HU205959B - Process for producing acrylamide polymeres containing hydroxame-groups - Google Patents

Abstract

In a process for the prepn. of a acrylamide polymer (A) contg. hydroxamic gps. by reacting aq. soln. of an acrylamide polymer (B) with a hydroxylamine salt (C) at a mole ratio of (C) to amide gps. in (B) of 0.1-2.0 an improvement comprises, conducting the reaction at pH = 8.0 or above at a temp. of 20-100 deg.C. The reaction remp. is 40-80 deg.C for 1-4 hrs. The pH is above 9.0 pref. above 11.0. (B) = acrylamide or polyacrylamide. -

Description

The present invention relates to a process for the preparation of hydroxamated acrylamide polymers.

The preparation of hydroxamated acrylamide polymers is known. Hydroxamated polymers are useful in the formation of iron complexes, chelating agents and their beneficial effects on known drilling muds. Hydroxamated polymers are also used as flocculating agents.

U.S. Patent No. 4,587,306 discloses the preparation of hydroxamated polyacrylamides by reaction of hydroxylamine with polyacrylamide in aqueous solution at 50-85 ° C and pH 6.2-6.8. According to the patent, this temperature is the optimum for minimizing the degradation of hydroxylamine and for achieving an appropriate reaction rate. With respect to the pH used, it is noted that this produces rapid kinetics of the reaction. The polymers used had a molecular weight of 1000-20000. Hydroxyoxamated polyacrylamides are also disclosed in U.S. Patent 3,353,444, which discloses that hydroxylamine is reacted with polyacrylonitrile and the resulting product is then acidically hydrolyzed. According to French Patent No. 2,476,113, hydroxyamine is reacted with polyacrylamide at 90 ° C using sodium acetate as a buffer. United Kingdom Patent Publication No. 2171127. and U.S. Patent Nos. 4,4800,667, 4,531,046, and 4,536,296.

Numerous studies have appeared in the literature on hydroxylamine with monomeric amides such as acetamide. on the kinetics of the reaction with formamide and acetanilide (W. P. Jencks and Mary, 35 Gilchrist, J. Am. Chem. Soc., 86, 5616 (1964); S. O. Eriksson and B. Arianderson, Acta Chem. Scand.

26, 2759 (1972); and G. B. Sergeev, V. A. Batyuk, and B.

M. Sergeev, Kinetics i Kataliz, 15, 326 [1974]). In each case, the optimum reaction pH was found to be between 6 and 740. According to Jencks and Gilchrist, a higher rate constant above pH 9 can be achieved. These kinetic studies were generally conducted under diluted conditions with a large excess of hydroxylamine and thus underwent pseudo-first order kinetics. Jencks and Gilchrist also found that the reaction could be catalyzed by buffers such as imidazole, pyridine, acetate or carbonate. F. Bergmann (Anal. Chem., 24, 1367 (1952)) used the reaction of hydroxylamine with amides at high pH as an analytical method for the determination of amides.

A. Meister et al. (J. Boil. Chem. 2/5, 441 (1955)), the maximum formation of hydroxamic acid with various natural amides is also at pH 6 55.

The foregoing articles deal primarily with the hydroxamation of monomers and refer primarily to pseudo-first order kinetics. When monomers are reacted with hydroxylamine salts, the reaction is carried out at very high hydroxylamine concentrations, and thus its kinetics are very different and cannot be considered to be the same as those of the polymer system with low hydroxylamine concentration. At high hydroxylamine concentrations, the reaction is always faster. When the concentration of hydroxylamine is reduced, the reaction rate is reduced proportionally and the conversion of hydroxylamine to the hydroxamate group is also reduced. Thus, the rate of reaction and the utilization of hydroxylamine used in hydroxylation of polymers, especially at low hydroxylamine concentrations of high molecular weight polymers, are critical to the industrial applicability of the process. Therefore, there is necessity _'Λ quality to develop a process in which the reaction rate and the utilization rate of hydroxylamine in the efficiency increases.

