Note: Descriptions are shown in the official language in which they were submitted.
Il 1 329474
FIELD OF INVENTION
This inVention is related to a composition
and method ~or inhibiting corrosion in
industrial cooling waters which contain hardness and have a pH of
at least 8, which composition comprises a water-soluble organic
phosphonate capable of inhibiting corrosion in an aqueous
alkaline environment and a co- or terpolymer of acrylic aci5 and
certain substituted acrylamides such as t-butyl acrylamide.
The term "phosphonate" refers to organic materials
containing one or more -PO3H2 groups and salts thereof.
Phosphonates particularly useful in this invention include
l-hydroxy-l,l-ethane diphosphonic acid (HEDP),
2-phosphonobutane-1,2,4-tricarboxylic acid (PBTC),
amino-tris-methylenephosphonic acid (AMP), and their salts. The
concentrations and dosage levels and/or ranges of polymers,
phosphonates and compositions are listed as actives.
INTRûDUCTION
Corrosion occurs when metals are oxidized to their
respective ions and/or insoluble salts. For example, corrosion of
metallic iron can involve conversion to soluble iron in a +2 or
+3 oxidation state or insoluble iron oxides and hydroxi~es. Also,
corrosion has a dual nature in that a portion of the metal
surface is removed, while the formation of insoluble salts
contributes to the buildup of deposits. Losses of metal cause
deterioration of the structural integrity of the system.
Eventually leakage can occur, through areas subject to corrosive
deterioration, for example between a water system and a process
stre
. . ~ . ~
- 2 - ~
:~
: ~ :
1 3 2 9 4 7 4
Corrosion of iron in oxygenated waters is known to occur ¦
by the following coupled electrochemical processes:
(1) ~e -~~ Fe+2 2e~ (Anodic Reaction)
(2) 2 ~ 2e --~ 2ûH (Cathodic Reaction)
Inhibition of metal corrosion by oxygenated waters
typically involves the formation of protective barriers on the
metal surface. These barriers prevent oxygen from reaohing the
metal surface and causing metal oxidation. In order to function
as a corrosion inhibitor, a chemical additive must facilitate
this process such that an oxygen-impermeable barrier is formed
and maintained. This can be done by interaction with either the
cathodic or anodic half-cell reaction.
Inhibitors can interact with the anodic reaction 1 by
causing the resultant Fe+2 to form an impermeable barrier,
stifling further corrosion. This can be accomplished by including
in~redients in the inhibitor compound which: react directly wlth
Fe+2 causing it to precipitate; facilitate the oxidation of
Fe+2 to Fe+3, as Fe 3 compounds are typicaIly less soluble;
or promote the formation of insoluble Fe+3 compounds.
The reduction of oxygen at corrosion cathodes provides
another means by which inhibitors can act. Reaction 2 represents
the half-cell in which oxygen is reduced during the corrosion
process. The ~rc~uct of this reaction is the hydroxyl (OH )
ion. Because of ~ydroxyl production, the PH at the surface of
metals undergoi ~ oxygen-mediated corroiion is generally much
higher than that of the surrounding medium. ~any compounds are
less soluble at elevated pH's. These compounds can precipitate
at corrosion cathodes and act as effective inhibitors of
corrosion if their precipitated form is impervious to oxygen and
is ele lca11y noncon~uctive.
Corrosion inhibitors func'.lion ~y creating an environment
in which the corrosion process induces inhibitive reactions on
the metal surface. In order for an inhibitor composition to
function effectively, the components of the composition must not
precipitate under the conditions in the bulk medium. Inhibitors
which effectively inhibit this precipitation by kinetic
inhibition have been extensively described in the literature. An
example of this art is U.S. patent 3,88û,765 which teaches the
use of polymers for prevencion of calcium carbonate precipitation.
The use of inorganic phosphates and phosphonates in
conjunction with a threshold inhibitor in order to control
corrosion by oxygenated waters is describeb by U.S. patent
4,303,568. This method is further elaborated by U.S. patent
4,443,340 which teaches that a composition comprised o~ only
inorganic phosphates and a polymeric inhibitor perforns well in
the presence of dissolved iron.
