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BACKGROUND OF THE INVENTION
This invention relates to novel compounds useful as sequestrants and scale
and corrosion inhibitors, methods of making such compounds, and methods of
inhibiting scale formation and corrosion of metals therewith.
The utility of materials having the ability to sequester various ions from
aqueous media is well recognized. For example, materials having ability to
sequester calcium ions, iron ions, etc., are extensively utilized in
treating water to prevent formation of scale or building up of
precipitants in boilers, water towers, heat exchangers, etc. Some
materials of this type are empirically found to also be useful as
corrosion inhibitors. That is, they inhibit the corrosion of metals by
water, and especially oxygen-bearing water.
The present invention has special utility in the prevention of the
corrosion of metals which are in contact with circulating water, that is,
water which is moving through condensers, engine jackets, cooling towers,
evaporators or distribution systems, however, it can be used to prevent
the corrosion of metal surfaces in other aqueous corrosive media. This
invention is especially valuable in inhibiting the corrosion of ferrous
metals including iron and steel (also galvanized steel) and nonferrous
metals including copper and its alloys, aluminum and its alloys and brass.
These metals are generally used in circulating water systems.
The major corrosive ingredients of aqueous cooling systems are primarily
dissolved oxygen and inorganic salts, such as the carbonate, bicarbonate,
chloride and/or sulfate salts of calcium, magnesium and/or sodium.
Most commercial water contains iron and alkaline earth metal cations, such
as calcium, barium, magnesium, etc., and several anions such as hydroxide,
bicarbonate, carbonate, sulfate, oxalate, phosphate, silicate fluoride,
etc. When combinations of these anions and cations are present in
concentrations which exceed the solubility of their reaction products
under the conditions of the application (i.e., use), precipitates form
until their reaction solubility product concentrations are no longer
exceeded. For example, when the concentrations of calcium ion and sulfate
ion exceed the solubility of the calcium sulfate, a solid phase of calcium
sulfate will form.
Solubility product concentrations are exceeded for various reasons, among
which are evaporation of the water phase, change in pH, pressure or
temperature, and the introduction of additional ions which form insoluble
compounds with the ions already present in the solution.
As these reaction products precipitate on the surfaces of the
water-carrying system, they form scale. This adherent scale prevents
effective heat transfer, interferes with fluid flow, facilitates corrosive
processes, and harbors microorganisms. The presence of this scale is an
expensive problem in many industrial water systems (e.g., boilers, cooling
towers, evaporators, etc.), oilwells, and the like, causing delays and
shutdowns for cleaning and removal.
Scale-forming compounds can be prevented from precipitating by inactivating
their cations with chelating or sequestering agents, so that the
solubility of their reaction products is not exceeded. Generally, this
requires many times as much chelating or sequestering agent as cation, and
these amounts under certain conditions are not always desirable or
economical.
More than 25 years ago it was discovered that certain inorganic
polyphosphates would prevent such precipitation when added in amounts less
than the concentrations needed for sequestering or chelating. See, for
example, Hatch and Rice, "Industrial Engineering Chemistry", vol. 31,
pages 51 and 53; Reitmeier and Buehrer, "Journal of Physical Chemistry",
vol. 44, No. 5, pages 535 and 536 (May 1940); Fink and Richardson U.S.
Pat. No. 2,358,222; and Hatch U.S. Pat. No. 2,539,305, all of which are
incorporated herein by reference. For sequestration, the mole ratio of
precipitation inhibitor equivalents to scale forming cation is usually 1:1
or greater (2:1, 3:1, etc.). These ratios are referred to as
stoichiometric. Substoichiometric amounts would include all mole ratios of
precipitation inhibitor equivalent to scale forming cation that are less
than the level required for sequestration; this phenomenon is known in the
water treating art as the "threshold" effect.
It is to be understood that the term "threshold" as utilized herein refers
to the chemical and/or physical phenomenon that less than stoichiometric
quantities of the particular precipitation inhibitor can effectively
prevent the precipitation of various metallic ions such as calcium, iron,
copper and cobalt and/or alter those crystals formed such that the
adherence to surfaces is substantially reduced. In other words, the
threshold treatment of water is that technique by means of which less than
stoichiometric quantities of the treating agent are added to interfere
with the growth of crystal nuclei and thereby prevent the deposition of
insoluble deposits.
