United States Patent [191 [11] Patent Number: 4,578,205

Yeakey et al. [45] Date of Patent: Mar. 25, 1986

[54] USE OF METHYLENE AZELAIC ACID AS A 3,678,102 7/1972 Isard et a1. ........................ .. 562/595
CORROSION INHIBITOR FOREIGN PATENT DOCUMENTS
[75] Inventors‘ (ififi’z?zbpbavid R 2036062 6/1980 United Kingdom .
McCoy, all Of Austin, TBX- Primary Examiner—Paul Lieberman
- ' ' Assistant Examiner—Hoa Van Le
73 : ., Pl , N.Y. _
l ] Asslgnee Texaco’ Inc Whlte ams Attorney, Agent, or F1rm—Jack H. Park; Kenneth R.
[21] Appl. No.: 697,193 Priem; Richard A. Morgan
[22] Filed: Feb. 1, 1985 [57] ABSTRACI‘
[51] Int. Cl.‘1 .............................................. .. C09K 5/00 The use of methylene azelaic acid having the formula
[521 115- Cl -- 252/76; 252/73; CH2:C—[(CH2)3—COOH]2 or an alkali metal salt
252/79; 252/82; 252/174'185 252/180; 2556255965; thereof in glycol and water based automotive antifreeze
_ formulations is described. Unlike natural dicarboxylic
[58] Field of searchz acids such as sebacic acid, methylene azelaic acid does
' ’ ’ ’ ’ not form a precipitate and drop out of solution, render
[56] References Cited ing the antifreeze unprotected against corrosion. The
U.S. PATENT DOCUMENTS methylene azelaic acid component should be present in
an amount of from 1.5 to 4.5 wt. % based on the glycol
2,641,607 6/1953 Albisetti et al. . ............... .. 260/4653
2,722,516 11/1955 Merker ....... .. . . . . . . .. 252/396
component.
2,726,215 12/1955 Jones . .... .. .. . . . .. 252/76

2,767,144 10/1956 Gottshall ........................... .. 252/396 12 Claims, N0 Drawings

