EP2687580B1 - Clock piece - Google Patents

Description

Technical area

The present invention relates to the field of mechanical watchmaking. It relates more particularly to a timepiece comprising at least two elements in contact and relatively movable relative to each other, at least one of said elements having a contact surface with the other element which is lubricated by means of a lubricating composition. The present invention also relates to such a lubricant composition, the use of chemical compounds as a lubricating agent and new chemical compounds.

State of the art

In a timepiece comprising at least two elements in contact and relatively movable relative to each other, it is necessary to lubricate the surfaces in contact with these elements to ensure as little friction as possible between these two elements.

For this, it is known to use lubricating oils comprising lubricants with a low coefficient of friction, less than or equal to 0.1. Such a lubricating agent is, for example, mixtures of polyalphaolefin type synthetic oils associated with a glycerol ester, namely glycerol monooleate (GMO).

In addition, the lubricating oils used in the timepieces must be altered as little as possible and retain their lubricant properties for a generally accepted period of at least 4 years.

To reduce friction, it is also known to associate elements having contact surfaces having affinity for hydrophilic groups to lubricating agents containing hydrophilic groups. Such contact surfaces comprise at least one oxide layer on the surface, and are for example made of alumina or zirconia, and more particularly of ruby or sapphire, materials traditionally used in the watch industry for bearings or pallets of 'anchor. Such a solution is proposed for example in the patent application EP 2,082,014 , the agent lubricant being a compound containing one or more hydrophilic groups chosen from C ₃ -C ₉ polyols having at least one third of OH groups relative to the number of carbon atoms. A preferred compound is glycerol. These compounds are agents with a very low coefficient of friction, the coefficients obtained being less than 0.06. However, these compounds have the disadvantage of deteriorating over time. In particular, they promote the development of microorganisms that will degrade the lubricant composition but also promote corrosion of the parts of the watch.

On the other hand, some oils used for the lubrication of timepieces are very fluid. Such oils have a natural tendency to migrate in case of deficient surface preparation. This migration would be catastrophic for the operation of the movement, so that these oils require the application of a layer of epilame, which complicates the steps of mounting a timepiece.

It is therefore necessary to propose new lubricating agents to guarantee the stability over time of the lubricant composition, but also to simplify the assembly steps of the timepiece, while having tribological properties equal to or better than those of known lubricating compositions.

Disclosure of the invention

For this purpose, and in accordance with the present invention, there is provided a timepiece according to the claims.

The present invention also relates to a lubricant composition according to the claims.

These glycerol ethers have the advantage of making it possible to obtain lubricant compositions that are stable over time, while guaranteeing tribological properties equal to or greater than those of known lubricating compositions.

Mode (s) of realization of the invention

The present invention relates to a timepiece comprising at least two elements in contact and relatively movable relative to each other, at least one of said elements having a contact surface which is lubricated by means of a lubricating composition.

et leurs mélanges.According to the invention, said lubricating composition comprises at least one glycerol ether chosen from the group comprising

and their mixtures.

The contact surface of at least one of the two elements in contact may be metal, metal alloy or plastic. So, the contact surface of at least one of the two elements in contact may be ferrous or cuprous alloy and have a surface coating electrochemically deposited, chemical, plasma or other.

If necessary, it is also possible to provide between the two elements in contact a surface tension modification layer (epilam layer) preventing the spreading of the lubricant composition. It is also possible to perform diffusion treatments.

Advantageously, the contact surface of at least one of the two lubricated elements by means of a lubricating composition may exhibit affinity with hydrophilic groups.

Preferably, the contact surface having an affinity with hydrophilic groups of at least one of the two elements is made of an oxide-based material. Such an oxide may be chosen from the group comprising, for example, aluminum oxide and zirconium oxide. Advantageously, the contact surface having an affinity with hydrophilic groups of at least one of the two elements is made of ruby or sapphire. The counterpart may be a ferrous alloy, cuprous or other, coated or uncoated, treated or not.

In an alternative embodiment, the contact surface of each of the two elements has an affinity with hydrophilic groups, as defined above.

