JP2003040854A - Method for chlorosulfonyl isocyanate production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for high-purity chlorosulfonyl isocyanate production in a high yield efficiently and safely. SOLUTION: Cyanogen chloride A and sulfuric anhydrite B are subjected to condensation reaction (a first process) to give a reaction solution 4 containing crude chlorosulfonyl isocyanate. When chlorosulfonyl isocyanate 9 is separated by distillation (second and third processes) from the obtained reaction solution, decomposition treatment (a fourth process) of a residue 7 is carried out. Low- boiling fractions (5, 8, 10 and 11) obtained by the separation of chlorosulfonyl isocyanate by distillation and the decomposition treatment of the residue are recovered and reused for the condensation reaction between cyanogen chloride and sulfuric anhydrite.

Description

Detailed Description of the Invention

[0001]

The present invention relates to an intermediate raw material for producing medicines, agricultural chemicals, sweeteners, etc., or synthetic fibers,
The present invention relates to a method for producing chlorosulfonyl isocyanate, which is a compound useful as a modifier for synthetic resins and the like.

[0002]

2. Description of the Related Art Conventionally, as a method for producing chlorosulfonyl isocyanate, a method of adding sulfuric anhydride to liquid cyanogen chloride and conducting a condensation reaction under low temperature conditions of minus 50 ° C. or lower [Chem. Ber., 89, 1071] (1956); West German Patent 9288
No. 96 (1955)] or 10% of anhydrous sulfuric acid and cyanogen chloride.
A method of conducting a condensation reaction under a temperature condition of 0 ° C. or higher, for example, 100 to 200 ° C. [European Patent 294613B (1988);
Swiss Patent 680292A5 (1992)] has been reported.
However, in the case of the former method, a large amount (1.5 to 3 times mol) of liquid cyanogen chloride has to be used with respect to anhydrous sulfuric acid, which is uneconomical and due to the strong toxicity of cyanogen chloride. In addition, it is not suitable for industrial production from the viewpoint of safety, the isolation yield is low at 60 to 62%, and the quality (especially purity) of the final product, chlorosulfonyl isocyanate, is required by the market. There was a problem of not meeting. Further, in the latter method, not only is it difficult to control the flow rates of sulfuric anhydride and cyanogen chloride, but there are many by-products, so that the quality of chlorosulfonyl isocyanate in the final product obtained is similar to that of the former method. , There was a problem that it did not meet the market demand.

Therefore, as a method for producing chlorosulfonyl isocyanate which has solved these problems, a method of adding cyanogen chloride to liquid anhydrous sulfuric acid and conducting a condensation reaction while keeping the temperature of the reaction system at 20 to 50 ° C. JP 63-
77855), a method of simultaneously supplying cyanogen chloride and sulfuric anhydride to the reaction system while maintaining the temperature of the reaction system at 10 to 50 ° C. to carry out a condensation reaction (JP-A-1-228955), a chlorine-based hydrocarbon solvent. Among them, a method of causing a condensation reaction of cyanogen chloride and sulfuric anhydride (Japanese Patent Laid-Open No. 4-164063) has been proposed. According to these methods,
Chlorosulfonyl isocyanate can be obtained in a relatively high yield (74 to 91%) and a high purity (9
0-98%).

[0004]

However, in the above-mentioned methods 1 to 3, there is a problem that the decomposition batch processing operation for the by-products is dangerous, complicated and expensive. Specifically, the distillation residual liquid obtained by distilling and separating chlorosulfonyl isocyanate from the condensation reaction liquid of cyanogen chloride and sulfuric anhydride is transferred to another decomposition kettle and subjected to heat treatment to remove chlorosulfonyl isocyanate produced by decomposition. The process of recovering by distillation was essential. Here, distillation residual liquid is produced during the decomposition batch treatment operation, but these are discarded and do not contribute to the improvement of the yield.

Further, in the above-mentioned methods 1) to 3), a large amount of low-boiling fractions is not generated during the distillation separation of the desired product chlorosulfonyl isocyanate and the decomposition treatment of the distillation residual liquid. Since the reaction conditions were set, the low boiling point fraction was basically subject to disposal and was never reused.

Further, the quality (particularly the purity) required by the market is becoming higher than that of chlorosulfonyl isocyanate, and higher quality chlorosulfonyl isocyanate is produced in higher yield and at lower cost. There is a growing demand for ways to get it.

