Method for preparing light-color isocyanate and polyurethane

Abstract

The invention relates to the technical field of preparation of isocyanate, in particular to a method for preparing light-color isocyanate and polyurethane. The method comprises the following steps: taking an amine compound as a raw material, and preparing isocyanate through phosgenation reaction; wherein the used amine compound raw material is prepared by hydrogenation reaction, and when the amine compound raw material is characterized by ultraviolet spectrophotometry, the requirement that absolute ethyl alcohol is used as a blank sample, and the absorbance is smaller than or equal to 2.5 under the maximum absorption wavelength in a 0.1 wt% ethanol solution is met. According to the method, the raw materials are characterized through the ultraviolet spectrophotometry, the method can be suitable for preparation of all isocyanates with amine compounds prepared through hydrogenation reaction as the raw materials, the universality is good, operation is easy and rapid, the cost is low, the characterization result is stable, and the prepared isocyanate has the characteristic of being light in color or colorless.

Description

Technical Field

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

[0002] As an intermediate in organic synthesis, isocyanate is widely used in various industries such as industry, agriculture, construction, automobile, and thermal insulation because it can be further synthesized into polymerized isocyanate, polyurethane, polyurea, spandex, and other materials. The mainstream method for synthesizing isocyanate in the industry is phosgenation, but 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 problem of high color value and poor color change resistance.

[0003] In order to solve the impact of isocyanate color value on downstream products, treating the material after the phosgenation reaction to improve the color of the isocyanate product was once considered an effective solution. However, many of the coloring substances in isocyanates come from the raw material components (some also come from the reaction results of trace components in the raw materials), and the by-products generated during the phosgenation reaction will also cause the product to be colored. Color treatment at the stage after the phosgenation reaction requires a lot of engineering costs and does not significantly improve the color number. In addition, the color treatment method at the stage after the phosgenation reaction will mostly introduce other impurities, which will form undesirable by-products in the downstream applications of isocyanates.

[0004] Therefore, with the development of technology, it has become a more accepted practice to treat or purify the starting raw material amine substances or their oligomers before the phosgenation reaction, and there are many technical disclosures at present.

[0005] For example, patent application publication No. EP0546398A discloses that polymethylene polyphenylene polyamine is subjected to acidification treatment before phosgenation to produce isocyanate products with low color.

[0006] Patent application publication number EP0446781A discloses a process in which polymeric MDA (monomers and oligomeric polymethylene polyphenylene polyamines) is first treated with hydrogen and then phosgenated to obtain a lighter-colored MDI.

[0007] Patent application with publication number CN103319372 A discloses a method for preparing light-colored or colorless dicyclohexylmethane diisocyanate (HMDI) by controlling the content of alcohol compounds in the raw material dicyclohexylmethane diamine to less than 0.2% and then subjecting it to 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 a mixture thereof in phosgene to be less than 25 ppm, and then reacting a diphenylmethanediamine series amine or a mixture of a plurality of these amines with the phosgene to undergo a phosgenation reaction.

[0009] It can be seen that in the prior art including the above disclosure, in order to solve the low color value of the isocyanate product and the impact on the downstream products, the impurity content in the specific amine substance of the starting raw material is used as the purity standard, but the universality is limited and cannot be applied in the preparation of other isocyanates; on the other hand, in order to determine the purity of the raw material, it is necessary to introduce a specific detection and analysis method according to the preset treatment object, which is not only complicated and expensive, but also has many interference factors that affect the sensitivity and accuracy of the results. Therefore, the art urgently needs to provide a method that can determine the purity of the raw material amine by a fast and simple characterization method, thereby making it easier to prepare light-colored isocyanates on the production line. Summary of the invention

[0010] The invention provides a method for preparing light-colored isocyanate. The method characterizes a raw material amine compound by ultraviolet spectrophotometry, determines that an amine compound that meets the requirements is used as a raw material for preparation, and is conducive to the prepared isocyanate being light-colored or colorless. The characterization method of the raw material is simple, rapid and stable, and can achieve raw material quality control and low-cost production of target products.

