Note: Descriptions are shown in the official language in which they were submitted.
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Taurine-modified acrylic acid-based homopolymers for water treatment
The present invention relates to a process for preparing (meth)acrylic acid
copolymers,
the (meth)acrylic acid copolymers obtainable by this process, and also their
use for
water treatment, preferably in cooling and heating processes, and in the
inhibition of
scale in petroleum production.
In petroleum production, owing to temperature changes and mixing of oilfield
water with
injection water, precipitates of carbonates and sulfates of the alkaline earth
metals
occur during the production process. They block the pores of the formation and
accumulate on pipe surfaces, which makes production difficult and sometimes
impossible.
In the treatment of water, in cooling or heating processes, including seawater
desalination, or in heat transfer processes in general, to the respective
cooling or
heating medium are generally added formulations which prevent, or at least
greatly
delay, the corrosion and deposition in the circuits. For this are used
formulations which
comprise, according to requirements, zinc salts, polyphosphates, phosphonates,
polymers, biocides and/or surfactants.
To master corrosion protection and antiscaling in open cooling circuits, a
distinction is
made in principle between two processes:
Firstly, phosphorus-containing formulations can be used in the cooling and
heating
media. Typical examples of these are polyphosphates and phosphonates such as
1-hydroxyethane-1,1-diphosphonic acid (H EDP), 2-phosphonobutane-1,2,4-tri-
carboxylic acid (GBTC) and aminotrimethylenephosphonic acid (ATMP), each of
which
is used in the form of its sodium salt. These phosphorus-containing
formulations
generally effect hardness stabilization. Polyphosphates, furthermore, enhance
the
corrosion inhibition.
Alternatively, in cooling and heating media, zinc salts can also be used, in
which case
the zinc ions present therein chiefly serve to protect steel.
In some cases, zinc salts in small amounts are also added to the phosphonates
in
order, in addition to hardness stabilization, to simultaneously protect the
steel used.
The actions of these additives are reinforced by suitable polymers:
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Suitable polymers can firstly reinforce the action of phosphonates for
hardness
stabilization and, secondly, they can also stabilize polyphosphates, in
particular when
these are added at high concentrations. This prevents calcium phosphate
precipitation.
In addition, suitable polymers can also stabilize zinc compounds so that
deposition on
the metal surface, and thus destruction of the protective film, does not
occur. The
anticorrosive action is explained in the example of phosphonates by the fact
that a film
forms on the metal surface. This separates the steel from the cooling or
heating
medium. The film which forms consists for the most part of iron(II) and
calcium ions
and the included phosphonate. It is extremely thin so that stabilization must
ensure the
prevention of breakdown and the possibility of corrosion occurring at
individual points.
Polymers suitable for stabilizing phosphonates and phosphates are in principle
known
from the prior art.
Thus, for example, EP-A 0 244 584 describes, for example, N-substituted
acrylamides
which bear sulfoethylamide groups and are used for corrosion inhibition of
industrial
cooling circuits. These N-substituted acrylamides are prepared by
transamidation of
polymeric acrylamides. The N-substituted acrylamides according to EP-A 0 244
584
inhibit the phosphate ions, but not the phosphonate ions.
EP-B 0 330 876 describes N-substituted acrylamides which are structurally
analogous
to EP-A 0 244 584. The use as claimed in EP-B 0 330 876 of these N-substituted
acrylamides relates, however, to stabilizing iron in aqueous systems, with the
exact
degree of amidation of the N-substituted acrylamides used not being disclosed.
US 4,801,388 describes processes to inhibit deposits in aqueous systems by
adding
polymers based on (meth)acrylic acid and sulfoalkyl(meth)acrylamide or
(meth)acrylamide.
US 4,604,431 describes a process for preparing acrylamidoalkylsulfonic acid by
reacting acrylic acid or methacrylic acid-group-containing polymers with
alkylsulfonic
acids under pressure and at elevated temperature.
US 4,756,881 discloses the use of polymers containing acrylamidoalkanesulfonic
acids
in combination with organic phosphates for corrosion inhibition in industrial
cooling
waters.
