DK146185B - PROCEDURE FOR PREVENTING CALCIUM AND MAGNESIUM SALT DISPOSALS AND CORROSION PROTECTION IN A WATER SYSTEM - Google Patents

Description

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il (12) PUBLICATION MANUAL (n) 146185 B

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DIRECTORATE OF THE PATENT AND TRADEMARKET SYSTEM

(21) Patent Application No: 0754/74 (51) Int.CI.3: C 23 F 11/12 (22) Filing Date: 13 Feb 1974 C23F 14/02 C 02 F 5/08 (41) Aim. available: 15 Aug 1974 (44) Submitted: 18 Jul 1983 (86) International Application No: - (30) Priority: 14 »eb1973GB7181 / 73 (71) Applicant: 'CIBA-GEIGY (UK) LIMITED; London SW1E 6LH, GB.

(72) Inventor: Thomas Ivor Mones; GB, Geoffrey 'Graham; GB, Michael Anthony ‘Finan; GB.

(74) Plenipotentiary: Dansk Patent Kontor ApS

(54) Procedure for preventing calcium and magnesium salt deposits and corrosion protection in a water system

The present invention relates to a method of treating water to prevent the formation of calcium and magnesium salt deposits on the surface of pipes, boilers, vaporizers, vapor ejectors and the like, as well as to protect metal surfaces from corrosion at ambient temperatures.

Various proposals have been made for the use of polymaleic anhydride and its copolymers for water treatment processes. Eg. U.S. Patent No. 3,617,577 discloses the use of copolymers of maleic anhydride and ethylene with molecular weights of from about 1000 to 5000} and states that with lower molecular weight polymers no significant inhibition of scale deposition is achieved at the threshold concentration. - r 3 2 146185 trations.

U.S. Patent No. 2,723 * 956 discloses the use of copolymers of maleic anhydride and another monoethylenic compound in a molar ratio of 1: 2 to 2: 1 to reduce and prevent scaling, but the molecular weights are not disclosed. English Patent No. 772,775 discloses a process for treating hard water with water-soluble copolymers of maleic anhydride and other molecular weight monomers of 1000 to 40,000.

Surprisingly, it has been found that water-soluble, hydrolyzed copolymers of maleic anhydride and a monoethylenically unsaturated monomer or mixture of monomers, having an average molecular weight of less than 1000, determined by vapor phase osmometry using methyl ethyl ketone as solvent, and a molar ratio of maleic anhydride to mono-olefinic compound of from 2.5: 1 to 100: 1 exerts a threshold electrical activity against calcium carbonate and in some cases also against calcium sulfate.

The present invention relates to a process of the kind set forth in the preamble of claim 1, and this process is characterized in that the molar ratio of maleic anhydride to the other monomers is from 2.5: 1 to 100: 1 and the molecular weight of the copolymer is in the The mole ratio is preferably from 2.5: 1 to 36: 1 ° S most preferably from 2.5: 1 to 7; 1. The copolymer can also be used with other water treating agents well known in the art. Dispersant and / or threshold agents may be used, such as polyacrylic acid and its salts, hydrolyzed polyacrylonitrile, polymethacrylic acid and its salts, polyacrylamide and copolymers thereof from acrylic and methacrylic acids, lignin sulfonic acid and its salts, tannin, naphthalenesulfonic acid / formaldehyde acid, derivatives thereof and cellulose derivatives, e.g. carboxymethylcellulose. Specific threshold agents such as polymaleic acid and its salts, alkylphosphonic acids, 1-aminoalkyl-1, 1-diphosphonic acids and their salts and alkali metal phosphates may also be used.

The copolymers may also be used in combination with precipitating agents such as alkali metal orthophosphates, carbonates and hydroxides, oxygen scavengers such as alkali metal sulfites and hydrazine, and sequestering agents such as nitrilotriacetic acid and its salts and ethylenediaminetetraacetic acid. They can also be used in conjunction with corrosion inhibitors such as cyclohexylamine, morpholine, distearylamine / ethylene oxide condensation products, stearylamine, sodium sulfate, magnesium sulfate, and also in combination with anti-foaming agents such as di-stearylsebacamide, distearyladipamide, and related products, such as caprylic alcohols and their ethylene oxide condensates.

