CA1183861A - Poly(alkenyl) phosphonic acid and methods of use thereof - Google Patents

Abstract

Abstract of Disclosure A polymer composition having a repeat unit characterized by the formula

Description

POLY (ALKENYL~ PHOSPHONIC ACID
AND METHODS OF USE THEREOF

Field of the Invention . .

The present invention pertains to a composition and method of utilization of same to inhibit corrosion and control the formation and deposition of scale imparting compounds in water systems such as coolingg boiler and gas scrubbing systems.

Background of the Invention The problems of corrosion and scale formation and attendant effects have troubled water systems for years. For instance, scale tends to accumulate on internal walls of various water systems, such as boiler and cooling systems, and thereby materially lessens the operational efficiency of the system.

Deposits in lines, heat exchange equipment, etc., may originate fran several causes. For example, precipitation of calcium carbonate, calcium sulfate and calcium phosphate in the water system leads to an agglomeration of these scale imparting compounds along or around the metal surfaces which contact the flowing water circula-ting through the system. In this manner, heat transfer functions of the particular syst~n are severely impeded.

Corrosion, on the other hand, is a degradative electro-chemical reaction of a metal with its enviro~nent. Simply stated, it is the reversion of re~ined metals to their natural state. For example, iron ore is iron oxide. Iron oxide is re~ined into steel.
When the steel corrodes, it fo~ns iron oxide which, if unattended, may result in failure or destruction of the metal, causing the par-ticular water system to be shut down until the necessary repairs can be made.

Typically, in cooling water systems9 the formation of cal-cium sulfates calcium phosphate and calcium carbonate, among others,has proven deleterious to the overall efficac.y of the cooling water system. Recently, due to the popularity o~ cooling treatments using high levels of orthophosphate to promote passivation of the metal surfaces in contact with the systern water, i~ has becane critically important to control calcium phosphate crystalli~ation so that rela-tively high levels of orthophosphate may be maint~ained in the system to achieve the desired passivation without resulting in ~ouling or impeded heat transfer ~unctions which would nonmally be caused by calcium phosphate crystallization.

Although steam generating systems are somewhat different from cooling water systems~ they share a common problem in regard to deposit formation.

As detailed in the Betz Handbook of Industrial Water Con-ditioning, 8th Edition, 1980, Betz Laboratories, Inc., Trevose, PA
Pages 85-96, the formation oF scale and sludge deposits on boiler heating surfaces is a serious problem encountered in steam genera-tion. Although current industrial steam producing systems make use of sophisticated external treatments oF the boiler feedwater, e.g., coagulation, filtration, softening of water prior to its feed into the boiler system, these operations are only moderately effective.
In all cases, external treatment does not in itself provide adequate treatment since muds, sludge, silts and hardness-imparting ions escape the treatment, and eventually are introduced into the stream genera~ing system.

In addition to the problems caused by mud, sludge or silts, the industry has also had to contend ~ th boiler scale. Al-though external treatment is utilized specifically in an attempt to remove calcium and magnesium from the feedwater, scale formation due to residual hardness, i.e., calcium and magnesium salts, is always experienced. Accordingly, internal treatment, i.eO, treatment of the water fed to the system, is necessary to prevent, reduce and/or retard formation of the scale imparting compounds and their deposi-tion. The carbonates of magnesium and calcium are not the onlyproblem compounds as regards scale, but also waters having high con-tents of phospha~e, sulfate and silicate ions either occurring naturally or added for other purposes cause proble~s since calcium and magnesium, and any iron or copper present, react with each and deposit as boiler scale. As is obvious, the deposition of scale on the structural parts of a steam generating system causes poorer cir-culation and lower heat transfer capacity, resulting accordingly in an overall loss in efficiency.

Detailed Description of the Invention . .
In accordance with the invention, it has been surprisingly discovered that a homopolymer, having a repeat unit represented by the following structural fonnula I R

II~ ~ CH2 --- C
-x - P - x I _ O _ I n wherein R1 _ lower alkyl of from 1 to about 6 carbon atoms, and wherein X = OH, or OM where M is a cation; is effective in controlling the formation of mineral deposits and inhibiting corrosion in various water systems. At present, the polymer preferred for use is poly (isopropenylphosphonic acid) i.e., R1 ~ CH3.

For instance, the above polymers have proven e-Ffective as corrosion inhibition agents in simulated cooling water and boiler water systems. Also, the polymers have proven efficacious in their ability to inhibit the formation of CaS04, CaC03, and Ca3(P04)2.