Corrosion inhibition can be achieved by a combination of
the use of inhibitors and modification of the chemistry of the
medium. U.S. patent 4,547,540 teaches a method of corrosion
inhibition relying on operation under conditions of high pH anc
alkalinity. This method does not rely on the use of inorganic , ;
phosphates, givlng a more desirable product from an environmental
impact point of view.
The current invention describes phosphonate corrosion
inhibiting compounds, containing a unique series of polymers,
phosphonates and to which may optionally be added aromatic
azoles. The use of these polymers results in signi-ficantly
improved corrosion inhibitor performance. -~
The use of the copolymers of this invention ac scale
inhibitors is discussed in U.S. Patent No 4,~66,973. In general,
1 3 2 9 4 7 4 66530-434
these compounds are copolymers containing t-butyl acrylamide
unlts ln conjunctlon wlth other comonomers. We have found that
these compounds are effectlve calcium phosphonate lnhibltors
and that they functlon effectlvely as cornponents ln a
phosphonate containing corroslon lnhlbitor compound.
According to one aspect of the present lnventlon
there ls provlded a composltlon for lnhlbltlng corroslon ln
lndustrlal coollng waters whlch contaln hardness and have a pH
of at least 8 whlch composltlon comprlses: I. e phosphonate
blend of 2-phosphonobutane-1,2,4-trlcarboxyllc acld and 1
hydroxy-ethylldene-l, l-diphosphonlc acid, and II. a water-
soluble non-crossllnked random terpolymer of 40 to 90 welght
parts of an acryllc acld, 5 to 30 welght parts of methacrylic
acld, and 5 to 50 welght parts of a t-butylacrylamlde, besed on
a total of 100 welght parts of polymer, sald polymer havlng a
weight average molecular weight in the range of about 1,000 to
50,000, and the polymerlzed unlts of an acryllc acld and a
t-butyl acrylamlde are deflned by the followlng formula:
R Rl
~CH2 f~ ~CH2 ~~n / R
O = C - OX O = N -
\ R3
where m i8 ln the range of about 10-700 and n ls ln the range
of about 0~1 to 350, sub~ec$ to the molecular welght
llmltatlons; R and Rl are lndivldually selected from hydrogen
and methyl; X ls selected from hydrogen, sodlum, potasslum,
calclum, ammonlum and magneslum moletles; and R~ and R3 are --
indlvldually selected from hydrogen, and substituted and
unsub~tltuted groups each contalnlng a total of 1 to 8 carbon
~ 32q474
66530 434
atoms, whereln the substltuents on R2 3
and/or R are selected
from alkyl, aryl, and keto groups, provlded that elther R2
and/or R3 ls t-butyl, wlth the welght ratlo of polymer ,
phosphonate blend belng wlthln the range of 0.2/1 to 2/1.
The welght ratlo of II to I ls preferably 0.75/1.
The Pho~Phonates
Generally any water-soluble phosphonate may be used
that ls capable of providlng corroslon lnhlbitlon ln alkallne
systems; for example U.S. 4,303,568 list~ a number of
representatlve phosphonates.
The Orqano-PhosPhonlc Acld Derlvatlves~:~
Organo-pho~phonlc acld compounds are those havlng a
carbon to phosphoru~ bond, l.e.,
- C I - OM
OM ~
Such compounds generally are lncluded ln one of ~ ;
perhaps 3 categories whlch are respectlvely expressed by the
followlng ~eneral formulas:
R - P - OM -;
OM
1 329474
where R is lower alkyl havins from about one to six carbon atoms,
e.g., methyl, ethyl, butyl, propyl, isopropyl, pentyl, isopentyl
and hexyl; substituted lower alkyl of from one to six carbon
atoms, e.g., hydroxyl and amino-substituted alkyls; a mononuclear
aromatic (aryl) radical, e.g., phenyl, benzene, etc., as a
substituted mononuclear aromatic compound, e.g., hydroxyl, amino,
lower alkyl subsitituted aromatic, e.g., benzyl phosphonic acid;
and M is a water-soluble cation, e.g., sodium, potassium,
ammonium, lithium, etc. or hydrogen.