A novel process for the hydroxamation of acrylamide polymers has been developed in which the reaction rate and the efficiency of hydroxylamine utilization can be increased over those known in the art, especially those described in U.S. Patent 4,587,306. In the prior art, the optimum pH for the reactions in acrylamide polymers should be close to the pKa of the hydroxylamine, since if the pH is the same as the pKa, the concentration of the hydroxylamine is the same as that of the hydroxylamine salt, and this salt acts as a catalyst in the reaction.

It has been found that the reaction rate of polymers is unexpectedly increased by raising the pH and that the efficiency of the utilization of hydroxylamine is optimized. Thus, the hydroxylamine units used have a higher degree of hydroxamation by the new process we employ.

The invention thus relates to a process for the preparation of acrylamide polymers containing hydroxy groups by reacting an aqueous solution of an acrylamide polymer with a hydroxylamine salt using from 0.1 to 2.0 moles of hydroxylamine per mole of the amide groups in the acrylamide polymer. At pH 8.0 and 20-100 ° C.

Any water-soluble or water-dispersible acrylamide polymer can be used in the process of the invention. The use of acrylamide homopolymers such as polyacrylamide, polymethacrylamide is preferred, but also copolymers and terpolymers of acrylamide or methacrylamide with 90%, preferably 50%, of a copolymer or terpolymer containing an ethylene bond copolymerizable with acrylamide. Suitable comonomers include alkyl esters of acrylic acid, methacrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid and methacrylic acid, such as methyl acrylate, ethyl acrylate, butyl acrylate, ethyl methacrylate, methyl methacrylate, sodium acrylate, vinyl acetate, vinylpyrrolidone, styrene, acrylonitrile. The acrylamide polymers have a molecular weight of 1x10 ⁴ 3x10 ⁷ , preferably 1x10 ⁶ -3x10 ⁷ . Since these poly2

The higher the molecular weight of the polymer, the more dilute the solution is to be prepared.

Suitable hydroxylamine salts for use in the process include phosphates, perchlorates, sulfates, sulfites, hydrochlorides, acetates, propionates. Sulphates are preferred.

The molar ratio of hydroxylamine to polymer amide groups of the acrylamide is 0.1 to 2.0, preferably 0.5 to 1.5.

The reaction is carried out for a period of time ranging from 15 minutes to 30 hours, preferably from 1 to 8 hours. At lower reaction times, the degree of hydroxylation of the polymer is relatively lower, and at higher reaction times, there is no appreciable increase in the degree of hydroxamation.

The process according to the invention is carried out at a temperature between 20 ° C and 100 ° C, preferably between 40 ° C and 80 ° C. The efficiency of the reaction increases with respect to the degree of hydroxamation at low temperatures, but the reaction rate decreases. The preferred temperature is also optimum in terms of the hydroxamation achieved and the reaction rate.

As mentioned above, the pH is the most critical for the reaction. By pH is meant the naturally occurring pH that results from the neutralization of the hydroxylamine salt. The pH is at least 8.0, preferably greater than 9.0, and particularly preferably at least 11.0, and thus unexpected results can be achieved by the process of the invention. Below pH 10.0, the pH increases during the hydroxamation reaction. Thus, if the pH is 8.0 at the beginning of the reaction, it will rise well above 8.0 during the reaction. However, for optimal hydroxamination, the pH should be at least 8.0 throughout the reaction. This means that the initial pH should be at least 8.0. Due to the buffer effect of hydroxylamine, an initial pH of at least 8.0 can be achieved by the addition of a suitable base by which the acid salt is substantially completely neutralized. Suitable bases include, for example, sodium, potassium hydroxide and limestone.

Weaker bases such as ammonia or sodium acetic acid may be used, but higher amounts are required to achieve the desired pH, and stronger bases must be used along with these weak bases. Once the acid salt has been neutralized, the addition of an additional base results in an initial pH.

