CA1065538A - Method of producing linear plyethylenimine - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
Ethylenimine or oligomers thereof are polymerized in the presence of various cationic catalysts (taken in an amount of from 0.1 to 1.0 mol.% per each elementary unit) in mass at a temperature of from 40° to 55°C till about 10-25% conversion ratio of the ethylenimine cycles is reached, thereafter the polymerization process is inhibited with an alkali, the unused monomer (or oligomer) is distilled off, water is added in an amount of from 0.3 to 3.5 parts per each part of the oligomeric residue, and the polymerization process is completed at a temperature of from 5° to 25°C. The precipitate of the linear polyethylenimine crystallohydrate is separated, washed with water and dehydrated by way of drying in vacuum at a temperature within the range of from 40° to 100°C.

Description

~;)655;~8 ~ he present invention relates to methods of' pro~ucing ~inaar polyet~ylenimine isomer (PEI). PEI is a vexsatile addi-tiv~ (adhesive, chel~te-~'orming agent, ion-exchange and catio-~ic flocculant~ promoti~g ~arious bechnological processes and impro~ing quality o~ the production. made such as paper and cardboard, rubber a~d textile articles.
Known in the art is a method of producing linear PEI
(IPEI) by wa~ of an isomerization polymerization o~ a ~ive-~membercd nitrogen-contalning ~eterocyclic compound suc~ as oxazoline-2 in aprotic. solvents or i~ mass ln the presenc~ of cationic cataIysts such as organic or mineral acids, methyl ~:
iodide, boron ~rifluoride etherate or antimon~ p~ntafluoride~
stherate to obtain as a result, linear poly(~-acylethylenimi-~nes) which are ~urther subjected to hydrol~sis to give IPEI~
is prior art met~od has a:disad~antage residing in~:the ;~
n~cessity o~ preliminar~ preparing the starting:oxazoline-2 whic~ i~ prepared~rom monoethanol~mino in three:stag~3 with a yield of about~4~%0 ~nother disadvant~ge of this prior ar~
metho~ rasid~s in the necessity o~ a ~pecial puri~ication of the:st æting monomer, i.e. o~azoline-2 (re-distillatlon, cr~
stallization, dehydration by~eans of molecular sie~es).`~More-o~er, i~ should be noted that e~en wi-th a hi~h-purity oxazoli-ne and a fresh catalyst, i~eO boro~ trifluoride et~erate~pre~
pared directly ~e~ore ~e experiment the polymerization o~
oxazoline-2 i~ ~ solution o~ dimethyl~ormamide or ac:etonitrile proceeds with a 70% yield (as calculated for the monomer~ and :

, ::

~OG5538 results in the production of a ~elatively low-molecular poly(N-formylethylenimine~. To conyext the latter into LPEI, the reaction o~ alkaline hydrolysis is employed which results in a 85% yield and, of course, features common disadvantages of macromolecular reactions, viz. low rate and incomplete conversion of functional groups in the polymer. Therefore, said prior art method is rather time-consuming (consists of 5 stages) and results in the production of a low-molecular LPEI (mol. weight of about 2,800) with irregular structure (due to incomplete hydrol-ysis) and yield o~ about 24~ as calculated in the monoethanolamineentered in the reaction.
It is an object of the present invention to provide a method of producing linear polyethyleneimine which would be simplified in respect of the processing.
It is another object of thepresent invention to provide a process which would enable the production of the desired product with a higher molecular weight and more uniform com-position.
These and other objects are accomplished by that, in -accordance with the present invention, the mass polymerization of ethyleneimine or its oligomers, i.e. dimer, trimer or linear tetramer taken individually or in a mixture is e~fected at a temperature within the ran~e of from 40 to 55C in the presence of cationic catalysts such as mineral acids (hydrochloric, ~L~6553~3 sulphuric or chloric acld ammonium salts o~ hyd~ochloric, sulphuric, or chloric acid, dichlo~opropane or dichloropropanol taken in an amount of f rom O .1 to 1.0 mol.% per each elementary unit; said mass polymerization is conducted until a conversion ratio of ethylene imine cycles of 10 to 25~ is reached; then the resulting polymerization mixture is cooled to a temperature ranging from 5 to 25C and added with water at a weight ratio of from 1:2.5 to 2.5:1 and the mixture is maintained at a tempera-ture within the range of from 5 to 25C until the polymerization is completed to give a heterogeneous polymerization mixture con-taining linear polyethyleneimine crystallohydrate in the form of a precipitate which is then separated from the heterogeneous poly-merization mixture and dehydrated by drying in vacuum at a temperature within the range of from 40 to lOO~C.
Ethyleneimine employed in this method as the starting product is a commercially available technical monomer. The polymerization of ethyleneimine or oligomers thereof to LPEI
simple as to its technological scheme ana appareillage and may be performed using conventional plants for the production of branched PEI (BPEI).
Corresponding intentional change of conditions of the polymeriæation process ~the use of water and low temperatures within the range of from S to 25C) makes it possible to eliminate, at the polymerization stage, blocking of imine groups ~5S3~

