JPH051287B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing maleic acid copolymers. More specifically, the present invention relates to a method for efficiently producing a copolymer of maleic acid and a certain allyl compound in an aqueous solvent. Conventionally, polymaleic acid and copolymers of maleic acid and other monomers have been used as dispersants, scale inhibitors, and the like. Currently, polymaleic acid is produced in an organic solvent such as toluene or xylene using a peroxide such as benzoyl peroxide as a polymerization initiator. However, from an industrial standpoint, it is much more desirable to carry out production in an aqueous solvent than in an organic solvent, from the viewpoints of simplifying the production process, reducing costs, preventing fires, etc. However, there are almost no examples of research on the polymerization of polymaleate in an aqueous solvent system, and there are only a few examples of copolymers of maleic acid and acrylic acid, vinyl acetate, or the like. When a maleic acid copolymer is used, for example, as a scale inhibitor, various literature reports that lowering the molar ratio of maleic acid in the copolymer results in a decrease in scale inhibiting activity due to a decrease in charge density. It is suggested. Therefore, it is presumed that a maleic acid copolymer with a high maleic acid content would have better scale prevention ability, and there is currently a need for a method for efficiently producing such a copolymer. In view of the current situation, the present inventors have conducted further research on the production of maleic acid copolymers, and have found that maleic acid and allyl copolymers have a high maleic acid content, which was previously thought to be difficult to produce efficiently. The present invention was completed by discovering that a copolymer with a compound can be efficiently produced under certain conditions. That is, the present invention has the general formula [In the formula, R represents hydrogen or a methyl group, and A is
Oh,

[Formula] -SO ₃ H or - SO ₃ M (M represents a monovalent metal, a divalent metal, an ammonium group, or an organic amine group)]] and a repeating structural unit () represented by the general formula (wherein, X and Y each represent hydrogen, a monovalent metal, a divalent metal, an ammonium group, or an organic amine group)
In the method for producing a maleic acid copolymer in which the total amount of () and the total amount of () are within the range of ():() = 5:100 to 40:100 in molar ratio, maleic acid is Aqueous solution containing or maleic acid and the following general formula A method for producing a maleic acid copolymer, which comprises copolymerizing an aqueous solution containing an allyl compound represented by (where R and A are as described above) with a polymerization initiator at a pH of 2.5 to 6.0, and neutralizing if necessary. It provides: To describe the production method of the present invention more specifically, an aqueous solution or suspension of maleic acid or maleic anhydride, or maleic acid and the general formula ()
An aqueous solution or aqueous suspension containing an allyl compound represented by, maleic anhydride, and the allyl compound represented by the general formula () is prepared, and an alkali metal hydroxide, aqueous ammonia, an organic amine compound, etc. are added thereto. Adjust the pH to 2.5 to 6.0. Next, a polymerization initiator is added all at once or continuously to the aqueous solution to advance the copolymerization reaction. The allyl compound represented by the general formula () may be added in its entirety to the maleic acid aqueous solution before the copolymerization reaction,
It may be added continuously using a polymerization nozzle in the form of an aqueous solution. In the present invention, the pH range is 2.5 to 6.0. It is known from calculations that within this range, most maleic acid is in the form of a monosalt (Ishikawa, ``Theory of Acids and Bases'', Sangyo Tosho, p. 22 (1950)).
and the dissociation constant of maleic acid). Maleic acid has a carbon double bond that is positively polarized due to the electron-withdrawing property of the carboxyl group, and when copolymerized with a monomer that has negative polarization, an alternating copolymer is created regardless of the molar ratio of the monomers charged. It is known that it is easy to make (T.Otsu, A.Shimizu, M.Imoto
“Alternative Copolymerization of Butene
Isomers with Maleic Anhydride”J.Polymer
Sci., B2 , pp.973-977 (1964), Masamori Yamada and Iwao Takase, "Study on copolymerization of maleic esters"
Polymer Chemistry, Vol. 18, No. 189, pp. 85-89), and this is considered to be the same in copolymerization with allyl compounds having a negative e value. However, since maleic acid monosalt forms intramolecular hydrogen bonds in an aqueous solution and becomes anionic, alternating copolymerization due to electrostatic interaction does not occur. For this reason, it is considered that within the pH range of the present invention, a copolymer of maleic acid and an allyl compound having a high maleic acid content can be efficiently produced. In the case of maleic acid di-salts, the intramolecular charge becomes large and the repulsion makes mutual polymerization of the di-salts difficult, so it is thought that an alternating copolymer is formed with the allyl compound. The polymerization temperature, monomer concentration, and reaction time during copolymer production are not particularly limited, but the polymerization temperature is preferably in the range of 60°C to 160°C. A practical monomer concentration is 30% by weight or more and 60% by weight or less in terms of solid content, and a suitable reaction time is 2 to 10 hours. Examples of polymerization initiators that can be used in the copolymerization reaction include hydroperoxides such as t-butyl hydroperoxide, persulfates such as ammonium persulfate, hydrogen peroxide, and water-soluble azobis-based initiators. They can be used alone, or in combination of two or more. It is best to use only water as the polymerization solvent, but alcohols such as ethanol and isopropanol, ketones such as methyl ethyl ketone and methyl isobutyl ketone, and esters such as ethyl acetate may be used as long as the yield of the copolymer is not impaired. There is no problem in adding some organic solvents such as. By such a method, a copolymer having the above-mentioned repeating structural unit and copolymerization molar ratio can be efficiently and easily produced. The copolymer obtained by the method of the present invention has a higher maleic acid content than conventional maleic acid copolymers, so it has excellent dispersion ability and ability to trap polyvalent metal ions, and also has a small amount in the molecule. Due to the presence of sulfonic or nonionic groups, it has excellent stability against polyvalent metal ions, and is useful as a scale inhibitor in boilers and seawater desalination, detergent builders, dispersants for inorganic pigments, cement admixtures, etc. . In addition, in the production method of the present invention, copolymers having a molecular weight of 400 to 40,000 are produced particularly efficiently. EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples. Example 1 In a 500 ml stainless steel autoclave, 98 g (1.0 mol) of maleic anhydride, 144 g of water, 103 g (1.03 mol as pure caustic soda) of a 40% aqueous solution of caustic soda, and 31.6 g (0.2 mol) of sodium methallylsulfonate were charged and stirred. At the same time, nitrogen was introduced and the temperature of the system was raised to 90°C. Thereafter, a small amount of the solution was taken, diluted with water, and the pH of the solution was measured to be 4.01 (measurement temperature: 35° C.). Then,
30 g of a 70% t-butyl hydroperoxide aqueous solution as a polymerization initiator was added dropwise to the system over 3 hours using a metering pump, and then stirred at 120°C for 4 hours. The solution was then cooled and treated under the same conditions as above.
When the pH was measured, it was 5.10. Next, water was added to the solution to obtain an aqueous maleic acid copolymer solution with a solid content of 40% (Experiment No. 1). The polymerization rate was determined by quantifying the remaining monomer by the bromine-bromide method. Furthermore, the average molecular weight of the copolymer was measured by gel permeation chromatography. These results are shown in Table-1. Next, as a comparative example, the same method as above was used except that the amount of caustic soda for neutralizing maleic acid was 30 g (0.3 mol) (experiment number 2) and 200 g (2.0 mol) (experiment number 3). The polymer was produced. The polymerization rate and average molecular weight of the obtained copolymer were as shown in Table 1.

