Resin polymer, 1, 4-cyclohexane dimethyl diisocyanate with low chlorinated impurity content and continuous preparation method

Abstract

The invention relates to the field of polymers, in particular to a resin polymer, 1, 4-cyclohexane dimethyl diisocyanate (1, 4-H6XDI) with low chlorinated impurity content and a continuous preparation method of the resin polymer and the 1, 4-H6XDI. In the 1, 4-cyclohexane dimethyl diisocyanate with low chlorinated impurity content, the content of first monochlorinated isocyanate is 600 ppm or less, and the content of second monochlorinated isocyanate is 200 ppm or less. The 1, 4-cyclohexane dimethyl diisocyanate with low chlorinated impurity content meets the processing requirement that optical-grade polyurethane resin is sensitive to chlorine impurities. Chlorinated impurities are easy to decompose under high-temperature processing or ultraviolet radiation to generate hydrogen chloride, resulting in resin yellowing, stress cracking or refractive index fluctuation, so that optical-grade application has extremely strict requirements on the content of the chlorinated impurities.

Description

Technical Field

[0001] This invention relates to the field of polymers, and more specifically, to a resin polymer, 1,4-cyclohexanedimethyl diisocyanate (1,4-H6XDI) with low chlorinated impurity content, and a continuous preparation method thereof. Background Technology

[0002] 1,4-Cyclohexanedimethyl diisocyanate (abbreviated as 1,4-H6XDI) belongs to the ADI (aliphatic diisocyanate) family and is a hydrogenated product of isophthalimide diisocyanate (m-XDI). Due to its cyclic structure, its curing properties, such as rapid surface drying and hardness of cured products, are essentially similar to IPDI. 1,4-H6XDI products are mainly used in thermoplastic polyurethanes and cast polyurethane elastomers. Because this cyanate has highly reactive primary isocyanate groups and a trans structure, it is a non-yellowing, high-hardness, and highly elastic polyurethane or polyurea resin. 1,4-H6XDI polyurethane elastomers possess elasticity, heat resistance, and light stability that are not easily achieved simultaneously with conventional diisocyanates. Thermosetting polyurethane exhibits good resistance to flexural fatigue, and the prepolymer has good stability, while thermoplastic polyurethane elastomers exhibit excellent resilience, low compression set, and short demolding time during injection molding. It has wide applications in plastic lenses, automotive materials, packaging materials, and other fields.

[0003] 1,4-Cyclohexanedimethyl diisocyanate (1,4-H6XDI) belongs to the aliphatic diisocyanate (ADI) and is a hydrogenation product of m-XDI. It has a cyclic structure, high reactivity and excellent photostability, and is widely used in optical-grade TPU, transparent elastomers, automotive protective films and other fields.

[0004] In existing technologies, the synthesis of 1,4-H6XDI generally employs phosgene or solid-phase (BTC) routes, but both are accompanied by the formation of chlorinated byproducts (monochloroisocyanates). Since chlorine impurities pose a risk of corrosion and yellowing to downstream optical materials (such as lenses and automotive lamp films), existing processes cannot effectively remove these chlorinated impurities, resulting in the need for multiple distillation or adsorption treatments, leading to high costs and low yields.

[0005] Therefore, there is an urgent need for a continuous process that can produce 1,4-H6XDI with low chlorine content in one step to meet the needs of high-end optical applications. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a 1,4-cyclohexanedimethyl diisocyanate with low chlorination impurity content. The 1,4-cyclohexanedimethyl diisocyanate with low chlorination impurity content contains a first monochloroisocyanate content of less than 600 ppm and a second monochloroisocyanate content of less than 200 ppm. The structure of the first monochloroisocyanate is as follows:

[0007] And / or the structure of the second monochloroisocyanate is as follows:

[0008] On the other hand, a continuous preparation method for 1,4-cyclohexanedimethyl diisocyanate with low chlorination impurity content is also provided, comprising:

[0009] 1,4-cyclohexanedimethylamine, a solid-state light source, and a non-polar solvent were mixed and subjected to cold light, warm light, and hot light reactions to obtain crude 1,4-cyclohexane diisocyanate.