o~ the propagating polymeric chains by co~alent-bonded proto-ctlve (ac~l) groups which is characteristic ~or t~e prior ark me~od and to replace said g.roups ~ith water molecules bondsd to imino groups by means o~ ~ydrogen ~onds. During dehydration of IPEI this water i5 completely removed ~rom the polgmer to gi~e, as a result, the desired prodllct with a uni~orm composi-tion.
~ he nature and ~mount of the catalysts employed in the m~thod of the pres~ inventio~ make it possible to control the molecular weigh~ o~ the resulting pol~mer ~ithin a widb range (~rom 1,000 to 40,000).
~ he me~hod o~ the present i~ention makes it pos~ible to produce IææI wit~ a maximum yield of about 55% as calculatsd~
on the startin~ heterocyclic compou~d consumed in the reactio~
~he remaining por~ion o~ the starting product is not wa~ted at all; instead9 it is co~verted into a water-soluble BÆI ~hich is o~ a commercial in~erest ~nd whic~ may be easily s~parated ~rom water-i~soluble IæEI. : :
~ o accelerate the polymerizatîon process, it is ad~isable to add, into the polymerization mixtuxe cooled to 5-25~, along with watex, a cationic catalyst - hydrochloric9 sulphur-:
ic or chlo~ic acid or ammonium salt o~ h~droc~loric or chlorlo acid~ an amount ra~ging ~rom 1 to 5 mol.% per each ele~en-tary unit.
To increa~e the desired product ~ield3 it is ~dvisable, prior to cooling t~e rsactio~ mi~ture to a temperature o~ ~rom ~6553~3 5 to 25~, to desacti~ate the cationic catalyst with an alkali, to distilleo~ startin~ mo~omer or oligoruer from the reaction mixture and to add, therea~ter, to the poly~nerization mixture cooled to 5 - 25G, alon~ with water, a cationic catalyst -hydrochloric, sulphuric or chloric acid or arn~or~um salt the-reo~ in an amount o~ from 1 to 5 mol~yO per each unit.
~ o the same end, it is ad~isable in order to distill-o~, along with the starting rrlonomer, the dilfler resulting ~rom the mass polymerization~
~ he method of producing LP~I in accordance with the pre~
sent invention may be performed in the manner as ~ollows.
Into a ~lask provide~ with a stirrer eth~lenimine or its oligomers, i.eD dimer, trir~er or linear tetramer taken i`ndivi dually or in a mi~ture, are charged. ~'he ~lask is heated on a water batch to 40G and a cationic catalyst such as hydrochlo-rlc, sulphuric or chloric acid, ammonium chloride, ammoniu~
sulphate or perchlorate, 1~3-dichloropropan-2-ol or dichloro- -propane lS gradually added through the re~lux condenser, ~here- .
with, the ~lask contents is heated, due to the poly~erization heat, to 55C (ethyIone imine boils at this temperature).
After addition of the catalyst the flask contents is stirred~
for additional 0.5 to 10 hours, the ~ernperature being rnaintai-ned within the range o~ from 40 to 55C, 'l1he ~ass poly~eriza~
tion (first stage o~ the polymerization proces3) is disconti-nued when the conversion ratlo o~ ethylenimine cycles in the ~:

