System device and method for preparing PDI from pentamethylene diamine salt

Abstract

The invention provides a system device and a method for preparing PDI from pentamethylene diamine salt, the device and the method utilize a three-section (carbon dioxide removal and discharge in an A section, acyl chloride formation, hydrogen chloride discharge and partial phosgene discharge in a B section, and PDI preparation from an intermediate state in a C section) channelization reaction, PDI is directly prepared from PDA carbon dioxide salt (PCC), and the product has low hydrolytic chlorine; under the condition that the total length of the pipeline is fixed, the cost of the three-section reaction pipeline reactor is far lower than that of a one-section reaction pipeline reactor, the manufacturing cost of the device is effectively reduced, and the whole process is efficient, energy-saving and safe.

Description

Technical Field

[0001] This invention belongs to the field of chemical production and relates to a system and method for preparing PDI from pentanediamine salt. Background Technology

[0002] Diisocyanates are highly reactive and can polymerize with hydroxyl and amino-containing substances to form polyurethane. Their applications span multiple fields, including construction (insulation foam, waterproof coatings, etc.), automotive (seat foam, body coatings), furniture and home appliances (adhesives, insulation layers), and footwear and textiles (shoe sole elastomers, waterproof coatings for fabrics). Among them, pentamethylene diisocyanate (also known as pentylene diisocyanate, PDI) is an emerging aliphatic representative product of diisocyanates, possessing enormous market potential.

[0003] PDI preparation methods are divided into gas-phase phosgenation reaction with PDA (pentanediamine) or liquid-phase phosgenation reaction. Gas-phase reaction has high efficiency, but it places extremely demanding requirements on the spraying equipment, and the reaction speed is fast, difficult to control, and prone to generating various impurities, making industrial-scale production difficult. Liquid-phase phosgenation reaction for PDI preparation typically involves a two-step phosgenation reaction of free diamine or its salt in a batch reactor, followed by distillation of the crude product to obtain the target product. The batch-type liquid-phase phosgenation reaction method suffers from numerous problems, including high solvent consumption, low efficiency, high impurity levels, severe coking, complex operation, and poor batch stability. One improvement method for the liquid-phase reaction is to utilize a pipelined reactor. Compared to batch reactors, pipelined reactions offer significant improvements in solvent consumption, energy consumption, and risk control, but they also have limitations, such as uneven mixing of raw materials, solvents, and phosgene leading to increased side reactions and impurities, and scaling and clogging of the pipeline walls.

[0004] Therefore, there is an urgent need for a liquid-phase production method for PDI that can directly utilize pentanediamine raw material salt for pipeline production, avoid the adverse effects of many impurities in the pipeline, and achieve low production costs and high product purity. Summary of the Invention

[0005] To address the technical problems existing in the prior art, this invention provides a system and method for preparing PDI using pentanediamine salt. It directly utilizes pentanediamine carbonate (PCC) as a raw material to prepare PDI. PCC products have the advantages of low price, high purity, and low water content, which can effectively reduce the production cost of PDI, and is efficient, energy-saving, and pressure-reducing.

[0006] To achieve the above-mentioned technical effects, the present invention adopts the following technical solution:

[0007] One objective of this invention is to provide a system apparatus for preparing PDI from pentanediamine salt, the system apparatus comprising a pipeline reactor A, a pipeline reactor B, and a pipeline reactor C connected in sequence;

[0008] The pipeline reactor A has a gas outlet at its tail end, which is connected to the gas inlet of the first gas-liquid separator. The liquid outlet of the first gas-liquid separator is connected to the material inlet of the pipeline reactor A. The gas outlet of the first gas-liquid separator is connected to a vacuum system. The material outlet of the pipeline reactor A is connected to the material inlet of the pipeline reactor B.

[0009] The head of the pipeline reactor B is provided with a phosgene inlet, and the tail of the pipeline reactor B is provided with a gas outlet. The gas outlet is connected to the gas inlet of the second gas-liquid separator, the liquid outlet of the second gas-liquid separator is connected to the material inlet of the pipeline reactor B, the gas outlet of the second gas-liquid separator is connected to the phosgene recovery device, and the material outlet of the pipeline reactor B is connected to the material inlet of the pipeline reactor C.

[0010] As a preferred technical solution of the present invention, a gas separation inlet is provided on the pipeline connecting the gas outlet of the pipeline reactor A and the first gas-liquid separator.

[0011] As a preferred technical solution of the present invention, a first liquid conveying device is provided on the connecting pipeline between the liquid outlet of the first gas-liquid separator and the pipeline reactor A.

[0012] Preferably, a second liquid conveying device is provided on the connecting pipeline between the liquid outlet of the second gas-liquid separator and the pipeline reactor B.

[0013] As a preferred technical solution of the present invention, the phosgene recovery device is connected to a vacuum system.

[0014] As a preferred technical solution of the present invention, the material outlet of the pipeline reactor C is connected to the product separation device, and the gas outlet of the product separation device is connected to the phosgene recovery device.

