JPH05155920A - Scale preventive - Google Patents

Abstract

PURPOSE:To provide a scale preventive which can prevent the formation of scales chiefly consisting of calcium even in a low-concentration region in which a maleic acid polymer cannot effectively prevent the formation of scales. CONSTITUTION:The objective scale preventive comprises a hydrolyzate of a maleic anhydride/aliphatic conjugated diene copolymer having a weight-average molecular weight of 500-10000 and a content of maleic anhydride units of 40-85mol%.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a scale inhibitor. More specifically, it relates to a scale inhibitor containing a hydrolyzate of a copolymer of maleic anhydride and an aliphatic conjugated diene.

[0002]

2. Description of the Related Art Generally, natural water, tap water, industrial water and the like contain various impurities. Impurities include cations such as calcium, magnesium, iron, and barium, and anions such as carbonate ions, hydrogen carbonate ions, sulfate ions, and silicate ions. Furthermore, in some cases, zinc ions and phosphate ions may be contained as anticorrosive agents. These waters are used as circulating water for devices such as boilers, cooling towers, evaporators and heat exchangers. However, in these devices, the water is heated or cooled, and sometimes the pH changes, so that the above ions contained in the water become insoluble salts, which are deposited on the inner wall of the device and adhere to the scale, often causing scale. Form. The formation of the scale causes a decrease in heat transfer efficiency and a cooling effect, an increase in flow path resistance, and a cause of corrosion of the apparatus.

Therefore, as scale inhibitors, for example, lignin compounds, phosphorus compounds, acrylic acid polymer compounds, maleic acid polymer compounds and the like are used.
Among them, maleic acid polymer compounds, for example, maleic anhydride homopolymer hydrolyzate and maleic anhydride-hydrolyzate of monoolefin copolymer are known to have an excellent scale-preventing effect. (Japanese Patent Publication Sho 53-20
No. 475, No. 54-29998, JP-A-53-700.
89, 60-71093).

[0004]

However, the above maleic acid type polymer compounds have not always been satisfactory under severe conditions such as the recent highly concentrated operation of cooling water systems. In particular, there is room for improvement in terms of the effect of preventing scale, which is mainly composed of calcium. That is, if the concentration of the maleic acid-based polymer compound was set to a relatively low concentration, it was not possible to effectively prevent the scale containing calcium as the main component.

Among the above maleic acid type polymer compounds, the hydrolyzate of a maleic anhydride homopolymer is particularly excellent as a scale inhibitor. However, at the time of production, a relatively expensive polymerization initiator needs to be used in a large amount, for example, 20% by weight with respect to maleic anhydride, so that the hydrolyzate of the maleic anhydride homopolymer produced is also expensive. There was a problem in safety and manufacturing safety.

Therefore, an object of the present invention is to provide a scale preventive agent capable of preventing the formation of a scale containing calcium as a main component even in a low concentration region where the above maleic acid polymer cannot effectively prevent scale. ..

Another object of the present invention is to provide a scale inhibitor which can be produced by using a relatively small amount of a polymerization initiator, and as a result is inexpensive.

[0008]

The present invention is a copolymer of maleic anhydride and an aliphatic conjugated diene having a weight average molecular weight of 500 to 10,000 and a maleic anhydride unit content of 40 to 85 mol. % Of the copolymer hydrolyzate.

The aliphatic conjugated diene constituting the copolymer of the present invention has a carbon number of 4 to 12, preferably 4 to 7,
More preferably, it is a 4-5 aliphatic conjugated diene. Specifically, 1,3-butadiene, 1,3-pentadiene,
Examples include isoprene, 1,3-hexadiene, 2,3-dimethyl-1,3-butadiene, 2-ethyl-1,3-butadiene, and 1,3-heptadiene. In particular,
1,3-Butadiene and isoprene are preferable because they have high reactivity with maleic anhydride, are easily industrially available, and are inexpensive. The copolymer of the present invention may contain one kind of these conjugated diene units or two kinds or more.