Specific examples of compounds which are encompassed by
this formula include:
methylphosphonic acid
CH3P03H2
ethylphosphonic acid
CH3CH2Po3H2
2-hydroxyethylphosphonic acid
CH2-CH2-P03H2
2-amino-ethylphosphonic acid
CH2-CH2-P3H2
NH2
isopropylphosphonic acid
CH3
CH3-CH-cH2-po3 2
benzene phosohonic acid
C6H5-P03H2
benzylphosphonic acid
C 5CH2~o3 Z
_ 7 -
o o 1 32~474
11 11
B ~ MO---P--R ~ P--OM I .
OM OM
wherein Rl is an alkylene having from about one to about 1~
ci~rbon atoms or a substituted alkylene having ~rom about 1 to -
abûut 12 carbon atoms, e.g., hydroxyl, amino etc. substituted
alkylenes, and M is as earlier defined above.
Specific exemplary compounds and their respective
formulas which are encompassed by the above formula are as
follows:
methylene diphosphonic acid
H203P-cH2-pû3H2 1'
ethylidene diphosphonic acid
l H203P-CH(CH3 )P03H2 ~ I
isopropylidene diphosphonic acid
¦ (CH3)2C(Po3~2)2
l-hydroxy-l,l-ethane diphosphonic acid (HEDP)
¦ OH
l H203P-c(cH3)-po3H2
. l ' ~
¦ hexamethylene diphosphonic acid ~;
H2U3p-6~2(~H2)4cH2-po3H2
¦ trimethylene diphosphonic acid
l H203P-~H~)3-po3H2 ~ ~
decamethylene diphosphonic acid
H203P-(~-~2)~o P3H2
l-hydroxy, propylidene diphosphonic acid -~
~2o3pc(oH)cH2(cH3)pû3H2
.. .. . ... . ... . . . . . . .... . . . . . . . ... . . . . . .
1 329474
1,6-dihydroxy, 1,6-dimethyl, hexamethylene diphosphonic acid ,
H203PC(CH3)(0H)(CH2)4C(CH3)(0H)P03H2
dihydroxy, diethyl ethylene diphosphonic acid ,
H2o3pc(OH)(c2H5)c(OH)(c2H5)po3H2
R3
C . ~ R2--I--OM
where R2 is a lower alkylene having from about one to about
four carbon atoms, or an amine or hydroxy substituted lower
alkylene; R3 is [R2-PO3M2] H, OH, amino, substituted
amino, an alkyl having from one to six carbon atomsl a
substituted alkyl of from one to six carbon atoms ~e.g., OH,
NH2 substituted) a mononuclear aromatic radical and a
substituted mononuclear aromatic radical (e.g., OH t NH2 .
substitutedj; R4 is R3 or the group represented by the formula
N~R ~--~ OM
where R5 and R6 are each hydrogen, lower al~yl of from about
one to six carbon atoms, a substituted lower alkyl (e.g., OH,
NH2 substituted), hydrogen, hydroxyl, amino group, suostituted
amino group, a mononuclear aromatic radical, and a substituted
mononuclear aromatic radical (e.g., OH and amine substitutea); R
is R5, R6, or the group R2-PO3M2 (R2 is as defined
above); n is a number of from 1 through about 15; y is a num~er
of from about 1 through about 14; and M is as earlier defined.
Compounds or formulas therefore which can be considered
exemplary for the above formulas are as follows:
' ,
. ..... ., .. . . , . ~, .... . .. ,~, , .; . . . . .
