CA1278638C - Process for continuously removing monomers from an aqueous dispersion of a polymer - Google Patents
Process for continuously removing monomers from an aqueous dispersion of a polymerInfo
- Publication number
- CA1278638C CA1278638C CA000252196A CA252196A CA1278638C CA 1278638 C CA1278638 C CA 1278638C CA 000252196 A CA000252196 A CA 000252196A CA 252196 A CA252196 A CA 252196A CA 1278638 C CA1278638 C CA 1278638C
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- polymer
- vinyl chloride
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D3/00—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
- B01D3/34—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping with one or more auxiliary substances
- B01D3/38—Steam distillation
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F6/00—Post-polymerisation treatments
- C08F6/001—Removal of residual monomers by physical means
- C08F6/003—Removal of residual monomers by physical means from polymer solutions, suspensions, dispersions or emulsions without recovery of the polymer therefrom
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- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Dispersion Chemistry (AREA)
- Health & Medical Sciences (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
- Polymerisation Methods In General (AREA)
Abstract
PROCESS FOR CONTINUOUSLY REMOVING MONOMERS FROM AN
AQUEOUS DISPERSION OF A POLYMER
ABSTRACT OF THE DISCLOSURE:
Monomeric matter is removed from an aqueous disper-sion of a polymer containing at least 50 weight % of po-lymerized vinyl chloride. To this end, the dispersion is introduced into the upper portion of a column provided with sieve plates and contacted therein for 10 seconds up to 20 minutes, under 600 up to 1200 mm Hg, with hot steam at 100 up to 150°C flowing countercurrently with respect to the dispersion. The polymer dispersion so treated is removed from the column base portion; and a vaporous matter mixture issuing at the head of the column is con-densed stagewise so as to recover an aqueous phase and the monomeric matter.
AQUEOUS DISPERSION OF A POLYMER
ABSTRACT OF THE DISCLOSURE:
Monomeric matter is removed from an aqueous disper-sion of a polymer containing at least 50 weight % of po-lymerized vinyl chloride. To this end, the dispersion is introduced into the upper portion of a column provided with sieve plates and contacted therein for 10 seconds up to 20 minutes, under 600 up to 1200 mm Hg, with hot steam at 100 up to 150°C flowing countercurrently with respect to the dispersion. The polymer dispersion so treated is removed from the column base portion; and a vaporous matter mixture issuing at the head of the column is con-densed stagewise so as to recover an aqueous phase and the monomeric matter.
Description
~786~
The p:~es~n-t invention rel~-ltec -to a p:rvc~ss .-for free-ing an aquec,us dispersion of a poly~ner f:rom a monomer p:reent -the:rei.n, the polym~r, which may ~e a homopolyrner, graf-t polymcr or copolyrner, having an ex-trerllely mirlor c~ncerltra-tion of residual rilonomer af-ter purif:icationO
I-t; has long been kno~rn -that aqueous po-ymer disper-; sions can be freed from volatile cons-tituen-ts 'by ~lol.iing an iner-t gas or steam at abo-u-t 60-70C through the dis-persjon, i.e. by subjecting the dispers:ion -to steam di-stilla--tion. ~'his has 'been described in Ge~rman Published Specifica-tion ("Auslegeschri~t~ No. 1,2/-~8,943, and in "Kunststoffe" (1959), volume 49, No. 10, page 499, and also in "Chemical Engineering", March 1972, page 960 :[n those cases in which aqueous polyvinyl chloride suspensions are worked up under -the condi-tions just described, -tne polymer is subsequen-tly dried by means of air~ whereby it is freed from a fur-ther proportion of vinyl chloride, e.g. a`bout 2 weight %, based on the quanti-ty of vinyl chlorlde su'bjected to polymeriza~ti.on7 which is allowed to escape in-to the atmosphere. In other words, the issuing gas contains vinyl chloride in propor-tions which are clearly beyond an accepta'ble emiss.ion limit, namely beyond the limit of 150 mg of vinyl cklo-- ride per cubic meter of issuing gas. In additLon to this, excessive proportions of vinyl chloride go into the was-te water. Despite -this, the final dry polyvinyl chloride still contains several hundred ppm of monomeric vinyl chloride, which is absorbed i:n the polyrner and cannot be - 2 ~
1;~78~8 rernove~rl-there:f:r-(Jm by -the purlfying procedure descri'bed above.
0~l~ o~ the u~es of polyvin~1 chloride sheets i~ in packlng Loocl, wh-ch is hazardou~ inasmuch a~ residual mono~ers con-tail1~d in -the polymer ma-y mi~rat~ i~-to th~?
food, It is -therefore obllga-tory for -th~ dry monomer ccn-taining polyrners -to be subjected to an additional special purifying -treatment.
A process wherein dry polyvinyl chloride made in conven-tion~l manner is freed from resi~ual vinyl chlo-ridej -~hich is embedded or occluded in -the polymer par-ticles, has been 'described in German Published Specifi-cation ("~ffenlegungsschrift") No. 2,331,895~ This pro-cess, which enables polyvinyl chloride to be freed from vinyl chloride and further comonomers, if any, comprises:
heating the polymer to a temperature ranging from i-ts freezing tem'pera-ture to 180C by directly condensing steam -thereonto; maintaining the polymer at that -tempe-rature for the period necessary to free it from the bulk of monomer or monomers therein; and cooling the polymer down to a temperature lower than i-ts freezing point by evaporating the s-team condensed on -the polymer. A pre-ferred embodiment of this process comprises heating -the polymer to a temperature ranging from 80 -to 1~0C and allowlng it to remain a-t that temperature for a period of a'bout 5 minutes up to 2 hours, especially 10 to 60 minutes. Typical of this known process is that the de-gasifica-tion is effec-ted a-t the dew point of wa-ter, as described in -the working Examples of that Specifica-tion.
A disadvan-tage encountered with this earlier pro-786~38 cesx -i~esi(1~s in thC f.lct -t~la-t -the ?o~lymer so plrifled continu s to pr~serlt rela-5ive^1y high proportions o-~ rno-norners. As shown in EY~ar~lp1e 1 of ~erri~an P~blished Spe-cifica-tion ("O1fen]egungsschrift" No. 2~31,89~, the purified po:Lyrner con-tains 3 g (or 3,000 ppm) of residual rr.onorners per kg of oolymer. This known process is effect-ed at ternpera-tures ancl under pressures wh:ich correspond -to the dew poin-t of water under -the conditions seLecte~, which naturally means 'nigh a-nd comrnercial~Ly unat-tractive consump-tion of s-team.
