EP0786019B1 - Use of guanidine salts of unsaturated fatty acids as anticorrosive active substances - Google Patents

Abstract

PCT No. PCT/EP95/03931 Sec. 371 Date Apr. 14, 1997 Sec. 102(e) Date Apr. 14, 1997 PCT Filed Oct. 5, 1995 PCT Pub. No. WO96/12054 PCT Pub. Date Apr. 25, 1996A method for the temporary protection of metal surfaces from corrosion is provided in which the metal surface to be temporarily protected from corrosion is coated with a guanidinium salt of an unsaturated fatty acid containing 6 to 44 carbon atoms.

Description

The invention relates to oil-based anti-corrosion agents for metallic, especially iron-based surfaces, preferably in the form of oil-in-water emulsions are used. The invention provides alkylamine free Corrosion protection agents are available, which are characterized by good Characterize oil solubility and at the same time the emulsification of the oil phase effect in water.

Anti-rust emulsions are used for the temporary protection of metallic materials against atmospheric influences that cause corrosion. she essentially contain non-polar or polar oils, emulsifiers, corrosion inhibitors and water. Their effect is based on the adsorption of inhibitor molecules on the metal surface and the formation of a protective film from emulsion components, which acts as a diffusion barrier for atmospheric oxygen as well as water works. T. Forster et al. report in "Surface-Surface", 1989, No. 4, pp. 8-12, on modes of action and investigation methods of anti-rust emulsions.

Previously used corrosion protection agents contain components such as for example petroleum sulfonates, salts of alkylsulfonamidocarboxylic acids and Amine or other salts of partial esters of alkyl or alkenyl succinic acid. For example, EP-A-566 956 describes anti-corrosion agents based on an amine-free salt of a half-ester of an alkyl or Alkenyl succinic acid.

Sulfur-containing corrosion inhibitors such as alkylarylsulfonic acids, Petroleum sulfonates or salts of alkyl sulfonamido carboxylic acids show the disadvantage that they are easily from microorganisms, such as sulfur-reducing Bacteria can be broken down, causing significant odor nuisance can lead. Corrosion protection agents containing alkylamine, in particular those with secondary amines, because of the risk of formation health-endangering nitrosamines are increasingly viewed critically. Therefore there is a need for sulfur and alkylamine-free anti-corrosion agents. For purely oily systems, for example for lubricating oils and Lubricating greases, stearic acid derivatives have been described as anti-corrosion agents (DE-C-32 03 491). Examples include 9,10-dihydroxystearic acid and their alkali salts and their oligomeric condensates, 9,10-epoxistearic acid, their alkali salts and their oligomeric estolides and finally mixed oligomerizates of 9,10-epoxy and 9,10-dihydroxystearic acid.

Anticorrosive in the form of oil-in-water emulsions for use should come as pure oily, i.e. water-free concentrates to be placed on the market by adding water at the location of the Application to be brought into the ready-to-use emulsion form. This Oil concentrates contain the corrosion inhibitors, which are therefore oil-soluble have to be. So that the oil concentrates spontaneously when diluted with water form an emulsion, so it can be self-emulsifying, it was previously required that these concentrates in addition to the corrosion inhibitors Contain emulsifiers. Possible interactions between the surface active Emulsifiers and the polar corrosion inhibitors often act negative on emulsification behavior and on corrosion protection effect from and this complicates the product formulation. This problem could be solved eliminate if oil-soluble anti-corrosion agents with emulsifying Properties could be made available.

From US-A-2,978,415 are guanidinium salts of unsaturated fatty acids as well Processes for their preparation are known. These guanidine soaps of unsaturated fatty acids are used for cleaning textiles with solvents, so-called "Dry cleaning" or "dry cleaning", as cleaning-enhancing Active ingredients used. For this application, which happens in a purely organic phase, is neither a corrosion protection effect nor an emulsifying ability important. Accordingly, this US document contains no information on a corresponding effect the guanidine soaps of unsaturated fatty acids.

Chemical Abstracts, Vol. 115 (1991), No. 12, Unit 115: 118 225y Investigations on the corrosion protection effect of guanidine salts on iron and Non-ferrous metals in water containing chloride, hydrogen carbonate and sulfate ions contains. The caprylate, carbonate, caprate and laurate salts were examined.