1329474
nitrilo-tri(methylene phosphonic acid)
N(cH2po3H2)3
imino-di(methylene phosphonic acid)
NH(CH2P03H2)2
n-butyl-amino-di(methyl phosphonic acid)
C4H9N(CH2po3H2)2
decyl-amino-di(methyl phosphonic acid~
CloH21N(cH2Po3H2)2
trisodium-pentadecyl-amino-di-methyl phosphate
ClSH31N(CH2P03HNa) (CH2P03Na2)
n-butyl-amino-di(ethyl phosphonic acid)
C4HgN(CH2cH2Pû3H2)2
tetrasodium-n-butyl-amino-di(methyl phosphate)
C4H9N(CH2po3Na2)2
triammonium tetradecyl-amino-di(methyl phosphate)
C14H2gN(CH2P03(NH4)2)CH2P03HNH4
phenyl-amino-di(methyl phosphonic acid) -:~
C6H5N(~H2Po3H2)2
4-hydroxy-phenyl-amino-di(methyl phosphonic acid)
. Hoc6H4N(cH2po~H2)2
phenyl propyl amino-di(methyl phosphonic acid)
C6H5(CH2)3N(cH2Po3H2)2
. tetrasodium phenyl ethyl amino-di(methyl phosphonic acid)
C6H5(CH2)2N(CH2Po3Na2)2
ethylene diamine tetra(methyl phosphonic acid)
203PCH2)2N(CH2)2N(CH2P03H2)2
trimethylene diamine tetra(methyl phosphonic acid)
(H2o3pt~H2)2N( H2)3N(cH2po3H2)~
hepta me~hylene diamine tetra(methyl phosphonic acid)
¦ ~. (H2o3pcH2)2N(c~2)7N(cH2po3H2)2
1329474
decamethylene diamine tetra(methyl phosphonic acid)
(H2o3pcH2)2N(cH2) 1oN(cH2po3H~)2
tetradecamethylene diamine tetra(methyl phosphonic acid)
2 3 CH2)2N(CH2)l4N(cH2po3H2)2
ethylene diamine tri(methyl phosphonic acid)
( 2o3P~H2)2N(CH2)2NHCH2P03H2
ethylene diamine di(methyl phosphonic acid)
H203PCH2 ) 2NH (CH2 ) 2NHCH2P03H2
n-hexyl amine di(methyl phosphonic acid)
C6H13N(CH2Po3H2)2
diethylamine triamine Penta(methyl phosphonic acid)
(H203PcH2)2N(cH2)2N(cH2po3 2)
(CH2)2N(CH2Po3H2)2
ethanol amine di(methyl phosphonic acid)
HO(CH2)2N(cH2po3H2)2
n-hexyl-amino(isopropylidene phosphonic acid)methylphosphonic
acid
6 13N(C(cH3)2Po3H2)(cH2po3H2)
trihydroxy methyl, methyl amine di(methyl phosphonic acid
(HOCH2)3CN(cH2Po3H2)2
triethylene tetra amine hexa(methyl phosphonic acid)
2 3 2)2N(CH2)2N(CH2P03H2)(CH2)2N-
(cH2po3H2) ~CH2)2N(cH2Po3H2)2
monoethanol, diethylene triamine tri(methyl phosphonic acid
2CH2N(CH2P03H2) (CH2)2NH(CH2)2N-
(cH2po3H2)2
chloroethylene amine di(methyl phosphonic acid)
ClCH2CH2N( (CH2P(H)2)2
1 329474
66530-434
The above compounds are lncluded for lllustratlon
purposes and are not lntended to be a llstlng of compounds
wlthln the conflnes of the lnventlon.
However, as deflned above, the present inventlon :~
relates to a blend of
A. 2-phosphonobutane-1, 2; 4~trlcarboxyllc acld (PBTC~
and
B. l-hydroxyethane-l, l-dlphosphonlc acld (HEDP~
While lndl~Jldual phosphonates may be used ln
comblnatlon wlth polymer~s) it has now been found that better
results are obtained by uslng a blend of phosphonates A and B.
They are preferably comblned ln a welght ratlo of A:~ of from
.5/1-4/1 and are more preferably from .5/1-2/1 and most
preferably about .67/1.
In additlon to phosphonates, addltlves such as
tolyltrlazole may be utillzed. Tolyltrlazole ls effectlve ln
the reductlon of copper substrate corrosion.
The Water-~oluble Noncrossed Llnked
Random CoPolYmers
These polymers are descrlbed in detall ln U.S.