l~SS~
resulting polymerization mixture is 10 to 25% which is deter-mined by a re~raction index value o~ the mixture (see Exalrlples hereinbelow). '~'he ~'irst pol~merization stage is directed to accwnulation of oligomeric products neces~ary to perform the second polymerization stage ~i.eO pol,~merization contemplati~g the use o~ water), '~he starting monomer or oligomer, upon completion of the ~`irst polymerization stage9 may be distilled-of~ ~xom the re-sulting polymerization mixture and employed in a new pol~meri-zation cylce. In this case 9 the cationic catal~st i~troduced at the first polymeriæatior- ~tage, prior to the distilling~of~
o~ the starting mono~er or oligomer, should be inactivated by way o~ adding an alkali (such as caus~ic soda or caustic pot-ash) taken preferably in e~cess wi-th respect to the catalyst a~ount used in the ~irst polymerigation stage.
'rO perfo~ the second polymerization stage, the resultin~
polymerizatio~ mixture (with,or without distil~ing-off the starting mo~omer or oli~omer) is cooled to a temperaturq with-in the ragne of from 5 to 25G, added with water at a weight ratio therebetwee~ ranging ~rom 1:2~5 to 2.5:1, wherea~ter the polymerization proce~s is conducted at a temperature o~ f~om 5 to 25C~ lf after the ~irst polymerization stage the ætarting monomer or oligomex has been distille~off and the catalyst has been i~activated, ~he polymeri~ation mixture is added witk a new portion o~ the cationic catalyst - (hydrochloric acid, sulphuric or chloric acid or a~monium salt of hydrochloric acid or chloric acid) in an amoun~ ranging ~rom 1 :~L0~iS53 to 5 mol,% per each elementar~ unit. Said additional amount o~
the catalyst ma~ be introduced into the polymerization mixture directly befor~ or a~ter the additio~ o~ water to the mixture or simultaneously with water. As the second polymerization stage progresses, the polymerization mix*ure hamogeneous at the star* of the process becomes str~ti~ied i~to BPEI or its aqueous solution and Iæ~I crystallohydrate precipitate (i.e., hetero~eneous polymeri ation mixture is formed). Duration o~
the second pol~merization stage a~d the desired product yi~ld depend on the amounts of water and catalyst employed at this stage. ~hus, an increased amou~t of the catalyst results in a hi~her polymerization rate with, however, decreased yield of the de~ired productO When water content in the polymerizati.on mixture is increa~ed? both said parameters (IEEI yield and polymerization rate) reac~ thsir maximal values at a weight ratio between water and bhe polymerization mixture ranging from 1:2.5 to 2~5:1.
~ he end o~ the polymerizatiGn is determined b~ the absenc~
of a colour reactlon o~ ethylenimine cycles wit~ thiourea and sodium nitroprusside ~he procedure is dascribed in ~xample 1 hereinbelow~. On completion of the polymerization process,~ t~e resulti~g heterogeneous pol~merization mixture is separ~ted, by deoantatlon, i~o BPæI or it~ a~ueous solution and ~EEI
crystalloh~drate precipitate~ Sai~ precipitate is 3-4~time~
washsd ~ith~water, t~e precipitate bei~g eparated ~rom ^tho la~t portion o~ the washings ~r centriIugation or filtra~ion9 lQ6553 Remo~al o:~ the hydrate wa~er ~rom LPEI c~stallo~ydrate i~
e~ected by dr~ing in ~acuum (e~g. ~t a residual pros~ure of ~rom 2 to 25 mm Hg) at a te}aperature wit~in the rang~ of from 40 to ~00C.
~ or better understa~ding of th~e present invention t~e ~ollowing Examples illustrating the production o~ linear pol~-ethylenimine are gi~en hereinbelowO
Example 1 250 ml of ethylenimine (207 g) were charged into a flask pxovided with a reYlux condenser, stirrer, theremometer and water bath, heated to 40C and drop wise added, via the re~l~x condenser, with 295 ml (0.5 mol.%) o~ a concentrated hydrochlo-ric acid (speci~ic gravit~ o~ 1.19) ~or 30 minutes under ~tir-riDg. A~ter the catalyst additio~, the ~lask con~ents was stir-~red for additional 4 hours while maintaining the ~lask tempera-ture at 40~C. The mas~ pol~merization (the ~irst polymeriza-tion stage) was discontinued when the con~ersion ratio of eth~lenim1ne c~cles 1~ the re~uIting pol~merization mi~ture reached 25~ ~re~raction index o~ said polymerization mixture ~5 = 1.4410)-~ o e~ect the second polymeriæation stage, t~:Le resultingpolymerization mixture was cooled to 20C, adde~ with 200 ml of ~vater (at a weight :ratio ther~between o~ abou~ 1:1) ~d 13 g ~5 mol~%) OI ammo~ium chloride ~the latter was added portiQn-wise b~ 2-3 g portions so as the pol;ymerization mixture tempe-rature be mai~ained at 20C not mors) and t~e mi~ure was ~ ~' ~ ..