[0015] Preferably, the product separation device is a negative pressure distillation device.

[0016] The second objective of this invention is to provide a systematic method for preparing PDI from pentanediamine salt, which uses the system apparatus provided in the first objective, and the systematic method includes:

[0017] The reactants containing PCC and a catalyst enter the pipeline reactor A for PCC decomposition reaction to obtain PDA. The carbon dioxide produced by the reaction enters the first gas-liquid separator through the gas outlet, and the separated liquid phase (PDA and solvent carried out by carbon dioxide) is returned to the pipeline reactor A.

[0018] PDA enters pipeline reactor B and undergoes an acyl chloride reaction with phosgene to obtain a product intermediate. The hydrogen chloride and some phosgene obtained from the reaction enter the second gas-liquid separator. The separated gas enters the phosgene recovery device, and the separated liquid (the solvent carried out by the gas) is returned to pipeline reactor B.

[0019] The intermediate product enters the pipeline reactor C for reaction, the product material enters the product separation device to separate and obtain PDI, and the obtained gas enters the phosgene recovery device.

[0020] As a preferred technical solution of the present invention, the catalytic decomposition agent includes any one or a combination of at least two of quaternary ammonium bases, quaternary ammonium salts, Lewis acids, quaternary phosphonium salts, or sulfonium salts.

[0021] Preferably, the quaternary ammonium base includes C1-10 aliphatic or aromatic quaternary ammonium bases.

[0022] Preferably, the quaternary ammonium salt includes C1-10 aliphatic or aromatic quaternary ammonium salts.

[0023] Preferably, the Lewis acid includes any one or a combination of at least two of aluminum chloride, ferric chloride, or zinc chloride.

[0024] Preferably, the quaternary phosphonium salt includes C1-10 aliphatic or aromatic quaternary phosphonium salts.

[0025] Preferably, the matte salt includes C1-10 aliphatic or aromatic matte salts.

[0026] As a preferred technical solution of the present invention, the vacuum degree in pipeline reactor A, pipeline reactor B, and pipeline reactor C increases sequentially.

[0027] As a preferred technical solution of the present invention, the reaction temperature in the pipeline reactor A is 50~150℃, preferably 90~100℃; the vacuum degree is 4000~10000 Pa, preferably 5000~6000 Pa.

[0028] Preferably, the mass ratio of PCC to solvent in the reactants is 1~40:100, more preferably 25~30:100.

[0029] Preferably, the flow rate of the separating gas is 1 to 5 times the flow rate of carbon dioxide, and more preferably 2 times.

[0030] As a preferred technical solution of the present invention, the reaction temperature in the pipeline reactor B is 100~200℃, preferably 110~130℃; the vacuum degree is 3000~7000 Pa, preferably 4000~5000 Pa.

[0031] Preferably, the molar ratio of phosgene to PDA in pipeline reactor B is 2.2:1 to 15:1.

[0032] Preferably, the amount of phosgene discharged from the pipeline reactor B is 10-86% of the amount of raw material phosgene entering, and more preferably 60-80%.

[0033] As a preferred technical solution of the present invention, the reaction temperature in the pipeline reactor C is 150~300℃, preferably 200~250℃; the vacuum degree is 1000~5000 Pa, preferably 3000~4000 Pa.

[0034] Preferably, the total residence time of pipeline reactors A, B, and C is 10-100 s, and more preferably 20-30 s.

[0035] Preferably, the residence time ratio of pipeline reactor A, pipeline reactor B and pipeline reactor C is 3:(1~3):(1~3).

[0036] Compared with the prior art, the present invention has at least the following beneficial effects:

[0037] (1) This invention provides a system and method for the direct preparation of PDI from pentanediamine salt. It utilizes a three-stage pipeline reaction (stage A decomposes pentanediamine salt to obtain PDA, while simultaneously removing carbon dioxide; stage B reacts PDA with phosgene to form acyl chloride, removing hydrogen chloride and some phosgene; stage C prepares PDI from the intermediate state); PDI is prepared from PDA carbon dioxide salt (PCC); with a fixed total pipeline length, the cost of the three-stage reaction pipeline reactor is much lower than that of the one-stage reactor, effectively reducing the manufacturing cost of the device. The overall process is efficient, energy-saving, and safe with reduced pressure.

[0038] (2) The present invention provides a system device and method for preparing PDI from pentanediamine salt. The decomposition catalyst is used to pyrolyze PCC, which greatly improves the decomposition efficiency and greatly reduces the decomposition temperature, thus avoiding the problem of PDA polymerization and the generation of polymer impurities due to excessively high decomposition reaction temperature when no decomposition catalyst is used.

[0039] (3) The present invention provides a system device and method for preparing PDI from pentanediamine salt. The tail end of the pipeline reactor A adopts a vacuum negative pressure + gas-liquid separation + barrier gas as the whole system to efficiently remove carbon dioxide generated in the reaction system. At the same time, it recovers the entrained PDA with a high recovery rate and does not cause PDA and carbon dioxide to form salt again during the recovery process, thus avoiding the problem of PDA forming white solid or gel-like substance and clogging the pipeline due to PDA forming salt again.