An object of the present invention is to solve the above-mentioned problems of the prior art, and specifically to provide a method for producing chlorosulfonyl isocyanate with high purity, high yield, efficiency and safety. It is to be.

[0008]

[Means for Solving the Problems] The inventors of the present invention perform decomposition treatment of a residual liquid obtained by distilling and separating chlorosulfonyl isocyanate, and also perform distillative separation of chlorosulfonyl isocyanate and decomposition / distillation treatment of a residual liquid. It was found that the above object can be achieved by recovering and reusing the obtained low boiling point fraction, and completed the present invention.

That is, according to the present invention, in the method for producing chlorosulfonyl isocyanate from cyanogen chloride and sulfuric anhydride, the following steps are carried out: (First step) Cyan chloride and sulfuric anhydride are subjected to a condensation reaction to give chlorosulfonyl isocyanate. A step of obtaining a condensation reaction liquid containing: (second step) the condensation reaction liquid obtained in the first step is distilled while heating under normal pressure to give a low boiling point fraction,
A step of separating a crude chlorosulfonyl isocyanate-containing fraction having a boiling point higher than that and a distillation residual liquid; (third step), the crude chlorosulfonyl isocyanate-containing fraction obtained in the second step under normal pressure A step of separating a low boiling point fraction, a purified chlorosulfonyl isocyanate fraction having a higher boiling point and a distillation residual liquid by distillation purification; and (the fourth step) the distillation obtained in the second step A step of separating the residual liquid into a distillate and a distillation residual liquid by distilling the residual liquid under heat treatment under normal pressure; and the purified chlorosulfonyl isocyanate fraction obtained in the third step Obtained as a sulfonyl isocyanate, a low boiling point fraction obtained in the second step, a low boiling point fraction obtained in the third step, a distillation residual liquid, and a recovered liquid obtained by mixing the distillate obtained in the fourth step. ,
Provided is a method for producing chlorosulfonyl isocyanate, which comprises introducing the condensation reaction between cyanogen chloride and sulfuric anhydride in the first step.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The method for producing chlorosulfonyl isocyanate of the present invention will be described in detail below for each step. Note that FIG. 1 shows a process flow of the manufacturing method of the present invention.

(First Step) The first step is a step of mixing cyanogen chloride (raw material A) and sulfuric anhydride (raw material B) to cause a condensation reaction to obtain a condensation reaction liquid containing chlorosulfonyl isocyanate. . The purpose of this step is to convert the reaction of cyanogen chloride and sulfuric anhydride into chlorosulfonyl isocyanate with good selectivity, and to adjust the concentration of chlorosulfonyl isocyanate in the reaction solution after the reaction to at least 80% by mass or more,
It is preferably 90% by mass or more. To this end, the main by-products, chloropyrosulfonyl isocyanate, 2,6-dichloro-1,4,
It is preferable to keep the production ratio of 3,5-oxathiadiazine-4,4-dioxide low, and to do so,
As described below, the condensation reaction temperature, the reaction ratio of cyanogen chloride and sulfuric anhydride, etc. may be adjusted.

As the sulfuric anhydride used in the present invention, industrially produced one can be used, and it is a γ-type sulfuric anhydride having a purity of 99% by mass or more in terms of reactivity. Those that can be particularly preferably used. The state of using sulfuric anhydride may be either a gas or a liquid, but it is more preferable to use it in a liquid state.

As the cyanogen chloride used in the present invention, it is preferable to use a highly pure one produced industrially from hydrocyanic acid and chlorine. The state of using cyanogen chloride may be either a gas or a liquid, but it is more preferable to use it in a gaseous state.

Regarding the raw material supply in the first step, as shown in FIG. 1, cyanogen chloride (1) and sulfuric anhydride (2) are
Each is supplied into the reaction system from a separate supply port. Each supply may be continuous or intermittent, but it is preferable to supply both continuously and simultaneously to the reaction system in order to suppress side reactions.

In the present invention, the low boiling fraction (5) obtained in the second step, the low boiling fraction (8) obtained in the third step, the distillation bottom liquid (10), and the fourth step in the present invention. The reaction solution is charged in advance with the recovered liquid (3) obtained by mixing the distillate (11) obtained in step 1, and the supply of cyanogen chloride (1) and sulfuric acid anhydride (2) is started with stirring or circulation. However, in the first reaction, if the low boiling point fractions (5) and (8), the distillation residual liquid (10) and the distillate (11) are not recovered,
Cyanide (1) and sulfuric acid (2) are supplied without charging the recovery liquid.

