WO2009065785A2

WO2009065785A2 - Lubricant

Info

Publication number: WO2009065785A2
Application number: PCT/EP2008/065608
Authority: WO
Inventors: Rudolf Eidenschink; Holger Kretzschmann
Original assignee: Nematel Gmbh & Co. Kg
Priority date: 2007-11-21
Filing date: 2008-11-14
Publication date: 2009-05-28
Also published as: DE102007055554A1; WO2009065785A3; DE102007055554B4; US20110086784A1

Abstract

The invention relates to a lubricant containing one or more compounds selected from among the keto compounds of general formula (I) and/or metal compounds produced from said compounds, wherein R1, R2, and X have the indicated meaning.

Description

lubricant

The invention relates to a lubricant containing 20 to 99.9 percent by weight of one or more compounds of general formula I.

in which

X is H, F, Cl, -CH ₃ , -C ₂ H ₅ , -OCH ₃ ,

Ri are each, independently of one another, H, an alkyl radical having a total of 1 to 18 C atoms, in which also one or two non-adjacent CH ₂ groups are substituted by -O-, -S- or -CO- and two adjacent CH ₂ groups - COO or OOC can be replaced,

Each R ₂ is independently an alkyl radical having a total of 1 to 18 carbon atoms, in which also one or two non-adjacent CH ₂ groups by -O-, -S- and two non-adjacent CH ₂ groups by -COO- or - OOC- may be replaced, or the rest

with the meanings given above for X and Ri and in which n is a number between zero and 12 and q is zero or 1,

mean and / or produced from these compounds metal compounds and thus lubricated machine bearings. Lubricants containing mesogenic compounds have been known for some time (EP 0 330 068). It is assumed that a mesophase, ie a nematic, smectic or discotic liquid crystalline phase, can be induced in them by increasing the pressure or by shearing in machine bearings. Such phases, which are formed by compounds with elongated rod-shaped or discus-shaped molecules, are generally known (H. Kelker, R. Hatz, Handbook of Liquid Crystals, Verlag Chemie, Weinheim 1980). Through such phase transitions contacts between the mutually moving solids can be avoided, especially in the lubrication gap of sliding bearings. Compared to conventional lubricants can be achieved with them a huge reduction in friction losses. Thus, under conditions where friction coefficients of 0.2 to 0.1 (typical for mixed friction) are found with conventional lubricants, friction coefficients of <0.005 were measured, which are typical for plain bearings rated in the hydrodynamic range (R. Eidenschink , Mol. Cryst. Liq. Cryst. 461, 71-81 (2007) and literature cited therein).

The previously known lubricants containing substances with liquid-crystalline properties must be prepared consuming and with high losses of materials used. So far they could only be used for the lubrication of very problematic bearings.

Object of the present invention was to find a lubricant that can be economically produced from inexpensive raw materials and yet allows compared to conventional lubricants particularly low friction coefficients, especially in plain bearings. Although the compounds of the formula I have been detected by a Markus formula of an older invention (DE 38 10 626), but can because of the low ratio of length and diameter of their molecules for the expert suspect no liquid crystalline properties, has never been in such compounds observed a liquid crystalline phase.

Due to the lubricant according to the invention, it is surprisingly possible to achieve particularly low friction coefficients in machine bearings. Despite the unfavorable geometry of the molecules of the compounds of the formula I and of the metal compounds prepared from them, an abrupt phase transition, which is induced by shear effects in the lubricating gap of a bearing, could be responsible for this surprising effect. There may also be an unknown cause for this. - -

The compounds of the general formula I can advantageously be prepared by a single synthesis step from inexpensive compounds. For this purpose, an acetophenone, which is dissolved in a carboxylic acid ester, are condensed under the action of sodium (cf., DE 29 18 775, Synthesis Scheme 1).

Synthetic Scheme 1 Exemplary reaction of 4-ethyl-acetophenone with heptanoic acid ethyl ester

With the same reaction procedure, starting from an acetophenone and a dicarboxylic acid ester, compounds of the formula I are likewise obtained (synthesis scheme 2).

