DE1950784A1 - Process for the production of isocyanates - Google Patents

Description

Folder 22030 ICI CASE D ₀ 21414

DESCRIPTION

to the patent application of

IMPERIAL CHEMICAL INDUSTRIES LIMITED, London SW _n 1 / ENGLAND,

concerning:

"Process for the production of isocyanates"

PRIORITY: Oct 8, 1968 - UK

The invention relates to the production of organic mono- and polyisocyanates from organic amines and Polyamines through a phosgenation process »

The production of organic isocyanates by phosgenation of amines and polyamines is well known.

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The process can be carried out batchwise or continuously will. Each procedure includes an initial stage, at the the anine or the polyamine and the phosgene with each other be brought into contact. Competing reactions can occur in this first stage, resulting in the final yield the isocyanate or polyisocyanate is strongly influenced »

Typical reactions of the amine group are given below, that can take place during the initial mixing stage:

(1) - HH ₂ + COCl ₂ -> - HHCOCl + HCl

(2) - HH ₂ + HCl> - HH ₂ HCl

(3) -NHCOCl -> - NCO + ECl

(4) - HH ₂ + - HCO - ■> - HHCOHH -

Reaction (1), the formation of Carbamylchlorifi _r and reaction (3)> the decomposition of carbamyl chloride, whereby isocyanate is formed, are both rapid reactions that proceed sufficiently quickly that reactions (2) and (4), in which the Products of reactions (1) and (3) undergo reaction almost instantaneously when the polyamine and phosgene are mixed together.

Reaction (2) is somewhat undesirable because, although the amine hydrochloride group can be converted to the isoyanate group by hot phosgenation, it is essential that the amine hydrochloride be in a fine physical form unless the phosgenation is uncommon.

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1 I should take a long time, which is particularly important in the context of a continuous process ₀

Coarse Amnhydrochlorid phosgenated in the hot stage of the process Uichi only slow but it can participate even at high temperatures in a further undesirable reaction showing the formation of urea groups has the consequence j vile z, B ..

(5) ■ - HHg · HCl + COOl ₂ - $ - - HCO + 3HOl

(6) - IIH ₉ ⁰ HCl + - HCO - "- HE" CO.HE - + HCl

The reactions (4) and (6) are extremely unruly because substituted urea groups _? once they have formed , only react very slowly and incompletely with phosgene to form isocyanate as follows:

(7) - 2JHC0HH - + GOCl ₂ - £ 2-HGO + 2HCl

Substituted ureas also react with phosgene and Chlorv ^r on Hydrogen, which small but significant amounts of products are formed, the chlorine contained These contaminants may be responsible, in both of which in the finished Isocyjinatprodukt resistant and for a high acidity and a high content of chlorine hydrol3'sierbarem can detrimentally affect the technical application of the Isoeyanatproö.ukts.

The formation of urea groups is therefore from both Point of view of the yield as well as the quality of the desired

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- 4 product undesirable «,

In order to obtain optimal conditions for the formation of polyisoeyanate in good yield, it is essential that the following conditions are met in the initial phosgenation mixing stage:

a) A high phosgene concentration must be in the reaction zone be present in order to promote the reaction (1) and to slow down the reaction (4).

b) Any amine hydrochloride formed as a result of reaction (2) must be in a satisfactory physical state Form so that it can easily react with phosgene in the subsequent hot stage. It was found, that freshly made amine hydrochloride quickly becomes coarser and therefore there must be a delay between its initial formation during the cold stage and its subsequent phosgenation at the hot stage if possible be kept short.

c) Contact of the free amine with free isocyanate groups must be avoided as much as possible to get an education to prevent urea groups by reaction (4).

It has now been found that these conditions can be met in the first reaction when phosgene with a solution of an amine or a polyamine in an inert solvent is set and the solution of the amine or polyamines are in the form of a forward flowing stirred film with little or no backmixing ensures. The product of this first stage consists essentially of a mixture of isocyanate amine hydrochloride, Garbamyl chloride, phosgene, hydrogen chloride and solvents;

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"Κ -

it is another essential feature of the present process that this mixture be fed directly into a hot reactor is introduced »

Ss has been found that by using the amine or Polyamine solution in the form of a forward-flowing stirred IPilins the reaction both on the surface and in the Dissolution takes place, due to the dissolution of phosgene, and that the stirring of the film, its surface / volume ratio is much larger than a normal reaction vessel, not just a rapid dissolution of the Phosgene supports but also allows easy escape of hydrogen chloride and that through the reaction (2) amine hydrochloride formed in a very fine physical Form which is particularly suitable for phosgenation results. The reaction in a forward flowing Film removes any isocyanate formed from the fresh amine and thus prevents these two from reacting accordingly Reaction (4), whereby undesired ureas are formed.