The monomer, to be used in the polymerization process, may be prepared by a reaction mechanism involving the nucleophilic addi-tion of PCl3 to the carbonyl group of a compound corresponding to 3~36~

the desired alpha-beta ethylenically unsaturated phosphonic acid monomers. For instance, the reaction may proceed in accordance with the following equations:

5 (1) / C=O ~ PCl~3 ~ ~ / C
R R \ P+Cl3 H3C O~ H3C Cl \/ 2HOAC \/
10 (2) / C (HCl)--~ / C \
R ~ +Cl3 R ~ O(OH)2 ., H3C ~ /Cl (3) C . > CH2 = C - P(OH)2 / \ -HCl R ~O(OH)2 R

R is an alkyl group of from about 1 to 6 carbon atoms. In this manner, the desired monorner may be produced in a most cost effective manner due to the relativity low economic cost of the precursor ketone compounds, such as acetone.

It is also possible to produce the desired moncmer via de-hydration, by heating the corresponding alpha-hydroxyl alkyl phos-phonic acid at a temperature of about 125-250C, as is detailed in U. S. Patent 2,365,4660 After the desired monomer is isolated, radical chain addi-tion polymerization may proceed in bulk, suspension, solution, emul-sion, or thermal polymerization form. For instance, in suspension polymerization, the reaction may be initiated by benzoyl peroxide, with the monomer suspended in ethyl acetate or like solution. On the other hand, an aqueous solution polymerization reaction may be initiated via a conventional persulFate initiator. The fact that polymers were formed was substantiated by 31PMR spectroscopy where broad absorp-tions between about -20 and -40 ppm are known to indicate significant polymer fonmation~

The polymers should be added to the aqueous system, for which corrosion inhibiting, and/or deposit control actiYity is desired, in an amount effective for the purpose. This amount will vary depending upon the particular system for which treatment is desired and will be influenced by factors such as, the area subject to corrosion, pH, temperature, water quantity and the respective concentrations in the water of the potential scale and deposit form-ing species. For the most part, the polymers will be effective when used at levels of about 0.1-500 parts per million parts of water, and preferably from about 1.0 to 100 parts per million of water con-tained in the aqueous system to be treated. The polymers may beadded directly into the desired water system in a fixed quantity and in the state of an aqueous solution, continuously or intermittently.

3~

The polymers of the present invention are not limited to use in any specific category of water system. For instance, in addition to boiler and cooling water systems, the polymers may also be effectively utilized in scrubber syst~ns and the like wherein corrosion andtor the formation and deposition of scale fo~ning salts is a problem. Other possible environments in which the inventive polymers may be used include heat distribution type sea water desalt-ing apparatus and dust collection systems in iron and steel manufac-turing industries.

The poly (alkenyl) phosphonic acid polymers of the present invention can also be used with other components in ~rder to enhance the corrosion inhibition and scale controlling properties thereof.
For instance the polymers may be used in combination with one or more kinds of compounds selected from the group consisting of inorganic phosphoric acids, phosphonic acid salts, organic phosphoric acid esters, and polyvalent metal salts.

Examples of such inorganic phosphoric acids include con-densed phosphoric acids and water soluble salts thereof. The phosphoric acids include an orthophosphoric acid, a primary phos-phoric acid and a secondary phosphoric acid. Inorganic condensedphosphoric acids include polyphosphoric acids such as pyrophosphoric acid, tripolyphosphoric acid and the like, metaphosphoric acids such as trimetaphosphoric acidj and tetrametaphosphoric acid.

As to the other phosphonic acid derivatives which are to be added in addition to the poly (alkenyl) phosphonic acid polymers of the present inventionl there may be mentioned aminopolyphosphonic acids such as aminotrilnethylene phosphonic acid, ethylene diamine~
tetramethylene phosphonic acid and the like, methylene diphosphonic acid, hydroxyethylidene diphosphonic acid, 2-phosphonobutane 1,2,4, tricarboxylic acid etc.

Exemplary organic phosphoric acid esters which may be com-bined with the polymers of the present invention include phosphoric acid esters of alkyl alcohols such as methyl phosphoric acid ester, ethyl phosphoric acid ester, etc., phosphoric acid esters of methyl cellosolve and ethyl cellosolve, and phosphoric acid esters of poly-oxyalkylated polyhydroxy compounds obtained by adding ethylene oxide to polyhydroxy compounds such as glycerol, mannitol, sorbitol, etc.
Other suitable organic phosphoric esters are the phosphoric acid esters of amino alcohols such as mono, di, and tri-ethanol amines.

