A method for treating distillation reactor residue containing 1,5-naphthalene diisocyanate

Abstract

The invention discloses a method for treating a rectification kettle residue containing 1,5-naphthalene diisocyanate. The method comprises the following steps: adding a certain amount of solvent to the rectification kettle residue to dissolve the solvent, and then subjecting the rectification kettle residue material to centrifugal drying treatment to obtain a centrifugal mother liquor. A 1,5-naphthalene diisocyanate synthetic liquid is added to the centrifugal mother liquor for mixing. When the isocyanate residue loses fluidity during a rectification recovery process, the 1,5-naphthalene diisocyanate can be effectively recovered from the solid isocyanate residue, the 1,5-naphthalene diisocyanate can be effectively separated from a high-boiling-point polymer solid residue, and compounds with a higher boiling point than the 1,5-naphthalene diisocyanate are further polymerized to form a high polymer solid residue. The high polymer solid residue is removed by a separation process to reduce the solubility of the high polymer solid residue in the solvent, while the 1,5-naphthalene diisocyanate can be effectively dissolved in the solvent, thereby increasing the content and yield of the recovered 1,5-naphthalene diisocyanate product. The treatment process of the rectification kettle residue of the 1,5-naphthalene diisocyanate does not require a high-temperature condition, effectively reduces the energy consumption of the recovery process, and is convenient for industrial implementation.

Description

Technical Field

[0001] The invention relates to the technical field of chemical raw material processing, and in particular to a method for treating distillation kettle residue containing 1,5-naphthalene diisocyanate. Background Art

[0002] NDI (1,5-naphthalene diisocyanate) is a raw material for high-performance polyurethane and can be used to manufacture high-elasticity and high-hardness polyurethane elastomers. It has the advantages of excellent dynamic performance, wear resistance, low damping and high resilience. It can be widely used in automotive shock absorbers, printing and dyeing textile rubber rollers, bridge construction buffer blocks, entertainment and leisure, and military industry.

[0003] At present, NDI is mainly synthesized by phosgene method using 1,5-naphthalenediamine and phosgene. In the process of NDI synthesis, main and side reactions will occur simultaneously. The side reaction products mainly include urea and imine substances with relatively active chemical properties. These substances can continue to polymerize with the generated NDI or themselves to generate high molecular weight polymer solid residues. In the subsequent separation process, the high temperature of the separation kettle will also lead to an increase in solid residues. In the prior art, distillation process is usually used to separate and purify NDI. In the distillation process, pure NDI will leave the system from the top of the distillation tower. , while the remaining by-products and NDI that has not been distilled out remain at the bottom of the distillation kettle. As the proportion of NDI in the kettle gradually decreases, the proportion of infusible solid residue also increases, and the fluidity of the tower kettle is also weakened accordingly. If the above-mentioned materials in the kettle are discharged before the fluidity disappears, it will cause a high loss of NDI product yield; if the distillation continues, the residue in the kettle loses fluidity and cannot be discharged from the system, resulting in equipment shutdown and safety hazards. In addition, the prior art mostly uses distillation to treat isocyanate residues. Long-term high-temperature distillation will cause side reactions in the isocyanate product, reducing the increase in the isocyanate yield.

[0004] Patent CN105452216B discloses a method for obtaining organic isocyanate from distillation residue of preparing isocyanate. The invention adopts a two-stage series distillation method to recover isocyanate in the still residue. By controlling the vacuum and temperature of the two-stage distillation, the purpose of improving the isocyanate recovery rate is achieved. However, it is only suitable for processing still residue materials that are fluid and thermally stable, and it is difficult to process non-fluid NDI still residue.

[0005] Patent CN105384644A discloses a method for treating isocyanate residues, wherein the isocyanate residues are reacted with a strong alkaline substance, an organic solvent is used as a reaction reagent, and the residues are reduced to organic amines under the conditions of a phase transfer catalyst and a certain reaction temperature, thereby improving the recovery rate of the treated product organic amines. However, this method is only applicable to treating isocyanate residues when the isocyanate content in the isocyanate residues is low. When the isocyanate content in the isocyanate residues is high, the isocyanate will be reduced to a raw material, which reduces the product production efficiency, the isocyanate recovery yield is low, and the energy consumption and production cost are increased. Summary of the invention

[0006] In order to solve the problems in the prior art that the recovery rate of isocyanate residue is low, side reactions are prone to occur during the recovery process, when the isocyanate residue loses fluidity during the distillation recovery process, it is difficult to effectively recover 1,5-naphthalene diisocyanate from the solid isocyanate residue, and when the isocyanate content in the isocyanate residue is high, the isocyanate will be reduced to raw materials, the product production efficiency is low, the isocyanate recovery yield is low, the recovery energy consumption and production cost are high, and it is difficult to recover high-content and high-purity 1,5-naphthalene diisocyanate.

