JP2000136264A - Decomposition of solid residue - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process for converting a hitherto discarded solid residue by-produced in the production of an isocyanate into the corresponding reusable amine without adding a hydrolysis promoting agent such as an alkali. SOLUTION: A solid residue by-produced in the production of an isocyanate is converted to an amine corresponding to the component compound of the solid residue by heating the residue in the presence of a gaseous, liquid or supercritical water or a mixture of water and alcohol. Preferably, the weight loss of the solid residue after keeping at 180 deg.C for 2 hr under 20 Torr pressure is <=3% and the weight ratio of water to the solid residue is >=0.1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for hydrolyzing a solid residue by-produced during the production of isocyanate in the presence of water in a gaseous, liquid or supercritical state or a mixture of alcohol and water to produce a solid residual component compound. The present invention relates to a method for decomposing a solid residue into a corresponding amine.

[0002] The present invention also relates to a method for recovering isocyanate from a distillation residue produced as a by-product during the production of isocyanate to form a solid residue, and hydrolyzing the solid residue as described above.

[0003]

2. Description of the Related Art Generally, isocyanates are obtained by reacting an amine corresponding to the isocyanate with phosgene, subjecting the reaction product to distillation to remove by-products and tar components, respectively, to obtain a crude isocyanate. It is produced by a method of subjecting a naart to rectification to obtain a purified isocyanate. This tar component obtained as a distillation residue is formed by a side reaction in the phosgenation step and a thermal polycondensation in the distillation step, and is considered to be a mixture of complex polycondensates such as urea, biuret, carbodiimide, and isocyanurate. I have. In general, the distillation residue is further obtained by recovering the isocyanate contained therein and disposing the remainder as industrial waste, or disposing the distillation residue as it is as industrial waste.

[0004] As described above, the isocyanate distillation residue by-produced during the production of isocyanate has been conventionally disposed of as industrial waste. At the same time, studies on effective utilization have been made. However, in recent years, from the viewpoint of reducing the burden on the environment and regenerating resources, effective use of industrial waste has been actively studied.

As an example of a conventional study on the distillation residue of isocyanate, Japanese Patent Publication No. 5-79690 discloses a method in which a monohydric alcohol is added to a distillation residue of tolylene diisocyanate.
A mixture of carbamate and polyol was added,
A technique is disclosed in which a foaming agent or the like is added thereto to form a urethane foam. This method should be evaluated in terms of changing the distillation residue to a more effective value.

On the other hand, as an approach from the isocyanate production process side, attempts have been made to reduce the production cost by recovering the isocyanate further from the distillation residue, or by decomposing the distillation residue and collecting it as the corresponding amine. Has been done.

[0007] For example, JP-A-50-142501,
JP-A-54-130525 and JP-A-58-20
No. 1751 discloses that an isocyanate distillation residue is hydrolyzed in the presence of an aqueous alkali solution to obtain a corresponding amine by separating a solid content in a decomposition solution. More specifically, JP-A-50-142501 discloses the presence of at least one of water, alcohols and amines and at least one of hydroxides, oxides and amines of alkali or alkaline earth metals in the isocyanate distillation residue. Heating for 30 minutes to 5 hours with a saturated solution at a temperature of 100 to 200 ° C.,
It is disclosed to separate the precipitated solid to obtain the corresponding amine. However, these all promote the hydrolysis using alkali, and separation of precipitated solids, etc.
Since the process becomes complicated, cost increase is unavoidable and cannot be said to be an economical method.

Recently, as an improved method, Japanese Unexamined Patent Application Publication No. 9-151270 discloses a short-term method which is not expected in the prior art, that is, waste in a molten or liquid state is treated with water near a critical point for 10 minutes. It is disclosed that a target compound is decomposed in time and recovered as a corresponding raw material compound or a derivative thereof. As a feature of this technology, waste in the molten or liquid state is not used without the conventional hydrolysis accelerator,
Decomposition is performed using water alone, and decomposition is performed under conditions near the critical point of water, but the construction cost is not so high because of a short time.

However, in this method, since the waste in a molten or liquid state contains useful substances such as isocyanate which can be circulated to the production process as it is, it is hydrolyzed to correspond to the isocyanate. Converted to an amine,
It is not economical in that it must be reacted again with phosgene for reuse in the isocyanate production process.