Inorganic phosphoric acid, phosphonic acid, and organic phosphoric acid esters may be salts, preferably salts of alkali metal, ammonia, amine and so forth.

Exemplary polyvalent metal salts which may be combined with the polymers of formula (I) above include those capable of dissociat-ing polyvalent metal cations in water such as Zn+-~, Ni++, etc, which include zinc chloride, zinc sulfate, nickel sulfate, nickel chloride and so forth.

When the polymer (I) is added to the aqueous system in com-bination with an additonal component selected from the group consis-ting of inorganic phosphoric acids, phosphonic acids, organic phos-phoric acids esters, their water-soluble salts (all being referred to hereinafter as phosphoric compounds), and polyvalent metal salts, a fixed quantity of said polymer ~I) may be added separately and in the state of aqueous solution into the system. The poly (alkenyl) phosphonic acid polymers (I) may be added either continuously or intermittently. Alternatively, the polymer (I) may be blended ~ th the above noted phosphoric compounds or polyvalent metal salts and then added in the state of aqueous solution into the water system either continuously or intermittently. The phosphoric compounds or S polyvalent metal salts are utilized in the usual manner for corrosion and scale preventing purposes. For instance, the phosphoric compounds or polyvalent metal salts may be added to a water system continuously or intermittently to maintain their necessary concentrations.

Generally, the phosphoric compounds should be present in the aqueous system in an amount of about 1-100 ppm (as P04) or the polyvalent metal salts should be present in an amount of about 1 to 50 ppm las metal cation).

As is conventional in the art, the phosphoric compounds or polyvalent metal salts may be added, as pretreatment dosages, to the water syst~n in an amount of about 20 to about 500 ppm, and thereafter a small quantity oF chemicals may be added, as maintenance dosages.

The polymers (I) may be used in combination with conven-tional corrosion inhibitors for iron, steel, copper, copper alloys or other metals, conventional scale and contamination inhibitors, metal ion sequestering agents, and other conventional water treating agents. Exemplary corrosion inhibitors comprise chromates, bichro-mates, tungstate, molybdates, nitrites, borates, silicates, oxycar-boxylic acids, amino acids, catechols, aliphatic amino surface active agents, benzotriazole, and mercaptobenzothiazole. Other scale and contamination inhibitors include lignin derivatives, tannic acids, starch, polyacrylic soda, polyacrylic amide, etc. Metal ion seques-~10-tering agents include polymines, such as ethylene diamine, diethylene triamine and the like and polyamino carboxylic acids, such as nitrilo triacetic acid, ethylene diamine tetraacetic acid, and diethylene triamine pentaacetic acid.

Examples The invention will now be further described with reference to a number of specific examples which are to be regarded solely as illustrative, and not as restricting the scope of th~ invention.

Example 1 , 10Preparation of Isopropenyl Phosphonic Acid _ _ . . . _ . _, To a 3~.3 neck flask equipped with a magnetic stirrer, thermometer, and pressure compensated addition funnel, was added 300 g (5.2 mole) of acetone. Phosphorus trichloride (730 g; 5.3 mole) was added rapidly through the addition funnel. The addition was only slightly exothermic. The mixture was stirred for 4 1~2 hours.
Acetic acid (1500 ml) was then added and a reflux condenser was added to the flask. The mixture became cloudy and refluxed as a copius quantity of hydrogen chloride was evolved. After the refluxing had subsided, hydrogen chloride gas was bubbled through the solution for 1/2 hour. The reaction mixture was then allowed to stir at room temperature overnight. The flask was equipped for distillation and volatiles were removed at atmospheric pressure until a head temperature of 118C was reached. A water aspirator was attached and the distillation continued until the pot tempera-2S ture reached 175C. The remainder of the volatiles were removed at ~ 1 mm and a pot ternperature of 180-190C. The product was a viscous golden-yellow liquid and weighed 571 9 (91%). After the mixture was cooled, sufficient water was added to giYe a 50% aqueous solution~ The 13CMR spectrum of aqueous product showed three doublets at ~ = 140.4, 132.7 ppm (J = 172.1 Hz); 129.9, 129.5 ppm (J= 9.8 Hz); 19.4, 18.9 ppm (J - 13.4 Hz). The 31PMR spectrum showed a single peak at ~ = -19.0 ppm. There was a trace of an inorganic phosphorus impurity.

