JP2010047503A - Method for producing isocyanate mixture - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing an isocyanate mixture reduced in the content of a metal affecting the reactivity of the isocyanate mixture. <P>SOLUTION: There is provided the method for producing the isocyanate mixture C, having a reaction process for introducing an amine mixture A, phosgene B and an inactive solvent into a reaction vessel 10 and reacting the amine mixture A with the phosgene B to synthesize the isocyanate mixture, and a concentration process for concentrating the reaction process liquid comprising the isocyanate mixture, an inactive solvent and an acidic compound such as the by-produced hydrogen chloride or the excessive phosgene in a concentration vessel 20 to distill away the inactive solvent and the acidic compound from the reaction process liquid, wherein the reaction is performed in a condition for refluxing the inactive solvent in the reaction process, and at least one part of the inactive solvent distilled away is again returned to the concentration vessel 20 in the concentration process, characterized in that at least one of the refluxed inactive solvent and the inactive solvent again returned to the concentration vessel 20 is treated with an adsorbents 13A or 23A, before introduced into the vessel 10 or 20. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing an isocyanate mixture, and more particularly to an efficient method for producing an isocyanate mixture having a low metal content.

  The process for producing an isocyanate mixture includes a condensation process for synthesizing an amine mixture by condensing aniline and formaldehyde in the presence of an acid catalyst, or a process for obtaining an amine mixture by a hydrogenation reaction of a nitro compound or a nitrile compound. Alternatively, a reaction step of substantially synthesizing an isocyanate mixture by reacting an amine mixture obtained by a hydrogenation reaction or the like with phosgene in an inert solvent, and the above reaction with the inert solvent used in the isocyanate mixture and the reaction step. Concentration step for separating the isocyanate mixture, the inert solvent and the acidic compound from the reaction step liquid consisting of by-produced hydrogen chloride and / or excess acidic compound such as phosgene and recovering the inert solvent and acidic compound, and the isocyanate mixture Refining process to separate the distillate and the residue by distillation Consisting of.

The industrial production process of the isocyanate mixture is generally performed using metal equipment mainly composed of iron or stainless steel in terms of cost and maintenance.
In regular repairs of this manufacturing facility, etc., equipment and piping are opened and inspected, so that the metals that make up them come into contact with oxygen in the air and are oxidized to form metal oxides, for example, iron. It remains in the manufacturing process as iron.
The metal oxide remaining in the production process is insoluble in the isocyanate mixture.

However, as mentioned above, there are acidic compounds such as hydrogen chloride and surplus phosgene produced as a by-product in the reaction of the amine mixture and phosgene during the production of the isocyanate mixture, and these cause the production system, particularly the reaction process and the concentration process. Has an acidic atmosphere, and the metal oxide exposed to the acidic atmosphere changes to a metal chloride that is easily dissolved in the isocyanate mixture.
As a result of the metal equipment being corroded or eroded by the acidic compound in this way, a trace amount of metal, particularly iron, is dissolved in the reaction process liquid and mixed into the isocyanate mixture as the final product.

Moreover, the reaction process liquid containing an isocyanate mixture will be in an acidic state by an acidic compound as mentioned above. When the solvent is refluxed in this state, the reflux equipment is corroded and / or eroded by the acid, and metal components such as iron are mixed in the solvent. As a result, since the solvent returns to the reaction step (reaction tank) in a state containing the metal from the reflux facility, the metal content in the reaction step liquid is further increased.
On the other hand, in the concentration step, part of the recovered solvent is returned to the concentration step again in order to prevent the yield from being lowered due to the isocyanate mixture accompanying the solvent separated from the reaction step solution. However, since this solvent is also in an acidic state, the metal dissolves into the solvent due to corrosion of the equipment as described above, and returns to the concentration step together with the solvent. For this reason, also in this case, the metal content in the concentrated liquid containing polyisocyanate is further increased.

If the amount of iron contained in the isocyanate mixture is increased, the storage stability of the isocyanate mixture may be affected.
Moreover, although the isocyanate mixture is used as a starting material of polyurethane, the reactivity of the isocyanate mixture with a polyol compound or the like is affected by the amount of iron contained in the isocyanate mixture.
Furthermore, when by-products such as water produced by the reaction between the acidic compound and the metal oxide are mixed in the isocyanate mixture, it may cause modification and alteration.
For the above reasons, it is desirable that the iron content in the isocyanate mixture is as low as possible.