In clear contrast therewi-th, -the present inven-tion - provides a process permitting an a~ueolls polymer dlsper-sion -to be freed from`monomeric mat-ter wi-th the resultan-t formation of a purified product containing a few ppm of residual monomer(s), the purified produc-t presentinO this minor concentration of residual Monorner~s) being obtain-ed much more rapidly than in the prior processes of which we are aware.
The following proper-ties of a vinyl chloride/water/
P01YVinY1 chloride-sys-tem are of importance to the removal of monomeric vinyl chloride from an aqueous polyvinyl chlo-ride dispersion~ and should conveniently be considered in effecting such operation.
a) Bunsen's solubility coefflcient a of vinyl chloride in water, which has the following values at temperatures of from 0.1C up to 100C: -0.1C 2 unit vol.vinyl chloride/uni-t vol. water 20C 1 unit vol.vinyl chloride/uni-t vol. water 35C 5 unit vol.vinyl chloride/unit vol. wa-ter 60C 0.1 unit vol.vinyl chloride/unit vol. water 100C 0 unit vol.vinyl chloride/uni-t vol. water 12~8~3 b) :Bur~,er~'~ ;o'lllbility coeïEicierl-t ~ of v:iny:l ch'loride in c)(lueolll PVC~ is?eL,c,ion containing ,5 we:ight ~6 o, solid ~1'.1 tter, w'n;ch has -the following values:
at; 6C 5 unit vol. -vinyl chloride/uni-t vol. wa-ter 18C 3 uni-t vol. vinyl chloride/unit vol. wa-ter 2~C 2 unit vol~ vinyl chloride/unit vol. wa-ter 5~C 1 unit vol. vinyl chloride/uni-t vol. wa-ter 7~C o.6 uni~t vol. vinyl chloride/uni-t vol. l,Jater 0 C) The solub:ili-ty of vi.nyl chloride in polyvinyl chloride.
The following quanti~t:ies of vinyl chloride have been ~'folmd to be dls~olved a-tl-the'following -temperatures e.g. in polyvinyl chloride having a mean particle size of 60 up -to 120 microns and a ~-value of 70.
- ' At 0C 100 g vinyl chloride/kg polyvinyl chloride 2L~oc '50 g vinyl chloridelkg polyvinyl chloride 40C 24 g vinyl chloride/~g polyvinyl chloride 60C 10 g vin-yl chloride/kg polyvinyl ch]oride 100C 4 g vinyl chloride/kg polyvinyl chloride d) The dis-tribu-tion coefficient of vinyl chloride be-tween water and PVC, which is equal -to abou~t 1:15.
We have now unexpectedly found that -the phase equili-bria commence set-ting within the tempera-ture range of 90C
to 100C at intervals of 10 up to 100 seconds under con-ditions which provide for a very effective exchange of cons-tituents between -the individual phases of the above miY,tures a) c). Temperatures around 100C, are, however, ~o known to irnpair the quali-ty of PVC. To avoid -this, i-t is ~7~6.'38 nect~ 1r~y rO~ -the in.~luence of -tempera-tllre o-n YVC to ~be li1n:L-I;ed -to evera~ n-ilLltcs. In o:rder to e-l~ec-ti-vely re-rno-~e Monome.ri.e matter ,`rolll an aqueouc PVC-dispeLsion at -tempera-ture; within -the rarlge 90 and 100C, i-t is f`inally necessary -to c~stablish condi-t:ions, which p:rovide for an e~fective exchange of cor.~s-ti-tuen-ts and thereby or a compLete setting of the phclse equilibria, and also for -the use o:. a sui-table gas phase enabling the monomeric matter -to b~ removed The process of -rhe presen-t in~en.-tion for removi-ng rnonomeric ma-t-ter from an aqueous dispersion of a polymer con-taining at least 50 ~eight % of polymeri~ed vinyl chlo-ride comprises: introducing the dispersion i.nto -the upper portio.n of a column provided with sie~e plates and con-tac-ting -the dispersion therein for a period of about 10 seconds up -to 20 mi-nu~tes and under a pressure of abou-t 600 up to 1200 mm Hg wlth ho-t steam a-t abou-t 100 up to 150C flowing countercurrently wi-th respec-t to -the disper-sion; removing the po]ymer dispersicn so -treated from the column base portion, and condensing stagewise a vaporous mat-ter mixture issuing at -the head o:- -the column so as to recover an aqueous phase and the monomeric ma-tter~
In accordance wi-th a preferred feature of -the pre-sent Lnven-tion, the aqueous dispersion contains approxi-mately 10 up to 60 welght %, more preferably 25-up -to 40 wcight %, of polymeri^ solids which in turn should preferably con-tain a-t leas-t 85 weight % of polymerized vinyl chloride~ The -term "polymers" as used herein com-prises polyvinyl chloride homopolymers and vinyl chloride copolymers, e.g. copolymers of vinyl chloride wi-th. vinyl 12786;~8 tr-l t~ t i rs cll.o ~dvarlt;ageous for -the polymer ~isper-s:iorl to con-t.1in betli/ee~l a'bou-t 0.2 up to 5 welghl 5b of virly~l, ch'lorid~.
A .~llr-th~r preferred fea-ture of the presen-t process cornp.rises hea-tlllr -the polymer to a -tempera-ture of abou-t 60 up to 90C ancl t;hen introdllcing it into -the colu~n.
~:o n ~c~ cte 6~
The dispersion so prehea-ted is-ee~ R~inslde the column ~ith Ihot si;eam ascending therein~ which prelerably is at a terrlpexature of 100 up -to 150~, a.nd causes a tem-0 pe:ratllre 0.~ 90 Up to 100C to be es-tablished ln the co.Lumn head. The column should preferably be opera-ted uncle:r a p.ressure of 700 up to 1100 mm Hg. A relatively mlnor proportion of steam, equal to 1 up -to 5 weight %
' of water, based on the quanti-ty of d1spersion supplied to the co]umn, escapes at the head of the column. Tha po-lymer dispersion i-tself is generally allowed to rem.1in ln -the column over a period of 0.3 up to 10 minu-tes.
