Antifreeze concentrates comprising glycerine with corrosion protection
Description
[0001] The present invention relates to antifreeze/anticorrosion concentrates, a process for preparing
such concentrates from superconcentrates, to aqueous coolant compositions from these concentrates,
and to the use thereof.
[0002] Coolant compositions for cooling circuits of internal combustion engines, such as those of
automobiles, generally include alkylene glycols, primarily ethylene glycol and/or propylene glycol, as the
antifreeze component.
[0003] In addition to further components, in particular corrosion inhibitors are included.
[0004] In particular modern internal combustion engines reach temperature loads that place high
demands on the materials that are used. Any kind and any degree of corrosion poses a potential risk
factor that can result in a shortened operating time of the engine and decreased reliability. Additionally, a
plurality of different materials are increasingly used in modern engines, such as cast iron, copper, brass,
soft solder, steel, and magnesium and aluminum alloys. This plurality of metallic materials creates
additional potential corrosion problems, in particular in areas where different metals are in contact with
each other. A wide variety of corrosion types can occur comparatively easily in particular in these areas,
such as pitting, crevice corrosion, erosion or cavitation.
[0005] The coolant compositions likewise must be compatible with non-metallic constituents of the cooling
circuit, such as elastomers and plastic materials from hose connections or gaskets, and must not alter
these.
[0006] The coolant composition is also of crucial importance for the heat transfer in modern internal
combustion engines.
[0007] In addition to coolant containers that already contain the afore-mentioned ready-to-use coolant
compositions, antifreeze/anticorrosion concentrates are of ever greater importance. Only water must be
added to these concentrates so as to obtain the ready-to-use coolant components.
[0008] Antifreeze/anticorrosion concentrates thus likewise comprise components that offer protection from
freezing - which is to say that are used for depressing the freezing point of the mixture - and corrosion
inhibitors that offer corrosion protection. The content of the anticorrosion component in the concentrate is
usually up to 10% by weight based on the total amount of the concentrate. The content of the concentrate
in the ready-to-fill radiator protective agent is usually 10 to 60% by weight. Concentrates may already
comprise small amounts of water.
[0009] In addition superconcentrates are available, in particular for transport reasons, which comprise a
reduce amount of antifreeze component, which is to say generally ethylene glycol, so as to provide as
compact a container as possible. For this purpose, the amount of antifreeze component that is generally
withdrawn from a concentrate is such that the remaining constituents are just barely still present in
dissolved form.
[0010] Antifreeze/anticorrosion concentrates can thus be obtained from superconcentrates by admixing a
certain amount of the antifreeze component, and optionally some water. The content of the
superconcentrate in the concentrate is usually 3 to 60% by weight.
[0011] As mentioned above, it is generally alkylene glycols, primarily ethylene glycol and/or propylene
glycol, that form the main constituents of the antifreeze component.
[0012] The corrosion inhibitors that serve as the anticorrosion component are known from the prior art.
Antifreeze compounds that comprise carboxylic acids, molybdates or triazoles are known from DE-A 195
47 449, EP-B 552 988 or US-A 4,561,990.
[0013] EP-B 229 440 describes an anticorrosion component composed of an aliphatic monobasic acid, a
hydrocarbyl dibasic acid and a hydrocarbyl triazole.
[0014] Special acids as the anticorrosion component are described in EP-B 479 470. Quaternized
imidazoles are disclosed in DE-A 196 05 509.
[0015] EP-A 816467 also discloses higher glycols and glycol ethers as the antifreeze component, in
addition to the customarily used ethylene glycol and propylene glycol.
[0016] WO-A 92/01029 discloses an aqueous coolant composition that comprises glycerol, among other
things.
[0017] EP-A 1416563 discloses a coolant composition for fuel cells.
[0018] DE-A 10163337 discloses radiator protective agent concentrates and coolant compositions having
improved corrosion protection.
[0019] US-A 2003 198847 discloses heat transfer compositions having high electrical resistance for fuel
cells.
[0020] US-A 2388 155 discloses anticorrosion agents for metals.
[0021] US-A 4 000 079 discloses anticorrosion agents and corrosion-inhibiting antifreeze agents.
[0022] EP-A 1010740 discloses concentrated and diluted coolants.
