JPS5912908A - Novel copolymer and preparation thereof - Google Patents

Abstract

PURPOSE:To obtain a novel copolymer, containing no residual monomer, and useful as a scale inhibitor for magnesium hydroxide, etc., by copolymerizing maleic acid or fumaric acid with ethylene glycol monoallyl ether. CONSTITUTION:Maleic acid or fumaric acid is copolymerized with ethylene glycol monoallyl ether in water or an alcohol in the presence of a polymerization initiator, e.g. ammonium persulfate, and if necessary treeted with an alkaline substance to give the aimed copolymer containing units expressed by formulas I and II at (1/9)-(9/1), preferably (3/7)-(7/3), molar ratio.

Description

Detailed Description of the Invention The present invention has the following structural units (1) and (2), and (2)
1-CH□-CH- CH20-CH2C1-J2' OH The above structural unit (
A copolymer having a molar ratio of 1) and (2) of 1:9 to 9:1 and maleic acid or fumaric acid toethylene glycol monoallyl ether are copolymerized using water or alcohol as a solvent, and the necessary This invention relates to a method for producing a copolymer or a salt thereof, which is further treated with an alkaline substance. The copolymer of the present invention or its salt is water-soluble.

In recent years, population growth has led to water shortages in various regions of the world, and the acute shortage of drinking water is especially noticeable in desert-rich Middle Eastern countries and remote islands. It is considered a strategy. However, in order to desalinate seawater and convert it into fresh water using various methods, it is necessary to suppress the precipitation of inorganic salts and metal hydroxides (hereinafter abbreviated as inorganic salts) contained in seawater.

Since these inorganic salts have low solubility in water, they tend to precipitate, causing clogging of semipermeable membranes in reverse osmosis and a decrease in heat conduction in distillation. In addition, similar to the distillation method for seawater desalination, various inorganic salts contained in seawater or freshwater are used in air conditioners, refrigerators, evaporators, etc. that use seawater or freshwater in various cooling circuits with heat transfer surfaces. Precipitates precipitate and reduce heat conduction. As a result, production efficiency decreases and the equipment must be stopped to clean or replace the semipermeable membrane or heat exchanger.

These deposited precipitates are usually called scale, and various scale prevention methods and scale inhibitors are being studied. Specifically, methods include controlling pH to suppress scale precipitation, using surfactants to prevent deposited scale from adhering, and using scale inhibitors made of phosphoric acid compounds or polycarforonic acids. There are methods to prevent scale precipitation.

A similar effect can be expected by using a chelating agent, but
The chelating agent must be used in an amount equivalent to the cation of the precipitated inorganic salt. On the other hand, scale inhibitors have the effect of suppressing or significantly delaying the precipitation of sediment even when added in small amounts.

Recently, various polycarboxylic acids have been developed as scale inhibitors. Specifically, it is a polymer of acrylic acid, methacrylic acid, and maleic anhydride, a copolymer with a monomer copolymerizable with these, a hydrolyzate thereof, or a salt thereof. Specific examples include hydrolysates of maleic anhydride polymers, hydrolysates of maleic anhydride-vinyl acetate copolymers, hydrolysates of maleic anhydride-styrene copolymers, acrylic acid polymers, and acrylics. Examples include acid copolymers, methacrylic acid polymers, and methacrylic acid copolymers.

On the other hand, various ions such as alkaline earth metal salts such as calcium carbonate and magnesium hydroxide, bicarbonate ions, carbonate ions, and sulfate ions are present in seawater, and these ions are bound together depending on the evaporation conditions of desalination. There is a critical temperature at which salts can precipitate. It is known that calcium carbonate is the main component at temperatures below 82C, magnesium hydroxide is the main component at temperatures above 93C, and calcium sulfate is difficult to form at temperatures below 1211:'.

Among these scales, the scale caused by calcium carbonate, which precipitates at relatively low temperatures, can be suppressed with a number of effective scale inhibitors.For example, among polycarboxylic acids, it can be controlled with acrylic acid and methacrylic acid scale inhibitors. . However, at present, there has not been a satisfactory solution to the problem of a scale inhibitor that prevents the scale of magnesium hydroxide that precipitates at high temperatures. Among polycarboxylic acid-based scale inhibitors, the hydrolyzate of maleic anhydride-based polymers is relatively effective in preventing the scale of not only calcium carbonate but also magnesium hydroxide, and it clearly delays scale formation. It is known that it has the effect of However, since maleic anhydride is an acid anhydride, in the presence of water it undergoes calohydrolysis to become maleic acid.
Generally, it is necessary to polymerize in an organic solvent and then hydrolyze it to dissolve it in water, resulting in high costs and problems with the remaining organic solvent.

