A method for preparing storage-resistant water-insoluble isothiazolinone

Abstract

The invention provides a method for preparing a storage-resistant water-insoluble isothiazolinone, and belongs to the technical field of chemical synthesis. The invention first uses N,N'-di-n-octyl dithiodipropionamide, a chlorinated solvent and chlorine as raw materials for chlorination reaction to prepare 2-n-octyl isothiazolin-3-ketone OIT and / or 4,5-dichloro-2-n-octyl isothiazolin-3-ketone DCOIT finished products with less impurity content, thereby reducing the discoloration reaction caused by impurities; the product is then mixed with a stabilizer, and the inhibitory effect of the stabilizer on the free radical discoloration process is utilized to finally obtain a storage-resistant water-insoluble isothiazolinone, thereby solving the problem of discoloration of the water-insoluble isothiazolinone during storage.

Description

Technical Field

[0001] The invention relates to the technical field of chemical synthesis, and in particular to a method for preparing storage-resistant water-insoluble isothiazolinone. Background Art

[0002] Isothiazolinone is a broad-spectrum, highly effective, low-toxic, non-oxidizing biocide. It has a strong inhibitory and killing effect on common bacteria, fungi, algae, etc. It has high killing efficiency, good degradability, no residue, safe operation, good compatibility, and low use cost. OIT (2-octylisothiazoline-3-one) and DCOIT (4,5-dichloro-2-octylisothiazoline-3-one) are also isothiazolinone fungicides. Due to their long carbon chain structure, they are water-insoluble isothiazolinones and are often used in coatings, leather, and pesticides as bactericides and mildew inhibitors.

[0003] The synthesis methods of OIT and DCOIT have been reported in patents, such as CN112159365. There are many studies on the stabilization of water-soluble isothiazolinones (such as 2-methylisothiazolin-3-one, 5-chloro-2-methylisothiazolin-3-one), such as CN1138038 and CN102783483. In order to avoid the degradation of the active ingredients of water-soluble isothiazolinone products, a large amount of stabilizers, such as magnesium nitrate, are usually added to the water-soluble isothiazolinone to avoid the failure of the active ingredients of the product. However, the finished products of OIT or DCOIT (active ingredient content is not less than 98%) are different from them. The active ingredient content does not decrease significantly during storage (the active ingredient content is still greater than 95% after 2 years of storage). Therefore, there are few studies on the stabilization methods of water-insoluble isothiazolinones.

[0004] European Patent EP0490565 discloses that an organic copper salt, such as copper dodecylbenzenesulfonate, copper dioctyl sulfosuccinate or copper petroleum sulfonate, is added as a stabilizer to a composition containing a water-insoluble 3-isothiazolone compound to avoid a reduction in the content of the isothiazolinone compound due to degradation.

[0005] Unlike water-soluble isothiazolinone, the appearance of OIT-98 and DCOIT-98 products will undergo obvious browning during storage as the storage time increases, affecting the sales of the products. Although there have been relevant studies on the degradation of isothiazolinone compounds (Ref: Zhang Chunyan, Yu Liangmin, Zhang Zhiming. Research Progress on Degradation and Ecotoxicological Behavior of Isothiazolinone Compounds [J]. Shanghai Coatings, 2008, 46 (11): 34-36.), there are no literature reports on the discoloration mechanism of isothiazolinone compounds, especially water-insoluble isothiazolinone, and there is no clear reference information on stabilizers that prevent the storage discoloration of water-insoluble isothiazolinone. Summary of the invention

[0006] The object of the present invention is to provide a method for preparing a storage-resistant water-insoluble isothiazolinone. The method provided by the present invention prepares a storage-resistant water-insoluble isothiazolinone, thereby solving the problem of discoloration of the water-insoluble isothiazolinone during storage.

[0007] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0008] The present invention provides a method for preparing a storage-resistant water-insoluble isothiazolinone, which is characterized by comprising the following steps:

[0009] (1) using N,N'-dioctyldithiodipropionamide, a chlorinated solvent and chlorine as raw materials to carry out a chlorination reaction to prepare 2-n-octylisothiazoline-3-one OIT and / or 4,5-dichloro-2-n-octylisothiazoline-3-one DCOIT finished products;

[0010] (2) The OIT / DCOIT product obtained in step (1) is mixed with a stabilizer to obtain a storage-resistant water-insoluble isothiazolinone.

