Method of treating water to inhibit corrosion and diminish mineral deposition

What is disclosed is a method for treating water to inhibit corrosion and diminish mineral deposition using certain cationic silanes in a neutral or basic pH environment. An example of the method is the use of (CH.sub.3 O).sub.3 Si(CH.sub.2).sub.3 N.sup..sym. (CH.sub.3).sub.2 C.sub.18 H.sub.37 Cl.sup.- in a humidifier unit.

BACKGROUND OF THE INVENTION 
This invention relates to a method of treatment of water in order to 
inhibit corrosion and diminish mineral deposition. 
Typically, if mineral deposition can be diminished or eliminated, the 
advent of corrosion can also be diminished. Thus, this invention deals 
primarily with the elimination of, or the significant decrease of, mineral 
deposition from aqueous systems. Minerals which are easily deposited from 
water can cause problems. For example, it is not difficult to remember 
mineral build-up on leaky water faucets, boiler tubes, cooling towers, 
humidifiers, water pipes, air conditioners, fish tanks, washing machines, 
sinks, auto radiators, hoses, cisterns and many other water systems, 
especially those systems which operate by losing some water to the 
atmosphere which causes the mineral contained in the water to concentrate. 
Everyone has experienced the distasteful sight of the buildup of such 
mineral deposits and, aside from the aesthetics, many have experienced the 
lack of performance of certain aqueous systems because of the deposits of 
such minerals, for example, the diminished capacity of heat exchangers. 
It seems that one way to prevent the deposition of such minerals is to 
eliminate such minerals from the water, but this could become very time 
consuming and costly. Moreover, quite often, such minerals are purposely 
added to aqueous systems to control corrosion; therefore, total 
elimination of the minerals is not the answer either. A better method, and 
a more economical method, appears to be the stabilization of the minerals 
in the aqueous systems such that they do not readily deposit from the 
aqueous systems. 
Many compounds have been suggested for this use. Such compounds include 
those which can be added to aqueous systems and which react with 
depositable minerals or, in the case of corrosion control, such compounds 
are reacted with the minerals and added to aqueous systems. Such compounds 
are, for example, shown in U.S. Pat. No. 3,121,692 as being useful in 
antifreeze formulations. Disclosed therein are aminofunctional siliconates 
or derivatives of such siliconates wherein the nitrogen atom is 
substituted with hydrocarbon groups containing hydroxyl, amido, ester, 
hydrocarbonoxy or cyano functionalities. Another patent, U.S. Pat. No. 
3,198,820, deals with copolymers of soluble silicates and carboxylic acid 
functional siliconates, which siliconates may be monocarboxylic acid 
functional or polyacid functional. U.S. Pat. No. 3,234,144 discloses a 
process for inhibiting corrosion using amine functional siloxanes. U.S. 
Pat. No. 3,341,469 deals with a process for inhibiting corrosion using a 
copolymer of soluble silicate and dihydroxyl or polyether functional 
siliconates. Other disclosures of similar applications appear in U.S. Pat. 
No. 4,370,255, issued Jan. 25, 1983 (alkali siliconates of silylalkyl 
phosphonates); U.S. Pat. No. 4,344,860, issued Aug. 17, 1982 
(carboxyalkylsubstituted nitrogen or sulfur-containing siliconates) and 
U.S. Pat. 4,352,742, issued Oct. 5, 1982, U.S. Pat. No. 4,354,002, issued 
Oct. 12, 1982 and U.S. Pat. No. 4,362,644, issued Dec. 7, 1982 (arylalkyl 
and aliphatic silicone sulfonate-silicate copolymers). Further, there is 
disclosed in U.S. Pat. No. 3,723,333, issued Mar. 27, 1973, the use of 
compounds having the formula 
##STR1## 
and a water-soluble, complex-forming compound which contains at least one 
phosphonate or N-dimethylenephosphoric acid group, wherein X is OH or 
NH.sub.2 and R is an alkyl radical of from 1 to 5 carbon atoms. 