4,566,973, whereln they are descrlbed by the patentee as
follows:
The copolymers suitable hereln are random polymers
contalnlng polymerlzed unlts of an acryllc acld and substltuted
acrylamlde, represented by the followlng structural formula I:
Rl ~
-~CH - lt -~CH~ - C~ ~2
0 ~ C - OX O = C - N
\ R3
12
1 3 2 q 4 7 4 66530-434
whereln m and n are numbers ln the range of about 0.1 to 700,
wlth m belng in the range of about 10 to 700 and n ls ln the
range of about 0.1 to 350, sub~ect to molecular welght
limitations; R and Rl are lndivldually selected from hydrogen
and methyl; X ls hydrogen, alkall metal, alkaline earth metal,
or ammonium, partlcularly hydrogen, sodlum, potasslum, calcium,
ammonlum, and magneslum; and R and R3 are lndlvidually
selected from hydrogen, alkyl and substltuted alkyl ~roups each
contalnlng a total of 1 to 8 carbon atoms, provided that elther
R and/or R ls t-butyl. Substltuents on the R and R groups
include alkyl, aryl, and keto groups, however, ln a preferred
embodlment, R2 and ~ are lndlvldually selected from alkyl
groups of 1 to 8 carbon atoms and substltuted alkyl groups of 1
to 8 carbon atoms contalnlng a keto substltuent group.
Speclflc examples of R2 and R3 lnclude t-butyl, lsopropyl,
lsobutyl, methyl, 2-~2,4,4-trlmethylpentyl) and 2-(2-methyl-4-
o~opentyl).
Sultable acryllc aclds for purposes hereln are
generally deflned as monounsaturated monocarboxyllc aclds
contalning 3 to 4 carbon atoms. Speclflc examples of such
aclds lnclude acryllc and methacryllc aclds, wlth acryllc acld
belng preferred.
Other comonomers can be used wlth an acryllc acld and
a t-butyl acrylamlde provlded that such addltlonal comonomers
do not deleterlously affect the deslred properties. Examples
of ~uch comonomer~ lnclude acrylate and methacrylate esters,
acrylamlde and methacrylamlde, acrylonltrile, vlnyl esters,
~tc.
The acryllc acid unlts in the copolymer can be ln the
acld for~ or ln a nPutrallzed form where the hydrogen of the
~ 13
1 329~7~ ~
carboxyl group is replaced with an alkali metal, alkaline earth
metal, or an ammonium cation, depending on the neutralizing
medium. Generally, the copolymers can be neutralized with a
strong alkali, such as sodium hydroxide, in which instance, the
hydrogen or the carboxyl group of the acrylic acid units will be
replaced with sodium. With the use of an amine neutralizing
agent, the hydrogen will be replaced with an ammonium group.
Useful copolymers include copolymers that are unneutralized,
partially neutralized, and completely neutralized.
1~ Polymerization of the monomers results in an essentially
non-crosslinked random copolymer, the molecular weight of which
can be adjusted with a little trial and error. The copolymer is
preferably formed in a high yield ranging from about 50% to about
99% by weight of the comonomers.
The polymers of the type described above may be modified
by incorporating into their structure up to 30% by weight of a
termonomer which contains: a non-ionic or anionic polar group
from the group selected perferably consisting of amido, lower
alkyl ester, and maleic acid salt groups.
Examples o~ preferred monomers that may be polymerized
to form terpolymers are acrylamide, methyl, or ethyl acrylate,
maleic anhydride. Other polar monomers that may be used are, for
example, vinyl acetate, acrylonitrile, the various vinyl ketones,
vinyl ethers and the like. Illustrative of these monomers are
the compounds: vinyl pyrrolidone, methyl vinyl ether,
methacrylonitrile, allyl alcohol, methyl methacrylate,
beta-diethylaminoethyl methacrylate, vinyl trimethylacetate,
1 329474 66530-434
methyl lsobutyrate, cyclohexyl methacrylate, vlnyl laurate,
vlnyl stearate, N-vinyl imldes, N-vlnyl lactams, diethylene
glycol dimethacrylate, dlallylmaleate, allyl methacrylate,
dlallyl phthalate, diallyl adlpate, etc.
The polymers formed may have weight average molecular
welght in the range of about 1,000 to about 50,000, and prefer-
ably about 2,000 to about 30,000, more preferably 9,000 to
30,000, as determlned by aqueous gel permeatlon chromatography
uslng polys~yrene of known molecular weight as a reference
material.
The acld numbers of the copolymers formed, as deter-
mlned by a conventlonal tltratlon wlth KOH, may range from 310
to about 740, corresponding to a welght fractlon of from 40% to
about 95% by welght of monomer units having COOH groups. The
preferred polymers have more than 50% by welght of free car-
bo~yl groups and an acld number ln the range from about 390 to
about 700.