Generally, if the iron content in the isocyanate mixture is 10 ppm or less, it is said that the storage stability of the isocyanate mixture and the reactivity when used as a raw material for producing polyurethane are not adversely affected.
In this respect, the iron content contained in the isocyanate mixture obtained by the above production process is usually 10 ppm or less, which greatly affects the storage stability of the isocyanate mixture and the reactivity when used as a polyurethane production raw material. is not.
However, in the isocyanate mixture obtained immediately after resuming production after carrying out periodic repairs of the equipment, the iron content may reach several hundred ppm, its storage stability and reactivity with polyol compounds, etc. May be adversely affected.

In view of the above problems, various techniques have been developed for the purpose of reducing the amount of iron contained in the isocyanate mixture.
For example, Patent Document 1 discloses a method of treating diphenylmethane diisocyanate or diphenylmethane polyisocyanate with a microporous adsorbent having an internal surface area of at least 100 m ² / g.
Patent Document 2 discloses a technique for treating an organic polyisocyanate composition with a basic adsorbent.

However, although the technique of Patent Document 1 can reduce the iron content in the isocyanate mixture to a level that does not cause a problem in practice, it introduces a new problem that the microporous adsorbent is mixed in the isocyanate mixture.
Further, in the method of Patent Document 2, since a basic adsorbent is used, there is a concern about modification and alteration of the organic polyisocyanate composition after treatment, and there is a problem in storage stability.

On the other hand, removal of metals in hydrocarbons using an adsorbent is known, and various techniques are disclosed.
For example, Patent Document 3 discloses a method for removing mercury contained in hydrocarbon oils such as naphtha and condensate oil, which are mixed base materials for petroleum products, using activated carbon.
Patent Documents 4 and 5 disclose a method in which water or a chlorine-containing compound is added to a hydrocarbon oil containing heavy metal to remove the heavy metal by the porous adsorbent.
Patent Document 6 discloses a method of adsorbing and removing heavy metal by adding a chelating agent to hydrocarbon oil containing heavy metal and bringing it into contact with activated carbon.
However, these methods are not efficient because it is necessary to modify heavy metals using additives such as chlorine-containing compounds, chelating agents, and water.
Japanese Patent No. 3881046 JP 2006-160684 A Japanese Patent Laid-Open No. 10-195456 Japanese Patent Laid-Open No. 11-50065 Japanese Patent Laid-Open No. 11-50066 JP-A-5-86373

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a method for producing an isocyanate mixture in which the amount of mixed metals including iron is reduced, which affects the reactivity of the isocyanate mixture. To do.

  As a result of intensive studies in order to achieve the above object, the present inventor has recovered an inert organic solvent refluxed in the reaction step or a concentration step in a general isocyanate mixture production step, and again enters the concentration step. The present inventors have found that the metal content in the isocyanate mixture as the final product can be efficiently reduced by treating the returned inert organic solvent with an adsorbent, thereby completing the present invention.

That is, the present invention
1. A reaction step of introducing an amine mixture, phosgene and an inert solvent into the reaction vessel and reacting the amine mixture and phosgene to synthesize an isocyanate mixture, and the isocyanate mixture, the inert solvent, and the chloride formed as a by-product by the reaction. A concentration step of concentrating a reaction step liquid comprising an acidic compound such as hydrogen and / or excess phosgene in a concentration tank to distill off the inert solvent and the acidic compound from the reaction step solution, In the method for producing an isocyanate mixture, the reaction is performed under a condition where the inert solvent is refluxed, and in the concentration step, at least a part of the distilled inert solvent is again returned to the concentration tank. And at least one of the refluxing inert solvent and the inert solvent returned back into the concentration tank is Method for producing isocyanate mixtures, characterized in that it is treated with an adsorbent prior to being introduced into les in the tank,
2. A process for producing one isocyanate mixture, wherein both the refluxing inert solvent and the inert solvent returned back into the concentration tank are treated with an adsorbent before being introduced into the respective tank;
3. A process for producing an isocyanate mixture of 1 or 2, wherein the treatment with the adsorbent is performed by passing the inert solvent through a packed column packed with the adsorbent;
4). The method for producing an isocyanate mixture according to any one of 1 to 3, wherein the adsorbent is activated carbon, activated clay, or zeolite,
5). A method for producing an isocyanate mixture of 4, wherein the adsorbent is activated carbon;
6). The method for producing an isocyanate mixture according to any one of 1 to 5, wherein the adsorbent has an average particle diameter of 0.01 to 20 mm,
7). Provided is a method for producing an isocyanate mixture according to any one of 1 to 6, wherein the treatment temperature with the adsorbent is 20 to 200 ° C.