[0007] The invention discloses a method for treating distillation reactor residue containing 1,5-naphthalene diisocyanate, comprising the following steps:

[0008] Step 1: adding a solvent to the distillation reactor residue containing 1,5-naphthalene diisocyanate, heating and stirring, and then cooling to obtain a mixed material;

[0009] Step 2: centrifugally drying the mixed material until the moisture content of the solid residue reaches a preset value, separating the centrifugal mother liquor from the solid residue to obtain the centrifugal mother liquor;

[0010] Step 3: adding 1,5-naphthalene diisocyanate synthesis liquid to the centrifuged mother liquor to mix to obtain a mixed liquid, and subjecting the mixed liquid to desolventization and distillation to obtain a 1,5-naphthalene diisocyanate finished product;

[0011] In some embodiments of the present invention, the specific steps of step 1 include:

[0012] Adding a solvent to the residue containing 1,5-naphthalene diisocyanate, heating to 30-100°C and stirring at a stirring speed of 200-400 r / min for 0.5-5h, and then cooling to 15-30°C to obtain a mixed material;

[0013] In some embodiments of the present invention, the centrifugal speed of the centrifugal drying treatment of the mixed material in step 2 is 3500-5000 r / min;

[0014] In some embodiments of the present invention, the centrifugal drying in step 2 is performed until the moisture content of the solid residue is a preset value, and the preset value is that the dry weight of the solid residue is less than or equal to 15% of the sum of the dry weight of the solid residue and the weight of the centrifuged mother liquor;

[0015] In some embodiments of the present invention, the solvent in step 1 includes one or more of toluene, benzene, o-dichlorobenzene, chlorobenzene, and ethylene dichloride;

[0016] In some embodiments of the present invention, the mass of the solvent in step 1 is 3-10 times the mass of 1,5-naphthalene diisocyanate;

[0017] In some embodiments of the present invention, in the distillation reactor residue containing 1,5-naphthalene diisocyanate in step 1, the mass percentage of 1,5-naphthalene diisocyanate is ≤50%, the mass percentage of high-boiling point polymer solid residue with a molecular weight between 5000 and 20000 is 42-48%, and the mass percentage of compounds with a higher boiling point than 1,5-naphthalene diisocyanate is 5-8%;

[0018] The compound with a higher boiling point than 1,5-naphthalene diisocyanate includes urea, dimer, and naphthalene diamine, and the mass ratio of urea, dimer, and naphthalene diamine is 2-4:3-5:1-5;

[0019] In some embodiments of the present invention, the specific steps of the desolventizing treatment in step 3 include:

[0020] The mixed liquid is desolventized by a constant speed agitator, the stirring speed of the constant speed agitator is 200-400r / min, the terminal temperature of the mixed liquid material in the constant speed agitator is ≤140°C, the desolventizing pressure is ≤60mmHg, the desolventizing time is ≤24h, and the desolventizing gas phase condensation temperature is ≤30°C;

[0021] In some embodiments of the present invention, the specific steps of the distillation treatment in step 3 include:

[0022] The mixed liquid after the desolventizing treatment is passed into a distillation tower for distillation treatment, the terminal temperature of the mixed liquid material in the distillation tower is less than 180°C, the absolute pressure in the distillation tower is less than 5mmHg, and the gas phase condensation temperature of the distillation treatment is 130-140°C;

[0023] In some embodiments of the present invention, the mass ratio of the centrifuged mother liquor to the 1,5-naphthalene diisocyanate synthesis liquid in step 3 is 0.04-0.15:1;

[0024] A 1,5-naphthalene diisocyanate finished product is prepared by the method for treating the distillation reactor residue containing 1,5-naphthalene diisocyanate described in steps one to three.

