CA1043653A - Method of inhibiting the precipitation of scale-forming salts - Google Patents

Abstract

ABSTRACT OF DISCLOSURE

A method of inhibiting the precipitation of scale-forming salts of calcium, magnesium, barium and strontium from aqueous systems comprising adding to the aqueous system a telomeric compound of the formula:
or salts thereof, wherein R11 is hydrogen, methyl or ethyl, R is hydrogen, 1-18C alkyl, 5-12C cycloalkyl, aryl, aralkyl, a residue of formula:

Description

Tllc l~rc~ in~ tio~ latcs 1;o th~ trcatlllent ~` c~f aqueol~ systclns.
The majority of natural waters~ and aqucous ~ystem3 in ~onorAL, contain di~solvecl salts of mctals such a~ calci~n~, ma~ncsium, barium and strontiwn. When tho watcr or aqueous sys~e~n is subjoctcd to heatin~, the dissolved ,salts ~ay be converted to in301uble salts and dcposited as ~cale on heat tra~sfer surface~ in contact with the water or aqueou~ system. If the water or aqueous sy~tem is conccntratcd evcn l~ithout heating, in~olublc ~alts may also be precipitated.
Salt precipitation and scale deposltion are troublesoole and can cause increased costs in maintaining aqueous systellls ln good worlcing order. ~nong the problems caused by scale ; doposits are obstruction of fluid flow, impedance of heat transrer, wear of mctal parts, shortening of equipment lifc, loc~ ed corrosion attack, poor corrocion inhibitor performance, ~and un~choduled cquipment shutdown. Tho~e problems can Qrlse j ~n watel or oil wolls~ watcr pipes, steam power plants, ¦ water desalination plants, reverso osmosls equipment utilisin6 ¦~ ~ aqueou~ solution~, heat oxchange oquipment, and equipmcnt concerned w~th the transport of products and by-products in aqueous mcdia ~¦ ( e,g.fly ash formed during the combustion of coal ln tho production of electricity). The ranGe of temperature over which these proccssos operate is widc, for exnmple amblent l tomperature~ are used for cooling watcr and elevated temperaturos ¦ aro usod for ~team power piants.
Ono method u3ed to overcome the di~advantages a~sociated wlth ~calo ~ormution has involved tho dismantline of cquipmcnt ~i ~.......... . . .
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:~': , , ,::,, : . . . , ' ' ', , . -1043f~S3 to enabl~ the accunl~llated d~posits to bo cleaned out.
This procc~urc is ~09~1y and does not provent scale re~eposition.
Another mcthod involves the uge Or strong allcali solutio~
for the removal of,in particular,sulpll~te scale. It has been alleGed that under suitable conditions of temperaturc and timo the allcali treatment eve~ltually provides an initial break up of the scale,which can then ~e removed by mechanical moans, Such a metihod requires considerable time, and tthe removal of scale subsequent to treatment is often difricult.
There is there~ore a need in this field for a composition which can be added to water or aqueous systems in very small quantitios and which can cut down the rate at which insolllble salts are precipitated over a wide temperature range.
Furbhermore when any scale is formed, it should desirably be oaslly romovable ~rom surrace3 by mechanical moans.
A number Or additives haive been proposod for addition to water or aqueous systoms ror these purposo~ among tllelll c~rta~n polyphosphates, polycarboxylic acids, such as polymerisoc1 acryllo acid and polymerised methacrylic acid.

.! ' The polyphosphates ultimately eive a sort-i rriable scale which i8 easily removed from surraces,whereas the use of ~olycarboxylic acid result 5 in a hard adherent eggshell-like so~le.
Where water-treatment processes involving heat are used, tho temperatures are increasin~, and since polyphosphate addlblvc~ are roadily hydrolysed at hi~h tcmperatures and a6 a rcsult can give rise to the precipitation of insolublc .,; , . , calcium orthophosphate,thci~ usefulness is consequently li~uited.
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1043~3 According to the present invention, there is provided a method of inhibiting the precipitation of the scale forming salts of calcium, mag-nesium, barium and strontium from aqueous systems comprising adding to the aqueous system from 1 to 200 parts per million of a product comprising a telomeric compound of the formula:

o R - P - (CH2CR ~ CH2CHRllC02H

or salts thereof, wherein Rll is hydrogen or a methyl or ethyl residue, R is hydrogen, a straight or branched alkyl residue having from 1 to 18 carbon atoms, a cycloalkyl residue having from 5 to 12 carbon atoms, an aryl residue, an aralkyl residue, a residue of formula:
_ ~cH2cRll)m - CH2CHRllC02H

whereln Rll has its previous significance, and the sum of n ~ m is an integer of at most 100, or a resitue -OX wherein X is hytrogen or a straight or - branched alkyl residue having from 1 to 4 carbon atoms, and Rl is a resitue -OX wherein X has its previous significance.
Salts of the telomeric compounds of formula I are compounds in i, which some or all of the acidic hydrogens in the acidic compounds, of formula .
I have been replaced by alkali metal ions, ammonium ions or quaternised amine raticals. These salts also have goot activity in inhibiting the precipita-tion of insoluble salts from aqueous solution.