GB-A-602 617 relates to oil-in-water emulsions which use a guanidine salt as an emulsifier contain a saturated monocarboxylic acid with at least 10 carbon atoms. Such Emulsions are used, for example, as lubricants. Preferably These emulsions contain a combination of a guanidine salt as an emulsifier a saturated fatty acid with at least 10 carbon atoms and an alkylolamine salt a carboxylic acid with at least 10 carbon atoms and also free alkylolamine. It it is mentioned that guanidine salts of unsaturated fatty acids, for example oleates, are unsuitable because of the instability of the resulting emulsions.

The object of the present invention is to create new sulfur and to provide alkylamine-free anti-corrosion agents whose Oil solutions are not unacceptably high even at high concentrations of active ingredients Have viscosities, and at the same time an emulsification of the oil phase effect when mixed with water, without additional Emulsifiers are required.

This object is achieved by using guanidinium salts polyunsaturated fatty acids with 6 to 44 carbon atoms Achieve temporary corrosion protection on metallic, preferably iron-based surfaces.

“Fatty acids” are understood here to mean carboxylic acids which, if appropriate May be substituted by OH. The unsaturated fatty acids that can be used can be divided into two groups: native fatty acids, like them occur as a component of natural oils and fats and so-called dimer fatty acids, the technically through, usually acid catalyzed, dimerization suitable fatty acids are accessible. The unsaturated ones that can be used Fatty acids are therefore once characterized in that they are native Represent fatty acids, that is branched or preferably linear, one have up to six, preferably one to three double bonds and preferably Contain 11 to 28, in particular 18 to 22 carbon atoms. Suitable unsaturated fatty acids of this type are preferably monobasic and selected from undecylenic acid, myristoleic acid, palmitoleic acid, Oleic acid, ricinoleic acid, erucic acid, linoleic acid, linolenic acid, Arachidonic acid and mixtures thereof. On the other hand, there are unsaturated fatty acids suitable from the group of the so-called dimer acids. These are polybasic, preferably dibasic. Such are in particular dimer acids suitable, which have 36 to 44 carbon atoms.

For the purpose of the invention, guanidinium salts can be more defined, purer Fatty acids can be used with advantage. Because of economical reasons in practice, however, one becomes guanidinium salts of technical fatty acid mixtures use that in addition to unsaturated fatty acids different C chain lengths also contain certain proportions of saturated fatty acids can. Such technical fatty acid mixtures can, for example can be obtained by splitting suitable natural oils and fats. In terms of the use according to the invention, however, it is necessary that the technical fatty acid mixtures at least 50 wt .-%, preferably at least 80% by weight of unsaturated fatty acids of the above Carbon chain lengths exist.

The so-called dimer fatty acids, which can likewise be used according to the invention, generally do not represent pure substances either, but can contain fatty acids of different carbon chain lengths and / or different degrees of oligomerization. In addition to the actual dimer fatty acids, for example, trimerization or polymerization products can also be present in addition to unreacted and / or isomerized monomer fatty acids. When we are talking about dimer fatty acids, we mean product mixtures that consist of at least 50% by weight, preferably at least 70% by weight, of dimer fatty acid with a C chain length between 36 and 44. Such products are commercially available, for example from Unichema under the product group name Pripol ^R or from Henkel KGaA under the product group name Empol ^R.

For the use according to the invention of guanidinium salts of the abovementioned fatty acids, they are used as solutions in hydrocarbons which are liquid at working temperature, dialkyl ethers and / or acetals which are largely insoluble in water, and mixtures thereof. Also suitable as oil phase for dissolving the guanidinium salts of unsaturated fatty acids are ester oils such as oleyl oleate, esterification products of aliphatic dicarboxylic acids (preferably C _8-9 ) with branched Guerbet alcohols (preferably C _12-20 ) (EP-A-489 809), esters of C _{1- 5-} nonocarboxylic acids with mono- or polyfunctional alcohols (described for example in DE-A-39 07 391), esters of C _6-11 -nonocarboxylic acids with mono- or polyfunctional alcohols (described for example in DE-A-39 07 392), and Alkoxylation products of triglycerides with 0.5 - 3 mol EO and / or PO, for example glycerol propoxylate trioleate (German patent application DE-A-43 23 771). Also suitable are liquid, largely water-insoluble saturated or unsaturated fatty alcohols having 6 to 36 carbon atoms at working temperature, both simple alcohols and alpha, omega-diols being suitable.

These essentially water-insoluble solvents are described below referred to as "oil-like solvents".

