Note: Descriptions are shown in the official language in which they were submitted.
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1-Hydroxy-3-sulfonoalkane-1,1-dinhosuhonic acids
The present invention relates to 1-hydroxy-3-sulfonopropane-1,1-diphosphonic
acids
and phosphonate mixtures containing these acids, a process for their
preparation and
their use as water treatment chemicals and sequestering agents.
In industrial water systems such as cooling water systems or steam generating
systems, but also alkaline cleaning, for example in the food industry, water
treatment
chemicals and sequestering agents are used for protection against unwanted
deposits
of sparingly soluble calcium salts (boiler scale) and, if appropriate, also
against
corrosion of the ferrous materials.
1-Hydroxyalkane-1,1-disphosphonic acids containing the structural element -
C(OH)-
(P03Hz)2 have long been known as water treatment chemicals. They are obtained
by
reacting carboxylic acids or carboxylic acid derivatives with inorganic
compounds of
trivalent phosphorus under dehydrating conditions and subsequent hydrolysis.
The best known representative of 1-hydroxyalkane-l,l-diphosphonic acid is
1-hydroxyethane-l,l-diphosphonic acid (HEDP) of the formula
CH3-C(OH)(P03H2)a
HEDP is synthesized from an excess of acetyl derivative and an inorganic
compound
of trivalent phosphorus under initially dehydrating conditions, for example by
reacting 2.4 mol of acetic acid, 1 mol of PC13 and 0.6 mol of water,
subsequent
hydrolysis and removal of excess acetic acid (see US-A-4 060 546, Example 2).
The
most important application for HEDP is inhibition of boiler scale formation in
cooling waters (P.R. Puckorius, S.D. Strauss; Power, May 1995, pages 17 to 28,
particularly page 18).
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One advantage of HEDP is the single-stage synthesis from inexpensive raw
materials. One disadvantage of HEDP is the fact that it forms a very sparingly
soluble
calcium salt. In the event of nigh calcium contents in the cooling water, the
HEDP Ca
salt precipitates out, so that the effective concentration of the inhibitor
decreases in
solution and instead of the calcium carbonate deposits to be prevented,
deposits of
the HEDP Ca salt can then occur.
US-A-5 221487 proposes using cn-sulfono-1,1-diphosphonic acids of the formula
i OsH2
H03S-(CH2)~ i -X
P03H2
as boiler scale and corrosion inhibitors, where n can have integral values
between 3
and 10 and X can be OH or NHZ. The compounds where X = OH resemble HEDP to
the extent that both compounds have a 1-hydroxy-l,l-diphosphonic acid group
-C(OH)(P03H2)Z. An advantage of sulfonated phosphonic acids over HEDP is their
considerably higher calcium tolerance. This is impressively verified by
Example 10
in US-A-5 221 487.
The calcium tolerance of a scale inhibitor may be readily determined in a
standardized turbidity test, by increasing stepwise the concentration of the
inhibitor at
a fixed calcium concentration and fixed pH until a turbidity-causing deposit
occurs.
The higher the dosage of the inhibitor can be, without causing a significant
deposit,
the higher is its calcium tolerance. A high calcium tolerance means that using
an
inhibitor in water with high calcium content, a highly effective inhibitor
concentration can be established. This is a necessary but not sufficient
condition for
the use of an inhibitor in very hard waters. The actual activity of the
inhibitor must be
additionally verified in a scale inhibition test.
However, US-A-5 221 487 lacks a scale inhibition test which demonstrates the
activity of cn-sulfono-l,l-diphosphonic acids as scale inhibitors compared
with
HEDP. Thus a technical advantage over HEDP, as the closest prior art, is not
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demonstrated. A clear disadvantage of the sulfonated species from this
publication
compared with HEDP is more precisely their expensive synthesis: to prepare the
1-hydroxy-w-sulfonoalkane-1,1-diphosphonic acids, expensive cn-bromoalkane
carboxylic acids are used as raw materials. These are first reacted with
phosphorus
trichloride and water under dehydrating conditions to give w-bromo-1-
hydroxyalkane-1,1-diphosphonic acids. The bromine is then replaced by the
sulfonic
acid group by treating the reaction mixture with aqueous sodium sulfite
solution and
alkali metal hydroxide solution. The bromide eliminated remains dissolved in
the
aqueous product solution. It cannot be separated off and recovered for a
reasonable
expenditure.
A further 1-hydroxy-w-sulfonoalkane-1,1-diphosphonic acid of the formula
i OaH2
H03S-(CH2)~ i -OH
P03H2
where n =1
is mentioned in US-A-3 940 436 as a potential scale inhibitor (ibid., Compound
No.
21 in column 8). The shortest possible synthetic pathway for this compound
(ibid.,
column 3, lines 1 to 29) begins with the dehydration of the solid HEDP sodium
salt
to form the vinylidenediphosphonic acid sodium salt which then requires
complex
purification. The vinylidenediphosphonic acid sodium salt is then epoxidized
with
hydrogen peroxide in the presence of sodium tungstate as catalyst. The
resulting
epoxyethane-1,1-diphosphonic acid sodium salt must then be reacted with sodium
disulfite in aqueous solution (not with sulfuric acid, as erroneously
described in
US-A-3 940 436, Example XI).
The object underlying the present invention was to provide a scale and
corrosion
inhibitor which
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- may be synthesized from inexpensive raw materials and with high yields
- has good scale inhibition action in a very broad water hardness range and
- especially in waters having a very high calcium concentration does not
precipitate sparingly soluble calcium salts.
This object is achieved according to the invention by the provision of 1-
hydroxy-
3-sulfonopropane-l,l-diphosphonic acids of the formula (I) and their salts,
03M M3
M' 03S-C-C-C-OH (I),
R' R2 P03M4M5
where R' and R2 independently of one another denote hydrogen or methyl and M1
to
MS independently of one another represent a hydrogen ion, alkali metal ion,
ammonium ion or an alkylated ammonium ion,
with preference being given to compounds of the formula (I) in which
R1 and R2 denote hydrogen and M1 to MS independently of one another represent
a
hydrogen ion, alkali metal ion, ammonium ion or an alkylated ammonium ion, or
compounds of the formula (I) in which
RI denotes methyl and R2 denotes hydrogen and Ml to MS independently of one
another represent a hydrogen ion, alkali metal ion, ammonium ion or an
alkylated
ammonium ion, or compounds of the formula (I) in which
R' denotes hydrogen and RZ denotes methyl and M1 to MS independently of one
another represent a hydrogen ion, alkali metal ion, ammonium ion or an
alkylated
ammonium ion
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and the provision of phosphonate mixtures which are characterized in that they
consist of the following components:
- one or more sulfonic acids of the formula (II) or their salts
M' Z (II)
n-n
- one or more hydroxy acids of the formula (III) or their salts
H H
Z (III)
R R
n-~
- a phosphate of the formula (IV) = M'MZHP03
- a phosphate of the formula (V) = M'MZM3P04
where R1 and R2 independently of one another denote hydrogen or methyl, M' to
MS
and M' independently of one another represent a hydrogen ion, alkali metal
ion,
ammonium ion or an alkylated ammonium ion, Z represents a group of the formula
-COOM' or -C(OH)(P03M'MZ)2, n can assume integral values from 1 to 5 and the
mean value of n over all compounds of type (II) and (III) is between 1 and 2.
In the
mixture, at least one compound of the formula (II) where Z = -C(OH)(P03M'M2)2
and n = l, that is to say a compound of the formula (I), must be present.
If appropriate the inventive mixtures also contain a chloride of the formula
(VI) _
M'Cl or a hypophosphite of the formula (VII) = M'HZP02.
The preferred quantitative ratios of the individual components in the
phosphonate
mixture are such that
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- at least 30%, particularly preferably at least 60%, of the total phosphorus
of the
mixture is present in a compound of the formula (I),
- the molar ratio of the compounds of the formula (II) to compounds of the
formula (III) is at least 5 to 1, particularly preferably at least 10 to l,
- the molar ratio of the compounds of the formulae (II) and (III) where
Z = -C(OH)(P03M2)Z to compounds of the formulae (II) and (III) where
Z = COOM is at least 1 to 1, particularly preferably at least 2.3 to 1,
- a maximum of 50%, particularly preferably a maximum of 30%, of the total
phosphorus of the mixture is present in inorganic phosphorus compounds of the
formulae (IV) and (V),
- a maximum of 15% of the total phosphorus of the mixture is present in a
phosphate of the formula (V).
The phosphorus proportion in the individual compounds of the mixture is
determined
by the relative intensity of the signals of the respective compounds in the
31p_NMR
spectrum (see Examples 1 and 2). The phosphonate of the formula (I) shows a
characteristic triplet having a coupling constant 3JPH of 14.8 Hz (aqueous
solution of
the free acid at pH 0 to 1).
The molar ratio of compounds of the type (II) to compounds of the type (III)
is
determined in the 'H-NMR spectrum by the ratio of intensities of the -CHR'-
S03H
signals (compounds of the formula (II)) to the -CHR'-OH signals (compounds of
the
formula (III)). For example, signals of the compounds (II) where R' = H show a
chemical shift of 3.1 to 3.4 ppm, signals of the compounds (III) where R' = H
show a
chemical shift of 3.75 to 4.0 ppm, both measured against 3-(trimethylsilyl)-
tetradeuteropropionic acid sodium salt in DZO at a pH of 0 to 3.