[0040] (4) The present invention provides a system device and method for preparing PDI from pentanediamine salt, which timely discharges hydrogen chloride and part of phosgene generated during the reaction process of pipeline reactor B under negative pressure, thereby reducing the generation of by-products; at the same time, it can also improve production efficiency and avoid the use of phosgene compressors with high production risks.

[0041] (5) The present invention provides a system device and method for preparing PDI from pentanediamine salt. The temperature of the acyl chloride reaction in pipeline reactor B is much lower than the temperature of the acyl chloride reaction to generate PDI in pipeline reactor C. Therefore, the segmented reaction has the advantages of energy saving and tar reduction. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of the system apparatus for preparing PDI from pentanediamine salt provided in Embodiment M2 of the present invention.

[0043] The present invention will now be described in further detail. However, the examples described below are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims. Detailed Implementation

[0044] The technical solution of this application will be further described below through specific implementation methods.

[0045] The present invention specifically provides a system apparatus for the direct preparation of PDI from pentanediamine salt, the system apparatus comprising pipeline reactor A, pipeline reactor B and pipeline reactor C connected in sequence;

[0046] The pipeline reactor A has a gas outlet at its tail end, which is connected to the gas inlet of the first gas-liquid separator. The liquid outlet of the first gas-liquid separator is connected to the material inlet of the pipeline reactor A. The gas outlet of the first gas-liquid separator is connected to a vacuum system. The material outlet of the pipeline reactor A is connected to the material inlet of the pipeline reactor B.

[0047] The head of the pipeline reactor B is provided with a phosgene inlet, and the tail of the pipeline reactor B is provided with a gas outlet. The gas outlet is connected to the gas inlet of the second gas-liquid separator, the liquid outlet of the second gas-liquid separator is connected to the material inlet of the pipeline reactor B, the gas outlet of the second gas-liquid separator is connected to the phosgene recovery device, and the material outlet of the pipeline reactor B is connected to the material inlet of the pipeline reactor C.

[0048] In this invention, pipeline reactors A, B, and C, connected sequentially, divide the PDA preparation reaction using PCC as raw material into three stages. In pipeline reactor A, the PCC decomposition reaction occurs, and the generated CO2 enters the first gas-liquid separator, ensuring timely removal of the carbon dioxide from the reaction system. Simultaneously, the generated PDA also enters pipeline reactor B, thereby improving the efficiency of stage A. In pipeline reactor B, the PDA undergoes an acylation reaction. During this reaction, the generated hydrogen chloride and some unreacted phosgene are promptly removed, accelerating the stage B reaction, reducing byproduct formation, and significantly minimizing the formation of byproducts (polymers, hydrolyzed chlorine, and monochlorinated impurities) in the subsequent stage C. The inventors discovered that stage C does not require phosgene; only a small amount is needed to maintain the phosgene atmosphere. Excessive phosgene and hydrogen chloride can lead to increased byproducts. Timely removal of the generated hydrogen chloride and some unreacted phosgene also maintains a low-pressure state in the reaction system, resulting in higher production efficiency per unit volume and allowing phosgene to be introduced into the reaction tube at a lower pressure, avoiding the use of a dangerous phosgene compressor. In addition, the temperature of the acyl chlorination reaction of PDA in pipeline reactor B is much lower than that of the PDI preparation reaction in pipeline reactor C. Compared with a single reactor, the segmented phosgenation reaction can reduce energy consumption and further reduce the generation of by-products.

[0049] In one specific embodiment of the present invention, pipeline reactor A is preferably a dynamic mixing reactor, while pipeline reactors B and C are each preferably static mixing reactors. The reason for using a dynamic mixing reactor for pipeline reactor A is that section A is a mixture of solid (PCC), liquid (ODCB, i.e., o-dichlorobenzene), and gas (phosgene), and a dynamic mixer can make the reaction mixture more uniform and thorough. However, dynamic mixing reactors are relatively expensive. In this embodiment, by dividing the pipeline reaction into three sections, sections B and C only need to use static reactors, which can reduce the overall cost.

[0050] In one specific embodiment of the present invention, a dynamic mixing reactor is a reactor in which components such as a stirring paddle and a vibrating screen are installed inside the reactor to promote the mixing of the reaction system, while a static mixing reactor is a reactor in which statically distributed components such as a baffle plate and a baffle cover are installed inside the reactor.

[0051] In one specific embodiment of the present invention, the inner diameter, length, shell material and model of pipeline reactor A, pipeline reactor B and pipeline reactor C can be adjusted according to their actual internal reaction effect and production scale, and are not specifically limited here.

[0052] In one specific embodiment of the present invention, the inner diameters of pipeline reactor A, pipeline reactor B, and pipeline reactor C are set to decrease sequentially.