 4,578,205
1 2
USE OF METHYLENE AZELAIC ACID AS A SUMMARY OF THE INVENTION
CORROSION INHIBITOR The invention concerns the use of a methylene aze
laic acid component as a corrosion inhibitor in a glycol
BACKGROUND OF THE INVENTION component and water antifreeze formulation. The
1. Field of the Invention methylene azelaic acid component is methylene azelaic
The invention relates to corrosion-inhibited aqueous acid alone or an alkali metal salt of methylene azelaic
solutions, and particularly relates to corrosion-inhibited acid.
antifreeze compositions containing dicarboxylic acids DETAILED DESCRIPTION OF THE
useful as coolants in a heat exchange system such as the PREFERRED EMBODIMENTS
cooling system of an internal combustion engine.
2. Other Inhibitors Known in the Art
It has been surprisingly discovered that methylene
azelaic acid is a dicarboxylic acid which will not form a
It is well known to use dicarboxylic acids as corro
troublesome precipitate when mixed with hard water.
sion inhibitors in aqueous systems. For example, Jones 15 The corrosion-inhibited antifreeze solution remains
in US. Pat. No. 2,726,215 teaches that dicarboxylic clear.
acids; namely, sebacic acid and azelaic acid, and their Methylene azelaic acid has the formula
alkali metal and alkali earth metal salts are useful corro
CH2=C—[(CH2)3—COOH]2 and is made by the fol
sion inhibitors in aqueous solutions. The use of a mix lowing “ene” reaction between isobutylene and two
ture of sodium sebacate (sodium salt of sebacic acid) and 20 moles of acrylonitrile followed by hydrolysis.
benzotriazole was disclosed as a useful corrosion inhibi
tor in engine coolants by G. Butter, et al. in “Inhibitor
Formulations for Engine Coolants,” British Corrosion
Journal, Vol. 12, No. 3, 1977, pp. 171-174. Similarly,
British Military Speci?cation TS 10177 calls for the use 25
of disodium sebacate and benzotriazole in antifreeze
formulation AL-39. The speci?cation uses 4.0—4.5 wt.%
disodium sebacate and 0.25-0.3 wt.% benzotriazole.
US. Pat. No. 3,931,029 to Dutton, et al. teaches the
use of certain unsaturated cycloalkylene dicarboxylic
acids as antifreeze additives to inhibit corrosion of con
tacted solder alloys. Corrosion inhibitors containing an
imidazoline derivative, a carboxylic acid or its metal salt
and/or a phosphate are used for steel in brackish or
acidic water according to Chemical Abstracts, Vol. 99, 35
paragraph l267l3x, 1983, which describes Japanese
Kokai 58-84, 981. US Pat. No. 4,382,008 reveals a In reality, the methylene group probably isomerizes
corrosion-inhibited antifreeze containing a triazole, an over the length of the middle alkylene, such that the
alkali metal borate, an alkali metal benzoate, an alkali methylene group is not always in the middle and methy
metal silicate and an alkali metal salt of a C7 to C13 lene azelaic acid turns out to be a mixture of isomers.
dibasic organic acid. The use of sodium sebacate as a Other similar compounds such as CH2=C—[(CH3
corrosion inhibitor in phosphate-based antifreezes is )4—COOH]2 may work but would be dif?cult to syn
further seen in the Derwent Abstract of Week E14 for thesize and would have to use another route. If methyl
French Certi?cate of Utility No. 2,489,355 to Perrot. 45 methacrylate were used instead of acrylonitrile, it may
be possible to make compounds such as
The Derwent Abstract of Week K18 for European
Pat. No. 77,767-B teaches the use of water-soluble salts
of dicarboxylic acids having at least three carbon atoms CH3
as antifreeze corrosion inhibitors. These acids are ma CH2CHCH2—COOH
lonic, succinic, glutaric and adipic acids along with CH2=C
smaller proportions of C3 and/or C10 dicarboxylic acids.
While the natural C8 to C12 dibasic acids; i.e. sebacic CH2CHCI-Ig—COOI-I
acid, azelaic acid, are useful as corrosion inhibitors in CH3
antifreeze, it has been discovered that when automobile
antifreeze formulations containing these dicarboxylic 55 which may be useful corrosion inhibitors.
acids, such as sebacic acid, are mixed with hard water, The methylene azelaic acid component useful as a
the sebacic acid completely falls out of solution as cal nonprecipitating corrosion inhibitor may be methylene
cium sebacate forming a very heavy precipitate. This azelaic acid alone or an alkali metal salt of methylene
precipitate could plug radiators, thermostats and water azelaic acid such as sodium methyleneazelate.
pumps of automotive cooling systems and thus lead to Typically, this compound is used as a corrosion inhib
rapid overheating of the engine. Since the corrosion itor in antifreeze formulations. The antifreeze formula
inhibitor has been precipitated out of the system, corro tions most commonly used include mixtures of water
sion would begin on the surfaces in contact with the and glycols and/or glycol ethers. The glycol compo
unprotected formulation. nent which can be employed as a major component in
Thus, an object of the invention is to provide a dicar 65 the present composition may be one or more glycols