Synthetic Scheme 2 Exemplary reaction of diethyl sebacate with 4-butoxy-acetophenone

The β-benzoylcarboxylic acid esters likewise encompassed by the invention can be prepared in the same way (cf., K. Matsuki et al., Chem. Pharm. Bull 41, 643 (1993), synthesis scheme 3).

Synthesis Scheme 3 - -

Exemplary reaction of 4-methyl-acetophenone with dioctyl carbonate

Ri in the general formula I is preferably an alkyl or an alkoxy group having 1 to 7 carbon atoms. Preferably, these are unbranched.

R ₂ in the general formula I preferably denotes an alkyl or alkoxy group having 1 to 12 C atoms, the chains preferably being unbranched.

X in the general formula I is preferably H or -CH ₃ , of which H is particularly preferred.

The compounds of general formula I comprise the following preferred partial formulas Ia, Ib and Ic, wherein in the formulas Ib and Ic the meanings of X and Ri are each independent of one another.

Of these, compounds of formula Ia and Ic are preferred.

The lubricant according to the invention may contain, apart from compounds of the formula I and / or metal compounds prepared from these compounds, up to 80% of one or more additives. Such additives may include known lubricating oils, such as those derived from petroleum. - -

mineral oils or synthetic oils (see Ullmann's Encyclopedia of Industrial Chemistry, 5th Ed., Vol. A15, p. 423ff) and the additives known in tribology, such as wear protection agents, antioxidants or antifreeze agents.

Additives are also within the invention, those known to cause a fat-like consistency, such as metal soaps or polymers. The latter may act as gelling agents or as finely divided particles, e.g. PTFE (perfluoroethylene) may be present. The lubricants according to the invention therefore also include lubricating greases as well as lubricating greases.

It is generally known that aryl-substituted 1,3-diketones are predominantly in the tautomeric keto-enol form I according to the scheme

available. Within the present invention, all tautomeric forms present in equilibrium are attributed to the keto compounds of general formula I. In the databases, such compounds are referred to in a simplified manner as 1, 3-diketones, as in Example 1 below. From a keto-enol form are known to derive metal compounds (metal complexes) from. These compounds are encompassed by the present invention. Their general formula can be represented as follows: - -

where M ^{m is} an m-valent metal atom and m is a number between 1 and 4.

Thus, for the zinc complex, which can be prepared from the keto compound from Synthetic Scheme 1, the structural formula

be specified.

Preferred metal compounds are those of lithium, magnesium, titanium, zirconium, chromium, molybdenum, manganese, iron, nickel, copper, zinc and tin, of which those of lithium, magnesium and zinc are particularly preferred. These compounds are preferably prepared by heating the acetate, the acetylacetonate complex or an alkoxide of the metal in question with one or more compounds of the formula I and evaporating the acetic acid or the acetylacetone or the alcohol released in the process. These metal compounds, prepared from compounds of the general formula I, can be in solid form, but also in the form of solids, if the lubricant according to the invention is a lubricating grease. If more than one compound of the formula I are present, metal compounds with different ligands can be present. Within the present invention is considered to be proportion of these metal compounds one which is obtained when one out of the lubricant by distillation at 180 ⁰ C bottom temperature under suffi- low-pressure, the compounds of formula I and possibly also volatile additives removed. The residue consists of the most stable at the bottom temperature of the invention metal compounds and possibly other non-volatile additives. The possibly necessary distinction between the metal compounds from the compounds of formula I and other non-volatile additives is carried out according to generally known analytical methods. Likewise, any necessary distinction between compounds of formula I and other volatile additives in the distillate.

The compounds of the general formula I can be mixed by simple stirring at room temperature with other components customary in lubrication technology.

The lubricant according to the invention contains from 20 to 99.9, preferably from 50 to 99.9 and more preferably from 70 to 99.9% of compounds of the general formula I and / or metal compounds prepared from these compounds.

