KR20000017605A - Solid residue decomposing method - Google Patents

Abstract

PURPOSE: Recycling of solid waste in the process of isocyanate preparation is in need to cut down the cost of disposal of waste. CONSTITUTION: The invention is disclosed a decomposition method of solid waste produced during the preparation of isocyanate performed by addition of gas, liquid, or super critical state of water or mixture of alcohol and water at 160°C and 20 torr for 1 hour. The method decomposes solid waste into corresponding amine and decrease the weight of waste under 3 % of total weight. Recycling of decomposition product cuts down the cost of process and enables to skip the process of waste disposal.

Description

Solid residue decomposing method

The present invention relates to a method for decomposing a solid residue, which is a by-product of isocyanate production in the presence of gas, liquid or supercritical water, or a mixture of alcohol and water, and converts it into an amine corresponding to a component compound of the solid residue. It is about.

The present invention also relates to a method of recovering isocyanate from distillation residues, which are by-products during the production of isocyanate, to solid residues, and hydrolyzing the solid residues as described above.

Isocyanate generally reacts an amine corresponding to isocyanate with phosgene, distills the reaction product, removes by-products and tar components, respectively, to form crude isocyanate, and attach the crude isocyanate to rectification. It is prepared by the method of obtaining purified isocyanate. This tar component obtained as distillation residue is produced by side reactions in the phosgenation step and thermal polycondensation in the distillation step, and complex polycondensation such as urea, biuret, carbodiimide and isocyanurate It is thought to be a mixture of water. The distillation waste is usually recovered with the isocyanate contained therein, and the remainder is disposed of as industrial waste, or the distillation residue as industrial waste as it is.

As mentioned above, the isocyanate residue which is a byproduct at the time of isocyanate manufacture has been disposed of as industrial waste conventionally, At the same time, the study regarding effective utilization has also been carried out. In recent years, however, the effective use of industrial wastes has been actively reviewed from the viewpoint of reducing the load on the environment and recycling of resources.

As an example of the conventional isocyanate distillation residue review, Japanese Patent Application Laid-Open No. 5-79690 discloses a mixture in which a monohydric alcohol is added to tolylene diisocyanate residue, which is converted into a carbamate, followed by a polyol. The technique which makes urethane foam which added foaming agent etc. to this is disclosed. This method should be evaluated in that the distillation residues are changed into more effective oil value.

On the other hand, as an approach to the isocyanate manufacturing process, attempts have been made to reduce the production cost by recovering isocyanate from distillation residues again or decomposing distillation residues and recovering them as corresponding amines.

For example, Japanese Patent Application Laid-Open No. 50-142501, Japanese Patent Application Laid-Open No. 54-130525, Japanese Patent Application Laid-Open No. 58-201751, etc., hydrolyze isocyanate distillate in the presence of an alkaline aqueous solution to separate solids in the decomposition liquid. Obtaining the corresponding amine is disclosed by doing so. More specifically, Japanese Patent Application Laid-Open No. 50-142501 discloses isocyanate distillation residues at 100 to 200 ° C in 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. It is disclosed that heating for 30 minutes to 5 hours with a saturated solution of to separate the precipitated solid to obtain a corresponding amine. However, all of them promote the hydrolysis using an alkali, and the process such as separation of the precipitated solid becomes complicated, so the cost up is inevitable and cannot be said to be an economical method.

In recent years, Japanese Patent Application Laid-Open No. 9-151270 discloses a method of decomposing a target compound in a short time which was not expected in the prior art, in which molten or liquid waste is 10 minutes into water near a critical point. Recovery as a corresponding raw material compound or derivative thereof is disclosed. The characteristics of this technology are that the wastes in molten or liquid state are decomposed by using water alone without using a hydrolysis accelerator as in the prior art, or under the conditions near the critical point of water, but the construction cost is very high. It is not big.

However, in this method, since the waste in the molten or liquid state contains useful substances such as isocyanate which can be readily recycled to the manufacturing process as it is, it is hydrolyzed and converted into an amine corresponding to the isocyanate. And reuse in the isocyanate production step is not economical in that it must be reacted with phosgene again.