[0023] Glycerol is also a generally known option as a constituent of the antifreeze component.
[0024] DE-A 3 413 416, US-A 2004/0104375 and WO-A 02/090462, for example, mention glycerol as a
possible freezing point depression component, in addition to the customary glycols such as ethylene
glycol.
[0025] WO-A 02/072728 points out the reduced toxicity of ethylene glycol-based antifreeze concentrates
as a result of the addition of small amounts of glycerol.
[0026] The corrosion protection achieved with the previously known mixtures and concentrates and also
the achievable freezing points are generally good. Nonetheless, due to ever increasing performance
capabilities of new internal combustion engines, there is a constant need for improved
antifreeze/anticorrosion concentrates.
[0027] It is the object of the present invention to provide such antifreeze/anticorrosion concentrates which
do not have the disadvantages of the prior art, or at least have them in reduced form. These mixtures
should have a balanced ratio of the corrosion protection, heat transfer and frost resistance properties.
[0028] An antifreeze/anticorrosion concentrate comprising:
- glycerol, wherein the amount of glycerol is from 15 to 35% by weight based on the total amount of the
concentrate;
- alcohols selected from monohydric alcohols, dihydric alcohols, trihydric alcohols other than glycerol,
polyhydroxy alcohols, the ethers thereof or mixtures thereof as the antifreeze component, wherein the
sum of the amounts of alcohol and glycerol is at least 75% by weight based on the total amount of the
concentrate; and
- an anticorrosion component, wherein the amount of anticorrosion component is at least 1% by weight
based on the total amount of the concentrate.
[0029] It has been found that the use of a certain range of amounts of glycerol in the concentrate can
achieve improved properties of the antifreeze/anticorrosion concentrate.
[0030] The amount of glycerol is preferably from 20 to 35% by weight based on the total amount of the
concentrate.
[0031] In addition, alcohols are selected from monohydric alcohols, dihydric alcohols, trihydric alcohols
other than glycerol, polyhydroxy alcohols, the ethers thereof or mixtures thereof as the antifreeze
component.
[0032] Additional alcohols can be ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol,
triethylene glycol, tetraethylene glycol, pentaethylene glycol, hexaethylene glycol, dipropylene glycol,
tripropylene glycol, tetrapropylene glycol, pentapropylene glycol, hexapropylene glycol, monoethers of
glycols such as the methyl, ethyl, propyl and butyl ethers of ethylene glycol, propylene glycol, diethylene
glycol and dipropylene glycol. Ethylene glycol and propylene glycol are preferred. Ethylene glycol is
particularly preferred.
[0033] In the context of the present invention, the term “propylene glycol” is understood to mean 1,2propanediol.
[0034] The amount of antifreeze component (glycerol and additional alcohol or additional alcohols) is at
least 75% by weight based on the total amount of the concentrate. The amount is preferably at least 85%
by weight, and particularly preferably at least 90% by weight.
[0035] The amount of anticorrosion component is at least 1% by weight based on the total amount of the
concentrate. The amount is preferably at least 2% by weight, and particularly preferably from 3 to 8 % by
weight.
[0036] In a preferred embodiment, an antifreeze/anticorrosion concentrate according to the present
invention additionally comprises at least one of the following components in an amount specified in each
case, based on the total amount of the concentrate:
(a) up to 5% by weight of one or more aliphatic, cycloaliphatic or aromatic monocarboxylic acids having in
each case from 3 to 16 carbon atoms in the form of their alkali metal, ammonium or substituted
ammonium salts;
(b) up to 5% by weight of one or more aliphatic or aromatic di- or tricarboxylic acids having in each case
from 3 to 21 carbon atoms in the form of their alkali metal, ammonium or substituted ammonium salts;
(c) up to 1% by weight of one or more alkali metal borates, alkali metal phosphates, alkali metal silicates,
alkali metal nitrites, alkali metal or alkaline earth metal nitrates, alkali metal molybdates or alkali metal or
alkaline earth metal fluorides;
(d) up to 5% by weight of one or more aliphatic, cycloaliphatic or aromatic amines which have from 2 to
15 carbon atoms and may additionally comprise ether oxygen atoms or hydroxyl groups;
(e) up to 5% by weight of one or more mono- or bicyclic, unsaturated or partly unsaturated heterocycles
which have from 4 to 10 carbon atoms and may be benzofused and/or bear additional functional groups;
(f) up to 5% by weight of one or more tetra(C1-C8-alkoxy)silanes (tetra-C1-C8-alkyl orthosilicates);
(g) up to 10% by weight of one or more carboxamides or sulfonamides;
(h) up to 1% by weight of one or more hard water stabilizers based on polyacrylic acid, polymaleic acid,
acrylic acid-maleic acid copolymers, polyvinylpyrrolidone, polyvinylimidazole, vinylpyrrolidonevinylimidazole copolymers and/or copolymers of unsaturated carboxylic acids and olefins.