The compounts of formula I, reaction protucts containing ~" .

~ .
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,~.., _ 4 _ i," ' ~
A
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~0~;~653 compound.s Or f`ornlula I and s.~lts ~her~of are efrcctive in in}li~iting t}lc ~Icposition Or scalc and prccip.itation of salts from aquoous ~lutloIIs. The scal~ for~ salt~ are dorived rroln calciulll, m~esiutn~ bariu~n or strontium c~tions and anions ~uch as sulphatc, carbonate, hyd~oxi~e, p1losphate or ~ilicate. The compounds of formula I, re~ction ~roducts containillg compounds o~ forlnula I and salts thereof are particularly erfective in i~1ibiting the deposition of calcium sulphate, maencsium hydroxlde and calcium carbon~te scalc9.

Preforably R" is hydrogen and i.t i5 preferred tl1at tho sum o~ m and n i5 an integer less t11an 60.
Examples of substituents R include hydro~en, a ~traight-or branched chain alkyl residue having from 1 to 10 carbon atoms~ a cyclohexyl~ a phenyl~ or a benzyl residue~ or a residue -OX wherein X has its previous ~ignificance.

Examples o~ the ba~e~- with which compounds Or formul~ I
,, .
may be rencted in order to ~orm partial or comple~o ~alts ~re bhe hydroxides and carbonatos o~ sodlum, potassiwn and .; ammonia. Similarly organic bases may bo eMploycd. For , . . . .
lnstance primary, secondary and tertiary alkyl and substitutcd ~lkyl aminos in which the total carbon number does not oxceed .. i . .
~ twelve, suCh as tricthnnol~mine. . . .
.~ The ¢ompounds o~ formula I are not new; the compounds -and their proccss of manu~acture are described in U.S, Patent .~',~ , . ..
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eciric~tion l~.o 2,95,-,cj31. 10 ~,, .
~I-IS the co;r.~ounds o~ forlnul.l I m~y ~,c prcpared in a co~cnicnt manner by reacting Val'iOUS molar ratios of a compotl~ld Or forll~ula :-CH2 = C~" - C02~1 II
.'~
whcrein n~ has it5 previous si6nificance~ with n compo~nd Or fornlula :-R
R"~ - P
. . R~
wherein Rt has its previou.s signiricance and Rll I i8 hydrogon, a straight or brQnche,d chain alkyl residuc havin~ ~roln 1 to 18 carbon atoms, a cyoloalkyl residue having from 5 to 12 oarbon atoms, a I)henyl, a benzyl residue or OX wherein X has it9 piovious fiignificance.
Altornatively a salt Or the compound o~ formula III
mAy be omployed in which the acidic hydroeons havo been partlally or complctel-y replaced by cntions derived ~rom the ~alt forulin~
bases hcreinbeforo describod . The reaction i9 carricd out in a q~olvcnt inert under the rcaction conditions and in the presence of a reaction lnitiator. Suitable reaction solvents are for instance, w~ter, aqueous c,tllanol or dioxan. Suitable reaction initiatorJ
lncludc materials which decompose, under thei rcaction condition~
-1 to ylold ~r~e, radicnls. Examplos of such matcrials are blsazoisobutyronitrile,organic peroxides such as benzoyl peroxide~
meth~l ethyl~etone p~eroxide~ ditertiary butyl ~!