As described above, these conventional methods are not intended for solid wastes, that is, solid residues. Ultimately, solid residues remain, and finally they must be disposed of as industrial waste. Was the current situation.

[0011]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to reuse a solid residue produced as a by-product during the production of isocyanate, which had to be disposed of before, without adding a hydrolysis accelerator such as an alkali. It is an object of the present invention to provide a possible method for converting to the corresponding amine.

Another object of the present invention is to efficiently separate the isocyanate from the distillation residue produced as a by-product during the production of the isocyanate, and to efficiently hydrolyze the resulting solid residue without adding an alkali and re-use it. It is an object of the present invention to provide a method for converting to a corresponding amine which can be used.

[0013]

The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that a solid residue produced as a by-product during the production of isocyanate is converted into gas, liquid or supercritical water or alcohol and water. By heating in the presence of the mixture, it was found that the amine can be converted to the amine corresponding to the component compound of the solid residue, and essential and suitable conditions therefor were found, and the present invention was completed.

That is, the present invention relates to a solid residue decomposition method described in the following (1) to (12). (1) The solid residue by-produced during the production of isocyanate is produced in the presence of gas, liquid or supercritical water, or a mixture of alcohol and water, at a temperature of 100 ° C. or more and a pressure of 0.1 MPa.
a. A method for decomposing a solid residue, wherein the method is heated at or above a to convert the solid residue into an amine corresponding to the component compound. (2) The method for decomposing a solid residue according to the above (1), wherein a weight loss of the solid residue when the solid residue is kept at 20 torr and 180 ° C. for 1 hour is 3% or less. (3) The solid residue decomposition method according to the above (1), wherein the weight ratio of water to the solid residue is 0.1 or more. (4) The method for decomposing a solid residue according to the above (1) or (3), wherein the molar ratio of the alcohol to water is 5 or less. (5) The pressure is 0.5 to 40 MPa, and the temperature is 1
The method for decomposing a solid residue according to the above (1), wherein the temperature is 50 to 450 ° C. (6) A volatile component is separated from a distillation residue containing a volatile component by-produced during the production of isocyanate, and the obtained solid residue is subjected to gas, liquid or supercritical water or a mixture of alcohol and water in the presence of water. , Temperature 100 ° C or higher, pressure 0.
A method for decomposing a solid residue, comprising heating to 1 MPa or more to convert the solid residue into an amine compound corresponding to the component compound. (7) The method for decomposing a solid residue according to the above (6), wherein the volatile component is separated in a two-phase flow type evaporator having a piston flow property. (8) The method for decomposing a solid residue according to (7), wherein the two-phase flow evaporator is a double tube evaporator. (9) The separation of the volatile components is performed at a temperature of 120 to 350 ° C,
The solid residue decomposition method according to the above (7) or (8), wherein the pressure is 1 to 200 mmHg, and the gas flow rate at the outlet of the two-phase flow type evaporator is 100 to 700 m / sec. (10) The solid residue decomposition method according to the above (6), wherein the weight ratio of water to the solid residue is 0.1 or more. (11) The method for decomposing a solid residue according to the above (6) or (10), wherein the molar ratio of the alcohol to water is 5 or less. (12) A distillation residue containing isocyanate, which is a by-product during the production of isocyanate, is heated in a two-phase flow type evaporator having a piston flow property to separate the isocyanate from the distillation residue and obtain a solid. Contacting the residue with gas, liquid or water in a supercritical state or a mixture of alcohol and water at a temperature of 100 ° C. or more and a pressure of 0.1 MPa or more to convert the residue into an amine corresponding to the component compound of the solid residue. A method for treating distillation residue.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a solid residue by-produced during the production of isocyanate means a residue generated during production of a compound having at least one --NCO group such as the following monoisocyanate and diisocyanate. .

Examples of the monoisocyanate include an aliphatic monoisocyanate represented by the general formula R-NCO (R is an aliphatic group or an aromatic group), an aromatic monoisocyanate, and the like.

Specific examples of the aliphatic monoisocyanate include methyl isocyanate and n-butyl isocyanate. Specific examples of the aromatic monoisocyanate include phenyl isocyanate.