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The molar ratio of the compounds of the formulae (II) and (III) where
Z = -C(OH)(P03M2)2 to compounds of the formulae (II) and (III) where Z = COOM
is determined in the 'H-NMR spectrum by the ratio of intensities of the
-CHRz-C(OH)(P03Mz)Z signals to the -CHR2-COOM signals. The former signals
show, for example for the case where R2 = H, a chemical shift of 2.0 to 2.5
ppm, and
the latter, for the case where R2 = H, a chemical shift of 2.5 to 3.0 ppm,
both
measured against 3-(trimethylsilyl)tetradeuteropropionic acid sodium salt in
D20 at a
pHofOto3.
The mean value of the coefficients n over all compounds of the formulae (II)
and
(III), that is to say the mean degree of oligomerization nmea", is also
calculated from
the 'H-NMR spectrum. For the case where the radicals R' and R2 both represent
hydrogen (raw material acrylic acid), the intensities of the above-described -
CH2-
S03H and -CH2-OH signals are added and multiplied by the factor 2. The
resultant
parameter gives the relative signal intensity of the outer protons. The signal
intensity
of the inner protons is determined from the intensity of the very broad
signals in the
range from 1.3 to 2.3 ppm (at pH 6 to 7, against 3-(trimethylsilyl)
tetradeuteropropionic acid sodium salt in D20) and in the range from 1.3 to
2.55 ppm
(at pH 0 to 3, against 3-(trirnethylsilyl)tetradeuteropropionic acid sodium
salt in
DZO). nmean is calculated from the formula below:
nmean = 4~3 (intensity of inner protons/intensity of outer protons) + 1
The formula must be amended appropriately for methacrylic acid or crotonic
acid as
raw materials.
The inventive compounds and mixtures may be prepared according to the
following
process steps, with the steps a), d) and e) being necessary, and steps b), c),
f) and g)
being optional:
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a) reaction of 1 mol of sulfur dioxide with at least 1 mol of water, at least
1 mol
of a monovalent base and with 0.9 to 2 mol of an unsaturated carboxylic acid
or a carboxylic acid mixture, with carboxylic acids of the formula
H
I
C=G-CUOH
R1 R2
being used and R' and R2 independently of one another denote hydrogen or
methyl;
b) if appropriate treatment of the reaction mixture from step a) with a
strongly
acidic cation exchanger in the H+ form;
c) if appropriate dewatering of the reaction mixture from step b);
d) reaction of the reaction mixture from a) or c) under dehydrating conditions
with a P(ITI) raw material, with the molar amount of phosphorus used being
1.6 to 2.4 mol, in the presence or absence of an amine salt;
e) hydrolysis of the reaction mixture from step d) with addition of a
sufficient
amount of water or aqueous hydrochloric acid;
f) if appropriate a distillation for the removal and recovery of volatile
constituents;
g) if appropriate a recovery of the amine added in step a) or d) by alkalizing
the
reaction mixture with alkali metal hydroxide solution, removing the amine
released and reusing of the amine in process step a) or d).
The unsaturated carboxylic acids to be used in process step a) are, for
example,
acrylic acid, methacrylic acid or crotonic acid; preference is given to
acrylic acid and
crotonic acid; particular preference is given to acrylic acid. Mixtures of
said
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carboxylic acids can also be used, for example a mixture of acrylic acid and
crotonic
acid.
The monovalent base to be used in process step a) can be an alkali metal
hydroxide,
ammonia or an aliphatic primary, secondary or tertiary amine. Preferably,
sodium
hydroxide or a tertiary amine is used, particularly preferably tributylamine.
The type of base used influences, inter alia, the proportion of oligomers in
the end
product. When sodium hydroxide is used as base, for example, markedly more
oligomers are obtained than with tributylamine as base.
The preferred molar amount of the added base must not be higher than the molar
amount of sulfur dioxide and unsaturated carboxylic acid in total. Together
with the
above-defined minimal amount of base, the preferred amount of base may be
calculated using the formula below:
Preferred number of moles of base = number of moles of S02 + (factor ' number
of
moles of unsaturated carboxylic acid)
The factor in the above formula preferably has values from 0 to l,
particularly
preferably values from 0.3 to 0.9. Any amine salt formed in process step a)
may
advantageously also be further used in this amount in the later process step
d).
The preferred amount of water to be used is, if sodium hydroxide is used as
base, 20
to 30 mol. If a tertiary amine is used as base, the preferred amount of water
is
substantially less. The reason for this difference is firstly the differing
solubility of
the salts, secondly the advantageous fact that dewatering according to process
step c)
can be omitted if an amine is used as base and if the amount of water in step
a) is
adapted to the substantially lower amount of water preferred in step d). If,
in step a),
tributylamine is used as base, and in the later process step d) PC13 is used
as P(ILI)
raw material, in process step a} preferably 3 to 5.8 mol, particularly
preferably 3.8 to
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4.6 mol, of water are used. This amount of water already corresponds to the
amount
required in process step d) plus the amount of water consumed by chemical
reaction
in process step a) (1 mol), so that the dewatering (process step c) and ion
exchange
(process step b) can be omitted.
The preferred amount of carboxylic acid to be used is, if sodium hydroxide is
used as
base, 1 to 2 mol, particularly preferably 1.05 to 1.15. If a tertiary amine is
used as
base, preferably 0.90 to 0.98 mol of carboxylic acid is used.
The molar amounts just mentioned are total amounts over the entire process
step a).
The amount of base added and the amount of water can, if process step a) is
carned
out stepwise, be readily divided: thus it has proved to be advantageous,
firstly
1) to react 1 mol of S02 with at least 1 mol of water and at least 1 mol of
base and
then to react this solution with
2) 0.9 to 2 mol of unsaturated carboxylic acid, the remaining base and the
remaining water.
This division into two partial steps 1) and 2) has the advantage that the pH
during the
reaction with the unsaturated carboxylic acid can be kept constant more
readily. The
preferred pH range for partial step 2) is 3 to 8, particularly preferably pH 5
to 6.
The procedure of process step a) becomes particularly simple if sodium
hydroxide is
used as base. Here, instead of the reaction of S02 with sodium hydroxide
solution
and water a solution of commercial sodium bisulfite can be prepared directly
in water
and reacted with a solution of carboxylic acid and sodium hydroxide in water.
If the
sodium bisulfite solution is introduced first and the sodium carboxylate
solution
added, the content of oligomers in the end product is lower than when the
sodium
carboxylate solution is introduced first and then the sodium bisulfite
solution is
added.
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The preferred reaction temperature for partial step 1) is 0 to 40°C.
For partial step 2),
20 to 80°C is preferred if an alkali metal hydroxide is used as base,
and 40 to 100°C,
if an amine is used as base.
Process step b) is only necessary if an alkali metal hydroxide was used as
base in step
a). In the ion-exchange process, at least 50%, preferably at least 70%, of all
alkali
metal ions should be exchanged for H+ ions. When an amine is used as base,
step b)
can be omitted.
The ion exchanger used can be a resin containing S03H groups, for example
LEWATTT~ S 100.
Process step c) is necessary if more than 4.8 mol of water per mole of SOZ
used are
present in the aqueous solution from process step a) or b). Process step c) is
generally
necessary after process step b), since the eluates from the ion exchanger
resin
generally contain too much water. When an amine is used as base, step c) can
be
omitted, provided that in step a) no more than 5.8 mol of water have been
used.
The dewatering is preferably carried out by distillation under a reduced
pressure
greater than or equal to 20 mbar and at a bottom temperature of less than or
equal to
90°C. A membrane process for concentrating the solution is also
suitable.
The P()ZI) raw material to be used in process step d) can be one of the
following pure
compounds or a mixture of the same compounds of trivalent phosphorus:
phosphorus
trichloride (PC13), phosphorus tribromide (PBr3), phosphorus trioxide (P40~),
pyrophosphorous acid (H4P205), phosphorous acid (H3P03) and monoalkyl, dialkyl
and trialkyl esters of phosphorous acid, with methyl and ethyl preferably
being used
as alkyl groups.
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The P()ZI) raw material only gives the desired reaction under dehydrating
conditions.
Dehydrating conditions means that, in the reaction mixture of step d), the
initial
molar ratio of the phosphorus-bound oxygen atoms (mol OP_~""a) to all of the
phosphorus atoms present in the mixture (mol P~o~,) must not be greater than
2.4. To
calculate this initial molar ratio (mol Op_,,~"na)/(mol Pto~,), all oxygen
atoms from the
phosphorus raw materials in addition to the oxygen atoms from any added water
or
from water already present in the reaction mixture are added and divided by
the
number of P atoms from all added phosphorus raw materials. The oxygen atoms
from
raw materials other than water and P(III) raw material are not included in the
total.
Preference is given to initial molar ratios (mol OP_~"na)/(mol Pto~1) of 1 to
2.4.