Finally, in U.S. Pat. No. 4,418,195, issued Nov. 29, 1983, there is 
disclosed the use of novel thiazines as corrosion inhibitors. 
None of the above references, however, describe the compositions or the 
process of this invention. 
THE INVENTION 
This invention consists of several aspects of the same concept and one 
aspect is a method of treating water in order to inhibit corrosion and 
diminish mineral deposition. Such a method comprises adding to the water, 
in an amount sufficient to inhibit corrosion and diminish mineral 
deposition, an organosilane having a general formula selected from the 
group consisting of 
##STR2## 
wherein, in each formula, R is an alkyl radical of 1 to 4 carbon atoms or 
hydrogen; a has a value of 0, 1 or 2; R' is an alkyl radical of 1 to 4 
carbon atoms; R" is an alkylene group of 1 to 4 carbon atoms; R"', R"" and 
R.sup.v are each independently selected from a group consisting of alkyl 
radicals of 1 to 18 carbon atoms, --CH.sub.2 C.sub.6 H.sub.5, --CH.sub.2 
CH.sub.2 OH, --CH.sub.2 OH, and --(CH.sub.2).sub.x NHC(O)R.sup.vi, wherein 
x has a value of from 2 to 10 and R.sup.vi is a perfluoroalkyl radical 
having from 1 to 12 carbon atoms; X is chloride, bromide, fluoride, 
iodide, acetate or tosylate. 
The organosilanes of this invention are known in the art. It should be 
noted that generically, these materials are quaternary ammonium salts of 
silanes. Such silanes, as well as their method of preparation, are 
disclosed in U.S. Pat. No. 4,259,103; issued Mar. 31, 1981. Also, Canadian 
Patent No. 1,010,782 discloses such silanes. 
Certain of the organosilanes used in this invention have been used to treat 
solid substrates in order to render the surfaces of such substrates 
antimicrobial. For example, in U.S. Pat. No. 3,817,739, issued June 18, 
1974, there is shown the use of a silane such as (CH.sub.3 O).sub.3 
Si(CH.sub.2).sub.3 N.sup.+ (CH.sub.3).sub.2 C.sub.18 H.sub.37 Cl.sup.- to 
treat solid substrates such as glass fiber and then the use of the treated 
glass fiber as a filter for aqueous systems. However, in that disclosure, 
at column 2, lines 1 to 5, it is noted that the treatment does not get 
into, at least does not stay, in the aqueous system. 
For purposes of this invention, the silanes can be used neat or they can be 
used in solvent or aqueous-solvent solutions. When solvents other than 
water soluble or water miscible solvents are used, they should be used 
sparingly. 
The silane is added to the water system to be treated and allowed to mix 
and disperse. It is believed that the silanes stabilize the minerals in 
the water system and keep them soluble, or at least dispersible, such that 
the minerals do not readily deposit on the surfaces with which they come 
in contact. Preferred for use in this invention are aqueous solutions of 
the silanes, without any solvents. 
The benefits of this invention are realized when the water to be treated is 
neutral or alkaline. In a neutral or alkaline aqueous system, the silanes 
of this invention are capable of increasing the time in which the water 
system can be operated without having to stop the system and refurbish it 
with fresh water. In the event that an aqueous system is shut down, the 
treated water removed, and the system refilled with fresh water, it is 
necessary that the fresh water be treated by the process of this invention 
in order to inhibit corrosion and diminish mineral deposits. 
The system to be treated can be neutral or alkaline when the silane is 
added or it can be rendered neutral or alkaline after the silane is added, 
just as long as the aqueous system operates in the neutral or alkaline pH 
range. 
The amount of the silane that is used in this invention is dependent on the 
nature of water being treated, that is, the amount of mineral in the 
water. Generally, the silanes are useful at a few parts per million 
concentration to a few weight percent concentration. Most preferred is the 
use of 0.1 to 20 mole percent of the silane based on the depositable 
minerals in the water system to be treated. Having an excess of the silane 
present over this amount does not appear to be detrimental but can be 
wasteful in some cases. 