[0011] The present invention also provides a quality control method for raw material amine compounds for preparing light-colored isocyanates, and the detection operation is convenient and practical.

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

[0013] The invention also provides a polyurethane having excellent anti-discoloration performance.

[0014] The present invention achieves the above technical objectives through the following technical solutions:

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

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

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

[0018] According to the above-mentioned preparation method, the maximum absorption wavelength is 203 nm, and / or the amine compound satisfies an absorbance of ≤2.0.

[0019] The preparation method described above also includes a process of epoxidizing and purifying the amine compound raw material so that it meets the absorbance characterized by the ultraviolet spectrophotometry.

[0020] According to the preparation method described above, the epoxidation treatment method includes: reacting the amine compound raw material with an epoxidation reagent to at least oxidize the unsaturated hydrocarbon compound in the amine compound raw material into an epoxy compound; and / or the epoxidation treatment temperature is 0-40°C.

[0021] According to the above-mentioned preparation method, the epoxidation reagent is butanone peroxide, sodium hypochlorite or a high-valent iodine reagent.

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

[0023] The present invention also provides a quality control method for raw material amine compounds for preparing light-colored isocyanates, specifically: using ultraviolet spectrophotometry for characterization, using anhydrous ethanol as a blank sample, at the maximum absorption wavelength in a 0.1wt% ethanol solution, the raw material amine compound is prepared by hydrogenation reaction and satisfies an absorbance of ≤2.5.

[0024] The present invention also provides a light-colored isocyanate, wherein the initial platinum-cobalt color number of the isocyanate is not higher than 10, and the platinum-cobalt color number is not higher than 35 after being placed in an environment of 60° C. for 24 hours; and / or the isocyanate is prepared by the above method.

[0025] The present invention also provides a method for preparing polyurethane, comprising preparing isocyanate by the above method, and then polymerizing the isocyanate with polyol.

[0026] The method for preparing light-colored isocyanate provided by the present invention characterizes the raw material amine compound by ultraviolet spectrophotometry, and can be applied to the preparation of all isocyanates using amine compounds obtained by hydrogenation reaction as raw materials, has good universality, simple and fast operation, low cost and stable characterization results, thereby ensuring that the prepared isocyanate has a stable low color value. According to the method of the present invention, the prepared isocyanate platinum cobalt color number can reach no more than 10 and is not easy to yellow.

[0027] The quality control method of the raw material amine compound for preparing light-colored isocyanate provided by the present invention has convenient and practical detection operation and is more conducive to the control of the raw material quality.

[0028] The polyurethane provided by the present invention has excellent color change resistance. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] Based on the problem that the existing preparation methods of light-colored isocyanates are not universal and complicated to operate, the present invention provides a method for preparing light-colored isocyanates, comprising the process of first characterizing the amine compound used by ultraviolet spectrophotometry to determine whether it meets the requirements, and then preparing the isocyanate by phosgenation reaction; wherein,

[0031] The amine compound raw material used is prepared by hydrogenation reaction, and when characterized by ultraviolet spectrophotometry, it meets the following conditions: taking anhydrous ethanol as a blank sample, the absorbance is ≤2.5 at the maximum absorption wavelength in a 0.1wt% ethanol solution.

[0032] The present invention characterizes amine compounds by ultraviolet spectrophotometry, thereby determining that amine compounds that meet the standards are used as raw materials to prepare isocyanates through phosgenation reaction. The method is applicable to the preparation of all isocyanates using amine compounds prepared by hydrogenation reaction as raw materials, and the prepared isocyanate products have stable low color value quality. According to the method of the present invention, the color value of the prepared isocyanate, characterized by platinum cobalt color number, may not be higher than 10.

[0033] According to the present invention, ultraviolet spectrophotometry is used to characterize and screen raw materials, targeting all amine compounds prepared by hydrogenation reactions, that is, it has good universality and has the advantages of cheap analytical instruments, simple sample processing, simple operation, fast response, high sensitivity, low background signal, low cost, and is conducive to large-scale application.