The raw materials in question have, as pure substances, the following initial
molar
ratios (mol OP_bo"~a)/(mol Pto~~): phosphorus trichloride and phosphorus
tribromide
(0), phosphorus trioxide (1.5), pyrophosphorous acid (2.5), phosphorous acid
and its
esters (3). In accordance with the above condition, only phosphorus trioxide
can be
used as pure substances, all other substances, to achieve the desired molar
ratio, must
be used as a mixture with another suitable P(I>I) raw material or as a mixture
with
water.
Preferred P()ZI) raw materials are the readily available and inexpensive
chemicals
phosphorus trichloride and phosphorous acid. If these preferred raw materials
are
used, an initial molar ratio (mol OP_~"nd)/(mol P~otat) of 1.4 to 1.8 is very
particularly
preferred. To achieve an initial molar ratio (mol OP_bo"na)/(mol Pto~,) of
1.5, for
example, 1 mol of phosphorus trichloride must be used together with 0.5 mol of
phosphorous acid or together with 1.5 mol of water. Phosphorus trichloride,
phosphorous acid and water can also be employed in a ternary combination. In
this
case the use of 3/3 mol of PCI3 to 2/3 mol of water and 1/3 mol of H3P03 is
particularly advantageous, because phosphorous acid can then be used in the
form of
a particularly inexpensive 70% strength aqueous solution, a waste product from
fatty
acid chlorination.
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The reaction step d) can be carried out in the presence of an amine salt,
with,
preferably, the amine salt used being that amine which was previously added in
process step a). If, in process step a) in addition to the amount of amine the
amount
of water is also set in accordance with the conditions of process step d),
only the
P(I>I) raw material needs to be added to the reaction mixture in step d).
If an amine is first added in process step d), the molar amount of the free
acids added
in process step d) plus the acids formed by hydrolysis of PC13, PBr3 or P406
must be
greater than the molar amount of the free amine, that is to say the reaction
mixture
must have an acid excess. If, for example, PC13, water and H3P03 are used as
raw
materials, this condition may be expressed in the following inequality:
2 (number of moles of H3F03) + 2 (number of moles of water) - (number of moles
of
amine) > 0
The amine salt accelerates the reaction and leads to a higher yield of
phosphonate in a
shorter time. In the presence of an amine salt, the reaction in process step
d) requires
about one to three hours at 75°C.
The temperature in process step d) can be 40 to 180°C. Reaction
temperatures of 60
to 130°C are preferably employed. If low-boiling PC13 is used as raw
material, a
reaction temperature of 130°C - depending on the amount of water and
amount of
amine added - under some circumstances cannot be reached immediately, but only
after a heating phase of about one hour, while a large part of the PC13 reacts
to form
nonvolatile secondary products.
The sequence in which the raw materials are added is optional.
In process step e), the reaction mixture from process step d) is hydrolyzed.
For this,
at least as much water or aqueous hydrochloric acid is added so that all PCl
or PBr
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bonds, or P-O-P bridges, used in process step d) can be hydrolyzed. The amount
of
water already used in process step d) is taken into account here. If, for
example, in
process step d), in addition to other raw materials 1.5 mol of PCI3 and 1 mol
of water
were used, in process step c) at least 2 mol of water must further be added.
The
preferred amount of water is 1.1 to 20 times the minimum amount. The
hydrolysis is
preferably carried out at temperatures of 70 to 120°C, particularly
preferably at 90 to
110°C. The hydrolysis can also be earned out at elevated pressure. The
preferred
duration for the hydrolysis is one hour to 24 hours, particularly preferably
12 to 20
hours.
In the optional process step f), volatile constituents of the reaction
mixture, especially
water and hydrogen chloride, are distilled off. For this, the mixture is
preferably
heated to temperatures of up to 130°C and aqueous hydrochloric acid is
taken off
overhead at atmospheric pressure or under reduced pressure.
If process step d) was earned out in the presence of an amine salt, the
process is
completed by process step g). For this, the reaction mixture is adjusted to a
pH
greater than 7, preferably to pH 10 - 14 by addition of alkali metal hydroxide
solution, preferably sodium hydroxide solution. As a result, the amine is
liberated. It
can be removed by distillation in the case of trimethylamine, triethylamine or
tripropylamine. Tributylamine, tripentylamine or trihexylamine, owing to their
low
water solubility, can be very readily removed from the phosphonate mixture by
phase
separation. The recovered amine can be re-used in process step a) or d).
The inventive substances and mixtures can have highly versatile uses, for
example as
scale inhibitors and also as corrosion inhibitors. Fields of use of such
compositions
can be, for example: water treatment (for example treatment of cooling waters,
process waters, injected waters in secondary oil extraction and water
treatment in
mining) and industrial and institutional cleaner applications (for example
cleaning
containers and equipment in the food industry, bottle cleaning, institutional
dishwashers and laundry detergents).
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Compositions of this type contain a 1-hydroxy-3-sulfonopropane-1,1-
diphosphonic
acid of the formula (I) or a phosphonate mixture of substances of the formulae
(II) to
(V), if appropriate also (IIJ to (VII), preferably in a total phosphonic acid
concentration of 1 to 20%. Calculation of the concentration of free phosphonic
acid
is described in Example 1, process step g). Obviously, the compositions can
also
contain the phosphonic acids in the form of their alkali metal salts, ammonium
salts
or alkylammonium salts.
The inventive substances and mixtures can be used alone or in combination with
one
or more substances which have proved to be useful for the respective
application.
Examples of such further components are:
Zinc salts, molybdates, borates, silicates, azoles (for example tolyltriazole
or
benzotriazole), other phosphonic acids, homo-, co- and terpolymers based on
acrylic
acid, methacrylic acid, malefic acid, if appropriate also containing
comonomers
having phosphonate, sulfonate and/or hydroxyl side groups, other polyaspartic
acids,
ligninsulfonates, tannins, phosphates, complexing agents, citric acid,
tartaric acid,
gluconic acid, surfactants, disinfectants, dispersants, biocides. For those
skilled in the
art, it is obvious here that instead of acids (for example "phosphonic acid")
their salts
("phosphonates") and vice versa can also be used.
The inventive substances and mixtures to which polyaspartic acids and/or their
salts
have been added as additional component proved to be particularly
advantageous.
Preferred embodiments of the polyaspartic acids are described in DE 4 439 193
Al,
which is incorporated into the present application.
The present invention further relates to a process for water treatment which
is
characterized in that the inventive substances or mixtures are introduced into
the
water to be treated.
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The present invention further relates to a process for alkaline cleaning,
characterized
in that the inventive substances or mixtures are used as encrustation
inhibitors/-
sequestering agents.
The process for water treatment is to be described below using examples:
For example, the inventive substances or mixtures for preventing deposits and
coatings, when used in cooling systems having fresh water cooling, are added
to the
inlet water in concentrations between about 0.1 and 10 mg/1 of active
compound.
In cooling circuits, the additives for scale protection and/or corrosion
protection are
frequently added in a rate-dependent manner based on the makeup water. The
concentrations are between about 1 and 50 mg/l of active compound in the
circulating cooling water, which usually has a considerably higher water
hardness
than with fresh water cooling. Still higher water hardnesses frequently occur -
at least
at times - in smaller cooling water systems, for example for air conditioning
systems
for hospitals or large office blocks, because of inadequate maintenance. For
such
systems, additives having a high calcium tolerance are particularly desirable.
Doses
are about 10 to 500 mg/l of active compound in the circulating cooling water.
In seawater desalination by distillation in MSF (mufti stage flash) and VP
(vapour
compression) systems, encrustations of the heat exchanger surfaces are
prevented by
additive additions of about 1 to 5 mg/1 of active compound, added to the inlet
seawater.
The doses required in RO (reverse osmosis) systems, because of the lower
maximum
temperatures necessitated by the process, are generally much lower.
The process for using the inventive substances and mixtures in alkaline
cleaning is
described as follows:
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The active compound concentrations used for inhibition of encrustation and
sequestering in alkaline cleaning depend in particular on the technical and
physical
conditions, for example pHs, residence times, temperatures, water hardnesses.
5 Whereas in the more weakly alkaline range (pH up to about 10) at
temperatures
below 60°C and relatively short residence times, active compound
concentrations of
markedly less than 100 mgll, generally 5 to 80 mg/l, are frequently
sufficient, at
higher alkaline concentrations and temperatures, doses of sometimes above 100
mgll
to 1000 mgJl may be necessary.
The inventive substances and mixtures have the following advantages over the
commercially used product HEDP:
- in waters having very high calcium concentration they do not form sparingly
soluble calcium salts. Their calcium tolerance is markedly higher, which is
verified by the low turbidity values in Table 1 of Example 3;
- in waters having a total hardness of 300 to 600 ppm CaC03, they are the more
effective scale inhibitors, because they prevent, in these waters which are
supersaturated with calcium carbonate, the formation of adherent coatings
(= scale) even at a lower dose than HEDP (see the symbol * for scale in
Tables 2 and 3). Furthermore, in these waters, the proportion of calcium ions
which can be kept in solution by the scale inhibitor (= residual hardness RH
[%]), is considerably higher when they are used than when HEDP is used (see
Tables 2 and 3). Even very hard waters having a total hardness of 1200 ppm
CaC03 are stabilized by the inventive inhibitors at a correspondingly high
dose to form a clear solution, whereas HEDP, owing to its low calcium
tolerance, under the same conditions leads to the precipitation of sparingly
soluble calcium salts (see Table 4, inhibitor concentration 400 mg/1).
