JPH0465408A - Production of aqueous solution of maleic anhydride copolymer or copolymer salt - Google Patents

Abstract

PURPOSE:To obtain the subject copolymer useful as an antiscaling agent in the form of an aqueous solution of salt, in high yield and reproducibility, by copolymerizing butadiene and maleic anhydride in an aromatic hydrocarbon solvent using a specific polymerization process. CONSTITUTION:The objective copolymer having a weight-average molecular weight of <=4,000 and containing maleic anhydride and butadiene at a molar ratio of >=1.2 can be produced by continuously adding butadiene to a mixture of maleic anhydride and an aromatic hydrocarbon solvent (preferably benene, etc.) under a condition satisfying the formula [Y is action temperature ( deg.C); X is feeding rate of butadiene (total molar number of butadiene/total molar number of maleic anhydride/total feeding time of butadiene) and is >=0.07] and continuously adding a radical generator (preferably t-butyl-2-ethylehexanoate, etc.) independent of the addition of the butadiene and polymerizing the components.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention provides a method for producing a copolymer of maleic anhydride and butadiene that has a relatively low molecular weight and a high content of maleic anhydride, and a method for preventing scale. The present invention relates to a method for producing an aqueous solution hydrolyzate of a maleic anhydride copolymer or a salt thereof, which is useful as an agent.

[Conventional technology]

Aqueous solutions of polymaleic anhydride and maleic anhydride copolymers are useful as scale inhibitors for cooling water systems, boiler equipment, and seawater desalination equipment, as dispersants for inorganic substances and pigments, and as fluidizing agents for concrete. It is known that this is the case [JP-A-60-71093].

The present inventors have conducted various studies on new aqueous solutions of maleic anhydride copolymers useful as scale inhibitors, etc., and have selected maleic anhydride-butadiene copolymer aqueous solutions that have particularly excellent physical properties as scale inhibitors, etc. I found that. According to the studies of the present inventors, the scale inhibitor, etc. must have a molar ratio of maleic anhydride to butadiene of 1.2 or more, and a weight average molecular weight of 4000 or less in order to exist stably as an aqueous solution. It is preferable that

However, maleic anhydride-butadiene copolymers were already known for use in molded products, or copolymers for use in aqueous solutions, which need to have a much lower molecular weight than copolymers for molded products, had not been studied. There was no. Therefore, a method for producing a copolymer satisfying the above conditions in good yield has not been known so far.

A conventionally known method for producing a copolymer of butadiene and maleic anhydride is a method of radical polymerization using a radical generator.

For example, Japanese Patent Publication No. 46-31972 describes a method for copolymerizing a diolefin containing butadiene and maleic anhydride. This method suppresses the Diels-Alder reaction between diolefins and maleic anhydride (in the Diels-Alder reaction, no copolymer is produced, but tetrahydrophthalic anhydride is produced as a by-product), and a 1.1 alternating copolymer is produced. It is characterized by polymerization at a temperature such that the half-life of the radical generating catalyst is 60 minutes or less. However, in the example of polymerization of butadiene and maleic anhydride, the yield of the polymer was extremely low.

Japanese Patent Publication No. 47-45954 describes a method of radical polymerizing butadiene and maleic anhydride in the presence of a solvent. However, it has been shown that polymerization in poor solvents using aromatic hydrocarbon solvents as solvents, such as copolymers such as benzene, produces three-dimensionally crosslinked polymers that are insoluble even in polar solvents such as dimethylformamide. .

Furthermore, in Japanese Patent Publication No. 58-35205, in the production of 11 alternating copolymers of butadiene and maleic anhydride, maleic anhydride and a radical-generating catalyst are prepared in advance, and butadiene is added to a compound with 1/2 of the half-life of the orchidyl-generating catalyst. A method has been shown for producing polymers in high yields by continuously feeding for more than 4 times longer and more than 2 times longer. The type of solvent is not particularly limited. However, Examples 7 and 8 show examples in which benzene was used as the aromatic hydrocarbon solvent. However, the intrinsic viscosity, which indicates molecular weight, has not been shown.
According to the results of additional tests conducted by the present inventors, a large amount of three-dimensionally crosslinked polymer was produced.