~6S53~3 maintained at 20C until completion of tha polymerization proce~s. ~he end o~ the pol~merization was determined by the absence of a colour reaction o-~ et~ylenimine cycles. ~o thi~
end, a small portio~ o~ the polymeriza-tio~ mixture (2-3 drops) were mixed with 1 ml o~ a 1C~/o thiourea solution in a 5~ aque-ous solution o~ ~drochloric acid~ maintained ~o:r 15 - 20 mi-nutes; the acid was then neutralized wit~ a 10% a~ueous solu-tion of caustic soda added with 1 - 2 drops of a 0.5% a~ueous solution o~ sodium nitroprusside. Lack of crimson colour upo~
the addi-tion of nitroprusside shows that eth~lenimine ~ycles content in the polymerization mix~ure is bslow 0.01%.
As a result, a heterogeneous polymerlzation mixture was obtained which was separated, by decantatio~, into an aqueous BPæI solution and IE$I crystallohydrate precipitate. ~he lat-ter w~s washed wit~ water, centri~uged and dehydrated in a vacuum-drying cabinet (residual pressur~ 3 5 mm Hg) at 60C
~or 20 hours to give 24 g of IPEI (12% of the theore-tical ~ield) with the i~tri~sic viscosit~ in a solution of absol~te ethanol o~ [q]2~hanOl = 0.1 dl/g at 20C and molecular weight o~ 4,5000 ~R spectxum of this samp}e on nuclei 13C consi~ed o~ one sig~al only which evidenced t~at the polymer had a uniform structure~
Dehydration of the BPEI aqueous solution and water wash-i~g~ resulted in 180 g o~ BPEI with the intrinsîc viscosity ` [~J 5 ~; = 0.07 dljg at 25~C in a 0.1N aqueous solution o~
sodium c~loride9 :;:
~ .. ~

J ~;)65538 ~ 10 -Example 2 Mass polymeriæatio~ o~ 500 ml o~ eth~lenimine was per~or-med in accordance with the procedure described in the ~orego-in~ Example 1 in the presance of 1~5 ~ (0~1 mol.%) of 1,3-di-chloropropane-2-ol till a 1C~o co~version ration o~ eth~lenim-ine c~cles in the resulting pol~merizatio~ mix*ure was rea~hed ( ~ 5 of the mixture is 1.4250). ~herea~ter, the polyme~i~ation mixture was cooled to 25C, added with 166 ml o~ water (at the weight ratio betwa0n water and ~he polymerization mixture o~
1:2.5) and polymerized a~ 20-C u~il completio~ of the process whiGh was determined in a manner similar to tha~ described in Example 1 ~erai~before.
~ s a result, a heterogeneous polymerization mixture wa~
obtained which was added wit~ 250 ml o~ water to red~ce BP~I~
~iseo~ity~, whorsa~ter said mixture was separated by decanta-tion intc an aqueous BPEI solution a~d IEEI cr~stallo~ydrate precipitate~ ~he latter was washed with wa-ter, centrifuged~and dehydrated in a vac~u~-drying cabinet (a~ a residual pressure o~ 1-2 mm X~)~'at ths temperature`of 40C to ~ive 37~5 g Q~
, ~
: Iæ~I (9% o~ the t~éoretical yield) with t~e in~rinsio:Yiscosit~
¦~20hanO1 ~ 0.31 dl/g and molecular weight o~ 237500.
Example 3 300 ml of ethylenimine dime~ were polymerized in mass at ;
50C ln t~e presenca of 12 ml (0~5 mol4?0) o~ a 40~0 aqueous solution of c~loric acid ~or 5 ~ours to give a polymerization mixture with a conversio~ ratio o~ eth~lenimi~e cycles o~