As described above, these conventional methods do not target solid wastes, that is, solid wastes, but in the end, solid wastes remain, and finally, they have to be disposed of as industrial wastes.

It is therefore an object of the present invention to provide a method for converting a reusable amine into a reusable solid without adding a hydrolysis accelerator such as an alkali to a by-product solid residue during isocyanate production. .

It is another object of the present invention to efficiently separate isocyanates from distillation residues produced by-products during isocyanate production, and to convert the obtained solid residues efficiently into hydrolyzable and corresponding amines without adding alkali. To provide a way.

1 is a conceptual diagram of a process for removing volatiles from distillation residues by a double tube heat exchanger.

2 is a conceptual diagram of a hydrolysis process of solid waste

<Explanation of symbols for main parts of drawing>

101: line 102: slurry preparation drum

103: line 104: preheat exchanger

105: reactor 106: line

107: line 201: pump

202: double tube heat exchanger 203: pressure control valve

204: hopper 205: line

206: solid discharge device 207: decomposition process

Therefore, the present inventors earnestly examined to solve the above problems, and as a result, by heating the solid residue produced by the isocyanate production in the presence of gas, liquid or supercritical water or a mixture of alcohol and water, What has been found to be convertible to the corresponding amines, and the necessary and decent conditions for them, have been reached to complete the present invention.

That is, this invention relates to the solid waste decomposition method as described in (1)-(12) below.

(1) The solid residue produced by-product in the production of isocyanate is heated at a temperature of 100 ° C. or higher and a pressure of 0.1 MPa or higher in the presence of a gas, a liquid or supercritical water, or a mixture of alcohol and water. Solid residue decomposition method characterized by converting into amine corresponding to the component compound of solid residue.

(2) The solid waste decomposition method according to the above (1), wherein the weight loss of the solid residue when the solid residue is kept at 20 tor and 180 ° C for 1 hour is 3% or less.

(3) The solid waste decomposition method according to the above (1), wherein the weight ratio of water to the solid residue is 0.1 or more.

(4) The solid waste decomposition method according to the above (1) or (3), wherein the molar ratio of alcohol to water is 5% or less.

(5) The solid waste decomposition method according to the above (1), wherein the pressure is 0.5 to 40 MPa and the temperature is 150 to 450 ° C.

(6) The volatile components are separated from the distillation residues containing volatile components by-products during the production of isocyanate, and the obtained solid residues are subjected to a temperature of 100 in the presence of gas, liquid or supercritical water or a mixture of alcohol and water. A method for decomposing a solid residue, wherein the residue is heated at a pressure of 0.1 MPa or higher and converted to an amine compound corresponding to the component compound of the solid residue.

(7) The solid waste decomposition method according to the above (6), wherein the volatile component is separated in a two-phase evaporation apparatus having a piston flow property.

(8) The solid waste decomposition method according to the above (7), wherein the two-phase evaporation apparatus is a double tube evaporation apparatus.

(9) In the above (7) or (8), the separation of the volatile components is carried out at a temperature of 120 to 350 DEG C, a pressure of 1 to 200 mmHg, and a gas flow rate of 100 to 700 m / sec at the outlet of the two-phase evaporator. Solid waste decomposition method described.

(10) The solid waste decomposition method according to the above (6), wherein a weight ratio of water to the solid residue is 0.1 or more.

(11) The solid waste decomposition method according to (6) or (10), wherein the molar ratio of alcohol to water is 5 or less.

(12) The isocyanate-containing distillate residue produced during isocyanate production is heated in a two-phase type evaporator having a piston flow property to separate the isocyanate from the distillation residue, and the obtained solid residue is obtained by gas, liquid. Or a supercritical water or a mixture of alcohol and water and contacting at a temperature of 100 ° C. or higher and a pressure of 0.1 MPa or higher to convert to an amine corresponding to the component compound of the solid residue. .

In the present invention, the solid residue produced by-product at the time of isocyanate production means the residue which arises at the time of manufacturing a compound which has at least 1 -NCO group, such as the following monoisocyanate and diisocyanate.

