluble salt and has 500-3,000 weight-average molecular weight. This scale inhibitor in a water system comprises the polyepoxysuccinic acid derivative or its water-soluble salt as active ingredient.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a novel biodegradable polyepoxysuccinic acid derivative or a water-soluble salt thereof (hereinafter collectively referred to as "polyepoxysuccinic acids"), and a scale using the same. It relates to an inhibitor.

[0002]

BACKGROUND OF THE INVENTION Chemicals that accumulate in the environment are now of great interest and great efforts are being made to reduce them. The solution is to use chemicals that ideally do not emit chemicals into the environment, but that if not met will easily decompose in the environment. In an industrial water system such as a circulating cooling water system, while the circulation and reuse of water is strengthened to minimize the amount of water discharged to the outside as much as possible, the use of biodegradable treating agents is being promoted.

At a variety of factories such as an oil refinery, a chemical factory, and a steel mill, a boiler and a circulating cooling water system of a nuclear power plant, a thermal power plant, an air conditioner, and the like, the adhesion of scale causes a decrease in heat transfer efficiency, blockage of pipes, corrosion. Various obstacles may occur during driving.

[0004] The scale is based on the fact that impurities derived from calcium, magnesium, iron, phosphorus, silica or the like in water are concentrated under high temperature conditions, and calcium carbonate, hydroxyapatite, iron oxide, magnesium silicate and the like are precipitated. On the heat transfer surface at a high temperature, the tendency of precipitation is particularly large, which is also a problem.

[0005] Recently, the unit heat transfer surface evaporation rate has become extremely higher than that of the conventional type, especially due to the packaging and high performance of medium and low pressure boilers and refrigerators. Due to the increase in the concentration of impurities in the water, the scale is more easily generated than before, and even if a small amount of scale adheres, the amount of power increases and the refrigeration efficiency decreases. Scale disturbances are becoming an increasingly important issue.

[0006] To solve such problems, scale inhibitors such as phosphoric acid compounds and synthetic carboxylic acid compounds such as polyacrylic acid and polymaleic acid have been used. However, when these compounds are discharged outside the system as blowdown water in the operation of the circulating cooling water system,
Phosphate compounds flow into lakes and inner bays, causing problems such as red tides due to eutrophication.Synthetic carboxylic compounds are slow to decompose naturally in the environment, and there is concern that they will accumulate in the environment. Was.

[0007] Therefore, as a scale inhibitor which does not cause a problem in the surrounding environment, polytartaric acid containing no phosphorus and having excellent biodegradability (Japanese Patent Application Laid-Open No. 6-240577) and polyepoxysuccinic acid (Japanese Patent Application Laid-Open No. 166298, U.S. Pat. No. 5,256,332 (1993)), but the effect of preventing scale is not sufficiently large, and a more effective one is desired.

[0008]

An object of the present invention is to provide a compound which is biodegradable and is useful as a scale inhibitor in a circulating water system such as an open circulation system.

[0009]

Means for Solving the Problems The present inventors have found that a polyepoxysuccinic acid derivative having a specific molecular weight in which citric acid is bound to one end has good biodegradability and remarkably suppresses scale formation in an aqueous system. This has led to the achievement of the present invention.

That is, the invention according to claim 1 of the present invention relates to a polyepoxy succinic compound represented by the following structural formula (where n represents a repeating structure) and having a weight average molecular weight of 500 to 3,000. An acid derivative or a water-soluble salt thereof.

[0011]

Embedded image

The invention according to a second aspect of the present invention is an aqueous scale inhibitor comprising the polyepoxysuccinic acid derivative or the water-soluble salt thereof according to the first aspect as an active ingredient.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. The polyepoxysuccinic acids of the present invention can be obtained by polymerizing epoxysuccinic acid in the presence of citric acid.

