A process for the preparation of light-colored isocyanates, polyurethanes

Abstract

The present application relates to the technical field of isocyanate preparation, and particularly relates to a method for preparing light-colored isocyanate and polyurethane. The method comprises the process of preparing isocyanate by phosgenation reaction with an amine compound as a raw material; wherein the amine compound raw material is prepared by hydrogenation reaction, and when characterized by ultraviolet spectrophotometry, the amine compound raw material satisfies: with anhydrous ethanol as a blank sample, in a 0.1wt% ethanol solution, the absorbance at the maximum absorption wavelength is less than or equal to 2.5. The method can be applied to the preparation of isocyanate with all amine compounds prepared by hydrogenation reaction as raw materials, has good universality, and is simple, fast, low in cost, stable in characterization result, and the prepared isocyanate has the characteristics of light color or colorlessness.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of isocyanate preparation, in particular to a method for preparing light-colored isocyanate and polyurethane. BACKGROUND

[0002] Isocyanate, as an intermediate of organic synthesis, is widely used in various industries such as industry, agriculture, construction, automobile, and thermal insulation, because it can be further synthesized into polymeric isocyanate, polyurethane, polyurea, spandex, etc. The mainstream method for synthesizing isocyanate in the industry is phosgenation. However, due to various reasons such as raw material composition, preparation process, and post-treatment, the color value of the prepared isocyanate is usually high, which is not conducive to downstream applications, especially for polyurethane. The polyurethane prepared from high-color isocyanate usually has the problems of high color value and poor discoloration resistance.

[0003] In order to solve the influence of isocyanate color value on downstream products, it has been considered an effective solution to treat the material after phosgenation reaction to improve the color of isocyanate product. However, many coloring substances in isocyanate come from raw material components (also partly from the reaction results of trace components in raw materials), and the by-products generated during the phosgenation reaction also cause product coloring. The color treatment in the stage after the phosgenation reaction requires a large amount of engineering cost and does not obviously improve the color number. In addition, the color treatment in the stage after the phosgenation reaction mostly introduces other impurities, which will form non-desired by-products in the downstream application of isocyanate.

[0004] Therefore, with the development of technology, it has become more acceptable to treat or purify the starting amine substance or its oligomers before phosgenation reaction, and many technologies have been disclosed.

[0005] Patent application No. EP0546398A discloses acidifying treatment of polymethylene polyphenylene polyamine before phosgenation to produce low-color isocyanate product.

[0006] Patent application No. EP0446781A discloses a process for producing a lighter color MDI by first treating polymeric MDA (monomeric and oligomeric polymethylene polyphenylene polyamine) with hydrogen gas, and then phosgenating.

[0007] Patent application No. CN103319372A discloses a method for preparing light-colored or colorless diisocyanate of di-cyclohexyl methane (HMDI) by controlling the content of alcohol compounds in the raw material di-cyclohexyl methane diamine to be less than 0.2%, and then performing phosgenation reaction, distillation, and rectification.

[0008] Patent application with publication number CN1356980A discloses a method for preparing light-colored isocyanate by first controlling the content of bromine or iodine molecules or mixture thereof in phosgene to be less than 25 ppm, and then performing a phosgenation reaction between the above-mentioned phosgene and a diphenylmethane diamine series amine or a mixture of multiple such amines.

[0009] It can be seen that, in the prior art including the above disclosure, in order to solve the low color value of isocyanate product and the influence on downstream products, the content of certain impurities in specific amine substances of starting materials is taken as a purity standard, the universality is limited, and it cannot be applied to the preparation of other isocyanates; on the other hand, in order to determine the purity of the raw material, specific detection and analysis means need to be introduced according to the preset processing object, which is not only complicated and expensive, but also has many interference factors, which will affect the sensitivity and accuracy of the results. Therefore, there is an urgent need in the art to provide a method for determining the purity of raw material amine by a fast and simple characterization method, and then more conveniently preparing light-colored isocyanate on the production line. SUMMARY

[0010] The present application provides a method for preparing light-colored isocyanate, which determines the amine compound that meets the requirements as a raw material by using ultraviolet spectrophotometry to characterize the raw material amine compound, so that the prepared isocyanate is light-colored or colorless, the characterization method of the raw material is simple, fast and stable, and the quality control of the raw material and the low cost of the target product production can be realized.

