BE642187A - - Google Patents

Description

       

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 EMI1.1
 



  For t Improvements in the purification of amihoop in particular of hexamthy19ne-dlamin.



  The present invention relates to a method of manufacturing
 EMI1.2
 cation of amines, in particular of high puxated hexamethylenediamine. Hexanethylenediamine is now a well known compound which can be very conveniently prepared on an industrial scale by the catalytic hydrogenation of adiponitrile to presence of ammonia.

   We mainly use
 EMI1.3
 hexamthylene.diamine to condense it with diacids in order to obtain polyamides and in the manufacture of these polyamides one obtains important advantages when one makes

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 first react the diamine with a quantity
 EMI2.1
 equivalent of a dicarboxylic acid so as to "form a salt using a solvent such as water, methanol or ethanol according to well-known techniques. The salt thus prepared is then subsequently converted into a polyamide.



   There are many known methods of preparing
 EMI2.2
 hexamethylone-diamine and these methods are employed in the industry but none of them gives a hexamethylenediamine free of side products or the like ...



  It is therefore generally necessary to purify the crude hexamethylenediamine thus produced afterwards if one wishes to obtain a product exhibiting the high degree of purity required when the hexamethylenediamine is to be processed industrially, in the final aim of producing commercial articles. ! - sands. This is particularly so, for example, in! the case of polyamides prepared by reaction of hexame
 EMI2.3
 thylnc-dibm1n with adipic acid and which are used in many end products.



  The use of poorly purified hexamethylene diamine in the manufacture of hexamethylene dipamide causes lowering of the molecular weight, gives a polymer having poor characteristics in terms of color and dyeability. , and affects various other physical and chemical properties
 EMI2.4
 a polymer or products made from it. Thus, for example, in the textile field where polyhexamethylene adipamide is extensively titilized to manufacture filaments and fibers, the use of a poorly purified hexa-ethylene-d1amine leads to filaments and

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 fibers that are not very resistant or have coloring or color characteristics that do not meet strict textile standards.



   A commonly and widely used process in industry for making hexamethylene diamine is to hydrogenate adiponitrile in the presence of a catalyst such as cobalt. This process is generally carried out on a continuous basis by passing hydrogen and adiponitrile over or through a catalyst under conditions of elevated temperature and pressure. Liquid ammonia is added to absorb the heat of the exothermic reaction and limit the formation of unwanted side products.

   The crude product, once formed, can be freed of unwanted side products by passing it through a series of distillation apparatus by means of chemical treatments or by a combination of these two kinds of purification methods *
It is well known that one of the main impurities, dissolved ammonia, cannot be effectively removed by fractional distillation operations alone.



  Ammonia is generally generated under the effect of the heat necessary for the fractional distillation of hexamethylenediamine and this ammonia redissolves in the condensed hoxamzthylene diamine vapors. Therefore, it is often not possible to reduce the concentration of ammonia in purified hexamethylene diamine below 100 to 300 percent. p.m. approx. This ammonia remaining in the refined hexamzthylene diamine poses an undeniable problem in the manufacture of polyamides. -

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 EMI4.1
 It is also known that even after having been subjected to a series of distillations to purify it, hexamethylenodimine still contains undesirable impurities.

   These impurities are believed to have formed both during the manufacture of hexamethylno-diamino and during its purification. The exact nature of these impurities is not known, but extensive research has led to the conclusion that they are mainly amino-
 EMI4.2
 hexyl, dne.imi.np ot do condensation products of this imine on it..mOrne and with hexamethylenediamine as well as compounds of other types. These impurities can be referred to in a general way as "impurities reducible to the polar grapho" since they give rise to unsaturated bonds reduced to the polorograph and this is how these impurities * will be designated in the following.



   The following equations represent the reactions
 EMI4.3
 reversible compounds of these types in hexamdthylbne- diamine,

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 Reversible reactions of raducible compounds with polarogrophn in hexamzthylene diamine.
 EMI5.1
 



   In addition to the preceding reactions, the amine-hexylene-imine probably undergoes aldol-type condensation which gives a complex mixture. The following equations are produced by the following equations.

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 EMI6.1
 
 EMI6.2
 It is clearly seen that the compound cos give rise to unsaturated bonds and are reducible at the polar graph. They are all reduced by the polarograph to potentials between 1.3 and 1.5 volts. There is therefore a real need in industry for a purification process.
 EMI6.3
 % cI4 l'lh.'xr: t'.lôthylùn0 ... dim: lino with a dogré ##. #. .- #. ##. such that impurities are completely removed or all
 EMI6.4
 at least:, mn's negligible quantities)) '.