10~531~

about 20% (nD5 o~ the mixture was 11,4670). Said pol~meriæation mixture was added wit~ 20 g of siolicl c~ustic soda to inactivako the ca~alyst and the unreacted ~tart;ing dimer waq distilled-off in ~acuum (156 g). ~heroa~ter5 the ~)olymerization mix*ure (120 g) wa~ separa~ed from th~ alkali b~ decan~ation, cool~d to 20C and ~he thu~-cooled mix*ure was ~dded ~ith 300 ml of water (at the weig~t ratio bstween the pol~meriz~tion mi2*ure a~d water of 1:2.5? and 3.5 g o~ amm~ium perchlorate (1.0 mol~%) and.the polymerization was con~inued at 20C till com-pletio~ of the process. ~he resulting ~eteroge~eous mix*ure was treated i~ a manner similar to that descri~ed i~ the ~o-risgoing ~xample 1 to give 60 g of IEEI (t~e yield was 50% a3 calculated on t~e con~rt~d dimar) with the intrinsic viscosi-t~[~j2e~anol = 0.16 dl/g a~d 60 g of BPEI wî~h ~he i~trinsic viscosit~ ¦q~MaCl = 0.15 dl/g.
x~mple 4 500 ml of ethylenimin2 were polymerized in mass at ths temperature of 55:C in the presence of 4.4 ml (0.5 mol.%) o~
a co~centrated h~drochloric acid to obtai~ a pol~merization mixture with the con~orsion ra~io of ethylenimine c~cles of ~0~0 ( ~ 5 o~ the mixture wa~ 1.4380). Said polymerization mix-ture was added with 20 g o~ solid caustic potash to inactivate the ca~alyst and t~e starting unreacted monomer was distilled-~o~`f, ~ollowed by distilling-of~ ethylenimine dimer resulting ~
from the polymerization process (th~ dlmer yi~ld was 100 g or ;
25% of~tha theor~tical value). ~hereafter, the polymerizatlon ~065538 -mixtur~ (150 g) was separa~ed from the alkali. by decantation, cooled to 25C and added with 360 m~. o~ water (at the weight ~atio between wa~er and the polymeri.zation mixture of 2.4:1) and 6 g o~ ammonium perchlorate (1~5 mol.%) an~ the polymeri-za~ion was continued untll co~pletion of the process. The re-sulting heterogeneous pol~merizatio~ mixture was treated in a manner similar to that de~cribed in the foregoing Example 1 to give 18 g of IPEI (~ield Gf 12% as calculated on the con-verted eth~lenimine3 ~aving it~ intrînsic viscosit~ value ~ 1 ethanOl = 0-18 dl/g.
Example 5 800 ml o~ et~lsnimine were polymerized i~ mass at the bempera~ure of 40'C i~ the presence of 10 g o~ a 50% aqueous solution o~ sulphuric acid to obtain a polymerization mix*ure with the oonverslon ratio of ethylenimine c~cles of 10~o (~DS
of ~he mixture was 1.42503. Said polymerization mixtlLre was ~ - , added wit~ 20~ g o~ a solid alkali to inacti~at3 t~e ca~aly~b ~na ~he star~ing unreacted m~nomer waæ distilled o~ hera-a~ter~ t~e~polymerization mixture (1~0 g) was separated ~rom the alkali b~ decanta~io~, cooled to t~s tempera~ure o~ 5C
and added wit~ 450 ml of water ~at the weight ratio b~tween water and bhe polymerization mixtur~ of 2.5:1) and 10 ml (1 mol.~0) of a ~0% aqueous solution o~ c~loric acid and the polymerîzation was continued at this temperature until oomple-tio~ of the process.
.
-:
~ .