The ethylenically unsaturated monomers can be selected from a wide range of substances, e.g. acrylic acid, methacrylic acid, crotonic acid, itaconic acid, aconitic acid (and their esters), ethyl acrylate, methyl methacrylate, acrylonitrile, acrylamide, vinyl acetate, styrene, α-methyl styrene, methyl vinyl ketone, acrolein, ethylene, propylene or mixtures thereof.

If mixtures of monomers are used, the resulting polymer may e.g. be a terpolymer derived from maleic anhydride and two other monomers. Such terpolymers are e.g. those derived from maleic anhydride, vinyl acetate and ethyl acrylate. Other suitable combinations may also be used, as shown in the table below.

Particularly preferred copolymers are those derived from hydrolyzed copolymers of maleic anhydride and acrylic acid, its amide and its esters, methacrylic acid, its amide and its esters and vinyl esters.

The copolymers can be prepared in various ways. A convenient way is by polymerization in a solvent, especially a reactive solvent, using an initiator which forms free radicals such as benzoyl peroxide, di-tert-butyl peroxide or monobutyl hydroperoxide. In some cases, the polymer precipitates from the solution, but if e.g. methyl ethyl ketone is used as a solvent, it can remain in solution. It can then e.g. is isolated by distillation of methyl ethyl ketone and precipitation of the anhydride resin in a non-polar solvent such as toluene.

Examples of reactive solvents which may be used are xylene, toluene, ethylbenzene, tert-butylbenzene, acetone, methyl ethyl ketone, carbon tetrachloride, acetic acid, acetonitrile. Especially preferred are xylene and toluene.

When a reactive solvent is used, it acts as end stopper, especially for short chain copolymers, and forms a minor part of the polymer molecule. Such end-stopped copolymers may also be referred to as cotelomers. Examples of copolymers which can be used in the process of the invention and reactive solvents which can be used in their preparation are given in the following table.

Table

Mol of male - Mol of first Mol of second Solution - Ex.

acid anhydride monomer monomer agent no.

2 r 05 ethyl - η 5 νίηγί- '* acrylate acetate toluene qo TO ethyl1_ 2 n vinyl- y'U 1, U acrylate acetate xylene 13 10 0 10 ethyl1_1UjU χ'υ acrylate toluene on -io vinyl-ethyl-3 "acetate" benzene 12 6 0 10 VW1- i η ethylene "" acetate "acrylate xylene 14 2Q O 10 ^ y1-" acetate - toluene .9 2.5 1.0 ethylene - toluene 2.5 1.0 propylene - xylene methylene. vinyl 3.0 0.5 vinyl 0.5 acetate ketone methyl 14.0 1.0 vinyl toluene 7 ketone methyl 3.0 1.0 meth- toluene 3 acrylate methyl ethyl 6.0 1.0 meth-1 0 acrylate acrylate xylene nn ς acrylo-Q c vinyl-ethyl-nitrile acetate benzene 146185

Table cont.

Mol of male - Mol of first Mol of second Solution - Ex.

acid anhydride monomer monomer agent no.

m η ί n acrylic tert.butyl 10 '° 1 »° nitrile - benzene 3.0 0.5 acrolein qr methylmethyl' 0 acrylate ethyl ketone 14.0 1.0 acrolein - toluene 10 3.0 1.0 acrylamide - toluene 6 9.0 1.0 acrylamide 2.0 xylene τη π ς croton n K vinylcarbon acid U, acetate tetrachloride 7, ° 1.0 ° y ° * on '- toluene 3 3.0 1.0 styrene - acetic acid 29.0 1.0 styrene - toluene 5 The amount of initiator used can be varied within wide limits, but depends to some extent on the ratio of the monomers. All of the copolymers can be prepared using 20 parts by weight or more of the initiator, based on the weight of monomers, where this amount is needed for the copolymers in which the ratio of maleic anhydride content to the other monomers is high, e.g. . 14: 1 and upwards, such as 29: 1, if a high yield is desired. When the amount of maleic anhydride is decreased, the amount of initiator can also be reduced without affecting the yield.