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Compared with the 1-hydroxy-w-sulfonoalkane-1,1-diphosphonic acids of the
formula below proposed in the literature
P03H2
H03S-(CH2)~ C-X
P03H2
where n = 1 and n = 3 to 10 and X = OH, the inventive substances and mixtures
have
the following advantages:
- they can be prepared in good yields and from inexpensive raw materials;
- in waters having a total hardness of 300 to 600 ppm CaC03 they are the more
effective scale inhibitors, since they maintain, even at a very low dose of 2
to
5 mgll of inhibitor, a greater amount of calcium ions in solution than the
above-described 1-hydroxy-c~-sulfonoalkane-1,1-diphosphonic acids of the
above formula. This is verified by the measured residual hardnesses in Tables
2 and 3 (compare substance from Example 1 (according to the invention) with
the substances from Comparison Examples 3 and 4 (described above)).
Furthermore, the inventive compositions in waters containing 600 ppm of
CaC03 prevent the formation of adhesive coatings (= scale) even at a lower
dose than the above-described 1-hydroxy-cz~-sulfonoalkane-1,1-diphosphonic
acids (see the symbol * for scale in Table 3).
The process for preparing the inventive substances, compared with the above-
described preparation process for 1-hydroxy-w-sulfonoalkane-1,1-diphosphonic
acids
of the formula
P03H2
H03S-(CH2)~ -X
P03H2
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where n = 1 and n = 3 to 10 and X = OH, has the following advantages:
- it gives the previously unknown compounds of the above formula where n = 2
in good yield;
- it produces good scale inhibitors having very high calcium tolerance;
- furthermore it produces additional methyl-substituted compounds according
to formula I where R1 or R2 are methyl;
i0
Both of the preparation processes mentioned in the literature for the
literature-known
1-hydroxy-c~-sulfonoalkane-1,1-diphosphonic acids of the above formula where n
= 1
and n = 3 to 10 do not lead to the inventive compounds of the formula (I).
For example, the above-described preparation process for the compounds where n
=
3 to 10 from US-A-5 221 487 cannot be extended to compounds where n = 2. The
mixtures obtained in this experiment contain a component of the formula (I)
either
not at all or only in very low concentration (see Comparison Examples 1 and
2).
Therefore, these mixtures in all of the tests carried out exhibit a much
poorer scale
inhibition activity than the inventive mixtures of Example 1 (see Tables 1 to
4 under
"substance Comparison Example 1 (C3 backbone)").
The preparation process which is also described above for compounds where n =
1
from US-A-3 940 436 is not suitable in principle for preparing compounds of
the
formula (I), since the sulfono group and -C(OH)(P03H2)2 group, because of the
synthetic pathway via the epoxyethane-1,1-diphosphonic acid sodium salt, can
only
be separated from one another by a maximum of one CH2 group, but not by two
CH2
groups.
The inventive preparation process is thus the only process which permits the
preparation of compounds of the formula (I) in high yields.
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The invention is to be described in more detail on the basis of the following
examples. See above for the designation of the process steps.
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Examples
Example 1
Reaction according to the invention of acrylic acid with tributylamine, 502,
water and phosphorus trichloride
Process step a), part step 1)
740 g (4 mol) of tributylamine and 252 g (14 mol) of water are introduced into
a 2 I
multinecked flask equipped with stirrer, internal thermometer, pH electrode,
gas inlet
tube with a glass frit, reflux condenser and gas outlet tube attached thereto.
Sulfur
dioxide is introduced into this two-phase mixture with intensive stirnng at
20°C to
30°C until the mixture becomes one-phase and a pH of 4 is measured.
Weighing the
reaction mixture gives an increase in mass of 263.6 g which means that 4.12
mol of
SOZ were absorbed. In order to set a starting molar ratio of sulfur
dioxide/tributylamine/water of 1/1/3.5, a further 22 g of tributylamine and
7.5 g of
water are added to the mixture. 312 g of this total mixture thus correspond to
the
starting amounts 1 mol of sulfur dioxide, 1 mol of tributylamine and 3.5 mol
of
water.
Process step a), part step 2)
312 g of the above solution are introduced into a 1 1 multinecked flask
equipped with
stirrer, internal thermometer, 2 dropping funnels, pH electrode and reflux
condenser
with a gas line attached thereto. The mixture is preheated to 60°C.
72.42 g (1 mol) of
acrylic acid (99.5% pure) and 78.5 g {0.42 mol) of tributylamine are then
added
dropwise from two separate dropping funnels at this temperature in the course
of one
hour. The pH of the reaction mixture during this is between 5 and 5.5. After
the
dropwise addition, the mixture is further stirred for at least two hours at
60°C.
Iodometric determination of sulfite shows that after a further stirnng time of
one hour
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87.7%, and as much as 97.6% after a further stirring time of 2 h, of the S02
used is
no longer detectable as sulfite. 462.9 g of the resulting mixture correspond
to initial
quantities of originally 1 mol of 502, 1 mol of acrylic acid, 1.42 mol of
amine and
3.5 mol of water. Since one mol of water was already consumed in part step 1)
by
chemical reaction per mole of S02, the resulting amount of free water is only
3.5-1 _
2.5 mol. The amount of free water is critical for the following process step
d).
Sodium hydroxide solution is added to a sample of the solution which is
concentrated
after removing the amine on a rotary evaporator at 20 mbar and 90°C. A
1H-NMR
spectrum of this sample (containing 3-(trimethylsilyl)tetradeuteropropionic
acid
sodium salt as internal reference at 0 ppm) shows the compound (II) where Z =
COOH, R1 and R2 = H and n = 1 as two triplets at 2.58 ppm (for the -CH2-COONa
group) and 3.13 ppm (for the -CH2-S03Na group). At 3.65 to 3.85 ppm a signal
group for the different -CH2-OH species is visible. The molar ratio of -CH2-
S03Na to
-CH2-OH is 42. The mean degree of oligomerization nmean is very close to 1,
but
cannot be determined exactly, since residues of tributylamine interfere with
the
spectrum.
Process step d)
126.62 g of the above reaction mixture and 5.04 g (0.28 mol) of water are
introduced
into a 0.5 1 four-necked flask equipped with stirrer, internal thermometer,
dropping
funnel, reflux condenser (coolant temperature -15°C), gas outlet tube
attached
thereto, safety vessel and absorption vessel containing 1 1 of water for
trapping HCI
and entrained PC13, blanketed with nitrogen and heated to 60°C. The
mixture
introduced corresponds to initial quantities of originally: 0.274 mol of S02,
0.388
mol of amine, 0.274 mol of acrylic acid and 1.236 mol of water, the amount of
free
water being only 0.964 mol. Then, with stirring and cooling, 77.0 g (0.561
mol) of
phosphorus trichloride are added dropwise to this mixture in the course of 30
min at
a temperature of 60 to 70°C. The amount of phosphorus trichloride added
is
calculated such that the molar ratio of amount of phosphorus used to amount of
S02
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used is 2.05, and the molar ratio of amount of SOZ used to amount of
phosphorus
used is 0.49. Furthermore, the molar ratio of free water before the PCI3
addition to
the phosphorus used is 1.72. After the addition of PCI3, the reaction mixture
is stirred
for a further 3 hours at 70 to 80°C.
Process step e)
Thereafter, 280 ml of water are added dropwise with stirring, initially
slowly, and
then more rapidly after the initial HCl gas evolution has decayed, and the
mixture is
kept for a further 18 h at 100°C. In the absorption vessel containing 1
1 of water for
escaping HCl and PC13 gas (see process step d)), a total of 1.07 mol of HCl
and 0.02
mol of H3P03 were detected.
Process step g}
The reaction mixture is cooled to 40 to 50°C and 136 g (1.53 mol) of
45% strength
sodium hydroxide solution are added with stirring. The two-phase mixture at
60°C is
transferred to a separating funnel. The lighter, organic phase separating out
consists
of 70.4 g of tributylamine, which can be re-used in the synthesis without
further
purification (the recovery rate for tributylamine is 97.9% in this
experiment).
The heavier, aqueous phase (490.4 g) is the desired phosphonate mixture. From
the
mass of the aqueous phase, the molar amount of PCI3 used and the PCl3 loss by
evaporation, the phosphorus content of the solution is calculated at 3.41%.
In the aqueous phase, according to 31P-NMR analysis, 72.1% of the total
phosphorus
is present as phosphonate of the formula (I) where R1 and R2 = H. (The
percentages
from the NMR spectra correspond here, as in the following text, to the
relative area
percentages below the signals). The compound (I) appears in the 31P-NMR
spectrum
as a triplet at a chemical shift of 18.6 ppm. A further triplet of 2.8% of the
total signal
intensity is evident at 19.2 ppm. This signal is tentatively assigned to
compound (III)
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where Z = -C(OH)(P03M2)2, R' and RZ = H and n = 1. Also detectable are a
phosphite of the formula (IV) at 3.8 ppm (5.4% of the phosphorus) and a
phosphate
of the formula (V) at 3.4 ppm (10.2% of the phosphorus). Together with other
phosphonates of unknown structure, a total of 84.4% of the phosphorus is
present in
phosphonates. From this total phosphonate content in molar % according to 31p-
NMR analysis, the calculated total phosphorus content of the solution of 3.41
% by
mass and the molar weight of compound (I) where M and R = H of 300.1 g/mol, a
phosphonic acid content of 13.9% by mass is calculated. This concentration is
used
to calculate the initial weight in the application test.