[0053] In one specific embodiment of the present invention, in order to ensure that the carbon dioxide generated in pipeline reactor A and the hydrogen chloride generated in pipeline reactor B can be removed from the reactor in a timely manner, the gas outlets at the tail ends of pipeline reactor A and pipeline reactor B are arranged in opposite directions perpendicular to the bottom surface.

[0054] In one specific embodiment of the present invention, in order to maintain the vacuum state inside the pipeline reactor A and to facilitate the removal of the carbon dioxide gas generated by the reaction, the first gas-liquid separator is connected to the vacuum system.

[0055] In one specific embodiment of the present invention, a gas separation inlet is provided on the pipeline connecting the gas outlet of the pipeline reactor A to the first gas-liquid separator.

[0056] In this invention, by setting a barrier gas in the carbon dioxide removal pipeline, it is possible to prevent some carbon dioxide from flowing back and reacting with the generated PDA to regenerate salt. This avoids the regenerated salt forming a white solid or gel that blocks the pipeline, reduces the generation of impurities, and improves the conversion rate of PCC decomposition.

[0057] In one specific embodiment of the present invention, the barrier gas can be any gas that does not react with PCC, PDA and carbon dioxide, such as nitrogen and inert gases.

[0058] In one specific embodiment of the present invention, a first liquid conveying device is provided on the connecting pipeline between the liquid outlet of the first gas-liquid separator and the pipeline reactor A. To ensure that the liquid separated by the first gas-liquid separator returns to the pipeline reactor A in a timely manner, the first liquid conveying device can be provided on the liquid return pipeline. For example, the first liquid conveying device can be a gear pump.

[0059] In one specific embodiment of the present invention, a second liquid conveying device is provided on the connecting pipeline between the liquid outlet of the second gas-liquid separator and the pipeline reactor B. To ensure that the liquid separated by the second gas-liquid separator returns to the pipeline reactor B in a timely manner, a second liquid conveying device can be provided on the liquid return pipeline. For example, the second liquid conveying device can be a gear pump.

[0060] In one specific embodiment of the present invention, the phosgene recovery device is connected to a vacuum system. To maintain the vacuum level in pipeline reactors B and C, and to allow the hydrogen chloride and some phosgene generated in pipeline reactor B to be removed in a timely manner, the phosgene recovery device can be connected to a vacuum system.

[0061] In one specific embodiment of the present invention, the vacuum system connected to the first gas-liquid separator and the vacuum system connected to the phosgene recovery device can be the same vacuum system, saving the manufacturing cost of the device; or they can be different vacuum systems, which facilitates precise control of the vacuum level inside the pipeline reactors A, B, and C.

[0062] In one specific embodiment of the present invention, the material outlet of the pipeline reactor C is connected to a product separation device, and the gas outlet of the product separation device is connected to a phosgene recovery device.

[0063] In one specific embodiment of the present invention, the product separation device is a negative pressure distillation device. The negative pressure distillation device can, on the one hand, promote the removal of products from the reaction system, increasing the reaction efficiency inside the tubular reactor C; on the other hand, it can separate the products from unreacted raw materials, obtaining pure products and recovering unreacted raw materials, thus reducing raw material costs.

[0064] In one specific embodiment of the present invention, the first gas-liquid separator and the second gas-liquid separator can be one of gravity sedimentation separator, centrifugal separator, inertial separator, and filter separator, preferably a centrifugal separator.

[0065] In one specific embodiment of the present invention, the phosgene recovery device is a commonly used device in the preparation of PDI by the phosgene method. Its structure is the same as that of existing phosgene recovery devices, so no further specific limitations are made to the phosgene recovery device here.

[0066] In this invention, traditional pipeline reactors are usually operated under pressure, which requires pressurizing phosgene before it can be introduced into the reaction system. Phosgene pressurizers are high-risk equipment. This invention avoids the aforementioned high-risk equipment and high-risk operations by removing gaseous substances from the reaction in stages and reducing the system pressure.

[0067] This invention provides a systematic method for preparing PDI from pentanediamine salt, which uses the system apparatus provided in one of the objectives. The systematic method includes:

[0068] The reactants containing PCC and catalyst decomposer enter the pipeline reactor A to carry out PCC decomposition reaction to obtain PDA. The carbon dioxide produced by the reaction enters the first gas-liquid separator through the gas outlet, and the separated liquid phase is returned to the pipeline reactor A.

[0069] PDA enters pipeline reactor B and undergoes an acyl chloride reaction with phosgene to obtain a product intermediate. The hydrogen chloride and some phosgene obtained from the reaction enter the second gas-liquid separator. The separated gas enters the phosgene recovery device, and the separated liquid is returned to pipeline reactor B.

[0070] The intermediate product enters the pipeline reactor C for reaction, the product material enters the product separation device to separate and obtain PDI, and the obtained gas enters the phosgene recovery device.

[0071] In one specific embodiment of the present invention, the catalytic decomposition agent includes any one or a combination of at least two of quaternary ammonium bases, quaternary ammonium salts, Lewis acids, quaternary phosphonium salts, or sulfonium salts.

