Abstract:
The present invention relates to terpene ethers of the general formula (I)                            
     in which the substituents have the meanings defined in the description, to a process for their preparation and to their use. 
     The novel terpene ethers are suitable as traction fluids, as fragrances, as solvents and as reactive intermediates.

Description:
BACKGROUND OF THE INVENTION 
     Lubricated traction gears require special power transmission fluids which transmit the torque of the driving part to the driven part by means of friction. The lubricating film in the contact zone between the two roller members is subjected to shearing by the transmitted frictional forces. 
     The profile of requirements for traction fluids comprises, inter alia, 
     good low-temperature flow behavior and sufficient viscosity at operation temperature 
     sufficiently high coefficient of friction over the operation temperature range 
     low evaporation losses. 
     EP-A-082 967 describes organic compounds for use as fluid for the transmission of frictional forces. DE-A-3 321 773 and DE-A-3 337 503 describe cyclic hydrocarbons for use as fluid for traction drive means. DE 1 644 926 describes condensed saturated hydrocarbons as traction fluid. Furthermore, EP-A-319 580 mentions hydrocarbon diesters for use as traction fluids. DE-A-3 327 014 describes terpene ethers. 
     DE-A-3 327 014 describes, inter alia, Example 6 (here, referred to below as Comparative Example 1).                           
     Comparative Example 1 tends to crystallize on prolonged standing, has a melting point of from 72 to 75° C. and thus does not meet the requirements for good low-temperature behavior. For use as traction fluid, the solidification points must be substantially below −20° C. 
     SUMMARY OF THE INVENTION 
     It was thus the object of the present invention to provide novel compounds having improved low-temperature behavior. 
     Surprisingly, it was found that certain terpene ethers, in spite of higher molecular weights, nevertheless have substantially lower solidification points and thus meet the criterion of low-temperature flowability. 
     The invention relates to novel terpene ethers, a process for their preparation and their use, inter alia, as traction fluids or in the area of fragrances and solvents. 
     The invention thus relates to novel terpene ethers of the general formula I                           
     in which 
     m is a number from 2 to 5, 
     A is a branched or straight-chain alkylene group having 2 to 5 carbon atoms, 
     R is hydrogen, 
     C 8 -C 4 -alkyl, which is optionally substituted by C 5 -C 12 -cycloalkyl, by C 7 -C 12 -bicycloalkyl or by C 8 -C 11 -tricycloalkyl, it being possible for the cycloalkyl radical or the tricycloalkyl radical to carry a substituent —CH 2 —O—R 1 , or it being possible for the cycloalkyl radical to be substituted by a radical —O—R 1 , 
     C 5 -C 12 -cycloalkyl, which may be substituted by a radical —O—R 1 , 
     C 7 -C 12 -bicycloalkyl, or 
     C 8 -C 12 -tricycloalkyl, 
     R 1  being hydrogen, 
     C 1 -C 18 -alkyl, 
     C 5 -C 12 -cycloalkyl, 
     C 7 -C 12 -bicycloalkyl, or 
     cycloalkyl-, bicycloalkyl- or tricycloalkyl-substituted C 1 -C 6 -alkyl. 
     It has also surprisingly been found that these novel terpene ethers have at least an equally high coefficient of friction as, in some cases even a higher coefficient of friction than, Comparative Example 1. This contradicts all expectations based on systematic friction measurements using model substances (literature: Dokumentation des BMFT: Tribologie [BMFT Documentation: Tribology] Vol. 2, published by Springer Verlag Berlin, Heidelberg, N.Y., 1982, pages 281-313). According to this, a decrease in the coefficient of friction under elastohydrodynamic operating conditions would be expected with increasing chain length of the ether bridge between the isobomyl radicals, owing to the associated decrease in the steric hindrance. 
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Compounds of the formula (I) in which A is a straight-chain or branched alkylene chain having 2-5 carbon atoms, m is 2 or 3 and R has the meaning of one of the radicals mentioned below: hydrogen, alkyl having 3-5 carbon atoms, cycloalkyl having 5-12 carbon atoms, bicycloalkyl having 7-12 carbon atoms and tricycloalkyl having 8-12 carbon atoms are preferred. 
     Compounds of the formula (I) in which m is 2 or 3 and R is hydrogen or C 7 -C 12 -bicycloalkyl are very particularly preferred. 
     In the terpene ethers according to the invention—according to IUPAC nomenclature 1,7,7-trimethylbicyclo[2.2.1]hept-2-yl ethers (=isobomyl ethers) the 1,7,7-trimethylbicyclo[2.2.1]hept-2-yl radical may be in the d or I form, preferably in the form of the racemate and the radical                           