The invention also provldes for the aqueous phase obtained on subjecting the vaporous matter mi~ture issuing overhead to stagewise condensation to be combined ~lith the polymer dispersion ahead of the monomer degasi~ica-tion zone.
The dispersion o~ vinyl chloride homopolymers, graIt po'lymers or copolymers to be treated in accordance with the present invention can b'e made by a process,'such as that'described by H. Kainer in the book enti-tled '~Po]y-vinylchlorid und Vinylchloride-Mischpolymerisa-t.", pu'--blished by Springer-Verlag, Berlin/Heidelberg/New York, 1965, pages 12-59.
One exemplary embodirnent of -the process o~ -the present lZ7~3~.38 i.nventior!-~liL no-~i be ~esc.r:Lbed wi-th reference -to the IccoTllpanyint~ drcl;~ing. Needles -to say the :inven-tlon is in r-lo way limL-t;ed -to -the exemp:lary embodi~en-t spec:ifi-cal~y describecl Wi.-th re:~erence -to -the dra~Jing:
S-tearQ is introduced through a li.ne 1 into a s-tri.pp-- i-ng column 2 for as long as necessary to obtain conden-sate in a heat exchanger 30 The str:ipping colu~n 2. compri-ses a vertic~l column having sieve pl.ates 4 at certain inter~als arranged -therein, perpendicularly with re-spect -to the column The sieve plates 4 have no par-ti-cular liquid ma-t-ter inlet or outlet and distinguish in this feature over the inserts normally used in conven-tional sieve plate columns, such as those described by E. Ki.rschbaum in "Destillier- und Rektifizier-technik'~, . Springer-Verlag, Berlin-Gottingen-Heidelberg (1950)~
page 97. The gas and/or liquid matter apertures 5 pro-vided in the sieve plates have a diameter between 1 and 10 mm, -the total surface area of those apertures being equal to 5 up to 50 % of the column's cross-sec-~tional area. Once the stripping column 2 has been warmed Up, a polymer dispersion having a mean particl.e size of about 20 up to 500 microns is in-troduced -there-i.nto overhead. The dispersion comes from a reservoir 6, travel.s through a line 7, is prehea-ted in a heat-ex-changer 8 and supplied in metered ~uanti-ti.es b~ means of a dosing me-ter 9. Following -this, the strippin~
column is supplied with -the quantity of steam which is necessary to establish a -temperature of 90 Up -to 100C
in the column nead a.nd to expel the monomeric mat-ter f`rom the polyrner dispersion. The polyrner di~perslon -- 8 ~
12786.~8 so ~r~ee~3 Irom monomeric rn~-t-ter is removed at -the base p~r-t; on ol` st:ripp;ng ~olur~n ~ thro~l~;h ~ llne 10 and -t~he heat excharlger 8. The hea-t con-tained in the polymer dispersion is thereby communicated ,,o -the hea t exchan-ger 8 and used ~or preheat'ing ~resh polymer'disper~cJion.
' The -time during w1~ich -the polymer dispersion re-rnains ih -the stripping column 2 is critical]y de-te-rmined ~y the number of sieve plates prov:ided, e.g. 5 up to 50 sleve plates, ~nd by the nature of the solid matter par-ticles in -the dispersion. The steam supplied to the co-lumn is partially used for effecting warm up of the dispersion to the necessary temperature, and mainly used for stripplng off and expelling the monomeric ma-tter frolrl the dispersion. The vaporous ma-tter mixture of steam and monomers issuing at the head of the s-tripp:ing column 2 and travelling through a line 11, is cooled down to a tempera-ture of 5 up to 20C, and only steam is accor-dingly condensed. The condensate containing some mono-meric mat-ter, i.e. a minor proportion consistent wi-th the monomer's solubility in water, can be removed through a line 13 and combined with the polymer dispersion coming from the reservoir 6. Gaseous monomeric matter7 w1nich remains uncondensed~ln -the heat exchanger 3, is dellver-ed through -the line 11-, a container 12 and a line 14 to a further heat exchanger 15, in which it is completely condensed by cooling'down to a temperature of -15~. The resulting li'quefied monomeric matter is collec-ted in a container 16 provided with a line 17 for the removal of gaseous rnonomer, and with a line 18 for the removal of liquid monomer, ~or further uses.
_ g _ ~ ~786.'38 The ~)~ocescs of 1;he ~resent lnvention enab1es poly-mers -to be fre(-~ more effectively and r~ore reliably from monomer~ Imder ecologically beneficial conditions, and -therefo-re coMpares ver-y favorabl~J with -t~e prior ar-t methods. More par-tlcu1arly, the polyrners so purified only con-taln -traces of mo~omers, of the approximate order of 10 ppm. In addi-tion to -this, -the polymers are very pure, so that they can be used in :Eields no-t acces-sible to thern here-tofore owing -to -their-inadequa-te puri-ty and relatively high conten-t of monomers. I-t could no-t have been foreseen that i-t is possible for the presen-t process to be successfully carried out in a stripping column with sieve pla-te inserts therein inasmuch as -the aper-tures providéd in the sieve plates would have been expected -to becomel soiled or encrus-ted with material7 which is however not the case. The present process is generally applicable to the removal of monomeric matter from an aqueous polymer dispersion containing polymer particles with a unit weight greater than tha-t of water.
A polyvinyl chloride dispersion was freed from vlnyl chloride contained therein. The operation was effected as shown in the flow scheme of the accompany- -ing~drawing. The dispe:rsion contained 6 000 ppm of vi- ~
nyl chloride and ~5 weight % of solid matter. The poly- -vinyl chloride had a K-value of 70, a mean partiGle ~
size of 65 microns and a power for absorbing softener of 27.7 %. The dispersion was purified in a stripping column 2 which was provided with 20 sieve plates and had an in-ternal diame:ter of 100 mm.
~2786~3~
The si(ve pla-tes provide~ in -the column were spaced apc~rt at intervals o:E 150 mrn arld provide~ ~ith 250 ape-rtures 2.5 mm wide. S-team a-t 10~C was introduced -thrGugh line 1 into stripping column 2 for as long as necessary -to obtain condensed water in heat exchanger 3. ~ile the supply of stearn was continued, aqueous polymer dispersion was in-troduced into -the head of stripping column 2 at a -throughput ra-te o~ 48 l~h7 corresponding -to a mean sojourn time of 1 mi~ute of the dispersion in -the column. The column was more par-tivu~Larly supplied wi-th the quantity of s-team necessary to obtain, in heat exchanger 3, abou-t 3 weight % of con-densa-te, based on -the quantity of dispersion supplied per hour, and to have a tempera-ture of 95 up to 100C in -the gas phase near the head of the column, and a tempe-rature of 102 up to 105C in the column base portion.
