CA1070889A - Process for the production of urea-formaldehyde adhesives or resins and products obtained thereby - Google Patents

Process for the production of urea-formaldehyde adhesives or resins and products obtained thereby

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Publication number
CA1070889A
CA1070889A CA251,702A CA251702A CA1070889A CA 1070889 A CA1070889 A CA 1070889A CA 251702 A CA251702 A CA 251702A CA 1070889 A CA1070889 A CA 1070889A
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CA
Canada
Prior art keywords
formaldehyde
solution
urea
methanol
stage
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
CA251,702A
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French (fr)
Inventor
Pedro Mir Puig
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Individual
Original Assignee
Individual
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Publication of CA1070889A publication Critical patent/CA1070889A/en
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Classifications

    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08GMACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G12/00Condensation polymers of aldehydes or ketones with only compounds containing hydrogen attached to nitrogen
    • C08G12/02Condensation polymers of aldehydes or ketones with only compounds containing hydrogen attached to nitrogen of aldehydes
    • C08G12/04Condensation polymers of aldehydes or ketones with only compounds containing hydrogen attached to nitrogen of aldehydes with acyclic or carbocyclic compounds
    • C08G12/10Condensation polymers of aldehydes or ketones with only compounds containing hydrogen attached to nitrogen of aldehydes with acyclic or carbocyclic compounds with acyclic compounds having the moiety X=C(—N<)2 in which X is O, S or —N
    • C08G12/12Ureas; Thioureas

Abstract

ABSTRACT OF THE DISCLOSURE

A process for the production of urea-formaldehyde adhesives or resins comprises the stages of catalytically oxidizing methanol with air, condensing some of the gases obtained during oxidation, separating the condensed solution from the uncondensed gases, cooling and washing the uncondensed gases with a solution of cold polymerised formaldehyde to take up any methanol and formaldehyde which might be present, separately distilling the condensed solution and the cooled washed gases to produce two formaldehyde solutions, combining parts of the two solutions and mixing the concentrated aqueous solution of formaldehyde obtained from the distilling of the condensed solution with urea under predetermined conditions.

Description

The present invention relates to a process for the production of urea-formaldehyde adhesives or resins, and to the products obtained by this process. More specifically, the invention relates to a process for producing urea-formaldehyde adhesives or resins from methanol by preparinga concentrated aqueous solution of formaldehyde and reacting it with ureaO The invention also relates to the preparation of concentrated aqueous solutions of formaldehyde which may be run off from the installation for other applications, such as the production of paraformaldehyde.
There are already known various processes for preparing formaldehyde from methanol, generally in the gas phase and at elevated temperature, which comprise passing a mixture of methanol vapour and air in suitable proportions over a catalystO
In one of these known processes, the oxidation products obtained are condensed in order to obtain, on the one hand, the condensable products and, on the other hand, the uncondensed gases. These uncondensed gases are washed with water to form a formaldehyde solution and to recover the unreacted methanol.
The solution thus obtained is combined with the condensed products and forms the crude aqueous formaldehyde solution.
The formaldehyde concentration of this solution is dependent upon the quantity of water used for washing the gases.
In addition to formaldehyde, the crude solution obtained contains methanol in a variable quantity according both to the type of catalyst used and to the proportions of air and methanol used. This solution may be directly used or may be partly or completely freed from the methanol present ~ ~
- 2 - ;