~.- ' ", ` 6 10 ~3~j~3 peroxidc ~nd mono1~utyl hydroperoxidc, and oxidising a~ents such as hydrogen peroxide, sodium perbora.te and sodium per-sulphate.
Th¢ products oI this ~rocess aro ~btaincd a~ solutions.Thcs~ m~y ~e subjected to partial or complete evaporati.on under reduccd pressurc. The unpuriricd reaction products may be used AS the te~omeric products in the n,cthod of th(~
invention. The rcaction products may also be purifiec1.
The puriri.cation procedure may be:
i) by evaporation of roactioT1 solvcnt, dissolving t~e rcsidue in w~ter, washing with a wat~r . inmiscible or.ganic ~olvent e.g, etller and evaporation Or the aqueous solution ii) by evaporation of rcaction solvent, dissolvi.ng the re~idue in methanol and reprecipi.tation by addition of ethor.
When the reaction products are employed without purification the ratio of reactants is important in that tl1e activity of the product varie~ accordingly. For cxample ; the product derived fro~ reactln~ 7 ~ole equivalent~ of acrylic acid and 1 mole equivalent of hypophosphorou~ aoid has a greater I activity in inhibiting for instance calcium sulphate pr¢cipi-¦ tation compared to products deri~ed from reactin~ acrylic acid ~ and hypopho~pho~ou4 acid in t}lo l~olar ratios o~ ~:1; 14:1 and r 28 s 1 ro9poctively. Purification of thc product deriYed from ; the reaction of 2 mole equivalents Or acrylic aold and 1 molc oqulvalellt Or hy,popho.sphorou~ aci~ by preci.pitation from its methanol solution ~y ~h~ addit~on of ethor resulted in a product whic}l exhibited ~ood acti~lty.
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0;~ :iS3 S~lt~ of the co~npoun~s of formul~ I in which some or all of t]lC acidic h~ro~ens in the colllpounds Or formul~ I
have bcen rop]accd by the catiolls derived I'rom tlle sal~
rorminG b~ses ~lereinbc3~ore derined, may be prepared by mixin6 ~n aqueous or alcoholic solution of the compound Or fornlula with an aqueous or alcoholic solution containing an amoun~
Or the requisite baso in excess of, equal to or less than the stoichiometric requiremcnt. The solvent may thcn be removed by evaporation. In many of the water-containing systems whcre inhibitors of this inventiQn would prove use~ul, thc wator is ~ufficiently alkaline to eff~ct neutralisation and only the product Or the invention need be added.
The precise nature of tho productQ Or this preparative process is not entirely clear. Nuclear ma~netic resonance examillation has shown,however, that in addition to unreacted compound Or rormula III and polymerised compounds derived from ~ormula II~ the ~eaction product Or the procesQ heroinbefore describcd oontains a compound of the rormulQ I ag hor~lnberore def ined .
The excellent activity Or the compounds of formula I, and Or reaction products containin~ compounds o~ formula I
produoed according to the process describcd h¢reinberore, a~
inhibitors ~or the deposition of the saltQ as hercinbeforc dorlned, from aqueous solutions wa-Q demonstrated by compara~ive testillg againYt both conmlercial products, and polymeri~cd acrylic .. . .. . . . . . .. ... . . . . .
acid produced by treating a compound of formula II R"_H, with a peroxide in the absence of a compow~d of formula III.
Tho amount of the inhibitor product comprising a compound Or formula I to be used in the method accordin~

. ;. . - , .
~t , ., , ,, ~- , ~ - 8 --10~3~53 to the invention is rom 1 part per million up to 200 parts per million and may be for example from 2 to 20 parts per million. The minimum amount of inhibitor required depends upon the concentration of the salts in the water to be treated.
The inhibitor composition used according to the method of the invention may be incorporated into the aqueous system to be treated in con-junction with other compounds known to be useful in water treatment.
Dispersing and/or threshold agents may be used, such as for example polymerised acrylic acid and its salts, hydrolysed polyacrylonitrile, polymerised methacrylic acid and its salts, polyacrylamide and co-polymers thereof from acrylic and methacrylic acids, lignin sulphonic acid and its salts, tannin naphthalene sulphonic acid/formaldehyde condensation products, starch and its derivatives, and cellulose. Specific threshold agents such as for exsmple, hydrolysed polymaleic anhydride and its salts, alkyl phos-phonic aclds, l-aminoalkyl, l,l-diphosphonic acids and their sslts and alkali metal phosphates, may also be used.
The inhibitor composition of the present invention may also be used in combination with precipitating agents such as alkali metal orthophos-phates, carbonates and hydroxides, oxygen scavengers such as alkali metal sulphites and hydrazine, and sequestering agents such as nitrilotriacetic acid and their salts and ethylene diamine tetraacetic acid and its salts, They msy also be used in conjunction with corrosion inhibitors such as cyclo-hexylamine, morpholine, distearylamine/ethylene oxide condensation products, stearylamine, and also in conjunction with antifoaming agents such as di-stearylsebacamide, ( lV~ 3 distcaryl adil~altli~e and rcla'~cd products dcrived frolll ethyl~lle oxidc condcllsations, in.a~di.tion to fatt~ alcohols, such as capryl alcohol* and t~eir ethylene oxide . cond~nsatos.

i The follo~ing Examplcs further illustrate the present invcntion. Parts and pcrccntagcs shown therein are by weigllt unlcss othe~ise stated.
In Examples A - D the reaction solvent was 1,4-dioxan and the reaction initiator benzoyl peroxide. I~ypopllosphorous acid was used throughout as a 50~o aqueous solution and parts of hypopho~phorous acid refers to parts of that 50~ nqueous eolution.