The diisocyanate has the general formula OCN-
Examples thereof include an aliphatic diisocyanate, an aromatic diisocyanate, and an alicyclic diisocyanate represented by R-NCO (R is the above group or an alicyclic group).

Specific examples of the aliphatic diisocyanate include hexamethylene diisocyanate. Examples of the aromatic diisocyanate include xylylene diisocyanate, tolylene diisocyanate, naphthylene diisocyanate, and diphenylmethane diisocyanate. Examples of the alicyclic diisocyanate include isophorone diisocyanate, norbornene diisocyanate, and the like. Other than the above isocyanates, for example, three or more of-such as triisocyanate
A solid residue by-produced during the production of the isocyanate compound having an NCO group can also be used. As the solid residue used in the decomposition of the present invention, any solid residue generated in any step may be used as long as the solid residue is a by-product during the production of isocyanate. Specifically, it is a solid residue produced as a by-product in any of an amine production step, an amine-phosgene reaction step, an isocyanate purification step, and an isocyanate recovery step. These solid residues may be melted or dissolved in each step. The solid residue applicable to the present invention is not limited to isocyanate produced using phosgene, and when produced by a non-phosgene method, the solid residue produced as a by-product in any of these steps is also decomposed. It goes without saying that you can do it.

Any of the solid residues may be used, but it is usually used after the solid residues generated in each step are separated from liquid components by a solid-liquid separation step, a distillation step, or the like. The isocyanate which has passed through a purification step is preferred. In particular, when the isocyanate is purified by distillation, the distillation residue (that is, the step of purifying and distilling the isocyanate) is preferable, and the one obtained by recovering the distillation residue from the distillation residue until it contains substantially no volatile components is particularly preferable.

Here, the solid containing substantially no volatile component means a solid whose weight loss after keeping at 20 torr and 180 ° C. for 1 hour is within 3 wt%.

The solid residue by-produced during the production of the isocyanate is a mixture mainly composed of a thermal polycondensate such as an amine or an isocyanate. The thermal polycondensate has, for example, a group or a ring such as urea (urethane), biuret, carbodiimide, and isocyanurate. In particular, many compounds having a complex structure having a plurality of these groups or rings are contained. The solid residue is gaseous, liquid or supercritical water, or a mixture of alcohol and water,
It is contacted under high temperature and high pressure to hydrolyze to an amine corresponding to the component compound of the solid residue.

The decomposition process of the solid residue will be described with reference to FIG. The solid residue is supplied from a line 101 to a slurry preparation drum 102. Water is supplied from line 103. Water may contain a predetermined amount of alcohol as needed. The slurry prepared in 102 is heated by the preheat exchanger 104 and supplied to the reactor 105, and the decomposed product is extracted from 106, purified if necessary, and recycled to the isocyanate raw material and the like.

From the line 107, gas produced as a result of decomposition of the solid residue, mainly carbon dioxide, is discharged.

As described above, any solid residue may be used as long as it is a solid residue generated during the production of isocyanate. Above all, it is particularly preferable to use one obtained by separating volatile components by a two-phase flow type evaporator having a piston flow property. A solid residue substantially free of volatiles (ie,
Particularly preferred is a residue obtained by recovering the isocyanate monomer to the utmost from the residual distillation residue in the form of tens of percent of the residual isocyanate monomer to a limit, such as a thermal polycondensate composed of the by-products described above).

These solid residues are decomposed by contact with water at high temperature and high pressure. High temperature / high pressure specifically means a temperature of 100 ° C. or higher and a pressure of 0.1 MPa or higher. At this time, water is in a gas, liquid, or supercritical form depending on its temperature and pressure. In addition, water may contain an alcohol etc. alone.

When the solid residue is decomposed by contact with water at high temperature and high pressure, the solid residue is preferably in the form of fine powder in order to increase the contact interface. It is preferable to grind into pieces.

Preferred temperature and pressure conditions for decomposing the solid residue are 150 ° C. or more and 0.5 MPa or more. Although there is no particular upper limit for temperature and pressure, 450 ° C.
Hereinafter, 40 MPa or less is preferable.