Consequently, precipitation inhibitors which function as threshold agents
as well as sequestering agents and corrosion inhibitors represent an
advancement in the art and are in substantial demand.
SUMMARY OF THE INVENTION
It is an object of this invention to provide novel compounds useful as
water treating agents.
Another object of this invention is to provide a method for manufacturing
such compounds.
Another object of this invention is to provide methods for inhibiting the
precipitation of metal ions from aqueous solution.
A still further object of this invention is to provide precipitation
inhibitors which are effective as threshold scale inhibitors in aqueous
solutions in less than stoichiometric amounts.
A further object of this invention is to provide new corrosion inhibiting
methods, especially for metals in contact with aqueous corrosive media
including cooling waters.
These and other objects will be better understood from the following
detailed description.
The novel water treating compounds of the present invention contain
multiple tertiary-substituted nitrogen atoms and multiple phosphonate
groups. These compounds are imino ethylimino methyl phosphonates whose
manufacture and utilities are more fully set forth in the description of
preferred embodiments below.
DESCRIPTION OF PREFERRED EMBODIMENT
The novel compounds of this invention are represented by the formula
##EQU2##
wherein R is --CH.sub.2 PO.sub.3 M.sub.2 or --CH.sub.2 CH.sub.2 N(CH.sub.2
PO.sub.3 M.sub.2).sub.2 and M is hydrogen, metal ions, ammonium ions,
alkylammonium ions or mixtures thereof.
In the above formula M can be alike or unlike and is from the group metal
ions and hydrogen or any cation which will yield sufficient solubility for
the desired end use. The aforementioned metal ions are from the group of
metals which includes, without limitation, alkali metals such as sodium,
lithium and potassium; alkaline earth metals, such as calcium and
magnesium; aluminum; zinc, cadmium; manganese; nickel, cobalt, cerium;
lead; tin; iron; chromium; copper; gold; and mercury. Also included are
ammonium ions and alkylammonium ions. In particular, those alkylammonium
ions derived from amines having a low molecular weight, such as below
about 300, and more particularly the alkyl amines, alkylene amines, and
alkanol amines containing not more than two amine groups, such as ethyl
amine, diethyl amine, propyl amine, propylene diamine, hexyl amine,
2-ethylhexylamine, N-butylethanol amine, triethanol amine, and the like
are the preferred amines. It is to be understood that the preferred metal
ions are those which render the compound a water-soluble salt in
concentrations sufficient for the desired applications, such as the alkali
metals, as well as the water-soluble salts from ammonium, alkylammonium
and alkanol amine ions.
Exemlary compounds of the present invention include nitrilo tris[ethylimino
bis(methyl phosphonic acid)], phosphonomethylimino bis[ ethylimino
bis(methyl phosphonic acid)] and the corresponding octa and hepta alkali
metal, ammonium and alkylammonium salts of the acids such as octasodium,
octaammonium and octamethylammonium nitrilo tris[ethylimino bis(methyl
phosphonates)], heptapotassium, heptaammonium and heptaethylammonium
phosphonomethylimino bis[ethylimino bis(methyl phosphonates)]; as well as
mixed salts thereof such as dihydrogen hexasodium and trihydrogen
pentaammonium nitrilo tris[ ethylimino bis(methyl phosphonates)] and
dihydrogen pentapotassium and trihydrogen tetraammonium
phosphonomethylimino bis[ethylimino bis(methyl phosphonates)]. Other mixed
salts or partial salts are likewise included in the above general formula.
In general, the compounds of the present invention are prepared by reacting
together an (a) phosphorus source from the group orthophosphorous acid and
a combination of PCl.sub.3 and H.sub.2 O, (b) formaldehyde and (c) an
amine of the formula
##EQU3##
wherein R' is hydrogen or --CH.sub.2 CH.sub.2 NH.sub.2.
It has been found that by forming a mixture of the above-described
phosphorus source, formaldehyde and an amine of Formula II and subjecting
the mixture to reaction conditions, compounds having multiple N--C--P
linkages can be formed.