[0025] The beneficial effects of adopting the above technical solution are as follows:

[0026] By adding a certain amount of solvent to the distillation still residue to dissolve, when the mass percentage of 1,5-naphthalene diisocyanate in the distillation still residue is ≤50%, the fluidity of the distillation still residue is poor. The present application only needs to add solvent and control the mass ratio of the centrifuged mother liquor and the 1,5-naphthalene diisocyanate synthetic liquid. Through specific desolventizing and distillation treatment processes, the 1,5-naphthalene diisocyanate in the distillation still residue containing 1,5-naphthalene diisocyanate can be effectively separated from the high-boiling-point polymer solid residue with a molecular weight of 5000-20000, and the compounds with a higher boiling point than 1,5-naphthalene diisocyanate can be further polymerized to form The polymer solid residue is removed through a centrifugal drying process, which reduces the solubility of compounds with higher boiling points than 1,5-naphthalene diisocyanate in the solvent, while 1,5-naphthalene diisocyanate can be effectively dissolved in the solvent, thereby further improving the content and yield of the recovered product. The HPLC normalized content of the 1,5-naphthalene diisocyanate product can reach up to 99.75%, and the yield can reach up to 94.8%. The treatment process of the distillation kettle residue of 1,5-naphthalene diisocyanate does not require high temperature conditions, and the number of chemical equipment used is small. The processes used are all conventional processes, which effectively reduce the energy consumption of the recovery process and facilitate industrial implementation. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The present invention is a flow chart of a method for treating distillation reactor residue containing 1,5-naphthalene diisocyanate according to an embodiment of the present application. DETAILED DESCRIPTION

[0028] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below in conjunction with specific implementation methods.

[0029] like Figure 1 As shown, the present application provides a method for treating distillation reactor residue containing 1,5-naphthalene diisocyanate as follows:

[0030] S1: adding a solvent to a mixture containing 1,5-naphthalene diisocyanate, heating and stirring, and then cooling to obtain a mixed material;

[0031] S2: centrifugally drying the mixed material until the moisture content of the solid residue reaches a preset value, separating the centrifugal mother liquor from the solid residue to obtain the centrifugal mother liquor;

[0032] S3: adding 1,5-naphthalene diisocyanate synthesis liquid to the centrifuged mother liquor to mix to obtain a mixed liquid, and subjecting the mixed liquid to desolventizing treatment and distillation treatment to obtain a 1,5-naphthalene diisocyanate finished product.

[0033] In the present application, in the distillation reactor residue containing 1,5-naphthalene diisocyanate, the mass percentage of 1,5-naphthalene diisocyanate is ≤50%, the mass percentage of high-boiling polymer solid residue with a molecular weight between 5000 and 20000 is 42-48%, and the mass percentage of compounds with a higher boiling point than 1,5-naphthalene diisocyanate is 5-8%;

[0034] The compound with a higher boiling point than 1,5-naphthalene diisocyanate includes urea, dimer and naphthalene diamine, and the mass ratio of urea, dimer and naphthalene diamine is 2-4:3-5:1-5.

[0035] When the mass percentage of 1,5-naphthalene diisocyanate in the distillation kettle residue is ≤50%, the fluidity of the distillation kettle residue is poor, and it is difficult to separate the 1,5-naphthalene diisocyanate and high-boiling-point polymer solid residue in the distillation kettle residue from compounds with higher boiling points than 1,5-naphthalene diisocyanate. The present application adds a solvent and controls the mass ratio of the centrifuged mother liquor and the 1,5-naphthalene diisocyanate synthetic liquid (wherein the 1,5-naphthalene diisocyanate synthetic liquid is prepared by adopting the existing general method for synthesizing 1,5-naphthalene diisocyanate) through a specific The desolventizing and distillation treatment processes can effectively separate 1,5-naphthalene diisocyanate from high-boiling-point polymer solid residues with a molecular weight of 5000-20000 in the distillation kettle residue containing 1,5-naphthalene diisocyanate, promote further polymerization of compounds with higher boiling points than 1,5-naphthalene diisocyanate to form polymer solid residues, which are removed through a centrifugal drying process, thereby increasing the content and yield of the 1,5-naphthalene diisocyanate product. The HPLC normalized content of the 1,5-naphthalene diisocyanate product can reach up to 99.75%, and the yield can reach up to 94.8%.

[0036] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below in conjunction with specific embodiments.

