WO1997016464A1 - Use of polycarboxylic acid semi-amides as scale inhibitors - Google Patents

Abstract

Disclosed is the use as scale inhibitors of polycarboxylic acid semi-amides obtainable by the reaction of (a) polymers containing anhydride groups and with a mean molar mass Mw of 200 to 100,000 and (b) sarcosine, aminosulphonic acids, aminophosphonic acids or their alkali metal salts.

Description

Use of polycarboxylic acid half-baitides as scale inhibitors

description

The invention relates to the use of polycarboxylic acid half-aitiides, which are obtainable by reacting polymers containing anhydride groups and compounds containing amino groups, as scale inhibitors.

In order to reduce or prevent the deposition of poorly soluble alkaline earth metal salts from aqueous systems, scale inhibitors are used in industry. They are used in various technical fields, e.g. in boilers for steam generation, for the desalination of sea water by distillation, for the evaporation of sugar juice, for reverse osmosis and for oil and gas extraction or transportation. In the latter application, for example, inorganic salts which are difficult to dissolve, such as e.g. Calcium carbonate, calcium sulfate, barium sulfate and strontium sulfate and form disturbing deposits inside the conveyor, which can even lead to production stoppages. The formation of such deposits is based on changes in the solubility parameters such as temperature and pressure during production or e.g. also mixing of formation water containing alkaline earth metal ions with sea water rich in sulfate ions in the formation or within the conveying devices. Deposits within the formation impair the permeability of the deposit and thus reduce the productivity of oil and gas.

The scale inhibitors used are, for example, polyacrylic acid, polymaleic acid or hydrolyzed water-soluble copolymers of maleic anhydride and, for example, C ₂ -C ₁ -efins. For oil and gas production, for example, the scale inhibitor dissolved in water can be injected into a press-in or production well or directly into the line. Polycarboxylates or oligo- / polyphosphates are usually used here. If the scale deposits occur in the deposit in the inflow area of the probe, these can only be prevented by a squeeze treatment with a suitable scale inhibitor. In the case of a squeeze treatment, the dissolved scale inhibitor is introduced directly into the formation in excess, practically as a supply, in order to be deposited on the formation rock. The inhibitor continuously separates from the formation rock during production. The content of scale inhibitor in the water, which comes from the deposit together with oil, for example, is checked at certain intervals. Only with a sub If a critical concentration of scale inhibitor is exceeded, a new squeeze treatment is carried out.

From US-A-4 018 702 the use of reaction products of polymaleic anhydride and compounds containing amino groups is known. Suitable reaction products are, for example, the adducts of iminodiacetate with polymaleic anhydride, and the addition products of diethanolamine or ethanolamine with polymaleic anhydride. The effectiveness of such products in scale inhibition, however, is in need of improvement.

The preparation of polymaleic anhydride by radical polymerization of maleic anhydride in inert solvents is known, cf. GB-A-1 024 725, GB-A-1 411 063 and US-A-3 810 834. According to the process known from US-A-4 818 795, maleic anhydride is converted into aromatic hydrocarbons at temperatures of 60 up to 200 ° C. in the presence of 1 to 20% by weight, based on maleic anhydride, of peroxyesters. Polymaleic anhydrides with a low residual monomer content are obtained.

Processes for the preparation of copolymers containing maleic anhydride units are known from EP-A-0 264 627 and EP-B-0 276 464. The copolymerization takes place in the presence of peroxyesters as a catalyst in aromatic hydrocarbons, for example toluene, xylene, ethylbenzene and isopropylbenzene. Examples of comonomers which can be used are vinyl esters of saturated Ci to C ₄ carboxylic acids, ethylenically unsaturated C ₃ to C ₅ carboxylic acids and compounds containing at least two monoethylenically unsaturated double bonds. The maleic anhydride units contain polymers which are prepared by radical polymerization in aromatic solvents and contain considerable amounts of solvents in bound form.

EP-B-0 009 171 discloses the preparation of polymaleic anhydride by polymerizing maleic anhydride in acetic anhydride with hydrogen peroxide as a catalyst.

The object of the present invention is to provide scale inhibitors which are more effective than those previously described. The new scale inhibitors should also be biodegradable if possible.

The object is achieved according to the invention with the use of polycarboxylic acid halamides, which are obtained by reacting (a) Anhydride group-containing polymers having an average molecular weight M _w of 200 to 100,000 and

(b) Sarcosine, aminosulfonic acids, aminophosphonic acids or their alkali metal salts

are available as scale inhibitors.