Preferred species are descrlbed ln Table A below as
Polymer Composltion Nos. 1-12.
. '
~ j~...
~ 32q474 ~ .
Table A
Polymer Materials
Polymer
Composition No. M.W. Composition (mol%)**
(9300) AA/ t-BAm (88: 12)
2 (12000) "
3 (17700) "
4 (25900) "
(8900) AA/EA/t-BAm (86: 8: 6)
_ _ _ _ _ _ -- -- -- .
6 (9400) AA/Am/t-BAm (84: 11:6)
.:
7 ( 8200) AA/MAA/ t-BAm (68 : 19 : 13) ::
8 (13300)~
9 (14300)* " ,
(15700)~
11 (15600) " :
12 (23000) 1l :
'~
Weight average molecular weight, i.e. M.W. or Mw.
* Aqueous Mw estimated from GPC value using the THF eluent.
** AA: Acrylic Acid
t-BAm: tert-butyl acrylamide
EA: ethyl acrylate
Am: Acrylamide
MAA: methacrylic ~cid
- 16 -
~ 3~q474 66530-4~4
Polymer Composltlon Nos. 1-4 are unneutrallzed
copolymers of acryllc acld and t-butylacrylamlde (t-~Am).
Polymer Composltlon No. 5, Polymer Compositlon No. 6, and
Polymer Composltlon Nos. 7-12 are terpolymers which respec-
tlvely contaln the addltlonal mer unlts of ethyl acrylate (EA),
acrylamlde (Am), and methacryllc acid (MAA).
A dlstlnctlve feature of all these polymers ls the t-
butylacrylamlde unlt. That sterlcally-hindered, hydrophoblc
alkylamlde group exhlblts excellent reslstance to hydrolysis
and the unlt appears to confer exceptlonal performanse charac-
terlstlcs upon polymers.
The copolymers composed of acrylic acld and t-butyl
acrylamlde contalns between 50 to 90~ by welght of acryllc acld
and from 10-50% by welght of t-butyl acrylamlde. Preferably
the acryllc acid ls present in a weight percent amount ranging
between 70-90 wlth the t-butyl acrylamlde belng present at
between 10-30. Most preferably the acryllc acld ls present ln
a weight percent amount ranglng between 80-90 with the t-butyl
acrylamide being present at between 10-20.
The terpolymers are wlthin the followlng welght per- -
cent composltion ranges:
a) acryllc acld 40-90 more preferably 40-80 and
most preferably 60-80
b) methacryllc acld 5-30 more preferably 10-30 and
most preferably 10-20
c) t-butyl acrylamlde 5-50 more preferably 10-30
and most preferably 10-20
Dosa~e
The aqueous system ls dosed based on actlve lngredl-
ents to provlde thereto on a welght basls from between 5-50ppm,
preferably 8 to 30ppm, more preferably 8 to 40ppm and most pre-
ferably 15-30ppm of Composltlons I and II prevlously descrlbed.
17
~ J
t ~
1 32~474
When the ccmpositions are first added it is beneficial if
they are dosed on the high side to control the corrosion and to
begin forming protective films. After a week or so the dosages
can be diminished until an optimum maintenance dosage is
established.
Systems Treated and pH
The systems treated are industrial recirculating and once
through cooling waters that either due to their natural make-up
or by pH adjustment have a pH of at least 80 Preferably the pH
of the systems are within the range of 8-9.5 and are most often
within the range of 8.5-9.2. These systems are characterized as
containing at least 10 ppm of calcium ion and are considered to
be corrosive to ferrous metals as well as non-ferrous with which
they come in contact.
Description of the PREFERRED Embodiment
The following example is a representative formulation used
in this program.
Example 1
To a glass or stainless steel container is added 14 grams of
softened water. With stirring, aqueous solutions of the
following materials were added consecutively:
7 grams of l-hydroxyethane-l,l-diphosphonic acid (60 wt%)
12 grams of 2-phosphonobutane-1,2,4-tricarboxylic acid
(50 wt %)
15.3 grams of acrylic acid/t-butylacrylamide copolymer (49
wt%).