[0037] The compounds of groups a) to g) are generally corrosion inhibitors.
[0038] Possible linear or branched-chain, aliphatic or cycloaliphatic monocarboxylic acids (a) are, for
example, propionic acid, pentanoic acid, hexanoic acid, cyclohexyl acetic acid, octanoic acid, 2ethylhexanoic acid, nonanoic acid, isononanoic acid, decanoic acid, undecanoic acid or dodecanoic acid.
A suitable aromatic monocarboxylic acid (a) is in particular benzoic acid; additionally, for example, C1- to
C8-alkylbenzoic acids such as o-, m-, p-methylbenzoic acid or p-tert-butylbenzoic acid, and hydroxyl
group-containing aromatic monocarboxylic acids such as o-, m- or p-hydroxybenzoic acid, o-, m- or p(hydroxymethyl)benzoic acid or halobenzoic acids such as o-, m- or p-fluorobenzoic acid are also
possible.
[0039] Typical examples of di- or tricarboxylic acids (b) are malonic acid, succinic acid, glutaric acid,
adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid,
dicyclopentadienedicarboxylic acid, phthalic acid, terephthalic acid and triazinetriiminocarboxylic acids
such as 6,6′,6″-(1,3,5-triazine-2,4,6-triyltriimino)trihexanoic acid.
[0040] All of the mentioned carboxylic acids of groups (a) and (b) are present in the form of alkali metal
salts, in particular in the form of sodium or potassium salts, or in the form of ammonium salts or
substituted ammonium salts (amine salts), for example with ammonia, trialkylamines or trialkanolamines.
[0041] Typical examples of corrosion inhibitors mentioned under (c) are sodium tetraborate (borax),
disodium hydrogen phosphate, trisodium phosphate, sodium metasilicate, sodium nitrite, sodium nitrate,
magnesium nitrate, sodium fluoride, potassium fluoride, magnesium fluoride and sodium molybdate.
[0042] When alkali metal silicates are also used, these are expediently stabilized by customary
organosilicophosphonates or organosilicosulfonates in customary amounts.
[0043] Possible aliphatic, cycloaliphatic or aromatic amines (d) having from 2 to 15, preferably from 4 to 8
carbon atoms, which may additionally comprise ether oxygen atoms, in particular from 1 to 3 ether
oxygen atoms, or hydroxyl groups, in particular from 1 to 3 hydroxyl groups, include, for example,
ethylamine, propylamine, isopropylamine, n-butylamine, isobutylamine, sec-butylamine, tert-butylamine,
n-pentylamine, n-hexylamine, n-heptylamine, n-octylamine, isononylamine, di-n-propylamine,
diisopropylamine, di-n-butylamine, mono-, di- and triethanolamine, piperidine, morpholine, aniline or
benzylamine. Aliphatic and cycloaliphatic amines (d) are generally saturated.
[0044] The heterocycles (e) are, for example, monocyclic five- or six-membered systems having 1, 2 or 3
nitrogen atoms or having one nitrogen atom and one sulfur atom, which may be benzofused. It is also
possible to use bicyclic systems composed of five- and/or six-membered rings having typically 2, 3 or 4
nitrogen atoms.
[0045] The heterocycles (e) can additionally bear functional groups, preferably C 1-C4-alkoxy, amino
and/or mercapto. The basic heterocyclic skeleton can, of course, also bear alkyl groups, in particular C 1C4-alkyl groups.