[0037] Embodiment 1

[0038] Step 1: Using liquid chromatography to analyze the residual components of the distillation kettle of 1,5-naphthalene diisocyanate, the mass proportions of 1,5-naphthalene diisocyanate, compounds with higher boiling points than 1,5-naphthalene diisocyanate (compounds with higher boiling points than 1,5-naphthalene diisocyanate include urea, dimer, and naphthalene diamine, and the mass ratio of urea, dimer, and naphthalene diamine is 2:3:2), and high-boiling polymer solid residues with a molecular weight of 5000-20000 are 48.2%, 6.6%, and 45.2%, respectively. 635.6g of o-dichlorobenzene is added to 158.9g of the distillation kettle residue containing 1,5-naphthalene diisocyanate, the temperature is raised to 80°C, stirred for 1h, the stirring speed is 260r / min, and then cooled to 25°C to obtain a mixed material;

[0039] Step 2: centrifugally drying the mixed material at a centrifugal speed of 3800 r / min until the mass of the centrifugal mother liquor is 695.4 g and the mass of the solid residue is 93.5 g, separating the centrifugal mother liquor from the solid residue to obtain a centrifugal mother liquor;

[0040] Step 3: Add 1,5-naphthalene diisocyanate synthesis liquid to the centrifugal mother liquor and mix (the mass ratio of the centrifugal mother liquor to the 1,5-naphthalene diisocyanate synthesis liquid is 0.06:1, wherein the 1,5-naphthalene diisocyanate synthesis liquid is prepared by adopting the existing general method for synthesizing 1,5-naphthalene diisocyanate) to obtain a mixed liquid, and use a constant speed agitator to perform desolventizing treatment on the mixed liquid, the stirring speed of the constant speed agitator is 260r / min, the terminal temperature of the mixed liquid material in the constant speed agitator is controlled to be 140°C, the desolventizing treatment pressure is 60mmHg, the desolventizing treatment time is 22h, and the desolventizing treatment gas phase condensation temperature is 30°C;

[0041] The mixed liquid after the desolventizing treatment was passed into a distillation tower for distillation, the terminal temperature of the mixed liquid material in the distillation tower was controlled to be 170°C, the absolute pressure in the distillation tower was 4.5 mmHg, the gas phase condensation temperature of the distillation treatment was 130°C, and 301.2 g of 1,5-naphthalene diisocyanate product was prepared.

[0042] The HPLC normalized content was 99.75%, and the yield was 94.8% (calculated as 1,5-naphthalene diisocyanate product). Compared with the process of not recovering 1,5-naphthalene diisocyanate in the kettle residue (i.e., synthesizing 1,5-naphthalene diisocyanate by the prior art, and then obtaining 1,5-naphthalene diisocyanate product by desolventizing and distilling, and not treating 1,5-naphthalene diisocyanate in any way, and directly treating it as hazardous waste), the distillation of 1,5-naphthalene diisocyanate in this embodiment was used. The method for treating the still residue is to treat the distillation still residue of 1,5-naphthalene diisocyanate, and the content and yield of the 1,5-naphthalene diisocyanate product are increased by about 24 percentage points. The distillation still residue of 1,5-naphthalene diisocyanate obtained by the desolventizing treatment and distillation treatment in step three is 159.2 g. The distillation still residue of 1,5-naphthalene diisocyanate obtained can be repeatedly treated according to the processes of steps one to three to recover the 1,5-naphthalene diisocyanate in the distillation still residue.

[0043] Embodiment 2

[0044] Step 1: Using liquid chromatography to analyze the residual components of the distillation kettle of 1,5-naphthalene diisocyanate, the components are: 1,5-naphthalene diisocyanate, compounds with higher boiling points than 1,5-naphthalene diisocyanate (compounds with higher boiling points than 1,5-naphthalene diisocyanate include urea, dimer, and naphthalene diamine, and the mass ratio of urea, dimer, and naphthalene diamine is 4:5:4.5), and the mass proportions of high-boiling polymer solid residues with a molecular weight of 5000-20000 are 45.2%, 7.3%, and 47.5%, respectively. 729g of chlorobenzene is added to 145.8g of the distillation kettle residue containing 1,5-naphthalene diisocyanate, the temperature is raised to 90°C, stirred for 0.5h, the stirring speed is 400r / min, and then cooled to 20°C to obtain a mixed material;

[0045] Step 2: centrifugally drying the mixed material at a centrifugal speed of 5000 r / min until the mass of the centrifugal mother liquor is 778.6 g and the mass of the solid residue is 92 g, separating the centrifugal mother liquor from the solid residue to obtain a centrifugal mother liquor;