As monoisocyanate, aliphatic monoisocyanate, aromatic monoisocyanate, etc. which are represented by general formula R-NCO (R is an aliphatic group or an aromatic group) are mentioned, for example.

As an example of aliphatic monoisocyanate, methyl isocyanate, n-butyl isocyanate, etc. are mentioned. Moreover, phenyl isocyanate etc. are mentioned as a specific example of aromatic monoisocyanate.

As diisocyanate, aliphatic diisocyanate, aromatic diisocyanate, alicyclic diisocyanate, etc. which are represented by general formula OCN-R-NCO (R is said group or alicyclic group) are mentioned.

Hexamethylene diisocyanate etc. are mentioned as a specific example of aliphatic diisocyanate. As aromatic diisocyanate, xylene diisocyanate, tolylene diisocyanate, naphthylene diisocyanate, diphenylmethane diisocyanate, etc. are mentioned. Examples of the alicyclic diisocyanate include isophorone diisocyanate and norbornane diisocyanate. In addition to the above isocyanate, for example, by-product solid residues produced in the production of an isocyanate compound having three or more -NCO groups such as triisocyanate can also be used. The solid dregs used in the decomposition of the present invention may be generated in any step as long as the solid dregs produced by-products during isocyanate production. Specifically, it is a solid waste produced by any of an amine manufacturing process, the reaction process of an amine and a phosgene, the isocyanate purification process, or the process of recovering an isocyanate. These solid wastes may melt and melt | dissolve in each process. In addition, the solid residue which can be applied to the present invention is not limited to an isocyanate produced using phosgene, and when produced by the non-phosgene method, it is also possible to decompose the solid residue produced by any one of these processes. Not to mention.

Any solid residue may be used, but is usually used after separating the solid residue generated in each step from the liquid component by a solid / liquid separation step, a distillation step, or the like. It is preferable to go through the purification process of isocyanate. In particular, when the isocyanate is purified by distillation, the distillation residue (that is, the purification distillation step of the isocyanate) is preferable, and it is particularly preferable that the distillation residue is recovered until it is substantially free of volatile components.

The solid which does not contain a volatile content here means that the weight loss after hold | maintaining at 20 tor and 180 degreeC for 1 hour is less than 3 wt%.

Solid residues produced by the production of these isocyanates are mainly mixtures composed of thermal polycondensates such as imines and isocyanates. The thermal polycondensate has, for example, groups or rings such as urea (urethane), biuret, carbodiimide, isocyanate and the like. In particular, many compounds having a complex structure having a plurality of these groups or rings are contained. The solid residue is hydrolyzed to an amine corresponding to the component compound of the solid residue by contacting gas, liquid or supercritical water, or a mixture of alcohol and water under high temperature and high pressure.

The decomposition process of this solid waste is demonstrated with reference to FIG. Solid residue is fed from the line 101 to the slurry preparation drum 102. Water is supplied from line 103. Water may carry predetermined amount of alcohol as needed. The slurry prepared in (102) is heated up by the preheat exchanger (104), is supplied to the reactor (105), and the decomposition products are refined as needed to extract from the (106) and recycled to an isocyanate raw material or the like.

From line 107, a by-product gas, mainly carbon dioxide, is discharged by solid residue decomposition.

The solid waste to be used may be any solid waste generated at the time of isocyanate production as long as it is a term. Especially, it is especially preferable to use what isolate | separated volatile matter by the two-phase type evaporation apparatus which has a piston flow property. From solid residues that are substantially free of volatiles (i.e., mixtures of thermal polycondensates composed of the above by-products after recovery of isocyanate monomers to the limit from residual distillation residues of several 10% tars). Consisting of) is particularly preferred.

These solid wastes decompose upon contact with water at high temperature and high pressure. High temperature and high pressure mean a temperature of 100 degreeC or more and a pressure of 0.1 Mpa or more specifically. At this time, water takes one of gas, liquid, and supercritical forms depending on the temperature and pressure. In addition, water may contain alcohol or the like alone.