Solutions which contain between 1 and 45% by weight are preferably used. contain dissolved in guanidinium salts of unsaturated fatty acids. With less The corrosion protection effect decreases significantly, while at higher levels, the solutions are usually so highly viscous that their Handling and their use for emulsion formation is unnecessarily difficult.

However, higher concentrations can also be used for the purposes of the invention, considering the difficulties associated with emulsion formation tolerates, for example, prior heating of concentrate and preparation water and the use of technical emulsifying aids such as fast running tooth lock washers or ultrasound.

As an oil-like solvent for the guanidinium salts of unsaturated fatty acids for example, hydrocarbons come into consideration at working temperature, So a temperature between about 10 and about 90 ° C liquid are. Examples of this are paraffin oil or mineral oil, where in the case of Mineral oil for ecological and toxicological reasons low-aromatic mineral oils are preferred. Suitable oils of this type are commercially available. Examples include pioneer oil 4556 from Hansen & Rosenthal, Enerpar 3036 from Deutsche BP and Parex Paraffin II from Leuna-Werke.

Furthermore come as unsaturated oil-like solvents for the guanidinium salts Fatty acids in the above Liquid working temperatures, largely water-insoluble dialkyl ethers. Under "largely insoluble in water" are dialkyl ethers to be understood that are in water dissolve no more than 5% by weight, preferably not more than 0.5% by weight. Suitable examples are dialkyl ethers with 6 to 24, preferably 8 to 18 C atoms per alkyl radical, the alkyl radicals being straight-chain independently of one another or can be branched, saturated or unsaturated and preferably n-octyl, 2-ethylhexyl, stearyl and / or isostearyl radicals represent. The dialkyl ethers can still have free hydroxyl groups and are then referred to as hydroxy mixed ethers. The use of such Dialkyl ether in metalworking fluids is for example in German patent application DE-A-42 37 501. Such dialkyl ethers are commercially available, for example from Henkel KGaA at Name Cetiol-OE (dioctyl ether).

As an oil-like solvent for the use according to the invention of the guanidinium salts come acetals based on monovalent aldehydes with 1 to 25, preferably 1 to 10 carbon atoms, and monohydric alcohols with 1 to 25, in particular 2 to 20 carbon atoms. The usage such acetals as a mineral oil substitute, oil component or base oil in lubricating oils and in metalworking fluids is known from EP-A-512 501. There is also a general rule for making such Acetale communicated.

The use according to the invention of the guanidinium salts of unsaturated fatty acids happens preferably in such a way that the solution of the guanidinium salts in one of the above-mentioned oil-like solvents or in Mixtures of these are used as the oil phase of an oil-in-water emulsion becomes. The proportion of the oil phase is, including the solution of Guanidinium salts of the unsaturated fatty acids is understood at the Emulsion preferably between 0.5 and 50% by weight, in particular between 5 and 20% by weight. The rule of thumb is that the proportion of the oil phase the lower the concentration, the higher the concentration of the guanidinium salts unsaturated fatty acids in the oil phase. Good corrosion protection results are achieved, for example, by using an oil-in-water emulsion with an oil phase content of 10% by weight, the Oil phase a concentration of a guanidinium salt of an unsaturated Fatty acid, for example guanidinium oleate, has between 5 and 20% by weight.

Accordingly, the invention encompasses the use of guanidinium salts polyunsaturated fatty acids with 6 to 44 carbon atoms according to one or more of claims 1 to 9, wherein the guanidinium salts are more unsaturated Fatty acids are dissolved in an oil-in-water emulsion and being an oil phase oily solvent or solvent mixture according to one or more of the Claims 6 to 9 is used and the proportion of the oil phase in the Emulsion between 0.5 and 50, preferably 5 to 20 wt .-% and the proportion of Guanidinium salts 1 to 45, preferably 5 to 20 wt .-% based on the oil phase is.

The viscosity of the solutions of the guanidinium salts can be increased by adding glycols unsaturated fatty acids in the oil-like solvents on application technology favorable values can be set without the ability to form emulsions Water is affected by this. Examples of glycols are butyl diglycol, Hexylene glycol or dipropylene glycol suitable in the guanidinium salt solution Amounts from 1 to 10% by weight can be added. The glycols can either be the solution of the guanidinium salts Unsaturated fatty acids added in oil-like solvents or the oily solvent before the reaction described below of guanidinium salts of volatile acids with unsaturated fatty acids be added. Because of the favorable effect on corrosion protection the use of hexylene glycol is preferred.