The reaction participants may be mixed in various ways, for example, the initiator may be added to a solution of the monomers, or a solution of monomers and initiator may be added to a heated solvent.

The copolymers obtained finally can be hydrolyzed before being used to treat water. The hydrolysis can be carried out by means of water, an alkali or a mineral acid.

General procedure for the preparation of copolymers

A general method used to prepare the homopolymer in the comparative example and copolymers of Examples 1 to 11 was as follows:

Two solutions were prepared:

Monomer solution: maleic anhydride 30 parts by weight comonomer (s) toluene 70 parts by weight

Initiator suspension benzoyl peroxide Λ 70E paste in V dimethyl phthalate J G, 6 parts by weight toluene 35 parts by weight

The monomer solution was stirred and heated to 70 ° C and the initiator solution was added over 5 minutes. The solution was then refluxed at 110 ° G to 113 ° C for 6 hours. After cooling, the precipitated resin was separated from the toluene solution and dried under vacuum. The yields were usually $ 70-90, based on the weight of monomers.

The polymers were ground to a powder and boiled with water for one hour to hydrolyze the anhydride to the acid. In most cases, this made the polymer water-soluble, but occasionally (for example, with styrene / maleic anhydride 1: 3) it became necessary to add sodium hydroxide to dissolve the polymer.

The copolymers containing hydrolyzable comonomers, e.g. vinyl acetate, acrylonitrile or ethyl acrylate, was further hydrolyzed by taking an amount of water-hydrolyzed polymer solution containing in grams of polymer and adding 25 ml of 1 N NaOH. The mixture was boiled lightly in a beaker for 6 hours, then neutralized to pH 10 with 1 M HCl.

The amount of hydrolyzed copolymer added to the water to be treated may vary over a wide range and may range from 0.1 to 7 million. Preferably, the amount added is from 2 to 100 ppm, most preferably from 5 to 100 ppm.

The copolymers in question, in addition to being useful for preventing scales and as corrosion inhibitors, can also be used as "builders" for detergents.

Procedures for testing the copolymers

The high activities of the preferred copolymers and terpolymers against scaling salts were shown in an experimental boiler and in a seawater vaporization plant. These test methods are described in Examples 12 and 14. However, both are elongated procedures, and to test the large number of polymers described in the Examples, a simpler sample was devised. The threshold activity tests described below can be completed within 2 hours and provide very good information on the activity of the tested compound against scaling salts.

Threshold activity against CaCO 2 (Sample 1) 2 cnr * of a 1000 ppm solution of the scald inhibitor substance being tested is mixed in a beaker with 100 cnr of an aqueous solution containing 1.47 g / liter Ca 2 · 4Η20. 100 cc of an aqueous solution containing 0.646 g / liter of Na 2 CO 2 is added and the beaker is set on a hot plate so that the solution is heated to 90 ° C over 10 minutes. The solution is pumped through the colorimeter cell of an Auto Analyzer, and its optical density is continuously measured and printed on a waveform.

Two measurements of the optical density curve sheet as a function of time are noted: a) the initiation time (IT), defined as the time after mixing of the two solutions where precipitation occurs (judged by an increase in optical density), and b) the precipitation rate (hereinafter abbreviated to rate), defined as the maximum positive slope of the recorded optical density curve as a function of time, disregarding rapid short-term increases from baseline, of less than 15% of the optical density shown by a fully precipitated blank solution.

δ 146185 Threshold activity against CaSO ^

The sample is the same as that described above, except that 1 cc of a 1000 ppm solution of the scald inhibitor substance is added to 50 c of a water solution containing 20 g / liter of Ca (NO_) And, after mixing, 50 cc of an aqueous solution containing 17 g / liter of Na 2 SO 4 is added.