c 1~7~88g in it.
Alt}louOh this proccss is ~enerally satisfnctory, it is ne~erth~lcss attended by the disadvanta~e that the concentration of the ~queous formaldehydo solutions obtained is necessarily limited on account of tlle fact that the uncondensed gases have been washed with a quantity of water sufficient to remove the formaldehyde and methanol present in these gases and which would otherwise be lost from the system.
The aqueous formaldehyde solutions thus obtained, of which the concentration ainounts to bet~-een ~C,b and 50~
may then be processed into dilute solutions of urea-formaldellyde adhesive wllich have to b~ concentrated by distillation ln vacuo to form standard commercial-~rade adh~ives, i.e. adhesives with a solids contcn-t of 650/o.
This final distillation sta~e is attended by the Iollowing disadvantages:
a) it is necessary to use an apparatus operating in vacuo, which is always expensive, both in the c~se of continuous operation and in the case of batch opcration;
- b) the resin obtained ilas to be heated, which gives rise to local increases in temperature on tl~e walls of the apparatus, resultingin secondary reactions ~hich adversely affect tlle quality of the resin;
c) it is also difficult to control the ~u~lity of the resin producod on account of c~lan~,es in viscosity ~hich take place durin~ distillation, in addition to ~hich tlle hcatin~ surraccs ~ecome encrllstcd as a rcsult of pol~mcri~ation of tllc rcsins; and d) thc distillate, ~hich al~ays has to be rcmo~cd, jf 3 ~07~889 1 contains relatively large quantities of formaldehyde, which gives rise to a problem of pollution.
The present invention obviates these disadvantages by providing a process for producing urea-formaldehyde adhesives or resins according to the invention comprises the stages of:
a) catalytically oxidizing methanol with air;
b) condensing the gases emanating from the catalytic oxidation of stage (a) whereby condensable products therein are condensed in the form of a solution;
c) separating the solution containing the condensed products obtained in stage (b) from the uncondensed gases remaining after said condenlsation stage;
d) cooling the uncondensed gases from stage (c) and washing the cooled gases in a washing column with a solution of cold polymerised formaldehyde which takes up the methanol and formaldehyde present in the uncon-densed gases;
e) distilling the solution obtained in stage (c) in order to recover separately a concentrated aqueous formaldehyde solution and methanol;
f) distilling the solution obtained in stage (d) in order to recover the methanol taken up into said solution and to isolate the formaldehyde in the form of a solution thereof;
g) combining a part of the formaldehyde solution obtained ~ .

- ~0708~39 ~, .

