Alcohol composition containing novel hydroxy-substituted aliphatic silicone sulfonate-silicate copolymers

Hydroxy-substituted aliphatic silicone sulfonate-silicate copolymers are useful metal corrosion inhibitors for metals that come in contact with aqueous liquids. Antifreeze concentrates and a process for inhibiting the corrosion of metals below sodium in the electromotive series which come in contact with aqueous liquids are disclosed.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to novel aliphatic silicone sulfonate-silicate 
copolymers and to corrosion inhibited aqueous solutions containing said 
polymers and particularly to antifreeze concentrates useful upon dilution 
with water as coolants in heat-exchange systems such as the cooling system 
of an internal combustion engine. 
2. Prior Art 
Kanner et al disclose in U.S. Pat. No. 3,507,897, hydroxy-substituted 
aliphatic silicone sulfonate copolymers with alkyl or aryl siloxanes for 
use as surfactants. Pines in U.S. Pat. Nos. 3,341,469 and 3,337,496 
disclose organosiloxane-silicate copolymers useful for inhibiting the 
corrosion of metals in contact with aqueous liquids. Additional 
organosiloxane-silicate copolymers useful as corrosion inhibitors are 
disclosed in U.S. Pat. Nos. 3,312,622; 3,198,820; 3,203,969; and 
3,248,329. 
SUMMARY OF THE INVENTION 
Copolymers of an aliphatic hydroxy-substituted silicone sulfonate with a 
water-soluble silicate have been found useful as corrosion inhibitors to 
protect against the corrosion of metals below sodium in the electromotive 
series that come in contact with aqueous liquids. The novel copolymers of 
the invention are useful in the preparation of antifreeze concentrates 
which, upon dilution with water, are useful as coolants, for instance, in 
the cooling system of an internal combustion engine. A process for 
inhibiting the corrosion of metals below sodium in the electromotive 
series is also disclosed. 
DETAILED DESCRIPTION OF THE INVENTION 
The copolymers of the invention are prepared by reacting an 
hydroxy-substituted aliphatic silicone sulfonate with a water-soluble 
silicate. By reacting the water-soluble silicate with said silicone 
sulfonate, the gel tendencies of water-soluble silicates in aqueous media 
can be inhibited thus prolonging the effectiveness of water-soluble 
silicates as corrosion inhibitors for metals below sodium in the 
electromotive series that come in contact with aqueous liquids. 
The copolymers of this invention contain from 0.1 to 99.9 parts by weight 
(per 100 parts by weight of the copolymer) of at least one siloxane group 
derived from hydroxy-substituted aliphatic silicone sulfonates represented 
by the formula: 
##STR1## 
wherein M is a monovalent, divalent or trivalent cation preferably a 
monovalent cation selected from the group consisting of alkali metal, 
ammonium, hydrogen, and tetraorganoammonium; x is 1 to 3 and equal to the 
valence of M; R is a hydroxy-substituted aliphatic divalent group having 3 
to about 18 carbon atoms preferably selected from the group consisting of 
hydroxy-substituted alkylene and cycloalkylene, alkylene oxyalkylene, and 
cycloalkylene oxyalkylene groups and said hydroxy substituent is bonded to 
a carbon atom vicinal to the carbon atom to which the --O.sub.3 S--group 
is bonded; R.sup.1 is a monovalent alkyl group preferably selected from 
the group consisting of alkyl and cycloalkyl of 1 to about 8 carbon atoms, 
and a is an integer of 0 to 2 and from 0.1 to 99.9 parts by weight (per 
100 parts by weight of the copolymer) of at least one silicate group 
derived from silicates having the formula: 
##STR2## 
wherein X is a cation that forms a water-soluble silicate preferably 
selected from the group consisting of at least one alkali metal, ammonium, 
and tetraorganoammonium cation; d is the valence of the cation represented 
by X and has a value of at least 1; and e has a value of from 1 to 3, said 
parts by weight being based upon 100 parts by weight of said copolymer. 
Most preferably, X is inorganic and selected from the group consisting of 
sodium, potassium, lithium, and rubidium. 