[0011] Preferably, in the step (1), the chlorination reaction is stopped when the content of N,N'-di-n-octyl dithiodipropionamide in the system is 0.01 wt% to 0.05 wt%.

[0012] Preferably, the content of N,N'-di-n-octyl dithiodipropionamide in the finished OIT or DCOIT product in step (1) is less than 60 ppm.

[0013] Preferably, the preparation of the OIT finished product in step (1) comprises the following steps:

[0014] Mixing N,N'-dioctyl dithiodipropionamide and a chlorinated solvent, heating, introducing chlorine gas and chlorination reaction in sequence, stopping the reaction when the content of N,N'-dioctyl dithiodipropionamide is 0.01wt% to 0.05wt% by sampling liquid phase detection, cooling, first filtering and eluting in sequence to obtain a filter cake and a mother liquor;

[0015] The filter cake is suspended in chlorobenzene, neutralized with 20% sodium hydroxide solution, and separated to obtain an organic layer;

[0016] The organic layer is sequentially washed with water, distilled and filtered for a second time to obtain an OIT finished product.

[0017] Preferably, the temperature of the chlorination reaction is 45-55° C., and the speed of introducing chlorine gas is 100-140 kg per hour.

[0018] Preferably, the preparation of the DCOIT finished product in step (1) comprises the following steps:

[0019] Mixing N,N'-dioctyl dithiodipropionamide and a chlorinated solvent, heating, introducing chlorine gas and chlorination reaction in sequence, stopping the reaction when the content of N,N'-dioctyl dithiodipropionamide is 0.01wt% to 0.05wt% by sampling liquid phase detection, cooling, first filtering and eluting in sequence to obtain a filter cake and a mother liquor;

[0020] The filter cake is suspended in chlorobenzene, neutralized with 20% sodium hydroxide solution, and separated to obtain an organic layer;

[0021] The organic layer is azeotropically dehydrated to a water content of less than 0.2%, and then combined with the mother liquor, and the temperature is raised, chlorine is introduced, and a re-chlorination reaction is performed in sequence. When the content of N, N'-di-n-octyl dithiodipropionamide in the sampled liquid phase is controlled to be 0.01wt% to 0.05wt%, the re-chlorination reaction is stopped, and desolventizing, methanol recrystallization, filtering, eluting and drying are performed in sequence to obtain a DCOIT finished product.

[0022] Preferably, the temperature of the re-chlorination reaction is 55-65° C., and the speed of introducing chlorine gas is 50-80 kg per hour.

[0023] Preferably, the stabilizer in step (2) is selected from one or more of 2,6-di-tert-butyl-p-cresol BHT, bis-2,2,6,6-tetramethylpiperidinol sebacate LS-770, dilauryl thiodipropionate DLTP, bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite THP-24, and the like.

[0024] Preferably, the concentration of the stabilizer in the storage-stable water-insoluble isothiazolinone in step (2) is 10 to 500 ppm.

[0025] Preferably, the concentration of the stabilizer in the storage-stable water-insoluble isothiazolinone in step (2) is 50 to 100 ppm.

[0026] The invention provides a method for preparing a storage-resistant water-insoluble isothiazolinone. The method comprises the following steps: firstly, N,N'-di-n-octyldithiodipropionamide, a chlorinated solvent and chlorine are used as raw materials for a chlorination reaction to prepare a 2-n-octylisothiazoline-3-one OIT and / or a 4,5-dichloro-2-n-octylisothiazoline-3-one DCOIT finished product with a low impurity content; and then the finished product is mixed with a stabilizer. The inhibitory effect of the stabilizer on the free radical discoloration reaction is utilized to enhance the inhibitory effect on the discoloration phenomenon caused by the free radical, and finally the storage-resistant water-insoluble isothiazolinone is obtained, thereby solving the problem of discoloration of the water-insoluble isothiazolinone during storage. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a liquid phase spectrum of the OIT finished product prepared in Comparative Example 1 of the present invention;

[0028] Figure 2 This is a liquid phase spectrum of the DCOIT finished product prepared in Comparative Example 2 of the present invention;

[0029] Figure 3 This is a liquid phase spectrum of the OIT product prepared in Comparative Example 3 of the present invention;