According to the present invention, in the method for producing an isocyanate mixture, at least one of the inert solvent refluxed in the reaction step and the inert solvent returned to the concentration step is treated with the adsorbent before returning to the reaction vessel or the concentration vessel. As a result, the amount of metal mixed into the reaction tank or the concentration tank from other equipment is reduced, and as a result, the amount of metal mixed into the isocyanate mixture can be greatly reduced.
For this reason, there exists an advantage that work processes, such as adjustment (reduction) of iron content required when using as a polyurethane raw material, become unnecessary.
Moreover, unlike the method of Patent Document 1 described above, since the isocyanate mixture itself is not a method of treating with an adsorbent, the adsorbent is not mixed into the final product isocyanate mixture.

Hereinafter, the present invention will be described in more detail.
The method for producing an isocyanate mixture according to the present invention includes an amine mixture, phosgene and an inert solvent introduced into a reaction vessel, and a reaction step of reacting the amine mixture and phosgene to synthesize an isocyanate mixture, and the isocyanate mixture, inert A concentration step of concentrating a reaction step liquid consisting of a solvent and an acidic compound such as hydrogen chloride and / or excess phosgene produced by the above reaction in a concentration tank to distill off the inert solvent and the acidic compound from the reaction step solution; In the reaction step, the reaction is performed under a condition where the inert solvent is refluxed, and in the concentration step, at least a part of the distilled inert solvent is returned again into the concentration tank. Wherein at least one of the refluxing inert solvent and the inert solvent returned back into the concentration tank is It is intended to be processed by the adsorbent prior to being introduced into the tank.

In other words, in order to prevent the mixing of metals such as iron into the isocyanate mixture, which affects the reactivity of the isocyanate mixture, the solvent containing the metal refluxed in the reaction step, and the isocyanate mixture separated in the concentration step At least one of the solvent containing the metal recovered and returned to the concentration step is treated with an adsorbent.
At this time, the treatment with the adsorbent (hereinafter referred to as adsorption treatment) can reduce the amount of metal mixed in the isocyanate mixture only on the reaction step side or on the concentration step side, but the amount of the mixture is more effective. In view of reducing the amount, it is preferable to adsorb both the inert solvent refluxed in the reaction step and the inert solvent returned to the concentration step before returning to the respective tanks.
Moreover, the frequency | count of the adsorption process in a reaction process and a concentration process is arbitrary, Each may be 1 time or multiple times.

The method for the adsorption treatment is not particularly limited, and may be a method in which an adsorbent is added to each solvent, or a method in which each solvent is passed through a packed column or column packed with the adsorbent. However, when the latter method is used, there is an advantage that it can be incorporated into a production line and processed continuously.
In addition, when using a method of passing a solvent through a packed tower or column, when performing the adsorption treatment a plurality of times, both the serial processing in which the packed tower and column are arranged in series, and the parallel processing in which they are arranged in parallel, A combination of these may be used.

The adsorbent used in the present invention is not particularly limited as long as it is a microporous adsorbent capable of adsorbing metals such as iron, chromium, nickel and molybdenum contained in the solvent during the production process, particularly iron. .
Examples of such a microporous adsorbent include activated carbon, carbon fiber, activated clay, zeolite, silica gel and the like. Among these, activated carbon, activated clay, and zeolite are preferable in view of metal adsorption ability and cost, and activated carbon is particularly optimal.

Although the average particle diameter of the said adsorbent is not specifically limited, 0.01-20 mm is preferable, 0.05-20 mm is more preferable, 0.1-20 mm is still more preferable. When the average particle size is 0.01 mm or less, clogging is likely to occur when processing is performed using the packed tower described above or when the adsorbent is filtered, and the processing efficiency may be significantly reduced. On the other hand, if it is 20 mm or more, the specific surface area of the adsorbent becomes small, and the metal adsorption ability may be insufficient.
The average particle diameter can be measured by a known method. For example, activated carbon can be measured according to JIS K 1474. Further, a sieving method, a light scattering method, or the like can be used.
The average particle diameter in the present invention is a value measured by a sieving method for activated carbon for JIS K 1474 and other adsorbents.