In order to increase the contact interface when the solid residue is brought into contact with water at high temperature and high pressure, the solid residue is preferably a fine powder, and in the case of a lump form, it is preferable to grind it to an appropriate size in advance.

Preferable temperature and pressure conditions for decomposing solid residues are at least 150 ° C and at least 0.5 MPa. In particular, there is no upper limit of temperature and pressure, but is preferably at most 450 캜 and at most 40 MPa.

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

The mixed heating of water and solid residues may be performed by any of the following methods, but 3) is preferable.

1) Mix water and solid residues to a predetermined temperature beforehand.

2) When water is mixed with solid residue, it is heated to a predetermined temperature, and the heated water and solid residue are mixed to obtain a decomposition temperature.

3) Prepare the slurry by mixing water and solid residue to a predetermined concentration in the slurry preparation drum, etc., and then heating to the decomposition temperature.

1/10 or more are preferable and, as for the weight ratio (water / solid waste) of water with respect to solid waste, More preferably, it is 1/2 or more. If the weight ratio of water to solid residue is less than 1/10 times, the decomposition products are not preferred because most of them are not only pitch residues but also tend to lower corresponding amine yields.

In the present invention, the molar ratio of alcohol to water (alcohol / mole) is preferably 5 or less, and more preferably 3 or less. When the molar ratio of alcohol to water exceeds 5, the yield of amine tends to be low, and since carbamate bodies and other alcohol-derived by-products tend to be produced, it is not preferable. In the present invention, the alcohol after coexistence in the reaction system can be recovered as a uniform aqueous solution. By making the product after decomposition into a uniform aqueous solution, the recovery of the amine from the decomposition product is simplified.

The alcohol used in the present invention is not particularly limited, but specific examples thereof include monohydric alcohols such as methanol, ethanol, isopropanol, n-butanol, tert-butanol and 1-octanol; Dihydric alcohols such as ethylene glycol, propylene glycol, diethylene glycol, trihydric alcohols such as trimethylolpropane, 1,2,6-hexatriol, and tetrahydric alcohols such as pentaerythritol. These alcohols may be used alone or in combination of two or more thereof and mixed with water.

It is more preferable that they are represented by methanol, ethanol, isopropanol, ethylene glycol, and propylene glycol which have high solubility with water in these alcohols. In the present invention, by using these alcohols in combination with water, it is possible to solubilize the pitch-like residue in the recovered matter after the solid residue decomposition.

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

It goes without saying that the amine corresponding to the isocyanate other than water or alcohol and water is contained as the main component in the aqueous solution obtained by dividing the solid residue in this way. Corresponding imine can be easily recovered by a normal distillation or extraction method. The recovered amine is further purified as necessary and then circulated as a raw material in the isocyanate production step to react with phosgene.

In the aqueous solution in which the amine is separated, a nasolabial component composed mainly of carbon dioxide is dissolved, but hydrolysis is performed after the alcohol is added as desired without removing or removing it by steam stripping or the like. It can also be recycled as water for dragons. Alternatively, the wastewater may be drained after the usual wastewater treatment.

The distillation residue at the time of manufacturing isocyanate in this invention may be any distillation residue which generate | occur | produced by distillation in any one process of the manufacturing equipment of an isocyanate. Usually, it arises by distilling the reaction liquid obtained mainly in the amine manufacturing process or the process of reacting an amine and a carbonyl source, for example, phosgene.

The by-product amount of this distillation dreg varies depending on the production method thereof, but is generally about 10 wt% based on the isocyanate that is released from the top of the column of the refinery distillation column. This distillation residue is normally liquid and contains 10%, for example, 50 to 10% by weight of volatile components.

In the present invention, as the apparatus for recovering from the distillation residue to a state that does not substantially contain volatile components, those used in a normal volatilization recovery process such as a device having a stirring and heating means such as a thin film evaporator and a kneader may be mentioned. Among them, it is particularly preferable to use a two-phase type evaporator having a piston flow property.