The hydrolyzate of the copolymer of the present invention exerts a scale preventing effect when the content of the maleic anhydride unit is 40 to 85 mol%. Further, the content of the maleic anhydride unit is 45 to 75 mol%, from the viewpoint of excellent scale prevention effect and easy production.
More preferably, it is 50 to 70 mol%. The content of maleic anhydride unit in the copolymer is
It can be determined using the CHN elemental analysis method or the NMR spectrum method.

Further, the weight average molecular weight of the copolymer is 50.
It is suitable that it is from 0 to 10,000, preferably from 700 to 5,000, from the viewpoint of exerting an excellent scale preventing effect. Here, the weight average molecular weight can be determined by measurement by gel permeation chromatography (GPC).

The scale preventive agent of the present invention comprises a hydrolyzate of the above-mentioned copolymer of maleic anhydride and an aliphatic conjugated diene. 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 is
Alkali metals such as sodium and potassium, calcium,
It may be an alkaline earth metal such as barium, or a salt such as ammonia or an alkylamine. Of these, sodium salts and ammonium salts are preferable.

The method for producing the hydrolyzate of the copolymer used in the scale inhibitor of the present invention will be described below.

The hydrolyzate of the copolymer of the present invention is obtained by, for example, radical copolymerizing a maleic anhydride and an aliphatic conjugated diene in a solvent in the presence of a radical generator to obtain the resulting copolymer. It can be produced by a method of hydrolysis.

In the polymerization, the aliphatic conjugated diene is preferably added continuously to the mixture of maleic anhydride and solvent. This is because if the aliphatic conjugated diene is preliminarily charged with maleic anhydride and the reaction solvent, the Diels-Alder reaction may proceed during the temperature rise or in the initial stage of the polymerization reaction to lower the yield. The polymerization reaction can be prioritized over the Diels-Alder reaction by continuously supplying the aliphatic conjugated diene. The radical generator may be added in advance to the mixture of maleic anhydride and the reaction solvent, or may be continuously added like the aliphatic conjugated diene.

As the solvent, hydrocarbons such as benzene, toluene, xylene and cyclohexane, ketones such as acetone, cyclohexanone and methyl ethyl ketone, esters such as ethyl acetate and isopropyl acetate, ethers such as dibutyl ether, tetrahydrofuran and dioxane, Alternatively, dimethyl sulfoxide, dimethylformamide, gamma butyrolactone and the like can be used. These solvents can be classified into those in which maleic anhydride is dissolved but the copolymer is not dissolved, and those in which both maleic anhydride and the copolymer are dissolved. When the former type of solvent is used, the polymerization proceeds as precipitation polymerization or suspension polymerization in the presence of a suitable dispersant. On the other hand, when the latter type of solvent is used, the solution polymerization proceeds. Solvents such as amines and alcohols are not suitable for reacting with maleic anhydride or the resulting copolymer.

Among the above-mentioned solvents, aromatic hydrocarbon solvents are preferable from the viewpoints of production and process. The aromatic hydrocarbon solvent is a poor solvent for the present copolymer, and after completion of the reaction, the copolymer is precipitated and obtained as a precipitate. Therefore, after completion of the polymerization reaction, most of the solvent can be easily separated by removing the supernatant solution, and further, unreacted maleic acid and by-products can be simultaneously removed. Further, when producing a hydrolyzate of a copolymer, there is an advantage that a small amount of the solvent remaining in the system can be easily removed as an azeotropic mixture with water.

As the aromatic hydrocarbon solvent, benzene,
Examples thereof include alkyl-substituted benzenes such as toluene, xylene, ethylbenzene and cumene, and halogen-substituted benzenes such as chlorobenzene and bromobenzene. Preferred are benzene, toluene and xylene.

The amount of solvent used is not particularly limited. However,
From the viewpoint of controlling local and rapid reaction, for example, 50 to 500 parts by weight with respect to 100 parts by weight of maleic anhydride.
It is expedient to use parts by weight of solvent.