Ammonia in excess of the reaction can be removed, for example, by heating, vacuum or purging with inert gas.

The following examples illustrate the invention without limiting it. Parts and percentages by weight are by weight unless otherwise indicated.

Examples 1 and 2

A series of experiments was conducted to determine the effect of pH on the reaction of hydroxylamine with polyacrylamide. The polyacrylamide used was prepared by polymerizing acrylic amide in aqueous solution using ammonium persulfate and sodium metabisulfite as catalyst. The polymer has a molecular weight of 50,000 to 600,000. The reaction with hydroxylamine was 2.8 mol / liter polyacrylamide and

1.27 M hydroxylamine (added as hydroxylamine sulfate) was added at 80 ° C. The hydroxylamine sulfate is dissolved in water and treated with a suitable base under cooling, and the resulting solution is added with stirring to the polyacrylic amide solution at a suitable temperature. Equal portions are taken at specified intervals and analyzed to determine the hydroxamate and carboxylate content of the unreacted hydroxylamine and the polymer. The hydroxamate content is determined either by precipitation of the polymer in methanol and hydrolysis in concentrated acid followed by ion chromatography to determine the liberated hydroxylamine, or by ¹³ C-NMR spectra. The carboxylate content was determined from ¹³ C-NMR spectra. Unreacted hydroxylamine is measured by iodometric titration. Table 1 shows the fastest kinetics obtained at high pH (Examples 1 and 2). The degree of hydroxamation is also higher in these experiments. Examples C6 and C7 are described in U.S. Patent 4,587,306. In these, the reaction rate and final hydroxamate concentration are lower than in Examples 1 and 2. The table also shows the rate constant for the hydroxamation reaction at 80 ° C. Rapid growth at pH 8.5 and 10.8 is observed.

Table 1

Example number % Neutral. ¹ Base pH Hydroxamate content of polymer (%) beginner Final 0.5 Hr. 1 Mr. 2HR. 3 Mr. 4Hr. 5HR. 6HR. 7 Mr. Kx10 ⁴ cl 0 - 3.4 4.2 0.8 14 1.8 3.0 3.7 4.1 4.9 1.17 C2 25 NaOH 5.0 6.0 1.2 1.3 2.8 4.1 4.4 6.4 7.8 10.6 2.18 C3 50 NaOH 5.8 7.2 1.3 2.5 4.1 6.7 8.5 11.9 14.1 - 3.82 C4 75 NaOH 6.1 9.0 1.5 1.7 3.6 7.3 8.5 10.9 12.1 12.1 3.50 C5 90 NaOH 6.9 10.0 1.1 1.9 3.6 6.7 11.1 14.0 12.5 14.5 3.95 1 100 NaOH 8.5 10.2 4.2 8.7 17.1 20.5 21.9 21.8 21.7 21.5 11.9

HU 205 959 Β

Example number % Neutral. ¹ Base pH Contains Polymer Carbon Oxamate (%) beginning Final 0.5 Hr. 1 Mr. 2 Mr. 3 Mr. 4 Mr. 5HR. 6HR. 7 Mr. Kx10 ' ⁴ 2 108 NaOH 10.8 10.5 16.7 23.3 27.2 26.0 - 26.7 - 25.2 31.1 C6 50 Sodium acetate 5.0 5.2 1.1 2.4 3.9 '5.5 7.5 9.9 12.3 14.6 3.49 C7 100 Sodium acetate 5.5 '5.7 2.9 3.8 6.7 9.7 14.1 15.7 18.6 19.6 5.58

¹ 1 Neutralization of hydroxylamine sulfate

3-6. example

The polyacrylamide of Example 1 was reacted with 0.63 mol of hydroxylamine (as hydroxylamine sulfate) at 80 ° C at a concentration of 1.41 mol (10% by weight). Add sufficient sodium hydroxide to neutralize the sulfuric acid in the hydroxylamine sulfate, followed by sodium hydroxide in Table 2, and test the kinetics. Even the lowest pH (or base concentration) is high enough, however, as the concentration of sodium hydroxide increases, the rate increases rapidly.