It has also been found that in the process according to the invention it is possible to use higher polyamine concentrations, than they have hitherto been found useful; it was also found that the process works for polyamines suitable, which in the previous processes in the first treatment with phosgene practically immovable pulps revealed.

Thus, according to the invention, a method for continuous Preparation of organic isocyanates by phosgenation of organic amines or polyamines proposed, which is characterized in that in a first stage an excess of phosgene with an amine or polyanine in solution in an inert solution

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sets, with the amin or polyamine in the form of a forward flowing, stirred film of a solution of the amine or polyamine is in an inert solvent and the product of this first stage is fed directly into a bite reactor is discharged.

The forward flowing stirred film of the amine or polyamine solution can be created by a number of methods. So one can let the solution flow downwards on an inclined surface, or one can pressurize the lies behind the liquid, the film is also above its horizontal one Let the surface flow »The film is stirred to a certain extent by the mere flow, but he can also be continued mechanically or by generating turbulence be stirred in the atmosphere above the film.

It has been found that the inner surface of a cylindrical tube is a particularly suitable surface represents on which the film of the amine solution can be formed. The pipe can be horizontal or can be a Have an angle to the horizontal, an angle of less than 30 ° is preferred.

The amine or polyamine solution can be introduced into one end of the cylindrical tube and the desired film can be allowed to flow down the inner walls of the tube, stirring taking place inside the tube? the solution can thus be fed to the wall of the pipe and directed along a spiral path by means of blades, arms or wipers which are mounted on a rapidly rotating shaft located centrally in the pipe. The shovels? Arne or wipers can be set to pass through the liquid film, which is preferred, or they can be set to only cover the top

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Move the area of the film by walking near it. So that the amine hydrochloride formed in a very feW When the atomized state is obtained, it is preferred to take agitation within the liquid film Crush particles of the amine hydrochloride. By a rotating assembly of this type of exerted force carries any solution or broad particle that the PiIm leave, automatically return to the PiIm · The solution transforms calibrate into a pulp of fine cords during the reaction with the phosgene, and at the end of this first stage this pulp is discharged directly into a hot reactor.

The cylindrical tube can be jacketed so that cooling or heating during the phosgene / Arain- or Polyamine reaction is made possible «, of course the reaction which is exothermic? also performed adialiatically will.

In addition to at least one inlet for amine and inert solvent, at least one inlet is provided for the supply of phosgene. Urinary phosgene can be in the form of a gas? be used in liquefied form or in perm of a solution in an inert solvent. The tube can also be equipped with an outlet for the phosgene flowing back, which sinks out of the reaction and returns directly to the reactor.

In order to support a direct exit of the product from the first stage and an entry into a hot reactor, the cylindrical tube is located on the other inlets opposite side preferably open ended

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When the cylindrical tube is inclined, the Arain solution the inner surface of the pipe under the Gravity down, and when it is horizontal, then the amine feed can be pumped in, with then the introduction pressure is used to propel the film along the tube.

Pipes with tapering sides, for example in the shape of a truncated cone, can also be used »

One type of commercially available device that is used to perform the first stage of the present process is the one that can be adapted as a thin film handling device is known, although in the present case it is not essential that the film be the amine or Polyamine solution is a thin film.

A treatment device of this type used in the first stage of the method according to the invention can is a horizontal thin film treatment device with reverse taper, as indicated by the contro Company Inc., Petersham, Massachusetts, USA.

The reaction between the phosgene and the amine or PoIyamin the first stage may be carried out at any temperature!, But it is conveniently carried out between 8 and 100 ⁰ C.

The first stage can be carried out under atmospheric pressure or under superatmospheric pressure; To increase the solubility of the phosgene in the solvent, it is preferred to work at pressures of 0.175 to 17.50 kg / cm ² .