in sta~e (f) witll th~ conderlsed, distilled formaldellyde solu1;ion obtainc~ in staae (e); and h) mixin~ the concentrated aqucous solution of Iormaldehydc obtaincd in sta~re (e) with urea under conditions of predetermined pH and témperature in order to obtain urea-formaldehyde adllesives or resins.
If desired, all or part of the concentrated aqueous solution of formaldehyde may be run o~f after sta~e (c) for other applications, for example for forming paraformalde~yclc ~ccordin~ to another aspect of the invention, tll~
gas~s are condensed in star~e (b) by washin~ in a washer with the condensed prolucts circulated by means of a ~urnp from tho l)asc of the washer and coolcd by means of a coolant outside tlle w~sher.
Accordill~ to yet another aspect of the invention, the formaldehyde ~Yashing solution used for stage (d) is obtained by running off a formaldchyde solution from the sump of the washing colum~, heatin~ the solution, partly distilling it to reco-~er the methanol present and to isolate the formal~ehyde, and alter cooling remo~in~ a :certain amount of the solution, wnich amount/added to the condensed products emanating from sta~e (c).
AccordinOly, it is possible by virtue of the process accordin~ to the invention directly to obtain urea-formaldchyde adhcsives or resins without any need to carry out a final distillatioll sta~e, because it uses aqueous ~ormal~ehy~c solutions of hi~h concentration by virtuc of thc fact that said solutions only cont~in tllc ~ateI i~rod~lce~l cl~rill~ catalytic o~id~tlon of the metl-lanol. This process
3~) also l1.1S tllo ~(lvanta~re oI cna~ all tllc mcthal~ol prcsorlt r~f 5 ( 1~708~39 in thc uncolldenscd ~ases to be reco~ered, because tllc qua~ltity of wasllin$ a~ent is limited solely by tllc inerease in the consump-tion of heat resulting Iro~n tlle e~llaustion of the methanol contcnt of the washing solution.
The washing column usin~ polymerised formal~ellyde has to opcrate at low temperature, and certain plates of the column may be cooled by means of liquid coolants or methanol - cooled by air in a first washer before catalysis.
- Distillation of the formalde}iyde solution to reco~er the mcthanol may be carried out in th~ usual ~ay, i.e. in suitable columns, under atmospheric prcssure or un1er pressurc ~elo~i atmospheric pressure. ~lowever, in vie~ of thc l`act that complete elimination of the formaldel~yde prescnt in t2)e concentrated forma]dellyde solution may require hi~h tcmperatures, it is possibic directly to use the heat of tlle gases givell-off during catalysis at 500C, providing a heat exchanger is present.
In sta~e (h) of thc process, the hot formaldehyde solution is ~ixed with urea at a pH-va]ue of from 7.5 to 8.5, follo-~ed by the addition of an acid product to Xcep the pH botween 5 and 6.5 if it is desire~ to obtain solutions - of urea-formaldehyde adhesive whicll are subsequently to be stored after cooling. If, attentatively, a pH of the or~er of 8 to 9 is maintained throu6hout sta~e (h) and if the urea is us~d in a smaller proportioll tllan thc formaldchyde, hi~llly sta~le, concelltrated urca-Iormal~ehyde so]utiolls are obtairlcd an~ may be marl(cted in particular as a basic matcrial Ior tllc produc1;ion oI so]id resiIIs~ mouldill~ po~dcr~ or adllc s ~ c s .
3~ q`2~o l~rocos~ acco~din~ to the invention llas in l)~rticular (- 107~)8~9 the iollo~in~ .~dvantagcs.
Firstly thcre is no nee(l to concentrato thc rosin obtaincd, wllich 3lal;es it unnecessary to ~orl; in vacuo and to use an e~pensi~e appara-tus both in the case oI continuous operation and in the cæse of batch operation.
Secondly, the resin obtained does not have to be heated, thereby avoidin~ local increases in temperature on the walls of the apparatus that are the cause of secondary - reactions ~hich can h~ve an adverse ef~ect upon tlle qua]ity of the resin, and also there~y avoidin~ the production of any deposits on the walls of the apparatus.
Thirdly it is possible more cfleotively to control the differo~t qu~lities of resin pro~uced ~y virtllc oi the fact that, once the reactioll is over, the resin is forme~ and only has to be cooled. Accordin~ly, there is no change in viscosity nor any other ~lodification due to subsequent concentration;
Fourthly, it is possible to work ill batclles of ~2 toi~ncs, and finally proble~s of pollution arc completel~-eliminated because no effluents are formed, even durin~cleanin~, b~ virtue of the fact that there is ne~er any formation of erusts ~hich have to be reDIoved. In adclition, there is no atmospheric pollution because the ~ases left after the production of formaldellydo are burnt off in a 2.5 boiler.
Itt should ~c noted that the process can be calricd out continuously, but also it affords the particular advanta~e of bei~ ablc to pro(lllc3 illdivi;lual ~atchos oI a~hesivcs or resins. This 19 illlport;~nt ~ecause~ in ord~r to satisfy ~0 dou!an~, it i.9 olton req~ e(l -to prodllce ~ e~iv~s of ~if~erent quality and this involves making particular adjustments for each of the different adhesives required. To have to make adjustments of this nature is a disadvantage in a method of continuous operation, and it is thus preferred to work in batches using separate tanks where the particular adjustments can be madeO According to the invention, it is possible effectively to work in tanks of this kind which may be simple and lightweight. This would not have been possible with conventional processes which necessitated a final distillation stage, with the associated equipment.
An exemplary embodiment of the invention is described in detail in the following, with reference to the accompanying drawings, wherein:
Figure 1 diagrammatically illustrates an apparatus for the production of urea-formaldehyde adhesives or resins Figure 2 diagrammatically illustrates one embodiment of an apparatus for the continuous production of urea-formaldehyde adhesives from concentrated solutions of -~
formaldehyde.
Using the apparatus illustrated in Figure 1, 2000 kg/
hour of atmospheric air at a pressure of 760 mm of mercury are drawn in by means of a gas blower 10 and introduced into a saturator 12 where they bubble through methanol kept at 50.5C by means of a steam heating unit regulated by a valve 14 The saturator 12 is fed with methanol from a reservoir 16 of which the constant output is regulated by means of a valve 58 fitted in the pipe connecting the reservoir 16 to the saturator 12u The mixture issuing from the saturator 12, containing 1950 kg/h of methanol, is then passed over a catalyst 18 `; _ Q _ ~7~ 889 based on metallic silver kept at a temperature of the order of 500C in order to convert 1160 kg/hour of methanol into formaldehyde by the conventional reaction with corresponding liberation of hydrogen, of which part is oxidised into water by the oxygen present in the air. A
small quantity of carbon dioxide is formed at the same time and virtually all the oxygen present in the air is transformed during the reaction The gaseous mixture emanating from the catalyser then enters the base of a washer 20 which at its head receives the condensation products removed from the base of the washer circulated by means of a pump 22 and cooled by a cooler 24.
The mixture thus collected is delivered by means of a pump 28 and under the control of a valve 30 to a distillation column 32 which removes the methanol present in the mixture it receives. After condensation in a condenser 34, this methanol is returned to the saturator 12 under the control of a valve 36. The aqueous formaldehyde solution remaining in the column 32 has a concentration of 65% and is substantially free from methanol. This solution is removed at the sump of the distil-lation column 32 and is introduced into a reactor 60, in which reaction of the formaldehyde with urea is effected.
The gases issuing from the washer 20 are introduced into a washing column 26 which at its head receives 50% formaldehyde in polymerised and hydrated form derived from column 40 (infra)O
A liquid mixture of the following constituents is collected at the base of the washer 26:
total formaldehyde 1410 kg water 1400 kg methanol 130 kg total condensates 2940 kg The liquid emanating from the second wash of the gases in the column 26 is introduced into a column 40 to remove the methanol and to fix the formaldehydeO The methanol is collected in a condenser 42 and delivered from there to the saturator 12 under the control of a valve 44. ~-The liquid emanating from the sump of the column 40 is recycled by means of a pump 46 to the head of the washing column 26 after having been cooled by a cooler 48.
In order to keep constant the quantity of liquid circulating between the column 26 and the column 40, the excess of this liquid is removed at the output end of the pump 46 by a valve 50 and is added to the concentrated formaldehyde in the distillation column 32. On the other hand, 100 kg/hour of concentrated, partially polymerised formaldehyde are removed from the column 32 and delivered to the column 40 under the control of a valve 52.
The distillation column 40 is heated by means of a steam coil regulated by a valve 54, whilst the distillation column 32 is heated by means of a steam coil regulated by a valve 56.
Various modifications of detail may be made to the 25 process for producing concentrated aqueous formaldehyde solutions described above without departing from the scope of the inventionu , For example, it is possible, in order to accelerate : polymerisation of the formaldehyde used for washing, to add to it traces of a suitable product such as, for example, - 10 - ~