The polymers of the abovementioned prior art have the disadvantage that they
precipitate at relatively high calcium concentrations. In particular, in the
case of the joint
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use of phosphonate ions and zinc ions in cooling or heating circuits, in
addition,
polymers are advantageous which act simultaneously in a stabilizing manner
both
toward phosphonate ions and also toward zinc ions. In addition, polymers are
advantageous which, when polyphosphate additives are used, and in particular
in the
presence of calcium ions at high concentration, inhibit a precipitation of
calcium
phosphate. Finally, polymers are desirable which generally disperse solid
particles, so
that their deposition on the metal surfaces of the cooling or heating systems
is avoided.
These requirements are not met, or are met only inadequately, by the polymers
of the
prior art.
It is an object of the present invention, therefore, to provide a process for
preparing
polymers which, in cooling or heating circuits, in the respective medium,
reinforce the
hardness-stabilizing action of phosphonates and simultaneously stabilize
polyphosphates, so that, for example, precipitation does not occur in the
presence of
calcium ions. Furthermore, the polymers obtainable by the inventive process
are to
stabilize zinc compounds, so that these do not form deposits on the metal
surfaces of
cooling or heating circuits.
According to the invention, this object is achieved by a process for preparing
(meth)acrylic acid copolymers which comprises the following process steps:
(1) free-radical polymerization of (meth)acrylic acid, a polymer I resulting,
and
(2) amidation of the polymer I resulting from process step (1 ) by reaction
with at
least one aminoalkanesulfonic acid.
In process step (2) of the inventive process, the ratio of the carboxylate
groups of the
polymer I resulting from process step (1) in relation to the
aminoalkylsulfonic acid is
preferably from 2:1 to 15:1, particularly preferably from 3:1 to 11:1, in
particular from
4:1 to 8:1.
Process step (1) is carried out at temperatures of preferably from 100 to
200°C,
particularly preferably from 105 to 135°C, in particular from 120 to
125°C.
Process step (1 ) is preferably carried out in a closed reaction vessel, for
example an
autoclave. The pressure in process step (1) is thus generally given by the
vapor
pressure (autogenous pressure) of the components used at the abovementioned
temperatures. Independently thereof, if appropriate additional pressure or
else reduced
pressure can be employed.
The free-radical polymerization of the monomers is preferably performed with
the use
of hydrogen peroxide as initiator. However, as polymerization initiators, all
compounds
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can alternatively be used which under the reaction conditions form free
radicals, for
example peroxides, hydroperoxides, peroxodisulfates, peroxodicarboxylic acids,
peroxocarboxylic esters and/or azo compounds.
If appropriate, in process step (1 ) of the inventive process, in addition
further
monomers can be used, for example ethylenically unsaturated monomers which can
be
copolymerized with (meth)acrylic acid. Suitable copolymers are, for example,
monoethylenically unsaturated carboxylic acids such as malefic acid, fumaric
acid,
itaconic acid, mesaconic acid, methylenemalonic acid and citraconic acid.
Other
copolymerizable monomers are C1- to C4-alkyl esters of monoethylenically
unsaturated
carboxylic acids such as methyl acrylate, ethyl acrylate, methyl methacrylate,
ethyl
methacrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl
acrylate, hydroxypropyl methacrylate and hydroxybutyl acrylate. Suitable
comonomers
are, in addition, alkyl polyethylene glycol (meth)acrylates which are derived
from
polyalkylene glycols having from 2 to 50 ethylene glycol units, monoallyl
ethers of
polyethylene glycols having from 2 to 50 ethylene glycol units and allyl
alcohol. Other
suitable monomers are acrylamide, methacrylamide, N-vinylformamide, styrene,
acrylonitrile, methacrylonitrile and/or monomers bearing sulfonic acid groups
and also
vinyl acetate, vinyl propionate, allyl phosphonate, N-vinylpyrrolidone,
N-vinylcaprolactam, N-vinylimidazole, N-vinyl-2-methylimidazoline,
diallyldimethyl-
ammonium chloride, dimethylaminoethyl acrylate, diethylaminoethyl acrylate,
dimethylaminoethyl methacrylate and diethylaminoethyl methacrylate. The basic
monomers such as dimethylaminoethyl methacrylate can be used as comonomers,
for
example, in the form of the bases, as salts with strong acids such as with
hydrochloric
acid, sulfuric acid or phosphoric acid, or in the form of quaternized
compounds.
Likewise, the abovementioned acid group-containing monomers can be used in the
polymerization in the form of the free acids or as salts, for example the
sodium,
potassium or ammonium salts.