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The remainder of the phosgenation can be carried out at atmospheric pressure or at higher pressures, but ea it is clear that the hot reactor into which the product of the first stage is introduced directly is at the same Pressure as the container in which the first stage is carried out must be operated »

The residence time in the container of the first stage can be changed but it is preferably adjusted so that the greatest possible proportion of the amine supplied is distributed and has been implemented before the product passes into the hot reactor. Suitable residence times are between 2 and 10 minutes.

A direct transfer of the product from the first stage into the hot reactor can be achieved by the cylindrical tube inserted directly into the side of the reactor or that one connects it to the reactor via one wide vertical pipe connects through which the slurry can flow into the hot reactor, what if necessary supported by a screw conveyor as the pulp is thick. It is an essential feature of the invention that the passage takes place through a direct connection, and that the pulp is not through ordinary pipe connections is transferred to the hot reactor. The hot reactor should have such a capacity that when Entry of the product of the first stage this is immediately heated to the temperature of the first reactor ..

The hot reactor can be a conventional heated phosgenation vessel such as is used in the art for continuous or semi-continuous phosgenation. The hot reactor can be operated at any temperature above about 8O ⁰ C, and it

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may be one reactor in which the phosgenation is completed, or it may be the first of a chain of reactors, which are operated at a temperature above 8O ⁰ C.

Thus, after the first stage, the phosgenation can be completed by any of the processes used in technology for continuous phosgenation are known, with the size and number of reactors used is only determined by the desired throughput and the desired dwell time ο

Additional phosgene can be introduced into the hot reactor or at any later stage as needed. Phosgene recovered from the exhaust gases can be used at any stage.

After the phosgenation has ended, the end product can be used in the can be isolated raw or in the pure state by known methods «

In the drawing, a device is shown, which is suitable for office management of the method according to the invention suitable.

The invention will now be described in more detail with particular reference to the drawings, in which FIGS 2 relate to a device that is used to carry out the method according to the invention in a small scale, and Figures 3 and 4 relate to containers designed for large scale implementation Scale.

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Fig «1 is a side view of a reactor for the cold (first) stage, with a reactor attached for the hot stage.

Fig. 2 is a perspective view and a plan view of a stirrer for the cold stage reactor like it is shown in FIG.

3 and 4 are pictorial positions for reactors,

which are suitable for the implementation of the invention Process suitable on a large scale.

According to FIG. 1, the reactor for the cold or first stage has an arm Q _f which is a rope of a cross-shaped container. The arm Q is connected to a hot reactor 1 by the lower arm R. The arm Q has two inlets A and B through which the amine solution and the phosgene can be introduced. A further inlet / outlet (not shown in the drawing) connected to a reflux condenser so that phosgene reflux from the first reactor, namely arm Q, can also be provided in the upper surface of the arm Q. The vertical axes of arms Q and R are conveniently slightly offset from one another, as shown in the cross section of line XX, to facilitate the fitting of the stirrers into each arm.

A stirrer as shown in Fig. 2 is arranged with its axis on the horizontal axis of the arm Q, the blades of the stirrer being of such a length that they extend from point K to point J. The ^agitator.,: As shown in Figure 2, has a shaft made of stainless steel, wherein the steel is preferably such, the corrosion under Phosgenierungsbe-

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conditions, on which shaft two spiders G attached are »with the two spiders carrying four movable blades H made of stainless steel between them. the Blades H are attached εο that when the rotation Wave the four blades swing outward in such a way that they brush the wall of the first reactor Q and thereby a good mixture of the liquid film on it and promote turbulence in the central area of Q.

Another stirrer can be arranged vertically in the arm R. The stirrer can be the same as that explained in FIG. Alternatively, a screw can be arranged vertically in the arm R. The purpose of the stirrer or screw is to help convey the product of the first reaction in Q directly into the hot reactor I. "The initial product leaving Q" is very thick and this second stirrer or screw prevents clogging in the direct feed.

When operating the gate direction of Fig. 1, phosgene and AfflinlÖeirag introduced into the individual entrances, with the The stirrer arm Q rotates at approximately 250 to 950 rpm and the vertical agitator in arm R rotates at about 100 to 250 rpm. The reaction between the phosgene and the amine takes place as the amine solution goes along of the inner surface of the arm Q flows towards the end J, the flow rate being adjusted so that the initial or first reaction stage within this Period is over * The solution or suspension, as the case may be, runs directly from the first reactor through the Arm R into the hot reactor. The phosgenation is then completed in the hot reactor and the product becomes continuous through one of the openings 0, D or F via a

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Dip tube (not shown) withdrawn. If desired, can the product can be fed from the hot reactor into one or more additional hot reactors to convert the phosgenation into complete a series of stages.