Example 2 Non-Aqueous Polymerization of Isopropenylphosphonic Acid Anhydrous isopropenylphosphonic acid (100 9, 0.8 mole) was slurried with 250 9 of ethyl acetate under nitrogen in a 3-neck flask equipped for mechanical stirring and reflux. Benzoyl peroxide (4 g~ was added and the slurry was heated to reflux. Additional increments of benzoyl peroxide were added over a 6-7 hour time period until a total of 12 g had been added. During this period, the liquid monomer was converted to a gum which accumulated around the sides of the reaction flask. After cooling, ~he ethyl acetate was decanted and the remaining residue was triturated with acetone to give, after drying, 70~1 g of off-white polymer. The 31PMR showed an intense absorption at S = -26.7 ppm and a lesser intense multiplet at ~ = -30 to -34 ppm.

Example 3 Aqueous Polymerization of Isopropenylphosphonic Acid Isopropenylphosphonic acid (45 9, 547O, 0.2 mole) was treat-6~

ed Wittl sodium hydroxide (7 9, .175 mole) and heated to reflux under nitrogen. Ammonium persulfate (3 9) was added. The solution was refluxed for one hour and an additional 3 9 of initiator was added.
AFter three hours of additional reflux, a 31PMR of the product show-ed numerous polymer peaks from ~ - -32 to -24 ppm. A trace of monomer can be observed at ~ = -15.8 ppm.

Example 4 Preparation ofc~-n-hexylY~nylphosphonic Acid Phosphorus trichloride ~274.6 9; 2 mole) and 2-octanone ~256 9; 2.0 mole) were mixed and allowed to stir at room temperature as described in Example 1. Acetic acid (500 ml) was added, followed by HCl saturation. The mixture was allowed to stand overnight. Removal of the volatiles gave 328 9 (85%) of a thick oil as a residue. The 31PMR spectrum showed a peak at ~ = -19.0 ppm consistent with struc-ture.

Example 5 Aqueous Polymerization of~ -n-hexylvinylphosphonic Acid Sodium hydroxide (8 9; 0.2 mole) was dissolved in lO0 ml water. To this solution was added 38.4 9 (0.2 mole) Ofo~-n-hexyl-vinylphosphonic acid. A white precipitate formed which was completelysoluble at reflux. The solution was degassed and 5 9 of sodium per-sulFate was added. After two hours of reflux an additional 5 9 was added. Within the next hour, a very viscous foaming solution was formed. Reflux was continued for an additional four hours. A 31PMR
showed polymer absorption at ~ = -28 to -30 ppm and -25 ppm. A slight amount of monomer and some inorganic phosphorus contaminants were also present.

Example 6 In order to assess the perfo~nance of the polymers of the present invention, in their ability to control deposits in boiling water applications, they were tested in experimental boiler systems having electrical heat sources. In these experimental boiler systems, circulation of water is permitted via natural con~ection. Two probes are installed in the described path and are positioned so that one probe sits above the other. The probes permit measurement of deposition, if any, at two locations in the path through which the water circulates.

The tests conducted using these experimental boilers were operated under the conditions specified in Tables VI and VIa below.
After test completion, the probes were removed and chemical analyses were employed to detenmine total deposit quantities. The deposits were dissolved in hydrochloriG acid and hydrofluoric acid and the solutions were analyzed for calcium, magnesium, phosphate and silica, since the test program was designed to evaluate this type of deposit.
Deposit weights were calculated from the solution and the results are reported in Tables VI and VIa hereinbelow.

TABLE VI
Low Pressure 8Oiler Evaluation of Poly~isopropenylphosphonic acid) Treatment Boiler Concentration Average Deposit*
Type ppm _ (g/ft2) 5 Versa TL-3 5 2.2 Versa TL-3 - 10 1.2 PIPPA 10 1.9 PIPPA 20 1.4 Versa TL-3 = sulfonated styrene maleic anhydride copolymer sold by National Starch Co., molecular weight 3000 H H H H

~c-- c - I 1-- c--c I I I I I I I I
I_ H ~ _l lo,jC ~0 ,C~0 S03Na x:y = 3:1 PIPPA = poly(isopropenylphosphonic acid) * = average between lower and higher probe Test Conditions:
Pressure: 300 psig Heat Flux: 185,000 BTU/ft2/hr.
Residual Phosphate: 20 ppm Feedwater Hardness: 15 ppm as CaC03 (10 Ca/5 Mg) Cycles: 15 Steam Rate: 8 lbs/hr.