Therefore, the present inventors investigated various copolymerizable monomers that can be copolymerized in an aqueous solvent using a hydrolyzed monomer, maleic acid, or its isomer, fumaric acid, rather than in the form of maleic anhydride. As a result, the present invention was completed.

In general, maleic anhydride is a monomer that is difficult to homopolymerize, and it is known that a polymer with a low degree of polymerization can be obtained by polymerizing it in an organic solvent or in a molten state, but a polymer with a high molecular weight can be obtained. Not obtained. 1.Although it is known that alternating copolymers can be obtained by copolymerization with electron-donating monomers such as styrene, vinyl ether, imbutylene, and vinyl acetate, all of these are carried out in non-aqueous systems. When maleic anhydride is polymerized in an aqueous solvent, the anhydride is hydrolyzed to maleic acid, and a polymer is hardly obtained. In the case of copolymerization, copolymerization is possible with a small amount of maleic acid, but if a large amount is used, a residual monomer remains and an operation to remove maleic acid is required.

The present inventors attempted copolymerization with the monomer ethylene glycol monoallyl ether, which is copolymerizable in an aqueous solvent, and surprisingly, the polymerization proceeded almost completely. A copolymer was obtained, and even if the composition ratio of ethylene glycol monoallyl ether and maleic acid was changed, a copolymer with no residual monomer was obtained.As shown in the test example, the effect as a scale inhibitor was It has been found that this method has a significant effect on magnesium oxide scale.

It has also been found that copolymerization proceeds in the same way when an alcohol solvent is used instead of water.

Further, in place of maleic acid, copolymerization in an organic solvent such as fumar or dioxane is an example in which maleic anhydride and allyl alcohol or meta-allyl alcohol are used. Makro-molekt+1. chem l
49 51 (1971), and the obtained polymer is an alternating copolymer, and simultaneously with the polymerization, an ester bond is formed in the molecule with an adjacent acid anhydride and alcohol to form a 6-membered lactone ring. Therefore, a polymer having alternating carboxyl groups and lactone rings has been obtained. However, when copolymerization is performed using maleic anhydride and ethylene glycol monoallyl ether according to the method described in the literature, cyclization does not occur within the molecule, but ester bonds are formed between the molecules, resulting in crosslinking, and ultimately, gel-like polymerization occurs. things were generated. Therefore, the polymerization according to the present invention is characterized by the combination of a specific monomer and a specific solvent (water, alcohol), and by using water or alcohol as a solvent, esterification between molecules is prevented and a gel-like product is produced. It seems that this is making it difficult to do.

When using an aqueous solvent in the method according to the present invention, maleic anhydride may be used instead of maleic acid, and in the case of maleic anhydride, it is hydrolyzed in water as a solvent to form maleic acid. In the case of alcoholic solvents, maleic anhydride cannot be used because it forms esters.

Moreover, this copolymer of maleic acid or fumaric acid and ethylene glycol monoallyl ether can be similarly used in the form of a salt.

The copolymer or salt thereof of the present invention has the following structural units (1) and (2).

(21-CH2-CH- CH2-0-CH□-co2-O11 Regarding the copolymerization composition ratio of the above structural units (1) and (2), the molar ratio of the above structural units (1) and (2) is 1 :9~9:
It is preferable to set it as the range of 1. Note that it is preferable that the amount of the structural unit (11) is larger than that of (2) because the scale prevention effect is greater and there is almost no residual ethylene glycol monoallyl ether during copolymerization. ) and (2) copolymerization composition ratio is 3;7~
The range is 7:3 (molar ratio).

In particular, the salts of the copolymer of the present invention include alkali metal salts,
Ammonium salts and organic amine salts (methylamine, trimethylamine, triethylamine, etc.) are preferred. Salts of copolymers can be easily obtained, for example, by neutralizing or partially neutralizing the carboxyl groups of copolymers with an appropriate amount of alkali, ammonia, organic amines, etc. Salts of these copolymers can also be obtained in the same way. It can be used as a scale inhibitor.As an alkali, it is an economical hydroxide).
Jum is most preferred.

