JP6787199B2 - Method of recovering synthetic solvent - Google Patents

Description

The present invention relates to a method for recovering a synthetic solvent of N- (cyclohexylthio) phthalimide, which is a compound useful as a vulcanization retarder in a rubber vulcanization step. More specifically, a method for recovering a synthetic solvent of N- (cyclohexylthio) phthalimide is provided, which is industrially advantageous and has no problem in safe operation.

Generally, N- (cyclohexylthio) phthalimide is produced by reacting cyclohexylsulphenyl chloride and phthalimide in the presence of a base. Usually, in this production method, chlorine is used to synthesize the raw material cyclohexylsulphenyl chloride under strong acid conditions, and then the cyclohexylsulphenyl chloride and phthalimide are condensed under strongly basic conditions. Therefore, saturated hydrocarbons are used as a solvent that is stable to strong acids and strong bases and has a low environmental load. In synthesis on an industrial scale, the synthetic solvent is recovered and reused by distillation or the like in order to reduce manufacturing costs and effectively utilize resources.

This method causes a large physical loss of the solvent, and there is a risk of an accident during distillation recovery.

JP-A-2007-186438

An object of the present invention is to provide a method for recovering a synthetic solvent of N- (cyclohexylthio) phthalimide, which is industrially advantageous.

As a result of diligent studies on a method for solving the above problems, the present inventors have found that after synthesizing N- (cyclohexylthio) phthalimide, the synthetic solvent can be efficiently and safely recovered by a simple treatment. Reached.

That is, in the present invention, cyclohexylsulphenyl chloride and phthalimide are reacted in a saturated hydrocarbon solvent to synthesize N- (cyclohexylthio) phthalimide, and N- (cyclohexylthio) phthalimide is crystallized. This is a method for recovering a synthetic solvent in which a basic substance and water are added to a crystallization mother liquor after the crystals are separated, and the solvent is distilled in the presence of the basic substance and water.

According to the present invention, the synthetic solvent of N- (cyclohexylthio) phthalimide can be recovered industrially advantageously by adding a basic substance and water at the time of recovering the synthetic solvent.

The present invention reduces the physical loss of the synthetic solvent for N- (cyclohexylthio) phthalimide. Further, the present invention has a small risk of accidents during distillation recovery, and greatly contributes to stable operation on an industrial scale. The method for recovering a synthetic solvent of the present invention is very useful for industrial production of N- (cyclohexylthio) phthalimide.

The present invention will be described in detail below.

In the present invention, cyclohexylsulphenyl chloride is reacted with phthalimide in a solvent containing saturated hydrocarbons. The saturated hydrocarbon solvent used in the present invention is preferably a saturated hydrocarbon having 5 to 10 carbon atoms. More preferably, n-pentane, cyclopentane, n-hexane, cyclohexane, n-heptane, methylcyclohexane, n-octane, cyclooctane and the like can be mentioned. The saturated hydrocarbon solvent used in the present invention may be used as one kind of saturated hydrocarbon solvent, or may be used by mixing two or more kinds of saturated hydrocarbon solvents.

In the present invention, the saturated hydrocarbon can be used only with the saturated hydrocarbon. Further, the saturated hydrocarbon can be used by mixing with a solvent other than the saturated hydrocarbon. Examples of the solvent used by mixing with saturated hydrocarbons include aromatic hydrocarbons and chlorinated hydrocarbons. The aromatic hydrocarbon is preferably an aromatic hydrocarbon having 6 to 8 carbon atoms, and more preferably, toluene, xylene, ethylbenzene and the like can be mentioned. The chlorinated hydrocarbon is preferably a chlorinated hydrocarbon having 1 to 6 carbon atoms, and more preferably, ethylene dichloride, chlorobenzene and the like can be mentioned.

The cyclohexylsulphenyl chloride used in the method for recovering a synthetic solvent of the present invention is generally synthesized by a reaction of dicyclohexyl disulfide or cyclohexyl mercaptan with chlorine. When cyclohexylsulphenyl chloride is synthesized by the reaction of dicyclohexyl disulfide or cyclohexyl mercaptan with chlorine, the solvent is preferably a solvent containing a saturated hydrocarbon. More preferably, the same solvent as that used in the reaction between cyclohexylsulphenyl chloride and phthalimide is used.

The amount of chlorine used when synthesizing cyclohexylsulphenyl chloride by reacting dicyclohexyl disulfide or cyclohexyl mercaptan with chlorine is usually 0.5 to 2 times the molar amount, preferably 1 to 2 times the molar amount of the raw material sulfide or mercaptan. It is 1.5 times the mole. The amount of the solvent used is usually 0.5 to 10 times by weight, preferably 1 to 5 times by weight, based on dicyclohexyl disulfide or cyclohexyl mercaptan. The reaction temperature is usually −30 to 20 ° C., preferably −20 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 normal pressure, but may be under reduced pressure or under pressure. The reaction method is usually that dicyclohexyl disulfide or cyclohexyl mercaptan is dissolved in a solvent containing saturated hydrocarbon, and chlorine gas is blown into the solvent for synthesis.

In the method for recovering the synthetic solvent of the present invention, the cyclohexylsulphenyl chloride is used, for example, by holding the synthesized cyclohexylsulphenyl chloride at a low temperature. The storage temperature of cyclohexylsulphenyl chloride is usually −30 to 20 ° C., preferably −20 to 5 ° C.

The phthalimide used in the method for recovering the synthetic solvent of the present invention may be produced by any synthetic method. For example, a production method by reacting ammonia or urea with phthalic anhydride can be mentioned.

In the method for recovering the synthetic solvent of the present invention, the reaction conditions of cyclohexylsulphenyl chloride and phthalimide are such that the molar ratio of cyclohexylsulphenyl chloride to phthalimide is usually 0.5 to 3 times the molar ratio, preferably 0.8 to. It is 1.5 times the mole. When the molar ratio of cyclohexylsulphenyl chloride to phthalimide is 0.5 to 3 times the molar ratio, the amount of unreacted phthalimide is small, and unreacted cyclohexylsulphenyl chloride is difficult to decompose.

In the method for recovering the synthetic solvent of the present invention, the reaction temperature of cyclohexylsulphenyl chloride and phthalimide 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 the target N- (cyclohexylthio) phthalimide and cyclohexylsulphenyl chloride are not decomposed. The reaction time is usually 0.1 to 10 hours. It is preferably 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.

In the method for recovering a synthetic solvent of the present invention, in the reaction of cyclohexylsulphenyl chloride with phthalimide, the amount of the solvent used is usually 0.5 to 10 times by weight, preferably 1 to 5 times by weight, based on phthalimide. Is. When the amount of the solvent used is 0.5 to 10 times the weight of the phthalimide, the yield is improved and the productivity is good.

In the synthetic solvent recovery method of the present invention, the reaction of cyclohexylsulphenyl chloride with phthalimide is usually carried out by adding a cyclohexylsulphenyl chloride solution to a phthalimide slurry or solution, or by adding a phthalimide slurry or solution to a cyclohexylsulphenyl chloride solution. It can be added or added at the same time and contacted. The reaction of cyclohexylsulphenyl chloride with phthalimide preferably adds a thermally unstable cyclohexylsulphenyl chloride solution to the phthalimide solution or slurry in the reactor while keeping it at a low temperature of −30 to 20 ° C.

In the method for recovering a synthetic solvent of the present invention, hydrogen chloride is produced as a by-product in the reaction between cyclohexylsulphenyl chloride and phthalimide, so it is preferable that a base coexists as a scavenger. The base used 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, and N-methylmorpholine. More preferably, it is triethylamine or dimethylbenzylamine. Examples of the inorganic base include metal hydroxides and metal oxides. The inorganic base is preferably an alkali metal hydroxide, an alkaline earth hydroxide, or an alkaline earth oxide. Specific examples thereof include sodium hydroxide, potassium hydroxide, calcium hydroxide and calcium oxide. More preferably, sodium hydroxide, potassium hydroxide and calcium hydroxide. The inorganic base may be used as an aqueous solution or a slurry in water.

In the present invention, the amount of the base used in the reaction is usually in the range of 0.7 to 3 times the molar amount of cyclohexylsulphenyl chloride. The amount of the base used is preferably 0.9-fold to 2-fold. More preferably, it is 1.0 to 1.5 times mol. The total amount of base is usually charged before the reaction starts. When the cyclohexylsulphenyl chloride solution is added to the slurry of phthalimide, it may be continuously supplied at the same time as the addition of the cyclohexylsulphenyl chloride solution. When an inorganic base is used, it may not be used alone, but may be reacted with phthalimide in advance to synthesize a phthalimide salt such as potassium phthalimide or sodium phthalimide, and reacted with cyclohexylsulphenyl chloride.

In the present invention, the synthesized N- (cyclohexylthio) phthalimide is crystallized to obtain N- (cyclohexylthio) phthalimide. The obtained N- (cyclohexylthio) phthalimide is preferably a crystalline solid.

In the method for recovering a synthetic solvent of the present invention, in order to remove by-products such as salts, bases and raw materials, the reaction mixture is usually mixed with water, neutralized with an acid, and then separated to form N- (cyclohexylthio) phthalimide. Obtain an oil layer containing. In the present invention, N- (cyclohexylthio) phthalimide is preferably crystallized by cooling an oil layer containing N- (cyclohexylthio) phthalimide. The crystallized crystals can be filtered, separated from the mother liquor, and dried to remove the solvent. More preferably, in the present invention, it is cooled and crystallized in a solvent containing saturated hydrocarbons. The solvent to be removed during drying can be recovered by cooling with a condenser or the like for reuse.

In the present invention, N- (cyclohexylthio) phthalimide is crystallized to separate the crystals, and then the solvent in the crystallization mother liquor is distilled and recovered for reuse. At that time, it is important to add a basic substance and water to the crystallization mother liquor and distill the solvent in the presence of the basic substance and water.

The basic substance added in the step of distilling and recovering the solvent in the present invention may be an organic base, an inorganic base or a mixture thereof. The organic base is preferably an amine, and examples thereof include monoethanolamine, diethanolamine, triethanolamine, dimethylbenzylamine, and N-methylmorpholine. More preferably, it is triethanolamine or dimethylbenzylamine. Examples of the inorganic base include metal hydroxides and metal oxides. Preferred examples of the inorganic base include sodium hydroxide, potassium hydroxide, calcium hydroxide, and calcium oxide. More preferably, it is sodium hydroxide.

In the present invention, the amount of the basic substance added in the step of distilling and recovering the solvent is 0.1% by weight to 10% by weight with respect to the N- (cyclohexylthio) phthalimide remaining in the crystallization mother liquor. Preferably, it is 0.5% by weight to 5% by weight. When the addition amount is 0.1% by weight to 10% by weight, the effect of the present invention is large and the amount of residue to be discarded is reduced.

In the present invention, it is preferable that the residue remaining after distilling the solvent is basic. The residue is basic, that is, the hydrogen ion index pH is 7 or more, and the explosive decomposition of the residue can be suppressed.

In the present invention, the time for adding the basic substance in the step of distilling and recovering the solvent may be before distillation or during distillation. Since the effect of the basic substance increases as the concentration of the crystallization mother liquor progresses, it is desirable to add the solvent until the amount of the solvent is approximately half by weight. More preferably, the basic material is added before the start of distillation.

Examples of the water added in the step of distilling and recovering the solvent in the present invention include pure water, distilled water, ion-exchanged water, tap water, and seawater. Water may be added as an aqueous solution or a slurry in water together with the inorganic base added by distillation recovery. Further, water may be blown as water vapor. Water appears to be effective in expelling residual solvents and dispersing basic substances.

In the present invention, the amount of water added in the step of distilling and recovering the solvent is preferably 0.1% by weight to 1000% by weight with respect to the N- (cyclohexylthio) phthalimide remaining in the crystallization mother liquor. More preferably, it is 0.5% by weight to 100% by weight. When the addition amount is 0.1% by weight to 1000% by weight, the effect of the present invention is large, water distillation is small, and efficiency is high.

In the present invention, the time for adding water in the distillation recovery of the solvent may be before or during the distillation. However, since water is distilled off as the concentration of the crystallization mother liquor progresses, it is preferable to add it to the crystallization mother liquor at the time of distillation. More preferably, it is additionally added several times during distillation. Alternatively, it is added intermittently or continuously.

In the present invention, the basic substance added in the step of distilling and recovering the solvent is more preferably dissolved in water and added as an aqueous solution. More preferably, it is added as an aqueous solution of sodium hydroxide. The concentration of the aqueous sodium hydroxide solution is preferably 1 to 50%, more preferably 20 to 49%.

In the method for recovering the N- (cyclohexylthio) phthalimide synthetic solvent of the present invention, the internal temperature for distillation recovery of the solvent is usually 0 to 100 ° C., preferably 40 to 70 ° C.

The synthetic solvent distilled and recovered from the crystallization mother liquor in this manner has no particular problem in quality and can be reused for the reaction between cyclohexylsulphenyl chloride and phthalimide.

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

Reference example 1
A mixed solvent of 910 kg of dicyclohexyl disulfide (molecular weight 230.4, purity 94%, 3.71 kg mol) and toluene (boiling point 111 ° C.) / cyclohexane (boiling point 81 ° C.) 1250 kg (toluene) in a 3 m ³ reactor made of stirring tank type glass lining. 14% by weight, density 0.781 kg / L, 1600 L) was charged and cooled to −20 ° C. with a refrigerant. While stirring there, 303 kg of chlorine (molecular weight 70.9, 4.27 kg mol) was blown in at a liquid temperature of 20 to -10 ° C for 2.0 hours to chlorinate dicyclohexyldisulfide, and a solution of cyclohexylsulphenyl chloride. 2460 kg (molecular weight 150.7, cyclohexylsulphenyl chloride content 1120 kg, 7.43 kg mol) was obtained.

Reference example 2
Similar to Reference Example 1 except that 1340 kg of a mixed solvent of ethylene chloride (boiling point 83 ° C.) / cyclohexane (20% by weight of ethylene chloride, density 0.838 kg / L, 1600 L) was used as the cyclohexylphenyl chloride synthetic solvent. , A solution of cyclohexylsulphenyl chloride was obtained in an amount of 2550 kg (7.43 kg mol).

Example 1
Toluene 1050 kg (molecular weight 147.1, 7.14 kg mol), triethylamine 977 kg (molecular weight 101.2, 9.65 kg mol) in a stirring tank type glass lining 6 m ³ reactor equipped with a rotary stirrer with a stirring blade at the bottom. ) And 1090 kg of a mixed solvent of toluene / cyclohexane (14% by weight of toluene, density 0.781 kg / L, 1400 L) were charged and heated to 60 ° C. with warm water. While stirring there (average rotation speed 100 rpm), 2460 kg of the cyclohexylsulphenyl chloride solution prepared in Reference Example 1 was kept cold at −10 ° C. and supplied at a reaction temperature of 63 to 67 ° C. for 22.0 hours, and then supplied. Stirring was continued for 0.5 hours at the same temperature to obtain a reaction mixture containing N- (cyclohexylthio) phthalimide, unreacted phthalimide, triethylammonium chloride and the like.

