US 2606928 A
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Patented Aug. 12, 1952 PREPARATION OF AMINO ALICYCLIC COMPOUNDS:
' Archie E. Barkdoll, Clarenc ,R. Graef, Wilmington,
du Pont de Nemours &
Del., a corporation of D e D. Bell, and Elbridge Del., assignors to E. I. Company, Wilmington, elaware No Drawing. Application November 18, 1947,
Serial No. 786,780
8 Claims. (Cl. 260-563) This invention relates to a process for hydrogenating certain di-(p-aminoaryl) alkanes to the corresponding di-(p-aminoalicyclic) alkanes. In a particular embodiment, it relates to a process for hydrogenating di-(p-aminophenyl) methane to di-(p-aminocyclohexyl) methane. m
'I?he di-(p-aminoalicyclic) alkane products obtained by the process of this invention may be represented by the formula where R1 and R4 are of the group consisting of hydrogen atoms and alkyl radicals, R2 is of the group consisting of hydrogen atoms and alkyl and alkoxy radicals attached to a carbon atom in the ring structure, the various R2 substituents being the same or different and at least 3 of the R2 substituents on any given ring being hydrogen atoms, and R3 is a saturated divalent acyclic hydrocarbon radical containing not more than six carbon atoms. The R1, R2 and R4 substituents may be, for instance, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, secondary-butyl, tertiary-butyl groups, or higher alkyl groups, or, in the case of R2, the corresponding alkoxy groups. These compounds are described in copending application S. N. 615,912 of William Kirk, Jr., Richard S. Schreiber, and Gerald M. Whitman, which discloses a process for their preparation comprising hydrogenation, in the presence of a ruthenium catalyst, of the corresponding di-(p-aminoaryl) alkane compounds having the general formula (II) /CR2CR2 -R1HNC 0413- c-NHR.
oR2=oR, 011F032 V wherein the substituents R1, R2, R3 and R4 have the same meaning ascribed to them above. The said application further discloses that, because of their structural configuration, these alicyclic diamines can exist in three or more'stereoisomeric' forms and that the ratio of these 2 1 melting isomers yield polyamides which tend to be relatively soluble, transparent, tough and fusible, while the higher-melting isomers ,yield polyamides which tend to be relatively insoluble, opaque, and either high-melting or infusible.
It is an object of this invention to provide a novel process for. carrying out the hydrogenation of the above-described 'di-(p-aminoaryl) alkane compounds to the corresponding di-(paminoalicyclic) alkanes. Another object of this invention is to provide a method for carrying out this hydrogenation process in such a way as to obtain di-(p-aminoalicyclic) alkane compositions containing high ratios of the lowermelting isomers. Another object is to provide a practical process for preparing di-(p-aminoalicyclic) alkane compositions of the type which can be condensed with adipic acid to produce transparent, fusible polyamides. A further object is to prepare di-(p-aminocyclohexyl) methane in a form which is liquid at room temperature. A still further object is to prepare di-(p-aminocyclohexyl) methane v compositions which can be condensed with adipic acid to produce transparent, fusible polyamides. Another object is to provide a continuous preparing the di-(p-aminoalicyclic) alkanes. Other objects of the invention will appear hereinafter.
According to this invention, we provide a process for hydrogenating a di-(p-aminoaryl) alkane compound of the type represented by Formula II to the corresponding di-(p-aminoalicyclic) alkane compound of Formula I which comprises continuously passing the saiddi-(p-aminoaryl) alkane together with at least 6 mols of hydrogen per mol of aryl compound over a ruthenium dioxide 1102) catalyst at a temperaturewithin the range of to 180 C. and 'at superatmospheric pressure. Preferably, the pressures eme ployed are in; excess of 50 atmospheres. Pressures of about 300 atmospheres have been found to .be particularly satisfactory. The preferred temperature range is from to C., the preferred hydrogen concentration is from 50 to 100 mols of hydrogen per mol of aryl compound, and the preferred space velocity is from 0.1 to 0.6 volume of the aryl compound per volume of catalyst per hour. If desired, various volatile organic solvents may be employed. For instance, superior results are obtained when anhydrous dioxane is the solvent and the solution contains from about 5% to about 35% by weight of the aryl compound. a I V According to a preferred embodiment of this invention, the di-(p-aminoaryl) alkane comprocess for pound to which the above-described hydrogenation process is applied is di-(p-aminophenyl) methane and the product obtained is a di-(paminocyclohexyl) methane composition which is liquid at room temperature, i. e. about C.
The process of this invention is unique in that the products resulting therefrom, upon subsequent condensation with adipic acid as well as with sebacic acid, yield polyamideswhich are--- clear, transparent and fusible. Insofar as :we are aware, there is no other practical, direct process which consistently producesdi-(p ami-s noalicyclic) alkanes having these characteristics.- The products obtained heretofore from-the batchwise hydrogenation of the di-(p-aminoaryl) alkanes yielded cloudy,
batchwise processesto v laborious treatments in order-to separate therefrom-the desired geometric isomers.