The differential pressure in the column was 50 up to 80 mm Hg. 1.5 l/h of vinyl chloride-contalning water was collected in con-tainer 12 and subsequentIy combined with the polymer dispersion to be purified. The dispersion -taken from the base portion of stripping column 2 con-tained less than~1 ppm of vinyl chloride in -the a~ueous phase, and less than 10 ppm of vinyl chloride in -the po-lyvinyl ch1orlde phase.~he residual content of vinyl chloride in the polymer dispersion was iden-tified by gas chromatography. 125 g/h of vinyl chloride was condensed in hea-t exchanger 5 at -30C.
EY~MPLE 2 The procedure was the same as that described in Exarnple 1, save tha-t the polymer dispersion which was 127136:~8 pur i f'ied cor:L-t~i ned :rigid polyviny:L chloride wi th a K-value of 6~. The polyme:r pal--tlc:Les had a Mean par-ticl.e si~e o:E 120 m:icrons and ~ power for absorbing soften.er - of 1,7~ ~ 5 %. The dispe:rsion con-tained 5200 ppm of -vinyl chlorlde. The dispe:rsion was pu-t through -the colunm at a ra-te of 48 l/h, corresponding to a mean 2 minute sojourn time of -the dispersion ln the colu.mn. The column was supplied wi-th the quantity of steam necessary to ob-tain, in hea-t exchanger 3, abou-t 5 weight % OI conden-sa-te, based on the quan-tity of disperslon supplied per hour. ~he purified dispersion was found to contai.n 10 ppm of viny:L chloride in -the solid ma-tter, and less than 1 ~pm of vinyl chloride in the aqueous phase.
The p:~es~n-t invention rel~-ltec -to a p:rvc~ss .-for free-ing an aquec,us dispersion of a poly~ner f:rom a monomer p:reent -the:rei.n, the polym~r, which may ~e a homopolyrner, graf-t polymcr or copolyrner, having an ex-trerllely mirlor c~ncerltra-tion of residual rilonomer af-ter purif:icationO
I-t; has long been kno~rn -that aqueous po-ymer disper-; sions can be freed from volatile cons-tituen-ts 'by ~lol.iing an iner-t gas or steam at abo-u-t 60-70C through the dis-persjon, i.e. by subjecting the dispers:ion -to steam di-stilla--tion. ~'his has 'been described in Ge~rman Published Specifica-tion ("Auslegeschri~t~ No. 1,2/-~8,943, and in "Kunststoffe" (1959), volume 49, No. 10, page 499, and also in "Chemical Engineering", March 1972, page 960 :[n those cases in which aqueous polyvinyl chloride suspensions are worked up under -the condi-tions just described, -tne polymer is subsequen-tly dried by means of air~ whereby it is freed from a fur-ther proportion of vinyl chloride, e.g. a`bout 2 weight %, based on the quanti-ty of vinyl chlorlde su'bjected to polymeriza~ti.on7 which is allowed to escape in-to the atmosphere. In other words, the issuing gas contains vinyl chloride in propor-tions which are clearly beyond an accepta'ble emiss.ion limit, namely beyond the limit of 150 mg of vinyl cklo-- ride per cubic meter of issuing gas. In additLon to this, excessive proportions of vinyl chloride go into the was-te water. Despite -this, the final dry polyvinyl chloride still contains several hundred ppm of monomeric vinyl chloride, which is absorbed i:n the polyrner and cannot be - 2 ~
1;~78~8 rernove~rl-there:f:r-(Jm by -the purlfying procedure descri'bed above.
0~l~ o~ the u~es of polyvin~1 chloride sheets i~ in packlng Loocl, wh-ch is hazardou~ inasmuch a~ residual mono~ers con-tail1~d in -the polymer ma-y mi~rat~ i~-to th~?
food, It is -therefore obllga-tory for -th~ dry monomer ccn-taining polyrners -to be subjected to an additional special purifying -treatment.
A process wherein dry polyvinyl chloride made in conven-tion~l manner is freed from resi~ual vinyl chlo-ridej -~hich is embedded or occluded in -the polymer par-ticles, has been 'described in German Published Specifi-cation ("~ffenlegungsschrift") No. 2,331,895~ This pro-cess, which enables polyvinyl chloride to be freed from vinyl chloride and further comonomers, if any, comprises:
heating the polymer to a temperature ranging from i-ts freezing tem'pera-ture to 180C by directly condensing steam -thereonto; maintaining the polymer at that -tempe-rature for the period necessary to free it from the bulk of monomer or monomers therein; and cooling the polymer down to a temperature lower than i-ts freezing point by evaporating the s-team condensed on -the polymer. A pre-ferred embodiment of this process comprises heating -the polymer to a temperature ranging from 80 -to 1~0C and allowlng it to remain a-t that temperature for a period of a'bout 5 minutes up to 2 hours, especially 10 to 60 minutes. Typical of this known process is that the de-gasifica-tion is effec-ted a-t the dew point of wa-ter, as described in -the working Examples of that Specifica-tion.
A disadvan-tage encountered with this earlier pro-786~38 cesx -i~esi(1~s in thC f.lct -t~la-t -the ?o~lymer so plrifled continu s to pr~serlt rela-5ive^1y high proportions o-~ rno-norners. As shown in EY~ar~lp1e 1 of ~erri~an P~blished Spe-cifica-tion ("O1fen]egungsschrift" No. 2~31,89~, the purified po:Lyrner con-tains 3 g (or 3,000 ppm) of residual rr.onorners per kg of oolymer. This known process is effect-ed at ternpera-tures ancl under pressures wh:ich correspond -to the dew poin-t of water under -the conditions seLecte~, which naturally means 'nigh a-nd comrnercial~Ly unat-tractive consump-tion of s-team.
In clear contrast therewi-th, -the present inven-tion - provides a process permitting an a~ueolls polymer dlsper-sion -to be freed from`monomeric mat-ter wi-th the resultan-t formation of a purified product containing a few ppm of residual monomer(s), the purified produc-t presentinO this minor concentration of residual Monorner~s) being obtain-ed much more rapidly than in the prior processes of which we are aware.