A sample of the aqueous phase is adjusted to pH 2 to 3 with hydrochloric acid,
concentrated and dissolved in DZO. A 1H-NMR spectrum of this sample
(containing
3-(trimethylsilyl)tetradeuteropropionic acid sodium salt as internal reference
at
0 ppm) shows two signal groups which predominantly originate from compound (I)
where R' and R2 = H: a multiplet at 2.37 ppm (for the -CH2-C(OH)(P03M2)2
groups
of compound (I) and to a small extent of compound (III) where Z = -
C(OH)(P03M2)z,
R1 and RZ = H and n = 1) and a further multiplet at 3.24 ppm (for the -CH2-
S03M
groups of compound (I) and to a small extent of compound (II) where Z = COOH,
R'
and R2 = H and n = 1). Two lower intensity triplets at 2.6 and 2.75 ppm
represent the
-CH2-COOH groups of compound (III) where Z = COOH, R1 and R2 = H and n = 1
and of the analogous compound (II). The -CH2-OH groups of the compounds of the
formula (III) are visible as a signal group at 3.75 to 4 ppm. Residues of
tributylammonium ions appear at 0.93, 1.38, 1.7 and 3.1 ppm. The molar ratio
determined from the signal intensities of the compounds of formula (II) to
compounds of the formula (III) is 18.8 (= molar ratio -CHZ-S03M / -CH2-OH).
The
molar ratio of the compounds of the formulae (II) and (III) where Z =
-C(OH)(P03M2)Z to compounds of the formulae (II) and (III) where Z = COOM is
5.3 (= molar ratio -C(OH)(P03M2)2 / COOM).
A 13C-NMR spectrum of the acidic mixture (solvent D20, containing 3-(trimethyl-
silyl)tetradeuteropropionic acid sodium salt as internal reference, set to 1.7
ppm)
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exhibits, with 'H decoupling, the following chemical shifts and coupling
constants:
for compound (I) where R1 and R2 = H: 1-C: 76.3 ppm (t, 'J~p 149.8 Hz), 2-C:
33.0 ppm (s), 3-C: 50.6 ppm (t, 3J~p 6.6 Hz). For compound (III) where Z =
-C(OH)(P03M2)2, R1 and R2 = H and n = l: 1-C: 76.6 ppm (t, 1J~P 149.1 Hz), 2-
C:
35.7 ppm (s), 3-C: 62.1 ppm (t, 3J~P 7.3 Hz).
Example 2
Reaction according to the invention of acrylic acid with sodium hydroxide
solution, sodium bisulfite, water and phosphorus trichloride
Process step a)
80.1 g (1.1 mol) of acrylic acid (99% pure) are introduced into a vented
apparatus
and 197.6 g (1.0 mol) of 20.24% strength sodium hydroxide solution are added
with
stirring at 20 to 25°C in the course of 30 min. The end pH of the
sodium acrylate
solution is 6.5.
95.1 g (0.5 mol) of sodium bisulfite are dissolved in 300 ml of water in a
multinecked flask equipped with stirrer, dropping funnel, internal
thermometer, pH
electrode, reflux condenser and air line attached thereto. The pH of the
solution is
adjusted to pH 4.5 using approximately 5 ml of 20% strength sodium hydroxide
solution. Then, in the course of 1.5 h, the above sodium acrylate solution is
added
dropwise at 35 to 40°C with stirnng and cooling. The end pH of the
reaction mixture
is 6.3. The mixture is stirred for a further hour at 30 to 35°C.
Iodometric
determination of sulfite shows that after further stirnng for one hour 95.9%
of the
initial sulfite is no longer detectable.
A sample of the solution is concentrated on a rotary evaporator at 25 mbar and
90°C
heating bath temperature. A 1H-NMR spectrum of this sample in DZO indicates
that
acrylic acid is no longer present in the mixture. At 3.1 to 3.3 ppm (against
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3-(trimethylsilyl)tetradeuteropropionic acid sodium salt as internal
reference, set to
0 ppm), the -CH2-S03Na groups of different species are visible. At 3.8 ppm
there
appears the triple of a -CH2-OH species, at 4.3 to 4.4 ppm a signal group for
various
compounds containing the -CH2-O-CO group. The molar ratio of -CHZ-S03Na to
(-CHZ-OH + -CH2-O-CO-) is 7.1. At 1.3 to 2.3 ppm are the very broad signals
for the
inner protons of the different oligomers. The mean degree of oligomerization
nm~" is
calculated at 1.18.
The total mixture corresponds to the initial amounts of 1 mol of sulfur
dioxide, 2.025
mol of sodium hydroxide solution, 1.1 mol of acrylic acid and 25.6 mol of
water.
Process step b)
The solution from process step a) is applied to a column containing 1.4 1 of
ion
R
exchanger LEWATIT~ S 100 (acid form).
Process step c)
The eluate from process step b) is dehydrated on a rotary evaporator initially
at 60°C
heating bath temperature and 50 mbar pressure, finally for a further 10
minutes at
90°C and 20 mbar. 161 g of a solid residue are obtained. Karl-Fischer
titration
indicates a water content of 13.4%. Titration with sodium hydroxide solution
gives,
from the difference between the first and second equivalence point, a content
of
5.435 mmol of COOH groups per g of substance. Only half of the -S03Na groups
have been converted to -S03H groups.
A sample of the solution is concentrated on a rotary evaporator at 25 mbar and
90°C
heating bath temperature. A'H-NMR spectrum of this sample in D20 shows at 3.1
to
3.3 ppm (against 3-(trimethylsilyl)tetradeuteropropionic acid sodium salt as
internal
reference, set to 0 ppm) a triplet for the -CH2-S03M group of the compound
(II)
where Z = COOH, R' and RZ = H and n = l, and in the boundary zones of the main
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signal as a broadening the -CH2-S03M groups of analogous species where n > 1.
At
3.85 ppm there appears the triplet of a -CH2-OH species, and at 4.25 to 4.45
ppm a
signal group for various compounds containing the -CHZ-O-CO-group. The molar
ratio of -CH2-S03M to (-CH2-OH + -CH2-O-CO-) is 7.9. At 1.5 to 2.55 ppm there
are the very broad signals for the inner protons of the various oligomers. The
mean
degree of oligomerization nmeao is calculated at 1.18 (no change compared with
the
analysis after process step a)).
Process step d)
18.42 g of the reaction mixture from process step c) containing 0.1 mol of
COOH
groups and 2.47 g (0.137 mol) of water, and in addition 2.93 g (0.163 mol) of
water
and 37.08 g (0.2 mol) of tributylamine are introduced into a multinecked flask
equipped with stirrer, internal thermometer, dropping funnel and reflux
condenser
with a gas outlet tube attached thereto. Two liquid phases form on heating up
to 60°C
under nitrogen.
The mixture introduced corresponds to initial quantities of originally 0.01
mol of SO~
and 0.1 mol of acrylic acid and currently 0.2 mol of amine and 0.3 mol of
water.
27.5 g (0.2 mol) of phosphorus trichloride are then added dropwise to this
mixture
with stirring and cooling in the course of 21 min at a temperature of 60 to
65°C. The
amount of phosphorus trichloride added is calculated such that the molar ratio
of
amount of phosphorus used to amount- of S02 used is 2.2, and the molar ratio
of
amount of S02 used to amount of phosphorus used is 0.46. In addition, the
molar
ratio of free water before PCl3 addition to the phosphorus used is 1.5. After
PCl3
addition the reaction mixture is stirred for a further 21 hours at
75°C.
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Process step e)
100 ml of water is then added dropwise at 30 to 40°C with stirring in
the course of
15 min and the mixture is held for a further 21 h at 75°C. 40 ml of
water are then
added and traces of a suspended substance are filtered off.
Process step g)
70 g (0.79 mol) of 45% strength sodium hydroxide solution are added to the
filtrate.
The two-phase mixture at 60°C is transferred to a separating funnel.
The lighter,
organic phase separating off consists of tributylamine (the recovery rate for
tributylamine in this experiment is approximately 94%) which can be re-used in
the
synthesis without further purification.
The heavier, aqueous phase (216 g) is the desired phosphonate mixture. From
the
mass of the aqueous phase, the molar amount of PC13 used and the estimated
PCl3
loss of 8% by evaporation and sampling for analyses, a phosphorus content of
the
solution is calculated at 2.72%.
In the aqueous phase according to 3iP-NMR analysis, 37.6% of the total
phosphorus
is present as phosphonate of the formula (I) where R1 and RZ = H. This
compound is
visible in the 3lP-NMR spectrum as a triplet (3JPH = i2.8 Hz) at a chemical
shift of
18.7 ppm. A further triplet having 7.7% of the total signal intensity is
visible at
19.3 ppm. This signal is tentatively assigned to the compound (III) with Z =
-C(OH)(P03M2)2, R' and R2 = H and n = 1. Also detectable are a phosphite of
the
formula (IV) at 3.75 ppm (1.1% of the phosphorus) and a phosphate of the
formula
(V) at 6.0 ppm (19.7% of the phosphorus). Together with other phosphonates of
unknown structure, a total of 78.3% of the phosphorus is present in
phosphonates.