[Problem to be solved by the invention]

As mentioned above, in the known radical copolymerization reaction of butadiene and maleic anhydride, a 1:1 alternating copolymer can be selectively obtained, and a copolymer with a high maleic anhydride content, which is the object of the present invention, can be selectively obtained. It was not possible to produce a combination.

Furthermore, in the present invention, the weight average molecular weight of the copolymer needs to be 4000 or less, considering the water solubility of the copolymer. However, the method described in the above publication is for producing a copolymer with a high molecular weight, and it was not possible to produce a copolymer having a weight average molecular weight of 4000 or less.

By the way, in the copolymerization of butadiene and maleic anhydride in a copolymer-soluble solvent such as a ketone solvent and a cyclic ether, a three-dimensionally crosslinked polymer is not produced, but the copolymer is obtained as a uniform solution. Therefore, after the polymerization reaction is completed, the reaction mixture must be poured into a poor solvent to reprecipitate and recover the polymer. Furthermore, soluble solvents are industrially disadvantageous because it is often difficult to remove the solvent remaining in the copolymer when the copolymer is made into an aqueous solution.

On the other hand, when copolymerizing butadiene and maleic anhydride,
monomer soluble, such as aromatic hydrocarbon solvents;
When a solvent that is a poor solvent for a copolymer is used, the copolymer precipitates out during the reaction 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 the polymerization reaction is completed. but,
When aromatic hydrocarbons are used in @ medium, three-dimensionally crosslinked polymers are formed. This crosslinked polymer does not dissolve even in polar solvents, and of course does not dissolve in water. Therefore, considering the water solubility of the copolymer, in addition to having a weight average molecular weight of 4000 or less, the copolymer must not contain a three-dimensionally crosslinked copolymer that is insoluble even in polar solvents.

However, until now, no method has been known for producing a copolymer of butadiene and maleic anhydride while preventing the formation of a crosslinked polymer using an aromatic hydrocarbon solvent.

Therefore, the object of the present invention is to use an aromatic hydrocarbon solvent as a reaction solvent, to achieve a molar ratio of maleic anhydride to butadiene of 2 or more, a weight average molecular weight of 4000 or less, and a copolymer-soluble solvent. The object of the present invention is to provide a method for producing a butadiene maleic anhydride copolymer containing no insoluble copolymer with good reproducibility.

A further object of the present invention is to provide a method for producing a butadiene-maleic anhydride copolymer in a high yield while suppressing the by-product of the Diels-Alder adduct of butadiene and maleic anhydride. It's about doing.

Furthermore, an object of the present invention is to provide an aqueous solution containing a hydrolyzate of the above copolymer or a salt thereof.

[Means to solve the problem]

The present invention provides a mixture of maleic anhydride and an aromatic hydrocarbon solvent with Y > 280 Continuously add butadiene under conditions that satisfy the following equation (number/total butadiene supply time), where x is a number of 0.07 or more), and continuously add a radical generator independently of butadiene. The present invention relates to a method for producing a copolymer of maleic anhydride and butadiene, which has a weight average molecular weight of 4000 or less and a molar ratio of maleic anhydride to butadiene of 1.2 or more.

Furthermore, the present invention relates to a method for producing an aqueous solution of a hydrolyzate of a copolymer and a salt thereof, which includes hydrolyzing the above copolymer.

The present invention will be explained in detail below.

The copolymer that is the object of the present invention has a weight average molecular weight of 4.
000 or less, preferably 1000 or more, more preferably 1500 to 3500, and the molar ratio of maleic anhydride to butadiene is 1.2 or more, preferably 3 or less, more preferably 1.5 to 2. By setting the weight average molecular weight and molar ratio within the above range, the aqueous solution has excellent physical properties as a scale inhibitor.

In the method of the present invention, a radical generator and butadiene are independently and continuously added to a mixture of maleic anhydride and an aromatic hydrocarbon solvent.