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E'xamnle A

I Treatment Or acrylic acid with hypopl-osphoro-ls acid in a 2 :1 molar proportion.
Acrylic acid ( 4ll parts) and hypophospllorous acid ( 40 parts) were discolved in dio~an ( 130 }?arts) by stirrin~.
~enzoyl pcroxidc containing 25~' water ( 2.5 parts) was addcd and the mixture hcated at a reflux for 24 hours. The solution was thon evaporated under reduced pressure, the final traces of water being removed at 100/0.1 mm. The residue was dissolved in methanol ( 60 part~) and reprecipitated by thc ~ddition of ether. This precipitation procedure was repeated twice further to yield a ~iscous residue. Traces of solven~
w~re remo~ed by evaporation at 100/0.1 mm to yield a white glassy soli~.
The product had a mean molecular weight of approximately 600 ( vapour prossure osmometry using methanol solution) and a phosphorus content of 5.2%. Thi8 indlcated that it containe~
an nvera~o of ~bout 7 moles of acrylic acid per molc of hypophos-phorous acid.
The 3 P n,m.r. spectrum ~a-4 obtained u ing Fourier Transfor~
analysis. ~he speçtrum contained ( inter alia) si~nals at the ~ollowing chemical shifts using H3P04 standard.

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' - 11 - .
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. ~ ' ' ' ' ' ' . ' ' . . , ' ' ' , ' Chcrr~ t ~1u].ti.~)1icity Asis:i~nl!lent p,p,lll.
+ 4.1 - 9.9 Trlplet Hypopllosphorous _24.1 Acid _15.7 39 5 ~ Doublet Compo~ld~ of formula I
.! n =
Rl. 01~
-50.2 Singlet Compounds o~ formula I

R ~l-l .
Rl = Il ., , _, ". .

... . _ xamnl~ B
Trcatment o~ acrylic acid with hypophosphorous acid in R 7:1 molar proporticn.
5 Acrylic acid ( 40 parts), hypophosphorous acid ( 10.5 parts) ben~oyl peroxid~ containing 25% water ( 2.5 parts) and water ( 13 parts) worc dlssolved in dloxan ( 130 parts) by stirrin~.
Hea~efl at rerlux ~or 24 hours, evaporatéd undcr reduccd proesurc, the rinal traces of solvent being romoved at 100-/0.1~m, The prod~ct was obtained as a white gla~sy solid, xam~l o C
, Treatmcnt o~ acrylic acid wI~h hypophosphorou4 acid in 14sl molar proportion.

-; ~xample B was repeated using hypophosphorous acid (5,3 parts) and water ( 16 parts). The product was obtained as a whlte glassy solid.
, ..... .... ~ --v .

, _ ,12- ' . ~ .

.-- ~.0~ ;53.
Colnp;~rflt i ~ e ~x~
Treatll~cnt oI acrylic acid Wit~l ~en~oyl pero~ide ln the absence of hypo~ o~phorous acid.
Examplc B was repeated in the abscnce of hypophospllorous acid using water ( 18 parts). The product was obtained as a white glassy s~lid.
Example D
..
Treatmcnt o~ acrylic acid with hypophospllorous acid in a 7: 1 molar proportion using water as solvent.
A suspcnsion of hypophospllorou~ acid ( 262 parts), acrylic aoid (100 parts), ben~oyl peroxide containing 25~' water ( 10 parts) and water (800 parts)-was stirrcd and heated cautiously to 95-98~. ~t this temperature an exothermic rcaction occurred causing the sy~tem to reflux. Extornal heating t~JaS removed.
. ~C 5y8tenl WAS maintained at reflux by gradual addition of Acrylic acid ( 900 parts) over 45 minutcs. Arter the addition w~ complcte and ~he exothermic reaction had ~u~sidcd the ~ixtllro wa# stirred at 95-10~ for 3 hours. After this poriod thc mix~ure wa~ allowed to cool A shmple was tcsted Wit]l ~cidified potassium iodide and Rtarch solution in order to chcck that peroxide did not rcmain. The product wa~ obtained a viscous solutlon.
~xalnPle E
A ~amplo ( 50 parts) of the solution from ~xample D was ovQ~poratcd under reduced pre~9ure as in Example A. The dried product was obtained as a white glassy solid ( 27. 5 part~).