In the preparation of emulsions, the procedure is preferably such that a solution of the guanidinium salts in the oil-like solvent Mixed water. Since the guanidinium salts in both the oil-like solvents are soluble in water, they will be between water and distribute oil phase. The distribution balance depends on the individual case the chosen oily solvent and the type of unsaturated Fatty acid. As described in Example 11, an emulsion can also do this are obtained by having an aqueous solution of the guanidinium salts emulsified with oil. Here too it is to be expected that there will be a distribution equilibrium which sets guanidinium salts.

The proportion of the oil phase, which contains the guanidinium salts of unsaturated fatty acids at least partially dissolved, in the oil-in-water emulsion is from about 0.5 to about 50% by weight and is preferably in the range from about 5 to about 20% by weight. %. Such an emulsion is usually stable for the periods of several hours required in terms of application technology without further co-emulsifiers. In special circumstances, for example if the emulsion contains further active ingredients such as builder salts or use-related impurities, it may be necessary to stabilize the emulsion by using additional co-emulsifiers. Nonionic surfactants, in particular ethoxylation products of fatty alcohols, such as, for example, an adduct of 6 moles of ethylene oxide with 1 mole of a C _12/14 fatty alcohol mixture, or anionic emulsifiers such as, for example, alkylbenzenesulfonates, are suitable for this. The amounts required depend on the other emulsion components and must be determined by experiment. As a guideline, the use of up to 20% by weight of co-emulsifier based on the proportion of the oil solution can be taken.

The emulsion can be in the form of a conventional, milky opaque Emulsion present. It can also be advantageous for special purposes be the emulsion in the form of an almost transparent so-called microemulsion with an oil content of up to 50% by weight, as is caused by phase inversion is available from a water-in-oil emulsion. A such phase inversion, for example by varying the temperature can also be done as a PIT (= "phase inversion temperature") method designated. It is closer in the German patent application DE-A-43 23 908 described. One possible implementation is in Example 11 below specified.

Accordingly, the invention relates to oil-in-water emulsions that are considered by Phase inversion microemulsions are available, the oil phase of which oily solvent or solvent mixture selected from at Working temperature liquid hydrocarbons, largely water-insoluble Dialkyl ethers, alcohols, ester oils and / or acetals and mixtures thereof, represents and guanidinium salts of mono- or polyunsaturated fatty acids with 6 to 44 carbon atoms in concentrations of 1 to 45% by weight, preferably 5 to 20 Wt .-%, dissolved in relation to the oil phase and the proportion of Oil phase on the emulsion between 0.5 and 50 wt .-%, preferably 5 to 20 % By weight.

The preparation of the guanidinium salts of unsaturated fatty acids is described in the above-mentioned US Pat. No. 2,978,415. For example, a mixture of unsaturated fatty acids can be dissolved in an organic solvent such as methyl isobutyl ketone and guanidinium carbonate can be added. After completion of the reaction, which proceeds with elimination of water and CO ₂ , the solvent and the water of reaction can be removed, the product remaining in the form of a brown, waxy paste. For the use according to the invention, it is advisable to use directly oil-like solvents as the solvent for the reaction of the unsaturated fatty acids with guanidinium salts of volatile acids, for example guanidinium carbonate, as the oil phase to be used for later emulsion preparation. A manufacturing example is described below.

Depending on the oil-type solvent used, it may be advisable that resulting from the reaction of guanidinium carbonate with the fatty acid Water of reaction more or less completely from the reaction product to be removed, since the viscosities of the solutions obtained strongly depend on the water content can depend. The optimal procedure during production (Heating, applying vacuum) depends on the one hand on the unsaturated used Fatty acid or from the fatty acid mixture and on the other hand from that used oily solvents and must be empirical for the specific case be determined.

It is advantageous when preparing the solutions of guanidinium salts unsaturated fatty acids in the oil-like solvent homogeneous liquids to get their viscosity allows them to be used without further technical To allow measures for emulsion formation to run into water. Highly viscous, paste-like systems are more difficult to handle and therefore less prefers. Guaninium salts of saturated fatty acids, which act as corrosion inhibitors are known are for the use according to the invention unsuitable because their oil solutions in the concentration ranges according to the invention are not mobile liquids, but wax-like pastes.