Advantageously, one of the elements of the timepiece is an anchor pallet and the other element is an escape wheel. It is also possible to advantageously lubricate a mobile axis (for example a wheel element or a pendulum) pivoting in a clock stone.

ou l'éther de glycérol de formule :

Preferably, the glycerol ether of formula:

or the glycerol ether of formula:

The lubricating composition also comprises all the necessary additives traditionally used in lubricating compositions, and in particular in lubricating compositions used in the field of horology. In particular, the lubricating composition may comprise viscosity control agents, other complementary base oils, antioxidants, anti-wear and high-pressure additives and / or corrosion inhibitors.

The present invention also relates to the use as a lubricating agent in a lubricant composition for lubricating a contact surface of at least one element in contact with another element of a timepiece, said elements being relatively movable relative to one another. relative to the other, at least one glycerol ether as defined below, including their mixtures.

The present invention also relates to a chemical compound of formula:

The following examples illustrate the present invention without, however, limiting its scope.

I: Synthesis of glycerol ethers Synthesis of compound II

Introduce 0.5 mol of 2,2-dimethyl-4-hydoxymethyl-1,3-dioxolane, 500 ml of cyclohexane, 3 mol of caustic soda in 50% aqueous solution and 0.05 mol of tetrabutylammonium hydrogen sulfate in a ball. Heat at 30 ° C with stirring and add 0.5 mol of n-bromododecane in 15 minutes. Heat to 45 ° C and stir at this temperature for 48 hours. Add 400 mL of water, separate the aqueous phase, wash 3x with water. Dry the organic phase over magnesium sulfate, filter and evaporate the solvent. 140 g of crude product are obtained, purified by distillation, eb. 136 ° C to 0.05 mbar; 89.2 g (59%) of 2,2-dimethyl-4-dodecyloxymethyl-1,3-dioxolane are recovered.

Introduce 400 mL of water, 400 mL of ethanol and 4 g of concentrated sulfuric acid into a flask. Add 0.29 moles of 2,2-dimethyl-4-dodecyloxymethyl-1,3-dioxolane. Heat to reflux for 2.5 hours under agitation. Cool to 20 ° C., add 300 ml of saturated sodium chloride solution, extract 2x with 150 ml and then 2x with 50 ml of ether. Wash the combined organic phases 2x with water and then with saturated sodium chloride solution. Dry the organic phase over magnesium sulfate, filter and evaporate the solvent. 77 g of crude product are obtained, purified by distillation, eb. 135-137 ° C at 0.05 mbar; 59.1 g (78%) of 1-dodecyloxy-2,3-propanediol are recovered in the form of a waxy white crystalline solid melting at 44-46 ° C.

Synthesis of compound III

Introduce 0.25 mol of 2,2-dimethyl-4-hydoxymethyl-1,3-dioxolane, 250 ml of cyclohexane, 1.5 mol of caustic soda in 50% aqueous solution and 0.025 mol of tetrabutylammonium hydrogen sulfate in a ball. Heat at 30 ° C. with stirring and add 0.25 mol of bromoisotridecane in 15 minutes. Heat to 45 ° C and stir at this temperature for 48 hours. Add 200 mL of water, separate the aqueous phase, wash with water and then with saturated sodium chloride solution. Dry the organic phase over magnesium sulfate, filter and evaporate the solvent. 65 g of crude product are obtained, purified by distillation, eb. 156 ° C to 0.05 mbar; 52.7 g (67%) of 2,2-dimethyl-4-isotridecyloxymethyl-1,3-dioxolane are recovered.

Introduce 200 mL of water, 200 mL of ethanol and 2 g of concentrated sulfuric acid into a flask. Add 0.15 moles of 2,2-dimethyl-4-isotridecyloxymethyl-1,3-dioxolane. Heat at reflux for 2.5 hours with stirring. Cool to 20 ° C, add 150 ml of saturated sodium chloride solution, extract with 3x 100 ml of ether. Wash the combined organic phases 2x with water. Dry the organic phase over magnesium sulfate, filter and evaporate the solvent. 48 g of crude product are obtained, purified by distillation, eb. 165 ° C to 0.05 mbar; 33.6 g (82%) of 1-isotridecyloxy-2,3-propanediol are recovered in the form of a colorless viscous oil.