An evaporation device having a piston flow property means an installation in which an evaporation body flows in a constant direction from the upstream to the downstream of the device. The two-phase type evaporation apparatus is an evaporation apparatus having at least one of two-phase flows of a gas liquid and a condensation, and three phases of the gas liquid chamber may coexist.

As these representative examples, a kneading machine, a double tube type heat exchanger, etc. are mentioned. Among these, the tubular evaporation apparatus which forms at least any one of a wave flow, a slack flow, a cyclic flow, and a spray flow form is especially preferable. The device in which the flow state is formed by the gas generated inside the evaporator is most preferred, and a double tube heat exchanger or the like is suitably used, for example.

With reference to FIG. 2, it demonstrates taking a double tube type heat exchanger as an example as an evaporation apparatus with a piston flow property suitably used for this invention.

The distillation residue from the distillation column is supplied to the double tube heat exchanger 202 by the pump 201. The distillation residue may be preheated by another heat exchanger (not shown) in advance. The pressure control valve 203 may be provided at the inlet of the double tube type heat exchanger. The distillation residue supplied to the double tube heat exchanger is heated by steam (STM) or the like. The flow state inside the double tube type heat exchanger varies depending on the temperature, volatile components, and pressure of the distillate residues supplied to the double tube type heat exchanger.

1) When there are many volatile components but the temperature of distillation residue is low

Near the inlet of the double-tube heat exchanger, the distillation residues are preheated and the whole is liquid. The preheating flow is heated by the fruit such as steam, so that the volatile component evaporates and forms a wave, slack, cyclic flow, and spray flow through the bubble flow and the like.

2) Low volatile content or high temperature of distillation residues due to preheating

Usually, a gaseous phase exists from a pore hole of a double-tube heat exchanger, and bubbles, shells, and slags are formed. After that, they are heated by fruit such as steam, whereby volatiles evaporate and bubbles. Through the formation of the wave, slack, cyclic flow, spraying. In particular, in the case of preheating, it is preferable to suppress the generation of bubbles in the preheating heat exchanger. Therefore, a valve is preferably provided at the inlet of the double tube type heat exchanger.

In the two-phase type evaporator having a piston flow property, their flow state is caused to increase in volume due to evaporation of volatile components, and this occurs as it accelerates the movement of the fluid inside the evaporator. Thereby, even if volatile matter evaporates and a viscosity rises, separation of volatile matter can be achieved without closing a heat exchanger by the kinetic energy which the gaseous phase has. In particular, when the spray flow is formed inside the two-phase evaporator, the obtained solid residue is preferably fine powder at the outlet of the two-phase evaporator. The solid waste obtained may be further pulverized if necessary.

In the evaporation ratio having a piston flow property, the heat applied is immediately consumed as the latent heat of evaporation, the temperature rise in the evaporation chamber ratio can be suppressed, and the temperature of the heat source necessary for evaporation can be kept low. Maintaining such a low temperature of the fruit not only lowered the cost per unit of energy, but also suppressed the loss of raw materials. That is, since the thermal polycondensation rate of isocyanate or the like depends on the temperature and concentration, the temperature of the fruit can be kept low, thereby suppressing the polycondensation rate and suppressing the production of oligomers and the like. By further evaporating the volatile component by the amount of heat applied, the concentration of thermal polycondensable components such as isocyanate can be kept low, and the rate of thermal polycondensation can be further suppressed.

Moreover, as volatile matter continued to evaporate, it could become boiling heat transfer, and the state was able to be maintained for a long time. In addition, the linear velocity of the fluid in the evaporative ratio was very large due to the above-mentioned volume expansion, which facilitated surface renewal in the heat transfer interface. By promoting surface renewal and using boiling heat transfer, the heat transfer efficiency is further improved, and by-products of the thermal polycondensate, which are difficult to decompose, can be suppressed, and in some cases, it is substantially prevented from developing. Although it does not specifically limit to the temperature, pressure, etc. in such an evaporation apparatus, Temperature is 120-350 degreeC normally, More preferably, it is 180-230 degreeC. The pressure varies depending on the boiling point of the volatile component, but is preferably reduced pressure, preferably 1 to 200 mmHg, more preferably 5 to 15 mmHg absolute. The gas line velocity of the two-phase evaporator having a piston flow property is usually 100 to 700 m / s, preferably 200 to 600 m / s. In addition, since the gas linear velocity changes gradually inside the two-phase evaporator, the gas linear velocity is defined using the gas linear velocity at the outlet of the two-phase evaporator.