Examples

Examples 1 to 5 describe processes according to the invention for the preparation of solutions and emulsions used.

example 1

In accordance with US Pat. No. 2,978,415, the preparation of a guanidinium oleate solution in mineral oil is described which contains 38% by weight of the salt: 610.6 g of technical oleic acid with an acid number of 202 (Edenor ^R Ti05GA, Henkel.) Are heated in a heated stirrer with nitrogen transfer KGaA, Düsseldorf), corresponding to 2 mol + 10% excess, mixed with 1096 g mineral oil (pioneering oil 4556, Hansen & Rosenthal). 180 g (1 mol) of guanidinium carbonate (Linz Chemie, Linz (Austria)) are added in portions with stirring at room temperature and with a nitrogen blanket. After the addition has ended, the reaction mixture is heated to 100 ° C. and stirred until the acid number is less than 20 (about 2 hours). A slight gassing can be observed during the reaction time and the solution changes color from light yellow to beige brown. During the reaction, the elimination of 1 mol of carbonic acid corresponding to 1 mol of H ₂ O and 1 mol of CO ₂ , 62 g, is theoretically to be expected. A viscous, beige-brown, transparent oil solution is obtained as the reaction product.

Examples 2 to 4

The preparation according to Example 1 was carried out with variation of the solvent, otherwise repeated identically.

Example 2

Solvent: paraffinic process oil Enerpar 3036, Deutsche BP

Example 3

Paraffin oil Parex Paraffin II, Leuna-Werke

Example 4

Solvent: dioctyl ether Cetiol-0E, Henkel KGaA.

There were brown, transparent, viscous but mobile liquids receive.

Example 5

Based on US Pat. No. 2,978,415, the preparation of a guanidinium oleate solution in mineral oil is described which contains 10% by weight of the salt: 638 g of technical oleic acid 202 (Edenor ^R Ti05GA, Henkel KGaA, Düsseldorf), corresponding to 2 mol + 15% excess, mixed with 190 g mineral oil (Pionieröl 4556, Hansen & Rosenthal). 180 g (1 mol) of guanidinium carbonate (Linz Chemie, Linz (Austria)) are added in portions with stirring at room temperature and with a nitrogen blanket. After the addition has ended, the reaction mixture is heated to 100 ° C. and stirred until the acid number is less than 20 (about 2 hours). A slight gassing can be observed during the reaction time and the solution changes color from light yellow to beige brown. After the main reaction, water jet vacuum is applied (15 min) at 100 ° C to remove CO ₂ and water. The reaction mixture is diluted with 6620 g of mineral oil. A beige-brown, transparent oil solution is obtained as a reaction product, from which emulsions can be produced by adding 90% by weight of water.

Examples 6 to 10, Comparative Examples 1 to 3

The corrosion protection effect was checked after the condensation test according to DIN 50017 KFW. Steel sheets of quality ST 1405 were used for this with the dimensions 5 cm x 10 cm brushed with an aqueous surfactant solution, rinsed with water and alcohol and dried. After that, the Plates immersed in oil solutions according to Examples 1 to 5. As comparative examples 1 to 3 became 20% by weight solutions of Ba-Petronate 70 TBN (Witco company) used in oils according to the table.

The test cycle began after 24 hours of draining, with the test panels being checked daily for corrosion. The results are summarized in the table. "Traces of corrosion" mean: a maximum of 3 corrosion points on the surface, "slight corrosion": less than 20% of the surface corrodes, "severe corrosion": over 20% of the surface corrodes. Corrosion protection test: condensation water test according to DIN 50017 KFW Test substance Results Ex. 6 Product from Ex. 1 up to 13 days no corrosion up to 24 days traces of corrosion after 25 days demolition with slight corrosion Ex. 7 Product from Ex. 2 after 25 days of demolition without corrosion Ex. 8 Product from Ex. 3 up to 16 days no corrosion after 25 days termination with traces of corrosion Ex. 9 Product from Ex. 4 up to 15 days no corrosion after 25 days termination with traces of corrosion Ex. 10 Product from Ex. 5 up to 7 days no corrosion after 20 days of severe corrosion Cf. 1 Barium petroleum sulfonate in pioneering oil 4556 severe corrosion after 1 day (> 20% corroded) Cf. 2nd Barium petroleum sulfonate in Enerpar 3036 up to 2 days no corrosion up to 3 days traces of corrosion after 5 days termination with severe corrosion Cf. 3rd Barium petroleum sulfonate in Parex Paraffin II up to 1 day traces of corrosion after 5 days termination with severe corrosion

Corrosion protection effect of emulsions

The corrosion protection effect of an emulsion was analogous to Example 10 tested by adding the product from Example 5 with water in the Weight ratio 1: 9 was obtained: after 7 days there was no corrosion, severe corrosion observed after 20 days.