Table 2

Example number Base Concentration: ^1M NaOH Hydroxamate content (%) pH 0.5 Hr. 1 Mr. 2 Mr. 3 Mr. 4 Mr. 5HR. 6 Mr. 7 Mr. 3 0.07 12.8 7.1 10.4 15.1 15.8 16.5 16.9 17.0 17.2 4 0.19 13.0 13.0 15.7 17.6 17.9 17.9 17.6 17.5 - 5 0.38 13.6 21.0 22.1 21.9 20.8 20.4 20.0 19.4 19.2 6 0.63 13.8 21.3 21.7 19.7 18.7 17.7 17.2 16.7 -

Base concentration after neutralization of hydroxylamine sulphate

7-11. Example 35

The polyacrylamide of Examples 1 and 2 is reacted as described in Examples 3-6. except that the polymer had a concentration of 0.70 mole (5 wt%) and a hydroxylamine concentration of 0.32 mole. The results are shown in Table 3. 40

In this case, the final hydroxamate level is dependent on the base concentration and increases with the sodium hydroxide concentration. The hydroxamate level is generally lower than the levels of 3-6. example where the polymer concentration was higher.

Table 3

Example number Base Concentration ^1M NaOH Hydroxamate content (%) pH 0.5 Hr. 1 Mr. 2 Mr. 3 Mr. 4Hr. 5 Mr. 6 Mr. 7 Mr. 7 0.02 12.3 3.0 4.7 6.6 7.3 8.0 8.5 8.9 8.9 8 0.1 13.0 7.5 9.5 10.7 11.2 H 1 10.8 10.9 10.9 9 0.2 13.3 11.6 12.4 12.4 12.1 12.0 11.5 11.2 11.0 10 0.33 13.5 15.8 16.1 15.0 14.6 14.0 13.5 13.5 13.5 11 0.65 13.8 17.9 18.7 18.1 16.5 15.8 15.9 15.2 -

Base concentration after neutralization of hydroxylamine sulphate

12-15. example

The results shown in Table 4 were obtained by using the polyacrylamide of Examples 1 and 2 as a

3-6. The polymer was reacted as described in Example 1, except that the polymer concentration was 0.28 mole (2 wt%) and the hydroxylamine concentration was 0.13 mole.

HU 205 959 Β

Table 4

Example number Base Concentration ¹ NaOH molar Hydroxamate content (%) PH 0.25 Hr. 0.5 Hr. 1 Mr. 2 Mr. 4Hr. 6HR. 12 0.13 13.1 3.8 4.4 4.8 4.9 4.7 4.4 13 0.25 13.4 6.4 6.8 7.9 7.3 7.2 7.1 14 0.51 13.7 8.6 8.8 9.2 9.2 8.7 8.6 15 1.01 14.0 9.4 9.0 8.9 8.6 8.4 8.3

Base concentration after neutralization of hydroxylamine sulphate

16-19. example

12-15. The reaction mixture was worked up as described in Example 2, 2% and the reaction was continued at 60 ° C to lower the concentration of polyacrylamide. The results are shown in Table 5.

Table 5

Example number Base Concentration ¹ NaOH molar Hydroxamate content (%) PH 0.25 Hr. 0.5 Hr. 1 Mr. 2 Mr. 4Hr. 6HR. 16 0.13 13.1 2.0 2.9 4.9 7.0 8.6 8.4 17 0.25 13.4 3.6 5.0 7.5 10.3 12.0 12.2 18 0.51 13.7 4.8 7.4 9.6 10.9 11.3 11.3 19 1.01 14.0 7.4 9.0 10.1 10.5 10.8 10.6

Base concentration after neutralization of hydroxylamine sulphate

20-23. example

A12-15. Example 35 was repeated except that the reaction was carried out at 40 ° C. The results are shown in Table 6. Both the reaction rate and the final hydroxamation concentration are increased when the amount of sodium hydroxide is increased from 2.0 mol to 4.0 mol. Thus, even at 40 ° C, a sufficiently rapid hydroxamation rate can be achieved at a sufficiently high pH.