Synthesis of compound IV

Introduce 0.5 mol of 2-octyldodecanol, 500 ml of cyclohexane, 1.5 mol of caustic soda in 50% aqueous solution and 0.025 mol of trioctylmethylammonium chloride in a flask. Add 1.0 mol epichlorohydrin in 30 minutes with stirring. Stir at room temperature for 24 hours. Add 100 mL of water, separate the aqueous phase, wash the 3x organic phase with water. Dry the organic phase over magnesium sulfate, filter and evaporate the solvent. 222 g of crude product are obtained, purified by distillation, eb. 185-188 ° C at 0.05 mbar; 145.5 g (82%) of 2-octyldodecylglycidyl ether are recovered.

Introduce into a flask 4.2 mole of acetone and 0.02 mole of boron trifluoride etherate. 0.37 mol of 2-octyldodecylglycidyl ether are added with stirring in the course of 2 hours at ambient temperature. Continue agitation for 2.5 hours. Add 0.04 mol of sodium bicarbonate and evaporate the solvent. Wash with 200 mL of water, separate the aqueous phase. 150 g of crude 2,2-dimethyl-4- (2-octyldodecyloxymethyl) -1,3-dioxolane are obtained.

Introduce 300 mL of water, 300 mL of methanol and 5 g of concentrated sulfuric acid into a flask. Add 0.37 mol of crude 2,2-dimethyl-4- (2-octyldodecyloxymethyl) -1,3-dioxolane. Heat at reflux for 2.5 hours with stirring. Cool to 20 ° C, add 10 g of sodium bicarbonate and evaporate the solvent. Separate the aqueous phase while hot, wash the organic phase with hot water. Dry the organic phase on potassium carbonate, filter under buchner. 139 g of crude product are obtained, purified by distillation, eb. 230-245 ° C at 0.05 mbar; 92.1 g (67%) of 1- (2-octyldodecyloxy) -2,3-propanediol are recovered in the form of a colorless viscous oil.

Synthesis of compound V

Introduce 0.42 mol of 2,2-dimethyl-4-hydoxymethyl-1,3-dioxolane, 100 ml of cyclohexane, 1.26 mol of caustic soda in 50% aqueous solution and 0.021 mol of tetrabutylammonium hydrogen sulfate in a ball. Add 0.4 mol of benzyl chloride in 1 hour at room temperature with stirring. Heat to 45 ° C and stir at this temperature for 2 hours. Add 200 mL of water, separate the aqueous phase, wash with saturated sodium chloride solution. Dry the organic phase over magnesium sulfate, filter and evaporate the solvent. 99.3 g of crude product are obtained, purified by distillation, eb. 108-112 ° C at 0.05 mbar; 79.4 g (89%) of 2,2-dimethyl-4-benzyloxymethyl-1,3-dioxolane are recovered.

Introduce 460 mL of water, 460 mL of ethanol and 4.6 g of concentrated sulfuric acid into a flask. Add 0.35 moles of 2,2-dimethyl-4-benzyloxymethyl-1,3-dioxolane. Heat at reflux for 3 hours with stirring. Cool to 20 ° C, add 300 mL of saturated sodium chloride solution, extract 3x with 100 mL of ether. Wash the combined organic phases 2x with water. Dry the organic phase over magnesium sulfate, filter and evaporate the solvent. 43 g of crude product are obtained, purified by distillation, eb. 117-122 ° C at 0.05 mbar; 34.7 g (54%) of 1-benzyloxy-2,3-propanediol are recovered in the form of a colorless oil which solidifies on storage. Melting point: 34-35 ° C.

Synthesis of compound VI

Introduce into a flask 0.5 mol of 4-dodecylphenol, 100 ml of ethanol and 0.5 mol of 85% potassium hydroxide. Distil the ethanol out of the reaction medium under vacuum. Add 200 mL of anhydrous ethanol then 0.55 mol of 1-chloro-2,3-propanediol. Heat at reflux for 2.5 hours then allow to cool to room temperature. Filter the precipitate of salts and evaporate the solvent. 151.3 g of crude product are obtained, purified by distillation, eb. 205-225 ° C at 0.05 mbar; 51.8 g (31%) of 1- (4-dodocylphenoxy) -2,3-propanediol are recovered in the form of a very viscous yellowish oil.