The amines falling within Formula II are described and prepared according
to processes outlined in "Formaldehyde", J. F. Walker, published by
Reinhold Publishing Company, New York (1964) pages 240-243 and in
"Chemistry of Organic Cyanogen Compounds", V. Migrdichian, published by
Reinhold Publishing Company, New York (1947) at pages 153-157, both of
which are incorporated herein by reference. More specifically these amines
can be prepared by the reaction of formaldehyde, ammonia and hydrogen
cyanide by a stepwise reaction to produce the iminodiacetonitrile and
nitrilotriacetonitrile and thereafter reducing the nitrile groups to amino
groups by known procedures. For example, nitrilotriacetonitrile is
produced by the above reaction and then reduced by hydrogenation to
produce the desired amine, nitrilotriethyleneamine. It is understood that
the amines falling within Formula II can be used in their (a) technical
grade form, (b) chemically pure form, or (c) crude form which is obtained
directly from the synthesis of the amine.
The formaldehyde reactant can be employed in any desired form, the more
preferable being paraformaldehyde or formalin solutions.
For ease of description, orthophosphorous acid will generally be described
hereinafter as the phosphorus source reactant. Orthophosphorous acid is
available commercially.
It can be utilized in the processes of the present invention either as the
acid, itself, or in the form of its salt, such as its mono- or diammonium
salts, and mono- or dialkali metal salts. When orthophosphorous acid is
utilized in the salt form, usually an amount of a supplementary acid
sufficient to effectively convert the salt form into the more reactive
orthophosphorous acid is used.
It is to be understood that while H.sub.3 PO.sub.3 is used in this form,
the individual ingredients PCl.sub.3 and H.sub.2 O which react to make
H.sub.3 PO.sub.3 can be used separately, e.g., added at different points
of the process operation, or added simultaneously, i.e., two individual
feed streams at the same time.
Ordinarily, for at least one from each of the reacting materials, i.e.,
items (a), (b) and (c) above, to undergo an interreaction to form one of
the imino ethylimino methyl phosphonates they must simply be mixed
together in certain relative proportions (described in more detail below),
preferably in an acidic aqueous medium, and ordinarily subjected to an
elevated temperature for a sufficient period of time to achieve the
desired reaction. At room temperature, the rate of interreaction of these
materials is slow, but where time is not a factor, the reaction can be
carried out at 25.degree.C. or lower. Increasing the temperature generally
results in increasing the rate of the desired reaction, so that, usually,
if the temperature of a mixture of phosphorous acid, amine of Formula II
above, and formaldehyde is above about 70.degree.C., the rate of their
interreaction is sufficiently high so that conventional mixing and
handling equipment can be utilized to produce the reaction product
continuously and at a commercially practically cost, if desired. It has
also been found that increasing the reaction temperature for the processes
of this invention in the temperature range above about 75.degree.C. up to
200.degree.C. (the latter being the spontaneous decomposition temperature
of orthophosphorous acid at atmospheric pressure) results in a fairly
rapid increase in the rate of the desired reaction. Thus, for practical
purposes, it is preferred that reaction temperature for the formation of
the desired reaction product wherein orthophosphorous acid is utilized
according to the processes of this invention, be above about 85.degree.C.
Temperatures within this preferred range, i.e., about 85.degree.C. to
about 200.degree.C., can readily be maintained by refluxing the aqueous
reaction mixture at, above or below atmospheric pressure until the desired
reaction has been completed.
It is believed surprising that the pH of the reaction medium has apparently
an important influence upon the rate of the desired reaction. For example,
it has been found that the rate of the desired reaction in mixtures
containing the amine formaldehyde, and orthophosphorous acid in the molar
ratio, respectively, of about 1:6:6 having a pH above about 4 is low. One
possible reason for the low rate of the desired reaction in reaction media
having pH's above about 4 is that apparently in such systems the competing
oxidation of orthophosphorous acid to orthophosphoric acid takes
precedence over the desired interreaction of orthophosphorous acid with
formaldehyde and the amine. Actually, it is preferred that the pH of the
reaction mixture of orthophosphorous acid plus formaldehyde plus amine,
and usually at least some water, be below about 4 and preferably about 2
in order to achieve optimum results in the practice of the present
invention. When one of the salts of orthophosphorous acid is utilized as a
raw material, and when the ratio of reactive amine to orthophosphorous
acid in the reaction mixture is relatively high, the "natural", or usual
pH of the reaction mixture or reaction medium is generally not within the
preferred range. However, the pH of the reaction medium can be adjusted
into the most effective range by adding to the system any of the
conventional acids having the ability to lower the pH of the reaction
medium. For example, hydrochloric, sulfuric, hydrobromic, phosphoric, and
sulfonic acids, as well as many others can be utilized for this purpose.