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Example 3
Reaction according to the invention of crotonic acid with tributylamine, 502,
water and phosphorus trichloride
Process step a), part step 1)
185 g (1 mol) of tributylamine and 63 g (3.5 mol) of water are introduced into
a
500 ml multinecked flask equipped with stirrer, internal thermometer, gas
inlet tube
with, glass frit, reflux condenser and gas outlet tube attached thereto.
Nitrogen is first
introduced into this two-phase mixture, then sulfur dioxide with intensive
stirnng at
25°C to 30°C until the second liquid phase disappears and the
mixture has changed
colour from colourless to yellow. Weighing the reaction mixture gives an
increase in
mass of 65.5 g which indicates that 1.02 mol of SOZ were absorbed. In order to
set an
initial molar ratio of sulfur dioxide/tributylamine/water of 1/1/3.5, a
further 4.33 g of
tributylamine and 1.47 g of water are added to the mixture. 312 g of this
total mixture
thus correspond to the initial amounts 1 mol of sulfur dioxide, 1 mol of
tributylamine
and 3.5 mol of water.
Process step a), part step 2)
312 g of the above solution are introduced into a 1 1 multinecked flask
equipped with
stirrer, internal thermometer, dropping funnel and pH electrode. The mixture
is
preheated to 60°C.
87.85 g ( 1 mol) of crotonic acid (98°lo pure) are melted together with
16.2 g (0.9 mol)
of water in a glass beaker and 74.0 g (0.40 mol) of tributylamine are added at
60°C
with water cooling. This one-phase mixture is added dropwise to the above
solution
from process step a), part step 2) in the course of 40 min at 60°C. The
mixture is
allowed to react for 23 h at 60°C and 5 h at 80°C. The pH of the
reaction mixture
after the reaction is 5.8. The resulting mixture (490 g) corresponds to
initial amounts
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of originally 1 mol of 502, 1 mol of crotonic acid, 1.4 mol of amine and 4.4
mol of
water. Since one mol of water has already been consumed per mole of SOZ by
chemical reaction in part step 1), the resulting amount of free water is only
3.4 mol.
The amount of free water is critical for the following process step d).
S
Sodium hydroxide solution is added to a sample of the solution and the
solution is
concentrated after removing the amine on the rotary evaporator at 20 mbar and
90°C.
A 1H-NMR spectrum of this sample (containing 3-(trimethylsilyl)tetradeutero-
propionic acid sodium salt as internal reference at 0 ppm) shows for the
compound
(II) where Z = GOOH, R1 = methyl, R2 = H and n = 1 the following signals: -
CH3:
1.31 ppm (d), -CHZ-COONa: 2.22 ppm (dd) and 2.84 ppm (dd), -CH-S03Na:
3.26 ppm (m). By-products containing -CH-OH groups or oligomers are not
detectable.
Process step d)
196 g of the above reaction mixture are introduced into a 0.5 1 four-necked
flask
equipped with stirrer, internal thermometer, dropping funnel, reflux condenser
(coolant temperature -15°C), gas outlet tube attached thereto, safety
vessel and
absorption vessel containing 1 1 of water for trapping HCl and entrained PCl3,
blanketed with nitrogen and heated to 60°C. The mixture introduced
corresponds to
initial amounts of originally: 0.4 mol of S02, 0.4 mol of crotonic acid, 0.56
mol of
amine and 1.76 mol of water, the amount of free water being only 1.36 mol. 110
g
(0.8 mol) of phosphorus trichloride are then added dropwise to this mixture in
the
course of 35 min at a temperature of 60 to 70°C with stirnng and
cooling. The
amount of phosphorus trichloride added is calculated such that the molar ratio
of
amount of phosphorus used to amount of SOZ used is 2, and the molar ratio of
amount of S02 used to amount of phosphorus used is 0.5. In addition, the molar
ratio
of free water before PCl3 addition to phosphorus used is 1.7. After PC13
addition the
reaction mixture is further stirred for 3 hours at 70 to 80°C.
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Process step e)
400 ml of water are then added dropwise with stirnng, firstly slowly, then
more
rapidly after the initial HCI gas evolution has decayed, and the mixture is
kept for a
further 18 h at 100°C. In the absorption vessel containing 1 I of water
for escaping
HCI and PC13 gas (see process step d)), in total 1.69 mol of HCl and 0.072 mol
of
H3P03 were detected.
Process step g)
The reaction mixture is cooled to 60°C and 213 g (2.4 mol) of 45%
strength sodium
hydroxide solution are added with stirring. The two-phase mixture at
60°C is
transferred to a separating funnel. The lighter, organic phase separating
consists of
102.5 g of tributylamine, which can be re-used in the synthesis without
further
purification (the recovery rate for tributylamine in this experiment is
98.9%).
The heavier, aqueous phase (724.5 g) is the desired phosphonate mixture. From
the
mass of the aqueous phase, the molar amount of PC13 used and the PC13 loss due
to
evaporation, a phosphorus content of the solution is calculated at 3.11%.
31
In the aqueous phase, according to P-NMR analysis, 52.2% of the total
phosphorus
is present as phosphonate of the formula (I) where Rl = methyl, R2 = H. This
compound is seen in the 31P-NMR spectrum as a multiplet and with 1H decoupling
in
the form of two closely adjacent signals at 18.9 ppm and 19.0 ppm. In
addition, a
phosphite of the formula (IV) is detectable at 3.7 ppm (11.1% of the
phosphorus) and
a phosphate of the formula (V) at 4.5 ppm (18.2% of the phosphorus). Together
with
other phosphonates of unknown structure, in total 70.7% of the phosphorus is
present
in phosphonates.
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Example 4
Reaction according to the invention of methacrylic acid with tributylamine,
S02, water and phosphorus trichloride
In a similar procedure to Example 3, methacrylic acid is used instead of
crotonic
acid.
In process step a), part step 2), the methacrylic acid is reacted from the
start at 80°C.
Sodium hydroxide solution is added to a sample of the reaction solution
obtained
there and, after removing the amine, the solution is concentrated on a rotary
evaporator at 20 mbar and 90°C. A 1H-NMR spectrum of this sample
(containing
3-(trimethylsilyl)tetradeuteropropionic acid sodium salt as internal reference
at
0 ppm) exhibits for the compound (II) where Z = COON, R' = H, RZ = methyl and
n = 1 the following signals: -CH3: 1.23 ppm (d), -CH-COONa: approximately
2.75 ppm (m), -CH2-S03Na: 3.31 ppm (dd) and approximately 2.85 (m).
After process step g), 960.6 g of aqueous phase are obtained. From the mass of
the
aqueous phase, the molar amount of PCl3 used and the PCl3 loss by evaporation,
a
phosphorus content of the solution is calculated at 2.93%.
In the aqueous phase according to 31P-NMR analysis, 39.1 % of the total
phosphorus
is present as phosphonate of the formula (I) where R' = H and R2 = methyl.
This
compound, in the 3~P-NMR spectrum, shows two multiplets which, with 'H
decoupling, are converted into two doublets at 19.4 ppm and 18.0 ppm with a
ZJPP
coupling constant in each case of 22.3 Hz. Also detectable are a phosphite of
the
formula (IV) at 3.7 ppm (29.4% of the phosphorus) and a phosphate of the
formula
(V) at 4.6 ppm (16.1% of the phosphorus). Together with other phosphonates of
unknown structure, a total of 54.5% of the phosphorus is present in
phosphonates.
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Comparison Example 1
In a similar manner to Example 7 from US-A-5 221 487, 3-bromopropionic acid is
first reacted with PC13 and water, and then with sodium sulfite and KOH.
Compared
with this Example 7, the starting amounts of the raw materials are tripled.
13.8 g (90 mmol) of 3-bromopropionic acid and 4.05 g (225 mmol) of water are
introduced into a multinecked flask equipped with stirrer, dropping funnel,
reflux
condenser and gas outlet tube attached thereto and warmed to 40°C. 20.7
g
(150 mmol) of phosphorus trichloride are added dropwise at a temperature of 40-
50°C with stirring in the course of 20 min. At the end of the addition,
the batch is
heated for 3 h under reflux in an oil bath at 150°C. During this the
mixture becomes
solid at times. After 3 h the mixture is allowed to cool to room temperature
and a
solution of 9.9 g (150 mmol) of 85% strength potassium hydroxide and 11.3 g
(90
mol) of sodium sulfite in 90 g of water are added dropwise with cooling in the
course
of 15 min. The solution is then heated for 19 h to 100°C with stirnng.
The clear
solution has an end pH of 4.85 and is evaporated to dryness. 38 g of a solid
are
obtained.