     in the exo and/or endo form. 
     The novel compounds can be prepared by methods known per se. 
     The preferred procedure for the preparation of the novel ethers starts from camphene, which is reacted with the alcohols of the general formula                           
     in which R has the abovementioned meaning. In the reaction taking place in the presence of acidic catalysts according to the equation:                           
     the camphene undergoes an intermediate Wagner-Meerwein rearrangement reaction to give a camphene intermediate. 
     The synthesis is carried out at temperatures between room temperature (20° C.) and 160° C., preferably at from 50 to 140° C. and in particular at from 70 to 120° C. Depending on the desired product, the reactants can be used in equimolar amounts or an excess of one or other reactant can be employed. An excess of camphene proved advantageous for the synthesis of diisobornyl ethers. 
     Catalysts used are mineral acids, such as sulfuric acid, perchloric acid, phosphoric acid, chlorosulfonic acid, etc., strong organic acids, such as p-toluenesulfonic acid, methanesulfonic acid and camphor-10-sulfonic acid, acidic ion exchangers or Friedel-Crafts catalysts, such as boron trifluoride and its adducts (e.g. etherates, glacial acetic acid complex), aluminum chloride, zinc chloride, PdCl 2 , Pd(OAc) 2 , SbCl 3 , SbCl 5 , YtCl 3 , LaCl 3 , zeolites and others, in amounts of from 0.1 to 10, preferably from 0.5 to 6 and in particular from 1 to 4, % by weight, based on camphene used. 
     The reaction can be carried out in the presence or in the absence of inert solvents. Suitable solvents are, for example, aliphatic hydrocarbons such as pentane, hexane, naphtha fractions, chloroform or carbon tetrachloride, aromatic hydrocarbons such as toluene, xylene or chlorobenzene, cycloaliphatic hydrocarbons, such as cyclohexane or cyclooctane, or ethers, such as dioxane, dibutyl ether or ethylene glycol dimethyl ether. The procedure without the addition of solvent is particularly advisable. 
     In the reaction, in general, all reactants can be initially introduced in their total amount, including the catalyst. In some cases, the reaction takes place slightly exothermally so that in this case it is advantageous initially to introduce the catalyst and the alcohol and to add the camphene at the desired temperature. 
     Diethylene glycol, triethylene glycol, dipropylene glycol and tripropylene glycol are particularly preferred as examples of alcohols which are reacted with camphene. 
     The purification of the reaction products is carried out in general after removal of the catalyst (e.g. washing with water or neutralization by means of bases or simple filtration) by distillation, but for some intended uses a distillation is not necessary. A further possibility for purification is recrystallization from suitable solvents. 
     The preferred reaction products are low-viscosity to high-viscosity liquids which are colorless to faintly yellow. 
     As already mentioned, the novel compounds are surprisingly distinguished by the fact that, in comparison with Comparative Example 1 (Example 6 from DE-A-332 701 A 1), they do not solidify down to −30° C. When they are used as traction fluids, the compounds described can be employed alone or as mixtures with other substances, with the main proportion of these mixtures comprising one or more of the compounds described here. 
     In the traction fluid, the terpene ether is used in a concentration of at least 5% by weight, preferably in a concentration of from 20 to 95% by weight. 
     Some of the novel compounds have a pronounced fragrance character and can therefore be used alone as fragrances or in a fragrance combination, i.e. in mixtures with synthetic and natural oils, alcohols, aldehydes, ketones or esters, and they are furthermore suitable for perfuming soaps, detergents, powders, bath oils, hair cosmetics, creams and further known fragrance-containing formulations. Owing to their consistency, a major part of the novel terpene ethers is of interest as fixing agents for fragrances, and the compounds suitable for this purpose are viscous liquids and therefore have the property of greatly reducing the volatility of fragrances. Furthermore, some of the products can be used as solvents, for example for resins and coating materials. 
     Finally, those members of the novel ethers which have a free hydroxyl group are suitable as reactive intermediates, for example for the synthesis of crop protection agents, pesticides and drugs. 
    