Another example of providing a low pH and also a halide ion for a
catalyst, hereinafter discussed, is the use of a halide salt and an acid.
These two ingredients alone accomplish the desired result; however, they
may react together to form a salt and a hydrogen halide which also
achieves the end result. For example, the use of sodium chloride and
sulfuric acid results in the formation of sodium bisulfate and hydrogen
chloride.
Ordinarily the desired reaction will be fairly complete, under optimum
reaction conditions in a resonable and practical period of time, for
example, in less than about 3 hours, generally from about several minutes
to about 3 hours, and fairly pure reaction products are produced.
While it is not essentially that water must be present in the reaction
medium, it has been found that the presence of at least some water
contributes substantially to such factors as keeping the reactants in
solution, ease of handling of the reaction medium, ease of maintaining the
desired reaction temperature by refluxing, ease of maintaining adequate
heat transfer within the reaction mixture, decreasing the viscosity of the
reaction products, etc. Thus, it is desirable that at least about 5 weight
percent of water, based on the total weight of the raw reaction materials
charged into the reaction mixture, and preferably at least about 15 weight
percent of water be present in the reaction mixture before it has been
exposed to temperatures above about 90.degree.C. for any extended period
of time. Additional water can also be added to the reaction medium from
time to time if and as it is needed.
The processes of this invention can be carried out with conventional,
readily available chemical processing equipment. For example, a
conventional heated glass-lined mixing and reaction vessel fitted with a
reflux condenser and a fairly efficient stirrer can be advantageously
utilized in practicing any of the preferred embodiments of the invention
described in the examples below.
The orthophosphorous acid, amine, and formaldehyde can be intermixed in
several manipulative manners without detracting appreciably from the
benefits that can be derived from the invention. For example, they can be
simply poured together in the appropriate proportions, discussed below,
into a mixing vessel, blended, and then heated to the reaction
temperature. Or th ingredients can be warmed individually, before they are
intermixed. The amine can be utilized per se or in the form of its salts
such as the HCl salt form thereof. Sometimes it is convenient and
desirable to intermix the amine with the phosphorous acid before they are
heated very much above ambient temperatures.
Usually significantly better yields of the desired product, based on the
amount of formaldehyde charged into the reaction vessel, can be attained
if the formaldehyde is added slowly, e.g., over a period of from about 10
minutes to about 3 hours, to the mixture of orthophosphorous acid and
amine while the temperature of said mixture is within the desired range.
The compounds of the present invention result from reacting (a) the
phosphorus source, e.g., orthophosphorous acid and (b) formaldehyde with
(c) the starting amine in a ratio of at least 5 to 6 moles, respectively,
of (a) and (b) for each mole of (c) the starting amine, depending on
whether such amine contains 5 or 6 amino hydrogen atoms. An excess of
orthophosphorous acid from about 1 to 100% by weight can be utilized in
such process. Excess formaldehyde can also be utilized to advantage.
However, if the molar ratio of orthophosphorous acid and formaldehyde to
the starting amine is raised above 5:5:1 or 6:6:1, respectively, resulting
in an excess of formaldehyde or orthophosphorous acid, depending on the
free amino hydrogen atoms in said amine, there may result side reaction
products. Thus, for the production of relatively pure desired reaction
products, it is preferred that the molar ratio of the starting amine to
orthophosphorous acid in the reaction mixture be about 1:5 or 1:6,
respectively, and that the molar ratio of the starting amine to
formaldehyde in the reaction mixture be about 1:5 or 1:6, respectively,
depending on the amino hydrogen content of said starting amine.
One reason why yields of the desirable products are generally not 100% of
theory in the processes of this invention is that, in addition to the
desired N--C--P linkage-forming reaction, the orthophosphorous acid also
undergoes an oxidation reaction to form orthophosphoric acid under the
conditions that usually favor the desired reaction. Since in most
instances the presence of orthophosphoric acid in the final products is
not particularly detrimental, the inclusion of excess orthophosphorous
acid into the reaction medium is generally all that is necessary to make
up for this "loss" of orthophosphorous acid from the desired reaction.