[0011] The present application also provides a quality control method for a raw material amine compound for preparing light-colored isocyanate, which is convenient and practical to operate.

[0012] The present application also provides a light-colored isocyanate, which is light-colored and not prone to yellowing.

[0013] The present application also provides a polyurethane, which has excellent discoloration resistance.

[0014] The present application achieves the above technical purpose by the following technical solutions:

[0015] A method for preparing light-colored isocyanate, comprising using an amine compound as a raw material to prepare isocyanate by a phosgenation reaction; wherein,

[0016] The amine compound raw material is prepared by a hydrogenation reaction, and when characterized by ultraviolet spectrophotometry, it meets the following condition: in anhydrous ethanol as a blank sample, in a 0.1wt% ethanol solution, at the maximum absorption wavelength, the absorbance is ≤2.5.

[0017] According to the above preparation method, the amine compound raw material is prepared by a hydrogenation reaction; and / or the amine compound raw material is a cycloaliphatic amine.

[0018] The preparation method satisfies that the maximum absorption wavelength is 203 nm, and / or the amine compound satisfies that the absorbance is less than or equal to 2.0.

[0019] The preparation method further comprises the process of subjecting the amine compound raw material to an epoxidation treatment and purification, so as to satisfy the absorbance characterized by the ultraviolet spectrophotometry.

[0020] The preparation method satisfies that the epoxidation treatment method comprises: reacting the amine compound raw material with an epoxidation reagent, and at least oxidizing the unsaturated hydrocarbon compound in the amine compound raw material into an epoxide compound; and / or the temperature of the epoxidation treatment is 0-40℃.

[0021] The preparation method satisfies that the epoxidation reagent is butanone peroxide, sodium hypochlorite or a high-valence iodine reagent.

[0022] The preparation method further comprises the step of separating and purifying the isocyanate prepared by the phosgenation reaction.

[0023] The application further provides a quality control method for an amine compound raw material for preparing a light-color isocyanate, specifically: the amine compound raw material is prepared by a hydrogenation reaction, and satisfies that the absorbance is less than or equal to 2.5, characterized by ultraviolet spectrophotometry with anhydrous ethanol as a blank sample at the maximum absorption wavelength in a 0.1wt% ethanol solution.

[0024] The application further provides a light-color isocyanate, the initial platinum-cobalt color number of the isocyanate is not higher than 10, the platinum-cobalt color number is not higher than 35 after being placed in an environment at 60℃ for 24h; and / or the isocyanate is prepared by the above method.

[0025] The application further provides a method for preparing a polyurethane, comprising preparing an isocyanate by the above method, and then polymerizing the isocyanate with a polyol.

[0026] The method for preparing a light-color isocyanate provided by the application can be applied to the preparation of all isocyanates using an amine compound prepared by a hydrogenation reaction as a raw material, has good universality, is simple, fast and low in cost, and has stable characterization results, so as to ensure that the prepared isocyanate has a stable low color value.

[0027] The quality control method for an amine compound raw material for preparing a light-color isocyanate provided by the application is convenient and practical to operate, and is more conducive to controlling the quality of the raw material.

[0028] The polyurethane provided by the application has excellent discoloration resistance. DETAILED DESCRIPTION

[0029] To make the objectives, technical solutions, and advantages of the present application clearer, the following will combine embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are some embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0030] Based on the problems that the existing preparation method of light-color isocyanate is not high in universality and complicated in operation, the present application provides a method for preparing light-color isocyanate, comprising the following steps: first, determining the amine compound to meet the requirements by ultraviolet spectrophotometry, and then preparing isocyanate through phosgenation reaction.

[0031] The amine compound raw material is prepared through hydrogenation reaction, and when characterized by ultraviolet spectrophotometry, it meets the following requirement: in the 0.1wt% ethanol solution, the maximum absorption wavelength is less than or equal to 2.5.

[0032] The present application characterizes the amine compound by ultraviolet spectrophotometry, so as to determine the amine compound meeting the standard as the raw material to prepare isocyanate through phosgenation reaction. The method is suitable for the preparation of isocyanate using all amine compounds prepared through hydrogenation reaction as the raw material, and the prepared isocyanate product has stable low color value quality. According to the method of the present application, the color value of the prepared isocyanate is characterized by platinum-cobalt color number, which can be not higher than 10.