Preferably, the copolymers of this invention contain about 15 to about 45 
parts by weight (per 100 parts by weight of said copolymer) of repeating 
hydroxy-substituted aliphatic silicone sulfonate members derived from said 
silicone sulfonates as described above and about 55 to about 85 parts by 
weight (per 100 parts by weight of said copolymer) of repeating groups 
derived from the water-soluble silicate described above. Most preferably, 
said copolymers contain about 15 to about 25 parts by weight of said 
silicone and about 75 to about 85 parts by weight of said silicate. 
Such hydroxy-substituted aliphatic silicone sulfonates can be obtained in 
high yields by reaction of epoxy or more specifically, glycidoxy silicone 
compositions with a bisulfite salt in the presence of relatively minor 
amounts of a sulfite salt. The silicone sulfonate compositions useful in 
the preparation of the copolymers of the invention are disclosed, together 
with processes for their preparation, in U.S. Pat. No. 3,507,897, 
incorporated herein by reference. 
Typical monovalent metal cations represented by M in the above-described 
structural formula for the hydroxy-substituted aliphatic silicone 
sulfonate are sodium, potassium, lithium, rubidium, cesium, ammonium or 
tetraalkylammonium. Illustrative divalent metal cations represented by M 
are barium, calcium, strontium, zinc, cadmium, magnesium, iron, cobalt, 
nickel, copper, tin, lead, mercury and the like. Useful trivalent metal 
cations represented by M are aluminum, nickel, tin, and the like. 
Preferably the cation represented by M is an inorganic cation. 
Representative alkyl groups for R.sup.1 in the above-structural formula for 
the hydroxy-substituted aliphatic silicone sulfonate are alkyl or 
cycloaliphatic groups having 1 to about 8 carbon atoms such as methyl, 
ethyl, propyl and cyclohexyl. Illustrative R groups are 
hydroxy-substituted alkylene, alkylene oxyalkylene, hydroxy-substituted 
cycloalkylene, and cycloalkylene oxyalkylene groups, and the like. 
The water-soluble silicates used in producing the copolymers of the 
invention are specifically represented by the alkali metal orthosilicates, 
the alkali metal metasilicates, the alkali metal tetrasilicates, the 
alkali metal disilicates, and the tetra(organo)ammonium silicates. 
Specific examples of silicates under each class of the above silicates are 
potassium metasilicate, sodium orthosilicate, potassium disilicate, 
lithium orthosilicate, lithium metasilicate, lithium disilicate, rubidium 
disilicate, rubidium tetrasilicate, mixed alkali metal silicates, ammonium 
silicate, tetra(ethyl)ammonium silicate, phenyltrimethylammonium silicate, 
benzyltrimethylammonium silicate, guanidine silicate, and 
tetra(hydroxy-ethyl)ammonium silicate. The preferred silicates are sodium 
and potassium silicates, especially sodium metasilicate and potassium 
metasilicate. 
In the preparation of the copolymers of the invention, the starting 
water-soluble silicate utilized can be added to an aqueous mixture, 
preferably an aqueous alcohol mixture, such as one containing ethylene 
glycol or the starting silicate can be formed in situ by adding the 
appropriate hydroxide (for instance, sodium hydroxide or potassium 
hydroxide) and silica to the reaction mixture. The hydroxy-substituted 
aliphatic silicone sulfonates can be added to an aqueous solution together 
with the starting water-soluble silicate. In addition, a silane precursor 
of the hydroxy-substituted aliphatic silicon sulfonate (siloxane) can be 
utilized to form the siloxane in situ. The presence of water converts said 
silane to the desired siloxane by hydrolysis and condensation. The 
siloxane so formed then reacts with the water-soluble silicate to produce 
the copolymer of this invention. The temperature at which the copolymers 
of this invention are formed can vary widely. Temperatures from 20.degree. 
C. to 150.degree. C. can be used. However, temperatures from 20.degree. C. 
to 115.degree. C. are preferred. 
The copolymers of the invention are soluble in aqueous liquids, that is, in 
water or aqueous solutions of water-soluble materials such as 
water-soluble alcohols, for instance, ethylene glycol. Because these 
copolymers inhibit metal corrosion, metals below sodium in the 
electromotive series exhibit remarkably less corrosion when in contact 
with aqueous liquids containing the copolymers of this invention as 
compared with aqueous liquids without the corrosion inhibiting copolymers 
of this invention. Thus, the copolymers of the invention are particularly 
suited for the preparation of corrosion inhibiting aqueous media, i.e., 
coolants for use, for example, in the cooling system of internal 
combustion engines. 
