JP3232610B2 - Scale inhibitor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a scale inhibitor. More specifically, the present invention 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 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. Furthermore, in some cases, zinc ions and phosphate ions may be contained as anticorrosives. 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, cooled, and sometimes the pH changes, so that the ions contained in the water become insoluble salts, deposit on the inner walls of the device, and adhere to the scale, often causing scale. Form. 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.

Therefore, 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, maleic acid-based polymer compounds, for example, a hydrolyzate of a maleic anhydride homopolymer or a hydrolyzate of a maleic anhydride-monoolefin copolymer are known to have an excellent scale preventing effect. (Special Publication 53-20
Nos. 475 and 54-29998, and JP-A-53-700.
Nos. 89 and 60-71093).

[0004]

However, the above-mentioned maleic acid-based polymer compound has not always been satisfactory under severe conditions such as a recent high concentration operation of a cooling water system. In particular, there is room for improvement in the effect of preventing scale containing calcium as a main component. That is, when the concentration of the maleic acid-based polymer was set to a relatively low concentration, it was not possible to effectively prevent the scale containing calcium as a main component.

[0005] Among the maleic acid-based polymer compounds, a 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. Therefore, a hydrolyzate of the produced maleic anhydride homopolymer is also expensive. There was a problem in terms of safety and manufacturing safety.

Accordingly, an object of the present invention is to provide a scale inhibitor which can prevent the formation of a scale mainly composed of calcium or the like even in a low concentration region where the maleic polymer compound cannot effectively prevent scale. .

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

[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 4 to 12 carbon atoms, preferably 4 to 7 carbon atoms,
More preferably, they are 4 to 5 aliphatic conjugated dienes. 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 preferred because they have high reactivity with maleic anhydride, are easily available industrially, and are inexpensive. The copolymer of the present invention may contain one kind of these conjugated diene units, or may contain two or more kinds thereof.

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

Further, the weight average molecular weight of the copolymer is 50
It is suitably from 0 to 10000, preferably from 700 to 5000 from the viewpoint of exhibiting an excellent scale prevention effect. Here, the weight average molecular weight can be determined by measurement by gel permeation chromatography (GPC).

The scale inhibitor of the present invention contains 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.

Further, the hydrolyzate of the copolymer of the present invention is
Alkali metals such as sodium and potassium, calcium,
Salts such as alkaline earth metals such as barium, ammonia and alkylamines may be used. Among them, sodium salts and ammonium salts are preferred.

Hereinafter, a method for producing a hydrolyzate of a copolymer used in the scale inhibitor of the present invention will be described.

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

In the polymerization, the aliphatic conjugated diene is preferably continuously added to a mixture of maleic anhydride and a solvent. This is because if the aliphatic conjugated diene is previously charged together with maleic anhydride and the reaction solvent, the Diels-Alder reaction proceeds during the temperature increase or at the beginning of the polymerization reaction, and the yield may decrease. By continuously supplying the aliphatic conjugated diene, the polymerization reaction can be prioritized over the Diels-Alder reaction. The radical generator may be added in advance to a mixture of maleic anhydride and the reaction solvent, or may be added continuously as in the case of the aliphatic conjugated diene.

Examples of the solvent include 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, dimethylsulfoxide, 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 insoluble, and those in which both maleic anhydride and the copolymer are soluble. With the former type of solvent, the polymerization proceeds as a precipitation polymerization or a suspension polymerization in the presence of a suitable dispersant. On the other hand, when the latter type of solvent is used, it proceeds as solution polymerization. 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 preferred 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 precipitates and is obtained as a precipitate. Therefore, there is an advantage that most of the solvent can be easily separated by removing the supernatant solution after completion of the polymerization reaction, and further, unreacted maleic acid and by-products can be removed at the same time. Further, when producing a hydrolyzate of the copolymer, there is also an advantage that a small amount of 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. Preferably, benzene, toluene and xylene are mentioned.

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

A mixture of maleic anhydride and a solvent or a mixture of this mixture and a radical generator previously charged in a polymerization vessel is heated to a predetermined reaction temperature, and then the aliphatic conjugated diene is added thereto. Preferably, the polymerization is carried out by continuously supplying a solution of the radical generator, if desired. This is because if the aliphatic conjugated diene, maleic anhydride and solvent are previously charged, the Diels-Alder reaction proceeds during the temperature increase or at the beginning of the polymerization, and the yield may decrease. By continuously supplying the aliphatic conjugated diene, the polymerization reaction can be prioritized over the Diels-Alder reaction.

In the present method, the feed 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 is the feed rate of the aliphatic conjugated diene (total moles of conjugated diene / total moles of maleic anhydride / Conjugated diene supply time (hour)).