[0072] In one specific embodiment of the present invention, the quaternary ammonium base includes C1-10 aliphatic or aromatic quaternary ammonium bases. Examples include tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrabutylammonium hydroxide, or tetraphenylammonium hydroxide.

[0073] In one specific embodiment of the present invention, the quaternary ammonium salt includes aliphatic or aromatic quaternary ammonium salts with C1 to 10 atoms. For example, the anionic portion of the quaternary ammonium salt can be a fluoride ion, chloride ion, bromide ion, or iodide ion. Further examples include tetramethylammonium bromide, tetramethylammonium chloride, tetraethylammonium bromide, tetraethylammonium chloride, tetraphenylammonium bromide, or tetraphenylammonium chloride, etc.

[0074] In one specific embodiment of the present invention, the Lewis acid includes any one or a combination of at least two of aluminum chloride, ferric chloride, or zinc chloride.

[0075] In one specific embodiment of the present invention, the quaternary phosphonium salt includes C1-10 aliphatic or aromatic quaternary phosphonium salts. For example, the anionic portion of the quaternary phosphonium salt can be a fluoride ion, chloride ion, bromide ion, or iodide ion. Further examples include tetrabutylphosphonium bromide, triphenylethylphosphonium bromide, tetraphenylphosphonium bromide, or triphenylmethylphosphonium chloride, etc.

[0076] In one specific embodiment of the present invention, the sulfonium salt includes aliphatic or aromatic sulfonium salts with C1 to 10 atoms. For example, the anionic portion of the sulfonium salt can be a fluoride ion, chloride ion, bromide ion, or iodide ion. Examples include trimethylsulfonium trifluoromethanesulfonate or triphenylsulfonium trifluoromethanesulfonate.

[0077] The present invention provides an economical and efficient catalytic decomposition agent for PCC decomposition. Adding a small amount significantly improves PCC decomposition efficiency while lowering decomposition temperature, reducing energy consumption, and enhancing the stability of the decomposition product, PDA. After the catalytic reaction in stage A is completed, the catalytic decomposition agent enters stage B. In the strongly acidic environment of stage B, the catalyst's polymerization activity cannot be released, and it rapidly reacts with hydrogen chloride and phosgene to form salts or becomes deactivated. Finally, it is discharged as a small amount of tar in the rectification stage. In other words, after completing the PCC decomposition in stage A, the catalytic decomposition agent does not adversely affect subsequent reactions.

[0078] In one specific embodiment of the present invention, the reaction temperature in the pipeline reactor A is 50~150℃, preferably 90~100℃; the vacuum degree is 4000~10000 Pa, preferably 5000~6000 Pa; and the residence time is 4~40 s, preferably 5~15 s, more preferably 8~10 s. The reaction temperature can be 50℃, 60℃, 70℃, 80℃, 90℃, 100℃, 110℃, 120℃, 130℃, 140℃, 150℃, or any value between any two of the above; the vacuum degree can be 4000 Pa, 5000 Pa, 6000 Pa, 7000 Pa, 8000 Pa, 9000 Pa, 1000 Pa, or any value between any two of the above; the residence time can be 4 s, 6 s, 8 s, 10 s, 12 s, 15 s, 20 s, 25 s, 30 s, 40 s, or any value between any two of the above.

[0079] In one specific embodiment of the present invention, the mass ratio of PCC to solvent in the reactants is 1 to 40:100, such as 1:100, 5:100, 10:100, 15:100, 20:100, 25:100, 30:100, 35:100, 40:100, and any two of the above values; preferably 25 to 30:100.

[0080] In one specific embodiment of the present invention, the flow rate of the separating gas is 1 to 5 times the flow rate of carbon dioxide, such as 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5 times, and any value between any two of the above values; preferably 2 times.

[0081] In one specific embodiment of the present invention, the reaction temperature in the pipeline reactor B is 100~200℃, preferably 110~130℃; the vacuum degree is 3000~7000 Pa, preferably 4000~5000 Pa; and the residence time is 2~30 s, preferably 4~15 s, more preferably 6~8 s. The reaction temperature can be 100℃, 110℃, 120℃, 130℃, 140℃, 150℃, 160℃, 170℃, 180℃, 190℃, 200℃, or any value between any two of the above; the vacuum degree can be 3000 Pa, 4000 Pa, 5000 Pa, 6000 Pa, 7000 Pa, or any value between any two of the above; the residence time can be 2s, 4s, 6s, 8s, 10s, 12s, 15s, 20s, 25s, 30s, or any value between any two of the above.

[0082] In one specific embodiment of the present invention, phosgene is in excess in the pipeline reactor B, and the molar ratio of phosgene to PDA is 2.2:1 to 15:1, such as 2.2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, and any two of the above values, preferably 8:1.

[0083] In one specific embodiment of the present invention, the amount of phosgene discharged from the pipeline reactor B is 10-86% of the amount of raw material phosgene entering, such as 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 86%, and any two of the above values, preferably 60-80%.

