DE960921C - Hydraulic fluid - Google Patents

Description

ISSUED MARCH 28, 1957

St 6653 IVc / 23 c

Hydraulic fluid

The invention relates to the composition of hydraulic fluids, in particular such with reduced flammability.

Hydraulic fluids are usually made from light, usually naphthenic, raw materials derived mineral lubricating oils and additives, e.g. B. substances to improve the Viscosity coefficient, prepared. The desired physical properties of such Liquids are very different for the individual uses. So one prefers z. B. mostly in the aircraft hydration, aulik a liquid with a very low freezing point its viscosity changes only relatively slightly when the temperature changes. On the other hand, require Power transmission fluids, e.g. B. for industrial extrusion machines, none of this low freezing point; they are only used within a small temperature range. in the however, in general, most uses require that the viscosity be increased changes only slightly when the temperature changes; usually the liquids have to be inside be resistant to a fairly wide temperature range. as

A disadvantage of conventional fluids used as transmission media is that they are more or less flammable. Through this

can cause very serious fire damage, especially if the Fine spray from high pressure pipe ignites. One object of the present invention are therefore hydraulic fluids whose properties are those of normal fluids based on mineral oil come close, but have only a very low flammability. The invention relates to the composition of hydraulic fluids based on Water or a mixture of water with mono- or polyhydric alcohols with a low An ionic surfactant content which, according to the specification, is a smaller amount of a contain non-ionic surfactants. That in the hydraulic. Liquids contained Water itself has the desirable property that it is non-flammable; However, it is Too thin for most purposes and only has inadequate smear properties. By using the various additives mentioned above and the inventive addition of non-ionic surfactants, it is thickened and improved in its permeability. The disadvantage that occurs with many substances of this type is the so-called »reverse Solubility «, d. H. the precipitation of a surfactant at higher operating temperatures from an aqueous solution which at room temperature is a homogeneous liquid of suitable Viscosity forms, is here by the presence of a small amount of anionactive or cation-active surface-active substances avoided. In many cases hydraulic fluids are used which have lower freezing points than the surfactant mixtures in water alone. In these cases, it is advantageous to start from a carrier composed of a mixture Water and a water-soluble mono- or polyhydric alcohol. Alkylene glycols and polyglycols are particularly preferred for this purpose

admitted; however, you can also use monohydric alcohols, e.g. B. isopropyl alcohol, or polyhydric alcohols such as glycerin, use. The amount of alcohol added depends on the freezing point required in the liquid. So z. B. a solution of 5 percent by weight ethylene glycol in water at about -ii °, a solution with 55 percent by weight glycol at -40 ⁰ or even lower. For industrial purposes, the amount of alcohol used is such that a freezing point of -10 to 0 °, preferably -7 to -1 °, is obtained; in the aircraft hydraulic, however, the freezing may preferably be -35 -40 to -50 ⁰ to -65 °. So you use z. B. ethylene glycol in amounts of about 1 to 15 percent by weight, preferably 2 to 10 percent by weight for industrial uses and 40 to 70 percent by weight, preferably 50 to 60 percent by weight for use in aircraft hydraulics. For most purposes, ethylene glycol is the preferred freezing point depressant.

Hydraulic fluids of a similar type have already been proposed in which ion-active Additives are included; however, the non-ionic surface-active substances are completely absent here Agents which, according to the present invention, are added to achieve sufficient lubricity are. Likewise, the simultaneous use of different mono- and polyvalent ones is already possible Alcohols and polyethylene oxide have been suggested for such liquids. The latter However, the additive is not a surface-active substance, but a waxy body that cools down when it cools down separates from the liquid like grease and therefore with the non-ionic surface-active Additives according to the present invention is not comparable, the solubility of which is incidentally in the Cold is many times higher than in warmth.

The following table shows the effect of using different amounts

Tabel

Influence of sulphonated castor oil, half of which is neutralized with potash, on the viscosity and Separation temperature of 15 percent by weight »Lissapol NX« in a mixture of ethylene glycol

and water in a ratio of 5:95 percent by weight

% Sulfonated Kinematic viscosity ² ) in cSt at 37.7 ° A. Segregation castor oil at 15.5 ° 10 (1.84) temperature ⁰ C ¹ ) 0 62 (8.16) 50 0.5 98.0 (12.90) 62 (8.16) - 36.0 81.5 1.0 70.0 (9.21) 48 (6.36) - 8.0 60 2.0 36.0 (4.82) 35 (4.69) + 12.0 ?! 3.0 29.5 (4.00) 27 (3.69) + 5.5 82 4, o 26.0 (3.57) • 21 (2.98) + 1.0 96 5.0 22.5 (3.16) 16 (2.43) - i, 5 > Boiling point 6.0 20.0 (2.87) 12 (2.02) - 4.0 - 7-0 I8, O (2.64) - 6.0. -

¹ J The demixing temperature is the temperature at which the mixture becomes cloudy as a result of the precipitation of the thickening additive.