Synthesis of the compound VII

Introduce 0.5 mol of oleic alcohol, 500 ml of cyclohexane, 1.5 mol of caustic soda in 50% aqueous solution and 0.025 mol of trioctylmethylammonium chloride in a flask. Add 1.0 mol epichlorohydrin in 15 minutes with stirring. Stir at 25-30 ° C for 21 hours. Add 200 mL of water, separate the aqueous phase, wash the organic phase the water. Dry the organic phase over magnesium sulfate, filter and evaporate the solvent. 208 g of crude product are obtained, purified by distillation, eb. 158-164 ° C at 0.05 mbar; 121.7 g (75%) of cis-9-octadecenyl glycidyl ether are recovered.

Introduce into a flask 4.2 mole of acetone and 0.02 mole of boron trifluoride etherate. 0.35 mol of cis-9-octadecenyl-glycidyl ether are added with stirring in the course of 2 hours at ambient temperature. Continue stirring for 2 hours. Add 0.04 mol of sodium bicarbonate and evaporate the solvent. Wash with 500 mL of water, separate the aqueous phase. 142 g of crude 2,2-dimethyl-4- (cis-9-octadecenyloxymethyl) -1,3-dioxolane are obtained.

Introduce 300 mL of water, 300 mL of methanol and 5 g of concentrated sulfuric acid into a flask. Add 0.35 mol of crude 2,2-dimethyl-4- (cis-9-octadecenyloxymethyl) -1,3-dioxolane. Heat at reflux for 3 hours with stirring. Add 10 g of sodium bicarbonate and evaporate the solvent. Separate the aqueous phase while hot, wash the organic phase with hot water. Dry the organic phase over magnesium sulphate, filter under buchner. 127.5 g of crude product are obtained, purified by distillation, eb. 189-197 ° C at 0.05 mbar; 72.6 g (60%) of 1- (cis-9-octadecenyloxy) -2,3-propanediol are recovered in the form of an oil crystallizing at room temperature.

Synthesis of compound VIII

Introduce 0.42 mol of 2,2-dimethyl-4-hydoxymethyl-1,3-dioxolane, 100 ml of cyclohexane, 1.26 mol of caustic soda in 50% aqueous solution and 0.021 mol of tetrabutylammonium hydrogen sulfate in a ball. Add 0.5 mol of epichlorohydrin in 1 hour. Heat to 45 ° C and stir at this temperature for 2 hours. Add 200 mL of water, separate the aqueous phase, wash with water and then with saturated sodium chloride solution. Dry the organic phase over magnesium sulfate, filter and evaporate the solvent. 69.3 g of crude product are obtained, purified by distillation, eb. 60-62 ° C at 0.05 mbar; 48.9 g (61%) of 2,2-dimethyl-4-glycidyloxymethyl-1,3-dioxolane are recovered.

Introduce 1 mol of isotridecanol into a flask. Add 0.01 mol of sodium metal and heat to 100 ° C. Once the sodium is completely dissolved, add 0.2 mol of 2,2-dimethyl-4-glycidyloxymethyl-1,3-dioxolane in 30 minutes at 100 ° C with stirring. Heat at this temperature for another 5 hours. Cool to room temperature, wash with 200 mL of water. Dry the organic phase over magnesium sulphate, filtered through buchner. 210 g of are obtained. The excess isotridecanol is separated by distillation, eb. 90 ° C to 0.05 mbar; the distillation residue consists of crude 2,2-dimethyl-4 - ((3-isotridecyloxy-2-hydroxypropan-1-yloxy) -methyl) -1,3-dioxolane. 60.1 g are obtained.

Introduce 200 mL of water, 200 mL of ethanol and 4 g of concentrated sulfuric acid into a flask. Add 0.155 moles of 2,2-dimethyl-4 - ((3-isotridecyloxy-2-hydroxypropan-1-yloxy) -methyl) -1,3-dioxolane. Heat at reflux for 3 hours with stirring. Cool to 20 ° C., add 150 ml of saturated sodium chloride solution, extract with 200 ml and then 2x with 50 ml of ether. Dry the organic phase over magnesium sulfate, filter and evaporate the solvent. 69.3 g of crude product are obtained, purified by distillation, eb. 240-250 ° C at 0.05 mbar; 30.3 g (56%) of 1- (3-isotridecyloxy-2-hydroxypropan-1-yloxy) -2,3-propanediol are recovered in the form of a very viscous yellowish oil.