[0046] Typical examples of heterocycles (e) are benzotriazole, tolutriazole (tolyltriazole), hydrogenated
tolutriazole, 1H-1,2,4-triazole, benzimidazole, benzothiazole, adenine, purine, 6-methoxypurine, indole,
isoindole, isoindoline, pyridine, pyrimidine, 3,4-diaminopyridine, 2-aminopyrimidine and 2mercaptopyrimidine.
[0047] For the tetra(C1-C8-alkoxy)silanes (f), tetramethoxysilane, tetraethoxysilane, tetra-n-propoxysilane
or tetra-n-butoxysilane may be used.
[0048] The amides (g) can optionally be alkyl-substituted at the nitrogen atom of the amide group, for
example by a C1-C4-alkyl group. Basic aromatic or heteroaromatic skeletons of the molecule can, of
course, also bear such alkyl groups One or more, preferably one or two, amide groups may be present in
the molecule. The amides can bear additional functional groups, preferably C 1-C4-alkoxy, amino, chlorine,
fluorine, hydroxyl and/or acetyl; such functional groups can be found in particular as substituents on
aromatic or heteroaromatic rings that are present.
[0049] Typical examples of such carboxamides and sulfonamides of group (g) are listed in DE-A 100 36
031.
[0050] In particular typical examples of such carboxamides and sulfonamides of group (g) are listed
below.
• aromatic carboxamides:
benzamide, 2-methylbenzamide, 3-methylbenzamide, 4-methylbenzamide, 2,4dimethylbenzamide, 4-tert-butylbenzamide, 3-methoxybenzamide, 4-methoxybenzamide, 2aminobenzamide (anthranilamide), 3-aminobenzamide, 4-aminobenzamide, 3-amino-4methylbenzamide, 2-chlorobenzamide, 3-chlorobenzamide, 4-chlorobenzamide, 2fluorobenzamide, 3-fluorobenzamide, 4-fluorobenzamide, 2,6-difluorobenzamide, 4hydroxybenzamide, phthalamide, terephthalamide;
• heteroaromatic carboxamides:
nicotinamide (pyridine-3-carboxamide), picolinamide (pyridine-2-carboxamide);
• aliphatic carboxamides:
succinamide, adipamide, propionamide, hexanamide;
• cycloaliphatic carboxamides having the amide group as a constituent of the ring:
2-pyrrolidone, N-methyl-2-pyrrolidone, 2-piperidone, ε-caprolactam;
• aliphatic sulfonamides:
methanesulfonamide, hexane-1-sulfonamide;
• aromatic sulfonamides:
benzenesulfonamide, o-toluenesulfonamide, m-toluenesulfonamide, p-toluenesulfonamide, 4-tertbutylbenzenesulfonamide, 4-fluorobenzenesulfonamide, 4-hydroxybenzenesulfonamide, 2aminobenzenesulfonamide, 3-aminobenzenesulfonamide, 4-aminobenzenesulfonamide, 4acetylbenzenesulfonamide.
[0051] In addition to the above-mentioned anticorrosion component of groups (a) to (g), it is also possible
to use, for example, soluble magnesium salts of organic acids, such as magnesium benzenesulfonate,
magnesium ethanesulfonate, magnesium acetate or magnesium propionate, hydrocarbazoles or
quaternized imidazoles, as they are described in DE-A 196 05 509, in customary amounts as further
inhibitors.
[0052] Of the above-listed additional ingredients of the antifreeze/anticorrosion concentrates according to
the invention, carboxylic acids of groups (a) and/or (b) and/or heterocycles of group (e) are preferably
also used.
[0053] In a particularly preferred embodiment, the antifreeze/anticorrosion concentrates according to the
invention each additionally comprise up to 5% by weight, in particular from 0.5 to 3% by weight, of two
different carboxylic acids from groups (a) and/or (b) and from 0.05 to 5% by weight, in particular from 0.1
to 0.5% by weight, of one or more heterocycles from group (e).
[0054] Such carboxylic acids that differ from each other can, for example, be mixtures of an aliphatic
monocarboxylic acid and an aliphatic dicarboxylic acid, of an aromatic monocarboxylic acid and an
aliphatic dicarboxylic acid, of an aliphatic monocarboxylic acid and an aromatic monocarboxylic acid, of
two aliphatic monocarboxylic acids or of two aliphatic dicarboxylic acids. Suitable heterocycles that are
preferably to be used additionally here are in particular benzotriazole and tolutriazole.