  A subject of the present invention is therefore a 0mQlior process for the purification of hcxamthylbn.-d1am1nlt on nzrticuliqr in order to eliminate all or most of it, the infnmciinc and the impurities reducible to polarography, this process being particularly applicable to takes care of the final stage of the refined.



   To achieve this object, in accordance with this
 EMI6.5
 invention, contacting liquid lthext'm4thyl'no-diamino containing dissolved ammonia with an inert gas and carbon dioxide
 EMI6.6
 Any gas which is inert with respect to the hexamethylene diamine lipid under the conditions of the contacting operation is suitable and as examples of suitable inert gases there may be mentioned, among others, nitrogen, air. free of carbon dioxide, and the product of gas combustion
 EMI6.7
 methane will be removed from carbon dioxide The inert gas is carbon dioxide can be mixed or not mixed before

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 EMI7.1
 However, it is preferable that the liquid hexamethylene-diamine are contacted simultaneously with the inert gas and carbon dioxide.



   The amount of inert gas required for the operation varies depending on the amount of ammonia dissolved in hexamz-, is
 EMI7.2
 Cthyleno-diamino liquid but / in general between 62.5 cm3 and 935 dm3, preferably between 6.25 and 125 diz, per kuy of liquid hexamethylenediamine.



  The quantity of carbon dioxide required & 1 op. ration may be between 3i, 2 and 625 cc, preferably between 47.5 and 156 cm ', per kg of hexamethylenediamine subjected to the treatment
The method used to make the contact can be any of the many well known means which
 EMI7.3
 are suitable for the hoxamthyleno-diamina purifier which is in the liquid form and which allows to ensure an intimate and complete mixture of the gas mixture inert gas +
 EMI7.4
 carbon dioxide with hexamethylene diamine to be purified.



  A convenient method is to bubble the gas mixture through liquid hexethylenediamine. No particular model or form of device is necessary for this, and one can choose the device which best suits the installation considered.



   A very satisfying process and even more
 EMI7.5
 economical than the bnrbots7ce gas, is to contact the hexnm6thylQn-dimino with a mixture of inert gas and carbon dioxide while it is fractionated in a distillation column. In this case, the quantities of inert gas and carbon dioxide required to remove the ammonia and remove or remove the impurities.

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 Reducible polarographs vary not only with the amount of ammonia dissolved in the particular amount of hexamzthylenediamine but also with the reflux rate at which the fractional distillation is carried out and the total flow rate of the hexamzthylene diamine.

   It is obvious that the quantities of inert gas and carbon dioxide introduced into the distillation column must be kept at the minimum values allowing the reduction or the total elimination of the ammonia and of the impurities which can be reduced by polarography without the the presence of these gases decreases the efficiency of the fractionating column or causes too much entrainment and losses of hexamzthylene-diamine by dilution.



   The point of introduction of inert gas and carbon dioxide into the fractionation column assembly and associated condenser (s) is not critical. / Inert gas and carbon dioxide can be introduced. at the bottom of the column, any point along the side of the column, at its top or at the inlet of the condenser or one of the condensers associated with the column, nvoc dos equivalent results The efficiency of the column is not diminished when the inert gas is introduced at the bottom or near the bottom of the column and, moreover, the introduction of the inert gas and carbon dioxide the entry of the or a conduction does not lead to a reduction or a reduction. Less removal of ammonia and polorograph reducible impurities.



   The process of the invention can be carried out in general in the last distillation operation of a purification treatment of hexamethylene diamine.

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 in fact its application before this step would not give appreciable results due to the tendency of the hexmamzthylene diamine on reflux to give birth to new amounts of ammonia and impurities which can be reduced by the pelarograph.

   It is obvious that the invention can be carried out in the last fractional distillation column of a process for the purification of hexamethylenediamine, continuous or discontinuous, whatever the number of previous purification operations that includes the process,
It is also evident that no precaution is to be taken to rid the hexamzthylenediamine of the water since all of the water will have been eliminated in the nnterieur stages of the purification.

   Those skilled in the art will readily understand that highly concentrated solutions of hexamethylenediamine and water cannot be subjected to the removal of ammonia and reducible impurities by the polarograph, probably due to the very high solubility of the gas. ammonia and water, however, the Applicant has found that if the inert gas and carbon dioxide were saturated with water, this had practically no influence on the efficiency of the process of the invention, therefore. it is not necessary to take care that the inert gas and the carbon dioxide are free from water vapor.