Epoxy succinic acid is described, for example, in The Journal of Organic Chemistry, No. 2,
4, p. 54 (1959). In this method, maleic anhydride or maleic acid is reacted with hydrogen peroxide using tungstate or the like as a catalyst to produce cis-epoxysuccinic acid, or fumaric acid is reacted with hydrogen peroxide to produce trans-epoxysuccinic acid. Is what you do. In the present invention, cis-epoxysuccinic acid or trans-epoxysuccinic acid may be used, or a mixture of both may be used.

[0015] Polyepoxysuccinic acids polymerize epoxysuccinic acid in the presence of citric acid. The polymerization reaction is carried out in an alkaline aqueous solution in the presence of an alkali metal or alkaline earth metal hydroxide, oxide or various salts, It is preferably carried out using a calcium ion donating compound as a catalyst.

[0016] The catalyst used in the polymerization reaction is a catalyst which allows the reaction between citric acid and epoxysuccinic acid to be carried out smoothly, and includes hydroxides, oxides and various salts of alkali metals or alkaline earth metals, preferably calcium. Calcium compounds that donate calcium ions in an aqueous alkaline solution, such as hydroxides, oxides or various salts, are used. The amount of the catalyst used is usually from 0.01 to 1 mol, preferably from 0.1 to 1 mol, per mol of epoxy succinic acid.
It is 0.5 to 0.7 mol.

The pH at the time of carrying out the reaction is preferably 9 or more, more preferably 1 to increase the reaction yield.
It is in the range of 0-14. The reaction temperature is usually 50 to 15
0 ° C. is preferred.

The weight average molecular weight of the polyepoxysuccinic acids is 500 to 3000, preferably 700 to 2500,
More preferably, it is 900-1500. If the weight average molecular weight is less than 500 or greater than 3000, no remarkable effect on scale suppression is observed.

The molar ratio between citric acid and epoxy succinic acid in the polymerization reaction is preferably from 1: 2 to 1:30. Since the moles of citric acid and epoxy succinic acid have a close relationship with the molecular weight of the polymer to be obtained, they should be determined in consideration of the target molecular weight.

The weight average molecular weight of polyepoxysuccinic acids is determined by gel permeation chromatography (GP
According to C), it can be measured using sodium polyacrylate as a standard substance.

Among the polyepoxysuccinic acids, the water-soluble salts include alkali metal salts such as sodium and potassium, alkaline earth metal salts such as calcium and magnesium, ammonium salts and organic amine salts. Preferred for the present invention are sodium and calcium salts, more preferred are the sodium salts.

The polyepoxysuccinic acids of the present invention can be used in aqueous systems as scale inhibitors, detergents, detergent builders, ion sequestering agents, dispersants, chelating agents, boiler cans and the like.

The method of applying the scale inhibitor is not particularly limited in the present invention, but the polyepoxysuccinic acids obtained by the above method are dissolved in water or a suitable organic solvent to meet the intended use. It is convenient to prepare the solution of the concentration before use.

When the scale inhibitor is added to the aqueous system, the amount added is 0.1 to 5000 as polyepoxysuccinic acid.
mg / L. However, it goes without saying that the range of the appropriate addition amount varies depending on the operating conditions and water quality of the applied water system.

The polyepoxysuccinic acids used as scale inhibitors may be copolymerized with other epoxy compounds other than epoxysuccinic acid or other vinyl compounds as long as the function of preventing scale is not impaired. It does not preclude the use of a combination of scale inhibitors of the type However, in consideration of biodegradability, it is needless to say that there is a limit to copolymerization with other vinyl compounds or to use in combination with other types of scale inhibitors. It is desirable to use it within a range that does not impair.

In addition, a corrosion inhibitor and a microorganism control agent may be used at the same time, but the present invention does not limit the use thereof.