The following proper-ties of a vinyl chloride/water/
P01YVinY1 chloride-sys-tem are of importance to the removal of monomeric vinyl chloride from an aqueous polyvinyl chlo-ride dispersion~ and should conveniently be considered in effecting such operation.
a) Bunsen's solubility coefflcient a of vinyl chloride in water, which has the following values at temperatures of from 0.1C up to 100C: -0.1C 2 unit vol.vinyl chloride/uni-t vol. water 20C 1 unit vol.vinyl chloride/uni-t vol. water 35C 5 unit vol.vinyl chloride/unit vol. wa-ter 60C 0.1 unit vol.vinyl chloride/unit vol. water 100C 0 unit vol.vinyl chloride/uni-t vol. water 12~8~3 b) :Bur~,er~'~ ;o'lllbility coeïEicierl-t ~ of v:iny:l ch'loride in c)(lueolll PVC~ is?eL,c,ion containing ,5 we:ight ~6 o, solid ~1'.1 tter, w'n;ch has -the following values:
at; 6C 5 unit vol. -vinyl chloride/uni-t vol. wa-ter 18C 3 uni-t vol. vinyl chloride/unit vol. wa-ter 2~C 2 unit vol~ vinyl chloride/unit vol. wa-ter 5~C 1 unit vol. vinyl chloride/uni-t vol. wa-ter 7~C o.6 uni~t vol. vinyl chloride/uni-t vol. l,Jater 0 C) The solub:ili-ty of vi.nyl chloride in polyvinyl chloride.
The following quanti~t:ies of vinyl chloride have been ~'folmd to be dls~olved a-tl-the'following -temperatures e.g. in polyvinyl chloride having a mean particle size of 60 up -to 120 microns and a ~-value of 70.
- ' At 0C 100 g vinyl chloride/kg polyvinyl chloride 2L~oc '50 g vinyl chloridelkg polyvinyl chloride 40C 24 g vinyl chloride/~g polyvinyl chloride 60C 10 g vin-yl chloride/kg polyvinyl ch]oride 100C 4 g vinyl chloride/kg polyvinyl chloride d) The dis-tribu-tion coefficient of vinyl chloride be-tween water and PVC, which is equal -to abou~t 1:15.
We have now unexpectedly found that -the phase equili-bria commence set-ting within the tempera-ture range of 90C
to 100C at intervals of 10 up to 100 seconds under con-ditions which provide for a very effective exchange of cons-tituents between -the individual phases of the above miY,tures a) c). Temperatures around 100C, are, however, ~o known to irnpair the quali-ty of PVC. To avoid -this, i-t is ~7~6.'38 nect~ 1r~y rO~ -the in.~luence of -tempera-tllre o-n YVC to ~be li1n:L-I;ed -to evera~ n-ilLltcs. In o:rder to e-l~ec-ti-vely re-rno-~e Monome.ri.e matter ,`rolll an aqueouc PVC-dispeLsion at -tempera-ture; within -the rarlge 90 and 100C, i-t is f`inally necessary -to c~stablish condi-t:ions, which p:rovide for an e~fective exchange of cor.~s-ti-tuen-ts and thereby or a compLete setting of the phclse equilibria, and also for -the use o:. a sui-table gas phase enabling the monomeric matter -to b~ removed The process of -rhe presen-t in~en.-tion for removi-ng rnonomeric ma-t-ter from an aqueous dispersion of a polymer con-taining at least 50 ~eight % of polymeri~ed vinyl chlo-ride comprises: introducing the dispersion i.nto -the upper portio.n of a column provided with sie~e plates and con-tac-ting -the dispersion therein for a period of about 10 seconds up -to 20 mi-nu~tes and under a pressure of abou-t 600 up to 1200 mm Hg wlth ho-t steam a-t abou-t 100 up to 150C flowing countercurrently wi-th respec-t to -the disper-sion; removing the po]ymer dispersicn so -treated from the column base portion, and condensing stagewise a vaporous mat-ter mixture issuing at -the head o:- -the column so as to recover an aqueous phase and the monomeric ma-tter~
In accordance wi-th a preferred feature of -the pre-sent Lnven-tion, the aqueous dispersion contains approxi-mately 10 up to 60 welght %, more preferably 25-up -to 40 wcight %, of polymeri^ solids which in turn should preferably con-tain a-t leas-t 85 weight % of polymerized vinyl chloride~ The -term "polymers" as used herein com-prises polyvinyl chloride homopolymers and vinyl chloride copolymers, e.g. copolymers of vinyl chloride wi-th. vinyl 12786;~8 tr-l t~ t i rs cll.o ~dvarlt;ageous for -the polymer ~isper-s:iorl to con-t.1in betli/ee~l a'bou-t 0.2 up to 5 welghl 5b of virly~l, ch'lorid~.
A .~llr-th~r preferred fea-ture of the presen-t process cornp.rises hea-tlllr -the polymer to a -tempera-ture of abou-t 60 up to 90C ancl t;hen introdllcing it into -the colu~n.
~:o n ~c~ cte 6~
The dispersion so prehea-ted is-ee~ R~inslde the column ~ith Ihot si;eam ascending therein~ which prelerably is at a terrlpexature of 100 up -to 150~, a.nd causes a tem-0 pe:ratllre 0.~ 90 Up to 100C to be es-tablished ln the co.Lumn head. The column should preferably be opera-ted uncle:r a p.ressure of 700 up to 1100 mm Hg. A relatively mlnor proportion of steam, equal to 1 up -to 5 weight %
' of water, based on the quanti-ty of d1spersion supplied to the co]umn, escapes at the head of the column. Tha po-lymer dispersion i-tself is generally allowed to rem.1in ln -the column over a period of 0.3 up to 10 minu-tes.
The invention also provldes for the aqueous phase obtained on subjecting the vaporous matter mi~ture issuing overhead to stagewise condensation to be combined ~lith the polymer dispersion ahead of the monomer degasi~ica-tion zone.
The dispersion o~ vinyl chloride homopolymers, graIt po'lymers or copolymers to be treated in accordance with the present invention can b'e made by a process,'such as that'described by H. Kainer in the book enti-tled '~Po]y-vinylchlorid und Vinylchloride-Mischpolymerisa-t.", pu'--blished by Springer-Verlag, Berlin/Heidelberg/New York, 1965, pages 12-59.