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   The following example illustrates the invention without limiting its scope in any way: EXAMPLE:
A continuous industrial hexamethylenediamine purification device comprising a primary column, an intermediate column) a purification column and a refining column, is continuously fed with crude hexamethylenediamine preheated to 125 Ci. The temperature at the base of the primary column is approximately 200 C, the temperature at its top being approximately 100 C. Ammonia ot low boiling point substances,

   such as water and hexamethylenediamine exit at the top of this column to go to a condenser where ammonia is recovered and low boiling substances condensed and discharged. The bottoms of this primary column are introduced into the intermediate column connected in series to the purification column; in these two columns, a head temperature of 110 to 140 ° C. and a pressure of 150 to 200 mm of mercury is maintained.



  A portion of the hexamethylene diamine which contains a part of the 1,2-diaminocyclohexane present in the crude material is taken as a distillate and introduced into the scrub column. The bottoms of the intermediate column which contain relatively pure hexamethylene diamine are introduced directly into the refining column where a head temperature of 113 ° C. and a pressure of 42 mm of mercury is maintained. purification, the hexamethylene-dianino is separated from the 1,2-diamino-cyclohexane by combining the 1,

  2-diamino-cyclohexane in the distillate of this column. The bottoms of the stripping column

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 are returned in the middle column for y
 EMI11.1
 be redistilleda, In the refining column, the hexamethylenediamine distills at the top of the column to condense in a condenser, a portion being returned to the top of the refining column as
 EMI11.2
 reflux and the remainder being withdrawn as hexamethylene. refined diamine. Table 1 below gives the average results of the analyzes carried out on the product introduced into the refining apparatus, on the refining bottoms and on the refined product in order to assay therein 1 ammonia and the reducible impurities with the polarograph.

   The figures shown in this table express the numbers of molee
 EMI11.3
 of impurities per million moles of hexamethylene diamine unless otherwise indicated TABLE
 EMI11.4
 
<tb> Ammonia <SEP> Impurities <SEP> reducti-
<tb>
 
 EMI11.5
 polarographa bles
 EMI11.6
 
<tb> Product <SEP> introduced <SEP> - <SEP> 4.233
<tb>
<tb> Queues <SEP> of <SEP> refining <SEP> - <SEP> 15.368
<tb>
 
 EMI11.7
 Hexamethylenediamine
 EMI11.8
 
<tb> refined <SEP> 183 <SEP> 843
<tb>
 
The evaluations of the impurities reducible with the polarographo are made on a polarograph & mercury drop electrode, at a potential of 1.3 to 1.5 volts
 EMI11.9
 calculated for heptaldiyde,

   1 molo do the latter corres-! laying down at 1 mole of impurity reducible with polarographs
Then a mixture of an inert gas, namely nitrogen, and carbon dioxide is introduced at a point near the base of the refining column; the nitrogen being introduced at a rate of 7.5 dm3 per kilog;
 EMI11.10
 of hexamethylnoMdiamino and carbon dioxide at a flow

 <Desc / Clms Page number 12>

 
 EMI12.1
 of 2y CM3 per kilog of purified hoxamethylenediamine.



    We know the beneficial effect of nitrogen on the reduction
 EMI12.2
 do the ammonia content; also is carried out a continuous test during which one introduces intermittently in the column of refining of carbon dioxide with nitrogen * The results of the determinations of ammonia and dos impurities
 EMI12.3
 reducible with the polarograph in 1 hexamethylone-dlamine purified during this continuous test over a period of 6 days) avoc and without addition of carbon dioxide to
 EMI12.4
 nitrogen, are given in Table 2 01-40'801.8.

   All concentrations of ammonia and polarograph-reducible impurities are expressed in moles per million
 EMI12.5
 moles of purified hoxamethylenediamine, unless otherwise indicated, TABLE 2
 EMI12.6
 Refined ilhoxamethylene-diamine assays.