~y fr~ ~ avA~

TABLE VIa High Pressure Boiler Evaluation of Poly(isopropenylphosphonic acid) Treatment Boiler Concentration Average Deposit*
Type ppm ~g/ft2) _ 5 Control _ 4 5 Control - 5.6 PIPPA 10 0.7 PIPPA 20 0~5 v~ PIPPA~ 40 0.6 Tamol 850 20 2.2 Tamol 850 20 1.1 Daxad 30S 20 0.5 .~
Tamol 850 = an aqueous acrylic emulsion sold by Rohm ~ Haas Daxad~ OS = sodium salt of carboxylated polyelectrolyte sold by W. R. Grace PIPPA = poly(isopropenylphosphonic acid) * = average between lower and higher probe Test Conditions:
Pressure: 1450 psig Feedwater Iron Concentration: 3.2 Fe Residual Phosphate: 20 ppm Steam Rate: 16 lbs/hr.
Heat Flux: 300,000 BTU/ft2/hr.

r ~ Q ~ k 6:~

In order to evaluate the efficacy of isopropenylphosphonic acid as a corrosion inhibitor in cooling water systems, this polymer was tested utilizing a procedure commonly referred to as the "Spinner Test".

Example 7 The tests were each conducted with two non-pretreated low carbon steel and two pretreated LCS coupons which were immersed and rotated in aerated synthetic cooling water for a 3 or 4 day period.
The water was adjusted to the desired pH and readjusted after one day if necessary; no further adjustments were made. Water temperature was 120F. Rotational speed was maintained to give a water velocity of 1.3 feet per second past the coupons. The total volume of water was 17 liters. Cooling water was manufactured to give the following conditions:

SCW6 (pH=6) SCW7 (pH=7) SCWg (pH=8) ppm Ca as CaC03170 170 170 ppm Mg as G~C03110 110 110 ppm SiO2 0 15 15 ppm Na2C03 0 0 100 Corrosion rate measurement was determined by weight loss measurement. Prior to immersion, coupons were scrubbed with a mix-ture of trisodium phosphate-pumice, rinsed with water, rinsed with isopropyl alcohol and then air dried. Weight measurement to the nearest milligram was made. At the end of one day, a weighed coupon was removed and cleaned. Cleaning consisted of immersion into a 50%

solutio`n of HCl for approximately 20 seconds, rinsing with tap water, scrubbing with a mixture of trisodium-pumice until clean, then rinsing with tap water and isopropyl alcohol. When dry, a second weight measurement to the nearest milligram was made. At the tenmination of the tests, the remaining coupon was removed, cleaned and weighed.

Corrosion rates were computed by differential weight loss according to the following equation:

Corrosion Rate = Nth Day Weight Loss - 1st Day Weight Loss where N = 3 or 4.

The cooling water was prepared by first preparing the following stock solutions Solution A - 212.4 g CaCl2 2H20/l Solution B - 229-9 9 M9S4 7~l2/l Solution C - 25.2 9 NaSiO3 9H20/l Solution D - 85 9 Na2C03/l Treatment Solutions - 1~7~o solution (1.7 9/100 ml) Then, these solutions were combined using the following order of addition:

1. To 17 l of de-ionized water add, with stirring, (a) 20 ml of Solution A, and (b) 2G ml of Solution B.

2. Adiust pH to 6.

3. With stirring add treatment.

4. For SCW7 add 20 ml of Solution C and, adjust pH to 7Ø

5. For SCWg add 20 ml of Solution D and adjust to pH 8.0 The results of these tests are reported hereinbelow in Table VII in terrns of mils per year (mpy) and ppm (actives) of the polymer treatrnent in each bathO