Polymers containing anhydride groups and having an average molecular weight M _{w of} from 200 to 100,000 are polymers of maleic anhydride, most of which are known from the prior art given above. They are particularly advantageous by polymerizing maleic acid anhydride. optionally in the presence of comonomers, in inert solvents in the presence of peroxyesters. Such processes are described for example in US-A-4 818 795, EP-A-0 264 627 and EP-B-0 276 464. The polymerization is usually carried out at from 60 to 200 ° C. in the presence of from 1 to 20% by weight, based on the monomers, of a peroxy ester. The polymerization can be carried out, for example, in benzene, toluene, xylene, ethylbenzene, diethylbenzene, isopropylbenzene, diisopropylbenzene, tetraalkylbenzenes, naphthalene, methyl indole, dodecylbenzene and mixtures of the aromatic solvents mentioned. Radical polymerization of maleic anhydride is the preferred solvent

Toluene, xylene, ethylbenzene, isopropylbenzene or mixtures thereof. Both the homopolymers of maleic anhydride and the copolymers with other monomers can be used as component (a).

Suitable comonomers for carboxylic anhydrides, for example, C ₂ - to Cι ₂ -01efine, preferably C ₂ - to Cβ and particularly preferably C ₂ - to C ₄ -α-olefins into consideration, for example ethylene, propylene, butene-1, isobutene, and Diisobutene. These copolymers are mainly alternating polymers, ie they contain, for example, maleic anhydride and the comonomer in a molar ratio of 1: 1. Also suitable as comonomers are styrene, Ci to C ₄ alkyl vinyl ether, vinyl esters of saturated Ci to C ₄ monocarboxylic acids, acrylic acid, methacrylic acid or mixtures of the comonomers mentioned. Of the alkyl vinyl ethers, preference is given to methyl vinyl ether and ethyl vinyl ether. Preferred vinyl esters are vinyl acetate and vinyl formate. Copolymers of isobutene and maleic anhydride are preferably used as component (a). Such copolymers have, for example, an average molecular weight Mw of 200 to 100,000. Also of interest are copolymers of maleic anhydride with 0.1 to 10% by weight, based on maleic anhydride, of at least one crosslinking agent containing two ethylenically unsaturated double bonds. Such crosslinkers are, for example, glycol diacrylates and glycol dimethacrylates such as butanediol diacrylate or the diacrylates and dimethacrylates of polyalkylene glycols, for example of polyethylene glycol with molar masses from 100 to 10,000. Other suitable crosslinkers are, for example, butanediol divinyl ether, pentaerythritol triallyaccharide and pentiallylsaccharose, triallyl. If they are present during the polymerization, the crosslinking agents are preferably used in an amount of 0.2 to 5% by weight, based on maleic anhydride.

The compounds preferably used as component (a) include polymaleic anhydrides which are obtainable by free-radical polymerization of maleic anhydride, if appropriate in the presence of comonomers copolymerizable therewith in toluene, xylene, ethylbenzene or mixtures thereof, and one of which is a medium ler molecular weight M _w from 300 to 3,000. Preferred copolymerizable comonomers are isobutene, diisobutene, ethylene and acrylic acid. If the polymerization of the maleic anhydride is carried out in an aromatic solvent, for example up to 50, preferably up to 40% by weight of the polymer can consist of chemically bound solvent in which the polymers have been prepared.

In the case of copolymers of maleic anhydride, the content of comonomers in the copolymer is, for example, 10 to 90, preferably 30 to 70 mol%.

The above-described polymers containing anhydride groups are reacted with sarcosine (N-methylglycine), aminosulfonic acids, aminophosphonic acids or their alkali metal salts. Aminosulfonic acids are understood to mean, for example, amino-Ci to Cζ-alkyl sulfonic acids, N-substituted aminoalkyl sulfonic acids and amino aryl sulfonic acids such as sulfanilic acid. From this group, preference is given to using taurine and N-alkyltaurines, the alkyl groups of which have 1 to 18 C atoms, e.g. N-methyl taurine. Suitable compounds (b) are also aminophosphonic acids such as propylaminomethylenephosphonic acid or aminotrimethylenephosphonic acid. The implementation products of

(a) polymaleic anhydrides which are obtained by radical polymerization of maleic anhydride, optionally in the presence of comonomers copolymerizable therewith in toluene, xylene, b

Ethylbenzene or mixtures thereof are available and which have an average molecular weight M _w of 300 to 3000 and

(b) sarcosine, taurine, methyl taurine or their alkali metal salts.