The solvent used in the present invention is an aromatic hydrocarbon solvent. The aromatic hydrocarbon solvent is a poor solvent for the copolymer, and the copolymer is precipitated and obtained as a precipitate. Therefore, it has the advantage that most of the solvent can be easily separated from the copolymer by removing the supernatant after the completion of polymerization. Furthermore, such aromatic hydrocarbon solvents have the advantage that when producing an aqueous solution of a copolymer or its salt, a small amount of solvent remaining in the system can be easily removed as an azeotrope with water. be.

In the present invention, examples of aromatic hydrocarbon solvents include alkyl-substituted benzenes such as benzene, toluene, xylene, ethylbenzene, and cumene, and halogen-substituted benzenes such as chlorobenzene and bromobenzene. Preferred are benzene, toluene and xylene.

There is no particular limitation on the amount of solvent used. However, from the viewpoint of suppressing local and rapid reactions, it is appropriate to use, for example, 50 to 500 parts by weight of the aromatic hydrocarbon solvent per 100 parts by weight of maleic anhydride.

A mixture of maleic anhydride and an aromatic hydrocarbon solvent, which had been charged in advance in a polymerization container, was heated to a predetermined reaction temperature, and then a solution of a radical generator and butadiene was continuously supplied to carry out polymerization. implement. Here butadiene,
If maleic anhydride and a solvent are charged in advance, the Diels-Alder reaction will proceed during heating or in the early stages of polymerization, which is undesirable because the yield will decrease. By continuously supplying butadiene, it becomes possible to prioritize the polymerization reaction over the Diels-Alder reaction. Furthermore, if maleic anhydride, a radical generator, and a solvent are charged in advance, a large amount of radicals will be generated within a short period of time. Therefore, unnecessarily high molecular weight and three-dimensional crosslinking reactions tend to occur, making it impossible to obtain the copolymer targeted by the present invention in high yield. Furthermore, since a large amount of reaction heat is generated in the initial stage of polymerization, it is not easy to control the polymerization temperature.

In the present invention, butadiene is continuously supplied so as to satisfy the condition of Y>280X-80.

That is, if the reaction temperature (0C) Y is high, the butadiene supply rate X can be increased. Note that X is a value obtained by dividing the number of moles of butadiene used in the reaction per mole of maleic anhydride used in the reaction by the total butadiene supply time. By adjusting the butadiene feed rate under these conditions,
The desired copolymer can be obtained with good reproducibility.

Although the desired copolymer may sometimes be obtained under conditions where the reaction temperature Y is equal to or lower than 280X''-80, the reproducibility is poor and this is not practical.

In addition, butadiene can be supplied evenly during the polymerization reaction, or can be increased or decreased in order to control the reaction, as long as it is within the range that satisfies the above conditions. .

Moreover, X is a number of 0.07 or more. This is because under temperature conditions where X is less than 0.07, the molecular weight of the copolymer becomes too large than the desired value or three-dimensional crosslinking occurs, making it impossible to use it as a water-soluble copolymer.

On the other hand, there is no particular limitation on the upper limit of the reaction temperature.

However, it is preferable to set the temperature to less than 180°C from the viewpoint that the weight average molecular weight of the resulting copolymer does not become too small. If the weight average molecular weight of the copolymer and the reaction temperature are low, the butadiene supply rate will be slow, so when considering the reaction time, the reaction temperature should be 130°C to 160°C.
The range of C is preferable.

On the other hand, there is no particular limitation on the supply rate of the radical generator. The radical generator only needs to be continuously supplied.

However, it is preferable that radicals be generated in synchronization with the supply of butadiene, and it is preferable that all the radical generators be supplied in approximately the same time as the supply time of butadiene. Furthermore, the radical generator can be supplied evenly during the polymerization reaction, or the supply rate can be increased or decreased in order to control the reaction.

The radical generator used in the present invention 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 long, the amount of radicals generated per unit time will decrease, and the Diels-Alder addition reaction will proceed more than the polymerization reaction, leading to a decrease in yield. Therefore, is it necessary to increase the amount of radical generator used? It's not really effective.