The decomposition time of the solid residue is not particularly limited, but is from 1 minute to 300 minutes, preferably from 1 minute to 30 minutes after reaching a predetermined temperature.

The mixing and heating of the water and the solid residue may be performed by any of the following methods, but 3) is preferred. 1) Mix the water and the solid residue at a predetermined temperature in advance. 2) Water is heated to a predetermined temperature when mixed with the solid residue, and the heated water and the solid residue are mixed to obtain a decomposition temperature. 3) A slurry is prepared by mixing water and a solid residue in advance in a slurry preparation drum or the like to a predetermined concentration, and then heated to a decomposition temperature.

The weight ratio of water to solid residue (water / solid residue) is preferably 1/10 or more, more preferably 1/10.
2 or more. Weight ratio of water to solid residue is 1/10
If the ratio is less than 2 times, the decomposition products are not preferred because most of them are not only pitch-like residues but also the corresponding amine yields tend to be low.

In the present invention, the molar ratio of alcohol to water (alcohol / water) is preferably 5 or less, more preferably 3 or less. When the molar ratio of alcohol to water is more than 5, the yield of amine tends to be low, and a large amount of carbamate and other alcohol-derived by-products tend to be generated, which is not preferable. In the present invention, by allowing alcohol to coexist in the reaction system, the product after decomposition can be recovered as a uniform aqueous solution. By making the product after the decomposition into a uniform aqueous solution, the amine can be easily recovered from the decomposition product.

The alcohol used in the present invention is not particularly limited, but specifically, for example, methanol,
Ethanol, isopropanol, n-butanol, te
monohydric alcohols such as rt-butanol and 1-octanol; dihydric alcohols such as ethylene glycol, propylene glycol and diethylene glycol; trihydric alcohols such as trimethylolpropane and 1,2,6-hexanetriol; and tetravalent alcohols such as pentaerythritol Alcohol can be mentioned. These alcohols can be used alone or as a mixture of two or more kinds and mixed with water.

Of these alcohols, those represented by methanol, ethanol, isopropanol, ethylene glycol and propylene glycol having high solubility in water are more preferable. In the present invention, by using these alcohols in combination with water, it is possible to solubilize the pitch-like residue in the recovered material after decomposition of the solid residue.

These solid residues and water or a mixture of alcohol and water can be supplied to the reactor alone or as a slurry.

The aqueous solution obtained by decomposing the solid residue in this manner contains, as a main component, an amine corresponding to isocyanate in addition to water or alcohol and water, and, of course, the corresponding amine. Can be easily recovered by ordinary methods such as distillation and extraction.
The recovered amine is further purified, if necessary, and then circulated as a raw material to the isocyanate production step, and reacted with phosgene.

In the aqueous solution from which the amine has been separated, a light-boiling component containing carbon dioxide as a main component is dissolved. After removing this by performing steam stripping or the like, or without removing it, If desired, an alcohol may be added and then recycled as water for hydrolysis. Alternatively, the wastewater can be drained after normal wastewater treatment.

The distillation residue in the production of isocyanate in the present invention may be any distillation residue generated by distillation in any step of the isocyanate production equipment. Usually, it is produced mainly by distilling a reaction solution obtained in an amine production step or a step of reacting an amine with a carbonyl source such as phosgene.

The amount of the by-product of the distillation residue varies depending on the production method, but is generally about 10% by weight based on the isocyanate extracted from the top of the purification distillation column. This distillation residue is usually in a liquid state, and contains several tens%, for example, 50 to 10 wt% of a volatile component.

In the present invention, as a device for recovering the above-mentioned distillation residue to a state substantially free of volatile components, a device used in a normal volatilization recovery step such as a device having a stirring and heating means such as a thin film evaporator, a kneader or the like. Is mentioned. Among them, it is particularly preferable to use a two-phase flow type evaporator having a piston flow property.

The evaporator having the piston flow property is as follows:
It refers to equipment in which the evaporant flows in a certain direction from upstream to downstream of the device. What is a two-phase flow evaporator?
It is an evaporator having at least a gas-liquid or gas-solid two-phase flow, and gas-liquid-solid three phases may coexist.