   Date Time Nli POI deduction impulse, Inort gas used
 EMI12.7
 
<tb> 1st <SEP> .day <SEP> 0800 <SEP> 44 <SEP> 87 <SEP> Without <SEP> carbon dioxide <SEP>
<tb>
<tb>
<tb> 1000 <SEP> 72 <SEP> - <SEP> "
<tb>
<tb>
<tb> 1200 <SEP> 84 <SEP> 139 <SEP> "
<tb>
<tb>
<tb> 2115 <SEP> 28 <SEP> 27 <SEP> With <SEP> carbon dioxide <SEP>
<tb>
<tb>
<tb> 2400 <SEP> 28 <SEP> 25 <SEP> "
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> 2nd <SEP> day <SEP> 0400 <SEP> 17 <SEP> 24 <SEP> "
<tb>
<tb>
<tb> 0800 <SEP> 18 <SEP> 27 <SEP> "
<tb>
<tb>
<tb> 1200 <SEP> 4 <SEP> 19 <SEP> "
<tb>
<tb>
<tb>
<tb> 1600 <SEP> 23 <SEP> 28 <SEP> "
<tb>
<tb>
<tb> 2000 <SEP> 28 <SEP> 25 <SEP> "
<tb>
<tb>
<tb>
<tb> 2400 <SEP> 25 <SEP> 24 <SEP> "
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> 3rd <SEP> day <SEP> 0800 <SEP> 19 <SEP> 98 <SEP> Without <SEP> carbon dioxide <SEP>
<tb>
<tb>
<tb>
<tb> 1200 <SEP> 19 <SEP> 78 <SEP> "
<tb>

  
<tb>
<tb> 1500 <SEP> 19 <SEP> 85 <SEP> "
<tb>
<tb>
<tb> 1400 <SEP> 16 <SEP> 50 <SEP> With <SEP> carbon dioxide <SEP>
<tb>
<tb>
<tb> 1600 <SEP> 19 <SEP> 27 <SEP> "
<tb>
<tb>
<tb>
<tb> 1800 <SEP> 18 <SEP> 61 <SEP> Without <SEP> carbon dioxide <SEP>
<tb>
<tb>
<tb> 2000 <SEP> 18 <SEP> 78 <SEP> "
<tb>
<tb>
<tb> 2400 <SEP> 16 <SEP> 119 <SEP> "
<tb>
 

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 T A B L E A U 2 (continued)
 EMI13.1
 
<tb> Date <SEP> Time <SEP> NH3 <SEP> Imp, Red, Pel,

   <SEP> Inert <SEP> gas <SEP> used
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> 4th <SEP> day <SEP> 0400 <SEP> 13 <SEP> 140 <SEP> Without <SEP> carbon dioxide <SEP>
<tb>
<tb>
<tb>
<tb> 0800 <SEP> 12 <SEP> 120 <SEP> "
<tb>
<tb>
<tb>
<tb> 0900 <SEP> - <SEP> 152 <SEP> "
<tb>
<tb>
<tb>
<tb>
<tb> 1200 <SEP> 9 <SEP> 31 <SEP> With <SEP> carbon dioxide <SEP>
<tb>
<tb>
<tb>
<tb> 1300 <SEP> - <SEP> 28 <SEP> "
<tb>
<tb>
<tb>
<tb> 1600 <SEP> 9 <SEP> 30
<tb>
<tb>
<tb>
<tb>
<tb> 2000 <SEP> 11 <SEP> 121 <SEP> Without <SEP> carbon dioxide <SEP>
<tb>
<tb>
<tb>
<tb>
<tb> 2400 <SEP> 12 <SEP> 33 <SEP> With <SEP> carbon dioxide <SEP>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> 5th <SEP> day <SEP> 0408 <SEP> 12 <SEP> 45
<tb>
<tb>
<tb>
<tb>
<tb> 0800 <SEP> 9 <SEP> 40
<tb>
<tb>
<tb>
<tb> 1200 <SEP> 10 <SEP> 48 <SEP> "
<tb>
<tb>
<tb>
<tb> 1600 <SEP> 10 <SEP>

  50
<tb>
<tb>
<tb>
<tb>
<tb> 2000 <SEP> 12 <SEP> 127 <SEP> Without <SEP> carbon dioxide <SEP>
<tb>
<tb>
<tb>
<tb>
<tb> 2400 <SEP> 12 <SEP> 42 <SEP> With <SEP> carbon dioxide <SEP>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> 6th <SEP> day <SEP> 0400 <SEP> 11 <SEP> 30 <SEP> "
<tb>
<tb>
<tb>
<tb>
<tb> 0800 <SEP> 12 <SEP> 100 <SEP> Without <SEP> carbon dioxide <SEP>
<tb>
<tb>
<tb>
<tb> 1000- <SEP> 112 <SEP> "
<tb>
<tb>
<tb>
<tb> 1200 <SEP> 12 <SEP> 129
<tb>
<tb>
<tb>
<tb> 1400 <SEP> 157 <SEP> "
<tb>
<tb>
<tb>
<tb>
<tb> 1600 <SEP> 10 <SEP> 34 <SEP> With <SEP> carbon dioxide <SEP>
<tb>
<tb>
<tb>
<tb> 2000 <SEP> 10 <SEP> 81 <SEP> Sana <SEP> carbon dioxide <SEP>
<tb>
<tb>
<tb>
<tb> 2400 <SEP> 14 <SEP> 121 <SEP> "
<tb>
<tb>
<tb>
<tb>
<tb> 0400 <SEP> 12 <SEP> 20 <SEP> With <SEP> carbon dioxide <SEP>.
<tb>
 