TABLE VII

Cooling Water Corrosion Study Inhibitor Active ppm Water Corrosion LCS Corrosion PTLCS
PIPPA 10 SCW6 99.5 57 PIPPA 100 SCW6 14.5 7.5 PIPPA 10 SCW7 67.0 30.0 PIPPA 100 SCW7 14.0 8.0 PIPPA 10 SCWg 30.0 24.0 PIPPA 100 SCWg 11.0 1.5 PIPPA = Poly(isopropenylphosphonic acid) LCS = Low carbon steel PTLCS = pretreated low carbon steel Example 8 One method of evaluating deposit control activity of a material consists of measuring its ability to prevent bulk phase precipitation of a salt at conditions for which the salt would normally precipitate. It is additionally important to recognize that the material being evaluated is tested at "substoichiometric" con-centrations. That is, typical molar ratios of precipitating cation to the material being eYaluated are on the order of 20:1 and much greater. Consequently~ stoichiometric sequestration is not the route through which bulk phase precipitation is prevented. This well known phenomenon is also called "threshold" treatment and is widely - practiced in water treatment technology for the prevention of scale (salt) deposits from forming on various surfaces. In the results that follow calcium phosphate, calcium carbonate, and calcium sul-fate salts commonly found in industrial water systems under various conditions have been selected as precipitants. The polymers of the present invention has been evaluated for their aility to prevent precipitation (i.e., inhibit crystallization) of these salts. The results are expressed as "percent inhibition", positive values indicate that the stated percentage of precipitate was prevented from being formed. Except as where noted to the contrary, the following conditions, solutions, and testing procedure were utilized to perform the calcium carbonate, calcium phosphate and calcium sulfate inhibi-tion tests, the results of which are reported herein in Tables VIII
and IX.

36~

CALCIUM PHOSPHATE INHIBITION PROCEDURE
.
Conditions Solutions . _ T = 70C 36076 CaCl2 2H20/liter DIH20 pH 8.5 0.4482g Na2HP04/liter DIH20 5 17 hour equilibration Ca+2 = 250 ppm as CaC03 P04-3 = 6 ppm Procedure _ 1) To about 1800 ml DIH20 in a 2 liter volumetric flask, add 20 ml of CaCl2 2H20 solution Followed by 2 drops of conc. HCl.
2~ Add 40 ml of Na2HP04 solution.
3) Bring volume to 2 liters with DI water.
4) Place 100 ml aliquots of solution in 4 07 glass bottles.
5) Add treatment.

6) Adjust pH as desired.

7) Place in 70C water bath and equilibrate for 17 hours.
~) Remove samples and filter while hot through 0.2 u filters.
9) Cool to room temperature and take Absorbance measurements using Leitz photometer (640 nm).

Preparation for Leitz a. 5 mls filtrate b. 10 mls Molybdate Reagent c. 1 dipper Stannous Reagent d. Swirl 1 minute, pour into Leitz cuvette;
wait 1 minute before readingO
10) Using current calibration curve (Absorbance vs ppm P04-3) Find ppm P04~3 of each sample.
Calculation:
ppm P04~3 rtock)~ --r~ x 100

8~

CALCIUM SULFATE INHIBITION PROCEDURE
Conditions Chemicals pH = 7.0 1 x 1o-l M CaCl2 2H20 T = 50C 1 x 10-1 M Na2S04 24 hour equilibration Ca+2 = 2000 ppm S04-2 = 4800 ppm Procedure 1) Add 50 ml of 10-1 M CaCl2 2H20 pre-adjusted to pH 7.0 to a 4 oz. bottle.
2) Add treatment.
3) Add SO ml of 10 1 M Na2S04 preadjusted to 7Ø
43 Heat samples for 24 hours in a 50C water bath.
5) Cool for 30 minutes, at least.
6) Filter 5 ml through 0.45 u filters.
7) Add NaOH to pH 12.0 and dilute to 50 ml with DI H20.
8) Add Ca+2 indicator (1 level).

9) Titrate ~o purple-violet endpoint with EDTA.
Calculation:
mls titrant (treated) - mls titrant (control) x 100 ~ In~llbltln mls ti~trant (Ca+2 stockr - mls titrant (control) ~3~

CALCIUM CARBONATE INHIBITION
Conditions Solutions pH = 9.0, 8.5 3.259 CaCl2 2H20/liter DI H20 T = 70C 2.489 Na2C03/liter DI H2020 5 hour equilibrium 442 ppm Ca+2 702 ppm C03-2 Procedure 1) Add 50 ml CaCl2 2H20 pre-adiusted to pH 9Ø
2) Add 40 ml of Na2HP04 solution.
3) Add 50 ml Na2C03 pre-adjusted to pH 9Ø
4) Heat 5 hours at 70~C water bath. Remove and cool to room temperature.
5) Filter 5 mls through 0.2u filters.
6) Adjust samples to pH <1.0 with conc. HCl ( 19 Conc. HCl).
7) Allow to stand at least 15 minutes.
8) Dilute to 50 mls with DI H20.
9) Bring pH to 12.0 with NaOH.