² ) The numbers given in brackets after the kinematic viscosity values are the corresponding viscosity numbers in Engler degrees.

of a typical anionic surfactant to the demixing temperature of a Mixture of 15 percent by weight of a non-ionic additive in a mixture of water and glycol in a ratio of 95: 5. A 50% was used as an anion-active additive KOH neutralized sulfonated castor oil is used. The non-ionic surfactant was a surface-active one commercially available under the name "Lissapol NX" Agent which is a mixture of o- and p-octyl cresols condensed with 6 moles of ethylene oxide. the The data given in the table are rounded-off, corresponding graphical representations Values.

From this table you can see that, apart from the addition of the sulfonated Castor oil in the range of 0.5 to 1 percent by weight, the addition of the anionic surfactant to an increasingly stronger one Increasing the demixing temperature leads and that the liquid is within the entire concentration range of the anion-active agent has a higher demixing temperature than in its absence Has.

With an anionic surfactant content, a peculiar effect on the kinematic viscosity values is evident at the various concentrations. At 15.5 °, the kinematic viscosity falls rapidly with increasing addition of the cleaning agent, until a concentration of 2 percent by weight is reached; from then on it falls more gradually. On the other hand, the viscosity at 37.7 ° rises rapidly with increasing concentration until a concentration of about 1.7 percent by weight is reached, and thereafter it also falls. The result of these peculiar changes in viscosity with increasing concentration is a range of contents of anionic surface-active additives, within which the viscosity of the liquid increases with increasing temperature. These strange relationships are shown most clearly when looking at the next column of the above table, in which the difference Δ between the kinematic viscosity values is shown between 15.5 and 37.7 °. It is noticeable that these values are first negative, then positive and finally negative again. A curve showing these values would reach the value ο at two points, namely with a content of sulfonated castor oil which is 1.4 percent by weight the first time and 4.5 percent by weight the second time. These are those areas in which the change in viscosity between 15.5 and 37.7 ° is particularly low. The person skilled in the art can thus, if he mixes 15 percent by weight of a nonionic surfactant with 85 percent by weight of a water-glycol mixture in the ratio 95: 5, hydraulic fluids by adding 1.4 percent by weight and 4.5 percent by weight sulfonated castor oil another time obtained whose viscosity changes little or not at all with increasing temperature. Of course, the viscosities of these two liquids are different. If the person skilled in the art desires other viscosities, which should not change much with increasing temperature, then he has to start from other basic mixtures of water, alcohol and non-ionic additives, which approximate the viscosity range sought and then carry out experiments in the same way with this starting mixture required addition of sulfonated castor oil or another similar agent to vary at different temperatures until he can determine from these values with which percentages of the sulfonated oil the viscosity is least influenced by the temperature.

An example of the effectiveness of a cationic surfactant content on the Increase in the separation temperatures of aqueous solutions, which are also non-ionic surface-active Containing substances is the influence of cetyltrimethylammonium bromide. -i ° / o of this remedy increases the separation temperature of a mixture of 15 weight percent polyethylene glycol monooleate and 85 percent by weight water from 38 to 55 °.

The non-ionic surface-active substances which, according to the invention, are used to improve lubricity go ability of water or mixtures of glycol and water to be used Compounds that contain both hydrophobic and hydrophilic groups that are directly or are connected to one another via an intermediate group in an overall configuration such that there is essentially no change in either of the two groups.

The hydrophobic group can essentially be an aliphatic, saturated or unsaturated radical straight chain, preferably containing 10 to 20 carbon atoms, e.g. B. the saturated Cetyl, lauryl, myristyl, stearyl and arachyl groups or those of the dodecylene, Unsaturated groups derived from palmitoleic, oleic, castor oil, linseed oil, linolenic and arachidic acid. These aliphatic chains can also contain non-polar substitution groups, e.g. B. aromatic, naphthenic or heterocyclic rings, or polar groups, e.g. B. hydroxyl, carbonyl, carboxyl groups contain. If the substituent is hydrophilic, care must be taken that the Overall action of the aliphatic and substituting groups is hydrophobic. The hydrophobic group can also consist of an aromatic, naphthenic or heterocyclic radical, the substituents may contain non-polar nature, e.g. alkyl, naphthene or heterocyclic groups, or polar groups such as hydroxyl, carbonyl, carboxyl groups and ether, ester and amide bonds.