The 3IP-NMR spectrum (solvent DZO) shows a triplet which is characteristic of
the
-CHZ-C(OH)(P03M2)2 group of achiral compounds at 18.8 ppm. In this
-CH2-C(OH)(P03M2)Z group only 13.2% of the phosphorus is present. In addition,
a
compound of the formula
'P03H2
O
~/P~ OH
O OH
may be detected in the 'H-decoupled 3'P-NMR spectrum via two doublets at
37.2 ppm (endocyclic phosphorus) and 16.7 ppm (exocyclic phosphorus) with a
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coupling constant ZJpP of 35.9 Hz. 19.0% of the phosphorus is present in this
compound. Together with other phosphonates of unknown structure, a total of
93.4%
of the phosphorus is present in phosphonates. The majority of the phosphonates
present cannot be assigned by structure. 5.8% of the phosphorus is present as
phosphate of the formula (V) whose chemical shift is at 1.0 ppm.
A 'H-NMR spectrum of this sample (containing 3-(trimethylsilyl)tetradeutero-
propionic acid sodium salt as internal reference at 0 ppm) shows two triplets
which
chiefly originate from compound (II) where Z = COOM, R' and R2 = H and n = 1:
one triplet at 2.62 ppm (for the -CH2-COOM group of this compound) and one
further triplet at 3.15 ppm (for the -CH2-S03M group of this compound). In the
region typical of -CH2-S03M from 3 to 3.3 ppm, in addition to said triplet, no
further
signal can be seen. This means that the great majority of the sulfonic acid
groups are
not present in a compound of the type (I) but in a compound of the formula
(II) where
Z = COOM. A compound of the type (I), owing to the P,H coupling for the
protons
of the -CH2-S03M group, would have to show a complicated multiplet (see
Example
1), but not a simple triplet. The -CHZ-OH groups of the compounds of the
formula
(III) are visible as two triplets at 3.75 to 4 ppm. The molar ratio determined
from the
signal intensities of the compounds of the formula (II) to compounds of the
formula
(III) is 4 (= molar ratio -CHZ-S03M / -CHZ-OH).
Comparison Example 2
In a similar manner to Comparison Example 1, 3-bromopropionic acid is first
reacted
with PC13 and water, and then with an increased amount of sodium sulfite and
KOH.
The reaction is carned out as in Comparison Example l, except that 210 mmol of
KOH are used instead of 150 mmol and 145 mmol of sodium sulfite are used
instead
of 90 mmol. The final reaction mixture, before evaporation, has a pH of 6.45.
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The 3'P-NMR spectrum (solvent D20) shows two triplets which are characteristic
of
the -CH2-C(OH)(P03M2)2 groups of achiral compounds. One at 18.7 ppm, which has
2.9% of the total phosphorus signal intensity, and one at 19.5 ppm, which
indicates
15.4% of the total signal intensity. By adding a sample from Example 1 and
measuring the sample mixture again, it emerges that the originally smaller
signal
containing 2.9% of the phosphorus has markedly increased in intensity. It thus
corresponds to the compound of the formula (I) where R' and RZ = H and n = 1.
The
originally greater signal containing 15.4% of the phosphorus may be assigned
to the
compound of the formula (III) where Z = -C(OH)(P03Mz)Z, R' and R2 = H and n =
1.
In addition, a compound of the formula
P03M' M2
O
~P OH
O ~ ~OM3
may be detected in the pure sample from Comparison Example 2. 11.5% of the
phosphorus is present in this compound. Together with other phosphonates of
unknown structure, in total 91.0% of the phosphorus is present in
phosphonates. The
majority of the phosphonates present, in this case also, cannot be assigned by
structure. 8.0% of the phosphorus is present as phosphate of the formula (V),
whose
chemical shift is at 2.9 ppm.
A 'H-NMR spectrum of this sample (containing 3-(trimethylsilyl)tetradeutero-
propionic acid sodium salt as internal reference at 0 ppm) shows two triplets
which
predominantly originate from compound (II) where Z = COOH, R' and R2 = H and n
= 1: a triplet at 2.60 ppm (for the -CHZ-COOM group of this compound (II)) and
a
further triplet at 3.16 ppm (for the -CHZ-S03M group of this compound (II)).
In the
region typical of -CH2-S03M from 3 to 3.3 ppm, in addition to said triplet, no
further
signal can be seen. This means that again the great majority of the sulfonic
acid
groups are not present in a compound of the type (I) but in a compound of the
formula (II) where Z = COOM. The -CH2-OH groups of the compounds of the
formula (III) are visible as two triplets at 3.75 to 4 ppm. The molar ratio
determined
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from the signal intensities of the compounds of the formula (II) to compounds
of the
formula (III) is 7.7 (= molar ratio -CH2-S03M / -CH2-OH).
Comparison Example 3
In a similar procedure to Example 5 from US-A-5 221 487, instead of
5-bromovaleric acid, the homologous 4-bromobutyric acid is first reacted with
PCI3
and water, and then with sodium sulfite and KOH. The amounts of the raw
materials
used are multiplied by six compared with this example.
14.0 g (84 mmol) of 4-bromobutyric acid and 3.8 g (210 mmol) of water are
introduced into a multinecked flask equipped with stirrer, dropping funnel,
reflux
condenser and gas outlet tube attached thereto and heated to 40°C. 19.0
g
(138 mmol) of phosphorus trichloride are added dropwise with stirnng at a
temperature of 40 to 50°C in the course of 20 min. After the end of the
addition, the
batch is heated in a 130°C oil bath under reflux for 3 h. The internal
temperature in
this case is approximately 120°C. After 3 h the mixture is allowed to
cool to room
temperature and a solution of 8.9 g (138 mmol) of 86.7a1o pure potassium
hydroxide
and 10.8 g (85.6 mol) of sodium sulfite in 90 g of water are added dropwise
with
cooling at 25 to 30°C in the course of 15 min. Immediately after the
solution is added
dropwise the reaction mixture is alkaline. After heating to 95-100°C,
the pH
decreases to 5 to 6. The mixture is heated for 19 h with stirring to
100°C. The
resultant clear solution (I24.3 g) has an end pH of 4.7.
The 3~P-NMR spectrum (solvent DZO) shows a triplet characteristic of the
-CH2-C(OH)(P03M2)2 group of achiral compounds at 19.1 ppm. Only 6.0% of the
phosphorus is present in this group. In addition, a compound of the formula
P03M' M2
O;P~OH
O// OMs
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may be detected in the 'H-decoupled 3'P-NMR spectrum via two doublets at
15.0 ppm (endocyclic phosphorus) and 17.7 ppm (exocyclic phosphorus) with a
coupling constant 2JPp of 25.4 Hz. 27.0% of the phosphorus is present in this
compound. Together with other phosphonates of unknown structure, in total
90.4%
of the phosphorus is present in phosphonates. The majority of the phosphonates
present cannot be assigned by structure. 9.6% of the phosphorus is present as
phosphate of the formula (V), whose chemical shift is at 0.7 ppm.
Comparison Example 4
In a similar procedure to Example 5 of US-A-5 221 487, 5-bromovaleric acid is
firstly reacted with PC13 and water, and then with sodium sulfite and KOH. In
comparison with the patent example, only the initial amounts of the raw
materials are
multiplied by a factor of six.
15.2 g (84 mmol) of 4-bromovaleric acid and 3.8 g (210 mmol) of water are
introduced in a multinecked flask equipped with stirrer, dropping funnel,
reflux
condenser and gas outlet tube attached thereto and heated to 40°C. 19.0
g
(138 mmol) of phosphorus trichloride are added dropwise with stirring at a
temperature of 40 to 45°C in the course of 20 min. After the end of the
addition, the
reaction mixture is heated to 130°C for 15 min and 120°C for
2.75 h. Reflux occurs
initially from an internal temperature of 110°C. The mixture is
thereafter cooled to
room temperature and a solution of 8.9 g (138 mmol) of 86.7% pure potassium
hydroxide and 10.8 g (85.6 mol) of sodium sulfite in 90 g of water is added
dropwise
with cooling at 25 to 30°C in the course of 15 min. Immediately after
the solution is
added dropwise the reaction mixture is alkaline. After heating to 95-
100°C, the pH
decreases to approximately 6. The mixture is heated for 19 h with stirnng at
100°C.
The resultant solution (129.9 g) has an end pH of 4.3.
The 3'P-NMR spectrum (solvent D20) shows a triplet which is characteristic of
the
-CH2-C(OH)(P03M2)Z group of achiral compounds at 19.0 ppm. 23.1 % of the
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phosphorus is present in this group. Together with other phosphonates of
unknown
structure, in total 87.8°!0 of the phosphorus is present in
phosphonates. The majority
of the phosphonates present cannot be assigned by structure. 8:9% of the
phosphorus
is present as phosphate of the formula (V) whose chemical shift is at 0.7 ppm.
Example 5
Test for calcium tolerance
700 ml of demineralized water are introduced into 1-1 glass flasks and the
inhibitor
solution and 10 ml of a solution containing 183.4 g of CaCl2 ~ 2H20/l is added
with
stirnng. The inhibitor solution used is usually a neutralized solution
containing
10,000 mg/1 of active compound, so that an addition of 5, 10 or 20 ml is
equivalent to
an inhibitor concentration of 50, 100 and 200 mg/l.
The pH of the solution is adjusted to 9.0 by adding sodium hydroxide solution
or
hydrochloric acid and the volume is then made up to 1 1. This solution
contains
500 mg/l of Ca2+.