One exemplary embodirnent of -the process o~ -the present lZ7~3~.38 i.nventior!-~liL no-~i be ~esc.r:Lbed wi-th reference -to the IccoTllpanyint~ drcl;~ing. Needles -to say the :inven-tlon is in r-lo way limL-t;ed -to -the exemp:lary embodi~en-t spec:ifi-cal~y describecl Wi.-th re:~erence -to -the dra~Jing:
S-tearQ is introduced through a li.ne 1 into a s-tri.pp-- i-ng column 2 for as long as necessary to obtain conden-sate in a heat exchanger 30 The str:ipping colu~n 2. compri-ses a vertic~l column having sieve pl.ates 4 at certain inter~als arranged -therein, perpendicularly with re-spect -to the column The sieve plates 4 have no par-ti-cular liquid ma-t-ter inlet or outlet and distinguish in this feature over the inserts normally used in conven-tional sieve plate columns, such as those described by E. Ki.rschbaum in "Destillier- und Rektifizier-technik'~, . Springer-Verlag, Berlin-Gottingen-Heidelberg (1950)~
page 97. The gas and/or liquid matter apertures 5 pro-vided in the sieve plates have a diameter between 1 and 10 mm, -the total surface area of those apertures being equal to 5 up to 50 % of the column's cross-sec-~tional area. Once the stripping column 2 has been warmed Up, a polymer dispersion having a mean particl.e size of about 20 up to 500 microns is in-troduced -there-i.nto overhead. The dispersion comes from a reservoir 6, travel.s through a line 7, is prehea-ted in a heat-ex-changer 8 and supplied in metered ~uanti-ti.es b~ means of a dosing me-ter 9. Following -this, the strippin~
column is supplied with -the quantity of steam which is necessary to establish a -temperature of 90 Up -to 100C
in the column nead a.nd to expel the monomeric mat-ter f`rom the polyrner dispersion. The polyrner di~perslon -- 8 ~
12786.~8 so ~r~ee~3 Irom monomeric rn~-t-ter is removed at -the base p~r-t; on ol` st:ripp;ng ~olur~n ~ thro~l~;h ~ llne 10 and -t~he heat excharlger 8. The hea-t con-tained in the polymer dispersion is thereby communicated ,,o -the hea t exchan-ger 8 and used ~or preheat'ing ~resh polymer'disper~cJion.
' The -time during w1~ich -the polymer dispersion re-rnains ih -the stripping column 2 is critical]y de-te-rmined ~y the number of sieve plates prov:ided, e.g. 5 up to 50 sleve plates, ~nd by the nature of the solid matter par-ticles in -the dispersion. The steam supplied to the co-lumn is partially used for effecting warm up of the dispersion to the necessary temperature, and mainly used for stripplng off and expelling the monomeric ma-tter frolrl the dispersion. The vaporous ma-tter mixture of steam and monomers issuing at the head of the s-tripp:ing column 2 and travelling through a line 11, is cooled down to a tempera-ture of 5 up to 20C, and only steam is accor-dingly condensed. The condensate containing some mono-meric mat-ter, i.e. a minor proportion consistent wi-th the monomer's solubility in water, can be removed through a line 13 and combined with the polymer dispersion coming from the reservoir 6. Gaseous monomeric matter7 w1nich remains uncondensed~ln -the heat exchanger 3, is dellver-ed through -the line 11-, a container 12 and a line 14 to a further heat exchanger 15, in which it is completely condensed by cooling'down to a temperature of -15~. The resulting li'quefied monomeric matter is collec-ted in a container 16 provided with a line 17 for the removal of gaseous rnonomer, and with a line 18 for the removal of liquid monomer, ~or further uses.
_ g _ ~ ~786.'38 The ~)~ocescs of 1;he ~resent lnvention enab1es poly-mers -to be fre(-~ more effectively and r~ore reliably from monomer~ Imder ecologically beneficial conditions, and -therefo-re coMpares ver-y favorabl~J with -t~e prior ar-t methods. More par-tlcu1arly, the polyrners so purified only con-taln -traces of mo~omers, of the approximate order of 10 ppm. In addi-tion to -this, -the polymers are very pure, so that they can be used in :Eields no-t acces-sible to thern here-tofore owing -to -their-inadequa-te puri-ty and relatively high conten-t of monomers. I-t could no-t have been foreseen that i-t is possible for the presen-t process to be successfully carried out in a stripping column with sieve pla-te inserts therein inasmuch as -the aper-tures providéd in the sieve plates would have been expected -to becomel soiled or encrus-ted with material7 which is however not the case. The present process is generally applicable to the removal of monomeric matter from an aqueous polymer dispersion containing polymer particles with a unit weight greater than tha-t of water.
A polyvinyl chloride dispersion was freed from vlnyl chloride contained therein. The operation was effected as shown in the flow scheme of the accompany- -ing~drawing. The dispe:rsion contained 6 000 ppm of vi- ~
nyl chloride and ~5 weight % of solid matter. The poly- -vinyl chloride had a K-value of 70, a mean partiGle ~
size of 65 microns and a power for absorbing softener of 27.7 %. The dispersion was purified in a stripping column 2 which was provided with 20 sieve plates and had an in-ternal diame:ter of 100 mm.
~2786~3~
The si(ve pla-tes provide~ in -the column were spaced apc~rt at intervals o:E 150 mrn arld provide~ ~ith 250 ape-rtures 2.5 mm wide. S-team a-t 10~C was introduced -thrGugh line 1 into stripping column 2 for as long as necessary -to obtain condensed water in heat exchanger 3. ~ile the supply of stearn was continued, aqueous polymer dispersion was in-troduced into -the head of stripping column 2 at a -throughput ra-te o~ 48 l~h7 corresponding -to a mean sojourn time of 1 mi~ute of the dispersion in -the column. The column was more par-tivu~Larly supplied wi-th the quantity of s-team necessary to obtain, in heat exchanger 3, abou-t 3 weight % of con-densa-te, based on -the quantity of dispersion supplied per hour, and to have a tempera-ture of 95 up to 100C in -the gas phase near the head of the column, and a tempe-rature of 102 up to 105C in the column base portion.