[0030] Figure 4 This is the liquid phase spectrum of the DCOIT product prepared in Comparative Example 4 of the present invention;

[0031] Figure 5 The physical pictures of the storage-stable water-insoluble isothiazolinone OIT products prepared in Examples 1 and 2 and the OIT finished products prepared in Comparative Examples 1 and 3 after heat stabilization, wherein: Figure 5 a, b and c are thermally stable for 0, 14 and 28 days respectively. Figure 5 From left to right in a / b / c are Example 1, Example 2, Comparative Example 1 and Comparative Example 3;

[0032] Figure 6 The physical pictures of the storage-stable water-insoluble isothiazolinone DCOIT products prepared in Examples 3 and 4 and the OIT finished products prepared in Comparative Examples 2 and 4 after heat stabilization, wherein: Figure 6 a, b and c are thermally stable for 0, 14 and 28 days respectively. Figure 6 From left to right in a / b / c are Example 3, Example 4, Comparative Example 2 and Comparative Example 4 respectively. DETAILED DESCRIPTION

[0033] The present invention provides a method for preparing a storage-resistant water-insoluble isothiazolinone, which is characterized by comprising the following steps:

[0034] (1) using N,N'-dioctyldithiodipropionamide, a chlorinated solvent and chlorine as raw materials to carry out a chlorination reaction to prepare 2-n-octylisothiazoline-3-one OIT and / or 4,5-dichloro-2-n-octylisothiazoline-3-one DCOIT finished products;

[0035] (2) The OIT / DCOIT product obtained in step (1) is mixed with a stabilizer to obtain a storage-resistant water-insoluble isothiazolinone.

[0036] In the present invention, unless otherwise specified, the raw materials used are conventional commercial products in the art.

[0037] In the present invention, the chlorination reaction is stopped when the content of N,N'-di-n-octyl dithiodipropionamide in the system is preferably 0.01 wt% to 0.05 wt%.

[0038] In the present invention, the content of N,N'-di-n-octyl dithiodipropionamide in the finished OIT or DCOIT product is preferably less than 60ppm, more preferably less than 20ppm. The present invention controls the content of N,N'-di-n-octyl dithiodipropionamide in the finished OIT or DCOIT product within the above range, controls the raw materials within a reasonable range, avoids the decomposition of the raw materials to generate free radicals, and reduces the degree of discoloration during product storage.

[0039] In the present invention, the preparation of the OIT finished product preferably includes the following steps:

[0040] Mixing N,N'-dioctyl dithiodipropionamide and a chlorinated solvent, heating, introducing chlorine gas and chlorination reaction in sequence, stopping the reaction when the content of N,N'-dioctyl dithiodipropionamide is 0.01wt% to 0.05wt% by sampling liquid phase detection, cooling, first filtering and eluting in sequence to obtain a filter cake and a mother liquor;

[0041] The filter cake is suspended in chlorobenzene, neutralized with 20% sodium hydroxide solution, and separated to obtain an organic layer;

[0042] The organic layer is sequentially washed with water, distilled and filtered for a second time to obtain an OIT finished product.

[0043] In the present invention, the temperature of the chlorination reaction is preferably 40-60° C., more preferably 45-55° C. In the present invention, the speed of introducing chlorine gas is preferably 100-140 kg per hour, more preferably 120 kg per hour.

[0044] In the present invention, the preparation of the DCOIT finished product preferably comprises the following steps:

[0045] Mixing N,N'-dioctyl dithiodipropionamide and a chlorinated solvent, heating, introducing chlorine gas and chlorination reaction in sequence, stopping the reaction when the content of N,N'-dioctyl dithiodipropionamide is 0.01wt% to 0.05wt% by sampling liquid phase detection, cooling, first filtering and eluting in sequence to obtain a filter cake and a mother liquor;

[0046] The filter cake is suspended in chlorobenzene, neutralized with 20% sodium hydroxide solution, and separated to obtain an organic layer;

[0047] The organic layer is azeotropically dehydrated to a water content of less than 0.2%, and then combined with the mother liquor, and the temperature is raised, chlorine is introduced, and a re-chlorination reaction is performed in sequence. When the content of N, N'-di-n-octyl dithiodipropionamide in the sampled liquid phase is controlled to be 0.01wt% to 0.05wt%, the re-chlorination reaction is stopped, and desolventizing, methanol recrystallization, filtering, eluting and drying are performed in sequence to obtain a DCOIT finished product.