【table】

[Table] The same applies to the following examples. Note that molecular weights are not shown for comparative examples due to low polymerization rates. Example 2 294 g (3.0 mol) of maleic anhydride and 228 g of water were added to a flask equipped with a thermometer, stirrer, dropping funnel, nitrogen inlet tube, and reflux condenser, and the mixture was heated under stirring for 40 min.
% caustic soda aqueous solution 309g (as pure caustic soda)
After the system became homogeneous, a small amount of this solution was taken, diluted with water, and the pH was measured as an aqueous solution with a solid content of 3% by weight, and it was found to be 4.12 (measurement temperature: 35°C). Next, 118.5 g (0.75 mol) of sodium methallylsulfonate was added, the temperature of the system was raised to 100°C while nitrogen was introduced, and 25.2 g of sodium persulfate and 144.2 g of 35% hydrogen peroxide solution were added as polymerization initiators. The mixture was added dropwise over 4 hours. 100 minutes after completion of dripping
Stir at ℃ for 1 hour, then add 5.4 g of sodium persulfate and
21.6 g of 35% hydrogen peroxide solution was added at once, aged for 3 hours, and the system was cooled to below 40°C. I took a small amount of the solution and measured its PH under the same conditions as above.
It was 5.12. Next, 40% caustic soda and water were added to obtain a copolymer salt aqueous solution with a solid content of 40% and a pH of 7.5. The polymerization rate of the obtained copolymer,
The average molecular weight was as shown in Table 2 (Experiment No. 4). Next, as a comparative example, the same method as above was used except that the amount of caustic soda for neutralizing maleic acid was 60 g (0.6 mol) (experiment number 5) and 600 g (6 mol) (experiment number 6), respectively. A copolymer was produced. The polymerization rate and average molecular weight of the obtained copolymer were as shown in Table 2.

[Table] Example 3 99g of α-glyceryl monoallyl ether instead of sodium methallylsulfonate used in Example 2
An aqueous solution of a copolymer salt was obtained in the same manner as in Experiment No. 4 of Example 2, except that (0.75 mol) was used. The pH of the solution during the polymerization reaction, the polymerization rate of the copolymer, and the average molecular weight are shown in Table 3 (Experiment No. 7). Example 4 In Example 2, the amount of sodium methallylsulfonate was changed to 189.6 g (1.2 mol), and the same procedure as in Experiment No. 4 of Example 2 was carried out except for that, to obtain an aqueous solution of a copolymer salt. The pH etc. during the polymerization reaction are shown in Table 3 (Experiment No. 8). Example 5 A copolymer aqueous solution was obtained in the same manner as in Experiment No. 1 of Example 1, except that 14.5 g (0.25 mol) of allyl alcohol was used in place of the sodium methallylsulfonate used in Example 1. Table 3 shows PH etc. during polymerization reaction.
(Experiment No. 9).

【table】

Claims (1)

[Claims] 1. General formula [In the formula, R represents hydrogen or a methyl group, and A is -
OH, [formula] -SO ₃ H or - SO ₃ M (M represents a monovalent metal, divalent metal, ammonium group or organic amine group)] and a repeating structural unit () represented by the general formula (In the formula, X and Y each represent hydrogen, a monovalent metal, a divalent metal, an ammonium group, or an organic amine group). In a method for producing a maleic acid copolymer in which the molar ratio is within the range of ():()=5:100 to 40:100, an aqueous solution containing maleic acid or maleic acid and the following general formula Maleic acid copolymerization characterized by copolymerizing an aqueous solution containing an allyl compound represented by (where R and A are as described above) using a polymerization initiator at a pH of 2.5 to 6.0, and neutralizing if necessary. Method for producing polymers.