[0027]

The present invention will be described below in more detail with reference to examples and comparative examples. Synthesis 1L flask was charged with epoxy succinic acid disodium epoxysuccinate Deionized water 300 ml, was added thereto and dissolved by stirring the maleic acid 89. 2g (0. 91mol). While cooling, 114 g of 48% NaOH (1.3 g)
7 mol) was gradually dropped, and a heat was generated.
The temperature rose to 5 ° C. After cooling to a temperature of 65 ° C., 120 g (1.06 mol) of 30% hydrogen peroxide and 6.0 g of sodium tungstate were added and dissolved by stirring. Approximately 8 minutes after the addition of hydrogen peroxide, rapid heat generation was observed, so cooling was started immediately, but the temperature rose to 86 ° C. Temperature 60 ~
After cooling to 65 ° C, 31.8 g of 48% NaOH (0.3
(8 mol), pH was adjusted to 5.3 (pH before adding NaOH was 3.4), and the temperature was maintained at 70 ° C for 1 hour.
The total addition amount of 48% NaOH is 150.8 g (1.82
mol) to the remaining 48% NaOH (5.9).
g) was added and maintained at a temperature of 70 ° C. for 10 minutes. During that time, foaming due to decomposition of unreacted hydrogen peroxide was observed. Upon cooling to room temperature, 562.8 g of an aqueous solution of disodium epoxysuccinate was obtained (solid content 30.8%, pH 1).
3.1).

Example 1 In a 500 ml flask equipped with a reflux tube, 40.5 g (0.09 mol) of an aqueous solution of dipotassium epoxysuccinate, 50%
3.84 g of citric acid (manufactured by Fuso Chemical) (0.01 mo)
l), 10 g of deionized water was added, and the pH was adjusted to 11.0 by adding 2.99 g of 48% sodium hydroxide. Here, 0.74 g (0.01 mol) of calcium hydroxide
Is added and stirred at a temperature of 80 ° C. under a stream of nitrogen gas.
Heated for hours. After cooling and filtering the reaction product, it was passed through a cation exchange resin to remove metal cations. afterwards,
The desired polymer component was obtained by performing a separation operation with methanol. The polymer was again neutralized with sodium hydroxide. The number average molecular weight (Mn) of the reaction product was 1187, and the weight average molecular weight (Mw) was 1361. The polymer aqueous solution was desalted by ion exchange, and reprecipitated and washed in methanol to remove impurities. Further, the polymer was neutralized, and the polymer obtained by performing the same operation was dried under reduced pressure. FIG. 1 shows the result of ¹ HNMR measurement, and FIG. 2 shows the result of IR measurement.

Example 2 1.92 g (0.005 mol) of 50% citric acid, 4
A polymer was obtained in the same manner as in Example 1 except that 2.61 g of 8% sodium hydroxide was added and adjusted. Mn of the reaction product was 2018 and Mw was 2119.

Example 3 7.68 g (0.02 mol) of 50% citric acid, 48
A polymer was obtained in the same manner as in Example 1, except that 3.24 g of 3% sodium hydroxide was added. Mn of the reaction product was 742 and Mw was 864.

Comparative Example 1 A 500 g flask equipped with a reflux tube was charged with 100 g (0.178 mol) of an aqueous solution of disodium epoxysuccinate.
1.39 g (0.0188 mol) of calcium hydroxide was added, and the mixture was heated with stirring at a temperature of 80 ° C. for 4 hours under a stream of nitrogen gas. After cooling and filtering the reaction product, it was passed through a cation exchange resin to remove metal cations. Thereafter, a separation operation was performed with methanol to obtain a polymer. The polymer was again neutralized with sodium hydroxide. Mn of the polymer was 900 and Mw was 1063.

Measurement of biodegradability A commercially available standard activated sludge was cultured at a temperature of 25 ° C. for 14 days in accordance with JIS K6950-1994. At this time, the biodegradation rate was determined from a comparison between the oxygen demand in the culture solution and the theoretical oxygen demand. Table 1 shows the measurement results of 1) the sodium salt of polyepoxysuccinate described in Example 1 2) the sodium salt of polyepoxysuccinate described in Comparative Example 1 and 3) the sodium salt of polyacrylic acid having a molecular weight of 6,000. [Margins below]

[0033]

[Table 1]

From the results, it is understood that the polyepoxysuccinic acids of the present invention have high biodegradability.