The aliphatic conjugated diene can be supplied evenly during the polymerization reaction, or the supply 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 radicals are generated in accordance with the supply of the aliphatic conjugated diene, and it is preferable to supply all the radical generators in substantially the same time as the supply time of the conjugated diene. Further, the radical generator can be supplied evenly during the polymerization reaction, or the supply rate can be increased or decreased for controlling the reaction.

The radical generator used in the present 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 decrease, and the Diels-Alder reaction will proceed from the polymerization reaction, leading to a decrease in yield, and it will be necessary to increase the amount of the radical generator used. 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-butyl peroxide and dicumyl peroxide;
Peroxy ketals such as bis (t-butylperoxy) -3,3,5-trimethylcyclohexane can be mentioned.

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 is too small, the polymerization reaction will not proceed effectively, and if it is too large, the molecular weight will be too low, and it is not preferable from an economic viewpoint.

The amounts of the maleic anhydride and the aliphatic conjugated diene can be appropriately adjusted depending on the maleic anhydride units and the aliphatic conjugated diene units of the copolymer.

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

The reaction temperature is preferably 90 ° C. or higher. If the temperature is lower than this temperature, the average molecular weight of the copolymer becomes too high than a desired value, or three-dimensional cross-linking easily occurs, 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 is preferably lower than 180 ° C. in order to obtain the desired average molecular weight of the copolymer. In consideration of 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 terminated when the addition is completed. However, in order to completely consume the unreacted monomer and radical generator, it is preferable to continue the polymerization reaction for a certain period of time, for example, about 30 minutes to 2 hours.

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

The copolymer thus recovered is heated and refluxed with water for a certain period of time, or is subjected to steam distillation by introducing steam to remove the residual solvent and hydrolyze to form an aqueous solution. Can be. However, from an economical and industrial point of view, it is desirable to carry out hydrolysis using water vapor to obtain an aqueous solution. Further, the concentration is preferably 10 to 60% by weight as a solid content.

Further, the hydrolyzate of the copolymer can be converted into a salt, if necessary. The compound used to make the salt is not particularly limited, but examples thereof include alkali metal compounds, alkaline earth metal compounds, and basic substances such as ammonia and alkylamines. As the alkali metal compound and the alkaline earth metal compound, use sodium hydroxide, potassium hydroxide, magnesium hydroxide, and as the alkylamine, use methylamine, ethylamine, aniline, cyclohexylamine, monoethanolamine, ethylenediamine, or the like. Can be. In addition, the above-mentioned basic substance may be allowed to coexist at the time of hydrolysis, and the hydrolyzate may be used to 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 of addition when the water-soluble maleic acid copolymer is used as a scale inhibitor varies depending on the concentration of each ion in water.
By setting the content to 100 ppm, preferably 0.2 to 20 ppm, generation of scale can be effectively prevented.

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

[0038]

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

Example 1 An autoclave was charged with 100 parts by weight of maleic anhydride and 245 parts by weight of toluene, and heated to 150 ° C. in a nitrogen atmosphere. 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 thereto over 4 hours. Thereafter, the mixture was aged at 150 ° C. for 1 hour to terminate the reaction. After cooling, the supernatant solvent was removed, and then steam was blown in to remove the residual solvent. At the same time, hydrolysis was carried out to obtain a uniform aqueous solution of maleic anhydride-1,3-butadiene copolymer having a solid content of 30% by weight.
3 parts by weight were obtained.

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

500 ml of pure water was put into an Erlenmeyer flask, and the obtained copolymer was adjusted to a final solid concentration of 1.0 ppm.
, And 10 ml of a 5.88% by weight aqueous solution of calcium chloride and 10 ml of a 3.36% by weight aqueous solution of sodium hydrogencarbonate were further added. The pH was adjusted to 8.5 with an aqueous sodium hydroxide solution, and pure water was added to adjust the total volume to 1 liter. Close the Erlenmeyer flask and place it in a 40 ° C constant temperature water bath.
It was left 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 precipitation inhibition rate (%) was calculated by the following formula. The results are shown in Table 1.

Scale Deposition Inhibition Rate (%) = ((AB) / (CB)) × 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 An autoclave was charged with 100 parts by weight of maleic anhydride and 252 parts by weight of toluene, and heated to 150 ° C. in a nitrogen atmosphere. A mixture of 5 parts by weight of di-t-butyl peroxide and 79 parts by weight of toluene and a mixture of 11 parts by weight of 1,3-butadiene and 69 parts by weight of toluene were separately added thereto over 4 hours. Thereafter, the mixture was aged at 150 ° C. for 1 hour to terminate the reaction. After cooling, the same operation as in Example 1 was carried out to obtain 337 parts by weight of a uniform aqueous solution of maleic anhydride-1,3-butadiene copolymer having a solid content of 30% by weight.