In the reaction of the polymers of group (a) containing anhydride groups with the compounds of group (b), when the reaction is complete, a carboxylic acid halamide group is formed from an anhydride group. However, the reaction can also be carried out only partially, so that only a small part of the anhydride groups present in the copolymer is converted into half-amide groups, e.g. 70%. The remaining part of the anhydride groups of the polymer is then converted into dicarboxylic acid groups during the reaction. In the reaction of the compounds (a) and (b), for example, those containing anhydride groups are used

Polymers (a) in such a ratio with at least one compound from group (b) that per mole of anhydride groups in the polymer (a) 0.1 to 2, preferably 0.2 to 1 mole of the compounds (b) containing amino groups be used.

The reaction is preferably carried out in an aqueous medium. Advantageously, an aqueous solution of an alkali metal salt, preferably a sodium or potassium salt, of at least one compound (b) is initially introduced and the polymeric compound (a) containing anhydride groups is added all at once, continuously or batchwise. The reaction is carried out, for example, in the temperature range from 30 to 100, preferably 50 to 80 ° C. The pH of the reaction solution is, for example, 6 to 12. The reaction of compounds (a) and (b) takes from about 30 minutes to 5 hours, with higher reaction temperatures leading to shorter residence times. The reaction can also be carried out at temperatures above 100 ° C., provided that the reaction is carried out under pressure in specially equipped apparatus. The sodium salt of sarcosine and / or taurine is usually initially introduced as a 40 to 50% strength aqueous solution, the aqueous solution is heated to a temperature of 70 to 80 ° C. and the polymers containing anhydride groups are added in portions. However, the reaction can also be carried out in tertiary amines such as tri-propylamine or pyridine as solvents. After the reaction has ended, the amine is distilled off and the reaction product is isolated in the form of the sodium salt. The resulting Polycarbonsaurehalbami.de can be characterized using IR spectra and using the KOH titer. The polycarboxylic acid halamides have, for example, molecular weights of 400 to 4500, preferably 500 to 2500. The polycarboxylic acid halamides described above are used as scale inhibitors. They prevent the formation of crystals of hardness-forming salts, such as calcium carbonate, magnesium hydroxide, magnesium carbonate, calcium, barium or strontium sulfate, calcium phosphate (apatite) in water-carrying systems, or they influence the formation of precipitates of such salts in such a way that no hard or rock-hard deposits are formed, but separations which are easily washed out in water are formed. In this way, the surfaces of, for example, heat exchangers, pipes or pump components are kept free of deposits. In addition, this is βie Cor ^ι -oo-i.onp- tilt, especially the risk of pitting corrosion, which often develops among rock hard coverings, crucial ver¬ Ringert. The use of scale inhibitors can increase the lifespan of systems. Downtimes for cleaning system parts can be significantly reduced by using scale inhibitors.

The scale inhibitors are usually used in substoichiometric amounts, e.g. in amounts of 0.1 to 100, preferably 0.5 to 25 ppm, based on the respective amount of water. The water-carrying systems are e.g. around open or closed cooling circuits, for example of power plants or chemical plants, such as reactors, distillation apparatuses and similar components, in which heat has to be dissipated. Scale inhibitors can also be used in boiler water and steam generators, preferably in the range of water temperatures below 150 ° C. A preferred application of the scale inhibitors to be used according to the invention is the desalination of sea and brackish water by distillation or membrane processes, such as, for example, reverse osmosis or electrodialysis. Another application of the deposit inhibitor is e.g. given the evaporation of sugar juices from cane or beet sugar. Another important application is the use of polycarboxylic acid halamides as scale inhibitors in the oil and gas extraction and transportation described above.

Examples

Preparation of the polycarboxylic acid half-amides to be used according to the invention

Adduct 1:

278 parts of a 40% aqueous solution of the sodium salt of sarcosine are heated to a temperature of 70 ° C. and mixed at this temperature with 173 parts of oligomaleic anhydride with an average molecular weight M _w of 600, heated to 80 ° C. and for 1 hour stirred at 80 ° C. A homogeneous emulsion is obtained which is diluted to a solids content of 50% by adding water. The acid number of the adduct is 1.455 meq KOH / g.