Representative examples of these are a kneader and a double tube heat exchanger. Among these, wavy flow,
A tubular evaporator that forms at least one of a slag flow, an annular flow, and a spray flow is particularly preferable. A device in which the flow state is formed by a gas generated inside the evaporator is most preferable. For example, a double tube heat exchanger or the like is suitably used.

Referring to FIG. 2, a double-pipe heat exchanger will be described as an example of a piston flow evaporator suitably used in the present invention.

The distillation residue from the distillation column is supplied to a double tube heat exchanger 202 by a pump 201. The distillation residue may be preheated by another heat exchanger (not shown) in advance. A pressure control valve 203 may be provided at the inlet of the double-pipe heat exchanger as needed. The distillation residue supplied to the double tube heat exchanger is heated by steam (STM) or the like. The flow state inside the double-pipe heat exchanger varies depending on the temperature, volatile components, pressure, etc. of the distillation residue supplied to the double-pipe heat exchanger, but passes through the following flow state. 1) When there are many volatile components or the temperature of the distillation residue is low In the vicinity of the inlet of the double-tube heat exchanger, the distillation residue is preheated and the whole is liquid. When this preheating flow is heated by a heating medium such as steam, the volatile components evaporate to form a wavy flow, a slag flow, an annular flow, and a spray flow via a bubble flow or the like. 2) When the volatile component is small or the temperature of the distillation residue is high due to preheating, etc. Usually, a gas phase exists from the supply port of the double-tube heat exchanger, and forms a bubble flow, a wavy flow, and a slag flow. Thereafter, when they are heated by a heat medium such as steam, the volatile components evaporate to form a wavy flow, a slag flow, an annular flow, and a spray flow via a bubble flow or the like. In particular, when preheating is performed, it is preferable to suppress the generation of bubbles in the preheating heat exchanger. Therefore, it is preferable to provide a valve at the entrance of the double-pipe heat exchanger.

These flow states in a two-phase flow type evaporator having a piston flow property are caused by the expansion of the volume due to the evaporation of volatile components, which accelerates the movement of the fluid inside the evaporator. . As a result, even if the volatile components evaporate and the viscosity increases, the volatile components can be separated without closing the heat exchanger due to the kinetic energy of the gas phase. In particular, it is preferable to form a spray flow inside the two-phase flow type evaporator because the obtained solid residue is already fine powder at the outlet of the two-phase flow type evaporator. The obtained solid residue may be further pulverized if necessary.

In the evaporating equipment having the piston flow property, the applied heat is immediately consumed by the latent heat of evaporation.
It is possible to suppress a rise in temperature inside the evaporating equipment and keep the temperature of the heat source necessary for evaporation low. Keeping the temperature of the heat medium low in this manner not only reduced the cost per unit of energy, but also suppressed the loss of raw materials. That is, since the rate of thermal polycondensation of isocyanate and the like depends on its temperature and concentration, the temperature of the heat medium can be kept low, so that the rate of polycondensation can be suppressed and the formation of oligomers and the like can be suppressed. . Further, the volatile components evaporate one after another due to the added heat, so that the concentration of the thermal polycondensable component such as isocyanate can be kept low, and the rate of the thermal polycondensation can be further suppressed.

Further, as the volatile components evaporate one after another, a boiling heat transfer can be achieved, and the state can be maintained for a long time. Further, the linear velocity of the fluid inside the evaporating equipment became extremely high due to the volume expansion described above, and the surface renewal at the heat transfer interface could be promoted. Heat transfer efficiency is further improved by promoting surface renewal and using boiling heat transfer, and by-products of thermal polycondensates, which are difficult to decompose and recover, can be suppressed, and in some cases, can be substantially eliminated. Was. The temperature, pressure, etc., in such an evaporator are not particularly limited, but the temperature is usually 120 to 350 ° C, more preferably 180 to 230 ° C.
It is. The pressure varies depending on the boiling point of the volatile component, but is preferably reduced to 1 to 200 mmHg, more preferably 5 to 15 mmHg in absolute pressure. The gas linear velocity of a two-phase flow type evaporator having a piston flow property is usually 100 to
700 m / s, preferably 200 to 600 m / s. Since the gas linear velocity changes successively in the two-phase flow type evaporator, it is defined using the gas linear velocity at the outlet of the two-phase flow type evaporator.