[0084] In this invention, timely removal of hydrogen chloride generated during the reaction in pipeline reactor B not only reduces system pressure but also decreases the generation of hydrolyzed chlorine and monochloroisocyanate; removal of some phosgene not only reduces system pressure but also decreases the generation of impurities such as polymers and hydrolyzed chlorine.

[0085] In one specific embodiment of the present invention, the reaction temperature in the pipeline reactor C is 150~300℃, preferably 200~250℃; the vacuum degree is 1000~5000 Pa, preferably 3000~4000 Pa; and the residence time is 2~30 s, preferably 4~15 s, more preferably 5~7 s. The reaction temperature can be 150℃, 160℃, 170℃, 180℃, 190℃, 200℃, 220℃, 250℃, 280℃, 300℃, or any value between any two of the above; the vacuum degree can be 1000 Pa, 2000 Pa, 3000 Pa, 4000 Pa, 5000 Pa, or any value between any two of the above; and the residence time can be 2 s, 4 s, 6 s, 8 s, 10 s, 12 s, 15 s, 20 s, 25 s, 30 s, or any value between any two of the above.

[0086] In one specific embodiment of the present invention, the total residence time of pipeline reactor A, pipeline reactor B and pipeline reactor C is 10~100 s, such as 10 s, 20 s, 30 s, 40 s, 50 s, 60 s, 70 s, 80 s, 90 s, 100 s and any two of the above values; preferably 20~30 s.

[0087] In one specific embodiment of the present invention, the residence time ratio of pipeline reactor A, pipeline reactor B and pipeline reactor C is 3:(1~3):(1~3), preferably 3:2.1:1.7.

[0088] In one specific embodiment of the present invention, the vacuum levels inside pipeline reactors A, B, and C should increase sequentially to avoid backflow and promote the entry of reaction products into the next reaction stage.

[0089] To better illustrate the present invention and facilitate understanding of its technical solutions, typical but non-limiting embodiments of the present invention are as follows:

[0090] Example M1

[0091] This embodiment provides a system apparatus for preparing PDI from pentanediamine salt, the system apparatus comprising pipeline reactor A, pipeline reactor B and pipeline reactor C connected in sequence;

[0092] The pipeline reactor A has a gas outlet at its tail end, which is connected to the gas inlet of the first gas-liquid separator. The liquid outlet of the first gas-liquid separator is connected to the material inlet of the pipeline reactor A. The gas outlet of the first gas-liquid separator is connected to a vacuum system. The material outlet of the pipeline reactor A is connected to the material inlet of the pipeline reactor B.

[0093] The head of the pipeline reactor B is provided with a phosgene inlet, and the tail of the pipeline reactor B is provided with a gas outlet. The gas outlet is connected to the gas inlet of the second gas-liquid separator, the liquid outlet of the second gas-liquid separator is connected to the material inlet of the pipeline reactor B, the gas outlet of the second gas-liquid separator is connected to the phosgene recovery device, and the material outlet of the pipeline reactor B is connected to the material inlet of the pipeline reactor C.

[0094] Example M2

[0095] This embodiment provides a system apparatus for preparing PDI from pentanediamine salt, the structure of which is as follows: Figure 1 As shown, the system includes pipeline reactor A, pipeline reactor B, and pipeline reactor C connected in sequence.

[0096] The pipeline reactor A has a reactant inlet at its head and an upward-opening gas outlet at its tail. The gas outlet is connected to the gas inlet of the first gas-liquid separator via a pipeline with a nitrogen inlet. The liquid outlet of the first gas-liquid separator is connected to the material inlet of the pipeline reactor A via a liquid phase pipeline with a first gear pump installed on the liquid phase pipeline. The gas outlet of the first gas-liquid separator is connected to a vacuum system. The material outlet of the pipeline reactor A is connected to the material inlet of the pipeline reactor B.

[0097] The head of the pipeline reactor B is provided with a phosgene inlet, and the tail of the pipeline reactor B is provided with an upward-opening gas inlet. The gas outlet is connected to the gas inlet of the second gas-liquid separator. The liquid outlet of the second gas-liquid separator is connected to the material inlet of the pipeline reactor B through a liquid phase pipeline. The liquid phase pipeline is equipped with a second gear pump. The gas outlet of the second gas-liquid separator is connected to a phosgene recovery device. The material outlet of the pipeline reactor B is connected to the material inlet of the pipeline reactor C.

[0098] The material outlet of pipeline reactor C is connected to a negative pressure distillation unit, and the gas outlet of the negative pressure distillation unit is connected to a phosgene recovery unit.

[0099] Examples A1-16

[0100] This embodiment provides a method for preparing PDI from pentanediamine salt. The method uses the system apparatus provided in Example M2 and includes the following steps:

[0101] The reactants containing PCC and catalyst decomposer enter the DN100 stainless steel pipeline reactor A with a diameter of 1 meter and a length of 1 meter to carry out the PCC decomposition reaction, and obtain a mixture of PDA and carbon dioxide. The carbon dioxide enters the first gas-liquid separator from the gas outlet. Nitrogen gas is introduced into the pipeline that transports carbon dioxide as a separating gas. The separated liquid phase is returned to the pipeline reactor A.