[0010] The crude 1,4-cyclohexane dimethyl diisocyanate was subjected to a thin-film evaporator to remove light component solvents and low-boiling substances, resulting in a desolventized product.

[0011] The desolventized material is subjected to primary distillation in a light-removal tower to remove the first monochloroisocyanate and the second monochloroisocyanate; the material after light-removal enters the product tower for secondary distillation to obtain 1,4-cyclohexanedimethyl diisocyanate with low chlorinated impurities.

[0012] Furthermore, the absolute pressure at the top of the light-light removal tower is 0.3–0.6 kPa, the temperature at the top of the tower is 100–115℃, the temperature at the bottom of the tower is 120–135℃, and the reflux ratio is 20–30.

[0013] Furthermore, the absolute pressure at the top of the product tower is 0.15–0.35 kPa, the temperature at the top of the tower is 110–125°C, the temperature at the bottom of the tower is 140–160°C, and the reflux ratio is 2–5.

[0014] Furthermore, the product tower is a composite tower consisting of an upper section of structured packing and a lower section of guide sieve plate.

[0015] Furthermore, the composite tower has a theoretical plate number of ≥20 and the opening ratio of the guide sieve plate is 12–15%.

[0016] Furthermore, the light-weight removal tower is a composite tower consisting of an upper section of structured packing and a lower section of floating valve trays.

[0017] Furthermore, the number of floating valve trays is 5 to 8.

[0018] Furthermore, the specific surface area of ​​the structured packing is 200–350 m². 2 / m3 The theoretical number of plates per meter is 3–6, and the pressure drop is 200 Pa / m.

[0019] Furthermore, the 1,4-cyclohexanedimethyl diisocyanate with low chlorination impurities is extracted via a second side-stream extraction device, wherein the second side-stream extraction is located at the 10th–12th theoretical plate of the product tower.

[0020] Furthermore, the second side-stream extraction device adopts a double-layer sleeve structure, wherein the inner tube is used to extract 1,4-cyclohexane dimethyl diisocyanate with low content of chlorinated impurities, and the outer tube sleeved on the outside of the inner tube is used to introduce refrigerant; more preferably, the side-stream extraction device also includes a sintered metal filter element; more preferably, the sintered metal filter element is 0.3 to 1 μm.

[0021] Furthermore, the second side-stream extraction includes a side-stream extraction cooler for cooling the extracted 1,4-cyclohexanedimethyl diisocyanate with low levels of chlorinated impurities.

[0022] Furthermore, at least one of nitrogen or rare gas is introduced during the second side-line extraction process.

[0023] Furthermore, the product tower also includes a liquid distributor, which is a combination of a tray type and a redistribution pipe;

[0024] Furthermore, the light-weight removal tower and product tower also include a reboiler, which is a vertical thermosiphon reboiler.

[0025] Furthermore, the light-weight removal tower and the product tower are each equipped with a cryogenic tail gas absorption system with an ultimate vacuum of 0.1 kPa.

[0026] On the other hand, a resin polymer is also provided, comprising the aforementioned 1,4-cyclohexanedimethyl diisocyanate with a low chlorinated impurity content.

[0027] The beneficial effects of this patent are:

[0028] 1. Continuous operation: The annual production capacity of a single unit is ≥3000t, which is 2.5 times higher than that of intermittent processes;

[0029] 2. Low energy consumption: Due to the lower pressure at the top of the tower, the temperature of the bottom of the tower can be reduced by at least 15–20°C, and steam consumption can be reduced by at least 30%;

[0030] 3. High separation efficiency: theoretical plate number ≥20, total removal rate of first monochloroisocyanate and second monochloroisocyanate ≥92%;

[0031] 4. Product stability: Low-temperature sampling from the side line + inert gas protection, hazen color <20, no visible change after 6 months of storage;

[0032] 5. The product contains very little monochloroisocyanate byproduct, which can be directly used in the preparation of resin.

[0033] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the description, claims, etc. Attached Figure Description

[0034] The accompanying drawings are provided to further understand the technical solutions of the present invention and constitute a part of the specification. They are used together with the embodiments of this application to explain the technical solutions of the present invention and do not constitute a limitation on the technical solutions of the present invention.

[0035] Figure 1 This is a post-processing flowchart of an embodiment of the present invention. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of specific embodiments of the present invention. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0037] One embodiment of the present invention provides a method for preparing 1,4-cyclohexanedimethyl diisocyanate with low chlorination impurities, comprising:

[0038] 1,4-cyclohexanedimethylamine, solid light (i.e., di(trichloromethyl) carbonate, BTC) and a nonpolar solvent are mixed and reacted under cold light, warm light and hot light to obtain crude 1,4-cyclohexane diisocyanate.

[0039] The crude 1,4-cyclohexane dimethyl diisocyanate was subjected to a thin-film evaporator to remove light component solvents and low-boiling substances, resulting in a desolventized product.

[0040] The desolventized material is subjected to primary distillation in a light-removal tower to remove the first monochloroisocyanate and the second monochloroisocyanate; the material after light-removal enters the product tower for secondary distillation to obtain 1,4-cyclohexanedimethyl diisocyanate with low chlorinated impurities.

[0041] Two-stage distillation can significantly reduce the impurity content of the first and second monochloroisocyanates.

[0042] In one embodiment of the present invention, 1,4-cyclohexanedimethylamine, a solid-state light source, and a non-polar solvent are mixed, and crude 1,4-cyclohexane diisocyanate is obtained by reacting it under cold light, warm light, and thermo-light conditions. The crude product comprises:

[0043] A curing solution and a 1,4-cyclohexanedimethylamine solution were prepared separately using a nonpolar solvent. The 1,4-cyclohexanedimethylamine solution was added dropwise to the curing solution at 0–50 °C to carry out a cold light reaction, and then the temperature was raised to 60–100 °C to carry out a warm light reaction. The curing solution was then added again, and the temperature was raised to 120–180 °C to carry out a thermo-light reaction. The total molar ratio of curing solution to 1,4-cyclohexanedimethylamine was 0.5–2:1.

[0044] The method of the present invention uses 1,4-cyclohexanedimethylamine and solid-light as reaction raw materials and a non-polar solvent as solvent. The reaction solution of 1,4-cyclohexane diisocyanate is obtained by mixing, cold light, warm light, and hot light (adding solid-light to stabilize the solid-light concentration and make the reaction proceed in the forward direction).

[0045] By dynamically supplementing solidification light during the thermo-photonic stage, the problem of side reactions caused by concentration fluctuations is solved. In synergy with three-stage gradient temperature control (matching reaction / byproduct decomposition kinetics), the selectivity is increased from the traditional 40%–70% to over 90% based on solidification light replacing phosgene.

[0046] This invention uses solid phosgene instead of highly toxic phosgene, which simplifies process safety control requirements, improves production and storage safety, extends equipment lifespan, and is easy to scale up for production.

[0047] The method of the present invention reduces the amount of solidification input in the cold light stage, and continuously and slowly adds solidification during the reaction to stabilize the solidification content in the reaction solution and enable the reaction to proceed in the forward direction.

[0048] In one embodiment of the present invention, the curing solution is dynamically added during the thermo-photonic reaction stage, and the curing solution is added over a period of 1 to 6 hours.

[0049] In one embodiment of the present invention, the cold light reaction time is 0.5 to 3 hours; the warm light reaction time is 0.5 to 8 hours; and the hot light reaction time is 1 to 6 hours.

[0050] In one embodiment of the present invention, the content of the added curing solution in curing solution accounts for 40% to 70% of the total curing amount.

[0051] In one embodiment of the present invention, the thermo-photochemical reaction is carried out in two stages: first, the reaction is carried out at 120°C for 0.5 to 4 hours, and then at 160°C for 0.5 to 2 hours.

[0052] In one embodiment of the present invention, stirring is performed in the cold light reaction stage, the warm light reaction stage, and the hot light reaction stage, and the stirring rate is controlled to be 200-500 rpm.