According to Figures 3 and 4, the reactor consists of the first Step from a tapered container L, which is equipped with a stirrer »which paddles or wipers M which are driven by a motor H. In the upper surface of the tapered container L inlets for phosgene P and amine solution S are provided. Which tapered container can be jacketed and there can be a further opening can be provided in the upper surface of L to allow phosgene reflux if necessary.

In Figure 3, the tapered container L is hot Phosgenator O is attached and the outlet from the tapered container opens directly into an upper one Flange on the hot phosgenator. In the embodiment shown in Figure 4, the tapered container is on attached to the side of the hot phosgenator, and the outlet opens directly into the hot phosgenator.

Preferably, several inlets for phosgene and amine solution are provided in the tapered container. Furthermore, it is preferred that the phosgene inlets are those from the outlet into the hot phosgenator are furthest away, although this is not essential.

The containers L and M and the auxiliary devices are off Constructed materials known to resist corrosion under phosgenation conditions.

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The hot Phosgenator M is with a floor drain T or alternatively equipped with a side drain (not shown). The material withdrawn from the hot phosgenator can be worked up and isolated in the customary manner, provided the phosgenation is over, or it can, if necessary, continuously to a further phosgenator be guided. You intended for a large-scale implementation of the figures 3 and 4 is in a operated in a similar manner as the device already described for working in the small hatred.

The present invention is particularly suitable for continuous operation, but it can also be semi-continuous operation, i.e. that the first stage is carried out continuously until a hot reactor located further back filled up is; the first stage is then interrupted and the material in the latter hot reactor becomes intermittent End of phosgenation, the product is discharged and the whole operation is repeated.

Organic isocyanates and polyisocyanates which may be prepared by the inventive process are, for example aromatic, aliphatic, cycloaliphatic and araliphatic mono- and polyisocyanates and include, for example hexyl _r cyclohexyl, benzyl, phenyl, chlorophenyl and tfaphthylisocyanate, tolylene diisocyanates, especially mixtures of the 2,4- and 2,6-isomers, diphenylmethane-4 "4 ^{t-diisocyanate} and mixtures thereof containing higher functionality polyisocyanates, 3-methyldiphenylmethane diisocyanate-4-4'", meta- and para-phenylene diisocyanate , Diphenyl-4 »4'-diisooyanate, naphthalene-1,5-diisooyanate, chlorophenylene-2,4-diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexa-

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methylenediisoeyan & t, heptamethylene diisoeyanate, oetamethylene diisocyanate, ffonamethylene diisocyanate, decamethylene diisocyanate, dodecam ethyl end iisocyanate, m-xylene diisocyanate, p-Xylylene diisoeyanate, cyelohexane-ii-diisocyanate, cyclohexane-1,3-diisocyanate, methylcyclohexane-2,4- and 2,6-diisocyanate and mixtures of these, 1,3- and 1,4-bis (isocyanatomethyl) - cyclohex & n, misocyanatodicyclohexylmethane, S-isocyanatylphenyl isocyanate, α-isocyanatobenzyl isocyanate and tetranethyl-p-xylylene diisocyanate.

You are using isocyanates listed above the corresponding well-known primary amines ale Raw materials produced.

It was found that the procedure is special for the production of organic polyisocyanates, both aromatic and aliphatic polyisocyanates, suitable, with unexpectedly high yields and short Phosgewkwiungszeiten can be achieved.

The inert solvent used in the process of the invention can be any of those solvents which are already known for use in phosgenation. The term "inert" means inert among the Reaction conditions; For this reason, the solvent must of course under the reaction conditions used with respect to hydrogen chloride, phogen and amine be inert.

Examples of inert solvents are ester solvents such as e.g. n-butyl acetate, n-hexyl acetate, dimethyl carbonate and Diethyl carbonate; Hydrocarbons such as toluene and Xylene, and halogenated hydrocarbons, such as mono-, di- and trichlorobenzenes, chlorotoluenes, carbon tetrachloride

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- 16 substance and trichlorofluoromethane.

You concentration of the solution of the amine in the inert solvent, hereinafter referred to as amine solutions, can vary widely, but preference is given to »one solution to use between 4 and 1§ wt. # of the amine contains · In the present proceeding it was found that Amine and polyamine solutions containing up to 10 wt .- ^ amine or Containing polyamine, can be used well.