The mixture was cooled in an ice-bath and then basified by
slow addition of approximately 22 grams of aqueous sodium
hydroxide ~50 wt%) to the vigorously stirred solutlon. During
the addition of base, the solutionls temperature was maintained
1 32q~74
¦below 130F. The pH was adjusted to 13 with 4.7 grams of a 50
weight Percent of a sodium tolyltriazole solutiQn. Finally,
sufficient softened water to produce 100 grams of product were
ad~ed. The cooling bath was removed and the solution stirred
until ambient temperature was reached.
Changes in the formulation are easily accommodated by simple
modification of the previously listed procedure. For example,
decreasing the amount of polymer and sodium hydroxide, followed
by increasing the final amount of water added, will produce a
formulation containing lower polymer actives. Alternatively, the
polymer and corrosion inhibitors may be fed separately.
EXPERIMENTAL PRûCEDURES
....,
In laboratory tests, hardness cations and M alkalinity are
expressed as CaCû3 or cycles of concentration. Fe'n is
listed as Fe, and inhibitors (monomeric and polymeric) are listed
as actives. In analyses of heat-exchanger deposits, all
components are listed as wt% of the chemical element or acid-form
of the compound.
Calcium Phosohonate Inhibition
A standard heated "beaker" test was employed for
evaluating perfor~ance of phosphonate inhibitors (Table B).
Calcium and inhibitor stock solutions from the calcium phosphate
inhibition test were used. In addition, stock solutions (lOOû
ppm actives) of Bayer PBS-AM and Dequest 2ûlû were prepared.
Dequest-2ûlû, made by the Monsanto Company, St. Louis, Missouri
is described as hydroxy ethylidene 1, l-diphosphonic acid (HEDP)
(CF. U.S. Patent No. 3,95~,168). PBS-AM is a trademark of Bayer
for 2-phosphonobutane-1,2,4-tricarboxylic acid. To begin the
test, distilled water, (400 mL) was added to the jacketed-beakers
maintained at 60+2C. The stock solutions were added to attain
36û ppm Ca+2, lû ppm inhibitor, 5.6 ppm Dequest and 8 ppm ~-
P85-AM in the final 50û mL test volume. Next, the pH was adjusted
to 9.2 usinQ aqueous sodium hydroxide.
- 19 - ~:
~rad ark
... . - . . - . - . . --: : . : , . , -
.
1 32q474 . .
The pH of the test samples was manually adjusted at 15
minute intervals during tne first hour and at 1 hour intervals,
subsequently. A four hour test duration was sufficient for these
precipitation reactions to stabilize. Finally, a portion of each
test solution was passed through cellulose acetate/nitrate
Millipore*filter (type HA, û.45 um). ~oth filtered and
unfiltered aliquots were spectrophotometrically analyzed for
total phosphate content. To study particle size effects, an
additional sample ~as passed through a û.lû um Millipore filter
(type VC). The % inhibition was determined by a following
formula:
[filtered - blank]
inhibition = X 100
[unfiltered - blank]
* Trade Mark
1 32~474
Table B
Calcium Phosphonate Inhlbition
10 ppm polymer actives
5.6 Dpm Deauest 2010 & 8 cpm Bayer PBS-AM (as actives)
360 ppm Ca (as CaC03)
140F / pH 9.2 ~ 4 hrs.
% Inhibition
Polymer ... filter size (um).............. ~ :
Oomp. No. (M-W- H20) 0-45 0.10
1 (9300) 8~ 26
_
(8900) 74 24
6 (9400~ 8 13
11 (15600) 98 5
_
Versa*TL-4 (19000) 95 26 :
* Trade Mark :~.
- 2 1 - :
132q474
In calcium phosphonate inhibition tests, polymer
performance versus precipitated particle size was examined and
¦the results are presented in Table B.