[0033] According to the present application, the raw material is characterized and screened by ultraviolet spectrophotometry, which is aimed at all amine compounds prepared through hydrogenation reaction, that is, good universality, and has the advantages of cheap analysis instrument, simple sample treatment, simple operation, fast response, high sensitivity, low background signal, and low cost, which is conducive to large-scale application.

[0034] The method is suitable for amine compounds prepared through hydrogenation reaction, because in the process of preparing amine compounds through hydrogenation reaction, when there is incomplete hydrogenation and side reaction, the impurities in the raw material may be mainly unsaturated hydrocarbons. These impurities are difficult to separate in the rectification and purification of amine compounds, and contain C=C unsaturated bond, which can be easily detected and controlled by ultraviolet spectrophotometry.

[0035] According to the setting of the target isocyanate, in some embodiments, the amine compound is selected from alicyclic amines such as 4,4'-diaminodicyclohexyl methane (HMDA), cyclohexyl dimethylene diamine (HXDA), cyclohexane diamine (CHDA), etc., and the chemical formula of the unsaturated hydrocarbon impurities thereof is as shown in formula (I) and formula (II):

[0036] wherein R is selected from one or more of amino, methylene amine, methylene cyclohexyl amine, hydrogen, methyl, ethyl, n-propyl, isopropyl, ester, t-butyl, halogen.

[0037] It can be understood that the selection of the specific amine compound raw material can prepare the corresponding isocyanate product. For example, in some specific embodiments, the prepared isocyanate is an alicyclic polyisocyanate, such as dicyclohexyl methane diisocyanate (HMDI), cyclohexyl dimethylene diisocyanate (HXDI), cyclohexane diisocyanate (CHDI), etc.

[0038] The amine compound prepared by the hydrogenation reaction according to the present application refers to the product obtained by one or two or even multiple hydrogenation reactions of unsaturated amines by the conventional hydrogenation preparation method. For example, when the amine compound is alicyclic amine, the alicyclic amine can be prepared by using a catalyst and a cocatalyst to convert aromatic amine and hydrogen into alicyclic amine with high activity and high selectivity under certain temperature and pressure. The reaction temperature is usually 120-200℃, the pressure is 3-8MPa, and the reaction time is 2-12h. More specifically, when the amine compound is 1,3-cyclohexanedimethylamine, the specific hydrogenation process can be as described in CN113666830A, and the specific preparation method is also described in the following examples.

[0039] According to the scheme of the present application, when the amine raw material is characterized by ultraviolet spectrophotometry, anhydrous ethanol is used as a blank sample, and the maximum absorption wavelength of the amine compound in 0.1wt% ethanol solution can be determined by full wavelength scanning. In specific embodiments, the maximum absorption wavelength can be 203nm.

[0040] According to the specific embodiments of the present application, when the amine compound as a raw material has an absorbance ≤2.0 at the maximum absorption wavelength in 0.1wt% ethanol solution, the color performance of the isocyanate prepared by phosgenation can be further improved.

[0041] Further, in order to make the amine compound meet the absorbance requirement of the above ultraviolet spectrophotometry characterization, the method further includes the process of epoxidation treatment and purification of the amine compound.

[0042] The present application discloses a method for improving the quality of amine raw materials by epoxidation treatment. The amine raw materials are reacted with an epoxidation reagent to oxidize the unsaturated hydrocarbons in the amine compounds into epoxides. The epoxidation reagent is unstable and decomposes at high temperatures, so the epoxidation reaction conditions should be controlled to be relatively mild, usually at 0-40°C, such as 0°C, 5°C, 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, or 40°C. The ambient temperature or room temperature, i.e. about 10-25°C, can meet the requirements. For example, in some specific embodiments, the epoxidation treatment is carried out as follows: the amine compounds prepared by hydrogenation reaction are reacted with an epoxidation reagent at 0-40°C to oxidize the unsaturated hydrocarbons into epoxides.