However, it has been discovered that the presence of at least a catalytic
amount of halide ions in the reaction mixture of amine, orthophosphorous
acid, formaldehyde, and usually water inhibits the oxidation of
orthophosphorous acid to orthophosphoric acid, and thus makes it possible
to produce relatively more of the desired final product from a given
reaction mixture than could otherwise be produced in the absence of halide
ions therefrom. Apparently, any simple halide ion can be utilized to
accomplish the inhibition described above, although for economic purposes
chloride is preferred. The halide ion can apparently be introduced into
the reaction mixture in any way whatever without detracting significantly
from the benefits that can be derived from practicing the invention,
provided it is introduced thereinto before the temperature of the reaction
mixture has been heated to or held at about 70.degree.C. for more than a
few minutes. For example, it can be added in the form of a hydrohalide
acid such as HCl, HBr, HI, etc., or as an inorganic salt, such as NaCl,
KCl, NaBr, CaCl.sub.2 and the like. Another convenient way is as the
hydrogen chloride salt of the amine. As mentioned earlier, a mixture of a
nonhalide containing acid and halide salt can be used to achieve the
desired end result. Even very small amounts of halide ions in the reaction
mixture have been found to inhibit the oxidation of orthophosphorous acid
to some extent. Excellent results can be accomplished when there is
utilized in the reaction mixture between about 0.01 and about 10, and
preferably at least about 0.5 weight percent of halide ions. Halide ions
in excess of these amounts can be present without any apparent detrimental
effects on the processes of the invention. However, as a practical matter,
generally, not more than about 20 weight percent of halide ions is
utilized in the processes.
The acid and salt forms of the imino ethylimino methyl phosphonates falling
within Formula I of the present invention have unique utility for treating
water or aqueous systems and function as sequestering agents, as threshold
agents and as corrosion inhibitors. It is to be understood that the term
threshold as utilized herein refers to the chemical and/or physical
phenomenon that less than stoichiometric quantities of the particular
treating agent can effectively prevent the precipitation and/or alter the
crystal forms of various salts of metallic ions such as calcium, iron,
copper and cobalt. In other words, the threshold treatment of water is
that technique by means of which less than stoichiometric quantities of
the treating agent are added to interfere with the growth of crystal
nuclei and thereby prevent the deposition of insoluble deposits.
The imino ethylimino methyl phosphonates of the present invention have
utility for inhibition of the precipitation of metal ions from aqueous
solutions, and/or alteration of those crystals formed such that the
adherence to surfaces is substantially reduced. Typical applications also
include liquid soaps and shampoos; bar soaps; scouring textiles, kier
boiling; textile bleaching; metal cleaning compounds; rubber and plastics
trace metal contamination (compounding and polymerization); pulp and paper
trace metal contamination; saline water; oral compositions as anticalculus
agents; photographic developers; hair bleaching and dyeing operations;
stabilizing hydrogen peroxide solutions; brine solutions; brackish water;
and squeeze treatment of producing oil wells.
The amount of the precipitation inhibitor necessary to be effective varies
with, inter alia, the type and amount of problem metal ions, pH
conditions, temperature and the like. When using substoichiometric or
threshold treatment amounts, the preferred mole ratio of the precipitation
inhibitor to the scale forming cation salt is from about 1:1.5 to about
1:10,000 with the concentration of precipitation inhibitor in the system
being from about 0.1 to 500 ppm. When using sequestering amounts, i.e., at
least stoichiometric quantities; the preferred mole ratio is from about
1:1 to 2.5:1.
The imino ethylimino methyl phosphonates of the present invention
furthermore have utility for inhibiting corrosion of metal surfaces in
contact with aqueous corrosive media, and particularly oxygen-bearing
waters. It has been found that to effectively inhibit corrosion, at least
3 ppm, preferably from about 10 ppm to about 500 ppm. More preferably from
about 10 to about 150 ppm of the imino ethylimino methyl phosphonate
should be utilized in the corrosive medium. It is to be understood that
greater than 500 ppm of these phosphonates can be used if desired so long
as the higher amounts are not detrimental to the water system. Amounts as
low as 1 ppm are found to be effective.
The corrosion inhibitors of the present invention are effective in both
acidic or basic corrosive media. The pH can range from about 4 to about
12. For example, nitrilo tris[ethylimino bis(methyl phosphonic acid)],
when used from about 3 to about 100 ppm is an effective corrosion
inhibitor in a corrosive medium where the pH is from about 4 to about 12.
In cooling towers the water system is generally maintained at a pH of from
about 6.5 to 10.0, and most often at a pH of from about 6.5 to 8.5. In all
such systems the inhibitors of the present invention are effective.