The sealed flasks are stored for 24 h at 75°C in a circulated air
drying cabinet. After
cooling, the pH is measured (control) and - after resuspending any
precipitated salts
for homogenization - the turbidity of the samples is measured in a
nephelometric
photometer as specified in EN 27027 in a 50 mm cuvette and reported as FNU
(formazine nephelometry unit).
The higher the turbidity values, the more calcium inhibitor salt has
precipitated out.
Low turbidity values therefore correspond to a high calcium tolerance. A high
calcium tolerance is a precondition for effective calcium carbonate inhibition
in
waters having high calcium concentration.
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As shown in Table I, the Ca tolerance of the inventive substance from Example
1
and that of substances described by US-A-5 221 487 from Comparison Examples 3
and 4 are markedly above that of HEDP. The sample which was prepared from
3-bromopropionic acid in an extension of the process proposed in US-A-5 221
487 to
shorter carbon chain lengths (see Comparison Example 1) was somewhat better
than
HEDP, but somewhat worse than the inventive substance from Example 1.
The samples from Comparison Examples 1 and 3 are, in contrast to the other
substances, not stable under the experimental conditions of calcium tolerance
measurement. The pHs fall markedly during measurement.
Table 1
Measurement of calcium tolerance via turbidity experiments
Product Turbidity
in FNU
at an inhibitor
concentration
of
50 mg/1 100 mg/1 200 mgll
Substance Example 1 0 0 0
Comparison: HEDP 88 109 157
Substance Comparison Example
1*
20 40 83
(C3 backbone)
Substance Comparison Example
3*
0 0 0
(C4 backbone)
Substance Comparison Example
4
0 0 0
(C5 backbone)
* marked pH reduction during storage over 24 h at 75°C
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Example 6
Test of scale-inhibiting activity
Three different waters (see Examples 6a) to 6c)), which are supersaturated in
calcium
carbonate, are prepared synthetically from demineralized water by dissolving
salts
and adjusting the pH with sodium hydroxide solution or hydrochloric acid. In
these
waters, the deposition of solids is studied during storage as a function of
added scale
inhibitors of different structure and concentration.
Example 6a)
To test the scale-inhibiting activity, a synthetic tap water of the following
composition is prepared:
100 mg/l of Ca2+ and 12 mg/1 of Mg2+, equivalent to 3 mmol/1 of alkaline earth
metal
ions and a total hardness of 300 ppm of CaC03 or 17° total German
hardness,
195 mg/I of HC03-, equivalent to 3.2 mmol/1 and a carbonate hardness of
9° German
carbonate hardness,
145 mg/1 of Na+, 197 mg/1 of S042- and 177 mg/1 of Cl-.
The total hardness (initial hardness) of this water is determined by titration
with
EDTA.
To this water is added a small amount of inhibitor, so that its concentration
in the test
solution, calculated as free inhibitor acid, is 2, 5, 10 and 25 ppm. The
solution is
adjusted to a pH of 11.0 by adding sodium hydroxide solution (c = 1 mol/1) and
stored in a drying cabinet in a closed glass flask containing a glass rod for
24 h at
60°C. After storage the solution is visually examined for deposited
crystals and
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filtered through a 0.45 pm membrane filter. In the filtrate, the residual
total hardness
is determined by titration with EDTA. The "residual hardness in %" (RH [%]),
listed
in Tables 2 to 4, is calculated using the formula below:
a-b
RH[%] = x 100
c-b
a = residual hardness in the filtrate of the sample under test
b = residual hardness in the filtrate of a blank sample without inhibitor
c = initial hardness
The higher the values of RH[%] in the filtrate, the more effectively is CaC03
precipitation inhibited.
Any deposition of scale, that is of an adherent deposit on the glass surfaces,
is
particularly serious and is indicated in Tables 2 to 4 by a star *.
As shown in Table 2, the formation of scale from the single-strength
concentration of
synthetic water is achieved from an inhibitor concentration of 25 mg/1 only
when the
inventive substance from Example 1 is used and also the substances claimed by
US-
A-5 221 487 from Comparison Examples 3 and 4. HEDP and the substance which
was prepared from 3-bromopropionic acid in extension of the process proposed
there
to shorter carbon chain lengths (see Comparison Example 1), cannot prevent
scale
formation even at an inhibitor concentration of 25 mg/l.
At lower dose (< 10 mg/I of inhibitor), the inventive substance is able to
stabilize a
higher residual hardness than all other comparison substances.
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Table 2
Residual hardnesses in single-strength concentration of synthetic water after
24 h at 60°C and pH 11
Product Residual
hardness
RH [lo)
at active
compound
concentration
of
2 mg/1 5 mgll 10 mg/I 25 mg/l
Substance Example ~* 77* 81* 98
1
Comparison: HEDP not determined49* 76* 78*
Substance Comparison
26* 47* 53* 61*
Example 1 * (C3
backbone)
Substance Comparison
30* 49* 87* 9
6
Example 3* (C4 backbone)
Substance Comparison
33 * 58 * 79 * 99
Example 4 (CS backbone)
* = scale deposition
Example 6b)
In comparison with Example 6a}, a synthetic water having twice the ionic
concentrations is used. The inhibitor-containing test solution is adjusted to
a pH of
9.0 by adding sodium hydroxide solution (c = 1 moll) and stored for 24 h at
80°C.
See Table 3 for the results.
According to Table 3 the minimum inhibitor concentration which still just
prevents
scale deposition from a two-fold concentration of synthetic water is, for the
inventive
substance from Example 1, 5 mg/I, for the substances claimed by US-A-5 221 487
from Comparison Examples 3 and 4, 10 mg/l, for the sample prepared in
extension of
the preparation method described there from Comparison Example 1, 25 mg/I, and
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for HEDP, above 25 mg/l. The inventive substance, at half the dose, therefore
already
achieves the same effect as the substances described there.
Table 3
Residual hardnesses in a two-fold concentration of synthetic water after 24 h
at
SO°C and pH 9
Product Residual
hardness
RH [%]
at active
compound
concentration
of
2 mg/l 5 mg/1 IO mg/1 25 mg/l
Substance Example 92* 100 I00 100
1
Comparison: HEDP 88 * 79 * 79 * 77
Substance Comparison
60* 82* 82* 88
Example 1 * (C3
backbone)
Substance Comparison
67 * 90 * 00
1 97
Example 3* (C4 backbone)
Substance Comparison
72* 91 * 100 100
Example 4 (CS backbone)
* = scale deposition
Example 6c)
In comparison with Example 6a), a synthetic water having four times the ionic
concentrations is used. The inhibitor-containing test solution is adjusted to
a pH of
9.0 by adding sodium hydroxide solution (c = 1 mol/1) and stored for 24 h at
60°C.
See Table 4 for the results.
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Table 4
Residual hardnesses in a four-fold concentration of synthetic water after 24 h
at
60°C and pH 9
Residual
hardness
RH [%J
at active
compound
Product
concentration
of
20 mg/l 50 mg/1 100 mg/1 400 mg/1
Substance Example 54 * 49 * 55 * 86
1
Comparison: HEDP 56 * 54 * 53 * -6 O
Substance Comparison
38* 48* 59* 25 O
Example 1 * (C3
backbone)
Substance Comparison
* *
53 55 77 O 55 O
Example 3* (C4 backbone)
Substance Comparison
53* 54* 58* 9
2
Example 4 (CS backbone)
* = scale deposition, O = sludge formation
According to Table 4, a four-fold concentration of synthetic water is
stabilized at
60°C and pH 9 only at very high inhibitor concentration of at least 400
mg/1 to give a
clear solution, and also only when the inventive inhibitor according to
Example 1 or
the inhibitor according to Comparison Example 4 is used. HEDP and the
substances
from Comparison Examples 1 and 3 lead to sludge formation at this dose. The
negative value for the percentage residual hardness in the 400 mg/1 HEDP test
is
noteworthy. A negative RH [°lo] value means that the total hardness at
the end of the
experiment with inhibitor (in this case 723 ppm of CaC03) is lower than in a
comparison test without inhibitor (750 ppm of CaC03). HEDP in this experiment
acts to precipitate calcium ions. This behavior is in agreement with the low
calcium
tolerance of HEDP (see Table 1 ).
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Example 7
Test for corrosion-inhibiting activity
S To test the corrosion-inhibiting activity, a synthetic cooling water is
prepared which,
compared with Example 6a), has twice the ionic concentrations. In 12 litres of
this
synthetic water, by adding preneutralized inhibitor, an inhibitor
concentration of
30 mg/1 is set. This solution is charged into a 12 litre capacity container in
which four
steel tube rings, which have been degreased by pretreating with acetone, made
of C
steel (St 37) are agitated through the solution on a stirrer at a speed of 0.6
m/s.
During the entire experimental time, 0.4 l/h of a fresh aqueous solution
which, in
contrast to the 12 litres of initial solution, contains 20 mgll of inhibitor,
is added to
the container, and the same flow rate of solution is allowed to flow off via
an
overflow. After 72 h the rings are taken out and pickled with hydrochloric
acid. The
loss of mass of the rings is determined and related to the surface area of the
rings and
the experimental time. From this is calculated an erosion rate of 0.06 mm/yr
for the
substance from Example l, an erosion rate of 0.05 mm/yr for HEDP. In a blank
test
without inhibitor, the erosion rate is 0.17 mm/yr.