[0048] In the present invention, the temperature of the re-chlorination reaction is preferably 55-65° C., and the speed of introducing chlorine gas is 50-80 kg per hour, more preferably 60 kg per hour.

[0049] In the present invention, the stabilizer is preferably selected from one or more of 2,6-di-tert-butyl-p-cresol BHT, bis-2,2,6,6-tetramethylpiperidinol sebacate LS-770, dilauryl thiodipropionate DLTP, bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite THP-24, and the like.

[0050] In the present invention, the concentration of the stabilizer in the storage-stable water-insoluble isothiazolinone is preferably 10 to 500 ppm, more preferably 50 to 100 ppm. The present invention controls the content of N,N'-di-n-octyl dithiodipropionamide in the finished OIT or DCOIT product within the above range to avoid the decomposition of the raw materials to generate free radicals and reduce the degree of discoloration during the storage of the product.

[0051] The technical solutions in the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0052] Example 1

[0053] A method for preparing a storage-resistant water-insoluble isothiazolinone OIT, comprising the following steps:

[0054] (1) 2000 kg of chlorobenzene and 1400 kg of N,N'-dioctyl dithiodipropionamide were added to a 5000 L chlorination reactor, and chlorine was introduced after heating to 50° C. to carry out chlorination reaction. The temperature of the chlorination reaction liquid was maintained at 50-55° C. The chlorine introduction rate was 120 kg per hour, and the total amount of chlorine introduced was 650 kg. Samples were taken from the reactor, and the reaction was stopped when the liquid phase detected the content of N,N'-dioctyl dithiodipropionamide to be 0.05 wt%. The reaction liquid was cooled to room temperature, filtered, and washed with chlorobenzene to obtain filter cake OIT hydrochloride and mother liquor;

[0055] The filter cake was placed in a neutralization kettle, suspended in 1000 kg of chlorobenzene and neutralized with 20% sodium hydroxide solution, and separated to obtain 2400 kg of an organic layer. 1600 kg of the organic layer was washed, distilled, and filtered to obtain 750 kg of an OIT finished product with a liquid phase purity greater than 99%. The liquid phase detection showed that the content of N,N'-di-n-octyl dithiodipropionamide was 10 ppm;

[0056] (2) Add 0.05 g of light stabilizer 770 and 0.05 g of BHT to 1000 g of the OIT product obtained in step (1), respectively, and stir to dissolve, to obtain a storage-stable water-insoluble isothiazolinone OIT product containing 50 ppm of light stabilizer 770 and 50 ppm of BHT.

[0057] Example 2

[0058] The OIT finished product was prepared according to the method of Example 1, and then 0.05 g of dilauryl thiodipropionate and 0.10 g of antioxidant THP-24 were added to 1000 g of the OIT finished product, respectively, and stirred to dissolve, to obtain a storage-stable water-insoluble isothiazolinone OIT product containing 50 ppm of dilauryl thiodipropionate (DLTP) and 100 ppm of THP-24.

[0059] Example 3

[0060] A method for synthesizing a storage-stable water-insoluble isothiazolinone DCOIT, comprising the following steps:

[0061] (1) According to the method of Example 1, 2400 kg of organic layer was prepared, 800 kg of organic layer was taken, and after azeotropic dehydration to a water content of less than 0.2%, it was combined with the mother liquor distillation kettle residue obtained during chlorination, heated to 55° C. and then introduced chlorine gas for re-chlorination reaction. The chlorine gas introduction rate was 80 kg per hour, and the total amount of chlorine introduced was 380 kg. The sampling control test was performed. When the content of N, N'-di-n-octyl dithiodipropionamide in the liquid phase was less than 0.01 wt%, the reaction was stopped, the solvent was removed, the solvent was recovered, methanol was added to the kettle for recrystallization, and 500 kg of DCOIT finished product was obtained after filtering, eluting and drying. The liquid phase purity was greater than 99%, and the content of N, N'-di-n-octyl dithiodipropionamide was 5 ppm after liquid phase detection;

[0062] (2) Add 0.01 g of light stabilizer 770 and 0.10 g of antioxidant THP-24 to 1000 g of DCOIT obtained in step (1), respectively, and stir to dissolve to obtain a storage-stable water-insoluble isothiazolinone DCOIT product containing 100 ppm of light stabilizer 770 and 100 ppm of THP-24.