The weight average molecular weight of the obtained copolymer by GPC was 1,100, and the content of maleic anhydride units estimated from CHN elemental analysis was 64 mol%.

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

Example 3 An autoclave was charged with 100 parts by weight of maleic anhydride and 270 parts by weight of toluene, and heated to 150 ° C. in a nitrogen atmosphere. A mixture of 5 parts by weight of di-t-butyl peroxide and 79 parts by weight of toluene and a mixture of 24 parts by weight of 1,3-butadiene and 51 parts by weight of toluene were separately added thereto over 4 hours. Thereafter, the mixture was aged at 150 ° C. for 1 hour to terminate the reaction. After cooling, the same operation as in Example 1 was performed to obtain 373 parts by weight of a uniform aqueous maleic anhydride-1,3-butadiene copolymer solution having a solid content of 30% by weight.

The weight average molecular weight of the obtained copolymer by GPC was 1,500, and the content of maleic anhydride units estimated from CHN elemental analysis was 61 mol%.

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

Example 4 An autoclave was charged with 100 parts by weight of maleic anhydride and 205 parts by weight of toluene, and heated to 170 ° C. in a nitrogen atmosphere. A mixture of 5 parts by weight of di-t-butyl peroxide and 149 parts by weight of toluene and a mixture of 55 parts by weight of 1,3-butadiene and 46 parts by weight of toluene were separately added thereto over 4 hours. Thereafter, the reaction was aged at 170 ° C. for 1 hour to terminate the reaction. After cooling, the same operation as in Example 1 was carried out to obtain 383 parts by weight of a uniform aqueous maleic anhydride-1,3-butadiene copolymer solution having a solid content of 30% by weight.

The weight average molecular weight of the obtained copolymer by GPC was 1,700, and the content of maleic anhydride units estimated from CHN elemental analysis was 62 mol%.

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

Example 5 An autoclave was charged with 100 parts by weight of maleic anhydride and 205 parts by weight of toluene, and heated to 160 ° C. in a nitrogen atmosphere. A mixture of 5 parts by weight of di-t-butyl peroxide and 149 parts by weight of toluene and a mixture of 55 parts by weight of 1,3-butadiene and 46 parts by weight of toluene were separately added thereto over 4 hours. Thereafter, the reaction was aged at 160 ° C. for 1 hour to terminate the reaction. After cooling, the same operation as in Example 1 was performed to obtain 357 parts by weight of a uniform aqueous maleic anhydride-1,3-butadiene copolymer solution having a solid content of 30% by weight.

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

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

Example 6 An autoclave was charged with 100 parts by weight of maleic anhydride and 205 parts by weight of toluene, and heated to 150 ° C. in a nitrogen atmosphere. A mixture of 5 parts by weight of di-t-butyl peroxide and 149 parts by weight of toluene and a mixture of 55 parts by weight of 1,3-butadiene and 46 parts by weight of toluene were separately added thereto over 4 hours. Thereafter, the mixture was aged at 150 ° C. for 1 hour to terminate the reaction. After cooling, the same operation as in Example 1 was performed to obtain 357 parts by weight of a uniform aqueous maleic anhydride-1,3-butadiene copolymer solution having a solid content of 30% by weight.

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

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

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

The weight average molecular weight of the obtained copolymer by GPC was 1600, and the content of maleic anhydride units estimated from CHN elemental analysis was 69 mol%.

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

Comparative Example 1 An autoclave was charged with 25 parts by weight of maleic anhydride and 69 parts by weight of toluene, and heated to 150 ° C. in a nitrogen atmosphere. A mixture 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 mixture of 1 part by weight and 10.5 parts by weight of toluene were separately added over 2 hours. Thereafter, the mixture was aged at 150 ° C. for 1 hour to terminate the reaction. 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 of 30% by weight. .

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

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

Comparative Example 2 The procedure of Example 1 was repeated, except that a commercially available maleic anhydride homopolymer (molecular weight: 1200) was used.
The scale precipitation inhibition rate (%) was calculated by the following formula. The results are shown in Table 1.

[0065]

[Table 1]

[0066]

The scale inhibitor of the present invention can effectively prevent the precipitation of scale containing calcium as a main component only 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. The generation of scale can be effectively prevented. 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 homopolymer of maleic anhydride.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-54-76690 (JP, A) JP-A-53-70089 (JP, A) JP-A-60-71093 (JP, A) 29998 (JP, B2) (58) Field surveyed (Int. Cl. ⁷ , DB name) C08F 8/12 C08F 222/06 C08F 236/04

Claims (1)

(57) [Claims] 1. 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%.
A scale inhibitor containing a hydrolyzate of a copolymer represented by the formula: