JP2018154588A - Manufacturing method and manufacturing device of n-(cyclohexylthio)phthalimide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and a device for manufacturing N-(cyclohexylthio)phthalimide industrially advantageously even when a reaction mixture is high concentration and contact between raw materials is insufficient in a solid liquid non-homogeneous state.SOLUTION: There is provided a manufacturing method of N-(cyclohexylthio)phthalimide by mixing cyclohexylsulfenyl chloride and phthalimide in a solvent containing saturated hydrocarbon in a reactor, extracting a part of the mixture to the reactor, further externally circulating the mixture by discharging the extracted mixture to the reactor to react the cyclohexylsulfenyl chloride and the phthalimide.SELECTED DRAWING: None

Description

  The present invention relates to a method for producing N- (cyclohexylthio) phthalimide, which is a compound useful as a vulcanization retarder in a rubber vulcanization step. More specifically, a method and an apparatus for producing N- (cyclohexylthio) phthalimide are advantageously provided industrially.

  In general, N- (cyclohexylthio) phthalimide is produced by reacting cyclohexylsulfenyl chloride and phthalimide in the presence of a base. Usually, in this production method, raw material cyclohexylsulfenyl chloride is synthesized under strong acidic conditions using chlorine, and then cyclohexylsulfenyl chloride and phthalimide are condensed under strong basic conditions. Therefore, saturated hydrocarbons are used as solvents that are stable to strong acids and bases and have a low environmental impact, and the reaction is carried out at a high concentration in order to increase productivity industrially.

  These methods can be carried out industrially without problems with the handling of raw materials and target products, reaction operations, environmental burdens, etc., but use of solvents containing saturated hydrocarbons with high concentrations and low solubility makes the reaction mixture solid. The liquid became inhomogeneous, the contact between the raw materials became insufficient, and the reaction yield was not always satisfactory.

JP 2007-186438 A Japanese Examined Patent Publication No. 1-37444

  An object of the present invention is to provide a method and an apparatus for producing N- (cyclohexylthio) phthalimide in an industrially advantageous manner.

  As a result of intensive studies on a method for solving the above problems, the present inventors have improved contact between raw materials by a simple method even when the mixture is in a solid-liquid heterogeneous state, and N- (cyclohexylthio) phthalimide Has been found to be able to be synthesized efficiently, and the present invention has been achieved.

  That is, in the present invention, cyclohexylsulfenyl chloride and phthalimide are mixed in a reactor in a solvent containing a saturated hydrocarbon, a part of the mixture is extracted out of the reactor, and the extracted mixture is further introduced into the reactor. This is a method for producing N- (cyclohexylthio) phthalimide in which N- (cyclohexylthio) phthalimide is synthesized by externally circulating the mixture and allowing cyclohexylsulfenyl chloride to react with phthalimide by discharging.

  Furthermore, the present invention comprises a rotary stirrer, has a charging port at the top of the reactor, further has a discharge port at the bottom of the reactor, a discharge port at the top of the reactor, and the discharge port and discharge port are: Connected by piping, equipped with a liquid feed pump in the middle of the piping, cyclohexylsulfenyl chloride and phthalimide are mixed in the reactor, a part of the mixture is extracted out of the reactor, and the extracted mixture is further discharged into the reactor. Is a device for producing N- (cyclohexylthio) phthalimide in which the mixture is externally circulated to react cyclohexylsulfenyl chloride with phthalimide.

  According to the present invention, it is possible to produce N- (cyclohexylthio) phthalimide in an industrially advantageous manner by simply providing a simple external circulation function to a conventionally used stirred tank reactor. it can.

  The present invention improves the reaction yield of N- (cyclohexylthio) phthalimide. Furthermore, reaction by-products are reduced and the purity of the product is improved.

  When N- (cyclohexylthio) phthalimide is produced by the method for producing N- (cyclohexylthio) phthalimide of the present invention, high-quality N- (cyclohexylthio) phthalimide can be produced at a low production cost.

  Further, when N- (cyclohexylthio) phthalimide is produced with the N- (cyclohexylthio) phthalimide production apparatus of the present invention, high-quality N- (cyclohexylthio) phthalimide can be produced at a low production cost.

It is an example of the reaction apparatus of this invention.

  The present invention is described in detail below.

  In the method for producing N- (cyclohexylthio) phthalimide of the present invention, cyclohexylsulfenyl chloride and phthalimide are mixed in a reactor in a solvent containing a saturated hydrocarbon. The saturated hydrocarbon solvent used in the present invention is preferably a saturated hydrocarbon having 5 to 10 carbon atoms. More preferable examples include n-pentane, cyclopentane, n-hexane, cyclohexane, n-heptane, methylcyclohexane, n-octane, and cyclooctane.

  In the method for producing N- (cyclohexylthio) phthalimide of the present invention, examples of the solvent used by mixing with saturated hydrocarbon include aromatic hydrocarbons and chlorinated hydrocarbons. The aromatic hydrocarbon is preferably an aromatic hydrocarbon having 6 to 8 carbon atoms, more preferably toluene, xylene, ethylbenzene and the like. The chlorinated hydrocarbon is preferably a chlorinated hydrocarbon having 1 to 6 carbon atoms, and more preferable examples include ethylene dichloride and chlorobenzene.

  The cyclohexylsulfenyl chloride used in the method for producing N- (cyclohexylthio) phthalimide of the present invention is generally synthesized by a reaction of dicyclohexyl disulfide or cyclohexyl mercaptan with chlorine. When cyclohexylsulfenyl chloride is synthesized by reaction of dicyclohexyl disulfide or cyclohexyl mercaptan with chlorine, a solvent containing a saturated hydrocarbon is preferably used. More preferably, the same solvent as that used in the reaction of cyclohexylsulfenyl chloride and phthalimide is used.

  The amount of chlorine used when synthesizing cyclohexylsulfenyl chloride by reacting dicyclohexyl disulfide or cyclohexyl mercaptan with chlorine is usually 0.5 to 2 times mol, preferably 1 mol, relative to the raw material sulfide or mercaptan. To 1.5 times mole. The amount of the solvent used is usually 0.5 to 10 times by weight, preferably 1 to 5 times by weight with respect to dicyclohexyl disulfide or cyclohexyl mercaptan. The reaction temperature is generally −30 ° C. to 20 ° C., preferably −20 ° C. to 5 ° C. The reaction time with chlorine gas is usually 0.1 to 10 hours. The reaction time with chlorine gas is preferably 1 to 5 hours. The reaction pressure is usually carried out at normal pressure, but it may be under reduced pressure or under pressure. The reaction is usually carried out by dissolving dicyclohexyl disulfide or cyclohexyl mercaptan in a solvent containing saturated hydrocarbon and blowing chlorine gas.

  In the method for producing N- (cyclohexylthio) phthalimide of the present invention, for example, cyclohexylsulfenyl chloride is synthesized and used at a low temperature. The storage temperature of cyclohexylsulfenyl chloride is usually −30 ° C. to 20 ° C., preferably −20 ° C. to 5 ° C.

  The phthalimide used in the method for producing N- (cyclohexylthio) phthalimide of the present invention may be produced by any synthetic method. For example, a production method by reaction of ammonia or urea with phthalic anhydride can be mentioned.

  In the method for producing N- (cyclohexylthio) phthalimide of the present invention, the reaction condition between cyclohexylsulfenyl chloride and phthalimide is such that the molar ratio of cyclohexylsulfenyl chloride to phthalimide is usually 0.5 to 3 times mol, preferably 0.8 to 1.5 times mole. When the molar ratio of cyclohexylsulfenyl chloride to phthalimide is 0.5 to 3 times mole, there is little unreacted phthalimide, and unreacted cyclohexylsulfenyl chloride is difficult to decompose. In the reaction of cyclohexylsulfenyl chloride and phthalimide, the amount of solvent used is usually 0.5 to 10 times by weight, preferably 1 to 5 times by weight, relative to phthalimide. When the amount of the solvent used is 0.5 to 10 times the weight of phthalimide, the yield is improved and the productivity is good. The reaction temperature is usually 0 to 100 ° C., preferably 10 to 80 ° C. When the reaction temperature is 0 to 100 ° C., the reaction is fast and N- (cyclohexylthio) phthalimide and cyclohexylsulfenyl chloride, which are target products, are not decomposed. The reaction time is usually 0.1 to 10 hours. Preferably, it is 1 to 5 hours. When the reaction time is 0.1 to 10 hours, the yield and productivity are high. The reaction pressure may be normal pressure or reduced pressure.

  Cyclohexylsulfenyl chloride and phthalimide are mixed in a solvent containing saturated hydrocarbons in a reactor with cyclohexylsulfenyl chloride and phthalimide.

  The reaction of cyclohexylsulfenyl chloride and phthalimide is preferably performed by adding a cyclohexylsulfenyl chloride solution to a phthalimide slurry or solution and mixing.

  In the reaction of cyclohexylsulfenyl chloride and phthalimide, a phthalimide slurry or solution is preferably added to the cyclohexylsulfenyl chloride solution and mixed.

  In the reaction of cyclohexylsulfenyl chloride and phthalimide, preferably, cyclohexylsulfenyl chloride and phthalimide are simultaneously added and brought into contact with each other and mixed.

  More preferably, the reaction of cyclohexylsulfenyl chloride and phthalimide is added to the solution or slurry of phthalimide in the reactor while maintaining the cyclohexylsulfenyl chloride solution at -30 ° C to 20 ° C.

  In the method for producing N- (cyclohexylthio) phthalimide of the present invention, since hydrogen chloride is by-produced in the reaction of cyclohexylsulfenyl chloride and phthalimide, a base is preferably used as a scavenger.

  The base may be an organic base, an inorganic base or a mixture thereof. The organic base is preferably a tertiary amine, and examples thereof include trimethylamine, triethylamine, tripropylamine, tributylamine, dimethylbenzylamine, N-methylmorpholine and the like. More preferred are triethylamine and dimethylbenzylamine. Examples of the inorganic base include metal hydroxides and metal oxides. The inorganic base is preferably an alkali metal hydroxide, alkaline earth hydroxide, or alkaline earth oxide. Specific examples include sodium hydroxide, potassium hydroxide, calcium hydroxide, and calcium oxide. More preferred are sodium hydroxide, potassium hydroxide and calcium hydroxide. The inorganic base may be used as an aqueous solution or a slurry in water.

  In the method for producing N- (cyclohexylthio) phthalimide of the present invention, the amount of the base to be preferably used is usually in the range of 0.7 to 3 times mol with respect to cyclohexylsulfenyl chloride. The amount of the base used is more preferably 0.9 to 2 times mol. More preferably, it is 1.0-fold mole to 1.5-fold mole.

  As for the use of the base, the whole amount is usually charged before starting the reaction. When the cyclohexylsulfenyl chloride solution is added to the phthalimide slurry, it may be continuously fed simultaneously with the addition of the cyclohexylsulfenyl chloride solution. Moreover, when using an inorganic base, you may make it react with the inorganic base to be used beforehand, phthalimide and a phthalimide salt like potassium phthalimide and sodium phthalimide, and it may make it react with cyclohexyl sulfenyl chloride, without using alone.

  In the method for producing N- (cyclohexylthio) phthalimide of the present invention, the mixture in the reactor is preferably in a solid-liquid non-uniform state. If the solid-liquid is in an inhomogeneous state, the solid component becomes a large lump, and liquid cyclohexylsulfenyl chloride is difficult to come into contact with phthalimide, but a large solid component lump cannot be formed by forcibly circulating the mixture externally. Therefore, the contact efficiency between the two raw materials is improved.

  In the method for producing N- (cyclohexylthio) phthalimide of the present invention, the mixture in the reactor is preferably at a high concentration. When the concentration is high, the solid component is easily formed, so that the contact efficiency is further improved.

  In the method for producing N- (cyclohexylthio) phthalimide of the present invention, it is more preferable that the raw material phthalimide, the salt derived from hydrogen chloride as a by-product or the target N- (cyclohexylthio) phthalimide is in a concentrated slurry state. The effect of improving contact efficiency is great.

  In the method for producing N- (cyclohexylthio) phthalimide of the present invention, cyclohexylsulfenyl chloride and phthalimide are mixed in a reactor, a part of the mixture is withdrawn out of the reactor, and the withdrawn mixture is further put into the reactor. To discharge.

  In the method for producing N- (cyclohexylthio) phthalimide of the present invention, preferably 0.01 to 10% of the mixture, more preferably 0.1 to 5% of the mixture is withdrawn from the reactor. The extracted mixture is discharged into the reactor.

  In the method for producing N- (cyclohexylthio) phthalimide according to the present invention, the contact efficiency between cyclohexylsulfenyl chloride and phthalimide is improved by externally circulating a part of the mixture.

  In the method for producing N- (cyclohexylthio) phthalimide of the present invention, preferably, a part of the mixture in the reactor is withdrawn from the bottom and discharged from a position higher than the liquid level of the reaction mixture in the reactor. A part of the mixture in the reactor is withdrawn from the bottom and discharged from a position higher than the liquid level of the reaction mixture in the reactor. Can be dispersed.

  In the method for producing N- (cyclohexylthio) phthalimide of the present invention, the vertical difference from the outlet at the bottom of the reactor to the outlet in the reactor is preferably 0.5 m or more. By setting the vertical height from the outlet at the bottom of the reactor to the outlet in the reactor to be 0.5 m or more, it is possible to improve the mixing failure between the upper part and the lower part due to lumps near the liquid level. it can.

  The apparatus for producing N- (cyclohexylthio) phthalimide of the present invention includes a rotary stirrer. The apparatus for producing N- (cyclohexylthio) phthalimide of the present invention is preferably a stirred tank reactor.

  The apparatus for producing N- (cyclohexylthio) phthalimide of the present invention has a charging port at the top of the reactor, and further has a discharge port at the bottom of the reactor and a discharge port at the top of the reactor. The spigot is connected by piping, and a liquid feed pump is installed in the middle of the piping.

  The piping used in the N- (cyclohexylthio) phthalimide production apparatus of the present invention is preferably capable of feeding a high-concentration reaction mixture. The inner diameter of the pipe is preferably 20 to 200 mm, more preferably 50 to 150 mm.

  The liquid feed pump used in the N- (cyclohexylthio) phthalimide production apparatus of the present invention is preferably capable of feeding a high-concentration reaction mixture. As the liquid feed pump, a spiral pump, a mixed flow pump, an axial pump, a reciprocating pump, a rotary pump, or the like is preferably used. More preferably, the liquid feed pump is a spiral pump.

  The apparatus for producing N- (cyclohexylthio) phthalimide of the present invention has a bottom portion of a tank reactor as an extraction port and a discharge port from the top of the reactor to the inside. The vertical difference from the outlet at the bottom of the reactor to the outlet of the reactor is preferably 0.5 m or more. The height difference in the vertical direction from the outlet to the outlet is more preferably 0.8 m or more, and further preferably 1.0 m or more. When the height difference is 0.5 m or more, the mixing improvement effect is high.

  The apparatus for producing N- (cyclohexylthio) phthalimide of the present invention preferably has a discharge port installed so as to discharge from a position higher than the liquid level of the reaction mixture in the reactor. Due to the positional relationship between the outlet and the outlet, an effective mixing effect can be obtained.