[0063] Example 4

[0064] A DCOIT product was prepared according to the method of Example 3, and then 0.50 g of antioxidant THP-24 was added to 1000 g of the DCOIT product and stirred to dissolve, thereby obtaining a storage-stable water-insoluble isothiazolinone DCOIT product containing 500 ppm of THP-24.

[0065] Comparative Example 1

[0066] The OIT finished product was prepared according to step (1) of Example 1.

[0067] Comparative Example 2

[0068] The DCOIT finished product was prepared according to step (1) of Example 2.

[0069] Comparative Example 3

[0070] The preparation steps of OIT finished product are as follows:

[0071] The OIT finished product was prepared according to the method of Example 1, except that the reaction was stopped when the content of the raw material N,N'-di-n-octyl dithiodipropionamide dropped to 1.5wt% during the chlorination reaction, and 750-80kg of OIT finished product was obtained, and the liquid phase purity was greater than 99%. The content of N,N'-di-n-octyl dithiodipropionamide was 720ppm after liquid phase detection.

[0072] Comparative Example 4

[0073] The preparation steps of DCOIT finished product are as follows:

[0074] According to the method of Example 3, part of the OIT prepared in Comparative Example 1 and the mother liquor still residue were subjected to re-chlorination reaction to obtain 500 kg of DCOIT finished product with a liquid phase purity of more than 99%. The content of N,N'-di-n-octyl dithiodipropionamide was 130 ppm after liquid phase detection.

[0075] Figure 1 This is the liquid phase spectrum of the OIT finished product prepared in Comparative Example 1 of the present invention.

[0076] Figure 2 This is the liquid phase spectrum of the DCOIT finished product prepared in Comparative Example 2 of the present invention.

[0077] Figure 3 This is the liquid phase spectrum of the OIT product prepared in Comparative Example 3 of the present invention.

[0078] Figure 4 This is the liquid phase spectrum of the DCOIT product prepared in Comparative Example 4 of the present invention.

[0079] The corresponding products obtained in Examples 1 to 4 and Comparative Examples 1 and 2 were placed in an oven (55° C.) for thermal stabilization for a certain period of time, and the color (Gardner) changes and active matter content of the products were investigated. The data are summarized in Table 1 below.

[0080] Figure 5 The physical pictures of the storage-stable water-insoluble isothiazolinone OIT products prepared in Examples 1 and 2 and the OIT finished products prepared in Comparative Examples 1 and 3 after heat stabilization, wherein: Figure 5 a, b and c are thermally stable for 0, 14 and 28 days respectively. Figure 5From left to right in a / b / c are Example 1, Example 2, Comparative Example 1 and Comparative Example 3 respectively.

[0081] Figure 6 The physical pictures of the storage-stable water-insoluble isothiazolinone DCOIT products prepared in Examples 3 and 4 and the OIT finished products prepared in Comparative Examples 2 and 4 after heat stabilization, wherein: Figure 6 a, b and c are thermally stable for 0, 14 and 28 days respectively. Figure 6 From left to right in a / b / c are Example 3, Example 4, Comparative Example 2 and Comparative Example 4 respectively.

[0082] Table 1 Product chromaticity change and active matter content statistics of corresponding products obtained in Examples 1 to 4 and Comparative Examples 1 to 4

[0083]

[0084] From Table 1 and Figure 5 , 6 It can be seen that the chromaticity of the water-insoluble isothiazolinone OIT product and the water-insoluble isothiazolinone DCOIT product prepared by the method provided by the present invention is stable, the content of active substances is high, and the problem of discoloration of water-insoluble isothiazolinone during storage is solved. The inventors found in the long-term experimental process that the storage discoloration phenomenon of water-insoluble isothiazolinone is related to the control of the chlorination process. Therefore, the inventors believe that the discoloration phenomenon may be related to internal and external factors. One is that the degree of chlorination reaction affects the remaining amount of raw materials, and the raw material N, N'-di-n-octyl dithiodipropionamide can be considered as a free radical reaction initiator. The sulfur-sulfur bond in the molecule breaks to generate free radicals, which further causes free radical discoloration reaction. This is the internal cause of the discoloration phenomenon; the second is to add free radical inhibitors to avoid the formation of free radicals to weaken the effect of the discoloration phenomenon, which is the external cause of the discoloration phenomenon. Therefore, the method provided by the present invention controls the residual amount of the raw material N,N'-di-n-octyl dithiodipropionamide on the one hand, and adds a stabilizer as a free radical inhibitor on the other hand, while controlling internal and external factors, and finally obtains a storage-resistant water-insoluble isothiazolinone OIT product and a storage-resistant water-insoluble isothiazolinone DCOIT product.