[0034] This method is applicable to amine compounds prepared by hydrogenation reaction. This is because in the process of preparing amine compounds by hydrogenation reaction, when there is incomplete hydrogenation and side reactions, the impurities in the raw materials may be mostly unsaturated hydrocarbons. These impurities are difficult to separate during the distillation and purification of amine compounds, and they contain C=C unsaturated bonds, which can be easily detected and controlled by ultraviolet spectrophotometry.

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

[0036] Wherein, R is selected from one or more of amino, methyleneamine, methylenecyclohexylamine, hydrogen, methyl, ethyl, n-propyl, isopropyl, ester group, tert-butyl, and halogen.

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

[0038] The amine compounds prepared by hydrogenation reaction described in the present invention refer to the products obtained by subjecting unsaturated amines to one, two or even multiple hydrogenation reactions by the conventional hydrogenation preparation method. For example, when the amine compound is alicyclic amine, the preparation of alicyclic amine can be carried out in the following manner: using a catalyst and a co-catalyst, at a certain temperature and pressure, aromatic amine and hydrogen are converted into alicyclic amines with high activity and high selectivity. The reaction temperature is usually 120-200°C, the pressure is 3-8MPa, and the reaction time is 2-12h. More specifically, when the amine compound is 1,3-cyclohexanedimethylamine, its specific hydrogenation process can be as described in CN113666830A, and the following examples also describe the specific preparation method.

[0039] According to the scheme of the present invention, 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 a 0.1wt% ethanol solution can be determined by full wavelength scanning. In a specific embodiment, the maximum absorption wavelength can be 203nm.

[0040] According to a specific embodiment of the present invention, taking anhydrous ethanol as a blank sample, when the absorbance of the amine compound as a raw material at the maximum absorption wavelength in a 0.1wt% ethanol solution is ≤2.0, the color properties of the isocyanate prepared by phosgenation can be further improved.

[0041] Furthermore, in order to make the amine compound meet the absorbance requirement characterized by the above-mentioned ultraviolet spectrophotometry, the method also includes a process of epoxidizing and purifying the amine compound.

[0042] The present invention has found that the quality of amine raw materials (characterized by the absorbance) can be improved by epoxidation treatment, specifically, the amine compound raw material is reacted with an epoxidation reagent, and at least the unsaturated hydrocarbon compound in the amine compound is oxidized to an epoxide compound. The stability of the epoxidation reagent is poor and it is easy to decompose at high temperature. Therefore, the conditions of the epoxidation reaction should generally be controlled to be relatively mild, and the reaction is usually selected under 0-40°C, for example, 0°C, 5°C, 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, and it can be regulated according to the specific conditions of the raw materials, processing facilities and environment. The usual ambient temperature or room temperature can meet the requirements, that is, about 10-25°C. For example, in some specific embodiments, the method of epoxidation treatment is as follows: at 0-40°C, the amine compound prepared by hydrogenation reaction is reacted with an epoxidation reagent to oxidize the unsaturated hydrocarbon compound to an epoxide compound.

[0043] The types of epoxidation reagents are generally not limited, such as butanone peroxide, sodium hypochlorite or high-valent iodine reagents, etc., which can be prepared by themselves or purchased commercially. The amount of epoxidation reagent added is generally excessive to ensure that the unsaturated hydrocarbons can be completely oxidized. For example, according to the range of unsaturated hydrocarbon impurity content obtained by the hydrogenation process in the following embodiment, the amount of epoxidation reagent added is usually 0.1-0.5% of the mass of the amine compound raw material to meet the requirements. The amine raw materials after epoxidation need to be purified before being used to prepare isocyanates. That is, the purification of amine compounds after epoxidation generally includes the removal of epoxidation reagents (unreacted), epoxides and solvents. In actual operation, the excess epoxidation reagents can be achieved by conventional thermal decomposition or distillation. The amine raw materials used in actual production usually need to be pretreated to further remove possible or residual solvents. Generally, distillation is performed to remove the solvent first, so the epoxides generated after epoxidation and the residual epoxidation reagents can also be removed together in the solvent removal link. For example, when the amine compound is an alicyclic amine, the epoxidation reagent, the oxidized epoxy compound, and impurities such as the solvent can be removed simultaneously by distillation.