  In the apparatus for producing N- (cyclohexylthio) phthalimide of the present invention, cyclohexylsulfenyl chloride and phthalimide are mixed in a reactor, a part of the mixture is extracted out of the reactor, and the extracted mixture is further discharged into the reactor. The mixture is externally circulated to react cyclohexylsulfenyl chloride and phthalimide.

  The N- (cyclohexylthio) phthalimide produced according to the present invention is generally finally separated from the solvent to obtain N- (cyclohexylthio) phthalimide as a crystalline solid product.

  In the present invention, in general, in order to remove by-produced salts, bases, raw materials and the like, the reaction mixture is mixed with water, neutralized with an acid, and separated to obtain an oil layer containing N- (cyclohexylthio) phthalimide. Thereafter, the crystallization method is preferable for the isolation and purification of the product.

  The crystallization method includes, for example, a method of cooling and crystallizing an oil layer containing N- (cyclohexylthio) phthalimide, a method of concentrating and crystallizing the oil layer, a method of reprecipitation by adding a low-solubility solvent, or a combination thereof. The method etc. can be mentioned. Preferably, in the present invention, cooling and crystallization are performed, or cooling is performed by evaporation while concentrating. The crystallized crystals are filtered, separated from the mother liquor, and dried to remove the solvent. More preferably, it is crystallized by cooling in a solvent containing a saturated hydrocarbon.

  Hereinafter, the present invention will be described in more detail with reference to examples.

Reference example 1
In a stirred tank type glass-lined 3 m ³ reactor, 910 kg of dicyclohexyl disulfide (molecular weight 230.4, purity 94%, 3.71 kg mole) and toluene (boiling point 111 ° C.) / Cyclohexane (boiling point 81 ° C.) mixed solvent 1250 kg (toluene) 14 wt%, density 0.781 Kg / L, 1600 L), and cooled to −20 ° C. with a refrigerant. While stirring there, 303 kg of chlorine (molecular weight: 70.9, 4.27 kg mole) was blown in at a liquid temperature of −20 to −10 ° C. over 2.0 hours to chlorinate dicyclohexyl disulfide, and a solution of cyclohexylsulfenyl chloride. 2460 kg (molecular weight 150.7, cyclohexylsulfenyl chloride content 1120 kg, 7.43 kg mole) was obtained.

Reference example 2
The same procedure as in Reference Example 1 was performed except that 1340 kg of a mixed solvent of ethylene chloride (boiling point 83 ° C.) / Cyclohexane (20 wt% ethylene chloride, density 0.839 Kg / L, 1600 L) was used as the cyclohexylsulfenyl chloride synthesis solvent. Thus, 2550 kg (7.43 kg mole) of a cyclohexylsulfenyl chloride solution was obtained.

Example 1
The reaction vessel shown in FIG. 1 was used. To connect a pipe with an inner diameter of 100 mmφ from the bottom of the reactor to the top to a 6 m ³ reaction vessel made of a stirring tank type glass lining equipped with a rotary stirrer with a stirring blade at the bottom, and to circulate the mixture from the bottom to the top in the middle A liquid feed pump (spiral pump) was provided. The vertical difference from the outlet at the bottom of the reactor to the outlet at the top of the reactor was 1.56 m.

Into the reaction vessel, 1050 kg of phthalimide (molecular weight 147.1, 7.14 kg mole), 977 kg of triethylamine (molecular weight 101.2, 9.65 kg mole) and 1090 kg of mixed solvent of toluene / cyclohexane (toluene 14 wt%, density 0.781 kg) / L, 1400 L), and warmed to 60 ° C. with warm water. While stirring with a rotary stirrer (average rotation speed: 100 rpm), the raw material mixture was discharged with a liquid feed pump, and external circulation was started at an amount of 0.5 m ³ / min. The cyclohexylsulfenyl chloride solution 2460 Kg prepared in Reference Example 1 was supplied at a reaction temperature of 63 to 67 ° C. over 2.0 hours while being kept at −10 ° C., and then stirred and mixed at the same temperature for 0.5 hour. External circulation was continued to obtain a reaction mixture containing N- (cyclohexylthio) phthalimide, unreacted phthalimide, triethylammonium chloride and the like.