R in the silanes of this invention are alkyl groups of 1 to 4 carbon atoms. 
Thus, useful as R in this invention are the methyl, ethyl, propyl and 
butyl radicals. R can also be hydrogen thus indicating the silanol form, 
i.e. the hydrolyzate. The value of a is 0, 1 or 2 and R' is an alkyl 
radical of 1 to 4 carbon atoms as illustrated for R above. 
R" for purposes of this invention is an alkylene group of 1 to 4 carbon 
atoms. Thus, R" can be alkylene groups such as methylene, ethylene, 
propylene, and butylene. R"', R"", and R.sup.v are each independently 
selected from a group which consists of alkyl radicals of 1 to 18 carbons, 
--CH.sub.2 C.sub.6 H.sub.5, --CH.sub.2 CH.sub.2 OH, --CH.sub.2 OH, and 
--(CH.sub.2).sub.x NHC(O)R.sup.vi. x has a value of from 2 to 10 and 
R.sup.vi is a perfluoroalkyl radical having from 1 to 12 carbon atoms. X 
is chloride, bromide, fluoride, iodide, acetate or tosylate. 
Preferred for this invention are the silanes of the general formula 
##STR3## 
wherein R is methyl or ethyl, R' is an alkyl radical of 1 to 4 carbon 
atoms, a has a value of zero; R" is propylene; R"' is methyl or ethyl; R"" 
and R.sup.v are selected from alkyl groups containing 1 to 18 carbon atoms 
wherein at least one such group is larger that eight carbon atoms and X is 
either chloride, acetate or tosylate. 
Most preferred for this invention are those silanes having the formula 
EQU (CH.sub.3 O).sub.3 Si(CH.sub.2).sub.3 N.sup..sym. (CH.sub.3).sub.2 C.sub.18 
H.sub.37 Cl.sup.- and (CH.sub.3 O).sub.3 Si(CH.sub.2).sub.3 -N.sup..sym. 
CH.sub.3 (C.sub.10 H.sub.21).sub.2 Cl.sup.-. 
As indicated above, most of these silanes are known from the literature and 
methods for their preparation are known as well. See, for example, U.S. 
Pat. No. 4,282,366, issued Aug. 4, 1981; U.S. Pat. No. 4,394,378, issued 
July 19, 1983; and U.S. Pat. No. 3,661,963, issued May 9, 1972, among 
others. 
The aqueous systems which benefit from this invention are any of those 
water systems which cause the build-up of mineral deposits from water. 
Such systems are, for example, humidifiers; cooling systems such as 
cooling towers, air conditioners, and the like; antifreezes, coolants and 
concentrates for use in engine cooling systems; controlling scale in 
geothermal power plants and conventional heat exchange systems, boiler 
water systems and the like. Also contemplated within the scope of this 
invention is the use of the silanes in industrial and household cleaning 
compositions. Further uses contemplated herein are in hydraulic fluids. 
When a silane of this invention is added to an aqueous system, the benefits 
to be derived are continuous operation of the aqueous system for long 
periods of time without re-treating the water; corrosion-free operation of 
the aqueous system and when necessary, easy clean-up and refurbishment of 
the components of the aqueous system.

EXAMPLE 1 
In an attempt to evaluate the ability of the organosilanes of this 
inventive method to diminish the deposition of minerals from water, it was 
necessary to evaluate the organosilanes in a system where the volume of 
water in the system is periodically lost and then replaced such that the 
quantity of minerals in the water system is increased over a period of 
time. Thus, chosen for such an evaluation was a home humidifier which 
required periodic additions of water. 
Two West Bend brand Vapor-All.RTM., one-speed humidifiers (Model No. 3021; 
Vapor-All.RTM. is a registered trademark of the West Bend Co., West Bend, 
Wisc., U.S.A.), having an eight gallon per 24 hour displacement potential, 
were used in this experiment. These humidifiers are the rotating drum type 
which have spun-polyester water pick-up belts. 