10) Add Ca~2 indicator (1 level~.
20 11) Titrate with EDTA to purple-violet endpoint.
Calculation:
. . . ml EDTA titrated (treated) - ml E~TA titrated (control) % Inhlbltln ml EDT-A titrated (Ca+2~stock-ml EDTA titrated (controlnX 100 TABLE VI I I
% Inhibition CaC03 Inhi _tlon 1 ppm 3 ppm 5 ppm PIPPA 8.9 32.3 38.3 5DQ 2000 69 71 75.4 DQ 2010 61 67 64.1 CaS04 Inhibition 1 3 5 PIPPA 37.3 54 99 DQ 2000 93.7 99.4 98.6 10DQ2010 31.3 30.9 31.0 Ca3(P04)~ Inhibitlon 10 25 50 PIPPA 41.0 41.0 43.1 DQ 2000 23.5 26.1 38.2 DQ 2010 9.0 9.0 11.3 PIPPA = Poly( isopropenylphosphonic acid) . . ~..,--~ 37 DQ 2010 = 60% active acid solution, M.W. = 206 OH OH OH
O = P - C - P = O Monsanto 20DQ 2000~= 50% activc acid solution, N

/1 \
HCH HCH l~CH

OH - P - OH OH - P - OH HO - P - 0~l Monsanto O O O

`Trc~d ~ ~)ark TABLE IX
% Inhibition CaC03 Inhibition 1 ppm 3 ppm 5 ppm Poly-d_-n-hexylvinyl phosphonic acid 1.9 5.9 31.5 DQ 2000 52.2 5901 70.4 DQ 2010 58.6 68.5 59.6 AA/HPA 11.8 44.3 45.3 Ca3(P04)2 Inhibition* 5 ppm 10 ppm20 ppm Poly~ n-hexylvinyl phosphonic acid 13.6 15.4 71.5 DQ 2000 14.3 16.1 19.5 DQ 2010 9.0 22.7 7.4 AA/HPA 55.8 80.2 84.6 CaS04 Inhibition1/2 ppm 1 ppm 3 ppm Poly-c~-n-hexylvinyl phosphonic acid 6.4 19.3 85.3 DQ 2000 8.9 95.3 97.9 DQ 2010 4.4 6.0 27.4 * = pH ~ 7.5 AA/HPA = acrylic acid/2-hydroxypropyl acrylate, MW 6,000 molar ratio AA:HPA - 3:1 DQ 2000 and DQ 2010 - same as in Table VIII.
While this invention has been described with respect to particular embodiments thereof, it is apparent that numerous other forms and modifications of this invention will be ob~ious to those skilled in the art. The appended claims and this invention generally should be construed to cover all such obvious forms and modifications which are within the true spirit and scope of the present invention.

e ~ k

Claims (32)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A water soluble polymer (I) having a repeat unit represented by the formula:

wherein Rl = lower alkyl of one to about six carbon atoms, and wherein X = OH or OM, where M is a cation.

2. A polymer as defined in Claim 1 wherein Rl =
CH3.

3. A polymer as defined in Claim 1 wherein Rl =

C6H13.

4. A composition comprising the polymer as defined in Claim 2 and an effective amount of a corrosion inhibitor compound (II) selected from the group consisting of inorganic phosphoric acids and water soluble salts thereof, phosphonic acids and water soluble salts thereof, organic phosphoric acid esters and water soluble salts thereof, and polyvalent metal salts capable of being dissociated to polyvalent metal ions in water.

5. A composition comprising the polymer as defined in Claim 3 and an effective amount of a corrosion inhibitor compound (II) selected from the group consisting of inorganic phosphoric acids and water soluble salts thereof, phosphonic acids and water soluble salts thereof, organic phosphoric acid esters and water soluble salts thereof, and polyvalent metal salts capable of being dissociated to polyvalent metal ions in water.

6. Composition as defined in Claim 4 or 5 wherein said inorganic phosphoric acid (II) is a member selected from the group consisting of orthophosphoric acid, primary phosphoric acid, secondary phosphoric acid, pyrophosphoric acid, tripolyphosphoric acid, trimetaphosphoric acid, tetrametaphosphoric acid and water soluble salts thereof.

7. Composition as defined in Claim 4 or 5 wherein said phosphonic acid (II) is a member selected from the group consisting of ethylene diamine tetramethylene phosphonic acid, methylene diphosphonic acid, hydroxyethylidene diphosphonic acid and 2-phosphono-butane 1,2,4-tricarboxylic acid.

8. Composition as defined in Claim 4 or 5 wherein said polyvalent metal salt is a member selected from the group consisting of zinc chloride, nickel chloride, zinc sulfate and nickel sulfate.