In both of the above samples, only 10 ppm of the scald inhibitor is used in the final sample solutions.

The initiation times and rates of CaCO2 and CaSO4 precipitation in the absence of additive are given in the tables in Examples 1 to 11.

An increase in the initiation time or a decrease in the precipitation rate in the presence of a test additive shows that the additive has a delaying effect on the precipitation of the scaling salts.

The procedures described above and those described in Examples 12 and 14 assess the activities of the test compounds against scaling salts at high temperatures. However, in some applications, it is necessary to slow the deposition of scales, especially of calcium sulfate, at ambient temperatures, i.e. 15-30 ° C. A test procedure is described in Example 15 which shows the efficiency of the copolymers in question in delaying the precipitation of CaSO 2 .2H 2 O at 20 ° C.

The method according to the invention is further illustrated by the following examples.

S equation six emp e1 Maleic anhydride homopolymer

Three polymers are prepared for comparison purposes by the general method outlined above. The average molecular weight by number of the first produced was found to be 450.

After hydrolysis with water, they were found to have the following threshold activities.

9 146185

CaC0 ^ activity CaSO ^ activity Ι · Τ · Rate Ι.Τ »Rate (min) (min) 1. Preparation 7 0.4 3> 30 2.» 5 0.6 3> 30 3. "5 0.6 3> 30

Blind (no polymer) 1 6 3> 30 Thus, homopolymaleic acid has a high activity against CaCO 2 but no activity against CaSO 2.

Example 1.

Maleic anhydride / acrylic acid copolymers

These were prepared as per the general method outlined above and hydrolyzed with water. The yields and average molecular weights by number obtained are given below. (Must stand for maleic anhydride).

Molecular ratio Mo / acrylic acid Yield $ Molecular weight 3: 1 86 490 8: 1 85 380 14: 1 85 29: 1 88

At threshold testing, they were found to have the following activity:

Molar ratio Mo / acrylic acid CaCO 2 activity C aS O 2 -act ivit an I.T. Rate I.T. Rate (min) (min) 3: 1 5-1.3 6> 30 8: 1 5 0.5 6> 30 14: 1 6 0.2.

29: 1.5 0.3 -

Blind 1 8 3> 30

Thus, the maleic / acrylic acid copolymer has high CaCO 2 activity and smooth activity against CaSO 2.

Example 2.

Maleic anhydride / methacrylic acid copolymers

These were prepared according to the general method in yields of $ 0-90 $ and hydrolyzed with water. 3: 1-MA / methacrylic acid copolymer had a molecular weight of 440. They had the following activities against CaCO3 and CaSO4:

Molar ratio Mo / methacrylic acid CaCO 2 activity CaSO 2 activity I.T. Rate I.T. Rate (min) (min) 3: 1 4 0.4 5> 30 7: 1 7 0.3 5> 30 14: 1 5 0.3 5> 30 29: 1 δ 0.4 5> 30

Blind 1 S 3> 30

Example 3

Maleic anhydride / crotonic acid copolymers

These were prepared according to the general method in yields of 70-SO%. They had the following activities against CaCO3 and CaSO4 after hydrolysis with water:

Molar Ratio Must / Crotonic Acid C aC 0 -act ivit et C aSO 2 -act ivit et I.T. Rate I.T. Rate (min) (min) 7: 1 6 0.2 4.5> 30 14: 1 6 0.3 4> 30 29: 1 7 0.2 4> 30

Blind 1 $ '3> 30

Thus, the maleic acid copolymer has a high activity against CaCO3 and only a marginal activity against CaSO4.