A mixture of maleic anhydride and a solvent, which has been charged in advance in a polymerization vessel, or a mixture of this mixture and a radical generator is heated to a predetermined reaction temperature, and then an aliphatic conjugated diene is added to the mixture. Further, if desired, it is preferable to continuously supply the solution of the radical generator to carry out the polymerization. This is because if the aliphatic conjugated diene, maleic anhydride and a solvent are charged in advance, the Diels-Alder reaction may proceed during the temperature rise or at the beginning of the polymerization, and the yield may decrease. The polymerization reaction can be prioritized over the Diels-Alder reaction by continuously supplying the aliphatic conjugated diene.

In the present method, the feeding rates of the aliphatic conjugated diene and the radical generator are not particularly limited. However,
When an aromatic hydrocarbon is used as the solvent, it is preferable that the feed rate of the aliphatic conjugated diene satisfies the following conditions from the viewpoint of suppressing the Diels-Alder reaction and suppressing the formation of an insoluble three-dimensional polymer. ..

Y> 280X + 80 and X ≧ 0.07 where Y represents the reaction temperature (° C.), and X represents the feeding rate of the aliphatic conjugated diene (total moles of conjugated diene / total moles of maleic anhydride / The conjugated diene supply time (hour) is shown.

The aliphatic conjugated diene can be evenly fed during the polymerization reaction, or the feeding rate can be increased or decreased for controlling the reaction.

On the other hand, when the radical generator is continuously supplied, the supply rate of the radical generator is not particularly limited. However, it is preferable that the radicals are generated in time with the supply of the conjugated aliphatic diene, and it is preferable that all the radical generators be supplied in a time substantially the same as the time of supplying the conjugated diene. Further, the radical generator can be uniformly supplied during the polymerization reaction, and the supply rate can be increased or decreased for controlling the reaction.

The radical generator used in this method is determined in consideration of its half-life. It is preferable to use a radical generator having a half-life of 1 hour or less in the reaction temperature range. If the half-life is too long, the amount of radicals generated per unit time will be small, and the Diels-Alder reaction will proceed rather than the polymerization reaction, leading to a decrease in yield. Absent.

At a temperature of 90 ° C. or higher, which is a reaction temperature range,
Examples of the radical generator having a half-life of 1 hour or less include t-butylperoxy (2-ethylhexanoate),
Peroxyesters such as t-butylperoxybenzoate, dialkyl peroxides such as di-t-butylperoxide and dicumyl peroxide, 1,1-
Mention may be made of peroxyketals such as bis (t-butylperoxy) -3,3,5-trimethylcyclohexane.

The amount of the radical generator used is, for example, 0.05 to 15% by weight, preferably 0.5 to 10% by weight, based on maleic anhydride. If the amount used is too small, the polymerization reaction will not proceed effectively, and if it is too large, the molecular weight will decrease too much, and it is not preferable from the economical viewpoint.

The amounts of maleic anhydride and aliphatic conjugated diene used can be appropriately adjusted by the maleic anhydride unit and aliphatic conjugated diene unit of the copolymer.

The aliphatic conjugated diene and the radical generator are
It can be supplied as it is or as a mixture with a solvent.
However, it is preferable to supply a mixture with a solvent from the viewpoint of suppressing local rapid reaction. The mixing ratio (weight ratio) with the solvent is 50 to 5000 parts by weight of the solvent and 100 parts by weight of the aliphatic conjugated diene, and the radical generator 1
It is suitable that the amount of the solvent is 500 to 5000 parts by weight based on 00 parts by weight.

The reaction temperature is preferably 90 ° C. or higher. When the temperature is lower than this temperature, the average molecular weight of the copolymer becomes excessively higher than the desired value, or three-dimensional crosslinking is likely to occur, and the copolymer cannot be used as a water-soluble copolymer. On the other hand, the upper limit of the reaction temperature is not particularly limited, but it is preferably less than 180 ° C. in order to make the average molecular weight of the obtained copolymer a desired value. Considering the average molecular weight of the copolymer and the reaction time, the reaction temperature is more preferably in the range of 100 to 160 ° C.

Since the polymerization reaction is almost completed after the addition of the aliphatic conjugated diene and the radical generator, the polymerization reaction may be completed when the addition is completed. However, in order to completely consume the unreacted monomer and the radical generator, it is preferable to continue the polymerization reaction for a certain period of time, for example, for about 30 minutes to 2 hours.