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;

.
la4~s3 13xnmp 1 e E~` -Treatmcnt of acry]ic acid wlth n-octyl phosphinic ncid in a 5:1 molar proportion.
Acrylic acid ( 10 parts), n-octyl phosphinic acid ( 5 part~) and bcnzoyl peroxide containing 25~,b water (0.5 parts) wcre treated as in Example ~. After evaporation Or the rcaction solvent the residuc was dissolved in water and washed with ether. The ether phase was discarded.
The aquaous pha~c was evaporated under reduced pres~ure tho final traces of sol~ent bein~ removed at 100-/0.1 mm.
The product was obtained as a white ~lassy solid which had a phosphorus content of 0.7%. This indicated that it contained an average of about 60 moles Or acrylic acid pcr mole Or n-octyl phosphinic acid.
Exam~le G ~, Treatment of acrylic acid with diethylp~osphite in a 1~2 molar proportion.
A solution Or benzoyl peroxide ( 70% in dlmethyl phthalatc 0.26 p~rt3) in diethylphosphite ( 13.8 parts) was addcd to a ~olution o~ acrylic acid ( 18 parts) in diethyl phosphitc ( 55.2 parts). The mixturc was heatcd to 90- to i,nitiate the exothermic reaction whlch caused the temperature to rise to 130-. The mixture was cooled to 90- and maintained at this temp~aturo ~or 3 ho'urs. The excess diethyl pho6pbite , , was rcn~oved by,vacuum distillation and the residue dissolved ln mothanol. Telomer was obtaincd by precipitation in dlethyl ether and dried under vacuum at 50-C. It had a phosphorus content of ~ ok which illdicatcd that it containcd ~: ' ' ' , , "'' t~ 3~iS3 an aver~e o~ aboui 36 molcs of acrylic acid per 1 molc o~

dlethyl pho~p~lite.
X~ltlp~
Treatlnent of acrylic acid with orthophosphorous acid in a 7:1 molar proportion.
To a solution of 5.85g( 1/14th mole)orthophosphorous acid and 3.6 g potassium persulphate in 100 g water at 75-C were added 36 g(~ mole) acrylic acid over a period of 30 minutes. The reaction mixture was heated to 85-C
and maintained at this temperature for 3 hrs.
A ~ample of the telomer was isolated by evaporating the solution to drynes~. The polymeric residue waq dissolved in methanol and the solution filtered in order to remove traces of inorganic material. The telomer was ~eprecipitated by addition of the solution to an eXcecs o~ diethyl ether. The telomer was found to have a phosphorus con"t,ent of 1.43/0 which indicated that it contained an average o~ 29 moles of acrylic acid per 1 mole of ortho-phosphorous acid.
Exam~le I
Treatment of acrylic acid with orthophosphorous acid in a 2:1 molar proportion.
To a solution of 20.5g (l/4 mole) orthophosphorous acid and 3.6 g potassium persulphate at 75-C were added 36g(~ mole) ~crylic acid over a period of 30 minutes. The reaction mixtur~ was heated to 85-C and maintained at this temperature ~ox 3 hours.
A sample of the telomer was isolated by evaporating the ~olubion to dryness. The polymerlc résidue was dissolved ...

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1043~3 in m~thclnol an~ the solution filtered ~o rernove traces of inorganic material The telomer was reprecipitated by addition of the ~olution to an excess of diethyl ether.
The telomer was found to have a phosphorus content of 3.~7~' which indicated that it contained an average of 11 moles acrylic acid per 1 mole orthophosphorous acid.
Example J
Treatment of acrylic acid with phenylphosphinic acid in 7:1 molar proportion.
5,6g of phenylphosphinic acid were dissolved in 50 mls. of dioxan and 20g. of redistilled acrylic acid were added, followed by 5 mls. of water and 1.5 g of benzoyl peroxide The reaction mixture was qtirred under reflux condition~ for 24 hours, then evaporated to drynees and dried under high vacuum over sodium hydroxide at 100-C. In thi~ way, 23 g. of a white glassy solid were obtained.
Exam~le K
Treatment of acrylic acid with butyl hypophosphite in 7:1 molar proportion.
4,9 g of butyl hypopho~phite was dis-qolved in dioxan . .
and 20g. of acrylic acid were added. 1.3g. o~ dry benzoyl peroxide were added and the whole wa~ heated gently at 100-C, under an atmosphere of nitrogen. The reaction mixture wa~ then evaporated to dryne~ and dried under high vacuum over ~odium hydroxide at 100-C. to leave 21g. o~ a white gla~sy ~olid.