[0043] The type of epoxidation reagent is not particularly limited, and can be selected from peroxobutane ketone, sodium hypochlorite, or high-valence iodine reagent, which can be prepared or purchased. The amount of the epoxidation reagent added is usually excessive to ensure that the unsaturated hydrocarbons can be completely oxidized. For example, according to the content range of the unsaturated hydrocarbon impurities obtained by the hydrogenation process in the following examples, the amount of the epoxidation reagent added is usually 0.1-0.5% of the mass of the amine raw materials. The amine raw materials after epoxidation treatment need to be purified before being used to prepare isocyanate. That is, the purification of the amine compounds after epoxidation treatment generally includes the removal of the epoxidation reagent (unreacted), epoxides, and solvents. In actual operation, the excess epoxidation reagent can be removed by conventional thermal decomposition or distillation. The amine raw materials used in actual production usually need to be pretreated to further remove the possible solvents. Generally, distillation is performed first to remove the solvents, so the epoxides generated after epoxidation treatment and the residual epoxidation reagent can also be removed together in the solvent removal step. When the amine compound is an alicyclic amine, the epoxidation reagent and the oxidized epoxide and other impurities such as solvents can be removed simultaneously by distillation.

[0044] The amine compounds as raw materials can be prepared into isocyanate by a liquid-phase phosgeneization method or a non-liquid-phase phosgeneization method. In the present application, either a gas-phase phosgeneization reaction or a liquid-phase phosgeneization reaction can be used. The phosgeneization reaction conditions can be operated using conventional conditions, such as the method described in CN103319372 A.

[0045] It can be understood that, in order to ensure the purity of the obtained isocyanate, a step of separating and purifying the isocyanate prepared by the phosgenation reaction is usually further included, the separation and purification method can adopt the known method, and generally includes the steps of removing hydrogen chloride, phosgene, removing solvent to obtain a crude product, and separating and purifying the crude product to obtain a pure isocyanate, for example, the method described in the published patents CN101302174A and CN102224133A can be referred to, and details are not described herein.

[0046] As described above, the isocyanate prepared by the method of the present application can have a lower color value, and when represented by a platinum-cobalt color number, can stably achieve an effect of not higher than 10, and has the advantages of not being prone to yellowing and stable performance. When the isocyanate is further applied to the preparation of polymeric isocyanate, polyurethane, polyurea and spandex material, the prepared downstream product can have excellent discoloration resistance.

[0047] The present application also provides a quality control method for an amine compound raw material for preparing light-colored isocyanate, which is characterized by ultraviolet spectrophotometry, with anhydrous ethanol as a blank sample, and the amine compound raw material satisfies absorbance ≤2.5 at the maximum absorption wavelength in a 0.1wt% ethanol solution. The quality control method of the present application is more conducive to controlling the quality of the raw material, and the detection operation is convenient and practical.

[0048] The present application also provides a light-colored isocyanate, which has a platinum-cobalt color number not higher than 10 initially, and a platinum-cobalt color number not higher than 35 after being placed in an environment of 60°C for 24h. As described above, the light-colored isocyanate product provided by the present application has light color and is not prone to yellowing, and as a raw material, can ensure that the prepared downstream product has excellent discoloration resistance.

[0049] The light-colored isocyanate product of the present application can be prepared by the above method.

[0050] The present application also provides a preparation method of polyurethane, which specifically comprises: first preparing the isocyanate by the above method, and then reacting the isocyanate with a polyol to obtain the polyurethane.

[0051] In the preparation process of the polyurethane, the polyol compound used is not particularly limited, and as specific examples of the polyol compound, the polyol can be selected from any one or a combination of at least two of polymers containing active hydrogen, such as: terminal amino polypropylene glycol, terminal hydroxyl polytetrahydrofuran, terminal hydroxyl polypropylene glycol, polyethylene glycol, polypropylene glycol, polytetrahydrofuran diol, polycaprolactone diol, polylactic acid diol, polyethylene glycol adipate diol, polybutylene glycol adipate diol, polybutadiene diol, 2,2-dimethylol propionic acid and N-methyl diethanolamine. Preferably, the polyurethane is prepared from terminal amino polypropylene glycol and / or terminal hydroxyl polypropylene glycol.

[0052] The process for preparing polyurethane resin by using the polymerization reaction of isocyanate and polyol compound is well known in the art, and is not the focus of the present application, and thus will not be described in detail. The preparation process mainly includes stirring and mixing the components in the raw material composition, then degassing and curing to obtain the product. Specifically, the isocyanate, polyol compound and other additives as needed are mixed, the mixture is degassed, then injected into the injection mold, and usually slowly heated from low temperature to high temperature, for example, from room temperature, to make it polymerize and cure to obtain the product. The molar ratio of NCO group / OH group is usually controlled in the range of 0.8-1.5, preferably in the range of 0.9-1.1.