While stirring at a temperature of 60 to 65 ° C., 1000 kg of warm water was added to the reaction mixture to dissolve ammonium salts and the like, and then unreacted phthalimide and the like were filtered. While stirring at a temperature of 60 to 65 ° C., sulfuric acid was added to neutralize the mixture in order to remove excess triethylamine and the like in the filtrate to the aqueous layer. Then, while stirring at a temperature of 60 to 65 ° C., 48% by weight caustic soda was added to separate the aqueous layer in order to remove the phthalimide remaining in the separated oil layer.

The oil layer remaining in the post-treatment was cooled to 10 ° C. with stirring to crystallize N- (cyclohexylthio) phthalimide. By filtering and drying the crystals (the solvent was recovered with a condenser during drying), 1680 g of the product (molecular weight 261.3, purity 99.0%, N- (cyclohexylthio) phthalimide content 1660 g, 6.35 kg mol). And 2600 kg of crystallization mother liquor (N- (cyclohexylthio) phthalimide content 70 kg, 0.27 kg mol) was obtained. The total yield with respect to phthalimide was 93% (1730 kg, 6.64 kg mol), and the crystallization rate of N- (cyclohexylthio) phthalimide in the product was 97%.

Next, 2.0 kg of a 48% sodium hydroxide aqueous solution (sodium hydroxide content 0.96 kg, water content 1.04 kg) was added to 2600 kg of the crystallization mother liquor, and the pressure was reduced from 300 mmHg (40 kPa) to 50 mmHg (6.7 kPa). , The mixture was heated from the outside with warm water at 82 ° C. and concentrated under reduced pressure until the internal temperature rose to 52 ° C., and when about 1000 kg of the solvent was distilled off, 1.0 kg of water was additionally added and the solvent was distilled and recovered. After separating the distilled water, the recovery solvent combined with the drying was 2240 kg (14% by weight of toluene). The amount of loss from the preparation was 100 kg, and the loss rate was 4.3%. Further, 360 kg of the residue concentrated under reduced pressure was filled in two iron drums (200 L) for disposal. A part (0.1 g) of the residue was collected, added to ion-exchanged water (10 mL) and mixed, and the pH was 10 and basic.

After the same reaction, post-treatment, crystallization, distillation recovery, and filling of the residue concentrated under reduced pressure into an iron drum can was repeated 4 to 5 times a day throughout the year. The iron drums filled with the residue were stored outdoors, but no abnormalities occurred in the drums.

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 x 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)
Injection port / FID detector: 270 ° C.

Example 2
Using 1170 kg of a mixed solvent of ethylene chloride / cyclohexane (20% by weight of ethylene chloride, density 0.838 kg / L, 1400 L) as an N- (cyclohexylthio) phthalimide synthetic solvent, 2550 kg of the cyclohexylsulphenyl 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, and post-treatment was performed.

The oil layer remaining in the post-treatment was cooled to 10 ° C. with stirring to crystallize N- (cyclohexylthio) phthalimide. The crystals are 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 mol) and 2700 kg of crystallization mother liquor (N- (N-). Cyclohexylthio) phthalimide content 72 kg, 0.28 kg mol). The total yield with respect to phthalimide was 95% (1770 kg, 6.77 kg mol), and the crystallization rate of N- (cyclohexylthio) phthalimide in the product was 96%.

Next, 1.0 kg of a 48% sodium hydroxide aqueous solution (sodium hydroxide content 0.48 kg, water content 0.52 kg) was added to 2700 kg of the crystallization mother liquor, concentrated under reduced pressure in the same manner as in Examples, and about 1000 kg of the solvent was distilled off. Then, 1.0 kg of 48% aqueous sodium hydroxide solution and 1.0 kg of water were additionally added, and the solvent was recovered by distillation. After separating the distilled water, the recovery solvent combined with the drying was 2440 kg (20% by weight of ethylene chloride). The amount of loss from the preparation was 70 kg, and the loss rate was 2.8%. Further, 260 kg of the residue concentrated under reduced pressure was filled in two iron drums (200 L) for disposal. A part (0.1 g) of the residue was collected, added to ion-exchanged water (10 mL) and mixed, and the pH was 11 and basic.