5 The oligomaleic anhydride was according to Example 1 of

US-A-4 818 795 made by polymerizing maleic anhydride in xylene. 0.7 mol of sarcosine Na salt was used per mole of anhydride groups in the polymer.

10 adduct 2:

89 parts of an alternating copolymer of isobutene and maleic anhydride with an average molecular weight M _w of 4000 are added to an aqueous sodium sarcosinate solution. that by mixing 58 parts sarcosine, 52 parts 50% aqueous

15 sodium hydroxide solution and 35 parts of water were obtained. The reaction mixture is stirred for 3 hours at a temperature of 80 ° C., so much water is then added that a 50% aqueous solution is formed. 1 mole of sodium sarcosinate was used per mole of anhydride groups in the copolymer.

20th

Adduct 3:

48 parts of the copolymer of isobutene and maleic anhydride described under adduct 2 are as described under adduct 2 with 22 parts sarcosine, 20 parts 50% aqueous

25 sodium hydroxide solution and 27 parts of water reacted. The molar ratio of anhydride groups in the copolymer to sodium sarcosinate was 1: 0.7. A 50% aqueous solution is prepared by adding water. A total of 150 parts are obtained.

30 adduct 4:

The procedure is as described for the preparation of adduct 2, but 58 parts of the copolymer of isobutene and maleic anhydride given there, 11.2 parts sarcosine, 13.6 parts water, 10 parts 50% aqueous sodium hydroxide solution are used. By adding

35 27 parts of water, the reaction mixture is adjusted to a solids content of 50%. The molar ratio of anhydride units in the copolymer to sodium sarcosinate was 1: 0.3.

Adduct 5:

40 48 parts of the copolymer described under adduct 2

Isobutene and maleic anhydride are added to a solution heated to 70 ° C. to 51.5 parts of a 50% strength aqueous solution of taurine sodium salt and stirred at 80 ° C. for 3 hours. By adding water, a solids concentration of 50% is

45 posed. The molar ratio of anhydride groups in the copolymer to taurine sodium salt is 1: 0.5. Adduct 6:

The procedure is as in the preparation of adduct 5, but using 44 parts of the alternating copolymer of isobutene and maleic anhydride, 66 parts of 50% aqueous taurine-sodium salt solution and 44 parts of water. You get 154 parts of one

50% aqueous solution of the adduct, in which the molar ratio of anhydride groups to taurine is 1: 0.7.

Adduct 7: The procedure is as described for the preparation of adduct 5, but using 34.3 parts of the alternating copolymer of isobutene and maleic anhydride and 73.5 parts of 50% aqueous tanrin-sodium salt solution. This gives 342 parts of a SO% icren aqueous solution of the adduct, in which the molar ratio of the anhydride groups to taurine is 1: 1.

Adduct 8:

The procedure is as described for the preparation of adduct 5, but 64.5 parts of the alternating copolymer of isobutene and maleic anhydride and 52.8 parts of a 43% strength aqueous N-methyl taurine sodium salt solution are used. 174 parts of a 50% strength aqueous solution of the adduct are obtained, in which the molar ratio of the anhydride groups to N-methyl taurine is 1: 0.33.

In order to test the performance properties of the polycarboxylic acid halamides to be used according to the invention as scale inhibitors, the behavior of the adducts described above during seawater desalination is assessed. The following test methods were used for this:

In this test, adducts 1-7 are investigated as inhibitors in the formation of calcium and magnesium hydroxides and carbonates from synthetic seawater solutions. In seawater desalination, calcium carbonate and magnesium hydroxide in particular form firmly adhering and disruptive deposits on the heat exchanger surfaces. The formation of calcium sulfate is also a serious problem. The test solution consists of an aqueous saline solution

70 ° d Mg ²⁺ 14 ° d Ca ²⁺ 70 ° d C0 ₃ ² '

contains. The synthetic sea water solution is then ppm with 25 of staggered and in Examples 1 to 7 used adducts 1-7 pumped for 3 ^hours' in a dynamic circulation apparatus in a circle. After a test period of 3 hours, samples are taken which are titrimetrically analyzed for the water hardness content. Due to the decrease in water hardness in the course of the experiment, one can count back to the deposits which form in the heat exchanger. The lower the degree of hardness in the water sample taken, the more coating has deposited on the heat exchanger tubes. The water hardness values determined are listed in Table 1. A high degree of hardness after a test time of 3 hours suggests good scale inhibition (deposit prevention).