11 148185

Example 4

Maleic anhydride / ethylaerylat-eopolymere

These were prepared by the general method in 75-90% yields. The 3: 1 copolymer had a molecular weight of 560. After aqueous hydrolysis, the following activities against CaCO

Hydrolyzed with water

Molar Ratio May / Ethyl Acrylate CaCO O Activity GaSO Activity - -2—- -4—1_ I.T. Rate I.T. Rate (min) (min) 3: 1 4 0.4 3> 30 7: 1 3 0.15 3> 30 14: 1 5 0.3 3> 30 29: 1 6.5 0.3 3> 30

Blind 1 g 3> 30

Following hydrolysis with sodium hydroxide, the activities were as follows:

Hydrolyzed with sodium hydroxide

Molar ratio MA / ethyl acrylate CaCO 2 activity CaSO 4 activity I.T. Rat e I.T. Rat e (min) (min) 3: 1 3 0.3 9> 30 7: 1 4 0.3 12> 30 14: 1 3 0.2 11 4 29: 1 4 0.4 10 9

Blind 1 8 3> 30

Maleic anhydride-ethyl acrylate copolymers hydrolyzed with sodium hydroxide have good activity against CaSO4.

Example 5

Maleic anhydride / styrene copolymers

These were prepared by the general method in yields of 75 to 12 80 80. They were hydrolyzed with water and neutralized with sodium hydroxide prior to testing. The molecular weight of the 3: 1 copolymer was 738.

Molar ratio Must / styrene CaCOO activity CaSO, activity - -2- - -4 _ I.T. Rate I.T. Rate (min). (min.) 3 · 1 1 4j0 4> 30 7: 1 5 0.8 3> 30 14: 1 5 0.8 3> 30 29: 1 5 0.5 3> 30

Blind 1 8 3> 30

These copolymers have a high threshold activity against CaCO3 but are inactive against CaSO4.

Example 6

Maleic anhydride / acrylamide copolymers

These were prepared by the general method in yields of $ 75-85. The 29: 1 copolymers precipitated as a resin, while the other copolymers precipitated as powders. After hydrolysis with sodium hydroxide, the following threshold activities had:

Molar ratio MA / aerylamide CaCO4 activity CaSO4 activity I.T. (Rate IT Rate (min) (min) 3: 1 5 0.5 8> 30 7: 1 5 0.3 11> 30 14: 1 5 0.4 11> 30 29: 1 6 0.3 10 > 30

Blind 1 8 3> 30 Thus, sodium hydroxide hydrolyzed maleic anhydride acrylamide copolymers have higher activity against CaSO3 than homopolymaleic acid and equivalent activity against CaCO3.

3 146185

Example 7

Maleic anhydride / methyl vinyl ketone copolymer

These were prepared by the general method outlined above in yields of 7O-éOfo. The 3: 1 copolymer had a molecular weight of 440. After hydrolysis with water, the following threshold activities had:

Molar ratio Mo / CaCO activity CaSO activity methylvinyl ketone I.T. Rate I.T. Rate (min) (min) 3: 1 4 0.6 5> 30 7: 1 6 0.6 4> 30 14-Ί S 0.6 3> 30 29: 1 5 0.6 5> 30

Blind 1 S 3> 30 Thus, only uniform activity against calcium sulfate was found in certain maleic anhydride-methylvinyl ketone copolymers. However, they all had a similar activity against CaCO 3 as polymaleic acid.

Example S.

Maleic anhydride / methyl methacrylate copolymers

These were prepared by the general method outlined above in yields of 75-00 $. The 3: 1 copolymer had a molecular weight of 510. After hydrolysis with water, it had the following activities:

Molar ratio Mo / CaCO -, - activity CaSO, - activity methyl methacrylate ^^ I.T. Rate I.T. Rate (min) (min) 3: 1 3.5 0.3 3> 30 7: 1 5 0.2 3> 30 14: 1 6 0.6 3> 30 29: 1 5 0.3 3> 30

Blind 1 S 3> 30 14 146185

Following hydrolysis with sodium hydroxide, they had the following activities:

Molar ratio Do / CaCCL activity CaSO, activity methyl methacrylate ^ 4 I.T. Rate I.T. Rate (min) (min) 3: 1 3 0.5 7> 30 7: 1 3 0.6 é 6 14: 1 5 0.4 9 6 29: 1 3.5 0.3 10 4

Blind 1 g 3> 30 Thus, the copolymers hydrolyzed with sodium hydroxide show good activity against CaSO4. All the copolymers exhibit activity against celium carbonate.