The inventive process can preferably be carried out in such a manner that the
(meth)acrylic acid copolymer has sulfonate groups containing a counterion
which is
selected from the group consisting of protons, alkali metal ions or ammonium
ions.
However, in general, the charges of the sulfonate radicals of the
(meth)acrylic acid
copolymers can be saturated with any desired counterion.
The polymer I obtainable in process step (1) of the inventive process is
preferably
obtained in a polymer solution which has a solids content of preferably from
10 to 70%,
particularly preferably from 30 to 60%, in particular from 45 to 55%.
In a particular embodiment of the inventive process, before the amidation of
the
polymer I in process step (2), the polymer solution containing the polymer I
is adjusted
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to a pH of preferably from 2.0 to 9.0, particularly preferably from 4.0 to
7.5, in particular
from 4.5 to 6.5. Bases which are suitable for this are in principle all bases,
but
preferably aqueous solutions of alkali metal hydroxides, for example aqueous
sodium
hydroxide solution.
The amidation (process step (2)) is preferably carried out under a protective
gas
atmosphere, for example with the use of argon or nitrogen.
Process step (2) of the inventive process is preferably carried out at
temperatures of
from 140 to 250°C, particularly preferably from 165 to 200°C, in
particular from 175 to
185°C. The molar ratio of monomer units in polymer I to
aminoalkanesulfonic acid is
preferably from 15:1 to 2:1, particularly preferably from 11:1 to 3:1, in
particular from
8:1 to 4:1. The pressure in process step (2) is preferably from 1 to 25 bar,
particularly
preferably from 5 to 17 bar, in particular from 7 to 13 bar.
In a particular embodiment of the inventive process, as aminoalkylsulfonic
acid,
aminoethylsulfonic acid is used, so that the polymer resulting from process
step (2) has
units based on aminoethylsulfonic acid. However, any other aminoalkylsulfonic
acids
can also be used. In this regard reference is made to the above
considerations.
The sulfoalkylamide structural units produced by process step (2) of the
inventive
process are preferably randomly distributed in the (meth)acrylic acid
copolymer:
The type of free-radical polymerization reaction in process step (1)
decisively affects
the distribution of the sulfoalkylamide units between the individual polymer
molecules
and along a polymer chain. Thus, a mixture of polymer chains of different
structure is
generally obtained than via the free-radical copolymerization of monomers of
corresponding structure. Thus, polymers prepared by polymer-analogous means
can
differ markedly from polymers which are obtained via the free-radical
copolymerization
of the monomer acrylamide with acrylic acid and subsequent transamidation of
the
amide units with aminoalkylsulfonic acid. Also, free-radical copolymerization
of acrylic
acid, terelactone acid and acrylamide with subsequent transamidation generally
leads
to other structures. In the case of the last-described polymerization, the
distribution of
the sulfoalkylamide units is predetermined by the copolymerization parameters
of the
monomers used in the free-radical copolymerization. The result is that the
statistics of
the distribution of different functional groups on the polymer backbone in the
case of
polymers synthesized by polymer-analogous means is generally different than
when
corresponding groups are introduced by free-radical copolymerization.
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The present invention further relates to (meth)acrylic acid copolymers which
are
obtained by the abovedescribed process.
These (meth)acrylic acid copolymers preferably contain
(a) from 30 to 95% by weight, preferably from 40 to 90% by weight,
particularly
preferably from 60 to 80% by weight, of a poly(meth)acrylic acid basic
framework,
(b) from 5 to 70% by weight, preferably from 10 to 60% by weight, particularly
preferably from 20 to 40% by weight, of amide units based on
aminoalkylsulfonic
acids,
where the total weight of the units in the (meth)acrylic acid copolymer is
100% by
weight and all weights are based on the (meth)acrylic acid copolymer.
The inventive (meth)acrylic acid copolymers, even in the substoichiometric
range,
prevent too many calcium ions from penetrating into the film on the metal
surfaces of,
for example, cooling or heating circuits.
The weight-average molecular weight of the inventive (meth)acrylic acid
copolymers is
preferably from 1000 to 20 000 g/mol, particularly preferably from 1500 to
10 000 g/mol, in particular from 2000 to 6000 g/mol. The weight-average
molecular
weight is determined here by gel-permeation chromatography (= GPC) at room
temperature using aqueous eluents.