[0102] The obtained PDA enters the DN50 stainless steel pipeline reactor B with a diameter of 1 meter and a length of 1 meter to undergo an acyl chloride reaction with phosgene, and obtains the product intermediate and a mixture of hydrogen chloride and phosgene. The hydrogen chloride and part of the phosgene enter the second gas-liquid separator. The separated gas enters the phosgene recovery device, and the separated liquid is returned to the pipeline reactor B.

[0103] The obtained intermediate product enters reactor C, which is DN40 thick and 1 meter long, through a stainless steel pipe for reaction. The product material enters a negative pressure distillation device to separate PDI, and the obtained gas enters a phosgene recovery device.

[0104] Specifically, the first gas-liquid separator and nitrogen gas are turned on. PCC, ODCB, and the catalytic decomposition agent are mixed in a certain proportion and then transferred by a transfer pump to the preheated (temperature shown in Table 1) pipeline reactor A. After running for 30 minutes, samples are taken from the outlet of the A-section reaction tube for testing, and the yield and solid content are calculated. The conditions of pipeline reactor A and PDA yield in each embodiment are shown in Table 1.

[0105] Comparative Example A1 was carried out without the addition of a decomposition catalyst, with other conditions the same as in Example A1. The PCC decomposition reaction was carried out in pipeline reactor A, and the specific conditions and PDA yield are shown in Table 1.

[0106] Table 1

[0107]

[0108] In Table 1, the PDA solid content detection method involves sampling, weighing, filtering, freeze-drying the filter cake, weighing, and calculating the solid content (relative to the mass ratio of PCC feed), i.e., the proportion of undecomposed PCC. The decomposition catalyst dosage is the mass ratio of the decomposition agent dosage to the PCC feed. In Examples A1-16, the vacuum degree in pipeline reactor A is 6000-7000 Pa. The conditions in Example A1 represent the optimal conditions for the reaction in pipeline reactor A.

[0109] Example B1-19

[0110] Examples B1-19: After obtaining PDA according to the method and conditions of Example A1, PDI was prepared by pipeline reactors B and C.

[0111] Specifically, phosgene is preheated and introduced into pipeline reactor B. After 20 minutes, PCC, ODCB, and the catalyst are mixed under optimal conditions (see Table 1, A1) to obtain a mixture. This mixture is pumped into the preheated pipeline reactor A at a certain rate (total reaction residence time is determined by the feed rate). Simultaneously, gas-liquid separators A and B, pipeline reactors B and C are started and preheated. For the first 30 minutes, the effluent from pipeline C is discarded and does not enter the distillation system. After the entire reaction system has been running stably for 30 minutes, the feed rate is recorded, and the effluent from pipeline C is switched to the distillation system. Pure PDI is obtained through distillation, and the yield is calculated. The conditions in pipeline reactors B and C and the PDI yield are shown in Table 2.

[0112] In Comparative Example B1, only a small amount of phosgene was removed; all other conditions were the same as in Example B1. In Comparative Example B2, the reaction temperature in tubular reactor B was the same as the reaction temperature in tubular reactor C; all other conditions were the same as in Example B1. The conditions in tubular reactors B and C of Comparative Examples B1 and B2, as well as the PDI yield, are shown in Table 2.

[0113] Table 2

[0114]

[0115] In Table 2:

[0116] Phosgene quantity: The value is the molar ratio of phosgene to PDA; Phosgene discharge ratio of tube B: The mass ratio of the amount of phosgene entering the phosgene recovery system through tube B to the phosgene feed quantity; Hydrolyzed chlorine refers to the hydrolyzed chlorine before entering the distillation column, i.e., crude hydrolyzed chlorine; Example B1 in Table 2 is the optimal condition experiment.

[0117] Comparative Example C

[0118] Comparative Example C series describes the synthesis of PDI using PCC as a raw material in a single-pipe reactor. The specific reaction conditions are shown below:

[0119] Equipment: A DN100, 3-meter-long stainless steel dynamic mixing reactor. The reactor head is equipped with a reactant inlet and a phosgene feed inlet. The reactor material outlet is connected to a negative pressure distillation device, and the gas outlet of the negative pressure distillation device is connected to a phosgene recovery device.

[0120] Experiment: A mixture of PCC, ODCB, and 0.2% catalyst was fed into the tubular reactor through the inlet. Preheated phosgene was simultaneously fed into the reaction tubular reactor at a certain molar ratio (phosgene / PCC). The feed concentration, residence time, and reaction tube temperature are shown in Table 3 below. After 30 minutes of feeding, samples were taken at the outlet for testing, and the yield was calculated. The results are shown in Table 3.