[0053] In one embodiment of the present invention, during the cold photoreaction stage, the initial molar ratio of the solidification solution to 1,4-cyclohexanedimethylamine in the solidification solution is 0.3 to 1.2:1.

[0054] In one embodiment of the present invention, the gases generated during the cold light reaction, warm light reaction and hot light reaction stages are collected, passed into an alkaline solution, and then dehydrated, boiled down, and recovered.

[0055] In one embodiment of the present invention, the non-polar solvent obtained after the reaction solution is desolventized is recycled and reused.

[0056] In one embodiment of the present invention, the nonpolar solvent is 1,2-dichlorobenzene, xylene, n-hexane, or cyclohexane.

[0057] In one embodiment of the present invention, the nonpolar solvent is more preferably 1,2-dichlorobenzene.

[0058] In one embodiment of the present invention, as Figure 1 As shown, the impurity removal process (post-treatment) for crude 1,4-cyclohexane diisocyanate is as follows:

[0059] The solution is cooled to <60℃ and filtered under nitrogen pressure to remove solid residue. The filtrate is then introduced into a vacuum distillation system to recover 1,2-dichlorobenzene, yielding crude 1,4-H6XDI. The crude 1,4-H6XDI is pumped into a thin-film evaporator for pretreatment to remove the light component solvent dichlorobenzene and ultra-low boiling points, yielding a desolventized product. This desolventized product is pumped into a light component removal column, and the reboiler is started. The temperature is increased, and simultaneously, the column top condenser, condenser, and vacuum system are activated. The pressure and temperature parameters of the light component removal column are controlled. Low-boiling points begin to distill off. The column top outlet valve is then closed, and total reflux is applied for 20–30 minutes until the column top temperature stabilizes at 45–60℃ and the purity of 1,4-H6XDI in the reflux liquid is ≥99.0% (G). C) To establish a stable concentration and temperature gradient, the first side-stream extraction device is activated, and the low-boiling components (first monochloroisocyanate and second monochloroisocyanate) enter the light component storage tank. The non-condensable gases are recovered by cooling in a low-temperature condenser (coolant: ethylene glycol, water, -10℃). The material passing through the light component removal tower is discharged from the bottom of the reactor into the product tower. The product tower reboiler is started and the temperature is raised. At the same time, the product tower top condenser, condenser, and vacuum system are activated to control the temperature, pressure, and other parameters of the product tower. After reflux for a period of time, the second side-stream extraction device is activated, and 1,4-H6XDI enters the product tank. The non-condensable gases are recovered by cooling in a low-temperature condenser (coolant: ethylene glycol, water, -10℃). The heavy components at the bottom of the tower enter the residue tank.

[0060] The post-processing technology of this invention has an annual production capacity of ≥3000t per unit, which is at least 2.5 times higher than that of intermittent processes.

[0061] In one embodiment of the present invention, the absolute pressure at the top of the light-light removal tower is 0.3–0.6 kPa, the temperature at the top of the tower is 100–115°C, the temperature at the bottom of the tower is 120–135°C, and the reflux ratio is 20–30.

[0062] In one embodiment of the present invention, the absolute pressure at the top of the product tower is 0.15–0.35 kPa, the temperature at the top of the tower is 110–125°C, the temperature at the bottom of the tower is 140–160°C, and the reflux ratio is 2–5.

[0063] Because the top pressure of this invention is as low as 0.15 kPa, the bottom temperature of the column can be reduced by at least 15–20°C, and steam consumption can be reduced by at least 30%; when the top pressure is as low as 0.35 kPa, steam consumption can be reduced by at least 10%. This setting of the top pressure can greatly reduce energy consumption.

[0064] In one embodiment of the present invention, the product tower is a composite tower consisting of an upper section of structured packing and a lower section of guide sieve plate.