In addition to the utilization of the imino phosphonates of the present
invention per se as corrosion inhibitors, it has been found that a
cooperative effect exists in corrosion inhibition between these
phosphonates and the zinc ion or chromates or dichromates. That is, the
use of the imino phosphonates with the zinc ion or a chromate or
dichromate more effectively inhibits corrosion than does an equal
concentration of the imino phosphonate or the zinc or chromate alone. The
zinc ion is preferably used in the same concentration as the imino
phosphonate, e.g., a suitable corrosion inhibitor may consist of 50 ppm of
zinc ion plus 50 ppm of an imino phosphonate. It is to be understood that
the present invention also encompasses a corrosion inhibiting process and
corrosion inhibition compositions utilizing mixtures of the imino
phosphonates of this invention and a zinc-containing material, i.e., a
zinc compound soluble in the corrosive media, which is capable of forming
the zinc ion in an aqueous medium.
When a corrosion inhibiting composition is prepared from the two above
materials there may conveniently be formed a dry composition thereof which
may be later dissolved in water or fed directly to the aqueous system
containing the metals to be protected. The maximum effect can be achieved
by a composition of from about 20 to 90 percent by weight of the imino
phosphonate and from about 10 to 80 percent by weight of a zinc compound
soluble in the aqueous medium. Preferably such composition comprises from
about 40 to about 80 percent by weight of the imino phosphonate and from
about 20 to 60 percent by weight of the soluble zinc compound.
A combination of about 3 to 100 ppm of an imino phosphonate of this
invention and about 2 to 100 ppm zinc ion will inhibit corrosion in most
water systems. The most preferred concentration range is from about 5 to
25 ppm of the imino phosphonate and about 5 to 25 ppm zinc ion. It is
understood, however, that those concentrations are not limitative of the
present invention.
The above-described cooperative effect is likewise realized with a chromate
or dichromate, which may include any compound of hexavalent chromium
soluble in the corrosive aqueous media, and preferably is an alkali metal
or ammonium chromate or dichromate or chromic acid. Corrosion in most
water systems can be inhibited by adding from 1 to 100 ppm of a imino
phosphonate of this invention and from about 1 to about 100 ppm of a
chromate or dichromate, preferably from about 5 to 25 ppm of a phosphonate
and about 5 to 25 ppm chromate or dichromate. Larger or smaller amounts
can be used if desired.
In corrosion inhibiting compositions the most effective compositions
comprise mixtures of from about 1 percent to about 60 percent, and
preferably from about 10 percent to about 40 percent of a water-soluble
chromate or dichromate, based on the combined weights of the chromate or
dichromate and the imino phosphonate of this invention.
It has also been found that compositions of imino phosphonates, zinc ion
and chromate or dichromate are useful in inhibiting the corrosion of
metal; that is all three components are cooperatively effective. The
coaction of zinc and dichromates described in U.S Pat. No. 3,022,133,
incorporated herein by reference, remains unaffected in the presence of
the imino phosphonates of this invention.
Where the water systems are in contact with various metals such as steel
and copper or copper-containing metals, it is frequently desirable to use,
along with the imino phosphonate, either alone or in combination with zinc
and/or chromium ions, a 1,2,3-triazole or a thiol of a thiazole, an
oxazole or an imidazole such as are known in the art to inhibit the
corrosion of copper. These azoles are likewise effective with the imino
phosphonates of the present invention. The amounts of the azoles used
depend on the particular aqueous systems. Generally concentrations of
about 0.05 to 5 ppm thiol or triazole with about 3 to 100 ppm imino
phosphonate and up to about 100 ppm zinc ion are satisfactory, preferably
concentrations of from 0.5 to 2 ppm of the azole, about 5 to 25 ppm imino
phosphonate and from about 5 to 25 ppm zinc ion.
It is within the scope of the present invention that the imino ethylimino
methyl phosphonates of the present invention may also be used in aqueous
systems which contain inorganic and/or organic materials (particularly,
all ingredients or substances used by the water-treating industry), with
the proviso that such materials do not render the imino phosphonates
substantially ineffective for their end purpose.