At temperatures above about 90°C, which is the reaction temperature range, the half-life is 1.
Examples of the Rancar generator for less than 1 hour include peroxy esters such as t-butyl-2-ethylhexanoate and butyl peroxybenzoate, and dialkyl peroxides such as di-t-butyl peroxide and dicumyl peroxide. .

The amount of the radical generator to be used is determined in consideration of the supply time of the radical generator, etc. For example, a suitable amount is 0.1 to 10% by weight, preferably 1 to 5% 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 also unfavorable from an economic standpoint.

The amount of butadiene to be used varies depending on the use of the obtained copolymer, but it is preferably used in an amount equal to or less than 0.2 to 1.0 moles relative to maleic anhydride. If the amount of butadiene added is equal to or more than the molar amount relative to maleic anhydride, it is undesirable because high molecular weight and three-dimensional crosslinking reactions tend to occur. If the amount is less than 0.2 moles, the polymerization reaction may not proceed smoothly, resulting in a decrease in yield.

Butadiene and the radical generator can be supplied as such or as a mixture with an aromatic hydrocarbon solvent. However, from the viewpoint of suppressing local rapid reactions, it is preferable to supply a mixture with an aromatic hydrocarbon solvent. The mixing ratio (weight ratio) with aromatic hydrocarbon solvent is
It is appropriate to use 50 to 500 parts by weight of the aromatic hydrocarbon solvent per 100 parts by weight of butadiene, and 500 to 5000 parts by weight to 100 parts by weight of the radical generator.

Since the polymerization reaction is almost completed after the addition of butadiene and the radical generator is completed, the polymerization reaction may be completed at the same time as the addition is completed. However, in order to completely consume unreacted monomers and radical generators, it is possible to continue the polymerization reaction for a certain period of time, for example, about 30 minutes to 2 hours.

The copolymer thus obtained can be hydrolyzed into an aqueous solution by heating under reflux with water for a certain period of time or by heating with steam. However, from an economical and industrial standpoint, it is desirable to hydrolyze it using steam to form an aqueous solution. The operating conditions for hydrolyzing the copolymer with water vapor are not particularly limited. However, it is desirable to prepare the aqueous solution of the copolymer while adjusting the amount of water vapor introduced and extracted and the amount of heating of the solution so that the final solid content concentration is about 10 to 50% by weight.

Furthermore, since the solvent remaining in the solid content is distilled off as an azeotrope at the same time as the hydrolysis, it is desirable that the time for hydrolysis with water vapor is a time that allows sufficient distillation of the solvent. Note that the amount of residual solvent in the aqueous solution can be easily analyzed by gas chromatography or liquid chromatography.

Furthermore, the aqueous solution of the hydrolyzate of this copolymer can be converted into a salt if necessary. Although the type of salt is not particularly limited, examples include metal salts, ammonium salts, and amine salts.

Amine salts include methylamine, ethylamine, aniline,
It can be prepared using cyclohexylamine, monoethanolamine, ethylenediamine, etc. Metal salts can also be obtained by neutralizing the copolymer hydrolyzate using an alkali metal hydroxide or alkaline earth metal hydroxide such as sodium hydroxide, potassium hydroxide, or magnesium hydroxide. .

〔Effect of the invention〕

According to the present invention, the molar ratio of maleic anhydride to butadiene is 1.2 or more and the weight average molecular weight is 4000 or less, which is suitable for preparing an aqueous maleic anhydride copolymer solution useful as a scale inhibitor, etc. A maleic anhydride-butadiene copolymer can be produced in high yield and with good reproducibility. Furthermore, according to the method of the present invention, it is possible to provide a copolymer that does not contain a three-dimensionally crosslinked polymer that would impede its formation into an aqueous solution.

The present invention will be explained in more detail with reference to Examples below.