[0065] By using a composite tower, the core advantages of the upper structured packing section (high mass transfer efficiency and numerous theoretical plates) can be fully utilized, while the advantages of the lower guided sieve plate section (large processing capacity and stable mass transfer efficiency) can also be leveraged. Furthermore, choosing a composite tower results in more stable operation, with the lower section being more resistant to interference and the upper section more resistant to fluctuations.

[0066] In one embodiment of the present invention, the theoretical number of trays in the product tower composite tower is ≥20 and the opening ratio of the guide sieve plate is 12–15%.

[0067] In one embodiment of the present invention, the theoretical tower weir height of the product tower composite tower is 30 mm, the downcomer area ratio is 10%, and the pressure drop is 150 Pa / plate.

[0068] Selecting this parameter ensures that the total removal rate of the first and second monochloroisocyanates is ≥92%.

[0069] In one embodiment of the present invention, the light-weight removal tower is a composite tower consisting of an upper section of structured packing and a lower section of floating valve trays.

[0070] Choosing the upper section structured packing allows for high-precision purification and deep removal of trace impurities; choosing the lower section floating valve tray allows for efficient coarse separation and rapid removal of large amounts of impurities.

[0071] In one embodiment of the present invention, the floating valve tray consists of 5-8 pieces.

[0072] In one embodiment of the present invention, the specific surface area of ​​the structured packing is 200-350 m². 2 / m 3 The theoretical number of plates per meter is 3–6, and the pressure drop is 200 Pa / m.

[0073] The light-weight removal tower uses 316L stainless steel structured packing (250Y), while the product tower uses 316L stainless steel high-throughput structured packing (350Y).

[0074] In one embodiment of the present invention, 1,4-cyclohexanedimethyl diisocyanate with low chlorination impurities is extracted via a second side-stream extraction device, wherein the second side-stream extraction is located at the 10th–12th theoretical plate of the product tower.

[0075] Setting up a second side-stream extraction device here can ensure accurate component separation, guarantee the purity of 1,4-cyclohexanedimethyl diisocyanate, optimize energy consumption and cost, and provide better operational flexibility.

[0076] In one embodiment of the present invention, the second side-line extraction device adopts a double-layer sleeve structure, wherein the inner tube is used to extract 1,4-cyclohexane dimethyl diisocyanate with low content of chlorinated impurities, and the outer tube sleeved on the outside of the inner tube is used to introduce refrigerant.

[0077] The refrigerant can be 20℃ circulating water, and the double-layer sleeve structure can achieve rapid cooling of the product to ≤60℃, suppressing the rise of thermal color.

[0078] The inner tube of the double-layered casing is directly connected to the outlet of the second side line device of the product tower; the outer tube is sleeved on the outside of the inner tube, and both ends are sealed by flanges or welding to form a sealed interlayer, which mainly serves to "contain the temperature control medium and keep it warm".

[0079] In one embodiment of the present invention, the side-line extraction device further includes a sintered metal filter element. This element can be used to intercept filler powder and polymer particles.

[0080] In one embodiment of the present invention, the sintered metal filter element is 0.5 μm. Choosing this filter element size effectively intercepts tiny solid particles, colloids, and other impurities in the side-stream produced fluid, ensuring the purity and quality of the produced product.

[0081] In one embodiment of the present invention, the second side-stream extraction includes a side-stream extraction cooler for cooling the extracted 1,4-cyclohexanedimethyl diisocyanate with low chlorinated impurity content. This reduces product stability risks and also meets the temperature requirements of subsequent processes / storage.

[0082] In one embodiment of the present invention, at least one of nitrogen or rare gas is introduced during the second side-line extraction process.

[0083] By employing side-stream cryogenic extraction and inert gas protection, the hazen color of 1,4-cyclohexanedimethyl diisocyanate can be kept <20, with no visible changes after 6 months of storage.

[0084] In one embodiment of the present invention, the product tower further includes a liquid distributor, which is a combination of a tray type and a redistribution pipe. This ensures uniform liquid distribution and avoids localized overheating.

[0085] In one embodiment of the present invention, the light-weight removal tower and the product tower further include a reboiler, wherein the reboiler is a vertical thermosiphon reboiler.