    
     EXAMPLES 
     Table 1 summarizes the compounds prepared by the general method described below, for illustrating the invention. 
     General method for synthesizing terpene ethers. 
     Catalyst is added to 1 mol of the corresponding dry alcohol and the mixture is heated to 80° C. until the suspension is stirrable, and molten technical-grade camphene is then added dropwise. Stirring is then carried out for 24 h at 80° C. Thereafter, water is added at 80° C. to decompose the catalyst, stirring is effected for 30 min and the aqueous phase is then separated off. This process is repeated once more. The unreacted camphene is removed by means of steam distillation. The oil bath is heated to 140° C. for this purpose. The condensate is analyzed by GC. To remove residual water and low-boiling byproducts, the residue is heated to 170° C. in a vacuum at 40 mbar. After foam formation has died down, the solution is filtered through a folded filter, the product, comprising mono- and diisobomyl ether, being obtained as a low-viscosity oil. Mono- and diether can be separated by subsequent distillation. 
     
       
         
               
             
               
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Synthesis of terpene ethers 
               
             
          
           
               
                   
                   
                   
                   
                   
                   
                 Molar 
               
               
                   
                   
                 Equivalent of 
                 Catalyst 
                 B.p. 
                   
                 mass** 
               
               
                 Alcohol 
                 Product 
                 camphene 
                 (equivalents) 
                 ° C. (pressure) 
                 M.p. 
                 (M + H)  
               
               
                   
               
               
                 Ethylene glycol 
                 Ethylene glycol diisobornyl ether 
                  3* 
                 AlCl3 
                 168-169 
                 72-75° C. 
                 — 
               
               
                   
                 Comparative Example 1 
                   
                 (0.037) 
                 (1.3 mbar) 
               
               
                 Diethylene glycol 
                 Diethylene glycol isobornyl ether 
                 4 
                 BF3—2CH3CO2H 
                 n.d. 
                 &lt;−30° C. 
                 243 
               
               
                   
                 Example 1 
                   
                 (0.037) 
               
               
                 Diethylene glycol 
                 Diethylene glycol diisobornyl ether 
                 4 
                 BF3—2CH3CO2H 
                 n.d. 
                 &lt;−30° C. 
                 379 
               
               
                   
                 Example 1a 
                   
                 (0.037) 
               
               
                 Triethylene glycol 
                 Triethylene glycol isobornyl ether 
                 4 
                 BF3—2CH3CO2H 
                 148-152 
                 &lt;−30° C. 
                 287 
               
               
                   
                 Example 2 
                   
                 (0.037) 
                 (0.4 mmHg) 
               
               
                 Triethylene glycol 
                 Triethylene glycol diisobornyl ether 
                 4 
                 BF3—2CH3CO2H 
                 184 
                 &lt;−30° C. 
                 423 
               
               
                   
                 Example 2a 
                   
                 (0.037) 
                 (0.1 mmHg) 
               
               
                 1,2-Dipropylene glycol 
                 1,2-Dipropylene glycol isobornyl ether 
                 4 
                 BF3—2CH3CO2H 
                 n.d. 
                 &lt;−30° C. 
                 271 
               
               
                   
                 Example 3 
                   
                 (0.037) 
               
               
                 1,2-Dipropylene glycol 
                 1,2-Dipropylene glycol diisobornyl ether 
                 4 
                 BF3—2CH3CO2H 
                 177 
                 &lt;−30° C. 
                 407 
               
               
                   
                 Example 3a 
                   
                 (0.037) 
                 (0.4 bar) 
               
               
                 1,2-Tripropylene glycol 
                 1,2-Tripropylene glycol isobornyl ether 
                 4 
                 BF3—2CH3CO2H 
                 147 
                 &lt;−30° C. 
                 329 
               
               
                   
                 Example 4 
                   
                 (0.037) 
                 (0.4 mmHg) 
               
               
                 1,2-Tripropylene glycol 
                 1,2-Tripropylene glycol diisobornyl ether 
                 4 
                 BF3—2CH3CO2H 
                 193 
                 &lt;−30° C. 
                 465 
               
               
                   
                 Example 4a 
                   
                 (0.037) 
                 (0.4 mmHg)  
               
               
                   
               
               
                 *Toluene as solvent  
               
               
                 **Mass spectrum DCI (Desorption Chemical Ionization)  
               
               
                 n.d. not determined since fraction was contaminated with byproducts  
               
             
          
         
       
     
     Table 2 
     Coefficients of Friction of Model Substances of Variable Chain Length 
     The friction measurement was carried out on a two-disk deskstand as described in the publication cited on page 2. Mean values of the coefficients of friction were compared with the following limits of the operating parameters. 
     Mean Hertsch pressure p m =500 . . . 1260 N/mm 2    
     Circumferential velocity v=0.42 . . . 8.4 m/s 
     Slip s less than 6% 
     Temperature T=50° C. 
     Roughness of the friction body surfaces corresponding to that of conventional friction gear designs. 
     
       
         
               
               
               
             
               
               
               
             
           
               
                   
                   
               
               
                   
                 Model substance 
                 Mean coefficient of friction 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 A1 
                 
                   
                             
                     
                         
                         
                     
                   
                 
                 0.086 
               
               
                   
               
               
                 A2 
                 
                   
                             
                     
                         
                         
                     
                   
                 
                 0.076 
               
               
                   
               
               
                 A3 
                 
                   
                             
                     
                         
                         
                     
                   
                 
                 0.075 
               
               
                   
               
               
                 B1 
                 
                   
                             
                     
                         
                         
                     
                   
                 
                 0.08 
               
               
                   
               
               
                 B2 
                 
                   
                             
                     
                         
                         
                     
                   
                 
                 0.078 
               
               
                   
               
               
                 C1 
                 
                   
                             
                     
                         
                         
                     
                   
                 
                 0.017 
               
               
                   
               
               
                 C2 
                 
                   
                             
                     
                         
                         
                     
                   
                 
                 0.016 
               
               
                   
               
               
                 C3 
                 
                   
                             
                     
                         
                         
                     
                   
                 
                 0.015 
               
               
                   
               
               
                 Comparative 
                 Ethylene glycol diisobornyl ether 
                 0.094 
               
               
                 Example 1 
               
               
                 Ex. 1a 
                 Diethylene glycol diisobornyl ether 
                 0.090 
               
               
                 Ex. 2a 
                 Triethylene glycol diisobornyl ether 
                 0.068 
               
               
                 Ex. 3a 
                 Dipropylene glycol diisobornyl ether 
                 0.099 
               
               
                 Ex. 4a 
                 Tripropylene glycol diisobornyl ether 
                 0.086