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f;~.~lllp~.CS 1 1;G 1 1 _ .
~queous ~sollltions ol' C~a(N03)2.4ll20(6.69/ol~r/w; 100 ml) And 2~,rS0l~ ~ 7~-120 (~; ~ 99~ ~t/w; 100 ml ) wcre ni~;ed to provi.de a ten fold supor~aturated coluti.on Or Ca~iO4 . 21120. ~n amount of an aqUeous solutioll containi.ng 1000 p.p.m.
of one of the products rrom l~a~ les A-_ K ~as addcd in order to provide an additive concentra l;ion Or 10 or 5 p .p.m. in thc- test solution. The solution ~;as stirred anc3 .~llo~fcd to stand at room temporaturc. After ~0 hours a sc.mple of the test solution Wai3 withd~; awn :-nd tlle conce~ rat-iion Or calcium ions rcma:Lni.n~ in solutlon was determi.ned by t-iitration with l~.D.T.~. The test; datia l ore recordocl by exprcssin~
the calcium ion concentrati.on prescnt in solut3.0n at 90 hours as ~ pcrcent:~ge Or the calciwn ion concontratioll presont in solution at thc start of the test. Tho te3t data are recorded in Table I whlch also contain~ thc results of oomparat:i.vc trials u~lng known ~dditives, It can 1)e secn rrom Table I that: tho solut:ionq to whlch oompoun~ls o~ ~ormula I~ or reaction px oducts containin6r ¢ompounds of formula I had been added, retained a groater proportion of` the s (;artin6 calci.um ion contcnt in solution .. . ..
At 90 hour.s, than didthc blanlc solution or than dld tihe test solutions containinfr poJ.ymerised ~crylic acid or Icnown commerc:ial produo t 0 .

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10~653 ( TAB1,E I

Ex~m~)le ,~dditlvc ~ddi.tive Concentr~tion iu 501U i on . . after 90 ~r~
_ :
~lank Nil 26 Exnmple 1 Produot rrom 10 100 Example ~ 5 Examplc 2 Product rrom 10 100 . Example Example 3 Product rrom 10 839 Example C 5 Example 4 Product from 10 100 . Example D 5 Examplc 5 Product from 10 100 Example E 5 Example 6 Product from 10 45 Example F 5 Examplo 7 Product from 10 42 Exa3ple G 5 . , Example 8 EXBmp10 H 10 36 4 Example 9 Product rrom , 10 37 1 EXB~P10 I 5 . . .

Example 10 Examplo J 105 40 6 Examplo 11 Product from ~ 10 92.7 _Exam~lc 1C S 9.
. ~olymeri~ed acrylic 10 35 scid. Produrt from .
. Comparative Exa~ple C 5 3 . Sodlum hexameta- 10 3 pho~phate ' 5 Bodlum 1.0 31 trlpolyphosphate Hydroxymethane 10 28 Comparati~o 1~1-diphosphonic acid .
. Exsmples Commorcial polyacrylic 10 50 . aold molocular ~oi~ht 5 31 ' 10~000 . :.

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10~ 53 i ~
~ 1 a9~1eOI.I5 801uti.0n ( 1 n~l) contai.ll:i.n~,r 1000 p.p.m.
of one of the produc1;s from Exa1llp].c ~ 3, or G to K was mixcd with an ~queous solution of Ca(N03)2.4!)zO
(206~./1. ;50 ml) . An aqucous solution of ~1a2SO11(17g/l. ;50 ml) was added and the resulting solution heat-ed to 90 over 10 m:lnutes and the optic~l density of tlle solution continuously monitored and recorded using an Auto Analyser.
From the plot of opt~cal dcnsity a~ainst time the initiatiorl time and the rate of preci~itation were dctGrmined.
The initiatioll time is de~ined as the timc after mix:lng t~le two solutions at which precipitation occurs ( as ~udged ~y .. e.n increase in optical density), and the rate of pr~cipi.ta1;i~n 1~ derined as the maximum positive slope of the plot o~
optioal densit)~ a6ainst time, In the latter determinatior any rapld short-term increase~ from the ba~o line Or less than 15~ of the opti-ea~ donsity Or the rully precip;.tiat~d blanlc solution wcro disrc6ardcd.
It can be ~een from Ta-~le II that the initiation time for CaS04 precipitation for compcunds of foxmula I and the reaction products containin6 compound.s of rormul,l X 1~
~reater than the initiation timcs ror the blanlc, polymbri~sed ao~ylic acid and known conunercial product~. In addition , the compounds of rormula I and the rcaction products conts.~.n:Ln~
oompounds o~ f'ormula I, have the advantagc of affordin~ lower ratcs of precipitation of' CaS04 compared with the blanl~ and tho othcr Exampie in Tablo II, .
._ .
.~

~ _19: _ 'I ' , .