After completion of the reaction, the copolymer precipitated in the precipitation or suspension polymerization is recovered by filtration separation or decantation of the supernatant. If necessary, it can be further washed with a poor solvent. On the other hand, in solution polymerization, the reaction solution is added to a large amount of a poor solvent to precipitate a copolymer, and the copolymer is recovered by filtration separation or decantation of the supernatant.

The copolymer recovered in this way is heated under reflux with water for a certain period of time, or steam is introduced and steam distillation is carried out to distill off the residual solvent and hydrolyze to obtain an aqueous solution. You can However, from an economical and industrial point of view, it is desirable to hydrolyze using steam to obtain an aqueous solution. Further, the concentration is preferably 10 to 60% by weight as a solid content.

Further, the hydrolyzate of this copolymer can be made into a salt if necessary. The compound used to form a salt is not particularly limited, but examples thereof include alkali metal compounds, alkaline earth metal compounds, and basic substances such as ammonia and alkylamines. Use sodium hydroxide, potassium hydroxide, magnesium hydroxide as the alkali metal compound and alkaline earth metal compound, and use methylamine, ethylamine, aniline, cyclohexylamine, monoethanolamine, ethylenediamine, etc. as the alkylamine. You can It is also possible to make the above-mentioned basic substance coexist at the time of hydrolysis to perform a hydrolyzate and obtain a water-soluble salt of the copolymer.

The scale inhibitor of the present invention contains the above water-soluble maleic acid copolymer. The amount added when the water-soluble maleic acid copolymer is used as a scale inhibitor varies depending on the concentration of each ion in water, but is, for example, 0.1 to
By setting it to 100 ppm, preferably 0.2 to 20 ppm, it is possible to effectively prevent the generation of scale.

In addition to the above water-soluble maleic acid copolymer or its salt, the scale inhibitor of the present invention may be used in combination with known agents such as water treatment agents.

[0038]

EXAMPLES The present invention will be further described below with reference to examples, but the present invention is not limited thereto.

Example 1 100 parts by weight of maleic anhydride and 245 parts by weight of toluene were charged into an autoclave and heated to 150 ° C. in a nitrogen atmosphere. To this, a mixed solution of 5 parts by weight of di-t-butyl peroxide and 76 parts by weight of toluene and a mixed solution of 5.5 parts by weight of 1,3-butadiene and 79 parts by weight of toluene were separately added over 4 hours. Then, the reaction was terminated by aging at 150 ° C. for 1 hour. After cooling, the supernatant solvent was removed, and then steam was blown to remove the residual solvent and at the same time hydrolysis was carried out to obtain a uniform maleic anhydride-1,3-butadiene copolymer aqueous solution having a solid content concentration of 30% by weight.
3 parts by weight were obtained.

The weight average molecular weight of the obtained copolymer by GPC (gel permeation chromatography) was 900, and the content of maleic anhydride unit estimated from CHN elemental analysis was 66 mol%. ..

500 ml of pure water was placed in an Erlenmeyer flask, and the copolymer obtained above had a final solid content of 1.0 ppm.
Then, 10 ml of a 5.88 wt% aqueous solution of calcium chloride and 10 ml of a 3.36 wt% aqueous solution of sodium hydrogen carbonate were added. The pH was adjusted to 8.5 with an aqueous sodium hydroxide solution, and pure water was added to make the total amount 1 l. Seal the Erlenmeyer flask with a stopper and place it in a constant temperature water bath at 40 ° C.
Let stand for 0 hours. Then, the mixture was allowed to cool to room temperature, the supernatant was collected, and the calcium concentration was analyzed by ICP. The scale deposition inhibition rate (%) was calculated by the following calculation formula. The results are shown in Table 1.