[0086] The shell side of the vertical thermosiphon reboiler is filled with heat transfer oil, the tube side is filled with 1,4-H6XDI, and the heat transfer area is 10m². 2 •h / t throughput. Simultaneously, a temperature gradient control is implemented: the shell-side oil temperature is 5–10°C higher than the bottom liquid phase temperature to prevent localized overheating.

[0087] In one embodiment of the present invention, the light-light removal tower and the product tower are respectively equipped with a cryogenic tail gas absorption system, and the ultimate vacuum of the light-light removal tower and the product tower is 0.1 kPa.

[0088] In one embodiment of the present invention, the heavy components (containing polymeric impurities and high-boiling Cl- compounds) at the bottom of the product tower are intermittently discharged to the residue treatment unit. The heavy components are incinerated in a closed system, and the HCl is absorbed by alkaline washing. The emissions meet national standards, do not produce pollution, and are relatively environmentally friendly.

[0089] The present invention also provides a 1,4-cyclohexanedimethyl diisocyanate with low content of chlorinated impurities, which is prepared by the above method.

[0090] The present invention also provides a 1,4-cyclohexanedimethyl diisocyanate with low content of chlorinated impurities, wherein the content of the first monochloroisocyanate is 0.2 ppm to 600 ppm, and the content of the second monochloroisocyanate is less than 200 ppm, wherein the structure of the first monochloroisocyanate is as follows:

[0091] And / or the structure of the second monochloroisocyanate is as follows:

[0092] In one embodiment of the present invention, the color of 1,4-cyclohexanedimethyl diisocyanate with low content of chlorinated impurities is 4-20.

[0093] This 1,4-cyclohexanedimethyl diisocyanate with low chlorine impurity content meets the processing requirements of optical-grade polyurethane resins that are sensitive to chlorine impurities.

[0094] The present invention also provides a resin polymer comprising 1,4-cyclohexanedimethyl diisocyanate with a low content of the above-mentioned chlorinated impurities.

[0095] To more clearly illustrate the technical solution of this application, the following embodiments and comparative examples are provided.

[0096] Example 1

[0097] (1) Preparation of curing solution

[0098] Add 200 kg of 1,2-dichlorobenzene to a 2000 L glass-lined reactor (with jacket, stirrer, thermometer, condenser, and dropping vessel), start stirring (150 rpm), and cool to below 10 °C.

[0099] Slowly add 100 kg of bleaching agent, and after dissolving, a bleaching agent solution is formed.

[0100] (2) Preparation of 1,4-cyclohexanedimethylamine solution

[0101] Add 100 kg of 1,4-cyclohexanedimethylamine and 250 kg of 1,2-dichlorobenzene to a dropping vessel, stir to dissolve, and protect with nitrogen.

[0102] (3) Cold light reaction (low-temperature phosgenesis)

[0103] Slowly add 1,4-cyclohexanedimethylamine solution to the curing solution, controlling the temperature at 15–20°C;

[0104] Dropping time: 2–4 hours (to avoid local overheating and side reactions);

[0105] After the addition is complete, keep warm for 3 hours, and continue stirring at a speed of 350 rpm.

[0106] (4) Temperature and light reaction

[0107] Heat to 80℃ and keep warm for 5 hours.

[0108] Exhaust gas absorption (alkaline solution absorbs HCl and phosgene)

[0109] (5) Thermo-optic reaction + supplementary light-fixing

[0110] The temperature was raised to 120℃ and held for 3 hours. Then the temperature was raised to 160℃ and held for 2 hours. During the holding period, a pre-dissolved solution of 175 kg of bleach + 500 kg of 1,2-dichlorobenzene was continuously added dropwise.

[0111] Nitrogen protection throughout the process, and alkaline scrubbing of the exhaust gas.

[0112] (6) Post-processing

[0113] Cool to below 60℃, then filter under nitrogen pressure to remove solid filter residue;

[0114] The filtrate was fed into a vacuum distillation system to recover 1,2-dichlorobenzene and obtain the crude product.