, ; TAI3LI: II 1 "3 ~ 53 ., xamrtle ~!\dditi~re Additive Lnitia- Rate of ¦ ~_ concen- t10n p ec _ I Precipi.tat7on trati.on ~ime it~ion 15 min 3 _ _ _ _ ~.P.~I. M~n~s _ ~lank Nil 3 >30 ¦ 100 ¦ ~
~ _ .
Example 12 Product from 10 13 11 10 100 . Example A .
Example 13 Product from 10 12 6 15 100 Exam~le ~ .
Example 14 Product from 10 13 5.5 6 100 Example G .
Exa~ple 15 Product from 10 8 1.2 8 100 Examplc ~ _~
Example 16 Product from 10 8.5 2.6 15 100 Example I
. . .~-. . ~ .

~xample 17 Product from 10 10 0.9 6 100 Example J
~xample Product from 10 12 2.3 9 ' 100 . Example K . .
Polymeri~ed acryllc acid 10 8 >3 100 Product from Comparati-~e Example C
Compara- Sodium trl-tl~o polyphosphate 10 5 >3 100 _ ~xample~
Hydroxymethano ; . . .. , 1,1-dlphos- 10 3 ~>3 100 phonlc acid . .
. Commercial poly acrylic acid 10 8 >3 100 Molecular weieh 10~000 .
. l . ~ -.

:~:: .:
i:: . : . .

:" ' ' ' '.~ '' ' ~' ~,' ".' ., '` ' . ' ' ' '' , " ' . . ' ., . .': " ' .' " ' ' ~ ., ' ' ' ' " ` . - ' . ' ': ' -~' :'.'' ' . ' '''' i."` ' , ' . ' '.' . .. ~, , : ' ' ' ~0~3~3 ~ ,]~; 19 to 21 _ J ~ __ _ _ ~ n aqucous solution ( 2 nll) contairli.n~ 1000 ppm Or one of tlle products I'ronl ~xamplos ~ - ~ W.lS mixed with an aqueous solution of C~(~03)2.4I120 (1~ll76/l.; 100 ml).
An aquoous ~olution Or Na2C0 ( o.646~r/1.; 100 ml) was add~d and the resulti~ olution heated to 95 over 7 minutes,and thc optical density of the solution csntinuously monitored and recorded usin~ an ~uto Analyser. The initiation timc and rate of precipitation were deterlllined in a manner similar to that described in Exampl~ 13 to 20.
It can bc seen from Table III that the initlation timc for CaC03 precipitation for colnpounds of forn;ula I
and reaction products containin~ compounds of formula I are grcater than those ror the blanlc, polymerised acrylic acid and known commercial products. In addit.ion the compounds o~ ~ormula I and the reaction p~oducts containing compounds Or ~orltlula I,have thc advanta~e of arrordin~ lowcr ratcs o~
preclpitation o~ CaC03 coJnparod with thé bla~c and thc other ~xamples in Ta~l~ III. .

. .

_21, _ , .. .. . .. ... . . . .. . . . . . . . . . .

,~',' : ' . :
, , . - . .. .
. : , , ~ ..... . . : , - -: ' .. ' '' ' , , ~ ' . ' , ~ . . . . ~ - ,, : .
:. , . . .. - . . , . .. -, : .: . -, . i04365 ;____ T~1 ~E lTI
J~,xnmplc Additivo ~ ~d~itiv~ I~tlation rT ecipitati.on .
. . onccn- Ti.me 15.min 30 min. ~5 mi~
rat~on (minute~) (p.p.m) . -.
_ _ ¦ Bla~c j nil¦ 1 l100 _ L .
~amplc 19 Product from 10 8 20 100 ¦Examplc D . . ~ :
Exmnplo 20 Product from 10 7 20 36 100 ¦Example E .
Fxamplc ~1lProduct rrom 10 7 32 64 100 Examplo F _ Comparat- . . .

. r~ mple~ phato 10 2 100 _ . ~ . Hydroxy mcthanc 10 3 100 _ l~l-di~ho~ph- .
, . nlo acld. . . .
ol~norcial 10 1 . 98 100 . ~lyacryllc acl . .
~oloculur w~lGh 0~000 ' .
. , . ... . .. _ . . ~ .-- . ,.-: . . _ .
. Polym-ri3cd . ' . acryllc aoid ~ .
. Produc t rro~ 1 o 2 ~ 80 1 oo . Comparativ~ .
~=D:~=~ , ~ mpl~ C_ ~ ., _ _ .... .. __ ,,, , . . _ ~ . :
, .. .. . ~ .
, ~ 22 -;~ ' ' .
- t.,s .. ,_ . ... , , , . , .. , ~ .. " ,, . j , . . ~ . .... .. . . . .