In addition, the water contained in the adsorbent may be mixed with the solvent in contact with the adsorbent and introduced into the reaction process or the concentration process together with the solvent. For this reason, the water content in the adsorbent is preferably 5% by mass or less, more preferably 3% by mass or less.
The moisture contained in the adsorbent may be removed by a known technique in advance before use, or may be removed simultaneously with the removal of moisture in the process of producing the isocyanate mixture after filling in a packed tower or the like.
The water content can be measured by a known method. For example, it can be measured using a loss on drying method or an infrared moisture meter which is an official standard measurement method.
The water content in the present invention is a value measured by the loss on drying method.

Although the amount of adsorbent used varies depending on the particle size of the adsorbent and the amount of metal in the solvent, it cannot be specified unconditionally, but it is possible to treat 100 to 10,000 kg of inert solvent, preferably 100 to 5000 kg per kg of adsorbent. preferable.
The processing temperature is 20 to 200 ° C., preferably 50 to 200 ° C., and the processing pressure is 0.01 to 5 MPa, preferably 0.03 to 3 MPa. The treatment time is 1 to 200 minutes, preferably 1 to 120 minutes.
By the adsorption treatment described above, the production amount of an isocyanate mixture containing 10 ppm or more of metal, particularly iron, is reduced.

As described above, the method for producing an isocyanate mixture according to the present invention is characterized in that the solvent refluxed in the reaction step and / or the solvent reused in the concentration step is adsorbed, so that the other steps are conventionally known. This is the same as the above method.
Examples of the isocyanate mixture include aliphatic diisocyanate mixtures such as hexamethylene diisocyanate (HDI); alicyclic diisocyanate mixtures such as isophorone diisocyanate; aromatic isocyanate mixtures such as toluene diisocyanate (TDI) and diphenylmethane diisocyanate (MDI), and the like. Depending on these, a suitable amine mixture is used.
Among them, an MDI mixture in which the influence of iron is particularly problematic, specifically, 20 to 70% by mass of an isocyanate having two benzene rings and two isocyanate groups in one molecule, and a benzene ring and an isocyanate group in one molecule. It is effective to use the method of the present invention for an MDI mixture containing 80 to 30% by mass of an isocyanate-based multinuclear condensate having 3 or more of each.

The inert solvent is arbitrary as long as it is generally used for the production of isocyanate mixtures, and benzene, toluene, xylene, chlorobenzene, dichlorobenzene, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, butyl acetate, cyclohexane, etc. are used. be able to.
After the concentration step, it can be purified by a conventional method such as distillation to obtain a pure isocyanate mixture (purification step).
In addition, what is necessary is just to employ | adopt conventionally well-known conditions suitably for other manufacturing conditions, for example, conditions, such as phosgenation reaction conditions, concentration conditions, and distillation conditions, according to the isocyanate mixture to manufacture.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a production apparatus 1 used in the method for producing an isocyanate mixture of the present invention.
In this production apparatus 1, the amine mixture A and phosgene B are introduced into the reaction vessel 10 together with chlorobenzene, which is an inert solvent, and a phosgenation reaction is performed under heating and reflux conditions (reaction step).
At this time, the chlorobenzene is sent to the first heat exchanger 11 together with the hydrogen chloride produced as a by-product from the reaction of the amine mixture A and phosgene B, and the excess acidic compound such as phosgene B, and then the first solvent recovery tank. 12 is recovered.

The recovered chlorobenzene and acidic compound are introduced from the lower part of the first adsorbent packed tower 13 packed with 500 kg of activated carbon 13A having an average particle diameter of 2 mm, and are adsorbed by the activated carbon 13A (liquid passing speed 60 kg / Min, processing temperature 80 ° C.). By this treatment, metal components such as iron eluted in chlorobenzene from the heat exchanger 11 and the recovery tank 12 due to corrosion and erosion by acidic compounds are removed.
The chlorobenzene after the adsorption treatment is discharged from the upper part of the first adsorbent packed tower 13 and returned to the reaction vessel 10 again.

After completion of the reaction process, the produced reaction mixture containing the isocyanate mixture, acidic compound and chlorobenzene is sent to the concentration tank 20 and concentrated (concentration process).
The chlorobenzene and acidic compound distilled off in this step are sent to the second heat exchanger 21 and then recovered in the second solvent recovery tank 22.
The recovered chlorobenzene and acidic compound are introduced from the lower part of the second adsorbent packed tower 23 packed with 500 kg of activated carbon 23A having an average particle diameter of 2 mm, and are adsorbed by the activated carbon 23A in the same manner as in the reaction step. (Flow rate 60 kg / min, treatment temperature 80 ° C.). By this treatment, metal components such as iron eluted in chlorobenzene from the heat exchanger 21 and the recovery tank 22 due to corrosion and erosion by acidic compounds are removed.
The chlorobenzene after the adsorption treatment is discharged from the upper part of the second adsorbent packed tower 23 and returned to the concentration tank 20 again.
After completion of the concentration step, the crude isocyanate mixture is sent to the distillation column 30, where it is separated and purified from a low-boiling compound or the like that is a distillate, and an isocyanate mixture C is obtained as a residue (purification step).