[0053] In the raw material composition for preparing polyurethane resin, a polymerization catalyst can be added to obtain the desired reaction speed. The catalyst is, for example, dibutyltin dichloride, and the optional amount can be, for example, 0.01 to 5.0% by weight, preferably 0.01 to 3% by weight (based on the total weight of isocyanate and polyol compound required for preparing polyurethane resin), calculated based on the total amount of catalyst used. The catalyst is specifically, for example, an organotin compound, specifically a dialkyltin halide such as dibutyltin dichloride, dimethyltin dichloride, etc.; a dialkyltin dicarboxylate such as dimethyltin diacetate, dibutyltin dioctate, dibutyltin dilaurate, etc.

[0054] In addition, according to the purpose and need, one or a combination of two or more of various auxiliary substances such as chain extender, crosslinking agent, light stabilizer, ultraviolet absorber, antioxidant, dye, filler, release agent, etc. can be added during the preparation process. The specific selection principles and operations can be carried out according to the known and conventional means, for example, the amount of each auxiliary agent can be, for example, 0.05 to 3.0% by weight, preferably 0.05 to 1% by weight (based on the total weight of isocyanate and polyol compound required for preparing polyurethane resin).

[0055] The present application will be described in detail below with specific embodiments. Specifically, 4,4'-dicyclohexylmethane diisocyanate (HMDI), cyclohexyl dimethylene diisocyanate (HXDI), and cyclohexane diisocyanate (CHDI) are taken as examples. In each embodiment,

[0056] The following instruments were used for the experiment: JJ100B electronic analytical balance (American Sartorius), HH-2 constant temperature water bath (Changzhou Guohua Electrical Appliance Co., Ltd.), UV-5600 ultraviolet spectrophotometer (wavelength range 190-1100 nm), and Huo Pu Biotechnology.

[0057] The test method is as follows:

[0058] Blank test: The anhydrous ethanol was used as a blank reagent, placed in a cuvette, and scanned in the full wave band (200-1000 nm). The wavelength was taken as the abscissa, and the absorbance was taken as the ordinate to draw a scanning curve.

[0059] Sample detection: The sample was accurately weighed, placed in a conical flask, and added with anhydrous ethanol for ultrasonic dissolution for 1 min. After standing for 5 min, the final volume was made to 250 mL with ethanol to prepare a 0.1 wt% ethanol solution. The sample was detected by ultraviolet spectrophotometry according to the conditions determined by the standard sample. The liquid was transferred into a cuvette, and scanned in the full wave band (190-1100 nm). The maximum absorption wavelength was determined to be 203 nm, and the corresponding absorbance was measured. According to the scanning curve, the absorbance of the sample at this wavelength was obtained by subtracting the absorbance of the blank sample ethanol at this wavelength.

[0060] Product color number analysis: The color number of the target isocyanate product was determined by GB / T 3143-1982.

[0061] Discoloration resistance performance test: 500 g of isocyanate product was taken in a sample bottle and placed in a 60°C environment for 24 h before testing the color number.

[0062] The amine raw materials used in the following examples were obtained from hydrotreated products, which can be obtained by operating according to conventional hydrogenation methods in the art.

[0063] The following is a detailed description of 1,3-cyclohexanedimethylamine as an example, and the hydrotreatment in other examples and comparative examples can be performed with reference to the treatment.

[0064] A fixed bed reactor was used to convert m-xylylenediamine into 1,3-BAC (full name: 1,3-cyclohexanedimethylamine, abbreviated as HXDA) by two hydrogenation reactions.

[0065] During the hydrogenation reaction, the hydrogen / benzene ratio was controlled at (6.0-9.0):1. The m-xylylenediamine and the additive isopropyl alcohol were pumped into a bubble mixer using a liquid feed pump, and hydrogen was introduced through a pipeline at the same time. The hydrogen, m-xylylenediamine, and additive isopropyl alcohol were uniformly mixed by the bubble mixer, and then entered the reaction tube filled with hydrogenation catalyst. In the reaction tube, the catalyst palladium carbon was loaded at a mass ratio of 7.8-8.2% of m-xylylenediamine, and the cocatalyst sodium nitrate was loaded at a mass ratio of 0.9-1.1% of m-xylylenediamine. The reaction pressure was controlled at 7.0-7.2 MPa, the reaction temperature was raised to 125-130 degrees, the reaction time was 120±5 minutes, the liquid from the reaction tube was collected into a sample tank for cooling, and finally flowed into a sample storage tank, which could be sampled at any time for detection.