The inventive (meth)acrylic acid copolymers have a K value of preferably from
5 to 50,
particularly preferably from 8 to 35, in particular from 11 to 16. The K value
was
determined by the method of Fikentscher (ISO 174, DIN 53726).
If appropriate, the inventive (meth)acrylic acid copolymers can additionally
contain units
of other ethylenically unsaturated monomers which are copolymerizable with
(meth)acrylic acid. Monomers suitable for this are, for example,
monoethylenically
unsaturated carboxylic acids such as malefic acid, fumaric acid, itaconic
acid,
mesaconic acid, methylenemalonic acid and citraconic acid. Other
copolymerizable
monomers are C1- to C4-alkyl esters of monoethylenically unsaturated
carboxylic acids
such as methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl
methacrylate,
hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate,
hydroxypropyl methacrylate and hydroxybutyl acrylate. Suitable comonomers are,
in
addition, alkyl polyethylene glycol (meth)acrylates which are derived from
polyalkylene
glycols having from 2 to 50 ethylene glycol units, monoallyl ethers of
polyethylene
glycols having from 2 to 50 ethylene glycol units and allyl alcohol. Other
suitable
monomers are acrylamide, methacrylamide, N-vinylformamide, styrene,
acrylonitrile,
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methacrylonitrile and/or monomers bearing sulfonic acid groups and also vinyl
acetate,
vinyl propionate, allyl phosphonate, N-vinylpyrrolidone, N-vinylcaprolactam,
N-vinylimidazole, N-vinyl-2-methylimidazoline, diallyldimethylammonium
chloride,
dimethylaminoethyl acrylate, diethylaminoethyl acrylate, dimethylaminoethyl
methacrylate and diethylaminoethyl methacrylate. The basic monomers such as
dimethylaminoethyl methacrylate can be used as comonomers, for example, in the
form of the bases, as salts with strong acids such as with hydrochloric acid,
sulfuric
acid or phosphoric acid, or in the form of quaternized compounds. Likewise,
the
abovementioned acid group-containing monomers can be used in the
polymerization in
the form of the free acids or as salts, for example the sodium, potassium or
ammonium
salts.
The amide units based on aminoalkylsulfonic acids can be derived from any
desired
aminoalkylsulfonic acid. Particularly suitable aminoalkylsulfonic acids are
those having
from 2 to 12, preferably from 4 to 10, carbon atoms. The amino groups can be
primary,
secondary or tertiary. As further substituents, the aminoalkylsulfonic acids
can have, for
example, hydroxyl groups or alkoxy groups or halogen atoms. The alkyl groups
can be
unsaturated, or preferably saturated, unbranched or branched, or joined to
form a ring.
The amino groups can be arranged within the chain of the aminoalkyl groups or
as
pendant substituents or terminal substituents. They can also be a constituent
of a
preferably saturated heterocyclic ring.
In a preferred embodiment of the present invention, the inventive
(meth)acrylic acid
copolymer contains the structural unit (II) based on aminoethanesulfonic acid
(taurine):
-CH-
I
C=O
I
N
W
X+ _03S
Generally, the charges of the sulfonate groups of the (meth)acrylic acid
copolymers
can be saturated with any desired counterion. Preferably, the counterion is
selected
from the group consisting of protons, alkali metal ions or ammonium ions.
The sulfoalkylamide structural units are preferably randomly distributed in
the
(meth)acrylic acid copolymer.
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The inventive (meth)acrylic acid copolymers differ markedly in their mode of
action in
water treatment, antiscaling and in corrosion protection from the
(meth)acrylic acid
polymers of the prior art which are obtained by transamidation of the
corresponding
(meth)acrylamide polymers with aminoalkylsulfonic acids.
This characteristic mode of action is due to the preferably random
distribution of the
sulfoalkylamide structural units. The direct amidation of the polyacrylic acid
decisively
affects the distribution of the sulfoethylamide units between the individual
polymer
molecules and along a polymer chain. Thus, characteristically, a mixture of
polymer
chains is obtained which have a different structure than by the free-radical
copolymerization of monomers of corresponding structure. Thus, polymers
synthesized
by polymer-analogous means differ, for example, markedly from polymers which
are
obtained by the free-radical copolymerization of the monomer acrylamide with
acrylic
acid and subsequent transamidation of the amide units with aminoethanesulfonic
acid.