[0055] The pH value of the antifreeze concentrates according to the invention usually ranges from 4 to 11,
preferably from 4 to 10, and in particular from 4.5 to 8.5. The desired pH value can also optionally be
adjusted by adding alkali metal hydroxide, ammonia or amines to the formulation; solid sodium hydroxide
or potassium hydroxide and aqueous sodium hydroxide or potassium hydroxide solution are particularly
suited for this purpose.
[0056] Carboxylic acids to also be used preferably are expediently added directly as the corresponding
alkali metal salts in order to automatically be within the desired pH range. However, the carboxylic acids
can also be added in the form of free acids and then neutralized with alkali metal hydroxide, ammonia or
amines, and the desired pH range can be adjusted.
[0057] The antifreeze/anticorrosion concentrate according to the invention can also comprise, in
customary small amounts, antifoaming agents (generally in amounts from 0.003 to 0.008% by weight)
and, for reasons of hygiene and safety in the event that it is swallowed, bittering agents (for example of
the denatonium benzoate type) and dyes as additional customary auxiliary agents.
[0058] The antifreeze/anticorrosion concentrates according to the invention can be prepared by simple
mixing of the individual components.
[0059] The concentrates according to the invention can also be prepared from commercially available
superconcentrates, for example.
[0060] Another object of the present invention is thus s a process for preparing an antifreeze/anticorrosion
concentrate, comprising the step of
mixing an antifreeze superconcentrate comprising corrosion inhibitors with a glycerol component,
wherein the component comprises glycerol in an amount which results in 15 to 35% by weight,
based on the total amount of the mixture, in the resulting mixture, and wherein the resulting
mixture results in an antifreeze/anticorrosion concentrate according to the invention.
[0061] The weight ratio of the superconcentrate to the glycerol component preferably ranges from 5:1 to
1:50. More preferably, it is in the range from 1:1 to 1:20.
[0062] The amount of glycerol is preferably at least 15% by weight, and more preferably at least 20% by
weight, based on the total amount of the glycerol component. Further constituents can be customary
constituents of the antifreeze component, preferably ethylene glycol, and water.
[0063] Another object of the present invention are also aqueous coolant compositions having a depressed
freezing point, in particular for radiator protection of internal combustion engines in the automotive field,
which comprise water and from 10 to 90% by weight, and in particular from 20 to 60% by weight, of the
antifreeze/anticorrosion concentrates according to the invention.
[0064] Another object of the present invention is the use of coolant compositions according to the
invention in systems where the frost protection of water (generally for the range from 0°C to −40°C, in
particular from −20°C to −35°C) and simultaneously the corrosion protection of metal casings of watercontaining vessels are to be ensured. Here, primarily the cooling circuits of internal combustion engines,
in particular in automobiles such as passenger cars and trucks, are of interest. The coolant compositions
according to the invention, however, can also be used in stationary engines, in hot water circulation
systems of central heating systems, in resistance-heated radiators, in solar power circuits, but also in
coolant-cooled circulation systems.
Examples
[0065] The radiator protection agents HK1, HK2 and HK3 listed in the following examples are
commercially available, typical superconcentrates which have a comprehensively tested and proven
property profile. This property profile is further improved by admixing glycerol in contents according to the
invention.
Example 1 Determination of the Ice Flocculation Point of HK1 with/without Glycerol
[0066] HK1 is a mixture of 32.6 parts of ethylene glycol, 26.9 parts of aqueous potassium hydroxide
solution (50% by weight), 33 parts of ethylhexanoic acid, 2.2 parts of sodium molybdate dihydrate, 2.4
parts of tolutriazole, 2.8 parts of water and auxiliary agents (< 0.2 parts).
HK1 with glycerol % by
HK1 without glycerol %
Specification: British
weight
by weight
HK1
7
7
Glycerol
25
--
Ethylene Glycol
66
91
Water
2
2
-36.0ºC
-37.5ºC
Standard BS6580
Ice flocculation point,
ASTM D 1177
<-33ºC
concentration, 50% by
volume
[0067] The comparison shows that glycerol, as the antifreeze component in a blend with ethylene glycol,
allows specification-compliant antifreeze protection.