Scale deposition inhibition rate (%) = ((A−B) / (C−B)) × 100 (1) A: Calcium concentration in supernatant after test B: In supernatant after test without addition Calcium Concentration C: Calcium Concentration Before Test

Example 2 100 parts by weight of maleic anhydride and 252 parts by weight of toluene were charged into an autoclave and heated to 150 ° C. in a nitrogen atmosphere. To this, a mixed solution of 5 parts by weight of di-t-butyl peroxide and 79 parts by weight of toluene and a mixed solution of 11 parts by weight of 1,3-butadiene and 69 parts by weight of toluene were separately added over 4 hours. Then, the reaction was terminated by aging at 150 ° C. for 1 hour. After cooling, the same procedure as in Example 1 was carried out to obtain 337 parts by weight of a uniform maleic anhydride-1,3-butadiene copolymer aqueous solution having a solid content concentration of 30% by weight.

The weight average molecular weight of the obtained copolymer by GPC was 1100, and the content of maleic anhydride unit estimated from CHN elemental analysis was 64 mol%.

The same operation as in Example 1 was carried out except that the above copolymer was used, and the scale deposition inhibition rate (%) was calculated by the calculation formula (1). The results are shown in Table 1.

Example 3 100 parts by weight of maleic anhydride and 270 parts by weight of toluene were charged into an autoclave and heated to 150 ° C. in a nitrogen atmosphere. To this, a mixed solution of 5 parts by weight of di-t-butyl peroxide and 79 parts by weight of toluene and a mixed solution of 24 parts by weight of 1,3-butadiene and 51 parts by weight of toluene were separately added over 4 hours. Then, the reaction was terminated by aging at 150 ° C. for 1 hour. After cooling, the same procedure as in Example 1 was carried out to obtain 373 parts by weight of a uniform aqueous solution of maleic anhydride-1,3-butadiene copolymer having a solid content concentration of 30% by weight.

The weight average molecular weight of the obtained copolymer by GPC was 1500, and the content of maleic anhydride unit estimated from CHN elemental analysis was 61 mol%.

In the same manner as in Example 1 except that the above copolymer was used, the scale deposition inhibition rate (%) was calculated by the calculation formula (1). The results are shown in Table 1.

Example 4 100 parts by weight of maleic anhydride and 205 parts by weight of toluene were charged into an autoclave and heated to 170 ° C. in a nitrogen atmosphere. To this, a mixed solution of 5 parts by weight of di-t-butyl peroxide and 149 parts by weight of toluene and a mixed solution of 55 parts by weight of 1,3-butadiene and 46 parts by weight of toluene were separately added over 4 hours. Then, the reaction was terminated by aging at 170 ° C. for 1 hour. After cooling, the same operation as in Example 1 was performed to obtain 383 parts by weight of a uniform aqueous solution of maleic anhydride-1,3-butadiene copolymer having a solid content concentration of 30% by weight.

The weight average molecular weight of the obtained copolymer by GPC was 1700, and the content of maleic anhydride unit estimated from CHN elemental analysis was 62 mol%.

In the same manner as in Example 1 except that the above copolymer was used, the scale precipitation inhibition rate (%) was calculated by the calculation formula (1). The results are shown in Table 1.

Example 5 100 parts by weight of maleic anhydride and 205 parts by weight of toluene were charged into an autoclave and heated to 160 ° C. in a nitrogen atmosphere. To this, a mixed solution of 5 parts by weight of di-t-butyl peroxide and 149 parts by weight of toluene and a mixed solution of 55 parts by weight of 1,3-butadiene and 46 parts by weight of toluene were separately added over 4 hours. Then, the reaction was terminated by aging at 160 ° C. for 1 hour. After cooling, the same operation as in Example 1 was carried out to obtain 357 parts by weight of a uniform maleic anhydride-1,3-butadiene copolymer aqueous solution having a solid content concentration of 30% by weight.

The weight average molecular weight of the obtained copolymer by GPC was 2,300, and the content of maleic anhydride unit estimated by CHN elemental analysis was 61 mol%.

The same operation as in Example 1 was carried out except that the above copolymer was used, and the scale deposition inhibition rate (%) was calculated by the calculation formula (1). The results are shown in Table 1.