The differential pressure in the column was 50 up to 80 mm Hg. 1.5 l/h of vinyl chloride-contalning water was collected in con-tainer 12 and subsequentIy combined with the polymer dispersion to be purified. The dispersion -taken from the base portion of stripping column 2 con-tained less than~1 ppm of vinyl chloride in -the a~ueous phase, and less than 10 ppm of vinyl chloride in -the po-lyvinyl ch1orlde phase.~he residual content of vinyl chloride in the polymer dispersion was iden-tified by gas chromatography. 125 g/h of vinyl chloride was condensed in hea-t exchanger 5 at -30C.
EY~MPLE 2 The procedure was the same as that described in Exarnple 1, save tha-t the polymer dispersion which was 127136:~8 pur i f'ied cor:L-t~i ned :rigid polyviny:L chloride wi th a K-value of 6~. The polyme:r pal--tlc:Les had a Mean par-ticl.e si~e o:E 120 m:icrons and ~ power for absorbing soften.er - of 1,7~ ~ 5 %. The dispe:rsion con-tained 5200 ppm of -vinyl chlorlde. The dispe:rsion was pu-t through -the colunm at a ra-te of 48 l/h, corresponding to a mean 2 minute sojourn time of -the dispersion ln the colu.mn. The column was supplied wi-th the quantity of steam necessary to ob-tain, in hea-t exchanger 3, abou-t 5 weight % OI conden-sa-te, based on the quan-tity of disperslon supplied per hour. ~he purified dispersion was found to contai.n 10 ppm of viny:L chloride in -the solid ma-tter, and less than 1 ~pm of vinyl chloride in the aqueous phase.
Claims (6)
1. A process for removing monomeric matter from an aqueous dispersion of a polymer containing at least 50 weight percent of polymerized vinyl chloride which comprises introducing the dispersion into the upper portion of a substantially vertical column provided with a series of horizontal perforated plates but with no liquid down-comers and contacting the dispersion therein for a period of about 1 minute up to 20 minutes and under a pressure of about 760 to 1200 mm Hg with steam flowing countercurrently with respect to the dispersion wherein the temperature of the slurry in the column is between 90° and 105°C, the stripped slurry is removed from the column at or near the foot of the column and the steam and vinyl chloride monomer are removed from the column at or near the head of the column.
2. The process as claimed in claim 1, wherein the aqueous dispersion contains 10 to 60 weight percent of solid matter.
3. The process as claimed in claim 1, wherein the polymer is a copolymer of vinyl chloride and vinyl acetate,
4. The process as claimed in claim 1, wherein the aqueous dispersion contains about 0.2 up to 5 weight percent of vinyl chloride.
5. The process as claimed in claim 1, wherein the polymer is a homopolymer of vinyl chloride.
6. The process as claimed in claim 1, wherein the polymer is prepared by suspension polymerization.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE2521780A DE2521780C2 (en) | 1975-05-16 | 1975-05-16 | Process for the continuous removal of monomers from an aqueous dispersion of a polymer |
| DEP2521780.5 | 1975-05-16 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1278638C true CA1278638C (en) | 1991-01-02 |
Family
ID=5946686
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000252196A Expired - Fee Related CA1278638C (en) | 1975-05-16 | 1976-05-11 | Process for continuously removing monomers from an aqueous dispersion of a polymer |
Country Status (22)
| Country | Link |
|---|---|
| JP (1) | JPS51140985A (en) |
| AT (1) | AT352393B (en) |
| BE (1) | BE841838A (en) |
| CA (1) | CA1278638C (en) |
| CH (1) | CH601358A5 (en) |
| CS (1) | CS191306B2 (en) |
| DD (1) | DD124253A5 (en) |
| DE (1) | DE2521780C2 (en) |
| DK (1) | DK213576A (en) |
| ES (1) | ES447280A1 (en) |
| FR (1) | FR2311037A1 (en) |
| GB (1) | GB1497510A (en) |
| HU (1) | HU174924B (en) |
| IE (1) | IE43107B1 (en) |
| IT (1) | IT1061284B (en) |
| LU (1) | LU74948A1 (en) |
| NL (1) | NL160841B (en) |
| NO (1) | NO146284B (en) |
| PL (1) | PL103008B1 (en) |
| SE (1) | SE7602710L (en) |
| SU (1) | SU841591A3 (en) |
| YU (1) | YU121376A (en) |
Families Citing this family (21)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2718858A1 (en) * | 1977-04-28 | 1978-11-02 | Hoechst Ag | Degassing column with equally spaced perforated plates - supported by peripheral ring and lugs and crossed by downcomers with adjustable overflow height |
| DE2718857A1 (en) * | 1977-04-28 | 1978-11-02 | Hoechst Ag | Degassing column with equally spaced perforated plates - supported by peripheral ring and lugs and crossed by downcomers with adjustable overflow height |
| DE2640592A1 (en) * | 1976-09-09 | 1978-03-16 | Hoechst Ag | Fractionation column for removing monomer from polymer suspensions - which extracts volatiles while avoiding sedimentation |
| JPS5298591U (en) * | 1976-01-20 | 1977-07-25 | ||
| NZ184661A (en) * | 1976-07-27 | 1979-08-31 | Ici Australia Ltd | Removing monomer from vinyl chloride polymers |
| DE2640546C2 (en) * | 1976-09-09 | 1982-07-01 | Hoechst Ag, 6000 Frankfurt | Process for the continuous removal of vinyl chloride from an aqueous dispersion of homo- and copolymers of vinyl chloride |
| DE2800608A1 (en) * | 1977-04-11 | 1978-10-19 | Buna Chem Werke Veb | PROCESS FOR THE DEMONOMERIZATION OF POLYMER DISPERSIONS, PREFERABLY POLYVINYL CHLORIDE DISPERSIONS |
| JPS548693A (en) * | 1977-06-21 | 1979-01-23 | Chisso Corp | Removal of monomer from vinyl chloride resin slurry by steam treatment using improved plate column |