The heat medium of the two-phase flow type evaporator having the piston flow property may be any of steam, electric heater, hot oil and the like, but steam is preferred.

The distillation residue from which volatiles are separated in the double-tube heat exchanger 202 in this manner is supplied to a hopper 204 and separated into a gas phase and a solid residue.
5, and the solid residue is sent by a solid discharge device 206 to a decomposition step 207 (eg, the slurry preparation drum 102 of FIG. 1), where it is hydrolyzed and converted to an amine as described above. The hopper 204 may be provided with a powder collecting device (not shown) such as a bag filter as needed.
The gas phase extracted from the line 205 is condensed and purified as necessary, and recovered as an isocyanate component or a raw material for producing isocyanate. The solid discharging device is not particularly limited, but usually a screw type powder feeder, an air current type powder transporting device, or the like is used.

[0050]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which do not limit the present invention in any way. Example 1 A distillation residue containing about 50% of tolylene diisocyanate was separated from volatile components using a double-tube evaporator under the conditions of an in-tube evaporation residue temperature of 200 ° C. and an absolute pressure of 10 mmHg. A solid residue containing 0.5% was obtained.
At this time, the gas linear velocity at the outlet of the double tube type evaporator is 400
m / sec. A reactor was charged with 4.0 g of the solid residue, and after degassing under vacuum, 25.4 g of water was injected into the reactor.
And at this temperature the solid residue decomposed. At this time, the pressure showed 27 MPa. Ten minutes later, the contents were quickly cooled to room temperature and the contents were taken out. As a result, 24.6 g of a liquid was recovered. Black viscous pitch-like residue adhered to the inner wall of the reaction tube. Methanol was added to the pitch-like residue, and the pitch-like residue was completely recovered.

As a result, toluene diamine was 16.7% by weight based on the solid residue filled from the recovered liquid and the pitch-like residue to which methanol was added.
And 5.8%, both in a yield of 22.5%, confirming that the solid residue could be converted to the amine corresponding to the component compound therein. Example 2 The weight ratio of water to solids was kept the same as in Example 1,
The mixture was heated at 380 ° C. and a pressure of 19 MPa for 10 minutes, and a decomposition product was recovered in the same manner as in Example 1.

As a result, toluene diamine was 15.6% and 5.7% on a weight basis with respect to the filled solid residue from the recovered liquid and the pitch-like residue to which methanol was added, and both were 21.4%. It was confirmed that the solid residue could be converted to the amine corresponding to the component compound therein. Example 3 The weight ratio of water to solids was kept the same as in Example 1,
The mixture was heated at 300 ° C. and a pressure of 23 MPa for 10 minutes, and a decomposition product was recovered in the same manner as in Example 1.

As a result, toluene diamine was 29.6% and 6.8% by weight based on the solid residue charged from the recovered liquid and the pitch-like residue to which methanol was added, and 36.4% in both cases. It was confirmed that the solid residue could be converted to the corresponding amine. Example 4 The weight ratio of water to the solid was tripled, and the mixture was heated at 300 ° C. and a pressure of 8.8 MPa for 10 minutes.
Collected in the same manner as described above.

As a result, toluene diamine was 39.6% and 5.6% by weight based on the solid residue filled in the recovered liquid and the pitch-like residue to which methanol was added, and 45.2% in both cases. It was confirmed that the solid residue could be converted to the corresponding amine. Example 5 The weight ratio of water to solids was 22 at the same ratio as in Example 4.
The mixture was heated at 0 ° C. and a pressure of 2.4 MPa for 60 minutes, and a decomposition product was recovered in the same manner as in Example 1.

As a result, toluene diamine was 30.3% and 5.2% by weight based on the solid residue from the recovered liquid and the pitch-like residue to which methanol was added, and 35.5% in both cases. It was confirmed that the solid residue could be converted to the corresponding amine. Example 6 A reactor was charged with 4.0 g of a solid residue obtained by further recovering the isocyanate from the residue of tolylene diisocyanate distillation, and after deaeration under vacuum, water and methanol were added such that the weight ratio of water to the solid was tripled. Was injected. At this time, the molar ratio of methanol to water is 1. Thereafter, the reaction tube was heated to 300 ° C. to reach the decomposition temperature. At this time, the pressure showed 15 MPa. Ten minutes later, the mixture was quickly cooled to room temperature and the contents were taken out.
5 g were recovered. Nothing was found in the reaction tube other than the water adhering to the vessel wall.