Whether the condensation reaction temperature in the first step is too low or too high, by-products such as chloropyrosulfonylsulfonyl isocyanate and 2,6-dichloro-1,4,3,5-
The formation ratio of oxathiadiazine-4,4-dioxide becomes high, the selectivity of chlorosulfonyl isocyanate in the first step decreases, and it adversely affects the steps after the second step. ℃, more preferably 2
It is 0 to 35 ° C.

The amount of cyanide (1) used in the condensation reaction in the first step (in the case of continuous supply, the amount used per unit time) is 0.8 to the amount of anhydrous sulfuric acid (2). It is 1.3 mole times, preferably 0.9 to 1.1 mole times. If it is out of this range, the formation ratio of by-products is significantly increased, the selectivity of chlorosulfonyl isocyanate in the first step is lowered, and further crystal precipitation occurs in the reaction system, which makes liquid flow difficult. However, it may be difficult to remove heat, which may make it difficult to control the reaction temperature in the first step.

When the condensation reaction time in the first step is within a range that can satisfy the above temperature conditions and supply molar ratio conditions, the time when the supply of cyanogen chloride (1) and sulfuric anhydride (2) is completed is completed. Then, since the substantial condensation reaction is completed, there is no need to particularly limit it. The condensation reaction liquid (4) after completion of the reaction can be immediately transferred to the next second step.

The condensation reaction liquid (4) contains, in addition to the desired product, chlorosulfonyl isocyanate, the starting material anhydrous sulfuric acid and starting material cyanide chloride having a lower boiling point, and chloropyrolide which is a higher boiling by-product. Sulfonyl isocyanate,
It may contain 2,6-dichloro-1,4,3,5-oxathiadiazine-4,4-dioxide, di (chlorosulfonyl) ether, sulfonyldiisocyanate. Among the by-products, chloropyrosulfonyl isocyanate can be thermally decomposed into chlorosulfonyl isocyanate and sulfuric anhydride, and 3,5-oxathiadiazine-4,4-dioxide is chlorosulfonyl isocyanate and cyanogen chloride. It can be thermally decomposed. However, it is known that chlorosulfonyl isocyanate cannot be obtained from di (chlorosulfonyl) ether and sulfonyl diisocyanate under ordinary thermal decomposition conditions.

(Second step) In the second step, the condensation reaction liquid (4) obtained in the first step is distilled while heating under normal pressure to give a low boiling fraction (cyanide chloride, sulfuric anhydride, (Sulfur dioxide, sulfuryl chloride, etc.) (5), a crude chlorosulfonyl isocyanate-containing fraction (6) having a boiling point higher than that (5), and a distillation residual liquid (7) containing the above-mentioned high boiling by-product. This is the step of separating. In this step, the operation of "distilling while heating under normal pressure" is carried out, and the thermal decomposition of the high-boiling-point by-product contained in the condensation reaction solution obtained in the first step and the crude chlorosulfonylisocyanate are carried out. The separation of the nato is carried out in a heat-processable reactor equipped with a distillation column which is usually used in industry.

Regarding the heat treatment conditions in the second step, if the temperature of the condensation reaction liquid is too low, the decomposition of by-products is not sufficient,
If it is too high, on the contrary, side reactions occur and the formation of high-boiling substances becomes conspicuous. Therefore, the temperature is preferably 80 to 130 ° C. At the time of heating, the low boiling point fraction (5) is distilled off at 80 ° C → 13
Heat to gradually increase to 0 ° C.

The heat treatment time is set to at least 5 hours or more, preferably 10 to 20 hours under a predetermined temperature condition.

The low boiling fraction (5) is preferably 100 ° C.
It is mainly composed of a fraction having a boiling point of less than 100.degree. C. Therefore, a fraction having a distillation temperature of less than 100.degree. C., preferably 90.degree. The distillation amount of the low boiling point fraction (5) is preferably 5 to 30% by mass, more preferably 5 to 20% by mass, relative to the charged amount of the condensation reaction liquid (4).

The low boiling point fraction (5) thus obtained is used as a recovery liquid (3) in the next reaction of the first step, as will be described later.

The crude chlorosulfonyl isocyanate-containing fraction (6) is preferably a fraction having a boiling point of 100 to 110 ° C., and therefore a fraction having a distillation temperature of 100 to 110 ° C., preferably 105 to 108 ° C. is collected. Good. The distillate amount of the crude chlorosulfonyl isocyanate-containing fraction (6) is preferably 50 to 80 of the charged amount of the condensation reaction liquid (4).
It is mass%, preferably 60 to 75 mass%.

The crude chlorosulfonyl isocyanate-containing fraction (6) thus obtained exhibits a purity of at least 98% or higher, usually 99% or higher at this stage, and in order to be purified by distillation, the following third step is carried out. Be transferred to.

The amount of the distillation residual liquid (7) remaining in the distillation pot is preferably 1 with respect to the charged amount of the condensation reaction liquid (4).
It is 0 to 40% by mass, more preferably 15 to 25% by mass.

The distillation residual liquid (7) is transferred to the fourth step described later.

(Third step) In the third step, the crude chlorosulfonyl isocyanate-containing fraction (6) obtained in the second step is
Low boiling fraction (8) by distillation and purification under normal pressure
And a purified chlorosulfonyl isocyanate fraction (9) having a boiling point higher than that and a distillation residual liquid (10). In this step, 99% of the crude chlorosulfonyl isocyanate-containing fraction (6) obtained in the second step was obtained by the operation of "distillation and purification under normal pressure".
%, A purified chlorosulfonyl isocyanate fraction (9) as a high-purity chlorosulfonyl isocyanate for the purpose, and a distillation residual liquid (10) containing a low-boiling fraction (8) as an impurity and a high-boiling by-product. Is carried out in a heat-processable reactor equipped with a distillation column usually used in industry.

Since the heating condition for the distillation and purification in the third step may be the temperature required for the distillation and purification of almost pure chlorosulfonyl isocyanate, it is preferably 10 under normal pressure.
The temperature is 0 ° C to 120 ° C, more preferably 105 ° C to 115 ° C.

The low boiling fraction (8) is preferably 104 ° C.
It is mainly composed of a fraction having a boiling point of less than 1, and therefore, a fraction having a distillation temperature of less than 104 ° C, preferably less than 106 ° C may be collected. The distillate amount of the low boiling point fraction (8) is preferably 5 to 20% by mass, more preferably 5 to 1% by mass of the crude chlorosulfonyl isocyanate-containing fraction (6).
It is 5% by mass.

The low boiling point fraction (8) thus obtained is used as a recovery liquid (3) in the next reaction of the first step, as will be described later.

The purified chlorosulfonyl isocyanate fraction (9) is preferably a fraction having a boiling point of 104 to 110 ° C, more preferably 106 to 108 ° C, and therefore has a distillation temperature of 104 to 110 ° C, preferably 106 to 110 ° C. The 108 ° C. fraction should be collected. The amount of the purified chlorosulfonyl isocyanate distillate (9) to be distilled off is preferably 60 of the amount of the crude chlorosulfonyl isocyanate-containing distillate (6) charged.
˜85% by mass, preferably 65-85% by mass. Obtained purified chlorosulfonyl isocyanate distillate (9)
Is the desired product of high-purity chlorosulfonyl isocyanate.

Distillation residual liquid (10) remaining in the still pot
The amount of is preferably 5 to 40% by mass, more preferably 5 to 25% by mass of the amount of the crude chlorosulfonyl isocyanate-containing fraction (6) charged.

The distillation residual liquid (10) is returned to the first step as the recovery liquid (3), but if necessary, it is distilled while being heat-treated under normal pressure in the same manner as in the fourth step described later, and the distillate is obtained. May be used as the recovery liquid (3).

(Fourth Step) In the fourth step, the distillation residual liquid (7) obtained in the second step is distilled while being heat-treated under normal pressure to obtain a distillate (11) and a distillation residual liquid ( It is a step of separating into 12) and. In addition, the heat treatment and distillation of the distillation residual liquid (10) in the third step, which is performed as necessary, are combined with this step, and the distillation residual liquid (7) in the second step and the distillation residual liquid (10) in the third step are combined. ) May be subjected to heat treatment and distillation. In this step, a distillate (11) which can be reused for the reaction by thermally decomposing the high-boiling-point by-product contained in the distillation residue by the operation of "distilling while heat-treating under normal pressure" is used. The recovery is carried out in a heat-processable reactor equipped with a distillation column which is usually used in industry.