10708~9 traces of an acid or alkali.
It is also possible to leave out the distillation column 40 by increasing the diameter of the column 32 and carrying out the two corresponding distillation operatiuns in this single column.
sy way of modification, it is possible to run off part of the formaldehyde from the last two plates at the base of the column 32 SO as to obtain for example 50% formaldehyde on the one hand and 85% formaldehyde on the other hand.
The 1420 kg of 68% formaldehyde obtained are introduced into the reactor 60 with urea in a variable quantity according ;
to the quality of the adhesive which it is desired to obtain.
For example, 2620 kg of adhesive are obtained with 1200 kg of urea.
The concentrated formaldehyde may be run off at 38 for other applications, for example for the production of paraformaldehydeO
Turning now to Figure 2~ the apparatus illustrated diagrammatically therein is used for 68% formaldehyde solutions obtained in the manner described above. This apparatus comprises a plate column 60 provided with a stirrer 62 rotated by a motor 64 and comprising a plurality of blades, such as 66~ designed to stir the reaction mixture at the level of each plate.
Urea is introduced through an inlet 68 formed in the upper 25 part of the column from a reservoir 70 with continuous feed by an endless screw 72.
The hot 68% formaldehyde is introduced through a lateral inlet 74 into the upper part of the column in a .. . ~ . .
.