The copolymers of the invention also can be added to aqueous liquids to 
provide corrosion protection in which case the copolymer is uniformly 
dispersed throughout the liquid by any suitable means. Thus, in the case 
of moving liquids that are in contact with the metal to be protected, the 
copolymer can be added to the liquid while the liquid is in use and 
dispersion of the copolymer throughout the liquid can be achieved by the 
movement of the liquid. Addition of the copolymer to a liquid prior to its 
use in contact with a metal to be protected allows the copolymer to be 
dispersed throughout the liquid, for instance, by stirring the liquid. 
The copolymers of this invention are generally useful for the protection of 
metals that come into contact with an aqueous liquid. Suitable liquids are 
pure water, aqueous solutions containing inorganic solutes and solutions 
containing water and water-soluble organic compounds, especially water 
soluble or miscible organic liquids. Illustrative of suitable aqueous 
solutions containing inorganic solutes are aqueous sodium or potassium 
chloride, refrigerating solutions, corrosive well water or river water 
containing chlorides, carbonates and sulfates which may be used as process 
or cooling water in industry, and the like. Illustrative of suitable 
solutions containing water and a water-soluble organic liquid are 
solutions containing water and monohydric or polyhydric alcohols (e.g., 
methanol, ethanol, propanol, ethylene glycol, propylene glycol and 
glycerol), hydroxy and alkoxy end blocked polyalkylene oxides (such as 
hydroxyl end-blocked polyethylene oxide), sulfoxides (such as 
methylsulfoxide), formamides (such as dimethylformamide) or cyclic ethers 
free of olefinic unsaturation (such as tetrahydrofuran, dioxane and the 
like). Suitable solutions containing water and a water-soluble orgaic 
liquid should contain at least 0.1 part by weight, or preferably, at least 
about 5.0 parts by weight of water per 100 parts by weight of the total 
weight of the water and the organic liquid. 
The copolymers of this invention are generally useful in the protection of 
all metals and alloys that are used in industrial processes and apparatus. 
Metals whose corrosion is retarded by the copolymers of this invention 
include the metals below sodium in the electromotive series (e.g., 
magnesiuim, aluminum, copper, iron, manganese, nickel, lead, silver, tin, 
beryllium and zinc) as well as the alloys of such metals (e.g., brass, 
bronze, solder alloys, steel and the like). Such metals are solids at 
25.degree. C. and normally become corroded when in prolonged contact with 
water, particularly when the water is at elevated temperatures and/or 
contains electrolytes (e.g., acidic solutes). The copolymers of this 
invention are particularly useful in the protection of brass, iron, copper 
and aluminum. 
The amount of the copolymers of this invention used in inhibiting corrosion 
of metals in contact with aqueous liquids is dependent upon the 
temperature, type of metal or metals being protected, type of any organic 
liquid in the solution, pH of the aqueous liquid, velocity of the aqueous 
liquid, inorganic solutes (e.g., electrolytes such as chlorides, sulfates 
and bicarbonates) in the aqueous liquid and prior treatment or corrosion 
of the metal. Generally, from 0.01 part to about 5 parts by weight of the 
copolymer per 100 parts by weight of the aqueous liquid to which the 
inhibitor is added are useful. Preferably, about 0.02 part to about 2.0 
parts by weight, and most preferably, about 0.025 part to about 1 part by 
weight of the copolymer per 100 parts by weight of the aqueous liquid are 
used. 
Compared with known inhibitors used in preventing corrosion of metals that 
are in contact with water, the copolymers of this invention provide 
numerous advantages. Thus, the copolymers can be added to a wide variety 
of aqueous solutions and inhibit the corrosion of a wide variety of 
metals. In addition, the copolymers are effective over a wide temperature 
range and these inhibitors do not cause the liquids in which they are 
employed to foam excessively. Furthermore, these copolymers do not promote 
the decomposition of any organic liquids present in the liquid nor do they 
attack other organic materials with which the liquid may come in contact. 