Example 6 100 parts by weight of maleic anhydride and 205 parts by weight of toluene were charged into an autoclave and heated to 150 ° C. in a nitrogen atmosphere. To this, a mixed solution of 5 parts by weight of di-t-butyl peroxide and 149 parts by weight of toluene and a mixed solution of 55 parts by weight of 1,3-butadiene and 46 parts by weight of toluene were separately added over 4 hours. Then, the reaction was terminated by aging at 150 ° C. for 1 hour. After cooling, the same operation as in Example 1 was carried out to obtain 357 parts by weight of a uniform maleic anhydride-1,3-butadiene copolymer aqueous solution having a solid content concentration of 30% by weight.

The weight average molecular weight of the obtained copolymer by GPC was 4,300, and the content of maleic anhydride unit estimated by CHN elemental analysis was 63 mol%.

The same operation as in Example 1 was carried out except that the above copolymer was used, and the scale deposition inhibition rate (%) was calculated by the calculation formula (1). The results are shown in Table 1.

Example 7 100 parts by weight of maleic anhydride and 265 parts by weight of toluene were charged into an autoclave and heated to 150 ° C. in a nitrogen atmosphere. A mixed solution of 5 parts by weight of di-t-butyl peroxide and 78 parts by weight of toluene and 20.8 parts of isoprene.
A mixed solution of 1 part by weight and 57 parts by weight of toluene was separately added over 4 hours. Then, the reaction was terminated by aging at 150 ° C. for 1 hour. After cooling, the same operation as in Example 1 was carried out to obtain a uniform maleic anhydride having a solid content of 30% by weight.
283 parts by weight of an isoprene copolymer aqueous solution was obtained.

The weight average molecular weight of the obtained copolymer by GPC was 1,600, and the content of maleic anhydride unit estimated by CHN elemental analysis was 69 mol%.

The same operation as in Example 1 was carried out except that the above copolymer was used, and the scale deposition inhibition rate (%) was calculated by the calculation formula (1). The results are shown in Table 1.

Comparative Example 1 25 parts by weight of maleic anhydride and 69 parts by weight of toluene were charged into an autoclave and heated to 150 ° C. in a nitrogen atmosphere. A mixed solution of 0.5 parts by weight of di-t-butyl peroxide and 20.5 parts by weight of toluene and isobutene were added thereto.
A mixed solution of 1 part by weight and 10.5 parts by weight of toluene was separately added over 2 hours. Then, the reaction was terminated by aging at 150 ° C. for 1 hour. After cooling, the obtained copolymer was washed, dried, purified by reprecipitation and then hydrolyzed to obtain 73 parts by weight of a uniform maleic anhydride-isobutene copolymer aqueous solution having a solid content concentration of 30% by weight. ..

The weight average molecular weight of the obtained copolymer by GPC was 1600, and the content of maleic anhydride unit estimated from CHN elemental analysis was 59 mol%.

In the same manner as in Example 1 except that the above copolymer was used, the scale deposition inhibition rate (%) was calculated by the calculation formula (1). The results are shown in Table 1.

Comparative Example 2 The same operation as in Example 1 was carried out except that a commercially available maleic anhydride homopolymer (molecular weight 1200) was used, and the calculation formula (1) was used.
The scale deposition inhibition rate (%) was calculated by. The results are shown in Table 1.

[0065]

[Table 1]

[0066]

The anti-scaling agent of the present invention effectively prevents the precipitation of scales containing calcium as a main component by adding a small amount to an aqueous system. Further, the scale inhibitor of the present invention is derived from cations such as calcium, magnesium, iron and barium, and various anions, such as carbonates, hydroxides, sulfates, silicates and phosphates. It is possible to effectively prevent the occurrence of scale. Further, the copolymer used as the scale inhibitor in the present invention can provide a relatively inexpensive scale inhibitor because the amount of the radical generator used in the production is suppressed as compared with the maleic anhydride homopolymer.

Claims (1)

[Claims] 1. A copolymer of maleic anhydride and an aliphatic conjugated diene, which has a weight average molecular weight of 500 to 10,000 and a maleic anhydride unit content of 40 to 85 mol%.
A scale inhibitor containing a hydrolyzate of a copolymer of: