Abstract:
Tertiary diamines having two saturated heterocyclic rings joined by an aliphatic carbon chain, of the general formula ##STR1## in which each A is a two- to four-membered aliphatic carbon chain substituted if desired by one or more C 1  -C 4  -alkyl groups, are prepared in one stage by catalytic hydrogenation of the corresponding dinitriles of the general formula 
     
       N.tbd.C--A--C.tbd.N                                        II 
     
     The diamines preparable in accordance with the invention are particularly suitable as catalysts for the production of polyurethanes.

Description:
This application is a 371 of PCT/EP95/01773 filed May 10, 1995. 
    
    
     This application is a 371 of PCT/EP95/01773 filed May 10, 1995. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     Tertiary diamine, its use as catalyst, and process for preparing tertiary diamines 
     The present invention relates to a process for preparing tertiary diamines having two saturated heterocyclic rings of aliphatic dinitriles, which rings are connected by an aliphatic carbon chain, and to a novel tertiary diamine and its use as a catalyst for the preparation of polyurethanes. 
     Tertiary diamines, for example 1,5-dipiperidino-pentane, are valuable compounds owing to their high basicity and relatively low volatility and can be employed, for example, as hardeners in epoxy resins (German Patent No. C10 32 920). 
     2. Background of the Invention 
     A relatively new use of such compounds is as starting material for the preparation of emulsion stabilizers for blood substitutes (European Published Patent Application No. A 0 415 263). 
     The preparation processes known to date for these compounds (see for example European Published Application No. A 0 415 263, p. 8) generally require two different starting substances and in some cases produce unwanted waste products (salts) and in some cases give unsatisfactory yields. Also known are processes in which, for example, piperidine is reacted under the influence of a catalyst to form 1,5-dipiperidinopentane (German Patent No. C10 34 180). These processes too often give rise to only poor yields. 
     BROAD DESCRIPTION OF THE INVENTION 
     It was therefore an object of the present invention to provide a simple process which gives tertiary diamines having two saturated heterocyclic rings, connected by an aliphatic carbon chain, in good yield without the production of relatively large quantities of waste products. 
     This object is achieved in accordance with the invention by the process. 
     It has surprisingly been found that tertiary diamines of the general formula ##STR2## in which each A is identical and is a two- to four-membered aliphatic carbon chain, and which may if desired be substituted by one or more C 1  -C 4  -alkyl groups, can be prepared in one stage by hydrogenating the corresponding aliphatic dinitriles of the general formula 
     
         N.tbd.C--A--C.tbd.N                                        II 
    
     in which A is as defined above. A by-product of this process is 4 mol of ammonia per mole of diamine. 
     The hydrogenation is expediently carried out at a temperature of 100°-250° C. and under elevated pressure in the presence of a supported palladium catalyst. 
     As supported palladium catalyst it is preferred to employ palladium on alumina. Good results have been obtained with relatively low palladium contents of, for example, 1%. 
     The hydrogen pressure in the course of the hydrogenation is preferably greater than 10 bar and is, for example, about 50 bar. The reaction temperature established is preferably a temperature from 150° to 220° C., for example 180° C. 
     The hydrogenation is preferably carried out continuously. For this purpose, the dinitrile is passed over the catalyst together with hydrogen in a suitable reactor. 
     A suitable carbon chain A is preferably 1,2-ethanediyl, 1,3-propanediyl, 1,4-butanediyl or 1,3-butanediyl (.tbd.1-methyl-1,3-propanediyl), corresponding to the dinitriles succinonitrile, glutaronitrile, adiponitrile or 2-methylglutaronitrile. 
     To the dinitrile II it is possible to add up to twice the molar quantity of the corresponding cyclic amine ##STR3## in which A is as defined above, i.e. addition up to a molar ratio of II to III of 1:2, the amine III being incorporated into the product I. This has the advantage that it is possible by this means to recycle the cyclic amine III, which is also formed in the novel process as a by-product, and ultimately to convert it into the desired product I. 
     Preferably, 3-methylpiperidine is employed as cyclic amine II and 2-methylglutaronitrile as dinitrile II. 
     A particularly preferred starting material is 2-methylglutaronitrile, which as novel product gives 1,5-bis(3-methylpiperidino)-2-methylpentane of the formula ##STR4## This compound is particularly suitable as a catalyst for the preparation of polyurethanes, polyurethane/polyurea mixtures and polyureas. Using this catalyst, the polymers can be prepared both as elastomers and in the form of foams. 
     The examples which follow illustrate the implementation of the novel process. 
     The hydrogen streams are based on standard conditions, and the throughput is in each case indicated in g of starting material per g of catalyst per hour. The composition of each product was determined by gas chromatography. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     EXAMPLE 1 
     3 g of a Pd/Al 2  O 3  catalyst (1% Pd, particle size 0.315-1 mm) were placed in a reactor (13 mm .o slashed.). In the stream of hydrogen (120 ml/min), a temperature of 180° C. and a pressure of 50 bar were established. Then 99.8% pure 2-methylglutaronitrile (MGN) was metered in. The throughput was 2.1 g/(g·h), and the molar ratio of MGN to H 2  was 1:5. With complete conversion, the concentrations in the product stream after a reaction period of 40 h were found (GC) to be as follows: 82.5% 1,5-bis(3-methylpiperidino)-2-methylpentane, 0.4% isomer mixture of 2-methyl-5-(3-methylpiperidino)pentanenitrile (major component) and 4-methyl-5-(3-methylpiperidino)pentanenitrile, 8.4% 3-methylpiperidine, remainder: 8.7%. The product mixture was water-clear. 
     EXAMPLE 2 
     3 g of a Pd/MgCl 2  Al 2  O 3  catalyst (particle size 0.315-1 mm) containing 1% Pd and 1.2% Mg were placed in a reactor (13 mm .o slashed.). In the stream of hydrogen (120 ml/min), a temperature of 170° C. and a pressure of 50 bar were established. Then 99.8% pure 2-methylglutaronitrile (MGN) was metered in. The throughput was 2.1 g/(g·h). With complete conversion, the concentrations in the product stream after a reaction period of 22 h were found (GC) to be as follows: 78.4% 1,5-bis(3-methylpiperidino)-2-methylpentane, 8.3% isomer mixture of 2-methyl-5-(3-methylpiperidino)pentanenitrile (major component) and 4-methyl-5-(3-methylpiperidino)pentanenitrile, 3.0% 3-methylpiperidine, remainder: 10.3%. The product mixture was water-clear. 
     EXAMPLE 3 
     3 g of a Pd/MgCl 2  Al 2  O 3  catalyst (particle size 0.315-1 mm) containing 1% Pd and 1.2% Mg were placed in a reactor (13 mm .o slashed.). In the stream of hydrogen (120 ml/min), a temperature of 190° C. and a pressure of 50 bar were established. Then 99.8% pure 2-methylglutaronitrile (MGN) was metered in. The throughput was 2.1 g/(g·h). With complete conversion, the concentrations in the product stream were found (GC) to be as follows: 76.3% 1,5-bis(2-methyl-piperidino)-2-methylpentane, 4.3% of 2-methyl-5-(3-methylpiperidino)pentanenitrile, 15.3% 3-methylpiperidine, remainder: 4.1% (reaction time: 90 h). The water-clear product was distilled, and 1,5-bis(3-methylpiperidino)-2-methylpentane was obtained in a purity of 99.5% (108° C./1.3 mbar). 
     Analytical data: 
     1,5 -bis(3-methylpiperidino)-2-methylpentane: 
     C 18  H 36  N 2  calculated: C 77.1 H 12.9 N 10.0 
     found: C 77.2 H 13.4 N 10.0 
     Molar mass 280 (MS) 
     