Viscosity regulation

The product from example was used for a corrosion test analogous to example 10 5 mixed with 5 wt .-% hexylene glycol. By adding water An emulsion was obtained in a weight ratio of 1: 9 and for testing the corrosion protection effect used. Result: After 8 days none, severe corrosion after 13 days.

Example 11: Production of a microemulsion by phase inversion.

In a first step, solvent-free guanidinium oleate was prepared by mixing 90 g (= 0.5 mol) guanidinium carbonate with 281 g (= 1 mol) technical oleic acid of acid number 202 (Edenor ^R Ti05, Henkel KGaA, Düsseldorf) in a stirring apparatus at room temperature . With stirring, the temperature was raised to 150 ° C. within 45 minutes and left at this value for 3.5 hours. A yellow-brown waxy product with an acid number of 5 was obtained.

To prepare a microemulsion by the phase inversion method, 2.6 parts by weight of this guanidinium oleate and 0.26 part by weight of sodium citrate were dissolved in 51.04 parts by weight of water. The solution was mixed with 40 parts by weight of mineral oil (pioneer oil 4556) and 6.1 parts by weight of emulsifier (adduct of 4 mol of ethylene oxide with a C _12/14 fatty alcohol mixture) at a temperature above the phase inversion temperature of 35 ° determined by preliminary tests C mixed by stirring and cooled below the phase inversion temperature. A transparent microemulsion was obtained which can be diluted by adding water.

Claims (11)

1. The use of guanidinium salts of mono- or polyunsaturated fatty acids containing 6 to 44 carbon atoms for obtaining temporary protection against corrosion on metal surfaces.
2. The use claimed in claim 1, characterized in that the mono- or polyunsaturated fatty acids are selected from native fatty acids and/or from dimer fatty acids.
3. The use claimed in claim 2, characterized in that the native fatty acids are branched or linear, have 1 to 6 double bonds and contain 11 to 28 carbon atoms.
4. The use claimed in claim 3, characterized in that the native fatty acids are monobasic and are selected from undecylenic acid, myristoleic acid, palmitoleic acid, oleic acid, ricinoleic acid, erucic acid, linoleic acid, linolenic acid, arachidonic acid and mixtures thereof.
5. The use claimed in claim 2, characterized in that the dimer fatty acids are polybasic and contain 36 to 44 carbon atoms.
6. The use claimed in one or more of claims 1 to 5, characterized in that the guanidinium salts are used as solutions in oil-like solvents selected from hydrocarbons liquid at the working temperature, substantially water-insoluble dialkyl ethers, alcohols, ester oils and/or acetals and mixtures thereof, in concentrations of 1 to 45% by weight.
7. The use claimed in claim 6, characterized in that dialkyl ethers containing 6 to 24 carbon atoms per alkyl group are used as solvents for the guanidinium salts, the alkyl groups independently of one another being linear or branched, saturated or unsaturated groups.
8. The use claimed in claim 6, characterized in that one or more acetals based on monofunctional aldehydes containing 1 to 25 carbon atoms and monohydric alcohols containing 1 to 25 carbon atoms are used as solvents for the guanidinium salts.
9. The use claimed in claim 6, characterized in that hydrocarbons in the form of paraffin oil or mineral oil are used as solvents for the guanidinium salts.
10. The use claimed in one or more of claims 1 to 9, characterized in that the guanidinium salts of unsaturated fatty acids are dissolved in an oil-in-water emulsion, an oil-like solvent or solvent mixture according to one or more of claims 6 to 9 being used as the oil phase and the oil phase making up from 0.5 to 50% by weight of the emulsion and the guanidinium salts making up from 1 to 45% by weight of the oil phase.
11. An oil-in-water emulsion in the form of a microemulsion obtainable by phase inversion, its oil phase being an oil-like solvent or solvent mixture selected from hydrocarbons liquid at room temperature, substantially water-insoluble dialkyl ethers, alcohols, ester oils and/or acetals and mixtures thereof and containing guanidinium salts of mono- or polyunsaturated fatty acids containing 6 to 44 carbon atoms in concentrations of 1 to 45% by weight, based on the oil phase, in dissolved form and the oil phase making up from 0.5 to 50% by weight of the emulsion.