boxylic acid which is useful as a corrosion inhibitor and such as ethylene glycol, diethylene glycol, propylene
which does not precipitate out in the presence of hard glycol, and dipropylene glycol, and/or glycol mono
water. ethers such as the methyl, ethyl, propyl and butyl ether
 4,578,205
3 4
of ethylene glycol, diethylene glycol, propylene glycol rejecting surfaces. Results of this test are given in Table
and dipropylene glycol. Also useful are glycol diethers II.
such as methyl and ethyl diethers of ethylene glycol, TABLE II
diethylene glycol, propylene glycol and dipropylene
ASTM D4340 Aluminum Hot Surface Corrosion Test
glycol. Ethylene glycol is the particularly preferred
glycol component. Weight Loss, mg/cmz/wk
The methylene azelaic acid component should be Example 2 0.65
ASTM spec., max. 1.0
present on the order of 0.5 to 5.0 wt.% based on the
glycol component, preferably 1.5 to 4.5 wt.%.
Other corrosion inhibitors and additives may be em
EXAMPLES 3-7
ployed to a lesser extent in the antifreeze formulation.
For example, alkali metal borates, which include so Examples 3 through 7 will demonstrate that the diso
dium tetraborate, potassium tetraborate, sodium metab dium salt of methylene azelaic acid will not precipitate
orate and potassium metaborate may be used. Other when contacted with hard water, unlike the disodium
permissible, but not required, components include alkali salt of other dicarboxylic acids such as sebacic acid and
metal silicates, such as sodium metasilicate, potassium a C11-C12 dicarboxylic acid mix (undecanedioic and
metasilicate and lithium metasilicate. Also useful are the dodecanedioic).
silicates represented by the formula [M(1/q)O]bSi Miscibility with hard water was measured according
O(4__1,); M is a cation that forms a water-soluble silicate, to test DIN 51367.6 from the Dainler-Benz speci?ca
a is the valence of the cation represented by M and b has 20 tions for antifreeze/coolant. The hard water and anti
a value from 1 to 3, inclusive. See U.S. Pat. Nos. freeze are mixed in a 2:1 ratio, 60 ml of hard water with
3,337,496 and 3,312,622. Other allowable components 30 ml of antifreeze. The hard water here has 540 ppm
include alkali metal nitrates, such as sodium nitrate and CaCO3. The mixture is allowed to stand 24 hours at
potassium nitrate, azoles such as alkali metal mercapto room temperature (about 25° C.). The appearance at the
thiazoles and alkali metal tolyltriazoles, alkali metal end of 24 hours is reported and any deposits are ?ltered,
nitrites such as potassium nitrite and sodium nitrite, dried and weighed.
alkali metal phosphates such as sodium phosphate and TABLE III
potassium phosphate, alkali metal benzoates and various
foaming agents and dyes, if desired. The components MM
30 Ex- Deposit
should be present in amounts of equal to or less than 1 ample Solution Appearance wt., mg
wt.% based on the glycol component, preferably from 3 4.2 wt. % Na sebacate and Heavy, 1456
0.01 to 1.0 wt.%, if they are used. tolyltriazole white precipitate
The amounts of these various other corrosion inhibi 4 4.2 wt. % Na (Cu/C11 mix) Heavy, 1189
tors which render them effective are well known in the 35 and tolyltriazole off-white pre
cipitate
art. Of course, the precise amount will vary for each 5 4.2 wt. % Na methylene Clear 16
inhibitor. It is not possible to set forth exactly the azelate and tolyltriazole
amount of the components of the corrosion-preventing 6 Commercial formulation Clear 13
mixture that might be desired due to the complicating
in?uence of the various parts. Simple, accelerated aging 40 To pass this test, the solution should be clear and with
tests can be used to determine the amount of silicate deposit weights in the same range as the currently ap
which when added will give the desired corrosion resis proved product (designated “commercial formula
tance. tion”). Only the methylene azelaic acid formulation
The invention will be further illustrated by the fol (Example 5) would pass this hard water test. The other
lowing examples which are not intended to limit the 45 diacids are not even close to being acceptable. The total
invention, but rather to illuminate it. inhibitor content appears to have precipitated in Exam
EXAMPLE 1
ples 3 and 4.
For the purposes of this invention, hard water is
A blend of ethylene glycol, 4.2 wt.% disodium salt of de?ned as water with 200 ppm CaCO3 or more, prefera
methylene azelaic acid and 0.2 wt.% tolyltriazole were 50 bly 500 ppm CaCO3 or more. At levels of 200 ppm,
prepared and tested in the ASTM D-l384 Glassware dicarboxylic acids with twelve or more carbon atoms
Corrosion Test. Results of this test are given in Table I. give precipitates whereas acids with fewer carbon
atoms, such as sebacic acid, are not adversely affected.
TABLE I However, at the 500 ppm level and above even these
55 lighter acids give precipitate and a corrosion inhibitor
ASTM D-l384 Glassware Corrosion Test
such as methylene azelaic acid would be necessary.