~ ~07~E~89 re~,ulate(l (~uallti.ty. .
The plI of the mi.~ture is con~ro].led i21 the upl~er part of the column, beinr~ kept ~et~een pM 7.5 alld pI 8.5, ~ccord~ to t,}le quali.ty of the adhesive to be obtained.
A product ~hich is suffici~ntly acid ~o l;ecl) the pH value between. 5 and 6.5 is ,introduced through a pipe 76 to~rards the middle of the column. Formic acid is ~enerally.used for this pur~ose. The hot urea-formaldcllyde ad'llesive is .
collected at the base of the colullln and is stored after cooling by means of a coolant 7~.
'. The columll 60 i.s equipped wlth means for controlli.n~ ~ ' pll, tempcrature and viscosity in certain plates, adjustmcnts bein~ made accordin6 to tho quality Or ~dllesive to be obtained.
To thi.s end, ccrtai.n parts of the colullln are heated or cooled individually and scparately by means of suitable devices.
Instead of worliing continuously witll the apparatus shown in Fi~ure 2, it is possible to work in batches in 2-~ tanks witll a ca~acity of for e.~ample ~0 cubic metl-es.
I~aturally t~e invention is by no means limited to thc embodiment described abo~re and modifications of dctail may be ma.de ~ithout depar~ing Irom the scopc of the invention.

: - .

. .
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~ ,5~ 1:?

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Claims (9)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A process for the production of a urea-formaldehyde reaction product of the class consisting of urea-formaldehyde adhesives and urea-formaldehyde resins, which comprises the steps of :
a) catalytically oxidizing methanol with air in a ratio of methanol to air passed over catalyst ranging from 0.95 to 0.99 by weight and at a temperature range from 480 to 550°C to produce a partially condensible gaseous product con-taining formaldehyde ;
b) condensing said partially condensible gaseous product emanating from said catalytic oxidation of methanol whereby condensible components therein are condensed in the form of a solution at 60-80°C ;
c) separating the solution containing condensed components in step b) from the uncondensed gases remaining after said condensation step ;
d) cooling the uncondensed gases from step c) and washing the cooled gas in a washing column with a solution comprising cold polymerized formaldehyde which takes up the methanol and formaldehyde present in the uncondensed gas, the ratio of cooled gases to the solution of cold polymerised for-maldehyde ranging from 0.06 to 0.14 by weight and the tempera-ture of the cooled gases and the solution of cold polymerised formaldehyde ranging from 0 to 25°C ;
e) distilling the solution obtained in step c) in order to recover separately methanol and a concentrated aqueous formaldehyde solution, the ratio of the concentrated aqueous formaldehyde solution to methanol being 1-2 by weight and the formaldehyde content of the concentrated aqueous formaldehyde solution being at least partially in polymerized form ;
f) distilling the solution obtained in step d) in order to recover the methanol taken up into said solution and to isolate the formaldehyde in the form of an aqueous solu-tion thereof containing formaldehyde, the ratio of methanol to the aqueous solution of formaldehyde ranging from 0.05 to 0.1 by weight ;
g) passing a portion of the aqueous formaldehyde solution obtained in step f) to distillation step e) and recycling another portion of the aqueous formaldehyde solution obtained in step f) to step d) as the cold polymerized washing solu-tion therein ; and h) reacting with urea at a pH between 7.5 and 9 the aqueous formaldehyde solution obtained in step e) which con-tains from 68 to 70 % concentration of formaldehyde polymer, in a ratio of the aqueous solution of formaldehyde to urea ranging from 1.4 to 2.0, to produce said urea-formaldehyde product.
2. A process as claimed in claim 1, wherein in stage b) the gases are condensed by washing in a washer with the condensed components circulated by means of a pump from the base of the washer, said condensed components being cooled by means of a cooler outside the washer.
3. A process as claimed in claim 1, wherein the form-aldehyde washing solution used in stage d) is obtained by running off a formaldehyde solution from the sump of the washing column, heating it, partly distilling the solution to recover the methanol present in it and to isolate the formal-dehyde and, after cooling, removing a part of the solution which part is added to the condensed components emanating from stage c), the remainder of said solution being used as the washing solution in stage d).
4. A process as claimed in claim 1, wherein the methanol recovered in stages e) and f) is returned to stage a).
5. A process as claimed in claim 1, wherein distillation in stage e) and distillation in stage f) are carried out in two separate columns.
6. A process as claimed in claim 1, wherein distillation in stage e) and distillation in stage f) are carried out in a single column.
7. A process as claimed in claim 1, wherein in stage h) the formaldehyde solution is mixed with urea at a pH
maintained between 7.5 and 8.5, followed by the addition of an acid product to keep the pH between 5 and 6.5 if it is desired to obtain solutions of urea-formaldehyde adhesive which are subsequently to be stored after cooling.
8. A process as claimed in claim 1, wherein in stage h) the formaldehyde solution is mixed with a smaller proportion of urea at a pH maintained between 8 and 9 if it is desired to obtain highly stable concentrated solutions or urea-formal-dehyde.
9. A process as claimed in claims 1, 7, or 8, which is carried out in batchwise manner.
CA251,702A 1975-05-13 1976-05-03 Process for the production of urea-formaldehyde adhesives or resins and products obtained thereby Expired CA1070889A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
FR7514794A FR2311048A1 (en) 1975-05-13 1975-05-13 PROCESS FOR PREPARATION OF UREE-FORMALDEHYDE GLUES OR RESINS AND PRODUCTS OBTAINED BY IMPLEMENTATION OF THIS PROCESS