[0085] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a storage-resistant water-insoluble isothiazolinone, characterized in that: The following steps are involved: (1) using N,N'-dioctyldithiodipropionamide, a chlorinated solvent and chlorine as raw materials to carry out a chlorination reaction to prepare 2-n-octylisothiazoline-3-one OIT and / or 4,5-dichloro-2-n-octylisothiazoline-3-one DCOIT finished products; (2) The OIT / DCOIT product obtained in step (1) is mixed with a stabilizer to obtain a storage-resistant water-insoluble isothiazolinone.

2. The preparation method according to claim 1, characterized in that: In the step (1), the chlorination reaction is stopped when the content of N,N'-di-n-octyl dithiodipropionamide in the system is 0.01wt% to 0.05wt%.

3. The preparation method according to claim 1, characterized in that: The content of N,N'-di-n-octyl dithiodipropionamide in the finished OIT or DCOIT product in step (1) is less than 60 ppm.

4. The preparation method according to claim 1, characterized in that: The preparation of the OIT finished product in step (1) comprises the following steps: Mixing N,N'-dioctyl dithiodipropionamide and a chlorinated solvent, heating, introducing chlorine gas and chlorination reaction in sequence, stopping the reaction when the content of N,N'-dioctyl dithiodipropionamide is 0.01wt% to 0.05wt% by sampling liquid phase detection, cooling, first filtering and eluting in sequence to obtain a filter cake and a mother liquor; The filter cake is suspended in chlorobenzene, neutralized with 20% sodium hydroxide solution, and separated to obtain an organic layer; The organic layer is sequentially washed with water, distilled and filtered for a second time to obtain an OIT finished product.

5. The preparation method according to claim 4, characterized in that: The temperature of the chlorination reaction is 45-55° C., and the speed of introducing chlorine gas is 100-140 kg per hour.

6. The preparation method according to claim 1, characterized in that: The preparation of the DCOIT finished product in step (1) comprises the following steps: Mixing N,N'-dioctyl dithiodipropionamide and a chlorinated solvent, heating, introducing chlorine gas and chlorination reaction in sequence, stopping the reaction when the content of N,N'-dioctyl dithiodipropionamide is 0.01wt% to 0.05wt% by sampling liquid phase detection, cooling, first filtering and eluting in sequence to obtain a filter cake and a mother liquor; The filter cake is suspended in chlorobenzene, neutralized with 20% sodium hydroxide solution, and separated to obtain an organic layer; The organic layer is azeotropically dehydrated to a water content of less than 0.2%, and then combined with the mother liquor, and the temperature is raised, chlorine is introduced, and a re-chlorination reaction is performed in sequence. When the content of N, N'-di-n-octyl dithiodipropionamide in the sampled liquid phase is controlled to be 0.01wt% to 0.05wt%, the re-chlorination reaction is stopped, and desolventizing, methanol recrystallization, filtering, eluting and drying are performed in sequence to obtain a DCOIT finished product.

7. The preparation method according to claim 6, characterized in that: The temperature of the re-chlorination reaction is 55-65° C., and the speed of introducing chlorine gas is 50-80 kg per hour.

8. The preparation method according to claim 1, characterized in that: In the step (2), the stabilizer is selected from one or more of 2,6-di-tert-butyl-p-cresol BHT, bis-2,2,6,6-tetramethylpiperidinol sebacate LS-770, dilauryl thiodipropionate DLTP, bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite THP-24, and the like.

9. The preparation method according to claim 1, characterized in that: The concentration of the stabilizer in the storage-resistant water-insoluble isothiazolinone in the step (2) is 10 to 500 ppm.

10. The preparation method according to claim 1 or 9, characterized in that: The concentration of the stabilizer in the storage-resistant water-insoluble isothiazolinone in the step (2) is 50 to 100 ppm.

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