In the case of the last-described polymerization, the distribution of the
sulfoethylamide
units is predetermined by the copolymerization parameters of the monomers used
in
the free-radical copolymerization. The result is that the distribution of
different
functional groups on the polymer backbone is significantly different by free-
radical
copolymerization than in the polymer-analogous introduction of corresponding
groups
into previously synthesized polymers.
Furthermore, the present invention relates to a process for stabilizing
phosphates,
phosphonates and/or zinc ions, for example zinc chloride or zinc phosphate, in
aqueous systems, where at least one inventive (meth)acrylic acid copolymer
and/or at
least one (meth)acrylic acid copolymer obtainable by the inventive process are
added
to the system. The amount of the polymer in the aqueous system is preferably
from 5
to 200 ppm, particularly preferably from 5 to 50 ppm, in particular from 10 to
40 ppm, in
each case based on the aqueous system.
The inventive polymers can be metered directly to the aqueous system via one
or more
metering points or else introduced in a mixture with another component.
The abovedescribed inventive (meth)acrylic acid copolymers and/or
(meth)acrylic acid
copolymers obtainable by the inventive process can be used for water
treatment,
antiscale in petroleum production and/or for corrosion inhibition in aqueous
systems.
If appropriate it can be expedient to use the inventive (meth)acrylic acid
copolymers in
formulations. The present invention thus further relates to formulations for
water
treatment, antiscaling in oil production and/or for corrosion inhibition which
comprise at
least one inventive (meth)acrylic acid copolymer and/or at least one
(meth)acrylic acid
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copolymer obtainable by the inventive process. If appropriate, the inventive
formulations comprise other constituents. Such formulation constituents are,
for
example:
a) condensed linear and cyclic polyphosphates, such as sodium triphosphate,
sodium hexametaphosphate;
b) phosphonates, such as 2-phosphonobutane-1,2,4-tricarboxylic acid, aminotri
(methylenephosphonic acid), 1-hydroxyethylene(1,1-diphosphonic acid),
ethylenediaminetetramethylenephosphonic acid, hexamethylenediaminetetra
methylenephosphonic acid or diethylenetriaminepentamethylenephosphonic
acid,
c) aminocarboxylates such as nitrilotriacetic acid, ethylenediaminetetraacetic
acid,
diethylenetriaminepentaacetic acid, hydroxyethylethylenediaminetriacetic acid,
methylglycinediacetic acid, gluconate, glucoheptonate, ethylene
diaminedisuccinate and iminodisuccinate;
d) water-soluble polymers, such as homo- and copolymers of sulfonated
monomers, such as 2-acrylamido-2-methylpropanesulfonic acid, styrenesulfonic
acid or vinylsulfonic acid having a weight-average molecular weight of from
500
to 15 000 or naphthalenesulfonic acid-formaldehyde polycondensates,
in addition to other formulation constituents such as surfactants,
dispersants,
defoamers, corrosion inhibitors, oxygen scavengers and biocides.
The formulation which comprises the inhibitory or dispersive polymer can be
added
directly to the aqueous system via one or more metering points.
The present invention is illustrated on the basis of the examples hereinafter.
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EXEMPLARY EMBODIMENTS:
1.) Preparation of inventive polymers
A polymer is prepared from acrylic acid (process step (1 )).
a) In a reactor with nitrogen feed, reflux condenser and metering apparatus, a
mixture of 394 g of distilled water and 5.6 g of phosphorous acid (50%
strength) is heated to 95°C internal temperature with nitrogen feed and
stirring. Then, (1 ) 936 g of acrylic acid, (2) 280 g of sodium peroxysulfate
solution (10% strength) and (3) 210 g of a 40% strength by weight aqueous
sodium hydrogensulfite solution were added continuously in the course of
5 h. After further stirring for one hour at 95°C, the reaction mixture
was
cooled to room temperature and adjusted to a pH of 4.0 by adding 169 g of
50% strength by weight sodium hydroxide solution.
A clear polymer solution was obtained having a solids content of 54% by
weight and a K value of 25 (1% strength by weight aqueous solution,
25°C).
b) A mixture of 1000 g of the polymer solution from a) (solids content = 50%)
and 130.47 g of taurine (aminoethanesulfonic acid) was charged into a
pressure-stable reaction vessel equipped with agitator, nitrogen feed,
temperature sensor, pressure display and venting means. To this mixture
were added 110 g of a 50% strength aqueous sodium hydroxide solution.