An excess of phosgene is always present in the first stage. Hit the phrase "excess" is an excess over is meant the amount which is ohiometrically required for a reaction with all of the amino groups present at a given time.

The invention is illustrated by the following examples, in which all parts and percentages are by weight are expressed.

example Manufacture of polyamine

465 parts of aniline, 300 parts of water and 499.5 parts of hydrochloric acid (36 #) are mixed together with thorough stirring. The temperature increases of approximately 2O ⁰ C to 60 ⁰ C. To the clear solution are added 242.4 parts of formaldehyde (36.5 50 for 30 Hinuten, whereby the temperature rises to approximately 90 ⁰ C. The resulting suspension is in one hour to 95 -.. 2 ⁰ C. and held for 3 hours at this temperature, the clear solution is cooled to 6O ⁰ C and neutralized skilled a 30 Hinuten permanent Eühren is the

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upper aqueous layer drawn off and discarded, and the lower is Polyaminechicht with three successive volumes of 330 parts of water nit 60 ⁰ C washed. The washed product is vacuum stripped (20 mm) at 115 ⁰ C erhitztt to dry it. The yield is approximately 460 ropes.

Phosgenation

400! Heal polyamide are dissolved in 600 parts Honoehlorobenzol at 60 ⁰ C. 4000 parts of monochlorobenzene at 30 ^° C. are added to the solution and, after careful mixing, the solution is filtered and continuously at a rate of 13 g / min into inlet A of the horizontal arm of the reactor for the cold stage, as shown in FIG »Pumped in. The horizontal arm of the reactor is effectively agitated using a stirrer of the type shown in Figure 2. It is set in rotation at 800 rpm. Liquid phosgene is initially introduced into inlet B at a rate of 4-5 g / min, and when steady conditions have been established, the supply of fresh phosgene is reduced to 3.5 g / min. The temperature of the reactor is 30 to 35 ⁰ C.

The thick suspension of the reaction mixture flows down the vertical arm of the cold stage reactor, which is equipped with a stirrer similar to the horizontal arm, but which rotates at 200 TJ / rain. At the lower end of the vertical arm it then enters a container with a capacity of 1000 ml and a working volume of approximately 750 al. The container is stirred moderately maintained (200 U / min) and heated to 85 ⁰ C. The contents of this reactor overflow into a collecting container, which is not shown in the drawing.

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The exhaust gases from the hot stage reactor flow through a water-cooled reflux condenser, which returns the solvent to the hot stage reactor, and then flow to the bottom of a condenser operated ^{at -5O 0 C.} The condenser separates HCl gas from phosgene which is liquefied. The latter flows back together with the fresh phosgene to inlet B in the horizontal arm of the reactor of the cold stage.

The diluted crude product flowing out of the hot stage reactor is clear and free from sediment. It is worked up in a conventional manner, the solvent being evaporated at a reduced pressure and a temperature not exceeding 140 ^° C.

The yield is 500 g of a clear pale brown liquid, the diphenylmethane-4,4'- and 2,4'-diisocyanate together with higher homologous polyphenylene polyisocyanates with methylene bridges. The product is suitable for the production of hard polyurethane foams, elastomers, Seals, plastics, Oherflächenbeläsen, adhesives and for many other purposes.

example

A solution containing 8 parts by weight 56 in o-tolylenediamine Dichiorobenzol of 70 ⁰ C is introduced into the entry B of the horizontal arm of the reactor the cold stage shown in Fig. 1,. The diamine is a mixture of isomers, rich approximately 80 f> 2.4-, 19.6 # 2.6- and 0.4 ^ 3.4- ·. Contains solylenediamine. The reactor is operated in a manner similar to Example 1. The initial feed velocity for fresh phosgene is 4.5 g / min, but

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after steady conditions have set in and a If phosgene is continuously refluxed from the hot stage reactor, the rate of fresh phosgene feed is reduced to 3.5 g / min. the The temperature of the reactor is 25 to 30 ° 0.