With respect to the heat treatment conditions in the fourth step, if the temperature of the distillation residual liquid is too low, the thermal decomposition of the high-boiling point by-product is not sufficient, and if it is too high, a side reaction takes place on the contrary and a high-boiling point substance is produced. Since it becomes remarkable, it is preferably 100 ° C to 140 ° C. When heated, the distillate (11) is heated to 100
Heat to gradually increase from ℃ to 140 ℃.

The heat treatment time is set to be at least 10 hours or more, preferably 10 to 30 hours under a predetermined temperature condition.

The distillate (11) is mainly composed of a fraction having a boiling point of less than 120 ° C. Therefore, a fraction having a distillation temperature of less than 120 ° C., preferably 110 ° C. or less may be collected. . The distillate amount of the distillate (11) is preferably 70 to 90% by mass, more preferably 75 to 85% by mass of the charged amount of the distillation residual liquid.

The obtained distillate (11) is used as the recovered liquid (3) in the next reaction of the first step as described above.

Distillation residual liquid (1
The amount of 2) is preferably 10 times the charged amount of the distillation residual liquid.
-30 mass%, more preferably 15-25 mass%.

The distillation residual waste liquid (12) is left as it is in the distillation pot, and is decomposed by heat again in the next heat decomposition treatment or hydrolyzed to waste.

[0043]

EXAMPLES The present invention will be specifically described below with reference to examples.

The purity of chlorosulfonyl isocyanate is determined by a method in which water is gradually added dropwise to chlorosulfonyl isocyanate prepared as a methylene chloride solution to decompose it and the produced sulfamic acid and hydrochloric acid are titrated with an aqueous sodium hydroxide solution. I asked.

Example 1 (First Step) The recovered liquid (3) 1792 was added to the reaction tank of the first step.
After charging kg, the temperature in the reaction system is set to 25 to 3 under cooling circulation.
Cyan chloride (1) 1260k while maintaining at 0 ° C
1640 kg of g and gamma-type sulfuric anhydride (2) were simultaneously introduced into the reaction system over 7 hours. After the completion, 4692 kg of the obtained condensation reaction liquid (4) was transferred to the reaction tank of the second step.

(Second step) Condensation reaction liquid (4) 4692k
g in a liquid temperature range of 80 to 120 ° C., and a fraction having a distillation temperature of less than 100 ° C. over 1 hour was filled with a glass Raschig ring (diameter 10 mm) to have a diameter of 38 cm and a height of 4.6.
Separation using a 7 m packed column, low boiling fraction (5) 326
I got kg. Then, similarly, the liquid temperature is heated in the range of 80 to 120 ° C., and the distillation temperature is 100 to 110 ° C. for 10 hours.
Was separated, and the obtained crude chlorosulfonyl isocyanate-containing fraction (6) 3428 kg was transferred to the reaction tank of the third step. 326 kg of the low boiling fraction (5) was transferred to the reaction recovery storage tank.

938 kg of the distillation residual liquid (7) remaining in the kettle was transferred to the reaction tank of the fourth step.

(Third step) 3428 kg of a crude chlorosulfonyl isocyanate-containing fraction (6) was added at a liquid temperature of 100 to 12
Heating in the range of 0 ° C., the low boiling point having a distillation temperature of less than 106 ° C. over 5 hours is separated using a packed column having a diameter of 38 cm and a height of 4.67 m filled with glass Raschig rings (diameter 10 mm), 356 kg of a low boiling fraction (8) was obtained. Then, similarly, the liquid temperature is heated in the range of 105 to 115 ° C.
The fraction having a distillation temperature of 106 to 108 ° C is separated over time,
Purified chlorosulfonyl isocyanate fraction (9) 272
9 kg (purity 99.8%) was obtained as a product. Yield is 9
It was 4.8% (based on the cyanide chloride used).

356 kg of the low boiling fraction (8) was transferred to the reaction recovery storage tank. Distillation residual liquid remaining in the kettle (10) 343
kg was also transferred to the reaction recovery storage tank.