| DE2744462C2 (en) * | 1977-10-03 | 1982-09-16 | Wacker-Chemie GmbH, 8000 München | Process for preventing foam formation during the removal of residual monomers from aqueous polymer dispersions |
| US4201628A (en) * | 1977-10-07 | 1980-05-06 | The Goodyear Tire & Rubber Company | Separation apparatus |
| DE2746909C3 (en) * | 1977-10-19 | 1982-03-11 | Hoechst Ag, 6000 Frankfurt | Process for the continuous removal of residual hydrocarbons from polyolefins |
| US4200734A (en) * | 1977-11-21 | 1980-04-29 | Diamond Shamrock Corporation | Process for polymerization of polyvinyl chloride and VCM monomer removal |
| DE2759097C2 (en) * | 1977-12-30 | 1987-03-05 | Norsk Hydro A.S., Oslo | Process for reducing the vinyl chloride content in aqueous dispersions of vinyl chloride polymers and copolymers |
| US4228273A (en) * | 1978-09-05 | 1980-10-14 | Tenneco Chemicals, Inc. | Process for the removal of vinyl chloride from aqueous dispersions of vinyl chloride resins |
| DE2855146C2 (en) * | 1978-12-20 | 1983-04-28 | Chisso Corp., Osaka | Process for removing residual monomeric vinyl chloride from an aqueous dispersion of a polyvinyl chloride resin powder |
| DE2903586A1 (en) | 1979-01-31 | 1980-08-14 | Hoechst Ag | METHOD FOR THE CONTINUOUS REMOVAL OF RESIDUAL HYDROCARBONS FROM POLYOLEFINS AND DEVICE FOR CARRYING OUT THE METHOD |
| US4402916A (en) * | 1981-06-30 | 1983-09-06 | Marathon Oil Company | Dilution apparatus and method |
| JPS63317306A (en) * | 1987-06-19 | 1988-12-26 | Chisso Corp | Low polymerization degree vinyl chloride polymer powder with small amount of residual vinyl chloride monomer and its preparation |
| WO1996018659A1 (en) * | 1994-12-12 | 1996-06-20 | C.I.R.S. S.P.A. | Method and plant for the production of polyvinylchloride in aqueous suspension with recovery of refluxes |
| JP3950743B2 (en) * | 2002-06-03 | 2007-08-01 | キヤノン株式会社 | Method for producing toner particles |
| JP6829567B2 (en) * | 2016-09-16 | 2021-02-10 | 株式会社クラレ | Method for producing a polymer from which volatile components have been removed |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| NL129660C (en) * | 1964-08-24 | |||
| US3816379A (en) * | 1971-07-26 | 1974-06-11 | Exxon Research Engineering Co | Monomer and solvent recovery in polymerization processes |
| BE793505A (en) * | 1972-12-29 | 1973-06-29 | Solvay | Process for removing residual vinyl chloride present in the polymer |
| NO752264L (en) * | 1974-08-29 | 1976-03-02 | Huels Chemische Werke Ag | |
| DE2450464A1 (en) * | 1974-10-24 | 1976-04-29 | Basf Ag | PROCESS FOR LOW EMISSIONS REMOVAL OF VINYL CHLORIDE FROM POLYMERIZES OF VINYL CHLORIDE |
| DE2509937C3 (en) * | 1975-03-07 | 1981-04-16 | Hoechst Ag, 6000 Frankfurt | Device for the aftertreatment of homo- and copolymers of vinyl chloride |
| DE2520591C3 (en) * | 1975-05-09 | 1980-11-06 | Hoechst Ag, 6000 Frankfurt | Process and device for the continuous treatment of aqueous homo- and copolymer dispersions, the polymer content of which is at least 50% by weight polymerized |
-
1975
- 1975-05-16 DE DE2521780A patent/DE2521780C2/en not_active Expired
-
1976
- 1976-02-24 CH CH227676A patent/CH601358A5/xx not_active IP Right Cessation
- 1976-02-27 SE SE7602710A patent/SE7602710L/en not_active Application Discontinuation
- 1976-04-23 ES ES447280A patent/ES447280A1/en not_active Expired
- 1976-04-29 SU SU762351858A patent/SU841591A3/en active
- 1976-05-04 GB GB18174/76A patent/GB1497510A/en not_active Expired
- 1976-05-11 CA CA000252196A patent/CA1278638C/en not_active Expired - Fee Related
- 1976-05-13 DK DK213576A patent/DK213576A/en not_active Application Discontinuation
- 1976-05-13 HU HU76HO1903A patent/HU174924B/en unknown
- 1976-05-14 LU LU74948A patent/LU74948A1/xx unknown
- 1976-05-14 NL NL7605200.A patent/NL160841B/en not_active Application Discontinuation
- 1976-05-14 IT IT49482/76A patent/IT1061284B/en active
- 1976-05-14 DD DD192857A patent/DD124253A5/en unknown
- 1976-05-14 NO NO761676A patent/NO146284B/en unknown
- 1976-05-14 AT AT354776A patent/AT352393B/en not_active IP Right Cessation
- 1976-05-14 BE BE167037A patent/BE841838A/en unknown
- 1976-05-14 IE IE1027/76A patent/IE43107B1/en unknown
- 1976-05-14 FR FR7614699A patent/FR2311037A1/en active Granted
- 1976-05-14 YU YU01213/76A patent/YU121376A/en unknown
- 1976-05-15 PL PL1976189603A patent/PL103008B1/en unknown
- 1976-05-17 CS CS763269A patent/CS191306B2/en unknown
- 1976-05-17 JP JP51056405A patent/JPS51140985A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| HU174924B (en) | 1980-04-28 |
| DE2521780A1 (en) | 1976-11-18 |
| SE7602710L (en) | 1976-11-17 |
| IE43107B1 (en) | 1980-12-17 |
| JPS5246994B2 (en) | 1977-11-29 |
| AT352393B (en) | 1979-09-10 |
| NO146284B (en) | 1982-05-24 |
| GB1497510A (en) | 1978-01-12 |
| DD124253A5 (en) | 1977-02-09 |
| DE2521780C2 (en) | 1982-10-21 |
| JPS51140985A (en) | 1976-12-04 |
| ATA354776A (en) | 1979-02-15 |
| IE43107L (en) | 1976-11-16 |
| SU841591A3 (en) | 1981-06-23 |
| FR2311037A1 (en) | 1976-12-10 |
| YU121376A (en) | 1982-02-28 |
| BE841838A (en) | 1976-11-16 |
| LU74948A1 (en) | 1977-02-14 |
| NO761676L (en) | 1976-11-17 |
| IT1061284B (en) | 1983-02-28 |
| DK213576A (en) | 1976-11-17 |
| ES447280A1 (en) | 1977-06-16 |
| PL103008B1 (en) | 1979-05-31 |
| NL160841B (en) | 1979-07-16 |
| CS191306B2 (en) | 1979-06-29 |
| CH601358A5 (en) | 1978-07-14 |
| FR2311037B1 (en) | 1981-12-31 |
| NL7605200A (en) | 1976-11-18 |
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