In the above embodiment, the adsorption process is performed only once in the reaction step and the concentration step, but the present invention is not limited to this.
That is, a plurality of adsorbent packed towers can be provided and subjected to adsorption treatment a plurality of times. In this case, the plurality of packed towers may be arranged in series or in parallel.
Further, the liquid passing speed and the treatment temperature during the adsorption treatment are not limited to the above values, and can be set as appropriate.
Furthermore, although the reaction process and the concentration process were performed in separate tanks, they can be performed in the same tank, that is, the concentration process can be performed in the reaction tank.
In addition, the configuration of the manufacturing equipment, the manufacturing conditions, and the like can be appropriately changed as long as the object of the present invention can be achieved.

EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated more concretely, this invention is not limited to the following Example.
In the following Examples, the iron content was measured using an atomic absorption photometer (AA-6800, manufactured by Shimadzu Corporation). Unless otherwise specified, all temperatures are in degrees Celsius and all percentages are in weight percent.

[Example 1]
Polymethylene polyphenyl polyamine and phosgene B, which are the amine mixture A, were introduced into the reaction vessel 10 together with chlorobenzene, and a phosgenation reaction was performed according to a conventional method. Subsequently, the reaction process liquid after phosgenation was introduced into the concentration tank 20, and excess phosgene, by-produced hydrogen chloride and chlorobenzene were separated from the isocyanate mixture to obtain an isocyanate mixture. Subsequently, this concentrated liquid was introduced into the distillation column 30, and an MDI mixture C was obtained by separating a distillate and a residue by distillation.
At this time, the first adsorbent packed tower 13 and the second adsorbent packed tower 23 are filled with 500 kg of activated carbon (activated carbon KW manufactured by Kuraray Chemical Co., Ltd., average particle diameter 2 mm, water content 3.0 mass%), respectively, and chlorobenzene (Iron content 50 ppm) was adsorbed through the first adsorbent packed tower 13 and the second adsorbent packed tower 23 at 80 ° C. and 60 kg / min.

When said manufacture was performed continuously for 6 days, iron content was not detected in the chlorobenzene which returns to the reaction tank 10 and the concentration tank 20 after the adsorption | suction process six days later.
And the manufacturing amount of the MDI mixture which contains iron content 10ppm or more in 6 days was 30% of the total manufacturing amount, and the average content of iron in the total MDI mixture manufactured in 6 days was 12 ppm.

[Example 2]
An isocyanate mixture was produced in the same manner as in Example 1 except that activated carbon (spherical activated carbon manufactured by Kureha Co., Ltd., average particle diameter 1 mm, water content 2.9% by mass) was used.
As a result, the production amount of the MDI mixture containing 10 ppm or more of iron in 6 days was 30% of the total production amount, and the average iron content in all MDI mixtures produced in 6 days was 12 ppm.

[Example 3]
An isocyanate mixture was produced in the same manner as in Example 1 except that activated carbon (Kuraray Chemical 4GS, Kuraray Chemical Co., Ltd., average particle size 4 mm, water content 3.0 mass%) was used.
As a result, the production amount of the MDI mixture containing 10 ppm or more of iron in 6 days was 40% of the total production amount, and the average iron content in all MDI mixtures produced in 6 days was 15 ppm.

[Example 4]
An isocyanate mixture was produced in the same manner as in Example 1 except that activated carbon (Tsurumi Coal 4GV manufactured by Turumi Coal Co., Ltd., average particle diameter 4 mm, water content 3.0 mass%) was used.
As a result, the production amount of an MDI mixture containing 10 ppm or more of iron in 6 days was 40% of the total production amount, and the average iron content in all MDI mixtures produced in 6 days was 15 ppm.

[Example 5]
An isocyanate mixture was produced in the same manner as in Example 1 except that activated carbon (Kuraray Chemical 7GS, Kuraray Chemical Co., Ltd., average particle diameter 7 mm, water content 2.4 mass%) was used.
As a result, the production amount of the MDI mixture containing 10 ppm or more of iron in 6 days was 50% of the total production amount, and the average iron content in all MDI mixtures produced in 6 days was 20 ppm.