  In the latter half of the reaction, the mixture became a thick slurry of insoluble unreacted phthalimide, N- (cyclohexylthio) phthalimide and by-product triethylammonium chloride, but the liquid surface was vigorously mixed and up and down movement was observed. .

The mixture was transferred to the another stirred tank not equipped with external circulation apparatus glass lined 6 m ³ reactor, with stirring at a temperature 60 to 65 ° C., after dissolving the ammonium salt and the like added to hot water 1000 Kg, unreacted Insoluble matter such as phthalimide was filtered with a centrifuge. While stirring at a temperature of 60 to 65 ° C., neutralization was performed by adding sulfuric acid in order to remove excess triethylamine and the like in the filtrate into the aqueous layer. Next, stirring was stopped and the mixture was allowed to stand at a temperature of 60 to 65 ° C. to separate and discharge the lower aqueous layer. In order to remove the phthalimide remaining in the remaining oil layer, 48% by weight of caustic soda was added with stirring to stop stirring, and the aqueous layer was separated.

  The oil layer remaining in the post-treatment was cooled to 10 ° C. with stirring, and N- (cyclohexylthio) phthalimide was crystallized. The crystals were filtered and dried to obtain 1680 g of product (molecular weight 261.3, purity 99.0%, N- (cyclohexylthio) phthalimide content 1660 g, 6.35 Kg mol) and crystallization mother liquor 2700 Kg (N- (cyclohexylthio). ) A phthalimide content of 70 kg, 0.27 kg mol) was obtained. The total yield based on phthalimide was 93% (1730 Kg, 6.64 Kg mol), and the crystallization ratio of N- (cyclohexylthio) phthalimide in the product was 97%.

The product and mother liquor were analyzed by gas chromatography. The analysis conditions are as follows.
GC device: Shimadzu GC-17A
Column: NB-1, length 60 m × inner diameter 0.25 mmφ, film thickness 0.40 μm
Column temperature: 70 → 270 ° C., 5 ° C./min Carrier He gas: 180 kPa (70 ° C.)
Inlet / FID detector: 270 ° C.

Example 2
Using 1170 kg of a mixed solvent of ethylene chloride / cyclohexane (20% by weight of ethylene chloride, density of 0.838 Kg / L, 1400 L) as a synthesis solvent for N- (cyclohexylthio) phthalimide, 2550 kg of the cyclohexylsulfenyl chloride solution prepared in Reference Example 2 was used. A reaction was carried out in the same manner as in Example 1 except that it was used, followed by post-treatment.

  In the latter half of the reaction, the mixture became a thick slurry of insoluble unreacted phthalimide, N- (cyclohexylthio) phthalimide and by-product triethylammonium chloride, but the liquid surface was vigorously mixed and up and down movement was observed. .

  The oil layer remaining in the post-treatment was cooled to 10 ° C. with stirring, and N- (cyclohexylthio) phthalimide was crystallized. The crystals were filtered, washed with a small amount of solvent, and dried to obtain 1710 kg of product (purity 99.1%, N- (cyclohexylthio) phthalimide content 1700 kg, 6.50 kg mole) and crystallization mother liquor 2700 kg (N- ( (Cyclohexylthio) phthalimide content 72 kg, 0.28 kg mol). The total yield based on phthalimide was 95% (1770 Kg, 6.77 Kg mol), and the crystallization ratio of N- (cyclohexylthio) phthalimide in the product was 96%.

Comparative Example 1
A reaction was carried out in the same manner as in Example 1 except that a 6 m ³ reaction vessel made of stirring tank type glass lining without an external circulation device was used, and post-treatment was performed.