[0115] Feed pretreatment: The crude product 1,4-H6XDI (hydrolyzed chlorine HC 650ppm, first monochloroisocyanate 7000ppm, second monochloroisocyanate 2300ppm) is desolventized by a thin-film evaporator at 90℃ and 2kPa to remove light component solvents and low-boiling substances, to obtain desolventized material.

[0116] The above-mentioned desolventized material was subjected to two-stage distillation:

[0117] Remove Light Tower (T1)

[0118] Tower type: A composite structure consisting of upper section structured packing (250Y) and lower section floating valve trays (6 pieces);

[0119] Operating parameters: Top pressure 0.45 kPa; Top temperature 115℃; Bottom temperature 135℃;

[0120] Reflux ratio 20;

[0121] The light component distillate D1 (containing the first monochloroisocyanate and the second monochloroisocyanate) is recovered after being collected via the first side stream.

[0122] Product Tower (T2)

[0123] Operating parameters: Top pressure 0.3 kPa; Top temperature 120℃; Bottom temperature 150℃;

[0124] Reflux ratio 2;

[0125] The second side profile yielded 1,4-H6XDI products.

[0126] Results: The side stream yielded 430 kg / h of product. Cooling with circulating water at 20°C reduced the product temperature from 135°C to 60°C. The concentrations were: HC 85 ppm, first monochloroisocyanate 550 ppm, second monochloroisocyanate 150 ppm, color 18, and yield 86%.

[0127] The heavy component B2 (containing polymeric impurities and high-boiling Cl- compounds) at the bottom of the tower is intermittently discharged to the residue treatment unit.

[0128] Example 2

[0129] The methods and parameters for the synthesis and pretreatment of the crude product are the same as those in Example 1.

[0130] Maintain the top pressure of T2 (product tower) at 0.18 kPa, and keep the other parameters the same as in Example 1.

[0131] Results: Product yield from the side stream was 440 kg / h, HC was 60 ppm, and the first monochloroisocyanate was present.

[0132] 160 ppm, second monochloroisocyanate 115 ppm, color 12, yield 88%, energy consumption reduced by 8% compared to Example 1.

[0133] Example 3

[0134] The methods and parameters for the synthesis and pretreatment of the crude product are the same as those in Example 1.

[0135] The conditions for two-stage distillation are as follows:

[0136] T1 (Lightweight Filtering Tower) Operation: Top of the tower 0.3 kPa, 100℃; Bottom of the tower 120℃; Reflux ratio 30;

[0137] T2 (product tower) operation: top of tower 0.15 kPa, 110°C; bottom of tower 140°C; reflux ratio 5; other conditions are the same as in Example 1.

[0138] The side stream yielded 440 kg / h of product. Cooling with circulating water at 20°C reduced the product temperature from 135°C to 60°C. The product contained 85 ppm HC, 15 ppm of the first monochloroisocyanate, 25 ppm of the second monochloroisocyanate, a color of 8, and a yield of 88%.

[0139] Comparative Example 1

[0140] The methods and parameters for the synthesis and pretreatment of the crude product are the same as those in Example 1.

[0141] The single distillation method is as follows:

[0142] The bottom temperature of the column was 140℃, the top temperature was 112℃, the absolute pressure at the top was 0.3kPa, the reflux ratio was 12, the theoretical number of plates was 10, and the yield of 1,4-cyclohexanedimethyl diisocyanate was 75%. After one distillation, the product still had a high level of chlorinated impurities (750ppm of the first monochloroisocyanate and 180ppm of the second monochloroisocyanate).

[0143] As can be seen from the examples and comparative examples, the product obtained in Comparative Example 1 has more chlorinated impurities. Therefore, the resin prepared from this product cannot meet the processing requirements of optical grade polyurethane resin, which is sensitive to chlorine impurities. Comparing Example 3 with Comparative Example 1, under the same processing capacity (500 kg / h), the steam consumption in Example 3 decreased from 1.8 t / t (Comparative Example 1) to 1.26 t / t (Example 3), a reduction of 30%.