Example 9

Maleic anhydride / vinyl acetate copolymers

These were prepared by the general method outlined above and the 3: 1 copolymer had a molecular weight of 657. After hydrolysis with water, the following threshold properties showed:

Molar ratio Mo / vinyl acetate CaCOO activity CaSO, activity - -1 ___ _ 4_ I.T. Rate I.T. Rate (min) (min) 3: 1 5 0.7 δ 6 7: 1 5 0.4 5> 30 14: 1 5 0.7 5> 30 29: 1 7 0.6 5> 30

Blind 1 S 3> 30

After hydrolysis with sodium hydroxide, the copolymers showed an enhanced activity against CaSO4 as shown below:

Molar ratio MA / vinyl acetate CaCO, activity CaSO. activity - -2-- -4_ I.T. Rate I.T. Rate (min) (min) 3: 1 5 2 8 2 7: 1 6.5 0.5 13 9 14: 1 7 0.6 13> 30 29: 1 5 0.6 10> 30

Blind 1 8 3> 30

Example 10.

Maleic anhydride / acrolein copolymers

These were prepared by the general method outlined above and hydrolyzed with water. Their thresholds were as follows:

Molar ratio MA / acrolein CaCOO activity CaSO. activity - -2- -4 I.T. Rate I.T. Rate (min) (min) 3: 1 10 '0.9 3 30 7: 1 4 0.8 3 30 14: 1 4 0.8 3 30 29: 1 5 0.8 5 30

Blind 1 8 3 30

The copolymers of maleic acid and acrolein showed high CaCO 2 activity but had no activity against CaSO 2.

Example 11

Several 3: 1 maleic anhydride / vinyl acetate copolymers were prepared by the general method outlined above but with different amounts of benzoyl peroxide. The yields, molecular weights of the resins and the threshold results after hydrolysis with water are shown below: 16 146185 Weight of benzoyl CaCCL activity CaSO, fefe.) 8.6 84 400 5 0.2 7 2 4.3 92 475 5 0.3 7 2 2.15 SO 400 5 0.1 7 3 1.07 75 440 5 0.8 8 2 0.54 67 330 4 0 , 3 S 2

Blind 1 8 3> 30

The catalyst concentration affected the yield of copolymer, but did not affect the level of the calcium carbonate and calcium sulfate activities.

Example 12.

Preparation and use of a maleic anhydride / vinyl acetate copolymer of 3: 1 mole ratio in a small test boiler 73.5 parts by weight of maleic anhydride and 21.4 parts by weight of vinyl acetate were dissolved in 240 parts by volume xylene and heated to 70 ° C. 4.5 parts by weight of ditertiary butyl peroxide in 20 parts by volume of xylene was added and the reaction mixture was heated to 130 ° C and kept at this temperature for 3 hours. A brown resin precipitated, which solidified upon cooling, and was easily separated from most of the xylene by decantation. Yield 86% (by weight of monomers). The average molecular weight by number of the polymer by vapor phase osmometry was found to be 675.

After hydrolysis with water and sodium hydroxide, the following results were obtained by threshold tests:

CaCO ^ CaSO ^ I.T. Rate I.T. Rate (min) (min)

After hydrolysis with water 7 0.3> 30

After hydrolysis with sodium hydroxide 5 1.6 9 5

Blind (no polymer addition) 1 8 3> 30 17 146185

The water hydrolyzed resin was tested for activity against alkaline scales in a laboratory test boiler boiling at 10 bar. Four soft steel sheaths, three of which contain 1 Kw permanently switched on electric cartridge heaters, are screwed through the base plate of the boiler so that they are in a vertical position. Thermocouples are brazed into the surface of each of the four sheaths, with the unheated sheath serving as a reference, to control all surface temperature changes as a result of scaling.