The copolymers of the invention are useful in preventing the corrosion of 
metals that are cleaned by corrosive solutions or that are used in cooling 
coils, boilers, refrigeration and air conditioning equipment, heat 
exchange tubes, storage tanks for liquids, pipes, solvent containers, tank 
cars, ballast tanks containing sea water and the like. The copolymers of 
this invention are particularly useful for inhibiting the corrosion of the 
metals in the cooling system of an internal combustion engine in contact 
with an aqueous alcohol coolant composition. 
Inhibited alcohol compositions containing an alcohol and a copolymer of 
this invention as a corrosion inhibitor are remarkably useful as 
antifreezes and coolants for the cooling system of an internal combustion 
engine. These antifreezes are inhibited alcohol solutions containing 
relatively large amounts of water. The antifreeze concentrates used in 
making the antifreeze or coolant composition are adapted to economical 
shipment and storage. The coolants are adapted to use as heat transfer 
media in the cooling system of internal combustion engines. In practice, 
the antifreeze concentrate can be shipped to the point where it is to be 
added to the cooling system and normally diluted to form a coolant. Water 
imparts desirable properties to both the concentrate and coolant 
compositions (e.g., large amounts of water impart good heat transfer 
properties to the coolant compositions). These coolant compositions 
generally contain from 1 part by weight to about 900 parts by weight of 
water per 100 parts by weight of the antifreeze concentrate. It is 
preferable that the coolant compositions contain about 30 to about 900 
parts by weight of water per 100 parts by weight of said concentrate. 
Generally, the concentrates contain from 0.1 part to about 10 parts by 
weight (or preferably about 2 parts to about 5 parts by weight) of water 
per 100 parts by weight of said concentrate. The relative amount of water 
and alcohol in these compositions can be varied to adjust the freezing 
point of the compositions by the desired amount. The above-described 
inhibited alcohol compositions can be formed in any convenient manner, 
e.g., by adding an alcohol, the organosilicon inhibitor, and water to a 
container and stirring the mixture. 
The pH of the inhibited aqueous alcohol compositions of this invention 
should be greater than seven to minimize corrosion of metals with which 
the compositions come into contact. Generally, the pH of the antifreeze 
concentrate or coolant composition is about 8 to about 12, preferably 
about 8 to about 11, and most preferably about 8.5 to about 10. The pH is 
maintained within the above ranges by the addition of conventional pH 
buffers such as salts of strong bases and weak acids, as are disclosed in 
U.S. Pat. No. 3,121,692, incorporated herein by reference. 
The effectiveness as metal corrosion inhibitors of the copolymers of the 
invention is a function of the retention of the solubility characteristics 
of the copolymer in an aqueous media, i.e., to remain effective, the 
copolymers must not precipitate or form gels during the effective life of 
the inhibited aqueous media. 
If desired, various additives can be added to the above-described inhibited 
alcohol compositions in particular instances for imparting special 
properties. By way of illustration, anti-foam agents, identifying dyes, pH 
indicators, conventional corrosion inhibitors, sealants which prevent 
leakage of the coolant from the cooling system, anti-creep agents which 
prevent seepage of the coolant into the crankcase and the like can be 
added to these compositions. 
Useful antifoam agents are alkoxylated nonionic surfactants which exhibit 
low-foaming characteristics. Examples of alkoxylated nonionic synthetic 
detergents which can be advantageously employed as antifoam agents in the 
antifreeze compositions of the invention include polyoxyalkylene adducts 
of hydrophobic bases, as illustrated by PLURONIC.RTM.L-61. Typical 
hydrophobic bases which can be condensed with alkylene oxides are the 
mono- and polyalkylphenols and the compounds prepared by condensing 
polyoxypropylene with a hydrophobic base initiator having from about 1 to 
6 carbon atoms and at least one reactive hydrogen atom. Additional useful 
defoamers based upon nonionic surfactants are disclosed in U.S. Pat. No. 
3,931,029, incorporated herein by reference. Useful water-pump lubricants 
are known in the prior art. 