[0066] The conversion rate of m-xylylenediamine at the reactor outlet after the first hydrogenation is 70-85%, and the conversion rate of m-xylylenediamine at the reactor outlet after the second hydrogenation is 85-99%. After the reaction is completed, the hydrogen in the pipeline is emptied by opening the nitrogen delivery pipeline. The hydrogenation catalyst used is filtered, dried, or regenerated for continued circulation.

[0067] The collected hydrogenation product HXDA is characterized by ultraviolet spectrophotometry to determine the absorbance A at an ultraviolet wavelength of 203 nm.

[0068] Example 1

[0069] In this example, 1,3-cyclohexanedimethylamine (HXDA) obtained after hydrogenation of m-xylylenediamine is used as the raw material to prepare cyclohexyl dimethylene diisocyanate (HXDI) through a phosgenation reaction. The method is as follows:

[0070] After the hydrogenation reaction, the HXDA raw material liquid (containing isopropyl alcohol solvent) enters the epoxidation reactor, and the room temperature (about 20°C) is maintained. 0.2wt% of butanone peroxide is added and reacted for 2h, and then sent to the isopropyl alcohol solvent removal process. The solvent removal conditions are: vacuum 22Kpa, temperature 50 degrees. Unreacted butanone peroxide is removed with the solvent in this process. After the solvent is removed, it is sent to the HXDA refining tower. The distillation conditions are: temperature 172-175 degrees, vacuum 1.0KPa, and HXDA product is obtained. Through absorbance detection, the A value is 2.3, which meets the requirements and can be used for the next step of isocyanate preparation by phosgenation.

[0071] Gas phase phosgenation reaction of 1,3-cyclohexanedimethylamine with phosgene. The phosgenation reaction conditions are as follows: before phosgenation reaction, the raw material is preheated to 350-360°C, 1,3-cyclohexanedimethylamine vapor is controlled with inert gas nitrogen, the molar ratio of phosgene to 1,3-cyclohexanedimethylamine is (5-6):1, the reaction temperature is 230-240°C, the reaction pressure is 0.1MPa absolute pressure, and the reaction product is absorbed by chlorobenzene. After the reaction is completed, the obtained isocyanate reaction liquid is further removed of hydrogen chloride, phosgene and solvent to obtain crude isocyanate. The crude product is further recrystallized to obtain pure isocyanate, which is subjected to color number detection.

[0072] The obtained pure isocyanate is further reacted with polyether polyol with a hydroxyl value of 105-112mg KOH / g to obtain a color-stable polyurethane product.

[0073] Example 2

[0074] In this example, 4,4'-diaminocyclohexylmethane (HMDA) obtained after hydrogenation of diaminodiphenylmethane (MDA) is used as the raw material to prepare 4,4'-dicyclohexylmethane diisocyanate (HMDI) through a phosgenation reaction. The method is as follows:

[0075] The hydrogenated HMDA raw solution (containing tetrahydrofuran solvent) is fed into an epoxidation reactor, room temperature (about 20°C) is maintained, 0.2wt% of peroxide acetone is added and reacted for 2h, and then fed into a tetrahydrofuran solvent removal process. The solvent conditions are: vacuum 40Kpa, temperature 40°C to remove tetrahydrofuran, and unreacted peroxide acetone is removed with the solvent. After the solvent is removed, the amine refining tower is fed in, the distillation conditions are: temperature 160-165°C, vacuum 0.5KPa, and HMDA product is obtained. The A value is 1.9 by absorbance detection, which meets the requirements and can be used for the next step of preparing isocyanate by phosgenation.

[0076] HMDA is subjected to liquid phase phosgenation reaction with phosgene in chlorobenzene solvent. The liquid phase phosgenation reaction conditions are as follows: HMDA is configured into a 15% solution with chlorobenzene as the solvent and preheated to 40°C, and simultaneously fed into a reactor containing chlorobenzene with liquid phosgene at -5°C to perform liquid phase phosgenation reaction, wherein the feeding amount of HMDA is 100Kg / h, the feeding amount of cold reaction phosgene is 1000kg / h, the cold reaction temperature is controlled at 60°C, the residence time is 5min, the hot reaction temperature is controlled at 140°C, the residence time is 2h, phosgenated liquid is obtained, and after further removal of hydrogen chloride, phosgene and solvent, crude isocyanate is obtained. The crude product is further recrystallized to obtain pure isocyanate, and color number detection is performed thereon.