The cold stage reaction mixture flows through the vertical arm to the hot stage reactor, any clogging being prevented by the action of the vertical stirrer.O From the hot stage reactor, which has a working volume of 750 ml, the dilute crude tolylene diisocyanate flows to one (not shown in the diagram) receiving container. After filtration to remove a small amount of an insoluble residue, the crude isocyanate is degassed to remove phosgene and hydrogen chloride. The solvent is removed in a conventional manner under reduced pressure, and the isocyanate is distilled to produce a colorless product which approximately 80 £ Xolylen-2,4-diisocyanate and 20 $ tolylene-2,6-diisocyanate contains.

The yield is 93 #. The product is suitable in everyone Way for the production of flexible polyurethane foams, surface coverings and other products.

example Manufacture of polyamine

1116 inexpensive aniline, 160 ropes water and 367 cords hydrochloric acid (36.5 £) are mixed together "The temperature under stirring cold increases from approximately 2O ⁰ C to 53 ⁰ C. To the aqueous mixture of aniline and aniline hydrochloride are 556 parts of formaldehyde (36, 0 56) for 30 minutes

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give. The temperature rises during the Bührens and is held by applying external cooling to 75 to 80 ⁰ C, after the addition of formaldehyde to the end, the resulting suspension in 15 minutes at 95 ί 2 ⁰ C heated, and 90 minutes at this temperature held. The clear solution is neutralized by adding a solution of 150 ropes of caustic soda in 500 parts of water. After stirring for 30 minutes, the upper aqueous layer is drained off and discarded and the lower layer of the polyamine is mixed with three successive amounts of 800 parts of water at 80 ⁰ C washed.

The washed product is treated under reduced pressure (20 mm) at 115 ^° C. in a falling film evaporator in order to remove water and excess aniline.

The yield is approximately 1025 parts, Phosgenation

960 ropes of the above polyamines are dissolved in 7040 ropes monochlorobenzene at 60 ⁰ G. They clear solution is cooled to 3O ⁰ C and continuously phosgenated as described in Example 1.

The diluted product is degassed and the product is in conventionally worked up with the solvent being removed under reduced pressure.

The concentrated material is ^{heated to 195 0} C,

Maintained at this temperature for 15 minutes and quickly increased cooled below 100 ^{° C.}

The product is a clear brown liquid and possesses the following analytical seeds:

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Isocyanate value (as KDI): 89.2 j4 (calculated for an MW of

250)

4,4'-Mphenylinethane diisocyanate content: 42.3 56

2.4 ¹ -Mphenylmethane diisocyanate content: 2.3 fL

Content of hydrolyzable chlorine: 0.37Jt

Acidity (ale HCl) 0.086} C Soluble dimer content: 1.1 56

Viscosity: 281 ö / S

The product is suitable for the production of "hard, flexible and semi-flexible foams, elastomers, Sightings, plastics, surface coverings, adhesives and many other products.

PAfflSWEJUffSPBUGHE i

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Claims (8)

PA (PENTAN'S PRÜCHE 1. Process for the continuous production of organic isocyanates by phosgenation of organic Aaines or polyamines »characterized in that in a first stage an excess of phosgene and an amine or reacting polyamine in solution in an inert solvent, the amine or polyamine taking the form of a forward flowing, stirred film of a solution of the amine or polyamines in an inert solvent, whereupon the product in the first stage directly into a hot reactor transferred " 2. The method according to claim 1, characterized in that the forward flowing stirred film of a solution of the amine or polyamines is formed in an inert solvent on the inner surface of a cylindrical tube. 3 «The method according to claim 2, characterized in that the amine or polyamine solution in one end of a cylindrical tube is inserted and the desired film is conveyed along the inner walls of the tube a stirrer provided in the tube is kept flowing. 4. The method according to claim 3, characterized in that the stirrer has blades, arms or wipers, which are mounted on a rapidly rotating shaft, which is arranged centrally in the pipe. 5. The method according to claim 4t thereby marked 109816/2261 draws; that the blades, arms or critters are arranged so that they pass through the liquid film. 6. The method according to any one of claims 2 to 5 »characterized in that the cylindrical tube on the the opposite side of the entrances has an open end. 7. The method according to any one of the preceding claims, characterized in that the first stage at überat atmospheric pressure is performed. 8. The method according to any one of the preceding claims, characterized in »that a polyanine is used, and that the product is an organic polyisocyanate. 9 * Method according to one of the preceding claims characterized in that the solution of the amine or polyamine in the inert solvent is between 4 and 16 wt Contains amine or polyanine. DiPU-ING. 5.STAEGER 109816/2261 Blank page