         ______________________________________.sup.1 H--NMR (CDCl.sub.3, 400 MHz) δ:             2.65-2.90(m, 4H,             ring-N--CH.sub.2); 2.25(t,             2H, N--CH.sub.2 --CH.sub.2); 2.02             (m, 2H, N--CH.sub.2 --CH):             1.34-1.82(m, 16H);             0.78-1.08(m, 12H, CH.sub.3             etc.).(Diastereomer mixture).sup.13 C--NMR (CDCl.sub.3, 100 MHz) δ:             54.1-66.3(N--CH.sub.2); 33.3             (N--CH.sub.2 --CH.sub.2 --CH.sub.2); 30.5-             31.2(CH; 24.5-25.7             (N--CH.sub.2 --CH.sub.2); 18.5-19.9             (CH.sub.3).______________________________________ 
    
     
         ______________________________________.sup.1 H--NMR (CDCl.sub.3, 400 MHz) δ:                 1.40-2.85(m, 16H, CH+(Major component)     CH.sub.2); 1.32(d, 3H, CH.sub.3 --                 CH--CN); 0.86(d, 3H,                 ring-CH.sub.3)..sup.13 C--NMR (CDCl.sub.3, 100 MHz) δ:                 123.01(s); 62.20(t);(Main component)      58.28(t); 54.12(t);                 33.13(t); 32.23(t);                 31.19(d); 25.62(t);                 25.47(d); 24.41(d);                 19.77(g); 18.07(q).______________________________________ 
    
     EXAMPLES 4-7 
     Use of 1,5-bis(3-methylpiperidino)-2-methylpentane as polyurethane catalyst: 
     Abbreviations: 
     VL: Desmodur® VL from Bayer, aromatic diisocyanate containing about 32% -NCO 
     D550U: Desmophen® 550U, polypropylene glycol from Bayer, trifunctional with 10.5%-OH 
     DBU: Diazabicyclo 5.4.0!undec-7-ene 
     BMPMP: 1,5-bis(3-methylpiperidino)-2-methylpentane 
     DBU was used as comparison catalyst. Desmophen was placed together with the amine (DBU or BMPMP) and thorough mixing was carried out to give a solution. In Example 6 and 7, water was added as well, giving an emulsion/solution. A weighed quantity of isocyanate (VL) was added with vigorous stirring at time t=0. A note was made of the points in time at which 
     the solution is no longer cloudy, 
     marked heating can be detected, 
     the mixture becomes solid. 
     The results (BMPMP in comparison with DBU) are evident from Table 1. 
     The addition of water in Examples 6 and 7 brings about partial hydrolysis of the isocyanate to the corresponding amine and the evolution of CO 2 . The corresponding amine reacts with the remaining isocyanate to form a urea compound, while the CO 2  acts as blowing agent in the formation of foam. 
     
                                           TABLE 1__________________________________________________________________________Examplet s!    t s!            t s!                VL D550U                       DBU                          BMPMP                               H.sub.2 O                                  Volume                                      NotesNo.  no longer cloudy        heating            solid                 g!                    g!  g!                           g!   g!                                   ml!                                      (colour etc.)__________________________________________________________________________4     60      62  90 50.0                   55.0                       0.5                          --   --     brown, clear hard5     70      90 360 50.0                   55.0                       -- 0.5  --     ochre, hard foam6    200     200 1200                50.0                   45.0                       0.1                          --   0.5                                  450 ochre, foam7    210     210 900 50.0                   45.0                       -- 0.1  0.5                                  450 ochre, foam__________________________________________________________________________ 
    