The calcium phosphonate "inhibition" process involves
¦minimizing particle growth. Maintaining scale particles at an
¦extremely small size and mass may ultimately prove to be a
pivotal factor in determining polymer performance. By using
¦ filters with mean pore sizes of 0.10 and û.45 um, differences in
¦polymer performance were readily observed. Polymer Composition
¦NO. 11 (MW = 15,600) produced the best overall performance, and
¦ was the only polymer which exhibited good inhibition when a 0.10
¦um filter was used. Versa TL-4 (the low molecular weight
¦copolymer of sulfonated styrene and maleic acid) and Polymer
¦Composition Nos. 1 and 5 exhibited very good inhibition (0.45 um
¦ filter), but performance decreased rapidly when the filter pore
¦size was reduced to 0.10 um. In particular, Polymer Composition
¦NO. 11 exhibited the best overall performance in both bench-top
¦and PCT tests.
¦Performance in Products -_PCT Tests
¦pilot cooling tower test procedure
The pilot cooling tower test is a dynamic test ~hich
simulates many features present in an industrial recirculating
cooling water system. The general test metnod is described in
the article "Small-Scale Short-Term Methods of Evaluating Cooiing
Water Treatments...Are They Worthwhile?", by D. T. Reed and R.
Nass, Minutes of the 36th Annual Meeting of the INTERNATIONAL
WArER CONFERENCE, Pittsburgh, Pennsylvania, November 4-6, 1975.
The general operating conditions are provided in Table C.
1 329474
Table C
Pilot Cooling Tower Operating Conditicns
Tube # ~t ~ (atu/ft2-hr)
8 MS/15,000 (top)
7 SS/15,000
6 ~S/12,400
Adm/5,000
4 MS/ 5,000
3 SS/12,400
2 Adm/12,400
1 SS/12,400 (bottom)
Make-up water: Synthetic #3**
Desired Cycles: 4
Basin Volume/Temp.~** 50L/125F :
Holdinq Time Index 24 hr.
Flow Rate 2 gpm
pH 9.2
Product - high level 200 ppm
" - maintenance 100 ppm
Test Duration 14 days
*MS = Mild Steel
Adm = Admiralty brass
SS - 306 Stainless steel
**Synthetic #3 contains total ion content of 90 ppm Ca~2,
50 ppm ~q~2, 90 pom Cl-, 50 DDm sulfate, 110 opm Na+,
and 110-120 ppm "M" alkalinity (as CaC03).
***Return water is 10F higher
- 23 -
1 329474
Polymer Composition Nos. 1, 3, 5, 6, 7 and 11, as descri~ed
in Table D, were prepared pursuant to Example 1 and were used to
directly replace VTL-4 in the high pH, standard formulation.
Long-term stability testing (120F./pH 13) of those formulations
made pursuant to the procedure of Example 1 but containing polymer
Composition Nos. 1, 6, or 11 revealed no hydrolysis of the polymer
occurred over a 3 month period. PCT deposit/corrosion rates are
summarized in Table D below:
l 3~9474
Table D
Heat Exchange Tube Results
Polymer
(ppm actives) Deposit (mg!day) Corrosion (mpy)
MS Adm SS MS AdmSS
Blank - No polymer * 148 8 -- 8.80.6 --
Polymer Composition No. 1(7.5) 72 10 42 2.8 0.45 0.0
Polymer Composition No. 3(7.5) 30 2 37 1.3 0.0 -0.1
Polymer Composition No. 5(7.5) 76 15 49 2.9 0.35 0.0
Polymer Composition No. 6(7.5) 101 26 72 3.1 0.20 0.1
Polymer Com,oosition No. 7(7.5) 57 10 94 1.3 0.05 0.0
Polymer Composition No. 11 (7.5) 21 3 15 1.3 0.25 0.1
Polymer Composition No. 11 (5) *~ 50 1 22 2.9 0.04 0.0
Versa TL-4 (7.5) 54 7 27 2.8 0.20.0
* Blank was run at return temperature of 11ûF. This
reduction in severity of test conditions for the blank was
necessitated by excessive scaling at higher temperatures.
** Averaqe of two tests.
-- ~5 --
1 329474
¦ It has been found advisable in some cases to add sma11
quantities Of tolyltriazole.
¦ Tolyltriazole is explained in Hackh's Chemical
Dictionary, Fourth Edition, page 91 (CF. ~enzotriazole) and is
employed as a corrosion inhibitor for copper and copper alloy
surfaces in contact with water when it is used it is applied to
the system at a dosage ranging between 1-2ûppm by weight.
I . .
~ . ' ..
, ~