[0077] The obtained pure isocyanate is further reacted with polyether polyol with a hydroxyl value of 105-112mg KOH / g to obtain color-stable polyurethane products.

[0078] Example 3

[0079] In this example, 1,4-cyclohexanediamine (CHDA) obtained by hydrogenation treatment of 1,4-phenylenediamine (PPDA) is used as raw material to prepare cyclohexane diisocyanate (CHDI) by phosgenation reaction, and the method is as follows:

[0080] The hydrogenated 1,4-cyclohexanediamine (CHDA) tetrahydrofuran solution is fed into an epoxidation reactor, room temperature (about 20°C) is maintained, 0.2wt% of peroxide methyl ethyl ketone is added and reacted for 2h, and then fed into a tetrahydrofuran solvent removal process. The solvent removal conditions are: vacuum 40Kpa, temperature 40°C. After the solvent is removed, the CHDA refining tower is fed in, the distillation conditions are: temperature 90-92°C, vacuum 3KPa, and unreacted peroxide methyl ethyl ketone is removed with the light components in the tower to obtain CHDA product. The A value is 2.5 by absorbance detection, which meets the requirements and can be used for the next step of preparing isocyanate by phosgenation.

[0081] The CHDA is subjected to liquid phase phosgenation reaction with phosgene in chlorobenzene solvent. The liquid phase phosgenation reaction conditions are as follows: the CHDA is configured into a 10% solution with chlorobenzene as solvent and preheated to 40°C, and is simultaneously introduced into a reaction kettle containing chlorobenzene with liquid phosgene at -5°C to carry out liquid phase phosgenation reaction, wherein the feeding amount of CHDA is 100 Kg / h, the feeding amount of cold reaction phosgene is 600 kg / h, the cold reaction temperature is controlled at 60°C, the residence time is 5 min, the hot reaction temperature is controlled at 140°C, and the residence time is 2 h, to obtain a phosgenation liquid, and further removal of hydrogen chloride, phosgene and solvent to obtain a crude isocyanate product, which is further recrystallized to obtain pure isocyanate, and color number detection is carried out.

[0082] The obtained pure isocyanate is further reacted with a polyether polyol having a hydroxyl value of 105-112 mg KOH / g to obtain a color-stable polyurethane product.

[0083] Example 4

[0084] In this example, 1,4-cyclohexanediamine (CHDA) obtained by hydrogenation of 1,4-phenylenediamine (PPDA) is used as raw material to prepare cyclohexane diisocyanate (CHDI) by phosgenation reaction, and the method is as follows:

[0085] The tetrahydrofuran solution of the hydrogenated 1,4-cyclohexanediamine (CHDA) is directly sent to the tetrahydrofuran solvent removal process. The desolvent conditions are: vacuum 40 Kpa, temperature 40 degrees. After the desolvent is removed, it is sent to the CHDA refining tower, and the distillation conditions are: temperature 90-92 degrees, vacuum 3 KPa, and the CHDA crude product is obtained in the tower, which is detected by absorbance, and the A value is 3.0; the CHDA crude product is subjected to secondary refining under the same refining conditions, and the CHDA product is obtained in the tower, which is detected by absorbance, and the A value is 2.5, which meets the requirements and can be used for the next step of phosgenation to prepare isocyanate.

[0086] The CHDA is subjected to liquid phase phosgenation reaction with phosgene in chlorobenzene solvent. The liquid phase phosgenation reaction conditions are as follows: the CHDA is configured into a 10% solution with chlorobenzene as solvent and preheated to 40°C, and is simultaneously introduced into a reaction kettle containing chlorobenzene with liquid phosgene at -5°C to carry out liquid phase phosgenation reaction, wherein the feeding amount of CHDA is 100 Kg / h, the feeding amount of cold reaction phosgene is 600 kg / h, the cold reaction temperature is controlled at 60°C, the residence time is 5 min, the hot reaction temperature is controlled at 140°C, and the residence time is 2 h, to obtain a phosgenation liquid, and further removal of hydrogen chloride, phosgene and solvent to obtain a crude isocyanate product, which is further recrystallized to obtain pure isocyanate, and color number detection is carried out.