The copolymer of the present invention can be produced by a general aqueous solution polymerization method using water as a solvent.

For example, it can be produced by adding raw material monomers to an aqueous solvent and polymerizing in the presence of a polymerization initiator, and the salt of the copolymer can be produced by further treating with an alkaline substance.

As a polymerization initiator, most water-soluble radical initiators can be used, including persulfates used in aqueous solution polymerization, such as ammonium persulfate, potassium persulfate, azobisamidinopropane hydrochloride, etc. . Further, a redox initiator using a combination of a reducing agent such as acidic sodium sulfite or sodium thiosulfate and a persulfate can also be used.

In addition, when copolymerization is carried out using alcohol instead of water as a solvent, the polymerization can be carried out in the same manner as in the case of aqueous solution polymerization, and methanol, ethanol, and isopropyl alcohol are suitable as the alcohol, and alcohols that are insoluble in water are preferable. do not have.

In the case of an alcohol solvent, the polymerization initiator is an organic peroxide,
Most alcohol-soluble initiators including azo compounds can be used, such as benzoyl peroxide,
Azobisisobutyronitrile and the like can be used.

In addition, the polymerization temperature varies depending on the type of polymerization initiator, but
The preferable polymerization temperature is 30C to 100C because the degree of polymerization is lower at a relatively high temperature.

The average molecular weight (number average molecular weight) of the copolymer or salt thereof of the present invention is preferably in the range of 800 to 100,000, particularly preferably in the range of 2,000 to 30,000.

The copolymer of the present invention or its salt may contain other copolymer components. That is, in producing the copolymer of the present invention or its salt, it is also possible to copolymerize by adding other copolymerizable monomers as a third component, such as acrylic acid, methacrylic acid, acrylamide, 2-hydroxy Hydrophilic monomers such as methacrylate can be used.

Also, alkyl acrylate, alkyl methacrylate,
Hydrophobic monomers such as vinyl acetate and styrene can also be used in small amounts, and it is also possible to use two or more of these components in combination.

These third components are preferably used within a range that maintains the water solubility of the obtained copolymer or its salt, and the content of the third component is preferably 40% by weight or less, particularly 20% by weight or less. is preferred.

When the copolymer of the present invention or a salt thereof is used as a scale inhibitor, the amount used is preferably about 2 to 100 ppm, and generally from 5 to 50 ppm from the economic point of view.
is used.

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

Example 1.

350 ml of maleic acid in a 114-necked reactor equipped with a reflux condenser and a stirring device. Add 4'401 of water to dissolve and raise the temperature to 100C. During this time, about 5 tons of nitrogen gas is passed through to drive out oxygen. Nitrogen gas is continued to flow in small amounts until the polymerization is completed. Next is ethylene glycol monoallyl ether 150? and 50 g of a 20% aqueous solution of ammonium persulfate were each added dropwise over 2 hours. After the dropwise addition was completed, the temperature was kept at 100C for 1 hour, and then a 5% aqueous solution of ammonium persulfate was added at 10°C. was added, and the polymerization was completed in 1 hour. The obtained polymer was an aqueous solution with a solid content of 50%, and was used as it was in the trench scale inhibitor test. The results are shown in the test example.

The properties of the produced copolymer are shown in Table 1.

Example 2.

Maleic anhydride 3002, water 4
40F! - and heated to 100C to dissolve and hydrolyze maleic anhydride to form maleic acid. Thereafter, ethylene glycol monoallyl ether 2001 was copolymerized in the same manner.

Example 3.

In the same manner as in Example 1, 35 oz of fumaric acid and 150 g of ethylene glycol monoallyl ether were copolymerized.

The aqueous polymer solutions obtained in Examples 2 and 3 were used as they were in the test as a scale inhibitor. The results are shown in the test example. Further, the properties of the produced copolymer are shown in Table-1.