As the fruit of the two-phase type evaporator having a piston flow property, any of steam, heat transfer device, hot oil and the like may be used, but steam is preferable.

In this way, in the double tube heat exchanger 202, the distillation residue from which the volatile components are separated is supplied to the hopper 204, separated into the gas phase and the solid residue, and the gas phase is discharged from the line 205, and the solid residue is the solid. It is sent to the decomposition process 207 (for example, the slurry preparation drum 102 of FIG. 1) by the discharge device 206, and is hydrolyzed as mentioned above and converted into amine. The hopper 204 may be provided with a powder collecting facility (not shown) such as a bug filter if necessary. The gaseous phase which exited the line 205 is condensed and refine | purified as needed, and is recovered as an isocyanate component or the raw material for isocyanate manufacture. The solid discharge device is not particularly limited, but a screw powder feeder, an air flow powder transport device, and the like are usually used.

Hereinafter, the present invention will be described in more detail with reference to the following Examples, which are not intended to limit the present invention.

(Example 1)

After distillation residue containing about 50% of tolylene diisocyanate was separated from the volatiles under the condition of an evaporation residue temperature of 200 DEG C and an absolute pressure of 10 mmHg using a double tube evaporator, a solid residue containing 0.5% of tolylene diisocyanate was obtained. . At this time, the gas flux at the outlet of the double tube evaporator was 400 m / sec. 4.0 g of this solid waste was charged to a reactor, 25.4 g of water was injected after vacuum degassing, it heated at 380 degreeC, and the solid waste was decomposed | disassembled at this temperature. At this time, the pressure displayed 27 MPa. After 10 minutes, the mixture was cooled to room temperature quickly and the contents were taken out. As a result, 24.6 g was recovered. A black sticky pitch residue remained on the inner wall of the reaction tube. Methanol was added to this pitch residue to completely recover the pitch residue.

As a result, toluenediamine was obtained in a yield of 16.7% and 5.8% by weight and 22.5%, respectively, with respect to the solid residues charged from the recovered solution and the pitch residue added with methanol, respectively. It was confirmed that it could be converted into the amine corresponding to.

(Example 2)

The weight ratio of water to solid was maintained at the same ratio as in Example 1, heated at 380 ° C. and 19 MPa for 10 minutes, and the decomposition product was recovered in the same manner as in Example 1.

As a result, toluenediamine was obtained in a yield of 15.6% and 5.7% by weight and 21.4%, respectively, based on the weight of solid residue from the recovered liquid and the methanol-added pitch residue. It was confirmed that it could be converted into the amine corresponding to.

(Example 3)

The weight ratio of water to solid was maintained at the same ratio as in Example 1, heated at 300 ° C. at 23 MPa for 10 minutes, and the decomposition product was recovered in the same manner as in Example 1.

As a result, toluene diamine was obtained in the yield of 29.6% and 6.8% by weight basis, and 36.4% by weight, respectively. It was confirmed that conversion was possible.

(Example 4)

The weight ratio of water to solid was tripled, the mixture was heated at 300 DEG C and a pressure of 8.8 MPa for 10 minutes, and the decomposition product was recovered in the same manner as in Example 1.

As a result, tolueneamine was obtained in a yield of 39.6% and 5.6% by weight, and 45.2% by weight, respectively, from the recovered solids and the pitch residue with methanol added to the solid residue. It was confirmed that it could be converted.

(Example 5)

The weight ratio of water to solid was heated for 60 minutes at 220 캜 and a pressure of 2.4 MPa at the same ratio as in Example 4, and the decomposition product was recovered in the same manner as in Example 1.