As a result of analyzing the recovered liquid, it was confirmed that toluenediamine was obtained in a yield of 35.8% on a weight basis with respect to the charged solid residue, and the solid residue could be converted to the corresponding amine. Comparative Example 1 The weight ratio of water to solid was tripled, and 90 ° C., 0.2 M
The treatment was carried out in the same manner as in Example 1 except that heating was performed at Pa for 60 minutes. As a result, the solid remained in the form at the time of filling, and there was no pitch-like residue. No toluenediamine was detected from the liquid after the solid-liquid separation.

[0057]

According to the method of the present invention, the solid residue of isocyanate, which has been conventionally disposed of as industrial waste, can be efficiently converted into an amine corresponding to the solid residue without using an additive such as an alkali. Became possible. By using a two-phase flow evaporator with piston flow properties, it is possible to suppress the thermal polycondensation of components that are easily thermally polycondensed, such as isocyanate, and to efficiently recover the isocyanate. A suitable solid residue could be prepared.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of a process of removing volatile components from a distillation residue by a double tube heat exchanger.

FIG. 2 is a conceptual diagram of a solid residue hydrolysis step.

[Explanation of symbols]

 101 line 102 slurry adjusting drum 103 line 104 preheat exchanger 105 reactor 106 decomposition product 201 pump 202 double tube heat exchanger 203 pressure control valve 204 hopper 205 line 206 solid discharge device 267 decomposition process

Claims (12)

[Claims] 1. The method according to claim 1, wherein the solid residue produced as a by-product during the production of the isocyanate is in the presence of gas, liquid or supercritical water, or a mixture of alcohol and water, at a temperature of 100 ° C. or higher, and at a pressure of 0.
A method for decomposing a solid residue, comprising heating at 1 MPa or more to convert the solid residue into an amine corresponding to the component compound. 2. The solid residue is removed at 20 torr and 180 ° C.
The solid residue decomposition method according to claim 1, wherein the weight loss of the solid residue when kept for 1 hour is 3% or less. 3. The weight ratio of water to the solid residue is 0.3.
The solid residue decomposition method according to claim 1, wherein the number is one or more. 4. The method according to claim 1, wherein the molar ratio of alcohol to water is 5
The solid residue decomposition method according to claim 1 or 3, wherein 5. The method according to claim 1, wherein the pressure is 0.5 to 40 MPa and the temperature is 150 to 450 ° C. 6. A volatile component is separated from a distillation residue containing a volatile component by-produced during the production of isocyanate, and the obtained solid residue is converted into gas, liquid or supercritical water or a mixture of alcohol and water. A method for decomposing a solid residue, comprising heating at a temperature of 100 ° C. or more and a pressure of 0.1 MPa or more in the presence to convert the solid residue into an amine compound corresponding to the component compound. 7. The method for decomposing a solid residue according to claim 6, wherein the separation of the volatile components is performed in a two-phase flow type evaporator having a piston flow property. 8. The method according to claim 7, wherein the two-phase flow type evaporator is a double tube type evaporator. 9. The method according to claim 1, wherein said volatile component is separated at a temperature of 120 to 35.
The solid residue decomposition method according to claim 7, wherein the method is performed at 0 ° C., a pressure of 1 to 200 mmHg, and a gas flow rate at an outlet of the two-phase flow type evaporator of 100 to 700 m / sec. 10. The solid residue decomposition method according to claim 6, wherein the weight ratio of water to the solid residue is 0.1 or more. 11. The method for decomposing a solid residue according to claim 6, wherein the molar ratio of the alcohol to water is 5 or less. 12. The isocyanate-containing distillation residue produced as a by-product during isocyanate production is heated in a two-phase flow type evaporator having a piston flow property to separate the isocyanate from the distillation residue. Gas,
A distillation residue, which is brought into contact with liquid or a mixture of water or alcohol and water in a supercritical state at a temperature of 100 ° C. or more and a pressure of 0.1 MPa or more to convert the solid residue into an amine corresponding to the component compound. Processing method.