Publications (1)

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CA1070889A true CA1070889A (en) 1980-01-29

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CA251,702A Expired CA1070889A (en) 1975-05-13 1976-05-03 Process for the production of urea-formaldehyde adhesives or resins and products obtained thereby

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JP (1) JPS5856368B2 (en)
AR (1) AR213286A1 (en)
AT (1) AT350695B (en)
AU (1) AU503309B2 (en)
BE (1) BE841663A (en)
BR (1) BR7602981A (en)
CA (1) CA1070889A (en)
CH (1) CH614454A5 (en)
DE (1) DE2606269C3 (en)
ES (1) ES447890A1 (en)
FR (1) FR2311048A1 (en)
GB (1) GB1536011A (en)
IT (1) IT1065986B (en)
MX (1) MX144145A (en)
NL (1) NL165726C (en)
SE (1) SE430897B (en)
SU (1) SU940642A3 (en)
ZA (1) ZA762576B (en)

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
ES2010959A6 (en) * 1989-05-10 1989-12-01 Patentes Novedades Sa Method for producing stabilized solutions of formaldehyde with methanol.
ES2171152B1 (en) * 2001-02-16 2003-10-01 Patentes Novedades Sa PROCEDURE FOR SEPARATION OF A WATERY MIXTURE OF TRIOXAN AND FORMALDEHYDE AND CORRESPONDING APPLICATIONS.
GB201502893D0 (en) * 2015-02-20 2015-04-08 Johnson Matthey Plc Process
GB201502894D0 (en) 2015-02-20 2015-04-08 Johnson Matthey Plc Process

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US23174A (en) * 1859-03-08 Improvement in corn-harvesters

Also Published As

Publication number Publication date
FR2311048B1 (en) 1979-04-27
DE2606269A1 (en) 1976-11-18
MX144145A (en) 1981-09-02
NL165726C (en) 1981-05-15
FR2311048A1 (en) 1976-12-10
JPS5856368B2 (en) 1983-12-14
BE841663A (en) 1976-11-10
ES447890A1 (en) 1977-07-16
IT1065986B (en) 1985-03-04
JPS51139895A (en) 1976-12-02
ATA347676A (en) 1978-11-15
SE7605413L (en) 1976-11-14
GB1536011A (en) 1978-12-13
DE2606269B2 (en) 1980-12-11
NL7601572A (en) 1976-11-16
AU1334376A (en) 1977-11-03
SU940642A3 (en) 1982-06-30
DE2606269C3 (en) 1982-09-02
NL165726B (en) 1980-12-15
BR7602981A (en) 1977-06-07
CH614454A5 (en) 1979-11-30
ZA762576B (en) 1977-04-27
SE430897B (en) 1983-12-19
AU503309B2 (en) 1979-08-30
AR213286A1 (en) 1979-01-15
AT350695B (en) 1979-06-11

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