The test results of the adducts 1 to 7 to be used according to the invention in comparison to a market product are given in Table 1. The market product is a polymaleic acid with a molecular weight of 1000.

Table 1

Test conditions: Temperature from the test water outlet: 112 ° C

Pressure: 4 bar running time: 3 hours

Eine weitere Scale-Inhibierungsprüfung wurde nach dem folgenden Test durchgeführt:

Another scale inhibition test was performed after the following test:

50 ml of synthetic sea water and 5 or 10 ppm inhibitor are placed in a 100 ml screw-top glass jar, followed by a short mixing. 50 ml of synthetic formation water are added and mixed again. The sealed jars are heated overnight at 80 ° C in an oven (about 15 hrs.) Un _d the extent of the deposit the next day qualitatively assessed shares.

Compositions of synthetic waters:

Synthetic sea water (weight g / 1):

1.6 g CaCl ₂ x2 H ₂ 0

11.8 g MgCl ₂ x 6 H ₂ 0

0.02 g SrCl ₂ x6 H ₂ 0

0.8 g KC1

4, 14 g Na ₂ S0 ₄

0.2 g NaHCO ₃

24.8 g NaCl

Synthetic formation water (weight g / 1)

0.24 g BaCl ₂ x2 H ₂ 0

6.06 g SrCl ₂ x 6 H ₂ 0

89.4 g NaCl

52.94 g CaCl ₂ x ₂ H ₂ 0

15.06 g MgCl ₂ x6 H ₂ 0

Without an inhibitor, large, large mineral deposits of, for example, CaC0 ₃ , CaS0 ₄ , SrS0 ₄ or BaS0 _{4 can be found} on the bottom and on the wall of the glass vessel (blind test). When using the inhibitors described, the observed deposits are only present selectively or not at all. The individual assessments can be found in the table. In some cases, doses lower than 5 ppm are sufficient for effective scale inhibition.

The assessments used in the table have the following meaning:

The evaluation scale ranges from "+++" to "-", where +++ stands for very good, i.e. no deposits and

--- very poorly symbolized, i.e. extremely heavy deposits can be seen.

Claims

claims 1. Use of polycarboxylic acid halamides by the reaction of (a) Anhydride group-containing polymers having an average molecular weight M _w of 200 to 100,000 and (b) Sarcosine, aminosulfonic acids, aminophosphonic acids or their alkali metal salts are available as scale inhibitors. 2. Use according to claim 1, characterized in that the Polymers (a) containing anhydride groups are obtainable by free-radical polymerization of maleic anhydride and, if appropriate, monomers copolymerizable therewith in an aromatic solvent. 3. Use according to claim 1, characterized in that the polymers containing anhydride groups are obtainable by radical polymerization of maleic anhydride in toluene, xylene, ethylbenzene, isopropylbenzene or mixtures thereof. 4. Use according to claim 1, characterized in that the anhydride group-containing polymers (a) by radical polymerization of maleic anhydride with C ₂ - to Cι ₂ -01efinen, styrene, Ci to C ₄ alkyl vinyl ethers, vinyl esters of saturated Ci to C ₄ monocarboxylic acids, acrylic acid, methacrylic acid or mixtures of the comonomers are available. 5. Use according to claim 1, characterized in that the reaction products of (a) Polymaleic anhydrides, which are radical-free Polymerization of maleic anhydride, if appropriate in the presence of comonomers copolymerizable therewith, in Toluene, xylene, ethylbenzene or mixtures thereof are available and have an average molar mass M "of 300 to 3000, and (b) sarcosine, taurine and / or methyl taurine or their alkali metal salts starts. 6. Use according to one of claims 1 to 5, characterized gekenn¬ characterized in that the anhydride groups containing Polymeri¬ sate (a) in such a ratio with at least one compound of group (b) that per mole of anhydride groups in the polymer (a) 0.1 to 2 moles of the amino group-containing compounds (b) are used. Use of polycarboxylic acid halamides as scale inhibitors Summary Use of polycarboxylic acid halamides, which are obtained by reacting (a) Anhydride group-containing polymers having an average molecular weight M _w of 200 to 100,000 and (b) Sarcosine, aminosulfonic acids, aminophosphonic acids or their alkali metal salts are available as scale inhibitors.