Example 2 Heat Transfer Corrosion Test of HK1 with/without Glycerol
[0068] The test is carried out according to ASTM D 4340 with HK1 with/without glycerol in the
composition as in Example 1 at a concentration of 25% by volume (water type: ASTM D 4340).
Cast aluminum test metal
Change in weight mg/cm 2
Appearance of the metal
HK1 with glycerol
-0.05
Gray tarnish, few deposits
HK1 without glycerol
+0.30
Light-color tarnish
Specification British Standard
<1
No information
BS6580
[0069] The comparison shows that the glycerol-containing mixture has a better corrosion result because
the change in weight of the aluminum test sample is lower.
Example 3 Dynamic Corrosion Experiment in the Hot Corrosion Circulation Apparatus
[0070] The hot corrosion circulation apparatus is designed analogously to the known apparatus according
to FW book R 443 1986. If modifications from the FW apparatus and test procedure are selected, they
are clear from the following tabular overview. For the purpose of the present invention, the more stringent
operating mode HK 96h was selected.
Specification
HK 96h
FW Book R 443 1986
Input hot chamber, ºC
95
80
Output hot chamber, ºC
105
-
Overpressure, bar
1.5
1.5
Temperature of the test liquid:
Flow rate, 1/h
210
260
Operating time, h
96
30
Volume of the test liquid, l
1
2.3
Heating output, W
2300
1500
Theoretical heat load density,
75
50
GALSi6Cu4
GG-26
(weight approx. 65 g)
GAISi10Mgwa
30
20/40
ASTM D 1384
10ºdGH
W/cm2
Material samples
Concentration of the test liquid,
% by volume
Type of water
[0071] A metal package as produced in ASTM D1384 was screwed together. Test liquid was introduced
into the vessel on a case-by-case basis so that the hot test liquid circulated around it. The metal package
consisted of the following metals and alloys, wherein the sequence of ASTM D1384 was observed, and
the additional metals were screwed next to the aluminum. The metal package consisted of the following
alloys:
Copper F-Cu, soft solder LPbSn30(Sb), brass Ms-63, steel II, gray cast iron GG-26, G-AlSi6Cu4, ALMn,
AL 99.5, G-ALSi12.
[0072] The metals were treated in a customary manner (which is to say as in ASTM D1384 or FVV
[German Research Foundation for Combustion Engines] R443 1986). The changes in weight were
recorded after the pickling unless indicated otherwise.
Example 4 Dynamic Corrosion Experiment with HK2 with/without Glycerol
[0073] The experiment was carried out as described in Example 3.
[0074] HK2 is a mixture of 87.8 parts of ethylene glycol, 5.4 parts of aqueous sodium hydroxide solution
(50% by weight), 1.3 parts of adipic acid, 5.0 parts of sebacic acid, 0.4 parts of tolutriazole, and auxiliary
agents (< 0.2 parts).
Mixture (180 g)
HK2 with glycerol
HK2 without glycerol
100 g HK2
100 g HK2
38 g ethylene glycol
80 g ethylene glycol
42 g glycerol
Change in weight of the
13 mg
36 mg
aluminum test sample (round
sample) HK96h KV23922
[0075] The comparison shows that the glycerol-containing mixture has a better corrosion result because
the change in weight of the aluminum test sample after an experiment duration of 96 hours is lower.
Example 5 Dynamic Corrosion Experiment with HK3 with/without Glycerol
[0076] The experiment was carried out as described in Example 3.
[0077] HK3 is a mixture of 81.5 parts of ethylene glycol, 5.9 parts of aqueous sodium hydroxide solution
(50% by weight), 5.4 parts of ethylhexanoic acid, 3.1 parts of sebacic acid, 0.03 parts of stabilized silicate,
2.7 parts of borax, 0.3 parts of benzotriazole, 0.7 part of sodium nitrate and auxiliary agents (< 0.4 parts).
Mixture (270 g)
HK3 with glycerol
HK3 without glycerol
100 g HK3
100 g HK3
107 g ethylene glycol
170 g ethylene glycol
63 g glycerol
Change in temperature of the
aluminum test sample (round
1ºC
5ºC
sample) HK96h KV23931
[0078] The comparison shows that the glycerol-containing mixture has a better corrosion result because
the increase in temperature of the aluminum test sample after an experiment duration of 96 hours is
lower.