The apparatus was flushed three times with nitrogen and sealed. Then, the
mixture was heated with stirring to an internal temperature of 180°C.
In the
course of this a pressure of approximately 10 bar built up. The mixture was
held for 5 hours at this temperature. The mixture was then cooled without
expansion. The apparatus was opened and adjusted to a pH of 7.2. This
produced a clear yellow solution having a solids content of 49.6% and a K
value of 14.6 (1% strength in 3% NaCI solution).
2.) Preparation of the reference polymer by transamidation
a) In a reactor equipped with nitrogen feed, reflux condenser and metering
apparatus, 180 g of distilled water were initially charged and heated to
reflux temperature with nitrogen feed and stirring. The nitrogen stream was
shut off and then, in parallel, (1) 180.15 g of acrylic acid, (2) 35.55 g of
acrylamide, (3) 143.8 g of a 30% strength by weight aqueous hydrogen
peroxide solution and (4) 21.6 g of mercaptoethanol (10% strength by
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weight in water) were added continuously in the course of 5 h. After further
stirring for two hours at reflux temperature, the reaction mixture was cooled
to room temperature and adjusted to a pH of 4.0 by adding 169 g of 50%
strength by weight sodium hydroxide solution.
A clear solution of poly(acrylamide) [16.6 mol%]-acrylic acid having a solids
content of 18.2% by weight and a K value of 11.5 (1% strength by weight
aqueous solution, 25°C) was obtained.
b) The transamidation is performed on the basis of the preparation protocol
from the patent EP 0 330 876 B1, example 1, the ratio of COOH to S03H in
the product being adapted so that the polymer is comparable to example 1
(same taurine content in both polymers, the pH having been increased to 6
to increase the conversion rate):
A mixture of 500 g of the polymer solution from a) (solids content = 18.2%)
and 27.7 g of taurine (aminoethanesulfonic acid) was charged into a
pressure-stable reaction vessel equipped with agitator, nitrogen feed,
temperature sensor, pressure indicator and venting means. To this mixture
were added 76.7 g of a 50% strength aqueous sodium hydroxide solution.
The apparatus was flushed three times with nitrogen and sealed. The
mixture was then heated to an internal temperature of 150°C with
stirring.
In the course of this a pressure of approximately 10 bar built up. The
mixture was held at this temperature for 4 hours. The mixture was then
cooled without expansion. The apparatus was opened and adjusted to a pH
of 7.2. A clear yellow solution having a solids content of 25.4% and a K
value of 13.9 (1% strength in 3% NaCI solution) was obtained.
3.) Use of polymers for inhibiting calcium phosphate and calcium
phosphonate
a) Calcium phosphate inhibition
The basis is the test of inhibitory activity of polymers for use in cooling
water
circuits.
Equipment: Dr. Lange Photometer, type LP2W
435 nm filter
Suction filter apparatus equipped with 0.45 pm membrane filter
Shaking water bath (GFL model 1083)
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300 ml Lupolen beaker (sealable)
disposable cuvettes (4 ml, Ratiolab)
Sartorius balance type LC 4800 - P
Reagents: vanadate/molybdate - reagent for phosphate determination
(Merck)
test solution A: 0.42 g of H3P04 solution (5%) made up to 1 I
with distilled water
test solution B: 1.64 g/1 of CaCl2 . 6 H20
0.79 g/1 of MgS04 . 7 H20
1.08 g/1 of NaHC03
polymer solution: 0.1 % strength, based on active substance
Procedure: 100 ml of the test solution A are placed in the Lupolen beaker,
2-4 ml of 0.1 % strength polymer solution are metered in (10-
ppm) and then 100 ml of the test solution B are added. After
sealing the beaker, it is placed into the shaking bath for 24 h at
70°C. After cooling (approximately 1 h), the sample solutions
are filtered off by suction through membrane filters (0.45 pm).
20 50 ml of the filtered solution are then taken for determining the
residual amount of phosphate, by adding 10 ml of the
vanadate/molybdate reagent. After a reaction time of
10 minutes, the phosphate content can then be determined
using the photometer on the basis of calibration curves.