[0046] Step 3: Add 1,5-naphthalene diisocyanate synthesis liquid to the centrifugal mother liquor and mix (the mass ratio of the centrifugal mother liquor to the 1,5-naphthalene diisocyanate synthesis liquid is 0.15:1, wherein the 1,5-naphthalene diisocyanate synthesis liquid is prepared by adopting the existing general method for synthesizing 1,5-naphthalene diisocyanate) to obtain a mixed liquid, and use a constant speed agitator to perform desolventizing treatment on the mixed liquid, the stirring speed of the constant speed agitator is 380r / min, the terminal temperature of the mixed liquid material in the constant speed agitator is controlled to be 130°C, the desolventizing treatment pressure is 55mmHg, the desolventizing treatment time is 20h, and the desolventizing treatment gas phase condensation temperature is 26°C;

[0047] The mixed liquid after the desolventizing treatment was passed into a distillation tower for distillation, the terminal temperature of the mixed liquid material in the distillation tower was controlled to be 160°C, the absolute pressure in the distillation tower was 3.5 mmHg, the gas phase condensation temperature of the distillation treatment was 140°C, and 278.4 g of 1,5-naphthalene diisocyanate product was prepared.

[0048] The HPLC normalized content was 99.68%, and the yield was 93.9% (calculated as 1,5-naphthalene diisocyanate product). Compared with the process of not recovering 1,5-naphthalene diisocyanate in the still residue (i.e., synthesizing 1,5-naphthalene diisocyanate by the prior art, and then obtaining 1,5-naphthalene diisocyanate product by desolventizing and distilling, and directly treating 1,5-naphthalene diisocyanate as hazardous waste without any treatment), the distillation still residue of 1,5-naphthalene diisocyanate was treated by the treatment method of the distillation still residue containing 1,5-naphthalene diisocyanate in the present embodiment, and the content and yield of the 1,5-naphthalene diisocyanate product were increased by about 23 percentage points. The distillation still residue obtained by the desolventizing process and the distillation process in step three was 147.2 g, and the distillation still residue of 1,5-naphthalene diisocyanate obtained by the process of steps one to three was repeatedly treated to recover 1,5-naphthalene diisocyanate in the distillation still residue.

[0049] The present application is described in detail above in conjunction with specific implementation methods and exemplary examples, but these descriptions cannot be understood as limiting the present application. Those skilled in the art understand that, without departing from the spirit and scope of the present application, a variety of equivalent replacements, modifications or improvements can be made to the technical solution of the present application and its implementation methods, all of which fall within the scope of the present application. The scope of protection of the present application shall be subject to the attached claims.

Claims

1. A method for treating distillation reactor residue containing 1,5-naphthalene diisocyanate, characterized in that: The following steps are involved: Step 1: adding a solvent to the distillation reactor residue containing 1,5-naphthalene diisocyanate, heating to 30-100° C. and stirring at a stirring speed of 200-400 r / min for 0.5-5 h, and then cooling to 15-30° C. to obtain a mixed material; the solvent comprises one or more of toluene, benzene, o-dichlorobenzene, chlorobenzene, and ethylene dichloride; Step 2: centrifugally drying the mixed material until the moisture content of the solid residue reaches a preset value, separating the centrifugal mother liquor from the solid residue to obtain the centrifugal mother liquor, wherein the preset value is that the dry weight of the solid residue is less than or equal to 15% of the total weight of the dry weight of the solid residue and the centrifugal mother liquor; Step 3: Add 1,5-naphthalene diisocyanate synthesis liquid to the centrifuged mother liquor to mix to obtain a mixed liquor, and prepare the 1,5-naphthalene diisocyanate finished product by desolventizing and distilling the mixed liquor, wherein the mass ratio of the centrifuged mother liquor to the 1,5-naphthalene diisocyanate synthesis liquid is 0.04-0.15:1, and the specific steps of the desolventizing treatment include: using a constant speed agitator to desolventize the mixed liquor, the stirring speed of the constant speed agitator is 200-400r / min, the terminal temperature of the mixed liquor material in the constant speed agitator is ≤140°C, the desolventizing treatment pressure is ≤60mmHg, the desolventizing treatment time is ≤24h, and the desolventizing treatment gas phase condensation temperature is ≤30°C; the specific steps of the distillation treatment include: passing the mixed liquor after the desolventizing treatment into a distillation tower for distillation treatment, the terminal temperature of the mixed liquor material in the distillation tower is <180°C, the absolute pressure in the distillation tower is <5mmHg, and the distillation treatment gas phase condensation temperature is 130-140°C.

2. The method for treating the distillation reactor residue containing 1,5-naphthalene diisocyanate according to claim 1, characterized in that: The mass of the solvent in step 1 is 3-10 times the mass of 1,5-naphthalene diisocyanate.

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