  In the second half of the reaction, the mixture becomes a concentrated slurry of unreacted unreacted phthalimide, N- (cyclohexylthio) phthalimide and by-product triethylammonium chloride, and the liquid level is swirled flatly only by stirring with a rotary stirrer. And there was almost no mixing up and down.

  As a result, 1580 g of product (purity 97.0%, N- (cyclohexylthio) phthalimide content 1530 g, 5.86 Kg mol) and crystallization mother liquor 2700 Kg (N- (cyclohexylthio) phthalimide content 73 Kg, 0.28 Kg mol) were obtained. did. The total yield based on phthalimide was 86% (1600 Kg, 6.13 Kg mol), and the crystallization ratio of N- (cyclohexylthio) phthalimide in the product was 96%.

Comparative Example 2
A reaction was carried out in the same manner as in Example 1 except that a 6 m ³ reaction vessel made of stirring tank type glass lining without an external circulation device was used, and post-treatment was performed.

  In the second half of the reaction, the mixture becomes a concentrated slurry of unreacted unreacted phthalimide, N- (cyclohexylthio) phthalimide and by-product triethylammonium chloride, and the liquid level is swirled flatly only by stirring with a rotary stirrer. So there was almost no mixing between the top and bottom.

  As a result, 1600 g of product (purity 97.5%, N- (cyclohexylthio) phthalimide content 1560 g, 5.97 kg mole) and crystallization mother liquor 2800 kg (N- (cyclohexylthio) phthalimide content 75 kg, 0.29 kg mole) were obtained. did. The total yield based on phthalimide was 88% (1635 Kg, 6.25 Kg mol), and the crystallization ratio of N- (cyclohexylthio) phthalimide in the product was 96%.

DESCRIPTION OF SYMBOLS 1 Reaction mixture main body 2 Reaction tank main body 3 Stirring blade 4 Piping extraction port 5 Liquid feed pump 6 Circulation piping 7 Piping discharge port 8 Rotating stirrer 9 Cyclohexylsulfenyl chloride charging port 10 Phthalimide charging port 11 Reaction mixture liquid surface

Claims (7)

In a solvent containing a saturated hydrocarbon, cyclohexylsulfenyl chloride and phthalimide are mixed in the reactor, a part of the mixture is extracted out of the reactor, and the extracted mixture is discharged into the reactor. A method for producing N- (cyclohexylthio) phthalimide in which N- (cyclohexylthio) phthalimide is synthesized by externally circulating the mixture and reacting cyclohexylsulfenyl chloride with phthalimide. The method for producing N- (cyclohexylthio) phthalimide according to claim 1, wherein the mixture in the reactor is in a solid-liquid heterogeneous state. The method for producing N- (cyclohexylthio) phthalimide according to claim 1 or 2, wherein a part of the mixture in the reactor is withdrawn from the bottom and discharged from a position higher than the liquid level of the reaction mixture in the reactor. The method for producing N- (cyclohexylthio) phthalimide according to claim 3, wherein the vertical difference from the outlet at the bottom of the reactor to the outlet in the reactor is 0.5 m or more. Equipped with a rotary stirrer, has a charging port at the top of the reactor, and has a discharge port at the bottom of the reactor and a discharge port at the top of the reactor, and the discharge port and discharge port are connected by piping. Equipped with a liquid feed pump in the middle of the process, cyclohexylsulfenyl chloride and phthalimide are mixed in the reactor, a part of the mixture is withdrawn out of the reactor, and the extracted mixture is discharged into the reactor. An apparatus for producing N- (cyclohexylthio) phthalimide in which cyclohexylsulfenyl chloride and phthalimide are reacted by externally circulating the mixture. The apparatus for producing N- (cyclohexylthio) phthalimide according to claim 5, wherein a vertical difference in height from the outlet to the outlet is 0.5 m or more. The apparatus for producing N- (cyclohexylthio) phthalimide according to claim 5 or 6, wherein the reactor is a stirred tank reactor.

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