The boiler is supplied with natural water with a total hardness of 300 ppm (expressed as CaCO 2). It was "run" continuously at 10 bar for a period of 500 hours during which time the water was allowed to concentrate by a factor of 30 and then kept constant by removing concentrate in the form of a blow off. Routine analyzes of the water were performed daily. At the end of a sample, the heat sheaths were removed and the weight and thickness of the scales determined; the average increase in the temperature of the heat sheath surfaces during boiling was determined.

The following results show the beneficial effect of the method according to the invention. They also show that other conventional water treatment chemicals can be used at the same time without risk.

Wife. in Boiler- Weight of Thickness Temp- feed water stone boiler- of boiler- in ppm formation stone (g) stone rise-

Treatment rate (mm)

Na-CO, 230) 0.9 5.3 0.25 32 ° C

^)

Condensation product of naphthalene sulphonic acid and formaldehyde 13 146185

Table cont.

Wife. in Boiler- Weight of Thickness Temp- feed water stone boiler- of boiler- in ppm formation stone (g) stone rise-

Treatment rate (mm)

NaoCCL 230} 2 3)

Condensation Product)

of naphthalene- 10) <0.1 0.1 0 <5.6 ° C

sulfonic acid and form aldehyde)

Hydrolyzed homo) polymaleic acid 3) anhydride}

Na9CQ. 230) 23 j

Condensation Product)

of naphthalene-10 0 0 0 <5.6 ° C

sulfonic acid and formaldehyde}

Product according to Example 12 after aqueous 3) hydrolysis)

None - 14.7 0.76 6l ° C

Example 13

Preparation of a terpolymer of maleic anhydride, vinyl acetate and ethyl etherylate in the molar ratio of 9: 2: 1 117.6 parts by weight of maleic anhydride, dissolved in 320 parts by volume of xylene, was heated to 143 ° C. A solution containing 13.2 parts by weight of ethyl etherylate, 22.8 parts by weight of vinyl acetate and 5.2 parts by weight of ditertiary butyl peroxide in 160 parts by volume of xylene was maintained at 20 ° G and added to the stirred maleic anhydride solution at 140-145 ° C over 1 1/2 hours. Heating and stirring were continued for a further 1 1/2 hours, after which the xylene solution was cooled, poured from the solid resin and dried in a vacuum oven at 50 ° C. A yield of 160 grams of resin was obtained.

100 parts by weight of this resin was boiled with 300 parts of distilled water for one hour under reflux, and the solution was then distilled to remove traces of xylene. A solution of 100 parts by weight of sodium hydroxide in 200 parts of water was added and the reflux was continued for 2 hours. The excess sodium hydroxide was neutralized by the addition of concentrated hydrochloric acid until a pH of 10 was reached. The following threshold values were measured: C aC 0 - act in vit a C aS 0 ^ act in vit et. I.T. Rate I.T. Rate (min) (min)

Resin of Example 13 5 0.5 13 5.4

Blind 1 6 3> 30

Thus, the hydrolyzed polymer has a good threshold activity against calcium sulfate.

Example 14.

Preparation of a terpolymer of maleic anhydride, vinyl acetate and ethyl acrylate in the molar ratio of 6: 1: 1 294 parts by weight of maleic anhydride, dissolved in 300 parts by weight of xylene, was heated to reflux temperature with stirring. A solution consisting of 43 parts by weight of vinyl acetate 50 "ethyl acrylate 5T ditertiary butyl peroxide and 150" xylene was maintained at 20 ° C and added over a period of 2 hours to the refluxing maleic anhydride solution. Stirring and reflux were continued for an additional 4 hours. The temperature was reduced to 120 ° G and the lower resin layer was transferred to a separate vessel containing water at 30 ° C. The resin and water were stirred and the remaining xylene removed by distillation, during which part of the resin was dissolved. the required hydrolysis type, the resin solution was treated in three different ways.

20 146185

Polymer 14A - hydrolyzed with water

After boiling with water, the solids content was adjusted to 50% by weight. Yield of 50% solution = 793 parts by weight.