It i is -not -lrnown with i certainty whythe :continuous -hydrogenationprocess of this invention yieldsodirectly thesehighly valuablev products...
The following simplified diagrams, however. will aid in explaining our theory of the process; The
diagrams show schematically the threepossible stereoisomers which result from .the hydrogen-a1 tion -of di-(p-aminophenyl) -methane. The. long horizontal-lines in .the diagrams-representan.
edge'viewof a cyclohexane residue. 3
11.. Hv 11.. H H N'H 1 CH1] l CH2 Na. Nm- NHi H Cis-cis Gis-trans 1 NHg- H- H NH: l CH1 t H Trans trans- It is our beliefthat' the hydrogenation of the di=(p aminophenyl')' methane results initially in a di= -'(paminocyclohexyl') methane composition consisting principally of the cis-cis and ClS-' trans isomers as shown above. These apparently correspond to the lower-melting isomers which yield the transparent, 'iusible polyamides; Gen-- eraliy' speaking; however; the very same conditions whichfavor the hydrogenation seem; upon more prolonged contactytopromoteisomerizationof: the initial product to the higher-melting- (trans=trans') form: The reason for the success of" the processofthisinvention, therefore; seems to" be that" conditions are employed which particularly favor the hydrogenation step,-andby incorporating these conditions into a continuous process, the: initial hydrogenation products are reinovcd-- fromcontact with the hydrogenatmg environment before 1 appreciable isomeriza'tion can 000111."
of Formula II have generallyv opaque or irrfusible polyamides' when condensed with adipic acid, and in order. to be sure that clear, fusible polyamides'would be obtained, it was necessary to subject the mix- A tures" of diamine isomers resulting from; these:
The following examples will illustrate certain embodiments of'the process ofthis invention and therefrom:
Example de This exampledescribeda con-' tin-nous process for hydrogenating di-(p-aminocertain characteristics of the productsderived phenyl) methane -to di-(p aminocyclohexyl) methane. The starting material may be obtained froin'aniline and iormaldehydeby a condensation reaction, followed by purification of the crude material either by a topping process whereby the volatile impurities-are removedor by a complete distillation process. The ei-( -amiuophenyl) methane is dissolved in dioxane to give a solution containing 13% by weight of the diamine, and this solution is mixed at 300 atmospheres pressure with from 50 to mole of hydrogen permolof di-(p-aminophenyl) methane. This mixture is then passed over a catalyst containing ruthenium dioxide (R1102) supported on charcoal-ata space velocity of 0.14 volume of di- (p'-a-minophenyl) methane per volume of cataadded over a '5 minuteperiod. This mixture is allowed to fuseior one hour, after which-it'is cooled and-dissolvedin parts ofdistilled Water." Thissolution-is then poured over-activated charcoal which has previously been-washed with a 10% solution of potassium hydroxide and dried at.ll0? C. for 48 -hours.-- The volume ratio of solution to activated charcoal is about 2:3. The impregnated charcoal is then heated to about 50 C.,' 15 parts of methanol are added, and the composition is dried at 110 C. The resulting catalyst contains about 4.5% by weight of ruthenium dioxide.
Example 3.-.-This example describes a con-- tinuous process: for. preparing ;di-'(p-,aminocyclo-. A solution "is:
hexyl) methane in high yields. prepared by dissolving 13 parts by weight of dis tilled di-(p -aminophenyl) methane in 8'? parts; ofifresh; anhydrous dioxane. obtained by distilla-. tion-rrom sodium. This solution is mixed at1300 atmospheres pressure with from .50. to 100. mols-of' hydrogenpermol of di-(p-aminophenyl) methane-and passed over; a ruthenium dioxideicata lyst prepared according to Example-2. The-space. velocity. is maintained at. about 0.29 volume of. di-(p-aminophenyi) methane pervolume of catae lyst-per hour, and the reaction temperature. over: theacatalyst is: maintained at to Ci.
During a-run of l30hours, the amount of di1-(paminophenyl) methane converted varies from'90 to 95%. and the yields of di-.- (-p:-aminocyclohexyl) methane, based on the .amountof -di-(p-amino-. phenyl) methane, employed; vary-from 65 to The product, upon being purified by dis tillation, is liquid at room temperature and has a refractive index, 11 of from 1.5057 to 1.5061.
Example4.-This example describes the preparation of a polyamide from adipic acid and a di- -(p,-aminocyclohexyl) methane composition prepared according to theprocess of this invention.
700' Parts of distilled di-v (p"an'iinocyclohexyl) methane. obtained according to. Example. 3 are dissolved-in 2760 parts of absolute ethanol, to
whichis added a hot solution of 485 partsaof adipic acid in 1575 parts ofv absolute ethanol.
The solutionis'allowed to cool slowly tov about 6C., and thesalt, which precipitates in-ayield of about .92 to, 99%, is washed with absolute: ethanoland dried. This salt is converted. tothe corresponding poly'amide by heatin in an autoclave under a nitrogen atmosphere. During the early heating, the autoclave is maintained under a pressure of about 250 pounds per'square inch but asthetempcrature-is raised to 306 C. the
pressure is gradually lowered to about atmospheric. Upon cooling, a clear, transparent polyamide is obtained possessing a softening point of 238 C.