[0087] The obtained pure isocyanate is further reacted with a polyether polyol having a hydroxyl value of 105-112 mg KOH / g, to obtain a color-stable polyurethane product.

[0088] Comparative Example 1

[0089] This comparative example provides an isocyanate, a polyurethane product and a preparation method thereof, which is different from Example 1 in that the filtrate is directly subjected to the next step of distillation to remove isopropanol solvent without epoxidation treatment.

[0090] The preparation of the polyurethane product is as in Example 1.

[0091] Comparative Example 2

[0092] This comparative example provides an isocyanate, a polyurethane product and a preparation method thereof, which is different from Example 2 in that the reaction solution after hydrogenation is directly subjected to the next step of distillation to remove tetrahydrofuran solvent without epoxidation treatment.

[0093] The preparation of the polyurethane product is as in Example 1.

[0094] Comparative Example 3

[0095] This comparative example provides an isocyanate, a polyurethane product and a preparation method thereof, which is different from Example 3 in that the reaction solution after hydrogenation is directly subjected to the next step of distillation to remove tetrahydrofuran solvent without epoxidation treatment.

[0096] The preparation of the polyurethane product is as in Example 1.

[0097] Performance test:

[0098] The evaluation results of the amine compounds and isocyanates prepared in each of the above examples and comparative examples are shown in Table 1 below:

[0099] Table 1

[0100]

[0101]

[0102] From the above results, it can be seen that by controlling the absorbance of the isocyanate raw material (amine compound) to be ≤2.5, an isocyanate product with an initial platinum-cobalt color number of not higher than 10 can be obtained, and the platinum-cobalt color number of the isocyanate after being placed in an environment of 60°C for 24 h is not higher than 35, and the yellowing rate is significantly lower than that of the control group with a higher absorbance of the raw material.

[0103] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit the present application; although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions recorded in the above embodiments can be modified, or some or all of the technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for preparing light-colored isocyanate, characterized in that, the method comprises a process of preparing isocyanate by phosgenation reaction with an amine compound as raw material; wherein, the amine compound raw material used is prepared by hydrogenation reaction, and satisfies the UV spectrophotometry characterization that, with anhydrous ethanol as a blank sample, in a 0.1wt% ethanol solution, the absorbance at the maximum absorption wavelength is ≤2.

5.

2. The method according to claim 1, further comprising a process of epoxy treatment and purification of the amine compound raw material, so as to satisfy the absorbance of the UV spectrophotometry characterization.

3. The method according to claim 1 or 2, wherein the amine compound raw material is alicyclic amine.

4. The method according to any one of claims 1-3, wherein the maximum absorption wavelength is 203nm, and / or, the absorbance of the amine compound satisfies ≤2.

0.

2. The method of claim 1, wherein 5. The method according to any one of claims 1-4, wherein the method of epoxy treatment comprises: reacting the amine compound raw material with an epoxy reagent, and at least oxidizing unsaturated hydrocarbon compounds in the amine compound raw material into epoxy compounds; and / or 3. The method according to any of claims 1-2, characterized in that, 6. The method according to claim 5, wherein the temperature of the epoxy treatment is 0-40℃.

7. The method according to claim 5 or 6, wherein the epoxy reagent is butanone peroxide, sodium hypochlorite or high-valence iodine reagent.

4. The method of claim 1, wherein, 8. The method according to any one of claims 1-7, further comprising a step of purifying and separating the isocyanate prepared by the phosgenation reaction.

9. The method according to any one of claims 1-8, wherein the UV spectrophotometry characterization is performed with anhydrous ethanol as a blank sample, in a 0.1wt% ethanol solution, the absorbance at the maximum absorption wavelength of the amine compound raw material prepared by hydrogenation reaction satisfies ≤2.

5.

5. The method of claim 4, wherein, 10. The method according to any one of claims 1-9, further comprising a step of polymerizing the isocyanate with a polyol after the isocyanate is prepared by the method according to any one of claims 1-6.

6. The method of claim 1 or 2, wherein, ​ 7. A method for quality control of raw material amine compounds for producing light-colored isocyanates, characterized by, ​ 8. A process for the preparation of a polyurethane, characterized in that, ​

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