[0144] While the embodiments disclosed in this invention are as described above, the content is merely for the purpose of facilitating understanding of the invention and is not intended to limit the invention. Any person skilled in the art to which this invention pertains may make any modifications and changes to the form and details of the implementation without departing from the spirit and scope disclosed herein; however, the scope of patent protection for this invention shall still be determined by the scope defined in the appended claims.

Claims

1. 1,4-cyclohexane dimethanol diisocyanate having a low content of chlorinated impurities, characterized in that, The 1,4-cyclohexane dimethanol diisocyanate having a low content of chlorinated impurities has a content of a first monochlorinated isocyanate of 600 ppm or less and a content of a second monochlorinated isocyanate of 200 ppm or less, wherein the first monochlorinated isocyanate has the structure and / or the second monochloro isocyanate has the structure 2. A continuous process for the preparation of 1,4-cyclohexane dimethyldiisocyanate with low content of chlorinated impurities, characterized in that, The application relates to a method for preparing 1,4-cyclohexane dimethyl diisocyanate with low content of chlorinated impurities. The method comprises the following steps: mixing 1,4-cyclohexane dimethyl amine, solid light and non-polar solvent, removing light components and low-boiling substances through cold light, warm light and hot light reactions, and obtaining a crude product 1,4-cyclohexane dimethyl diisocyanate; The crude product 1,4-cyclohexane dimethyl diisocyanate is subjected to light component removal through a thin film evaporator to obtain a desolventized material; The desolventized material is subjected to first-stage rectification through a light component removal column to remove first and second monochloro isocyanates; the light component-removed material is subjected to second-stage rectification through a product column to obtain 1,4-cyclohexane dimethyl diisocyanate with low content of chlorinated impurities.

3. The preparation method according to claim 2, characterized in that, The light component removal column has an absolute pressure of 0.3-0.6 kPa, a top temperature of 100-115 DEG C, a bottom temperature of 120-135 DEG C and a reflux ratio of 20-30; The product column has an absolute pressure of 0.15-0.35 kPa, a top temperature of 110-125 DEG C, a bottom temperature of 140-160 DEG C and a reflux ratio of 2-5.

4. The production method according to claim 2, characterized by, The product column is a composite column with regular packing in the upper section and a guide sieve plate in the lower section; Preferably, the composite column has a theoretical plate number of not less than 20 and the guide sieve plate has an opening rate of 12-15%. The light component removal column is a composite column with regular packing in the upper section and a float valve plate in the lower section; Preferably, the float valve plate is 5-8 pieces.

5. The preparation method according to claim 2, characterized in that, The specific surface area of the structured packing is 200-350 m 2 / m 3 The theoretical plate number per meter is 3-6 pieces, and the pressure drop is 200 Pa / m.

6. The preparation method according to claim 2, characterized in that, The 1,4-cyclohexane dimethyl diisocyanate with low content of chlorinated impurities is collected through a second side line collection device, wherein the second side line collection is arranged at the 10th-12th theoretical plate of the product column; Preferably, the second side line collection device adopts a double-layer sleeve structure, wherein an inner tube is used to collect the 1,4-cyclohexane dimethyl diisocyanate with low content of chlorinated impurities, and an outer tube sleeved outside the inner tube is connected with a refrigerant; further preferably, the side line collection device further comprises a metal sintered filter element; further preferably, the metal sintered filter element is 0.3-1 mu m.

7. The preparation method according to claim 6, characterized in that, The second side line collection comprises a side line collection cooler for cooling the collected 1,4-cyclohexane dimethyl diisocyanate with low content of chlorinated impurities; At least one of nitrogen or rare gas is introduced into the second side line collection process.

8. The preparation method according to claim 2, characterized in that, The product column further comprises a liquid distributor which adopts a combination of a groove disc and a redistribution pipe; The light component removal column and the product column are respectively provided with a deep cold tail gas absorption system with a limit vacuum of 0.1 kPa.

9. The method of claim 2, wherein, The application further discloses the 1,4-cyclohexane dimethyl diisocyanate with low content of chlorinated impurities.

10. A resin polymer, characterized by, ​

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