[0044] There are two methods for preparing isocyanates by phosgenation using amine compounds as raw materials: liquid phase phosgenation and non-liquid phase phosgenation. In the present invention, both gas phase phosgenation and liquid phase phosgenation can be used. The conditions for the phosgenation reaction can be operated under conventional conditions, such as the method described in Publication No. CN103319372 A.

[0045] It is understandable that in order to ensure the purity of the obtained isocyanate, the step of separating and purifying the isocyanate prepared by the phosgenation reaction is usually further included. The separation and purification method can adopt an existing known method, which usually includes removing hydrogen chloride, phosgene, and solvent to obtain a crude product, and separating the crude product to obtain pure isocyanate. For example, the method described in the published patents CN101302174A and CN102224133A can be referred to, and will not be described in detail here.

[0046] As mentioned above, the isocyanate prepared by the method of the present invention can have a lower color value, and when characterized by a platinum cobalt color number, it can stably achieve an effect of no more than 10, and also has the advantages of not being easy to yellow and having stable performance. It is further applied to the preparation of polymerized isocyanate, polyurethane, polyurea, and spandex materials, and can ensure that the prepared downstream products have excellent color resistance.

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

[0048] The present invention also provides a light-colored isocyanate, the initial platinum-cobalt color number of the isocyanate is not higher than 10, and after being placed in a 60°C environment for 24 hours, the platinum-cobalt color number is not higher than 35. As mentioned above, the light-colored isocyanate product provided by the present invention has a light color and is not easy to yellow. As a raw material, it is more conducive to ensuring that the prepared downstream products have excellent discoloration resistance.

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

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

[0051] In the process of preparing polyurethane, the polyol compound used is not particularly limited. As a specific example of the polyol compound, the polyol can be selected from polymers containing active hydrogen, for example, selected from amino-terminated polypropylene glycol, hydroxyl-terminated polytetrahydrofuran, hydroxyl-terminated polypropylene glycol, polyethylene glycol, polypropylene glycol, polytetrahydrofuran diol, polycaprolactone diol, polylactic acid diol, polyethylene adipate glycol ester diol, polybutylene adipate glycol ester diol, polybutadiene diol, 2,2-dimethylol propionic acid, and any one or a combination of at least two of N-methyldiethanolamine, preferably amino-terminated polypropylene glycol and / or hydroxyl-terminated polypropylene glycol.

[0052] The process of preparing polyurethane resin by polymerization reaction of isocyanate and polyol compound is well known in the art, which is a known technology in the art and is not the focus of the present invention, so it will not be described one by one. Its preparation process mainly includes stirring and mixing the components in the raw material composition, then degassing and obtaining it after a curing process. Specifically, isocyanate, polyol compound and other additives added as needed are mixed, and the mixed solution is degassed and injected into an injection mold, which is usually slowly heated from a low temperature to a high temperature, for example, by a room temperature program, so that it is polymerized and cured to obtain a product. It is usually necessary to control the molar ratio of NCO group / OH group to 0.8-1.5, preferably in the range of 0.9-1.1.

[0053] In order to obtain the desired reaction rate, a polymerization catalyst may be added to the raw material composition for preparing the polyurethane resin. The catalyst is, for example, dibutyltin dichloride. The optional amount used may be, for example, 0.01 to 5.0% by weight, preferably 0.01 to 3% by weight (based on the total weight of the isocyanate and polyol compounds required for preparing the polyurethane resin) calculated based on the total amount of the catalyst used. The catalyst is, for example, an organic tin compound, specifically, dialkyltin halides such as dibutyltin dichloride and dimethyltin dichloride; dialkyltin dicarboxylates such as dimethyltin diacetate, dibutyltin dioctoate, and dibutyltin dilaurate.