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Table 6

Example number Base Concentration ¹ NaOH molar Hydroxamate content (%) pH 0.25 Hr. 0.5 Hr. 1 Mr. 2 Mr. 4Hr. 6HR. 20 0.5 13.7 3.1 4.0 5.4 8.3 11.6 13.1 21 1.0 14.0 4.3 5.1 7.6 11.0 13.2 14.3 22 2.0 14.3 8.0 8.9 11.0 12.9 14.1 14.4 23 4.0 14.6 14.7 16.1 17.6 19.2 20.6 20.5

Base concentration after neutralization of hydroxylamine sulphate

24-30. example

Examples 1 and 2 work with the advantage of using polyacrylamide with a molecular weight of about 15 million and different concentrations of polymer / hydroxylamine at different pHs, temperatures and reaction times. The results are shown in Table 7. 24-26. In Example 1, the increase in pH increases the incorporation of hydroxamate at the same ratio of polymer to hydroxylamine. If the 27-30. Examples 5 to 10 are compared with the data in Table 5, the polymer having a much lower molecular weight gives almost the same hydroxamation response under nearly the same conditions.

HU 205 959 B

Table 7

E.g. Konccniráció Hydroxamate a in polymer (%) Pam NHjOH C Hrs. Ph 24C 0.38 mol 0.38 mol 75 18 6.2 7 25 0.28 mol 0.28 mol 80 3 9.5 16 26 0.28 mol 0.28 mol 80 4 11.0 23 27 0.28 0.14 60 0.5 12.0 7 28 0.28 0.14 60 1 12.0 10 29 0.28 0.14 60 2 12.0 13 30 0.28 0.14 60 4 12.0 13

C - comparator

Example 31

The same procedure as in Examples 1 and 2 was followed except that the hydroxylamine hydrochloride salt was used. Similar results are obtained.

Example 32

The procedure described in Examples 1 and 2 was followed except that a copolymer of acrylamide and acrylic acid (90:10) (molecular weight: 72,000) was used. Similar results are obtained.

Example 33

The procedure described in Example 32 was followed except that the following polymers were used instead of the copolymer used therein:

Example 33 - acrylamide / sodium acrylate (60:40), molecular weight: 120000.

Example 34 - polymethacrylamide, molecular weight: 2 million.

Example 35 - acrylamide / acrylonitrile (70:30), molecular weight: 8000.

Example 36 - acrylamide / ethyl acrylate (80:20), molecular weight: 8 million.

Example 37 - acrylamide / acrylic acid / styrene (80:10:10), molecular weight: 800,000.

In each example, the same results were obtained.

38-40. example

The hydroxylamine of Example 31 was replaced with O-methylhydroxylamine (Example 38), N-ethylhydroxylamine (Example 39), and O-phenylhydroxylamine (Example 40), so that each In this case, a similar degree of hydroxamation of the polymer is obtained.

Claims (6)

PATENT CLAIMS A process for the preparation of an acrylamide polymer containing hydroxam groups in an aqueous solution of an acrylamide polymer By reaction with 30 hydroxylamine salts, wherein the molar ratio of hydroxylamine to moles of amide groups in the acrylamide polymer is from 0.1 to 2.0, characterized in that the reaction is carried out at a pH of at least 8.0 and 20-100 ° C is carried out. Process according to claim 1, characterized in that the reaction is carried out at 40-80 ° C. The process according to claim 1, wherein the reaction is carried out at a pH above 9.0. The process according to claim 1, wherein the reaction is carried out at a pH of at least 11.0. The process according to claim 1, wherein the reaction is carried out for 1 to 4 hours. The process according to claim 1, wherein the reaction is carried out at a temperature of from 40 ° C to 80 ° C at a pH of at least 11.0.