The hydrophilic group can be the remainder of a low molecular weight acid of esters, ethers, Be ketones. Preferably it should be from a low molecular weight aliphatic alcohol or a polyhydric alcohol originate, e.g. B. the alkylene

glycols or glycerine, or of polymeric alcohols such as polyethylene glycols.

The hydrophobic and hydrophilic groups can be used directly or through intermediate groups, e.g. B. amide, alkyl-substituted amide, ester, ether, sulfonamide groups, —SO ₂ - and —S—, may be linked to one another.

To the class of anionic surfactants used in mixtures in conjunction with the

ίο Above-mentioned non-ionic surface-active substances may be included, include hydrophobically substituted carboxylic acids, sulfuric acid esters (sulfates), alkane sulfuric acids, alkyl aromatic sulfuric acids, phosphates and phosphoric acids, persulfates and thiosulfates, sulfonamides and sulfamic acids. The hydrophobic group, usually a long chain fatty acid residue, can be linked to the above functional groups directly or through intermediate groups, principally amide, ester, sulfonamide ether groups, —SO ₂ - and —S—. The hydrophobic group may have no polar substituents or it may contain substituents such as chlorine, oxy and acetoxy groups or olefin sulfuric acid. The compounds are preferably used as alkali metal salts.

Preferred anionic surface-active agents are the water-soluble alkali metal salts, preferably sodium or potassium salts, of the sulfonated vegetable oils such as turkey red oil, or sulfonated alkyl aromatic substances, e.g. B. the sodium salt of sulfonated C ₁₂ polypropylbenzene or toluene.

The cationic surface-active substances, which can be contained together with or instead of the anion-active agents, break down into four main groups: a) primary, secondary and tertiary amine salts, b) quaternary ammonium compounds, c) other nitrogenous bases and d) nitrogen-free bases. The amines of group a) can be aliphatic, aromatic or heterocyclic. In c) the bases can also not be quaternary, e.g. B. guanidine and thiuronium compounds. The nitrogen-free bases of group d) are mainly phosphonium and sulphonium compounds. The hydrophobic groups may be connected with the above-mentioned groups, directly or through groups such as ester, amine or ether groups _7.

Particularly preferred cationic surfactants are the quaternary amine halides which are N-substituted by long chain alkyl groups, e.g. B. Mono-C ₁₀ - to -C ₂₀ -alkyltri-C _JL -bis -Cg-alkylammonium halides, preferably cetyltrimethylammonium bromide and C ₁₀ - to C ₂₀ -alkylpyridinum halides, preferably cetylpyridinium bromide.

The choice and concentration of the nonionic surfactant depends on the viscosity and other properties required in the finished mixture / in general becomes the viscosity of a mixture of a non-ionic surfactant in water or a water-glycol mixture due to the presence of the anionic or cationic Surfactant reduced, in such a way that when performing the present Invention of the former surfactant is required considerably more to achieve a given viscosity. Usually less than 30 weight percent will be in the mixture of the nonionic surfactant used; for some uses however, more may be desirable.

The hydraulic fluids should be composed so that at 38 ^{0 they have} a kinematic viscosity between 5 and 60 cSt (corresponding to 1.4 to 17.1 ° Engler), preferably between 10 and 40 cSt (2.8 to 11.4 ° Engler ), even better between 10 and 30 cSt (2.8 to 8.5 ° Engler), 8a z. B. 20 cSt (5.7 °. Angel), and the surfactant should be mixed in such an amount that these viscosity values are achieved. On the other hand, it is desirable that the amount of the surfactant be as small as possible in order that the liquid remains practically non-flammable and yet has sufficient lubricity. For these reasons the proportion of the non-ionic surfactant should be between 5 and 45 percent by weight, preferably 10 and 30 percent by weight, e.g. B. 15 or 20 percent by weight.

According to the present invention, the can serve as a solubilizer for elevated temperatures ionic surfactant can be either an anion active or a cation active agent. An anion active agent of this kind is preferable; its concentration should vary according to the ratio and the nature of the other ingredients, less than 25 percent by weight, preferably between 0.5 and 10 percent by weight, more advantageously between 1 and 7 percent by weight, e.g. B. 2 or 5 percent by weight.

The preferred non-ionic surfactant is a C ₄ - to C ₁₀ -alkylated or dialkylated phenol ester or ether which is attached to a polyhydric alcohol or a polymeric glycol, such as. B. polyethylene glycol, is bound. In particular, an octylated cresol which is bound to monoethylene glycol by an ether chain is preferred. Other particularly suitable non-ionic surface-active substances are diethylene glycol monooleate, glyceryl monooleate, polyoxyalkylene derivatives of the fatty acid esters of polyhydric alcohols, esterified polyoxyalkylene derivatives of urea, condensation products of alkylphenols and ethylene oxide.