Conventional corrosion inhibitors and/or alkaline pH buffers which can be 
used under aqueous alkaline conditions in combination with the copolymer 
corrosion inhibitors of the invention include water-soluble metal salts 
such as the alkali metal carbonates, borax, the alkali metal dichromates, 
the alkali metal phosphates, the alkali metal tungstates, the alkali metal 
salts of benzoic or toluic acid, the alkali metal salts of phenol, 
benzotriazole or tolyltriazole, lower alkanolamines (C.sub.2 -C.sub.6), 
for instance, triethanolamine, alkali metal nitrates, alkali metal 
nitrites, alkali metal molybdates, and alkali metal 
mercaptobenzothiazoles. Such conventional corrosion inhibitors are used 
under alkaline conditions in an amount effective to inhibit corrosion. 
Generally, conventional corrosion inhibitors are used in the amount of 
about 0.03 parts to about 5 parts by weight, preferably about 0.1 to about 
2.0 parts by weight per 100 parts total weight of the antifreeze 
concentrate. 
Many antifreeze compositions can be formulated in accordance with the 
teachings of the present invention. The compositions described below are 
merely representative of the heat transfer or antifreeze compositions 
contemplated by the invention. Where not otherwise specified throughout 
this specification and claims, temperatures are given in degrees 
centigrade and parts, percentages and proportions are by weight. 
TEST METHOD 
In order to demonstrate the effectiveness of said hydroxy-substituted 
silicone sulfonates as gel stabilizers for aqueous solutions of 
water-soluble silicates, the copolymers of the invention were formed by 
mixing at ambient temperature and pressure said hydroxy-substituted 
silicone sulfonates with a water-soluble silicate in a mixture of 
distilled water and antifreeze grade ethylene glycol. Samples were placed 
in sealed glass jars, aged at a temperature of 180.degree. F. and a pH of 
8 over a period of about 2 weeks, and observed for the appearance of 
gelation. The structurally closest siloxanes were utilized as controls in 
separate concentrates. Each of the solutions were run in triplicate and 
contained 3 percent by weight distilled water, 0.4 percent by weight of 
sodium metasilicate (Na.sub.2 SiO.sub.3.5H.sub.2 O), the calculated amount 
of siloxane in weight percent, as noted below, so as to provide an 
equimolar amount in comparison with the control sample, and the balance 
antifreeze grade ethylene glycol which contains about 5 percent diethylene 
glycol. The silicate is in the form, NaOSiO.sub.1.5 in aqueous solution.

EXAMPLE 1 
3-(Sodium sulfo-2-hydroxy-oxypropyl)propyl siloxane in the average form 
##STR3## 
in aqueous solution was utilized in the amount of 0.01 weight percent. 
After two weeks at 180.degree. F., the sample utilizing this level of 
siloxane showed no indication of gelation. 
EXAMPLE 2 
Example 1 was repeated except that 0.02 weight percent of siloxane was 
used. After two weeks at 180.degree. F., there was no indication of 
gelation. 
EXAMPLE 3 
Example 1 was repeated except that 0.04 weight percent of siloxane was 
used. After two weeks at 180.degree. F., no gelation appeared. 
EXAMPLE 4 
(Control forming no part of this invention) 
(2-3-Dihydroxyoxypropyl)-propyl siloxane was utilized in the amount of 
0.007 weight percent. No gelation occured after two weeks at 180.degree. 
F. 
EXAMPLE 5 
(Control forming no part of this invention) 
Example 4 was repeated except that 0.014 weight percent was utilized. Gel 
formation occurred after two days at 180.degree. F. 
EXAMPLE 6 
(Control forming no part of this invention) 
Example 4 was repeated except that 0.029 weight percent was utilized. After 
11 days at 180.degree. F., gel formation occurred. 
EXAMPLE 7 
The procedure of Example 3 is repeated substituting 
(3-sodiumsulfo-4-hydroxy cyclohexyl)ethyl siloxane for the siloxane of 
Example 3. In aqueous media, this has the average formula 
##STR4## 
No gel is formed. 
While this invention has been described with reference to certain specific 
embodiments, it will be recognized by those skilled in this art that many 
variations are possible without departing from the scope and spirit of the 
invention and it will be understood that it is intended to cover all 
changes and modifications to the invention disclosed herein for the 
purposes of illustration which do not constitute departures from the 
spirit and scope of the invention.