The lubricant according to the invention can advantageously be used in the generally known machine bearings, which are known to be divided into slide bearings or rolling bearings. Special advantages arise in the lubrication of plain bearings, namely those in machines of the textile industry, such as in the needle guides of sewing machines, but also for the lubrication of pistons hochtouriger combustion engines.

The following examples are intended to illustrate the invention without limiting it. Above and below, temperatures are given in degrees Celsius, percent means mass percent. Hz means the oscillation frequency in 1 / s. Within the invention, a coefficient of friction is considered to be particularly low if, in the test arrangement described in Example 1, a coefficient of friction of <0.05 can be achieved with the given parameters.

example 1

The prepared according to synthesis scheme 1 compound is 1- (4-ethylphenyl) -3-hexyl-propanedione-1, 3 has a melting point of -1 ⁰ C and is oberhab this temperature for an isotropic liquid having a kinematic viscosity of 1 1, 7 mm / s ² at 23 ⁰ C. Herein 0.2% of Antioxi- dans were dissolved 2,6-di-tert-butyl-p-cresol. - -

To demonstrate the availability of particularly favorable coefficients of friction in plain bearings, this lubricant was tested in a reversing sliding wear contact (tribometer SRV III, F. Optimol Instruments Prüftechnik GmbH, Munich). A drop of the lubricant was placed on a flat disc of 24 mm diameter and 7.9 mm thickness. Then a cylinder of 15 mm diameter and 22 mm length (both friction partners made of steel 100Cr6, according to the German industrial standard DIN 51834) at 90 ⁰ C under a load of 50 N at 50 Hz and a stroke of 1 mm at an angle of 10 ° parallel to the axis of rotation of the cylinder moves. After 6 hours of testing, the coefficient of friction had dropped from the initial 0.20 to below 0.005. This value was not exceeded until the termination of the measurement after 20 h. For comparison, commercially available lubricants have friction coefficients between 0.2 and 0.1 at the same parameters of the measurement.

Example 2

A lubricant (grease) made from

- -

30% PTFE powder, 5 μm (Dr. Tillwich GmbH, Horb) shows particularly low coefficients of friction in plain bearings.

Example 3 A lubricant consisting of

80% paraffin oil, dynamic viscosity at 20 ^° C 100 - 145 mPa-s, CAS 8012-95-1 shows in friction bearings particularly low friction coefficients.

Example 4

A lubricant consisting of - -

25% paraffin oil, dynamic viscosity at 20 ^° C 100 - 145 mPa-s, CAS 8012-95-1 shows very low coefficients of friction in plain bearings.

Example 5

96 parts by weight and

4 parts by weight Mg (OC ₂ Hs) ₂

are combined, heated with stirring in vacuo of 10 mbar at 120 ⁰ C for 2 h. The ethanol-free lubricant (a grease) has the composition

6 ^H 13 - -

particularly low coefficients of friction.

Claims

- P atentanspr che

1. lubricant containing 20 to 99.9 percent by mass of one or more compounds of general formula I.

in which

X is H, F, Cl, -CH ₃ , -C ₂ H ₅ , -OCH ₃ ,

Each R ₂ is independently an alkyl radical having a total of 1 to 18 carbon atoms, in which also one or two non-adjacent CH ₂ groups by -O-, -S- and two non-adjacent CH ₂ groups by -COO- or - OOC- can be replaced, replaced, or the rest

mean and / or produced from these compounds metal compounds.

2. A lubricant according to claim 1, characterized in that it contains 50 to 99.9 percent by mass of one or more compounds selected from the keto compounds of the general formula I and / or metal compounds prepared from these compounds.

3. A lubricant according to claim 1, characterized in that it contains 70 to 99.9 percent by mass of one or more compounds selected from the keto compounds of general formula I and / or metal compounds prepared from these compounds.

4. Use of a lubricant according to one of the preceding claims for reducing friction losses between mutually moving solids.

5. plain bearing, containing a lubricant from one of the preceding claims.