KR100473217B1 - Antifreeze concentrates containing silicates, borates and nitrates, and cooling formulations containing them - Google Patents

Abstract

The present invention is a novel antifreeze concentrate free of silicates, borates and nitrates based on alkylene glycols or derivatives thereof, containing reaction salts containing the salts of carboxylic acids with hydrocarbon-triazole and / or -thiazole as main components. A novel antifreeze concentrate comprising the composition is disclosed. In particular, these antifreeze concentrates are completely free of any mineral acid salts as corrosion inhibitors. The present invention also relates to a ready-to-use aqueous coolant composition containing this antifreeze concentrate.

Description

Antifreeze concentrates containing silicate, borate and nitrate and coolant compositions containing them

The present invention is a novel antifreeze concentrates free of silicates, borates and nitrates based on alkylene glycols or derivatives thereof, the salts of carboxylic acids with hydrocarbon-triazole and / or -thiazole as main components. A novel antifreeze concentrate comprising a containing inhibitor composition. The present invention also relates to a ready-to-use aqueous coolant composition containing this antifreeze concentrate.

For example, antifreeze compositions for the cooling circulation of internal combustion engines in motor vehicles generally comprise alkylene glycols, in particular ethylene glycol or propylene glycol as the main component. For use in cooling systems it is intended to be diluted with water and to provide good heat dissipation as well as protection against freezing. However, alkylene glycol / water mixtures are highly corrosive at the operating temperature of the internal combustion engine and as a result are various types of corrosion, such as pitting, crevice corrosion, acid corrosion. It is necessary to adequately protect the various metals and alloys thereof present in the cooling system against erosion or cavitation by or the like. A large number of various chemicals are already known from the prior art for their use as corrosion inhibitors in such cooling systems.

As far as temperature stress, pressure, flow rate and material selection for the heat transfer zone are concerned, the operating conditions of modern internal combustion engines nowadays make much greater demands on the coolant's corrosion protection than ever before. . In addition to known materials such as copper, brass, wax, steel and gray cast iron, aluminum alloys are also increasingly used. As a result, recent patent literature claims that each has a specific spectrum of action, and includes many descriptions of specific combinations of active substances known for a long time.

EP-B 229 440 (1), for example, is an effective inhibitory agent in liquid alcoholic freezing point reducers for protecting aluminum alloys against viscosity, salts of hydrocarbon-triazoles, dibasic C ₅ -C ₁₆ hydrocarbon acids, and aliphatic Describe the combination of salts of monobasic C ₃ -C ₁₆ acids. In addition, simultaneous use of additional conventional inhibitors such as alkali metal borate, silicate, benzoate, nitrate, nitrite and molybdate, and / or hydrocarbazole is recommended.

EP-A 308 037 (2) discloses in particular antifreeze compositions for the protection of automotive radiators, which are water-soluble liquid alcoholic freezing point reducers, salts of C ₆ -C ₁₂ aliphatic monobasic acids, alkali metal borates and hydrocarbon-triazoles. And the composition is derived from the results of electrochemical measurements, the composition protects the metals in particular against pitting. It is also possible in this document to use additional conventional inhibitors such as alkali metal benzoates, silicates, nitrates and molybdates.

GB-B 1 004 259 (3) discloses a combination of dicarboxylic acids, such as sebacic acid, and hydrocarbon-triazoles, such as benzotriazole, as corrosion inhibitors, for example in the form of amine salts. At the same time the use of additional inorganic inhibitors such as borax is also recommended.

EP-A 035 834 (4) discloses a corrosion inhibitor mixture consisting of triazoles, alkali metal borates, alkali metal benzoates, alkali metal silicates and alkali metal salts of C ₇ -C ₁₃ dicarboxylic acids.

US-A 4 587 028 (5) discloses a silicate free antifreeze composition consisting of alkali metal benzoates, alkali metal nitrates and alkali metal salts of C ₈ -C ₁₂ dicarboxylic acids as corrosion inhibitors.

EP-B 251 480 (6) discloses antifreeze concentrates wherein the corrosion inhibitor is alkylbenzoic acid or a salt thereof, monobasic aliphatic C ₈ -C ₁₂ acid or a salt thereof and a hydrocarbon-triazole. It is also recommended to use additional inhibitors simultaneously, such as borates, silicates, nitrates, nitrites or molybdates of alkali metals.

EP-A 369 100 (7) is a corrosion inhibitor for use in coolant compositions containing ethylene glycol and diethylene glycol in a ratio of 90:10 as alcoholic freezing point decane acid, dodecanedioic acid and tolutriazole. The mixture of is described.

It is known that borate salts can have a very bad effect on corrosion protection against aluminum under heat-surface stress. If silicate is present, this adverse effect does not occur. Thus, under optimal conditions, the borate and silicate are in a balanced ratio. If the ratio of silicate to borate is too low, the corrosion-inhibiting action of the whole mixture is impaired. In addition, as a result of precipitation of insoluble silicate modifications, for example as a result of insufficient silicate stabilization, a deficiency of silicates inherently present in the coolant formulation may occur during service, which may lead to a decrease in the soluble silicate ratio.