     EXAMPLE 8 
     Investigation regarding the reaction mechanism: 
     3 g of a Pd/Al 2  O 3  catalyst (1% Pd, particle size 0.315-1 mm) were placed in a reactor (13 mm .o slashed.). In the stream of hydrogen (120 ml/min) a temperature of 180° C. and a pressure of 50 bar were established. Then 99.8% pure 2-methylglutaronitrile (MGN) was metered in. The throughput was 2.1 g/(g·h). With complete conversion, the concentrations (GC) established in the product stream after a reaction period of 6 h were as follows: 78% 1,5-bis(3-methylpiperidino)-2-methylpentane, 21% 3-methylpiperidine (MPI), remainder: 1%. Subsequently, 3-methylpiperidine (MPI) instead of 2-methylglutaronitrile (MGN) was passed over the catalyst. &gt;99.5% of the MPI passed over the catalyst unchanged. Then MPI and MGN in a molar ratio of 2:1 were passed over the catalyst. The concentrations (GC) established in the product stream were as follows: 18.9% MPI, 70.6% 1,5-bis(3-methylpiperidino)-2-methylpentane, remainder: 10.5%. The experimental results show that MPI alone is not converted to 1,5-bis(3-methylpiperidino)-2-methylpentane. However, when added to MGN, MPI is incorporated into the desired product. 
     EXAMPLE 9 
     3 g of a Pd/Al 2  O 3  catalyst (1% Pd, particle size 0.315-1 mm) were placed in a reactor (13 mm .O slashed.). In the stream of hydrogen (140 ml/min) a temperature of 180° C. and a pressure of 50 bar were established. Then glutaronitrile was metered in. The throughput was 2.1 g/(g·h). At a conversion of 98.6%, the product stream contained, after a reaction period of 4 h, 34.6% 5-piperidinopentanenitrile, 32.4% 1,5-dipiperidinopentane and 5.5% piperidine (GC). 
     EXAMPLE 10 
     3 g of a Pd/Al 2  O 3  catalyst (1% Pd, particle size 0.315-1 mm) were placed in a reactor (13 mm .o slashed.). In the stream of hydrogen (120 ml/min) a temperature of 180° C. and a pressure of 50 bar were established. Then adiponitrile was metered in. The throughput was 2.1 g/(g·h). At a conversion of 98.8%, the product stream contained, after a reaction period of 3 h, 26% 6-(hexahydro-1H-azepin-1-yl)hexanenitrile, 20% 1,6-bis(hexahydro-1H-azepin-1-yl)hexane and 13% hexahydro-1H-azepine (GC). 
     EXAMPLE 11-13 
     3 g of a Pd/Al 2  O 3  catalyst (1% Pd, particle size 0.315-1.0 mm) were placed in a reactor (13 mm .o slashed.). In the stream of hydrogen (120 ml/min), the reactor was heated at 50 bar to 180° C.. Then the metered addition of 99.8% pure 2-methylglutaronitrile was begun. The molar ratio of MGN to H 2  and the MGN throughput were varied and the following results were obtained. 
     EXAMPLE 11 
     MGN:H 2  =1:10 
     Throughput: 2.10 g/(g·h) 
     
         ______________________________________Product composition______________________________________1,5-Bis(3-methylpiperidino)-2-methylpentane                    71.2%2(4)-Methyl-5-(3-methylpiperidino)pentanenitrile                     0.7%2-Methylglutaronitrile   0%3-Methylpiperidine        9.2%Remainder                18.9%______________________________________ 
    
     EXAMPLE 12 
     MGN:H 2  =1:3.4 
     Throughput: 2.10 g/g·h) 
     
         ______________________________________Product composition______________________________________1,5-Bis(3-methylpiperidino)-2-methylpentane                    44.2%2(4)-Methyl-5-(3-methylpiperidino)pentanenitrile                    20.1%2-Methylglutaronitrile   8.4%3-Methylpiperidine       3.6%Remainder                23.7%______________________________________ 
    
     EXAMPLE 13 
     MGN:H 2  =1:5 
     Throughput: 1.73 g/(g·h) 
     
         ______________________________________Product composition______________________________________1,5-Bis(3-methylpiperidino)-2-methylpentane                    80.4%2(4)-Methyl-5-(3-methylpiperidino)pentanenitrile                     3.6%2-Methylglutaronitrile   0%3-Methylpiperidine        5.7%Remainder                10.2%______________________________________ 
    
     Examples 1 and 11-13 show that the highest selectivity for the formation of the bis(methylpiperidino) compound is reached at a molar ratio of MGN to H 2  of approximately 1:5.