While this invention has been illustrated with particular reference to the hydrogenation of di- (p-aminophenyl) methane, it is to be understood that the process may be applied to any of the compounds having the hereinbefore defined general Formula II. Included among examples of said compounds are: p,p-diaminoditolylmethane, p,p' diaminodianisylmethane, p,p' diaminodiphenylmethylmethane, and di-(p-aminophenyl) ethane, to mention only a few.
The temperature range within which the process of this invention is carried out appears to be critical. At temperatures below about 130 C., the conversion of the aryl compounds are so low as to be impractical, whereas at temperatures above about 180 C., the concentration of highermelting( trans-trans) isomers in the product becomes so great that clear, fusible, polyamides with adipic acid can no longer be obtained therefrom. In the case of di-(p-aminocyclohexyl) methane, for instance, experiments show that transparent, fusible polyamides with adipic acid can only be produced when the content of transtrans isomer is below about 2.5% to 27%, the exact figure depending upon the relative proportions of the cis-cis and cis-trans isomers present.
The catalysts which are useful in the process of this invention are those comprising ruthenium dioxide. If desired, promoters or extenders may be employed, including, for instance, other forms of ruthenium such as sodium or potassium ruthenate. Catalyst supports which may be employed include those known in the art, such as charcoal, activated carbon, silica gel, alumina, kieselguhr, pumice, the various clays, and the like. The apparatus in which the process is carried out may be so designed that the reactants flow over the catalyst in any suitable direction including upwardly, downwardly, horizontally, etc.
Solvents which may be useful in carrying out the process of this invention include, for instance, dioxane; dioxolane; the lower alcohols such as methanol, ethanol and isopropanol; various ethers, particularly those boiling below about 100 C. such as dimethyl, diethyl and diisopropyl ether; ammonia; cyclohexane; and other volatile organic solvents. Ammonia, besides serving as a solvent, may also be useful in suppressing undesired side reactions such as deamination or the formation of non-volatile polyamines.
The products obtained according to the process of this invention are useful in the preparation of dye intermediates, germicides, surface active agents, pharmaceuticals, corrosion inhibitors, and rubber chemicals. Their outstanding characteristic, however, is that they are capable of being condensed with dibasic acids, such as adipic acid or sebasic acid, to yield clear, transparent, fusible polyamides.
Since many different embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that we do not limit ourselves except as defined in the appended claims.
1. A process for preparing a di(p-aminocyclohexyl) methane composition by hydrogenating di-(p-aminophenyl) methane, which process comprises continuously passing the said di-(paminophenyl) methane together with at least 6 mols of hydrogen per mol of di- (p-aminophenyl) methane over a ruthenium dioxide catalyst at a temperature Within the range of to 180 C. and at superatmospheric pressure.
2. A process according to claim 1 in which the pressure employed is about 300 atmospheres.
3. A process according to claim 1 in which the temperature is within the range of to C.
4. A process according to claim 1 in which there is employed from 50 to 100 mols of hydrogen per mol of di-(p-aminophenyl) methane.
5. A process according to claim 1 in which the di-(p-aminophenyl) methane is passed over the catalyst at a space velocity of from 0.1 to
0.6 volume of di-(p-aminophenyl) methane per volume of catalyst per hou 6. A process according to claim 1 in which the di-(p-aminophenyl) methane is passed over the catalyst in the form of a solution containing from 5% to 35% by weight of di-(p-aminophenyl) methane and the solvent employed is anhydrous dioxane.
- 7. A process for preparing a di-(p-amirm cyclohexyl) methane composition by hydro genating di-(p-aminophenyl) methane, which process comprises forming a solution of di-(paminophenyl) methane in dioxane, said solution containing from 5% to 35% by weight of di-(p-aminophenyl) methane, and continuously passing said solution together with from 50 to 100 mols of hydrogen per mol of di-(p-aminophenyl) methane over a ruthenium dioxide catalyst at a temperature Within the range of 140 to 160 C., at a pressure in excess of 50 atmospheres, and at a space velocity of from 0.1 to 0.6 volume of di-(p-aminophenyl) methane per volume of catalyst per hour.
8. In a process for preparing di-(p-aminocyclohexyl) methane which comprises hydrogenating di-(p-aminophenyl) methane at superatmospheric pressure in the presence of a ruthenium dioxide catalyst and, in the presence of at least six mols of hydrogen per mol of di- (p-aminophenyl) methane, the improvement which comprises passing the di-(p-aminophenyl) methane continuously over the catalyst at a space velocity of from 0.1 to 0.6 volume of di-(p-aminophenyl) methane per volume of catalyst per hour and maintaining the reaction temperature within the range of 130 to C.
ARCHIE E. BARKDOLL. CLARENCE D. BELL. ELBRIDGE R. GRAEF.
REFERENCES CITED The following references are of record in the file of this patent:
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