9. Method of controlling the deposition of scale imparting precipitates on the structural parts of a system exposed to an aqueous medium containing scale imparting precipitates under deposit forming conditions, said scale imparting precipitates being selected from the group consisting of calcium carbonate, calcium phosphate, and calcium sulfate, said method comprising adding to said aqueous medium an effective amount for the purpose of a water soluble polymer (I) having a repeat unit represented by the formula wherein R1 is a lower alkyl moiety of one to about six carbon atoms, and wherein X = OH or OM, where M is a cation.

10. Method as defined in Claim 9 wherein said polymer (I) is added to said aqueous medium in an amount of about 0.1-500 parts polymer (I) per one million parts of said aqueous medium.

11. Method as defined in Claim 10 wherein said system is a steam generating system.

12. Method as defined in Claim 10 wherein said system is a cooling water system.

13. Method as defined in Claim 10 wherein said system is a gas scrubbing system.

14. Method as defined in Claim 9 further comprising adding to said system, an effective amount for the purpose, of a compound (II) selected from the group consisting of inorganic phosphoric acids and water soluble salts thereof, phosphonic acids and water soluble salts thereof, organic phosphoric acid esters and water soluble salts thereof, and polyvalent metal salts capable of being dissociated to polyvalent metal ions in water.

15. Method as defined in Claim 14 wherein said inorganic phosphoric acid (II) is a member selected from the group consisting of orthophosphoric acid, primary phosphoric acid, secondary phosphoric acid, pyrophosphoric acid, tripolyphosphoric acid, trimetaphosphoric acid, tetrametaphosphoric acid and water soluble salts thereof.

16. Method as defined in Claim 14 wherein said phosphonic acid (II) is a member selected from the group consisting of ethylene diamine tetramethylene phosphonic acid, methylene diphosphonic acid, hydroxyethylidene diphosphonic acid and 2-phosphono-butane 1,2,4-tricarboxylic acid.

17. Method as defined in Claim 14 wherein said polyvalent metal salt is a member selected from the group consisting of zinc chloride, nickel chloride, zinc sulfate and nickel sulfate.

18. Method as defined in Claim 14 wherein said compound (II) is added to said system in an amount of 20 to about 500 parts per million parts of said system.

19. Method as defined in Claim 9 wherein Rl = CH3.

20. Method as defined in Claim 9 wherein Rl = C6H13.

21. Method of inhibiting corrosion of metallic parts of an aqueous system comprising adding to said system an effective amount of a water soluble polymer (I) having a repeat unit represented by the formula wherein Rl is a lower alkyl group of one to about six carbon atoms, and wherein X = OH or OM, where M is a cation.

. .

22. Method as defined in Claim 21 wherein said polymer (I) is added to said aqueous medium in an amount of about 0.1-500 parts polymer I per one million parts of said aqueous medium.

23. Method as defined in Claim 21 wherein said system is a steam generating system.

24. Method as defined in Claim 21 wherein said system is a cooling water system.

25. Method as defined in Claim 21 wherein said system is a gas scrubbing system.

26. Method as defined in Claim 21 further comprising adding to said system, an effective amount for the purpose, of a compound (II) selected from the group consisting of inorganic phosphoric acids and water soluble salts thereof, phosphonic acids and water soluble salts thereof, organic phosphoric acid esters and water soluble salts thereof, and polyvalent metal salts capable of being dissociated to polyvalent metal ions in water.

27. Method as defined in Claim 21 wherein said inorganic phosphoric acid (II) is a member selected from the group consisting of orthophosphoric acid, primary phosphoric acid, secondary phosphoric acid, pyrophosphoric acid, tripolyphosphoric acid, trimetaphosphoric acid, tetrametaphosphoric acid and water soluble salts thereof.

28. Method as defined in Claim 21 wherein said phosphonic acid (II) is a member selected from the group consisting of ethylene diamine tetramethylene phosphonic acid, methylene diphosphonic acid, hydroxyethylidene diphosphonic acid and 2-phosphono-butane 1,2,4-tricarboxylic acid.

29. Method as defined in Claim 21 wherein said polyvalent metal salt is a member selected from the group consisting of zinc chloride, nickel chloride, zinc sulfate and nickel sulfate.

30. Method as defined in Claim 21 wherein said compound (II) is added to said system in an amount of 20 to about 500 parts per million parts of said system.

31. Method as defined in Claim 21 wherein Rl = CH3.

32. Method as defined in Claim 21 wherein Rl = C6H13.