Table-1 Viscosity = Type B rotational viscometer average molecular weight: Shimadzu high performance liquid chromatography LC-3A
Type column: 5hodex 0I-I PaK B-8
05+3-803 Carrier: KH2P O40, 2% aqueous solution flow rate:
0.8ml! 7m1n Detector: Differential refractometer Standard material: Sodium polystyrene sulfonate Infrared absorption spectrum Ryotsu infrared spectrophotometer IR-27 type K) 3
r tablet method + 3cm NM 几spectrum JEOL FX-6ONMI
% Spectrometer 13C Resonance Frequency 15.03 MHz Reference
Dioxane solvent D20 Concentration 12.5% Example 4゜Maleic acid 350゜ using the same device as Example 1. , and ethylene glycol monomer ether 150 P, ethyl alcohol 400? Add and dissolve, and heat to reflux temperature on a water bath. During that time, about 50% of air gas is passed through to drive out oxygen. Continue to flow nitrogen gas little by little until polymerization is complete.

Subsequently, a solution of penzoylno(-oxide 51 dissolved in 100 P of ethyl alcohol) was added dropwise over a period of 3 hours, during which time the heat of polymerization was removed by reflux.

After the dropwise addition is completed, the mixture is kept for 1 hour to complete the polymerization. The obtained polymer was an alcohol solution with a solid content of 50%, and was used as it was in the scale inhibitor test. The average molecular weight of the obtained polymer was as follows.

Number average molecular weight: 5600 Weight average molecular weight: 13300 Example 5: 100 g of the aqueous solution obtained in Example 1 was 40% hydroxylated with 25 g of IJum aqueous solution, cooled and gradually neutralized without stirring. The pH of the resulting aqueous solution was 7.1.

In the example, 10 oz of the aqueous solution obtained in line side 2 was neutralized with 14.5 P of a 40% methylamine aqueous solution in the same manner as in Example 5, and the resulting aqueous solution had a PL of 6.0.

Example 7. - The pH of the aqueous solution obtained by neutralizing the □ aqueous solution 100Fi- obtained in Example 3 with 29% ammonia permanent solution 11.51 in the same manner as in Example 5 was 6.3.

The copolymers obtained in Examples 4 to 7 are all soluble in water, dimethylformamide, and dimethyl sulfoxide, and insoluble in acetone, dioxane, benzene, toluene, T-tyl acetate, chloroform, and tetrahydrofuran. be.

Moreover, the 13C-NMn spectra of the polymers obtained in Examples 4 to 7 are as shown in Table-2.

Table 2 (unit: ppm) Note: a, b, c, d, h, h2 are broad peaks f1g, which overlap in Examples 5 to 7 and become two-road.

There may be three hl and h2 due to differences in sequence and conformation.

The copolymers of Examples 1 to 7 were evaluated by the following method, and the results were as follows:
3 shows each inhibition rate along with comparative examples.

Aqueous sodium hydroxide solution (0,003 molar solution 25
0ml) and an aqueous magnesium chloride solution with and without each scale inhibitor (250mAl of a 0,002 molar solution)
were mixed and allowed to stand at 70C. After 1 hour, a part of the supernatant liquid was collected and filtered through a microfilter to obtain ethylenediaminetetraacetic acid disodium salt (El) TA-2N.
a), the magnesium concentration in the solution was measured, and the effect of each scale inhibitor on preventing magnesium hydroxide precipitation was investigated. The inhibition rate was determined using the following formula.

-B Scale suppression rate (@--xlo.

-B A... Concentration of magnesium dissolved in the solution before the test (ppm) B... Concentration of magnesium dissolved in the solution without scale inhibitor added after the test ( pp mouth 1) C...
... Concentration of magnesium dissolved in the solution of each scale inhibitor additive IJ after the test (1) pm) Table 3 Composition Comparative Example of Comparative Examples 1 to 3 - 1 Commercially available hydrolyzed polymaleic acid comparative example - 2 Sodium polyacrylate (molecular weight 1.850) Comparison, Example 3 Acrylic acid-methyl acrylate copolymer (
Number average molecular weight: 1720) Patent applicant: Nippon Kayaku Co., Ltd. Patent applicant: Koei Chemical Industry Co., Ltd.

Claims (1)

[Scope of Claims] A copolymer having the following structural units (1) and (2), wherein the molar ratio of the structural units (1) and (2) is from ]:9 to 9:1. 2 Maleic acid or fumaric acid and ethylene glycol monoallyl ether as a solvent! A method for producing a copolymer or a salt thereof, which comprises copolymerizing using -L, water or alcohol, and further treating with an alkaline substance if necessary.