[Example 6]
The same treatment as in Example 1 was performed except that the chlorobenzene containing 50 ppm of iron was not treated in the first adsorbent packed tower 13 and returned to the reaction vessel 10 as it was.
As a result, the production amount of the isocyanate mixture containing 10 ppm or more of iron in 6 days was 50% of the production amount of the total isocyanate mixture, and the average content of iron in the total isocyanate mixture produced in 6 days was 18 ppm. It was.

[Example 7]
The same treatment as in Example 1 was performed except that the chlorobenzene containing 50 ppm of iron was not treated in the second adsorbent packed tower 23 and returned to the concentration tank 20 as it was.
As a result, the production amount of the isocyanate mixture containing 10 ppm or more of iron in 6 days was 60% of the production amount of the total isocyanate mixture, and the average content of iron in the total isocyanate mixture produced in 6 days was 25 ppm. It was.

[Example 8]
Example except that activated clay (made by Mizusawa Chemical Co., Ltd., galeonite, particle size 2 mm, water content 3.0 mass%) was packed in the first adsorbent packed tower 13 and the second adsorbent packed tower 23 instead of the activated carbon. 1 was performed.
As a result, the production amount of the isocyanate mixture containing 10 ppm or more of iron in 6 days was 50% of the production amount of the total isocyanate mixture, and the average content of iron in the total isocyanate mixture produced in 6 days was 18 ppm. It was.

[Example 9]
Except that the first adsorbent packed tower 13 and the second adsorbent packed tower 23 were packed with zeolite (manufactured by Tosoh Corporation, HSZ-930-HOA, particle size 2 mm, water content 2.9 mass%) instead of activated carbon. The same processing as in Example 1 was performed.
As a result, the production amount of the isocyanate mixture containing 10 ppm or more of iron in 6 days was 40% of the production amount of the total isocyanate mixture, and the average content of iron in the total isocyanate mixture produced in 6 days was 15 ppm. It was.

[Comparative Example 1]
The chlorobenzene was not treated in the first adsorbent packed tower 13 and the second adsorbent packed tower 23, and was returned to the reaction tank 10 and the concentration tank 20 as they were to produce an MDI mixture.
As a result, the production amount of the MDI mixture containing 10 ppm or more of iron in 6 days was 90% of the total production amount, and the average iron content in all MDI mixtures produced in 6 days was 100 ppm.

It is a schematic block diagram of the apparatus used for the manufacturing method of the isocyanate mixture which concerns on one Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Isocyanate mixture manufacturing apparatus 10 Reaction tank 13 1st adsorbent packed tower 20 Concentration tank 23 2nd adsorbent packed tower 13A, 23A Adsorbent 30 Distillation tower A Amine mixture B Phosgene C Isocyanate mixture

Claims (7)

A reaction step of introducing an amine mixture, phosgene and an inert solvent into the reaction vessel and reacting the amine mixture and phosgene to synthesize an isocyanate mixture, and the isocyanate mixture, the inert solvent, and the chloride formed as a by-product by the reaction. A concentration step of concentrating a reaction step solution composed of an acidic compound such as hydrogen and / or excess phosgene in a concentration tank to distill off the inert solvent and the acidic compound from the reaction step solution,
In the reaction step, the reaction is performed under a condition in which the inert solvent is refluxed, and in the concentration step, at least a part of the distilled inert solvent is again returned to the concentration tank. A manufacturing method of
A process for producing an isocyanate mixture, wherein at least one of the refluxing inert solvent and the inert solvent returned to the concentration tank is treated with an adsorbent before being introduced into the tank.   The method for producing an isocyanate mixture according to claim 1, wherein both the refluxing inert solvent and the inert solvent returned again into the concentration tank are treated with an adsorbent before being introduced into the respective tanks.   The process for producing an isocyanate mixture according to claim 1 or 2, wherein the treatment with the adsorbent is carried out by passing the inert solvent through a packed tower packed with the adsorbent.   The method for producing an isocyanate mixture according to any one of claims 1 to 3, wherein the adsorbent is activated carbon, activated clay, or zeolite.   The method for producing an isocyanate mixture according to claim 4, wherein the adsorbent is activated carbon.   The method for producing an isocyanate mixture according to any one of claims 1 to 5, wherein an average particle diameter of the adsorbent is 0.01 to 20 mm.   The processing temperature with the said adsorption agent is 20-200 degreeC, The manufacturing method of the isocyanate mixture of any one of Claims 1-6.

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