~L~)65S3 ~ s a result~ a hetero~eneous polymerization mixture was obtained which was s~parated by decantation into an aqueous ~P~I solution and IP~I crystallohydrat~ precipitate. ~he lat-ter was washed with water, centri~ug;ed and deh~drated in a vacuum-drying cabillet (under a residual pressure of 20 mm Hg~
at the temperature of 100~C to give 40 g-o-~ ~PEI (the yield wa~ 22% of the co~verted eth~lenlmi~e) with the intrinsic ris-y [ ~ ~thanOl ~ 0.21 dl/g and 140 g o~ ~PBI with ~h trinsic ~i~cosity [~25cl = 0.19 dl/go Eæample 6 100 ml o~ ethylenimine trimer were pol~merized i~ mass at the temperature of 40C in the presence o~ 0.85 ml (0.5 mol~%) o~ ~ concentr~ed h~drochloric acid (speci~ic gr~ity o~ 1.19 fo~ 2 hours to obtain a polgm~rization mixture ~ith a conver-sion ratio o~ ethylenimine cycles of about 10% ( ~ 5 of the mi~ure was 1.4815). ~hereafter1 t~e pol~meri~ation mixture was cooled to 20C, added with 150 ml o~ water (a~ the weîght ratio between water a~d the polymerization mixture o~ 1.6:1) and 2.5 g (1 mol.%) o~ ammonium perchlorate, an~ t~ polymeri-zatio~ was con*inu~d at this temperature until co~pletion o~
the process. ~he resulting heterogeneous polymeriæation mix*u-re wa~ trea-ted in a m~x~ler similar to that described i~ the foregoing Exampl~ 1 to gi~e 33 g o~ Iæ~I (the yield was 35%
of t~e theoretical ~alus) ~ith the intrinsic ~iscos~t~
thanol = 0.19 dl/g and 60 8 o-f BPEI with the intrinslc viscosity of ~25aCl = 0.15 dl/g-.

~553~

Example 7 ~ inear ethylenimine tetram~r (50 ml~ was pol~merized i~
mass a~ the te~perature o~ 40~C in the prese~ce of 1.2 g (1.0 mol.%) o~ ammonium perchlorate ~or a period o~ one hour to obtain a polymerization mixture wit~ the con~ersion ra-tio o~ ethylenimine c~cles o~ about 10%o ~n~5 o~ the mixtur~ wa~
1~930). ~herea~ter, the polymerization mixture was cooled to the temperature of 20C, ~ixed with 100 ml o~ water (at the waight ratio between water and t~e polymeriz~tion mixture of

2:~) and mai~tained at t~is temperature until completio~ o~
the polymerization p~oc~ss. ~he resulting heterogeneou~ poly-merizatio~ mixture was treated in a manner similar to that desribed in the foregoing Example 1 to gi~e 26 g o~ IæEI ~the ~ield was 55% o~ the theoretical value) with the intrinsic vis-co~it~3 2thanOl = 0.15 dl/g and 22 g of BPEI wit~ t~e intri~-sic viscoBitYE~3 ~aCl ~ 3 E~ample 8 A mixture o~ dimer, trime~ a~d linear tetramer o~ ethyl-enimine (weight proportions o~ the oligomers being 1:1:1) in the amou~t of 100 g waæ polymerized in mass at the temperature of 40C in tho presence ~ 1 g (1 molr%) o~ ammonium c~loride for a perioa of two hours ~o obtain a polymeri2atio~ mix*ure wit~ t~e`conversion ratio o~ eth~lenimi~e ~Y.cles of 10% ( ~ 5 o~
t~ mix*ure was 1.4820~ ~hereafter,:the polymerization mixtur~
wa~ oooled to 25C, added with 200 ml of water ~at t~e weight :