Polymer 14B - hydrolyzed with alkali

Sufficient 50% sodium hydroxide solution was added to raise the pH of the resin solution to 10. The temperature was kept at 0-90 ° C for 2 hours. During this time, more sodium hydroxide solution was added to keep the pH of 10. After cooling to 20 ° C, the solids content was adjusted to 50% by weight. Yield of 50% solution = 1000 parts by weight.

Polymer 14C - Hydrolyzed with Acid

The water was removed by distillation. 300 parts by weight 47% by weight hydrogen bromide solution was added and the solution obtained was slowly distilled for two hours. At the end of this time, the remaining hydrogen bromide was removed by distillation under reduced pressure. The resin was taken up in water, neutralized to pH 10 with sodium hydroxide solution, and the solids content was adjusted to 50% by weight.

Yield of 50% solution = 1000 parts by weight.

The excellent scavenging activities of the maleic anhydride / vinyl acetate / ethyl acrylate terpolymer are shown by: a) the threshold test b) the laboratory boiler test c) sample with seawater evaporator.

a. Threshold test values

The following test results were obtained at a solid polymer concentration of 10 ppm: 21 146185

CaCO3 CaSO,

Additive - ^ - a- I.T. Rate I.T. Rate (min) (min)

Polymer 14A 5 0.5 8 4

Polymer 14B 3 1.9 8 3

Polymer 14C 3 1.0 10 2

Blind (no polymer) 1 8 3> 30 b. Laboratory boiler sample

The scale inhibiting activity was measured in the test boiler described in Example 12 using the same procedure as described therein. The following results were obtained:

Wife. in Boiler- Weight of Thickness Tempera- ture water stone boiler- of boiler rise (ppm) formation stone

Treatment rate (g) (mm)

Na 2 CO, 230.0 0.5 0.5 <5.6 ° C

J)

Condensation product of naphthalene sulphonic acid and form aldehyde)

Polymer 14A 1)

None - - 14.7 0.76 6l ° c c. Antique stone activity in a seawater evaporation plant

The anticircular activity of the polymers in seawater evaporators was investigated as follows:

Seawater containing the additive was passed through a test cell at a rate of 10 liters per ml. day. Steam was passed into the cell through an aluminum / brass U-tube to maintain the temperature of 104 ° C, and air was blown into the cell to stir its contents and facilitate decomposition of the hydrogen carbonation in the seawater. After 14 days, the cell was separated and all scales deposited on the U-tube and cell walls were scraped off and weighed.

The tube's scaling rate and the total scaling rate were then determined. These values are derived from the following relationships:

Tube's scaling rate = Weight of material deposited on the U-tube Tube's capping rate Total volume of water passed through the cell.

Total Scale Rate - Total ** Solids a ^ l

Total volume of water passed through the cell.

The following results were obtained with a concentration of 5 ppm (solid) polymer in the feed water.

Scale formation rate in mg / liter

Additive ---- Stir Total

Polymer 14A 1.2 34.0

Polymer 14B 1.4 34.1

Nothing 16.6 46.0

Example 15 »

The excellent threshold activity of maleic anhydride / vinyl acetate / ethylerylate terpolymer against calcium sulfate at room temperature is illustrated by the following sample.

An aluminum stump is immersed in a supersaturated solution of calcium Λι sulfate containing 1750 ppm Ca 2 at 20 ° C. Crystallization takes place on the aluminum stump and on the walls and base of the container. At the end of the trial, the aluminum stump is removed for examination of the crystal structure. A certain portion of the sample solution is titrated with EDTA to determine the residual calcium content.

The following results were obtained:

23 14618E

Additive- Sample Remaining Wife. duration n2 +, »

Additive (ppm) (days) vPP J

Polymer 14A 5 4 1640

Polymer 14B 5 14 1720

Polymer 14C 5 30 1720

Homopolymer of maleic anhydride 5 4 1640 »» 5 14 £ 00 "” 10 14 yo

Nothing Nothing 4 6B0

Thus, after 30 days, the alkali hydrolyzed terpolymers of maleic anhydride, vinyl acetate and ethylerylate at a concentration of 5 ppm have a superior activity to the homopolymer at a concentration of 10 ppm.