Scale suppression test In 170 ml of water, 1.56% aqueous calcium chloride solution 10
ml and 0.02 of the polymer of Example or Comparative Example.
% Aqueous solution 2 ml (2 p
pm), and 10 ml of a 3% aqueous sodium hydrogen carbonate solution was added to make a total volume of 200 ml. The supersaturated aqueous solution (pH 8.5) of 530 ppm of calcium carbonate thus obtained was sealed in a glass bottle, and the temperature was 70 ° C.
At 3 o'clock. After cooling, the precipitate was separated by filtration with a 0.1 μm membrane filter, and the calcium concentration of the filtrate was determined according to JIS K0101. The scale inhibition rate (%) of calcium carbonate was determined by the following equation. As a comparative example, a case where a sodium polyacrylate having a molecular weight of 6000 was used is also shown. Table 2 summarizes the results.

[0036]

[Formula 1] Scale suppression rate (%) = (CB) / (A−
B) × 100 A: The concentration of calcium dissolved in the liquid before the test (%) B: The calcium concentration in the filtrate without the scale inhibitor C: The calcium concentration in the filtrate with the scale inhibitor (%) )

[0037]

[Table 2]

From these results, it is understood that the polyepoxysuccinic acids of the present invention have a large calcium carbonate scale preventing effect.

[0039]

The novel polyepoxysuccinic acids of the present invention are susceptible to degradation by the action of microorganisms existing in nature and have no problem of environmental pollution due to accumulation in living organisms.

This compound has an excellent scale-suppressing ability against scales generated in water systems, and does not bind phosphorus, so that it does not cause red tide due to eutrophication even when it flows into lakes or marshes. Therefore, destroy the surrounding environment in various factories such as petroleum refining factories, chemical factories, steelworks, etc., and in water systems used for cooling and heating of various processes and various equipment such as nuclear power plants, thermal power plants, and air conditioners. It can be an environmentally harmful scale inhibitor that suppresses scale formation.

[Brief description of the drawings]

FIG. 1 is a ¹ HNMR measurement chart of sodium polyepoxysuccinate obtained in Example 1 of the present invention.

FIG. 2 is an IR measurement chart of the polyepoxysuccinate Na salt obtained in Example 1 of the present invention.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Naoko Fujigo, 6-6-9, Yokkaichi, Mie Pref. Inside Yokkaichi R & D Co., Ltd. (72) Inventor Junichi Nakajima 6-6-9, Hakuto Co., Ltd., Yokkaichi, Mie Pref. Inside Yokkaichi Research Institute (72) Inventor Masahiro Aoyama 1 in Funami-cho, Minato-ku, Nagoya-shi, Aichi Prefecture Toagosei Co., Ltd.Nagoya Research Institute (72) Inventor Kozo Kubota 1 in Funami-cho, Minato-ku, Nagoya-shi, Aichi 1 Nagoya Research Institute, Toagosei Co., Ltd. (72) Inventor Minoru Atsuchi 1-term, Funamicho, Minato-ku, Nagoya-shi, Aichi F-term in Nagoya Research Institute, Toagosei Co., Ltd. 4J005 AA12 4K062 AA03 BB06 BC12 BC13 BC22 GA08 GA10

Claims (2)

[Claims] 1. A compound represented by the following structural formula (wherein, n represents a repeating structure) having a weight average molecular weight of 500.
A polyepoxysuccinic acid derivative or a water-soluble salt thereof. Embedded image 2. An aqueous scale inhibitor comprising the polyepoxysuccinic acid derivative or the water-soluble salt thereof according to claim 1 as an active ingredient.