After the same reaction, post-treatment, crystallization, distillation recovery, and filling of the residue concentrated under reduced pressure into an iron drum can was repeated 4 to 5 times a day throughout the year. The iron drums filled with the residue were stored outdoors, but no abnormalities occurred in the drums.

Example 3
After reaction, post-treatment, and crystallization in the same manner as in Example 1 except that 1.0 kg of sodium hydroxide was added to the crystallization stock solution, 2600 kg of the crystallization stock solution (N- (cyclohexylthio) phthalimide content 70 kg) was added to the example. The solvent was distilled and recovered in the same manner as in 1. The recovered solvent combined with the drying was 2200 kg (14% by weight of toluene). The amount of loss from the preparation was 140 kg, and the loss rate was 6.0%. A part (0.1 g) of the residue was collected, added to ion-exchanged water (10 mL) and mixed, and the pH was 9 and basic.

Comparative Example 1
After reaction, post-treatment, and crystallization in the same manner as in Example 1 except that no basic substance was added to the crystallization stock solution, 2600 kg of the crystallization mother liquor (N- (cyclohexylthio) phthalimide content 70 kg) was applied to the example. The solvent was distilled and recovered in the same manner as in 1. The recovered solvent combined with the drying was 2100 kg (14% by weight of toluene). The amount of loss from the preparation was 240 kg, and the loss rate was 10%. A part (0.1 g) of the residue was collected and added to and mixed with ion-exchanged water (10 mL). As a result, it was acidic with pH 4 and not basic.

Comparative Example 2
After the reaction, post-treatment, and crystallization in the same manner as in Example 1 except that no basic substance was added to the crystallization stock solution, 2700 kg of the crystallization stock solution (N- (cyclohexylthio) phthalimide content 72 kg) was applied to Example 1. The solvent was distilled and recovered in the same manner as in the above. The recovered solvent combined with the drying was 2230 kg (20% by weight of ethylene chloride). The amount of loss from the preparation was 280 kg, and the loss rate was 11%. Further, 470 kg of the residue concentrated under reduced pressure was filled in two iron drums (200 L) for disposal. A part (0.1 g) of the residue was collected, added to ion-exchanged water (10 mL), and mixed. As a result, it was acidic with pH 3 and not basic.

After the same reaction, post-treatment, and crystallization, filling of the iron drum can with the residue concentrated under reduced pressure was repeated 4 to 5 times a day, and the iron drum can filled with the residue was stored outdoors. On the third day, a phenomenon was observed in which the internal temperature became higher than that of warm water during concentration under reduced pressure, suggesting that the residue during concentration may have decomposed and generated heat. After that, among the iron drums stored outdoors, the internal pressure of 6 of them increased and expanded, and corrosion was observed on a part of the outer surface, and it became clear that the residue decomposed. It caused a serious problem in safe operation.

Claims (5)

After reacting cyclohexylsulphenyl chloride with phthalimide in a solvent containing saturated hydrocarbon to synthesize N- (cyclohexylthio) phthalimide, crystallize N- (cyclohexylthio) phthalimide, and separate the crystals. , A method for recovering a synthetic solvent in which a basic substance and water are added to a crystallization mother liquor and the solvent is distilled in the presence of the basic substance and water. The method for recovering a synthetic solvent according to claim 1, wherein the basic substance is sodium hydroxide. The method for recovering a synthetic solvent according to claim 2, wherein an aqueous sodium hydroxide solution is added to the crystallization mother liquor. The method for recovering a synthetic solvent according to any one of claims 1 to 3, wherein water is added to the crystallization mother liquor at the time of distillation. The method for recovering a synthetic solvent according to any one of claims 1 to 4, wherein the residue remaining after distilling the solvent is basic.