, , .,: , ,: . . :- . .. -, , . ~, . . ::. : . : , _xi3IIlp]e22 1043~S3 ~ :
Solu~io~l~ Or ~Ig~NrO3)2~II20 (6.56/1;21) and NaIIC0~(4.0 g/l.; 21) were preparod. The product from Exi~mple ~ was added to thc solution of magncsium nitratc in an amount ~hat attainod the requircd te~t concentratlon.
I~e solutions were mixed ~nd a ~amplo ( 21.) with~rawn for te~ting. The remai~inV solution was retained for addition to the test solution durin~ the experiment.
A weighed mild steel sheathcontaining a 1~ cartrid~e hoater was immorPed in the 2 litre ~ample of ~olution causin~
boiline at thc metal ~furrace. Ihe bulk of t~le test solution wa~ maintained below its boiling point using a copper coolin3 coil.
The expor~ment was continucd for 5 houri~ and during this tlme tho reolaining test solution was addcd. At the ond o~
the expcriment the tei3t i~olution had been ~oncentratcd 1.7 tlme~ . , A~tor tho ~ hour exporimcnt pexiod~the conccntration of ma6no~ium 50n~ in the solution, thc weight of scale on the heater sheath, and the jcale thickness were dete~nined, Tho results in Tablc IV demollstrate the ef~icicncy with which the compcwlds o~ ~ormula I inhibit tho precipitation Or ~1¢(0II)2 from aqueous solution~. The conccntra~ion of ma6no~1uID ions in the final solution are higher,and the wei~llti and thic~ne~is Or the i~cale on thc sheath ~ro lowor~
~rom the test sfolutiion containing the compound of formula I
tllan the r0spe_tivo valuesi obtained from both ~he ~lank run andthe te~it run on coIim~ercial polyacrylic acid.

.,

3-.

."'`J . 1(~43653 'rADL~: IV .
.

F,xanl~le Addltive Additiv~ ~ei~t of ~hickness ~ t concentra- -. concen- Scale of Scale tiOII in the p.p m. e Inch 3p.p.m.

~lnnlc nil 2.1 20 150 Fxalr.pl~ 22 Product Or 10 0.75 4 - 5 371 . Examplc ~

Comparativ Commcrcial .
Examplc polyacrylic acid. 10 1.8 11 - 15 l9G
Uolccular .
. 10,000 .

m. results ln ~ables I~ II, ~I and IV clearly den~onJ~rate the cood stnbility lmparted to a~ueou3 solutions Or calcium 3ulphate, o-loium carbonAto, and n~Gnesium hydroxide by the compoundis o~
ormul~ I and by rsaction product~ contalnin6 compounds Or ~ormula I.

.

-~: 24 _ ; ~

.

~ ' .

Claims (9)

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

1. A method of inhibiting the precipitation of the scale forming salts of calcium, magnesium, barium and strontium from aqueous systems com-prising adding to the aqueous system from 1 to 200 parts per million of a product comprising a telomeric compound of the formula:

I

or salts thereof, wherein R11 is hydrogen or a methyl or ethyl residue, R is hydrogen, a straight or branched alkyl residue having from 1 to 18 carbon atoms, a cycloalkyl residue having from 5 to 12 carbon atoms, an aryl residue, an aralkyl residue, a residue of formula:

wherein R11 has its previous significance, and the sum of n + m is an integer of at most 100, or a residue -OX wherein X is hydrogen or a straight or branched alkyl residue having from 1 to 4 carbon atoms, and R1 is a residue -OX wherein X has its previous significance.

2. The method of claim 1 wherein R11 is hydrogen.

3. The method of claim 1 wherein the sum of n and m is an integer less than 60.

4. The method of claim 1 wherein R is hydrogen, a straight or branched chain alkyl residue having from 1 to 10 carbon atoms, a cyclohexyl residue, a phenyl or benzyl residue or a residue -OX wherein X is hydrogen or a straight or branched alkyl residue having from 1 to 4 carbon atoms.

5. The method of claim 1 wherein R1 is OH, and R is a residue of formula wherein R11 is hydrogen and the sum of n and m is an integer within the range of from 5 to 20.

6. The method of claim 1 wherein R and R1 are each OH, R11 is hydrogen and the sum of n and m is an integer within the range of from 5 to 30.

7. The method of claim 1 wherein R and R1 are each a residue -OX
wherein X is an alkyl residue of from 1 to 4 carbon atoms, R11 is hydrogen and the sum of n and m is an integer within the range of from 5 to 30.

8. The method of claim 1 wherein there is used a proportion of the inhibitor composition within the range of from 2 to 20 parts per million.

9. The method of claim 1 wherein the inhibitor composition is used in conjunction with a dispersing and/or threshold agent, a precipitating agent, an oxygen scavenger, a sequestering agent, a corrosion inhibitor or an anti-foaming agent.