Synthesis of compound IX

Put in a flask 80 mL of dimethylformamide and cool to 0 ° C in an ice bath. Slowly add 2.2 mol of thionyl chloride not more than 10 ° C. Add 2 mol of diethylene glycol monobutyl ether dropwise not to exceed 10 ° C with stirring. Heat to 100 ° C slowly, hydrochloric gas and sulfur dioxide emerge and must be absorbed in an extended solution of caustic soda. Once the evolution of gas is complete, cool to room temperature and add 500 mL of water. Separate the aqueous phase, wash the organic phase with 500 mL of water and 500 mL of saturated sodium chloride solution. Dry on potassium carbonate and filter. 320 g of product crude are obtained, purified by distillation, ebb. 82-83 ° C at 8 mbar; 283 g (78%) of 2- (2-butoxyethoxy) -1-chloroethane are recovered in the form of a colorless oil.

Introduce 0.5 mol of 2,2-dimethyl-4-hydoxymethyl-1,3-dioxolane, 500 ml of cyclohexane, 3.0 mol of caustic soda in 50% aqueous solution and 0.05 mol of tetrabutylammonium hydrogen sulfate. in a balloon. Add 0.5 mol of 2- (2-butoxyethoxy) -1-chloroethane at room temperature with stirring over 15 minutes. Heat to 45 ° C and stir at this temperature for 48 hours. Separate the aqueous phase, wash with 200 mL of water. Dry the organic phase over potassium carbonate, filter and evaporate the solvent. 142 g of crude product are obtained, purified by distillation, eb. 116-120 ° C at 0.05 mbar; 30.1 g (22%) of 2,2-dimethyl-4- (2- (2-butoxyethoxy) -ethoxymethyl) -1,3-dioxolane are recovered.

Introduce 130 mL of water, 130 mL of ethanol and 1.3 g of concentrated sulfuric acid in a flask. Add 0.1 mol of 2,2-dimethyl-4- (2- (2-butoxyethoxy) -ethoxymethyl) -1,3-dioxolane. Heat at reflux for 2 hours with stirring. Cool to 10 ° C., add 100 ml of saturated sodium chloride solution, extract with 100 ml and then 4x 50 ml of ether. Wash the combined organic phases with saturated sodium chloride solution. Dry the organic phase over magnesium sulfate, filter and evaporate the solvent. 28.7 g of crude product are obtained, purified by distillation, eb. 138-140 ° C at 0.05 mbar; 16.9 g (72%) of 1- (2- (2-butoxyethoxy) -ethoxy) -2,3-propanediol are recovered in the form of a colorless oil.

Synthesis of compound X

Introduce 1.0 mol of diethylene glycol monohexyl ether, 1 L of cyclohexane, 3.0 mol of caustic soda in 50% aqueous solution and 0.05 mol of trioctyl methyl ammonium chloride in a flask. Add 2.0 mol of epichlorohydrin in 30 minutes with stirring. Stir at 35 ° C for 20 hours. Add 200 mL of water, separate the aqueous phase, wash 2x the phase organic with a saturated solution of sodium chloride. Dry the organic phase over magnesium sulfate, filter and evaporate the solvent. 275 g of crude product are obtained, purified by distillation, eb. 121-123 ° C at 0.05 mbar; 184.3 g (75%) of 2- (2-hexyloxyethoxy) -ethylglycidyl ether are recovered.

In a flask, introduce 12 moles of acetone and 0.035 moles of boron trifluoride etherate. Add 0.7 mol of 2- (2-hexyloxyethoxy) -ethylglycidyl ether in the course of 1 hour at room temperature while stirring. Continue stirring for 2 hours. Add 0.07 moles of sodium bicarbonate and evaporate the solvent. Wash with 400 mL of water, separate the aqueous phase, dry over magnesium sulphate and filter through a beaker. 180.5 g of crude product are obtained, purified by distillation, eb. 120-123 ° C at 0.05 mbar; 98.5 g (46%) of 2,2-dimethyl-4- (2- (2-hexyloxyethoxy) -ethoxymethyl) -1,3-dioxolane are recovered.

Add 330 mL of water, 330 mL of methanol and 1.5 g of concentrated sulfuric acid to a flask. Add 0.31 mol of 2,2-dimethyl-4- (2- (2-hexyloxyethoxy) -ethoxymethyl) -1,3-dioxolane in 20 minutes. Heat at reflux for 2 hours with stirring. Add 10 g of sodium bicarbonate and evaporate the solvent. Add 100 mL of saturated sodium chloride solution, extract with 3 x 200 mL and then 2x 50 mL of ether. Dry the combined organic phases over magnesium sulfate, filter and evaporate the solvent. 112.3 g of crude product are obtained, purified by distillation, eb. 158-162 ° C at 0.05 mbar; 42.7 g (52%) of 1- (2- (2-hexyloxyethoxy) -ethoxy) -2,3-propanediol are recovered in the form of a slightly yellow oil.