(Fourth step) 938 kg of the distillation residual liquid (7) remaining in the kettle of the second step is heated at a liquid temperature in the range of 100 to 130 ° C., and a distillate temperature of less than 110 ° C. is spent for 12 hours. Was separated using a packed column with a diameter of 38 cm and a height of 4.67 m packed with glass Raschig rings (diameter 10 mm),
767 kg of distillate (11) was obtained. 171 kg of the distillation residual liquid (12) remaining in the kettle was discarded.

767 kg of the distillate (11) was transferred to the reaction recovery storage tank, and the total amount of the recovered liquid (3) in the reaction recovery storage tank was 1
792 kg (breakdown: low-boiling fraction (5) 326 kg + low-boiling distillate (8) 356 kg + distillation residual liquid (10) 343 kg)
+ Distillate (11) (767 kg) was confirmed, and then transferred to the reaction tank of the first step.

[0052]

EFFECTS OF THE INVENTION According to the present invention, the productivity of chlorosulfonyl isocyanate can be significantly improved by using cyanogen chloride and sulfuric anhydride as starting materials, and high purity, high yield, and industrially Chlorosulfonyl isocyanate can be obtained in a very simple manner.

Further, if the series of steps from the first step to the fourth step is closed cycle, the safety and convenience of the production method can be further enhanced, and the thermal decomposition in the fourth step or the distillation residue thereof can be performed. Repeated thermal decomposition by accumulating liquid greatly reduces the amount of waste liquid containing toxic compounds at high concentrations.

Further, since the amount of the waste liquid is reduced, it is necessary to complete the decomposition, which is complicated, and it is possible to reduce the hydrolysis treatment operation of the waste liquid which is accompanied by the risk of leakage and generation of cyan gas.

[Brief description of drawings]

FIG. 1 is a process flow chart of the present invention.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kazunari Kon             2-28 Kurashiki-cho, Nakajo-cho, Kitakanbara-gun, Niigata Prefecture             Inside the ceremony company Kuraray (72) Inventor Masaki Iwata             2-28 Kurashiki-cho, Nakajo-cho, Kitakanbara-gun, Niigata Prefecture             Inside the ceremony company Kuraray F-term (reference) 4H006 AA02 AD11 BC51 BD40 BD52                       BD60 BD84 BE43 BE90

Claims (4)

[Claims] 1. A method for producing chlorosulfonyl isocyanate from cyanogen chloride and sulfuric anhydride, which comprises the following steps: (first step) condensation reaction of cyanogen chloride and sulfuric anhydride to give a condensation containing chlorosulfonyl isocyanate. Step of obtaining reaction solution; (Second step) By distilling the condensation reaction solution obtained in the first step while heating under normal pressure, a low boiling point fraction,
A step of separating a crude chlorosulfonyl isocyanate-containing fraction having a boiling point higher than that and a distillation residual liquid; (third step), the crude chlorosulfonyl isocyanate-containing fraction obtained in the second step under normal pressure A step of separating a low boiling point fraction, a purified chlorosulfonyl isocyanate fraction having a higher boiling point and a distillation residual liquid by distillation purification; and (the fourth step) the distillation obtained in the second step A step of separating the residual liquid into a distillate and a distillation residual liquid by distilling the residual liquid under heat treatment under normal pressure; and the purified chlorosulfonyl isocyanate fraction obtained in the third step Obtained as a sulfonyl isocyanate, a low boiling point fraction obtained in the second step, a low boiling point fraction obtained in the third step, a distillation residual liquid, and a recovered liquid obtained by mixing the distillate obtained in the fourth step. ,
A method for producing chlorosulfonyl isocyanate, which comprises adding to the condensation reaction between cyanogen chloride and sulfuric anhydride in the first step. 2. In the second step, the heat treatment is to heat the condensation reaction liquid to 80 to 130 ° C., and the low-boiling fraction is mainly a fraction having a boiling point of less than 100 ° C. The production method according to claim 1, wherein the chlorosulfonyl isocyanate-containing fraction is mainly composed of a fraction having a boiling point of 100 to 110 ° C. 3. In the third step, the low boiling point fraction has a boiling point of 1
The main component is a fraction below 04 ° C, and the purified chlorosulfonyl isocyanate fraction has a boiling point of 104 to 110 ° C.
3. The production method according to claim 1 or 2, which is mainly composed of the fraction. 4. The production method according to claim 1, wherein in the fourth step, the heat treatment is to heat the mixed distillation residual liquid to 100 to 140 ° C.