Concentration
of the test
solution: GH = 5.4 mmol/I
KH = 6.42 mmol/I
P04 = 10 ppm
polymer = 10-20 ppm of active substance
Table: Inhibition [%]
Dosage (ppm) 15 20 25
Taurine-modified polymer (according 90 96 100
to the invention)
Transamidated polymer (not according 38 96 100
to the invention)
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. . .. .
b) Calcium phosphonate inhibition
The basis is the test of inhibitory action of polymers for use in cooling
circuits.
Equipment: Dr. Lange Photometer type LP 2 W, 800 nm filter
suction filter apparatus equipped with 0.45 pm membrane filter
shaking water bath (GFL model 1083)
300 ml Lupolen beaker (sealable)
Dr. Lange test kit LCK 350
Sartorius balance type LC 4800 - P
Reagents: Test solution A:
2.2 g/1 of HEDP 1% strength WS (bequest 2010) or 5.7 g/1 of
PBTC 1 % strength WS (Bayhibit AM) or 2.1 g/1 of ATMP 1
strength WS (bequest 2000), make up to 1 I with distilled water
Test solution B:
1.64 g/1 of CaCl2 - 6 H20
0.79 g/1 of MgS04 - 7 H20
1.08 g/1 of NaHC03
0.1 % polymer solution, based on active substance
Procedure: 100 ml of test solution A are placed in the Lupolen beaker, 2-
4 ml of 0.1% strength polymer solution are added (10-20 ppm)
and then 100 ml of test solution B are added. After the beaker is
sealed, it is placed in the shaking bath for 24 hours at 70°C.
After it has cooled (approximately 1 h), the test solutions are
filtered off by suction through a membrane filter (0.45 pm). The
amount of phosphonate inhibited is then determined by
Dr. Lange test kit LCK 350.
Concentration
of test solution: GH = 5.4 mmol/I
KH = 6.42 mmol/I
P04 = 10 ppm
polymer = 10-20 ppm active substance
Table: Inhibition [%]
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Dosage (ppm) 10 20 30
Taurine-modified polymer (according 68 94 100
to the invention)
Transamidated polymer (not according 52 84 89
to the invention)
The transamidated polymer is a terpolymer of AA, acrylamide and
acrylamidoethanesulfonic acid. The inventive polymer has an increased calcium
phosphate inhibition in the lower dosage range compared with the transamidated
polymer. This activity is especially marked when substoichiometric amounts are
used.
4.) Examples of formulations for water treatment, in particular for cooling
water
a) Polymerlzinc formulation (free from phosphate)
i) Inventive 40% (antiscale, zinc stabilization)
polymer
ii)Zinc chloride25% (anticorrosion)
iii)Tolyltriazole0.5% (anticorrosion)
iv)Antifoam 2% (wetting)
v) Biocide (control of microorganisms)
b) Organic formulation (free from phosphate and heavy metals)
i) Inventive polymer 20-25% (phosphonate stabilization,
dispersion of sludge)
ii) Phosphonate (HEDP + 10-20% (antiscale, corrosion
PBTC) inhibition)
iii)Tolyltriazole 2-5% (anticorrosion)
iv) Antifoam 1-3% (wetting)
v) Biocide (control of microorganisms)
HEDP = 1-hydroxyethane-1,1-diphosphonic acid, sodium salt
PBTC = 2-phosphonobutane-1,2,4-tricarboxylic acid, sodium salt
c) Phosphatelphosphonate formulation
i) Inventive polymer 20% (phosphate inhibition,
phosphonate inhibition)
ii)Phosphate/phosphonate5-15% (anticorrosion, antiscale)
iii)Tolyltriazole 2-5% (anticorrosion)
CA 02544771 2006-05-04
-15-
iv) I Antifoam 1-3% (wetting)
5.) Determination of the average molecular weight
The weight-average molecular weight was determined by gel-permeation
chromatography (= GPC) at room temperature using aqueous eluents (0.08 m TRIS
buffer (TRIS = tris(hydroxymethyl)aminomethane) having pH = 7 in distilled
water +
0.15 m NaCI + 0.01 m NaN3). The samples had a concentration of c = 0.1 % by
mass,
and the injection volume was V,~~ = 200 pL. The calibration was performed
using a
broadly distributed sodium polyacrylate calibration mixture. The
chromatography
column combination consisted of Waters Ultrahydrogel 1000, 500, 500 and TSK PW-
XL 5000 (from TosoHaas). A differential refractometer was used for detection.