[0121] Table 3

[0122]

Claims

1. A system apparatus for preparing PDI from pentanediamine salt, characterized in that, The system includes pipeline reactor A, pipeline reactor B, and pipeline reactor C connected in sequence. The pipeline reactor A is provided with a gas outlet at its tail end. The gas outlet is connected to the gas inlet of the first gas-liquid separator. The liquid outlet of the first gas-liquid separator is connected to the material inlet of the pipeline reactor A. The gas outlet of the first gas-liquid separator is connected to a vacuum system. The material outlet of the pipeline reactor A is connected to the material inlet of the pipeline reactor B. The pipeline reactor B has a phosgene inlet at its head and a gas outlet at its tail. The gas outlet is connected to the gas inlet of the second gas-liquid separator, the liquid outlet of the second gas-liquid separator is connected to the material inlet of the pipeline reactor B, the gas outlet of the second gas-liquid separator is connected to a phosgene recovery device, and the material outlet of the pipeline reactor B is connected to the material inlet of the pipeline reactor C.

2. The system apparatus for preparing PDI from pentanediamine salt according to claim 1, characterized in that, A gas separation inlet is provided on the pipeline connecting the gas outlet of the pipeline reactor A to the first gas-liquid separator.

3. The system apparatus for preparing PDI from pentanediamine salt according to claim 1, characterized in that, A first liquid conveying device is provided on the connecting pipeline between the liquid outlet of the first gas-liquid separator and the pipeline reactor A; A second liquid conveying device is provided on the connecting pipeline between the liquid outlet of the second gas-liquid separator and the pipeline reactor B.

4. The system apparatus for preparing PDI from pentanediamine salt according to claim 1, characterized in that, The phosgene recovery device is connected to a vacuum system.

5. The system apparatus for preparing PDI from pentanediamine salt according to claim 1, characterized in that, The material outlet of the pipeline reactor C is connected to the product separation device, and the gas outlet of the product separation device is connected to the phosgene recovery device. Preferably, the product separation device is a negative pressure distillation device.

6. A systematic method for preparing PDI from pentanediamine salt, characterized in that, The system method uses the system apparatus according to any one of claims 1-5, and the system method comprises: The reactants containing PCC and catalyst decomposer enter the pipeline reactor A to carry out PCC decomposition reaction to obtain PDA. The carbon dioxide produced by the reaction enters the first gas-liquid separator through the gas outlet, and the separated liquid phase is returned to the pipeline reactor A. The PDA enters the pipeline reactor B and undergoes an acyl chloride reaction with phosgene to obtain a product intermediate. The hydrogen chloride and part of the phosgene obtained from the reaction enter the second gas-liquid separator. The separated gas enters the phosgene recovery device, and the separated liquid is returned to the pipeline reactor B. The intermediate product enters the pipeline reactor C for reaction, the product material enters the product separation device to separate PDI, and the obtained gas enters the phosgene recovery device.

7. The systematic method for preparing PDI from pentanediamine salt according to claim 6, characterized in that, The catalytic decomposition agent includes any one or a combination of at least two of the following: quaternary ammonium base, quaternary ammonium salt, Lewis acid, quaternary phosphonium salt, or sulfonium salt; Preferably, the quaternary ammonium base includes C1-10 aliphatic or aromatic quaternary ammonium bases; Preferably, the quaternary ammonium salt comprises aliphatic or aromatic quaternary ammonium salts with C1 to 10 atoms; Preferably, the Lewis acid comprises any one or a combination of at least two of aluminum chloride, ferric chloride, or zinc chloride; Preferably, the quaternary phosphonium salt comprises C1-10 aliphatic or aromatic quaternary phosphonium salts; Preferably, the sulfonium salt comprises aliphatic or aromatic sulfonium salts of C1 to 10.

8. The systematic method for preparing PDI from pentanediamine salt according to claim 6, characterized in that, The reaction temperature in the pipeline reactor A is 50~150℃, preferably 90~100℃; the vacuum degree is 4000~10000 Pa, preferably 5000~6000 Pa; Preferably, the mass ratio of PCC to solvent in the reactants is 1~40:100, more preferably 25~30:100; Preferably, the flow rate of the separating gas is 1 to 5 times the flow rate of carbon dioxide, and more preferably 2 times.

9. The systematic method for preparing PDI from pentanediamine salt according to claim 6, characterized in that, The reaction temperature in the pipeline reactor B is 100~200℃, preferably 110~130℃; the vacuum degree is 3000~7000 Pa, preferably 4000~5000 Pa; Preferably, the molar ratio of phosgene to PDA in the pipeline reactor B is 2.2:1 to 15:1; Preferably, the amount of phosgene discharged from the pipeline reactor B is 10-86% of the amount of raw material phosgene entering, and more preferably 60-80%.

10. The systematic method for preparing PDI from pentanediamine salt according to claim 6, characterized in that, The reaction temperature in the pipeline reactor C is 150~300℃, preferably 200~250℃; the vacuum degree is 1000~5000 Pa, preferably 3000~4000 Pa; Preferably, the total residence time of pipeline reactors A, B, and C is 10-100 s, more preferably 20-30 s; Preferably, the residence time ratio of pipeline reactor A, pipeline reactor B and pipeline reactor C is 3:(1~3):(1~3).

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