It is therefore an object of the present invention as an inhibitor system for a coolant composition that is effective without sensitive inorganic inhibitor materials of this kind, ie without salts of inorganic acids, in particular without alkali metal borate and alkali metal silicate, and all metals used in engine production. It is to provide an inhibitor system for a coolant composition that provides adequate protection against corrosion, but especially against aluminum, under high heat-surface stress.

Applicants have found that this object is achieved by antifreeze concentrates free of silicates, borate and nitrates based on alkylene glycols or derivatives thereof, consisting of:

(a) 0.05 to 10% by weight, preferably 0.1 to 5% by weight, based on the total amount of the concentrate, at least one carboxylic acid having 3 to 16 carbon atoms in the form of an alkali metal salt, ammonium salt or substituted ammonium salt, And

(b) 0.01 to 3% by weight, preferably 0.05 to 1% by weight, based on the total amount of the concentrate, of at least one hydrocarbon-triazole and / or hydrocarbon-thiazole, in particular benzotriazole and / or tolute Riazole.

In a preferred embodiment the new antifreeze concentrate is completely free of salts of any inorganic acid that are effective corrosion inhibitors. In particular it contains no alkali metal phosphates, alkali metal molybdates and alkali metal nitrites at all.

In a more preferred embodiment component (a) is a mixture of at least two carboxylic acids. If this mixture comprises, for example, two carboxylic acids, its weight ratio is usually 1:99 to 99: 1, in particular 3:97 to 97: 3.

(a) is particularly preferably a mixture of two dicarboxylic acids, in particular two aliphatic dicarboxylic acids.

(a) is also particularly preferably a mixture of two monocarboxylic acids, in particular one aliphatic monocarboxylic acid and one aromatic monocarboxylic acid.

(a) is also particularly preferably a mixture of monocarboxylic and dicarboxylic acids, especially branched aliphatic monocarboxylic acids and aliphatic dicarboxylic acids.

Particularly suitable dicarboxylic acids are those of 4-16 carbon atoms, in particular 8-12 carbon atoms, examples of which are subric acid, azelleic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, dicyclopentadienedicarboxylic acid , Phthalic acid and terephthalic acid.

Particularly suitable straight and branched aliphatic monocarboxylic acids are those of 5-12 carbon atoms, examples of which are pentanoic acid, hexanoic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, 2-ethylhexanoic acid Laoshan and isononanosan.

Particularly suitable aromatic monocarboxylic acids are those of 7-16 carbon atoms, in particular benzoic acid, alkylbenzoic acids having 1-8 carbon atoms in the side chain, such as o-, m- or p-methylbenzoic acid, hydroxy aromatic monocarboxylic acids such as o -, m- or p-hydroxybenzoic acid and o-, m- or p- (hydroxymethyl) benzoic acid.

Such carboxylic acids are present in the form of their alkali metal salts, in particular sodium or potassium salts, or as salts with ammonium salts or substituted ammonium salts (amine salts) such as trialkylamines or trialkanolamines.

Carboxylic acids which can be used according to the invention generally do not comprise functional groups other than carboxyl groups and possibly hydroxyl groups. This carboxylic acid may only contain ether oxygen and / or carbonyl functional groups. However, it should not contain halogen or nitrogen functional groups such as nitro or amino.

The new silicate, borate and nitrate free antifreeze concentrate may comprise additional corrosion inhibitors in an amount of up to 2% by weight, in particular 0.001 to 1% by weight, of the total amount of the concentrate, the inhibitor being at least one 4 And quaternized imidazoles. Such quaternized imidazoles are described in German Patent Application No. 196 05 509. Examples of this are 1-methylimidazole, 1-ethylimidazole, quaternized with benzyl chloride, benzyl bromide, methyl chloride, methyl bromide, ethyl chloride, ethyl bromide, diethyl sulfate, or especially dimethyl sulfate , 1- (β-hydroxyethyl) imidazole, 1,2-dimethylimidazole, 1-phenylimidazole, benzimidazole, and especially N-vinylimidazole.

The new silicate, borate and nitrate free antifreeze concentrates may further comprise additional corrosion inhibitors in amounts up to 2% by weight of the total amount of the concentrate, in particular from 0.001 to 1% by weight, which inhibitors may be organic acids, in particular At least one soluble magnesium salt of carboxylic acid. Examples of such magnesium salts are magnesium benzenesulfonate, methanesulfonate, acetate and propionate.

In addition to the above inhibitor components, it is also possible to use, for example, conventional amounts of hydrocarbazole.

The total corrosion inhibitor component may comprise up to 15% by weight, in particular up to 10% by weight of the total amount of concentrate, with the concentration of each component being up to 10% by weight, in particular up to 5% by weight.

Furthermore, new silicate, borate and nitrate free antifreeze concentrates may additionally comprise up to 1% by weight, in particular 0.01-0.5% by weight, of hard water stabilizers, based on the total amount of the concentrate, These hard water stabilizers include polyacrylic acid, polymaleic acid, acrylic acid-maleic acid copolymers, polyvinylpyrrolidone, polyvinylimidazole, vinylpyrrolidone-vinylimidazole copolymers and / or unsaturated carboxylic acids and olefins. Is based on a copolymer of.

The pH of fresh silicate, borate and nitrate free antifreeze concentrates is typically 7-10, preferably 7.5-9.5, in particular 8.0-9.0. The desired pH is generally established by adding alkali metal hydroxides, ammonia or amines to the formulation, and solid sodium hydroxide and potassium hydroxide, and aqueous sodium and potassium hydroxide solutions are particularly suitable for this purpose.

Aliphatic or aromatic mono- and / or dicarboxylic acids are usefully added in the form of the corresponding alkali metal salts to automatically establish the desired pH range; However, it is also possible to add the free carboxylic acid and then neutralize it with alkali metal hydroxide, ammonia or amine and establish the desired pH range.

Liquid alcoholic freezing point reducers which normally make up the major part of the new antifreeze concentrate (generally at least 80% by weight, in particular at least 90% by weight) are suitably alkylene glycols or derivatives thereof, in particular propylene glycol, in particular ethylene glycol. However, higher glycols and glycol ethers are also suitable, examples being diethylene glycol, dipropylene glycol, and methyl, ethyl, propyl, of ethylene glycol, propylene glycol, diethylene glycol and dipropylene glycol as monoethers of glycol. Butyl ether and the like. It is also possible to use mixtures of these glycols and glycol ethers. Preferably, it is given as ethylene glycol itself or as a mixture comprising at least 95% by weight of ethylene glycol, ie as a mixture of ethylene glycol, ie ethylene glycol, propylene glycol, higher glycols and / or glycol ethers.

The present invention also relates to ready-to-use aqueous coolant compositions with reduced freezing point, particularly for the protection of radiators in the automotive sector, wherein 10-90% by weight, preferably 20-60, of the free silicate concentrates free of silicate, borate and nitrates. It relates to including by weight and water.

Example

The present invention is illustrated with reference to Examples A, B and D and Comparative Example C of the present invention. Table 1 shows the compositions of exemplary inhibitor mixtures in ethylene glycol. This antifreeze concentrate was diluted with water and subjected to conventional corrosion test. C is a commonly available prior art antifreeze (in addition to benzoate and tolutriazole) having a significant amount of inorganic inhibitor component.

The corrosion protection capability of the antifreeze concentrates of the compositions of Examples A to D was evaluated using the ASTM D 4340 corrosion test and the German Engine and Turbine Union (MTU) thermal corrosion test.

TABLE 1

Composition (wt%) of antifreeze concentrate

The extremely good protection provided for aluminum is evident from the test results shown in Table 2. The increase in weight found in the new compositions A and B in the ASTM D 4340 test indicates the formation of a stable protective coating layer, while Formulation C shows a significant weight reduction, ie removal of material, especially under test conditions. Under very stringent conditions of the MTU thermal corrosion test, Formulation C shows significant defects, while new products A, B and D show significantly improved protection, i.e. less removal of material.

TABLE 2

Test results

The present invention is an inhibitor system for a coolant composition, which is effective without any sensitive inorganic inhibitor material of this kind, ie without salts of inorganic acids, in particular without alkali metal borate and alkali metal silicate, but for all metals used in engine production, but It provides adequate protection against corrosion against aluminum, especially under high heat-surface stresses.

Claims (8)

Based on alkylene glycols or derivatives thereof, (a) a mixture of aliphatic monocarboxylic acid and hydroxyl containing aromatic monocarboxylic acid having from 3 to 16 carbon atoms in each case in the form of an alkali metal salt, ammonium salt or substituted ammonium salt, based on the total amount of the concentrate, 0.05 To 10% by weight, (b) containing 0.01 to 3% by weight, based on the total amount of the concentrate, of at least one hydrocarbon-triazole and / or hydrocarbon-thiazole, Antifreeze concentrate without silicate, borate and nitrate. The concentrate of claim 1, wherein the concentrate is free of additional inorganic acid salts. The concentrate of claim 1 or 2, further comprising up to 2% by weight of one or more quaternized imidazoles, based on the total amount of the concentrate. The concentrate of claim 1 or 2, further comprising up to 2% by weight, based on the total amount of the soluble magnesium salt of at least one organic acid. The polyacrylic acid, polymaleic acid, acrylic acid-maleic acid copolymer, polyvinylpyrrolidone, polyvinylimidazole, vinylpyrrolidone-vinylimidazole copolymer according to claim 1 or 2 And / or a hard water stabilizer based on a copolymer of unsaturated carboxylic acid and olefin up to 1% by weight based on the total amount of the concentrate. The concentrate of claim 1 or 2, having a pH of 7-10. The concentrate according to claim 1 or 2, characterized in that it is based on ethylene glycol or a mixture of ethylene glycol containing at least 95% by weight of ethylene glycol. A ready-to-use aqueous coolant composition with reduced freezing point comprising 10-90% by weight of concentrate according to claim 1 or 2.