As a result, toluene diamine was obtained in the yield of 30.3% and 5.2% by weight, respectively, and 35.5% by weight, based on the recovered solids and the pitch residue added with methanol, respectively. It was confirmed that we could convert.

(Example 6)

4.0 g of the solid residue after the isocyanate recovery from the tolylene diisocyanate distillation residue was charged into the reactor, and 33.0 g of a mixture of water and methanol was injected so as to triple the weight ratio of water to solid after vacuum degassing. The molar ratio of methanol to water at this time is 1 times. Thereafter, the reaction tube was heated at 300 ° C. to a decomposition temperature. At this time, the pressure displayed 15 MPa. After 10 minutes, the mixture was cooled to room temperature quickly and the contents were withdrawn. As a result, 36.5 g was recovered. Nothing other than water attached to the wall of the device was found in the reaction tube.

As a result of analysis of the recovered liquid, it was confirmed that toluenediamine was obtained in a weight-based yield of 35.8% with respect to the solid residue charged, and the solid residue could be converted into the corresponding amine.

(Comparative Example 1)

The weight ratio of water to solid was tripled and treated in the same manner as in Example 1 except that the mixture was heated at 90 ° C and 0.2 MPa for 60 minutes. As a result, the solid remained in the form at the time of filling, and there was no pitch-like residue. Toluenediamine was not detected from the liquid after solid-liquid separation.

According to the method of the present invention, it is possible to efficiently convert solid residues of isocyanates that have been disposed of as industrial wastes to amines corresponding to solid residues without using additives such as alkalis. By using a two-phase type evaporator having a piston flow property, thermal polycondensation of components that are easily thermally condensed such as isocyanate can be suppressed, and isocyanate can be efficiently recovered, and further, solid wastes suitable for hydrolysis can be prepared. there was.

Claims (12)

The solid residue produced by the isocyanate production in the presence of gas, liquid or supercritical water, or a mixture of alkal and water is heated at a temperature of 100 ° C. or higher and a pressure of 0.1 MPa or higher to obtain the solid residue. Solid residue decomposition method characterized by converting into an amine corresponding to a component compound. The solid waste decomposition method according to claim 1, wherein the weight loss of the solid residues when the solid residues are kept at 20 torr and 180 ° C. for 1 hour is 3% or less. The method of claim 1, wherein the weight ratio of water to the solid residue is 0.1 or more. 4. The method of claim 1 or 3, wherein the molar ratio of alcohol to water is 5% or less. The solid waste decomposition method according to claim 1, wherein the pressure is 0.5 to 40 MPa and the temperature is 150 to 450 ° C. The volatile components are separated from the distillation residues containing volatile components, which are byproducts in the production of isocyanate, and the obtained solid residues are subjected to a temperature of 100 DEG C or higher in the presence of gas, liquid or supercritical water or a mixture of alcohol and water, A method for decomposing a solid residue, which is heated at a pressure of 0.1 MPa or more and converted into an amine compound corresponding to the component compound of the solid residue. The solid waste decomposition method according to claim 6, wherein the volatile component is separated in a two-phase evaporation apparatus having a piston flow property. 8. The method of claim 7, wherein the two-phase evaporator is a double tube evaporator. 9. The solid residue according to claim 7 or 8, wherein the volatile component is separated by a temperature of 120 to 350 DEG C, a pressure of 1 to 200 mmHg, and a gas flow rate of 100 to 700 m / sec at the outlet of the two-phase type evaporator. Decomposition method. 7. The method of claim 6, wherein the weight ratio of water to solid residue is 0.1 or more. The solid residue decomposition method according to claim 6 or 10, wherein the molar ratio of alcohol to water is 5 or less. Distillation residue containing isocyanate, which is a by-product of isocyanate production, is heated in a two-phase evaporator having a piston flow property to separate the isocyanate from the distillation residue, and the obtained solid residue is gas, liquid or supercritical. A process for treating distillation residues, comprising contacting the mixture of water or alcohol in water with water at a temperature of 100 ° C. or higher and a pressure of 0.1 MPa or higher to convert to an amine corresponding to the component compound of the solid residue.