These organic and inorganic materials include, without limitation,
polycarboxylates, particularly those whose molecular weights are from
about 2000 to about 20,000 and from about 20,000 to about 960,000;
antifoam agents; water soluble polymers such as polyacrylic acid,
polyacrylamide, partially hydrolyzed acrylamide and the like; tannins;
lignins; deaerating materials; polymeric anhydrides (such as polymaleic
anhydride); and sulfonated lignins. Other materials which can be used with
said inhibitors include, for example, surface active agents,
acetodiphosphonic acids, inorganic phosphates including orthophosphates,
molecularly dehydrated phosphates and phosphonates, polyfunctional
phosphated polyol esters, calcium and magnesium salts such as calcium or
magnesium chlorides, sulfates, nitrates and bicarbonates and inorganic
silicates. Furthermore, other scale and precipitation inhibitors such as
amino tri(methylene phosphonic acid) may be used in combination with the
inhibitors of the present invention. For examplary purposes only, these
other precipitation inhibitors are described in U.S. Pat. Nos. 3,234,124;
3,336,221; 3,393,150; 3,400,078; 3,400,148; 3,434,969; 3,451,939;
3,462,365; 3,480,083; 3,591,513; 3,597,352 and 3,644,205, all of which
publications are incorporated herein by reference. Other corrosion
inhibitors can be used in combination with the imino phosphonates
including those described in U.S. Pat. Nos. 3,483,133; 3,487,018;
3,518,203; 3,532,639; 3,580,855; and 3,592,764, all of which are
incorporated herein by reference.
The following examples are included to illustrate the practice of the
present invention and the advantages provided thereby but are not to be
considered limiting. Unless otherwise specified, all parts are parts by
weight and all temperatures are in degrees centigrade.
EXAMPLE I
Into a 500 milliliter flask equipped with a water condenser and dropping
funnel are charged approximately 99 grams (0.6 mole) of 49.9%
orthophosphorous acid (and which contained 9.4 grams of HCl) and 5.2 grams
of 37% hydrochloric acid. The total moles of HCl is 0.4. The resultant
mixture in the 500 milliliter flask is then heated by the addition thereto
of approximately 14.6 grams (0.1 mole) of nitrilo triethyleneamine in its
technical grade form. This amine is added over a period of approximately
10 minutes at the end of which time, the reaction mass has a temperature
of about 75.degree.C. The reaction mass is then heated for 20 minutes to
bring it up to boiling thereby obtaining a homogeneous, clear solution
having a boiling point of approximately 112.degree.C.
The resultant clear solution in the flask is maintained at boiling, and
over a period of approximately 2 hours, approximately 27 grams (0.66 mole)
of paraformaldehyde is added. At the end of the 2 hour period, the
reaction mixture, which is a clear solution, is held at boiling with
reflux for an additional 30 minutes and then is cooled to 25.degree.C. At
25.degree.C., the solution is found to be clear with an amber color. One
hundred forty-four grams of this solution is obtained with about 49% by
weight thereof being the desired nitrilo tris phosphonic acid. Analysis of
this solution by p.sup.31 Nuclear Magnetic Resonance spectra (NMR) shows
the presence of N--C--P linkage. After precipitation and reslurrying of a
50 gram portion of the solution and drying overnight there is obtained 24
grams of tan granular material. This material subjected to elemental
analysis is identified as nitrilo tris[ethylimino bis(methyl phosphonic
acid)], having the following structural formula:
##EQU4##
EXAMPLE II
Into a 500 milliliter flask equipped with a water condenser and dropping
funnel are charged approximately 99 grams (0.6 mole) of 49.9%
orthophosphorous acid (and which contained 9.4 grams of HCl) and 5.2 grams
of 37% hydrochloric acid. The total moles of HCl is 0.4. The resultant
mixture in the flask is then heated by the addition thereto of
approximately 10.3 grams (0.1 mole) of imino diethyleneamine HN(CH.sub.2
CH.sub.2 NH.sub.2).sub.2. This amine is added over a period of
approximately 8-10 minutes at the end of which time, the reaction mass has
a temperature of about 70-75.degree.C. The reaction mass is then heated
for about 20 minutes to bring it up to boiling thereby obtaining a
homogeneous, clear solution having a boiling point of approximately
110-115.degree.C.
The resultant clear solution in the flask is maintained atboiling, and over
a period of approximately 2 hours, approximately 22 grams (0.66 mole) of
paraformaldehyde is added. At the end of the 2 hour period, the reaction
mixture, which is a clear solution, is held at boiling with reflux fo | | |