Example 1 30 g of maleic anhydride and 48.6 g of toluene were charged into a 200-glass autoclave equipped with a stirrer, and the inside was purged with nitrogen. The solution was heated to 100°C. After the solution stabilized at 100°C, while stirring the solution, a solution of 4.15 g of butadiene dissolved in 30.8 g of toluene and 1.5 g of t-butylperoxy(2-ethylhexanoate) were added. A solution of 40.6 g of toluene was added continuously over a period of 4 hours (butadiene feed rate=0°0625 mol 1 mol/hour). After the addition of the solution of butadiene and the radical generator was completed, stirring was continued for another hour while maintaining the temperature at 100°C. After the reaction is complete, the reaction solution is cooled to room temperature and the supernatant is separated.
A pale yellow lumpy copolymer was obtained. The weight average molecular weight of this solid content measured by gel permeation chromatography using tetrahydrofuran as an eluent was 2200 in terms of polystyrene. Moreover, from this, the yield of the copolymer excluding the solvent and unreacted monomer in the solid content is 25
．． 5g (yield 74.6%).

This solid content was charged into a 500-cm autoclave equipped with a steam introduction tube, a stirrer, and a condenser, and the introduction of steam was started while heating the solution.

An azeotropic mixture of toluene and water began to condense in a portion of the capacitor at around 86°C, and when the temperature was raised to about 100°C, almost no solvent was flowing out. After the temperature was raised, introduction of water vapor and extraction using a condenser were continued for another 2 hours, and the solvent was sufficiently distilled off. Cool the aqueous solution to room temperature and solid content concentration 3
5% butadiene-maleic anhydride copolymer aqueous solution 72
．． 9 g was obtained.

Examples 2 to 7 and Comparative Examples 1 to 11 The experiments were carried out except that the molar ratio of butadiene/maleic anhydride used, the reaction temperature, the type and supply time of the radical generator, and the time and supply rate of butadiene were set as shown in Table 1. Copolymerization of butadiene and maleic anhydride was carried out under the same conditions as in Example 1.

In addition, the molecular weight of the comparative example is the measurement result of the copolymer excluding the THF-insoluble content, and is written in parentheses.

Comparative Example 12 In a 2007nl glass autoclave equipped with a stirrer, 30 g of maleic anhydride and 1 t-butyl peroxide were added.
．． 5 g and 89.2 g of toluene were charged, the inside was replaced with nitrogen, and the temperature of the solution was quickly raised to 140°C.

After stabilizing at 140℃, 8.3g of butadiene was added to 3g of toluene.
A solution of 0.8 g was added continuously over 1.7 hours while stirring the inside. After the addition of the butadiene solution was completed, stirring was continued for another hour while maintaining the temperature at 110°C. After the reaction was completed, the reaction solution was cooled to room temperature and the supernatant was separated to obtain a reddish-brown lumpy copolymer. This solid content was dissolved in tetrahydrofuran, but the insoluble content was 9.2
% Ah 1.

Comparative Examples 13 and 14 Butadiene and anhydride were prepared under the same conditions as in Comparative Example 12, except that the molar ratio of butadiene/maleic anhydride used, reaction temperature, type of radical generator, and butadiene time were as shown in Table 1. Copolymerization of maleic acid was carried out. The results are shown in Table 1.

From the results of Examples 1 to 7 and Comparative Examples 1 to 11, the relationship between the butadiene supply rate (X) and the reaction temperature (Y) is shown in FIG. In Fig. 1, ○ indicates an example of the present invention, △ indicates a comparative example, and it may be 0 if it is insoluble in THF, but if it is not reproducible, X is a comparative example and always indicates a THF-insoluble content. Indicates when to generate.

[Brief explanation of drawings]

Figure 1 shows the butadiene supply rate (X) and reaction temperature (Y
). 1゜2゜3゜4゜Indication of procedural amendment date case 1990 Patent Application No. 1, Title of invention related to the case of the person making the amendment No. 6

Claims (2)

[Claims] (1) In the mixture of maleic anhydride and aromatic hydrocarbon solvent, Y > 280 /butadiene total supply time), and X is 0.07
the weight average molecular weight is 4.
000 or less, and the molar ratio of maleic anhydride to butadiene is 1.2 or more. (2) A method for producing an aqueous solution of a hydrolyzate of a maleic anhydride copolymer and a salt thereof, which comprises hydrolyzing the copolymer obtained by the production method according to claim 1.