The polyester belts were thoroughly rinsed with tap water before the 
testing began. Each humidifier reservoir was filled with 24 liters of tap 
water. The humidifiers were labeled "A" and "B". The "A" humidifier was 
treated by adding 28.3 grams of 42 weight % in water 
EQU (CH.sub.3 O).sub.3 Si(CH.sub.2).sub.3 N(CH.sub.3).sub.2 C.sub.18 H.sub.37 
Cl.sup.-, 
directly to the water in the reservoir, and the mixture was stirred to 
disperse the silane. This level of addition gave a 1.0-.times.10.sup.-3 
molar solution of the silane in the reservoir water. The "B" humidifier 
received nothing but 24 liters of tap water. 
Samples of water from each reservoir were taken periodically and analyzed 
by atomic absorption to monitor the magnesium and calcium ion 
concentrations (precursors to the dominant silicates that are formed). 
The "B" humidifier displayed gross mineral precipitation in the water 
reservoir after about two hundred hours run time, whereas the "A" 
humififier water reservoir remained clear of precipitation and 
discoloration. 
The mineral scaling profiles of both humidifiers were subjectively evaluted 
by visually rating the drum and belt condition at the beginning of each 
run cycle while they were in the dry state. The levels of mineral scaling 
were assigned values of from 0 to 5, with 0 representing no scaling and 5 
representing gross meneral deposits across the non-submerged surfaces of 
the belt and drum. 
The results are summarized in Table I. 
The results show that the cationic silane of the treated reservoir showed a 
much enhanced resistance to mineral scaling relative to a control without 
any silane added. 
TABLE I 
__________________________________________________________________________ 
Results from Example 1 
Total Run Points at Which 
Scaling 
Ion Concentration/ppm 
Time in "On" 
Fresh Tap H.sub.2 O was 
Level 
A B 
Ref. 
Position/hours 
added/quantity 
A B Mg.sup.++ 
Ca.sup.++ 
Mg.sup.++ 
Ca.sup.++ 
__________________________________________________________________________ 
A 0 24 liters 0 0 7.2 .+-. 0.5 
16.0 .+-. 2 
7.2 .+-. 0.5 
16.0 .+-. 2 
B 1.5 -- 0 0 -- -- -- -- 
C 8.5 -- 0 0 -- -- -- -- 
D 17.1 -- 0 0 -- -- -- -- 
E 25.6 20 liters 0 0 -- -- -- -- 
F 34.2 -- 0 0 -- -- -- -- 
G 42.7 20 liters 0 0 -- -- -- -- 
H 51.4 -- 0 0 -- -- -- -- 
I 59.8 20 liters 0 0 22.8 54.0 23.4 54.0 
J 115.9 20 liters 0 0 -- -- -- -- 
K -- 20 liters -- 
-- -- -- -- -- 
L 148.7 20 liters 0 0 -- -- -- -- 
M 156.8 -- 0 1 -- -- -- -- 
N 164.9 20 liters 0 1 -- -- -- -- 
O 173.3 20 liters 0 1 -- -- -- -- 
P 181.8 20 liters 0 2 51.6 94 53.2 59.0 
Q 189.6 -- 0 2 -- -- -- -- 
R 198.0 15 liters 0 3* 
-- -- -- -- 
S -- 15 liters -- 
-- -- -- -- -- 
T 229.5 -- 0 4* 
-- -- -- -- 
U 255.0 20 liters 0 4* 
-- -- -- -- 
V 263.4 10 liters 1 4* 
61.6 112 68.8 99.0 
W 271.9 -- 1 4* 
X 279.9 20 liters 1 5* 
Y 279.9 20 liters 1 5* 
61.6 37 53.6 29 
__________________________________________________________________________ 
*In each of these cases, the mineral precipitate was very gross.