II: Lubrication test (tribometric example)

The various glycol ethers as prepared above are tested by disk pion tribology under the following conditions: Pawn: Steel 20AP 900HV Pawn radius: 1.5 mm Disk: Ruby Charge : 10 N Speed: 10 mm / s Friction radius: 3 mm Distance: Variable Number of tours: Variable Humidity : 85% Temperature : 18-25 ° C

The lubricant is deposited in superabundant quantity.

The average coefficient of friction is measured over the first 10 meters.

For comparison, a dry test is carried out. This test corresponds to direct slip without added lubricant.

For comparison also, the same test is carried out with a Synt-A-Lube ™ 9010 oil marketed by The Swatch Group R & D Ltd. Moebius Division.

The results are reported in the table below: Compound Coefficient of friction (average over 10 m) Dry test (comp.) 0.46 III (inv.) 0.08 IV (inv.) 0.06 VI (inv.) 0.08 VII (inv.) 0.06 VIII (inv.) 0.08 IX (inv.) 0.07 X (inv.) 0.06 Synt-A-Lube ™ 9010 oil (comp.) 0.07

These results show that the glycerol ethers used in the present invention make it possible to obtain low or very low friction coefficients of less than 0.08 and preferably less than 0.06.

In addition, the glycerol ethers are stable over time so that the lubricating composition according to the invention is not altered over time, unlike glycerol.

Finally, certain compounds used according to the invention have high viscosities at ambient temperature (consistency of a grease) and make it possible to formulate lubricating compositions with a high viscosity at ambient temperature (consistency of a grease). Consequently, the compounds used according to the invention make it possible not to use an epilame in order to prevent the spreading of the lubricating composition. In contrast, the Synt-A-Lube ™ 9010 oil used in the comparative tribometric example, the 9415 grease used in the comparative watch example or the glycerol-based lubricating compositions are fluid or very fluid, so that require the use of an epilame.

III: Measurement of amplitude (watchmaking test)

The amplitude of a rocker lubricated by one of the lubricant compositions according to the invention is measured (conventional lubrication of the rock of pivoting of the balance shaft).

The amplitude of a balance wheel is also measured, the escapement having been lubricated by one of the lubricating compositions according to the invention (conventional lubrication of the teeth of the escape wheel).

By way of comparison, the same tests are carried out under the same measurement conditions with Moebius oil 9415 or Moebius 9010 sold by The Swatch Group R & D Ltd. Moebius Division.

The amplitudes are measured in degrees, the measurements being made on a representative sample of movements, with the same equipment.

The results are shown in the tables below:
Lubrication of the exhaust: Lubricant Composition comprising a 50/50 mixture of compounds VII and X Moebius 9415 Average gain Horizontal 323 309 5% Vertical 311 290 7%
Lubrication of the balance: Lubricant Composition comprising compound VII Composition comprising a 70/20 mixture of compounds VII and X Moebius 9010 Average gain Horizontal 316 318 310 2% Vertical 287 287 277 3%

The lubricating compositions according to the invention are therefore more advantageous than the known oils because they hold in place without resorting to an epilame, they do not deteriorate over time, while having tribological properties equal to or better than those of known oils. .

Claims (4)

1. Timepiece comprising at least two elements in contact and mobile in relation to each other, at least one of said elements having a contact surface with the other element that is lubricated by means of a lubricating composition, characterized in that said lubricating composition comprises at least one glycerol ether selected from the group comprising:

   

   

   

   

   

   

   

   and mixtures thereof.
2. The timepiece according to the preceding claim, characterized in that one of the elements is a pallet lever and the other element is an escapement wheel.
3. Use as lubricating agent - in a lubricating composition to lubricate a contact surface of at least one element in contact with another element of a timepiece, said elements being mobile in relation to each other - of at least one glycerol ether selected from the group comprising:

   

   

   

   

   

   

   

   and mixtures thereof.
4. Chemical compound of formula: