MXPA01000019A - Antifreeze concentrates and coolant compositions containing these concentrates for cooling circuits in internal combustion engines - Google Patents

Abstract

The invention relates to antifreeze concentrates which are characterized in that they a) comprise at least one alcohol which can be mixed with water and which lowers the freezing point;b) at least one corrosion inhibitor;and c) at least one mononuclear or polynuclear aromatic component which carries at least one hydroxyl group, has a high buffering capacity in the pH range of approximately 6 to 10, and which is used as a reserve alkalinity dispenser. The invention also relates to coolant compositions containing these antifreeze concentrates for cooling circuits in internal combustion engines.

Description

CONCENTRATED ANTIFREEZE AND LIQUID COOLERS FOR ENGINES THAT UNDERSTAND THEM DESCRIPTION OF THE INVENTION The present invention relates to novel antifreeze concentrates based on alkylene glycols and aqueous compositions ready for use liquid coolers which comprise concentrates and are intended for cooling circuits in internal combustion engines. Coolant fluids for the cooling circuits of internal combustion engines such as motor vehicles generally include alkylene glycols especially ethylene glycol or propylene glycol, or any corresponding glycol ethers. For use in the cooling system they are diluted with water and are intended not only to provide controlled protection by lowering the freezing point of the water but also to contribute to good heat dissipation. The alkylene glycol / water mixtures, however, are extremely corrosive to the operating temperatures of internal combustion engines and thus the various metals used to build cooling systems must be protected against corrosion. With regard to the thermal load of the areas of pressure transfer, flow velocity, and material selection, the operating conditions in today's modern internal combustion engines place far greater demands on capacity. of the 5 prevention of liquid coolant corrosion that to date was the case. In addition to the known materials such as copper, bronze, tin solder, steel, and gray cast iron, there is also the increasing use of aluminum alloys for the purpose, in particular, of reducing weight. Consequently, there is an increased occurrence in the most recent literature of descriptions of specific combinations of long-known active substances, each claiming to have a specific spectrum of action. In particular, the alkali metal silicates are have found excellent to protect the aluminum against corrosion. In glycol-based radiator protectors, however, they tend to form gels or even precipitate, thus creating a need for special silicate stabilizers. Examples of constituents of such combinations of active substances include salts of organic acids which, especially in the form of their alkali metal salts, are efficient corrosion inhibitors, while free acids are less effective or can still be corrosives. The incidence of free acids in Jí ^^^^^ ^^ i ^^^^? ^^^^ radiators protecting formulations as a possible result, for example, oxidation processes or nitrous gases entering into the cooling system is therefore highly undesirable. It is for this reason that the protective formulations of radiators contain small quantities of agents known as alkalinity reserve donors which have a regulatory action in the relevant pH range and thus prevent the formation of free acids. Examples of compounds used as alkalinity reserve donors are amines and phosphates and, in particular, less expensive borax. Such inhibiting compositions corrosion are described for example in EP-B-0229440 and EP-A-0 308 037. Due to the above described disadvantages associated with the use of silicates as corrosion inhibitors for aluminum in developments In recent years, there has been a tendency to omit them and use other active substances instead. Under these conditions, however, the reserve donor of alkalinity, borax, is highly corrosive, and can thus no longer be used. The use of phosphates in the protective formulations of modern radiators is in the same undesirable way. This applies even more to amines, based on their characterization as potential nitrosamine formers. O-A-96/18757 describes compositions anticorrosive to temporarily protect metallic surfaces, especially those that include iron, against corrosion. The compositions are aqueous solutions comprising a combination of a carboxylic acid anion of 6 to 44 carbon atoms with an aromatic hydroxy compound having a pKa for the hydroxyl group in the range of 7.0 to 11, in a weight ratio of 1. : 2 to 20: 1. Corrosion inhibitor systems of this type, however, are not intended for use in cooling systems containing alkylene glycol for internal combustion engines. Instead, it is proposed that they be used in aqueous treatment baths in which the articles to be treated, for example, steel sheets, are immersed. As a result, there continues to be a need for improved antifreeze concentrates. It is an object of the present invention to provide silicate-free antifreeze concentrates which comprise new alkalinity reserve donors and which are not hampered by the disadvantages described above. Antifreeze concentrates must in particular exhibit increased corrosion inhibition in aluminum or its alloys. It has been found that this object is achieved by taking conventional silicate-free inhibitor systems for glycol-containing protective formulations of radiators ? üásá? - ¿ME ¿& iirn *****. *. and replacing the customary alkalinity reserve donors, such as borates, phosphates and amines, by the mono- or polycyclic aromatic compound having at least one hydroxyl group and a high regulatory capacity in the pH range of about 6 to 10. The present invention therefore provides, in particular, antifreeze concentrates which comprise a) at least one water-miscible alcohol which lowers the freezing point, preferably selected from alkylene glycols and alkylene glycol ethers; b) at least one corrosion inhibitor; and c) as an alkalinity reserve donor, at least one mono- or polycyclic aromatic compound which has at least one hydroxyl group and a high buffer capacity in the pH range of about 0 to 10. Such antifreeze concentrates and the compositions of Ready-to-use coolant liquids prepared with them have the surprising advantage over conventional formulations of a remarkably better corrosion inhibiting effect. In particular, an improvement in the corrosion stability of aluminum materials as used in the construction of engines is observed. ^^^^^ jteftfe% * fcg¡alj ^ si «i In a preferred embodiment, antifreeze concentrates of the invention comprise as alkalinity reserve donor at least one compound of the formula '.'. Ar-X (I) where Ar is a radical of formula II wherein n is an integer from 0 to 4 and R1 is hydrogen or an alkali metal ion, and substituents R2 independently of one another are a hydroxyl, alkyl, hydroxyalkyl, heteroalkyl or hydroxyheteroalkyl group, and X is -COOH, - S03H or -S02Ar, where Ar is as defined above. Preferred compounds of the formula I include Ar radicals of the formula II wherein n is 0, 1 or 2. The substituents R 2 on the ring, where present, are preferably independently of one another hydroxyl or hydroxyalkyl group. The radical X is preferably -S02Ar, where Ar can be as defined above. An alkalinity reserve donor which is particularly preferred according to the invention is «^^ fc selects from the compounds of formula III wherein R1, R2 and n independently of one another are as defined above. In the compounds of formula III R is preferably hydrogen, n is preferably 0, 1 or 2, and R 2, if present is preferably hydroxy or hydroxyalkyl. The compounds of formula III are preferably symmetrical; that is, the two aromatic rings are replaced symmetrically to the mirror starting from the central group S02. 1C Particular preference is given to the compounds of formula III wherein the radicals R1 are identical and are hydrogen or an alkali metal and n in each case is 0. Specific examples of such compounds are 4,4'-dihydroxydiphenylsulfone (bisphenol S) and the isomers of corresponding positions, and also the mixtures of these compounds. Where R1 in the above-mentioned compounds of the formula I is not hydrogen, it is preferably a monovalent metal cation, especially an alkali metal cation such as, for example, a sodium or potassium cation. Where two or more radicals R1 are present, they are preferably the same metal cation alkaline Suitable alkyl radicals according to the invention are branched carbon chains or linear chains having 1 to 10, preferably 1 to 6 and in particular 1 to 4 carbon atoms. Examples that may be mentioned include the following radicals: methyl, ethyl, n-propyl, i-propyl, n-butyl, sec-butyl, i-butyl, t-butyl, n-pentyl, sec-pentyl, isopentyl, n- hexyl, 1-, 2- or 3-methyl-pentyl, and long-chain alkyl radicals, such as ethyl, octyl, nonyl and non-branched decyl, as well as the branched analogues individually or in multiple forms thereof. Suitable hydroxyalkyl radicals according to the invention are preferably alkyl radicals containing hydroxyl as defined above. They may contain from 1 to 10, preferably from 1 to 3, and in particular a hydroxyl group, of at least one hydroxyl group is preferably in the terminal position, ie, attached to a primary carbon atom. The heteroalkyl radicals which may be used according to the invention are alkyl groups as defined above in which at least one heteroatom selected from S, N and O, preferably O is present in the alkyl chain. Examples of heteroalkyl groups Particularly preferred are methoxymethyl and ethoxyethyl groups. The hydroxyheteroalkyl groups which can be used according to the invention are heteroalkyl groups as defined above in which at least 1 to 10, such as 1 to 3, hydroxyl groups, especially 1 hydroxyl group, are / is attached to the chain heteroalkyl. Possible examples of such radicals are hydroxyethyl-oxyethyl and hydroxymethyloxymethyl. C The aforementioned alkyl, hydroxyalkyl, heteroalkyl and hydroxyheteroalkyl groups according to the invention may also, if desired, be attached to the aromatic ring by means of a heteroatom, preferably an oxygen atom. In another preferred embodiment of the invention antifreeze concentrates comprise as corrosion inhibitors at least one compound selected from triazoles, thiazoles, and mono- or polybasic carboxylic acids, aliphatic or aromatic or carboxylic salts, and mixtures of C these compounds. Examples of thiazoles and triazoles that can be used according to the invention are derivatives of these compounds having a fused ring system, preferably aromatic. Particular mention may be made of benzotriazole, benzothiazole, tolutiazole and tolutriazole. a- * Mfe_t-fafaal, t ... JVt¿ ^. ^. * ^ ** B & - The aforementioned thiazoles and the triazoles may be present individually or in a mixture in the antifreeze concentrates of the invention.

They may also be present as a mixture with at least one carboxylic acid of the type specified above. Examples of suitable carboxylic acids according to the invention are straight or branched chain aliphatic monocarboxylic acids of 5 to 12 carbon atoms, examples being pentanoic, hexanoic, octanoic, nonanoic, decanoic, undecanoic, dodecanoic, 2-ethylhexanoic and isononanoic acid . The aromatic monocarboxylic acids suitable according to the invention are, in particular, those of 7 to 16 carbon atoms. Possible examples are benzoic acid, alkylbenzoic acids wherein the alkyl portion is as defined above, such as the o-, m-, and p-methylbenzoic acid and hydroxyl-containing analogs of the above aromatic monocarboxylic acids, such as acid or -, m-, or p-hydroxybenzoic, and o-, m-, and p- (hydroxymethyl) benzoic acid. The aforementioned carboxylic acids which can be used according to the invention can if desired be further substituted by ether oxygen-containing groups, such as alkoxyalkyl groups, or by functional carbonyl groups, such as alkylcarbonyl groups, the alkyl portion in each case being cerno was previously defined. The carboxylic acids usable according to the invention can be added individually or as a mixture to the anti-freeze concentrates of the invention. Particular preference is given to mixtures of at least two carboxylic acids of the aforementioned type. Two carboxylic acids are preferably present in a molar ratio of about 1:99 to 99: 1, in particular 0 of 3:97 to 97: 1. A particularly preferred mixture is that of two dicarboxylic acids, especially two aliphatic dicarboxylic acids, and / or their salts, especially alkali metal salts, such as sodium or potassium salts, for example. The additional carboxylic acid mixtures usable according to the invention comprise a mixture of two monocarboxylic acids, especially of an aliphatic monocarboxylic acid and an aromatic one, and mixtures of a monocarboxylic acid with a dicarboxylic acid, especially an aliphatic dicarboxylic acid with an acid branched aliphatic monocarboxylic. As a specific example of a carboxylic acid mixture which can be used according to the invention, mention may be made of a mixture of sebasic and adipic acids.

Suitable mixtures according to the invention and comprising triazole and / or thiazole-containing carboxylic acids are described in the earlier EP-A-0 816 467, the content of which is expressly incorporated herein by reference. Suitable mixtures comprise, for example, at least one carboxylic acid of the type designated above and at least one thiazole or triazole of the type designated above, in a quantitative ratio of about 1:20 to about 20: 1, particularly about 1: 15 to about 15: 1. The antifreeze concentrates of the invention commonly include the alkalinity reserve donor (s) of formula I above in a proportion of about 0.05 to 4% by weight, preferably about 0.5 to 3% by weight and, in particular, about 0.8 to 2% by weight. The aforementioned corrosion inhibitors, ie, carboxylic acids, thiazoles and / or triazoles, are commonly present in a total proportion of from about 0.1 to 20% by weight, in particular from 0.5 to 10% by weight, based on the total weight of the concentrate. In this case the carboxylic acids of the type referred to above can be present in a proportion of about 0.05 to 10% by weight, preferably 0.1 to 5% by weight, in > ? ßá? iaar eJÉá ¡k i¡ái? based on the total weight of the concentrate. The triazoles and / or thiazoles are commonly present in a proportion of 0.01 to 3% by weight, preferably 0.5 to 1% by weight, based on the total weight of the concentrate. As additional corrosion inhibitors, the antifreeze concentrates of the invention may include up to 2% by weight, in particular from 0.001 to 1% by weight, based on the total weight of the concentrate, of at least one quaternized imidazole. Such quaternized imidazoles are described in 0 DE-A-196 05 509. Examples are 1-methylimidazole, 1-ethylimidazole, 1- (β-hydroxyethyl) imidazole, 1,2-dimethylimidazole, 1-phenylimidazole, benzimidazole, and in particular, NI-vmilimidazole quaternized with benzyl chloride, benzyl bromide, methyl chloride, methyl bromide, ethyl chloride, ethyl bromide, diethyl sulfate and, in particular, dimethyl sulfate. As additional corrosion inhibitors, the antifreeze concentrates of the invention may include up to 2% by weight, in particular from 0.001 to 1% by weight, in C based on the total weight of the concentrate, of at least one soluble magnesium salt of acids organic, especially carboxylic acids. Examples of such magnesium salts are magnesium benzenesulfonate, magnesium methanesulfonate, magnesium acetate and magnesium propionate. 5 In addition to the specified inhibitory components it is also possible, for example, to employ hydrocarbons in the customary amounts. The anti-freeze concentrates of the invention may additionally include up to 1% by weight, in particular from 0.01 to 0.5% by weight, based on the total amount of concentrate, of hard water stabilizers based on polyacrylic acid, polymaleic acid, copolymers of acrylic acid, maleic acid, polyvinylpyrrolidone, polyvinylimidazole, vinylpyrrolidone-vinylimidazole copolymers, and / or copolymers of carboxylic acids and unsaturated olefins. The pH of the antifreeze concentrates of the invention usually reside within the range of 7 to 10, preferably 7.5 to 9.5 and, in particular, 8.0 to 9.5. The desired pH is generally established by adding alkali metal hydroxide, ammonia or amines to the formulation, with solid sodium hydroxide and potassium hydroxide and also aqueous sodium and potassium hydroxide solutions being particularly suitable for the purpose. The mono- and / or dicarboxylic aliphatic or aromatic dicarboxylic acids are judiciously added diry as the corresponding alkali metal salts to reside automatically in the desired pH range. Alternatively, these carboxylic acids can be added as free acids, after which the formulation is neutralized with alkali metal hydroxide, ammonia or amines and the desired pH range is established. Similar comments apply to the alkalinity reserve donors of the formula I, which may be employed as alcohols or in the form of the corresponding alkali metal salts. The partial conversion of the compounds into their salts would be in the same conceivable way. The appropriate liquid alcohol freezing point reducers, which normally 1C characterize the majority (generally at least about 80% by weight, in particular about 90% by weight) of the antifreeze concentrates of the invention are alkylene glycols or derivatives thereof, especially propylene glycol and, in particular, ethylene glycol. However, high glycols and glycol ethers are also suitable, examples being diethylene glycol, dipropylene glycol, and glycol monoethers, such as methyl, ethyl, propyl and butyl ether of ethylene glycol, propylene glycol, diethylene glycol and dipropylene glycol. It is also possible to use mixtures of these glycols and glycol ethers. Preference is given to ethylene glycol alone or to mixtures of alkylene glycols, ie ethylene glycol, propylene glycol, higher glycols and / or glycol ethers, containing at least 95% by weight of ethylene glycol. The present invention also provides, liquid coolant compositions ready for use of reduced freezing point, especially for protection of radiators in the automotive sector, which comprise water and from 10 to 90% by weight, preferably from 20 to 60% by weight of silicate and borate-free anti-freeze concentrates of the invention. The present invention further provides the use of compounds of the formula I as alkalinity reserve donors in chilled liquor compositions based on alkylene glycols or alkylene glycol ethers, the coolant compositions being essentially free of silicate and borate. The present invention is currently illustrated by the following examples.

EXAMPLES The anti-freeze concentrates of the invention 2, 3 and 4 and the comparative concentrates Cl, C5, C6 and C7 described in Table 1 were prepared and tested for their corrosion protection effect. The experimental data are summarized in the attached Table 2.

Table 1: Composition of used antifreeze concentrates i; H02C- (CH2) 8-C02H 2: H02C- (CH2) 4-C02H 3: Parts by weight Table 2: Technical data and test results 1) In accordance with ASTM D 1121 (10 ml concentrate) 2) Quantity (ml) of 0.1 N HCl consumed 3) According to ASTM D 384 for a 33 volume solution in H20 4) Weight change in mg / cm2 5) According to MTU; for a solution at 20% by volume in H20 6) Weight change in Mg / sample The results established in Table 2 of the determination of the reserve alkalinity according to ASTM D 1121 clearly illustrate the effectiveness of the hydroxydiphenylsulfone additive used in according to the invention. Although the level of effectiveness of borax is not exactly achieved (Example 5), the performance is remarkable relative to the formulations (Examples 1, 6, 1), without an additive of the invention. Corrosion tests according to ASTM D 1384 illustrate that the additive treatment produced for the radiator protective formulations according to the invention has no adverse effect on the corrosion behavior and that in the case of molten aluminum, it can truly get a slight improvement. Table 2 also shows results obtained in the dynamic hot chamber corrosion test of the MTU (German Engine and Turbine Union), a test with high thermal load. Here, a very high corrosion ratio for borax-containing formulation 5 is found while much lower values are found for the formulations of the invention, especially in Examples 3 and 4. b) For the next series of tests it was prepared a concentrate of active substance according to Example 7 of OA-96/18757 (50.1 parts of monoethylene glycol, 24.9 parts of 50% solution of potassium hydroxide, 20 parts of sorbic acid and 5 parts of bisphenol S) and was investigated in a corrosion test according to ASTM D 1384. For this test a 33% solution was prepared ( V / V) of the mixture in distilled water, and 0.05 parts by weight of tolutriazole. The results are summarized in Table 3 below. Table 3: ASTM D 1384 - Result ? A? My &fSf * ».. -ayi.fe .- ..« £.,.? The results show that it is impossible to obtain satisfactory corrosion protection on the basis of a composition according to O-AA-96/18757. ? ÉHÉ ^^^ ggg ^^^ H tffiÉ.M.ftifltfhtrr? R • üiifpt ^

Claims (10)

1. CLAIMS 1. An antifreeze concentrate comprising a) at least one water-miscible alcohol that lowers the freezing point; 5 b) at least one corrosion inhibitor; and c) an alkalinity reserve donor, at least one mono- or polycyclic aromatic compound having at least one hydroxyl group and a high regulatory capacity in the pH range of 1C about 6 to 10, which is selected from the compounds of the formula III or wherein n is an integer from 0 to 4 and R1 is hydrogen or an alkali metal ion, and the substituents R2 independently of one another are a hydroxyl, alkyl, hydroxyalkyl, heteroalkyl or hydroxyheteroalkyl group.
2. 2. The anti-freeze concentrate as claimed in claim 1, wherein the alkalinity reserve donor is selected from 4,4'- and 2,4'- dihydroxydiphenylsulfone and mixtures thereof.
3. 3. The antifreeze concentrate as claimed in any of the present claims, which comprises at least one alkalinity reserve donor of Formula III in a proportion of about 0.05 to 4% by weight, based on the total weight of the concentrate.
4. 4. The antifreeze concentrate as claimed in any of the present claims, wherein the corrosion inhibitor is selected from triazoles, thiazoles and mono- or polybasic aliphatic or aromatic carboxylic acids and their salts, and mixtures of these compounds.
5. 5. The antifreeze concentrate as claimed in claim 4, which comprises at least one corrosion inhibitor in a proportion of about 0.1 to 20% by weight, based on the total weight of the concentrated concentrate.
6. 6. The antifreeze concentrate as claimed in any of the present claims, wherein the alcohol decreases the freezing point tl ^ a * ****** ^^ inirr i i-Mili? n.il? l? - ^ ^ ^^^ ^ ¡n ^! 2¿ ^^ g? J is selected from alkylene glycols and alkylene glycol ethers, and mixtures thereof.
7. 7. The anti-freeze concentrate as claimed in any of the preceding claims, which is essentially free of borate and silicate.
8. 8. The coolant composition comprising an antifreeze concentrate as claimed 10 in any of the preceding claims.
9. 9. The use of a compound of formula III as an alkalinity reserve donor in a liquid coolant composition based on alkylene glycols or 15 alkylene glycol ethers.
10. 10. The use as claimed in claim 9, wherein the composition of the coolant liquid is, in addition, essentially free of borate and silicate.