Wt. Loss, m_g/coupon
Example Cu 70/30 Solder Brass Steel Iron Aluminum EXAMPLE 7
1 4 2 4 0 l 3 A blend of ethylene glycol, 4.3 wt.% sodium me
ASTM 10 30 10 1O 10 3O thyleneazelate and tolyltriazole was prepared and tested
spec, max.
as in Example 1 with the passing results given below.
TABLE IV
EXAMPLE 2 ASTM D-l384 Glassware Corrosion Test
The antifreeze composition prepared in Example 1 65 Cu Solder Brass Steel Iron Al
was tested in the ASTM D-4340 Aluminum Hot Sur Ex. 7 formulation 2 2 2 1 0 2
face Corrosion Test. This test gives a measure of the ASTM spec., max. 10 30 l0 l0 10 30
degree of protection an antifreeze has at aluminum heat
 4,578,205 -
5 6 -
adding to an antifreeze comprising a glycol compo
EXAMPLE 8 nent and water an effective amount of a methylene
The antifreeze composition in Example 7 was tested azelaic acid component selected from the group
in the Ford Aluminum Pitting Potential Test with the consisting of methylene azelaic acid alone and an
passing results given below. 5 alkali metal salt of methylene azelaic acid.
5. The method of claim 4 in which the glycol compo~
TABLE V nent is selected from the group consisting of an alkylene
Ford Aluminum Pitting Potential Test glycol, an alkylene glycol ether and mixtures thereof.
Potential, mV vs. SCE 6. The method of claim 4 in which the glycol compo
Example 8 formulation +120 nent is ethylene glycol.
Ford spec, min. -—400 7. The method of claim 4 in which the methylene
azelaic acid component is present in a proportion rang
ing from about 1.5 to 4.5 wt.% based on the glycol
The methods and compositions of this invention may
component.
be further modi?ed by one skilled in the art without 8. The method of claim 4 in which at least one other
departing from the spirit and scope of the invention, corrosion inhibitor is employed, at levels of equal to or
which are de?ned only in the appended claims. For less than 1 wt.% each based on the glycol component,
example, a precise blend of corrosion inhibitors may which is selected from the group consisting of alkali
form a particularly advantageous package. metal borates, alkali metal silicates, alkali metal benzo
We claim: ates, alkali metal nitrates, alkali metal nitrites, alkali
1. A corrosion-protected antifreeze composition metal molybdates and triazoles.
comprising 9. A method for inhibiting corrosion of metal contact
a. a glycol component selected from the group con ing an aqueous antifreeze containing a glycol compo
sisting of an alkylene glycol, an alkylene glycol nent and hard water comprising
ether and mixtures thereof, and 25 adding to an antifreeze comprising hard water and a
b. an effective, corrosion-preventing amount of a glycol component selected from the group consist
methylene azelaic acid component selected from ing of an alkylene glycol, an alkylene glycol ether
the group consisting of methylene azelaic acid and mixtures thereof, an effective amount of a
alone having the formula CH2:C—[CH2 methylene azelaic acid component selected from
)3—COOH]2 and alkali metal salts thereof said the 30 the group consisting of methylene azelaic acid
methylene azelaic acid component present in a alone and an alkali metal salt of methylene azelaic
proportion ranging from about 1.5 to 4.5% based acid.
10. The method of claim 9 in which the glycol com
on the glycol component.
2. The antifreeze composition of claim 1 in which the 35
ponent is ethylene glycol.
11. The method of claim 9 in which the methylene
glycol component is ethylene glycol. azelaic acid component is present in a proportion rang
3. The antifreeze composition of claim 1 in which at ing from about 1.5 to 4.5 wt.% based on the glycol
least one other corrosion inhibitor is employed, at levels component.
of equal to or less than 1 wt.% each based on the glycol 12. The method of claim 9 in which at least one other
component which is selected from the group consisting 40 corrosion inhibitor is employed, at levels of equal to or
of alkali metal borates, alkali metal silicates, alkali metal less than 1 wt.% each based on the glycol component,
benzoates, alkali metal nitrates, alkali metal nitrites, which is selected from the group consisting of alkali
alkali metal molybdates and triazoles. metal borates, alkali metal silicates, alkali metal benzo
4. A method for inhibiting corrosion of metal contact ates, alkali metal nitrates, alkali metal nitrites, alkali
ing an antifreeze containing a glycol component and 45 metal molybdates and triazoles.
* i * i it
water comprising

50

55

60

65
 UNITED STATES PATENT AND TRADEMARK OFFICE
CERTIFICATE OF CORRECTION
PATENT N0. :4, 578' 205
DATED IMarch 25, 1986
INVENTOR(S) : Ernest Leon Yeakey et al
It is certified that error appears in the above-identified patent and that said Letters Patent is hereby
corrected as shown below:

Column 5, lines 29-30, the formula should read

Signed and Scaled this

Twenty-fourth D l y Of June I 986
[SEAL]
Arrest:

DONALD J. QUIGG

. Arresting Officer Commissioner ofhmm and Tudunaks