   The evaluations of the quantities of impurities reducible with a polarograph are carried out as above,
Although the nature of the reaction or reactions which take place in the process of the invention is not known with certainty, the preceding results clearly show the synergistic effect which results from the use of a combination of carbon dioxide and gas. an inert gas in the process according to the invention; this results in a reduction of several times the content of dissolved ammonia and of impurities reducible by polarography of hexamethylenediamine.

   The advantages of the process are all the more evident since it is possible to obtain a hexamethylenediamine of markedly improved purity, both a substantial and costly change in the existing devices for the purification of hexamethylenediamine and

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 Ammonia and polar reducible impurities contents
 EMI14.1
 rosraph of purified huxl1mÓthylôno-d1amina can be reduced to specific yield values which are acceptable because of the inconvenience of the screening process.
 EMI14.2
 cation back polyamides * The process of the invention therefore provides a high purity hexamethylenediamine practically fresh blood of additional manufacture and in most cases without any chaugomont in

    the appa-
 EMI14.3
 rcill,; lGo..LIeD so will account for many other advantages of the invention.



   It is understood that modifications can
 EMI14.4
 Ûtro contributiondoo to the embodiments which have just been described in particular by substitution of equivalent technical means cana which one aorto for cola du
 EMI14.5
 part of the X'Ó: 3unto invontion.


    

Claims (1)

CLAIMS EMI15.1 't. A method of purifying hexamethylenediamine by contacting hexamethylenediamino containing dissolved ammonia and polarograph reducible impurities with both carbon dioxide and an inert gas. -to said EMI15.2 hoxamethylbne-diamino. 2.- The method of claim 1, wherein an amount of inert gas is used comprised EMI15.3 between 62) 5 OM3 and 935 dm3 per kg of h, xam6ethyl'ue-diamine subjected to the treatment. 3.- The process of claim 1, wherein the amount of carbon dioxide used is included * EMI15.4 between 31.2 and 6, because per kg of hoxam'th11ne-41..1n. processed $ 4.- The process of claim 1, in EMI15.5 in which is used, per kg of hexamethylene '"diajaine treated, a quantity of inort gas v1a-v18 of hexa mothyleno-diamine of between 62.5 car and z5 dz *, t a quantity of do / el Alaz" "dr 'Don1èuo oompriao between 3', and 625 on1 5 <- The process of claim 1 wherein the quantity of inorto gas via the said hexa * mdthylbno-diamine used is between G, 23 and 125 cm per kg of 'hoxamethylenCd1amlne'm18o involved. 6.- The process of claim 1, wherein the amount of carbon dioxide used is EMI15.6 between 47.5 ot 156 em3 per kg of hoxam6tb11.ne-d1aaiu9 treated. <Desc / Clms Page number 16> EMI16.1 7. "The process of 4 rovon1Qation '!, In which the quantity of inert gas via-a-lifetime Se said hoxamethene-diam1n & is compressed between 6, and 125 dz3 per kg of thexamethene-diamino involved and the quantity of carbon dioxide is between 47 and 156 om 'per kg of hoxamthylenodiamine involved # 3, The process of claim 1, wherein said gas inert to the hoxamthylenodiaialno comprises at least 1 'donate gas following i nitrogen EMI16.2 carbon dioxide gas is oxidized by the combustion of methane from which the carbon dioxide has been removed. EMI16.3 In the continuous process of purification of thoxamethylene diamine in which the hexanethyleno- EMI16.4 diamino in a distillation zone where one condenses EMI16.5 the resulting hexaethyleno-diattino vapors we EMI16.6 form of a final product, processing according to EMI16.7 which is called the hoxamth11no-41amine with both carbon dioxide and an inert gas vi.-to-v1. of said hexamethylene diaminoe