The hydraulic fluids according to the invention can also contain other components, e.g. B. soluble substances to reduce wear and tear, as well as anti-corrosion agents. So z. B. C ₁ - to C ₄ trialkyl phosphates, especially tributyl phosphate, to reduce wear, and inorganic or organic nitrites, z. B. sodium nitrite, di-isopropylamine nitrite, dicyclohexylamine nitrite, to prevent

Corrosion can be added. As other anti-corrosive substances that can be added, are to be mentioned the alkali metal salts of organic acids, z. B. benzoic acid or cinnamic acid, and Mercaptobenthiazole. Antifoam agents, e.g. B. the silicones can also be used will.

Below is an example of a hydraulic fluid with approximate specifications of the ίο viscosity properties, and a comparison of this liquid with those in which some of the non-ionic surface-active ingredients to be used according to the invention are not included.

example

The hydraulic fluid was composed as follows:

»Lissapol NX« (condensation product from one
Mixture of o- and p-octyl cresols with 6 mol
Ethylene oxide) n, o percent by weight

Ethylene glycol 4.1 percent by weight

Water 78.0 -

Sulphonated castor oil, too
50% neutralized with KoH 4.9

Sodium dioctyl - sulfosucci-

nat (to improve the lubricating properties
high load) 0.99

Sodium nitrite 0.99

Silicone (anti-foam additive) 0.02 - '/ 5

This liquid has an acid number (mg Ko H / g) of 0.53 and the saponification number 1.5; the sulfur content was 0.08 percent by weight, the ash content after smoking with sulfuric acid was 1.67 percent by weight. The liquid was non-flammable, had a pour point of -10 ■ and a specific gravity at 15 ⁰ of 1,029. It was colored light yellow and showed the demixing temperatures and kinematic viscosity values (cSt) at 60, 37.7 and 15.6 ° given in the table below:

Kinematic Mix according to Like I, without Like i
»LissapolNX« through Like I, without sulf. Like I, sulf. Castor Viscosity cSt at example "Lissapol NX" • H ₂ O + glycol
replaced castor oil H ₂ O + glycol I. II III IV V 6o, o ° - 13.5 r.f 29.1 0.96 0.69 about 26.0 about 20.0 15.6 ° 35.8 I, 8l i, 74 166.7 121.1 Segregation temp. 8o, 6 ° <0 ° <o ° · 31.8 ° 30.5 ° Bern. unstable at 37 °

According to this it can be seen that if the Lissapol or the castor oil are omitted, the mixture is mixed very easily separated and the Lissapol has a decisive influence on the viscosity properties Has.

Claims (9)

PATENT CLAIMS: 1. Hydraulic fluid consisting of water or a mixture of water with a 'monohydric or polyhydric alcohol and a small amount of an anionic or cationic surface-active substance, characterized in that the same also still contains a non-ionic surfactant. 2. Hydraulic fluid according to claim 1, characterized in that the non-ionic surfactant a polyoxyalkylene oxide derivative is an alkylated phenol. 3. Hydraulic fluid according to claim 1 and 2, characterized in that the same is the non-ionic surfactant in amounts of 5 and 45 percent by weight, preferably 10 and 30 percent by weight based on the total weight of the hydraulic fluid. 4. Hydraulic fluid according to claim 1 to 3, characterized in that the same is the anionic surfactant in amounts of 0.5 and 10 percent by weight, preferably between 1 and 7 percent by weight, based on the total weight of the hydraulic fluid, contains. 5. Hydraulic fluid according to claim 1 to 4, characterized in that the anionic surfactant is an alkali metal salt. 6. Hydraulic fluid according to claim 5, characterized in that the anionically surface-active Substance an alkali metal salt of an organic sulfonic acid or a sulfonated one fatty substance. · 7. Hydraulic fluid according to claim 1 to 6, characterized in that the anionic surfactant is Turkish red oil. 8. Hydraulic fluid according to claim 1 to 3, characterized in that the cationic surfactant is a quaternary Ammonium compound, especially an alkyl halide of an N-substituted amine. 9. Hydraulic fluid according to claim 1 to 8, characterized in that it also contains a corrosion inhibitor, a foam inhibitor, or a soluble, wear-reducing agent? Agents, in particular a C ₁ - to C ₄ -alkyl ester of phosphoric acid, ζ. Β. Tributyl phosphate. Documents considered: Swiss Patent No. 147 216; British Patent No. 588,381; German patent specification No. 513 482. © 509 627/157 12.55 (609 845 3.57)