~C~65S31 .

ratio botween water and the pol~m~rization mixture o~ 2:1) and the polymerization was continued at this temperaturo until completion o~ the process. ~he resulting h~terogeneous polyme-rization mixtura was treated in a ma~ner similar to t~at des-cribed in the ~oregoing Examplo ~ to give ~0 g o~ IæEI ~the yiald is 40% of the theoretical value) with ~he i~brinæic vis-cosity r~]et~anol - 0-16 dl/g a~d 60 g of ~PEI ~it~ the in-trinsic viscosity ~ 25acl = 0.13 dI/g-pl~ 9 500 ml of ethylene imine ~are:polymerized in ~ass at t~etemperature of 40C in the presence o~ ~.4 g (0.135 mol~%)~o~
~ dichloropropa~e for a period o~ about 4 hours to obtain a polymerizatio~ mixture with the conversio~ ra-tio o~ e~ylen!-imino cycles o~10~ 5 o~ the mixture was ~.4250). There-after, t~e polymerizatio~ mixture was cooled to 20C, added with 177 ml of water (ak the weight ratio betwe0.n water and th~ pol~merizatio~ mI~ure of 1:2~3) a~d main~ained at thi ~emperature until completio~ of the pro~oss. ~he resultlng heterogeneous polymerization mixture was treated in a manner similar to that describ0d in. Exampl~ ~ to gi~e 3~ g IæEI (the :
~ield was 7.5% o~ the theoretical value~ with -the intrinsic iscoBity ~] etha~Ol - 0-42 d /g . ~

Claims (4)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A method of producing linear polyethylenimine, compri-sing polymerization of nitrogen-containing heterocyclic com-pounds selected from the group consisting of ethylenimine and oligomers thereof, selected for dimer, trimer and linear tetramer, at a temperature within the range of from 40 to 55°C in the pre-sence of cationic catalysts selected from the group consisting of hydrochloric acid, sulphuric and chloric acid, ammonium salts of hydrochloric acid and chloric acid, dichloropropane and dichloropropanol and taken in an amount ranging from 0.1 to 1.0 mol.% per each elementary unit; said polymerization in mass being conducted until a conversion ratio of ethylenimine cycles of 10 to 25% is reached; thereafter, the resulting po-lymerization mixture is cooled to a temperature within the range of from 5 to 25°C, added with water at a weight ratio between water and the polymerization mixture ranging from 1:2.5 to 2.5:1 and maintained at a temperature within the range of from 5 to 25°C until completion of the polymerization process to obtain a heterogeneous polymerization mixture con-taining linear polyethylenimine crystallohydrate as a precipi-tate; said precipitate is separated from the heterogeneous polymerization mixture and dehydrated by drying in vacuum at a temperature within the range of from 40 to 100°C.

2. A method as claimed in Claim 17 wherein the polymeriza-tion mixture cooled to a temperature of from 5 to 25°C is ad-ded, along with water, with a cationic catalyst selected from the group consisting of hydrochloric acid, sulphuric and chlo-ric acid and ammonium salts of hydrochloric and chloric acids and taken in an amount ranging from 1 to 5 mol.% per each ele-mentary unit.

3. A method as claimed in Claim 19 wherein, prior to cooling the polymerization mixture to a temperature within the range of from 5 to 25°C, the cationic catalyst is inactivated with an alkali, the starting nitrogen-containing heterocyclic compounds are removed from the polymerization mixture by di-stilling-off, whereupon the mixture is cooled to a temperature of from 5 to 25°C and added, along with water, with a cationic catalyst selected from the group consisting of hydrochloric acid, sulphuric and chloric acid and ammonium salts of hydro-chloric and chloric acids and taken in an amount ranging from 1 to 5 mol.% per each elementary unit.

4. A method as claimed in Claim 3, wherein, along with the starting ethylenimine, distilled-off from the polymeriza-tion mixture is also ethylenimine dimer resulting from the mass polymerization.