[0054] In addition, according to the purpose and needs, the preparation process can choose to add one or a combination of two or more of various auxiliary substances such as chain extenders, cross-linking agents, light stabilizers, ultraviolet absorbers, antioxidants, dyes, fillers, release agents, etc. The specific selection principles and operations are all in accordance with well-known and conventional means. For example, the addition 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 compounds required for the preparation of polyurethane resin).

[0055] The present invention is described in detail below in conjunction 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 analysis: JJ100B electronic analytical balance (Shuangjie Company, USA), HH-2 constant temperature water bath (Changzhou Guohua Electric Co., Ltd.), UV-5600 ultraviolet spectrophotometer (wavelength range 190-1100nm), Hepu Biotechnology.

[0057] The test method is as follows:

[0058] For the blank test, first use anhydrous ethanol as a blank reagent, place it in a cuvette, scan the entire band (200-1000nm), and draw a scanning curve with wavelength as the horizontal axis and absorbance as the vertical axis.

[0059] Sample detection: weigh the sample accurately, put it into a conical flask, add anhydrous ethanol and ultrasonically dissolve it for 1 minute, let it stand for 5 minutes, and finally use ethanol to make a volume of 250mL to prepare a 0.1wt% ethanol solution. Perform ultraviolet spectrophotometer detection according to the conditions determined by the standard sample, transfer the liquid into a cuvette, and scan the full band (190-1100nm). Determine the maximum absorption wavelength of 203nm, and measure the corresponding absorbance. According to the drawn scanning curve, the absorbance is subtracted from the absorbance of the blank sample ethanol at this wavelength, and the result is the absorbance A of the sample at this wavelength.

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

[0061] Color change resistance test: Take 500g of isocyanate product in a sample bottle, place it in a 60℃ environment for 24 hours, and then test the color number.

[0062] The amine raw materials used in the following examples are derived from hydrogenation products, which may be products obtained by conventional hydrogenation methods in the art.

[0063] The following is a detailed description using 1,3-cyclohexanedimethylamine as an example, and the hydrogenation treatments in other embodiments and comparative examples may be carried out with reference to this treatment.

[0064] Using a fixed bed reactor, m-xylylenediamine is converted into 1,3-BAC (full name: 1,3-cyclohexylenediamine, abbreviated as HXDA) by two hydrogenation steps.

[0065] During the hydrogenation reaction, the hydrogen-to-benzene ratio is controlled to be (6.0-9.0):1, and the meta-xylenediamine and the additive isopropanol are pumped into the bubble mixer by a liquid feed pump, and hydrogen is introduced through a pipeline at the same time. The hydrogen, meta-xylenediamine and the additive isopropanol are uniformly mixed with gas and liquid through the bubble mixer, and then enter the reaction tube filled with a hydrogenation catalyst, in which the catalyst palladium carbon is filled according to the mass ratio of meta-xylenediamine 7.8-8.2%, and the promoter sodium nitrate is filled according to the mass ratio of meta-xylenediamine 0.9-1.1%. The reaction pressure is controlled to be 7.0-7.2MPa, the reaction temperature is raised to 125-130 degrees, and the reaction is carried out for 120±5 minutes. The liquid coming out of the reaction tube is collected in a sample tank for cooling, and finally flows into a sample storage tank, and the sample storage tank can be sampled for detection at any time.

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

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

[0068] Example 1

[0069] In this embodiment, 1,3-cyclohexyldimethylamine (HXDA) obtained by hydrogenation of m-phenylenediamine is used as a raw material to prepare cyclohexyl dimethylene diisocyanate (HXDI) by phosgenation reaction, and the method is as follows:

[0070] The HXDA raw material liquid (containing isopropanol solvent) after hydrogenation reaction enters the epoxidation reaction kettle, maintains room temperature (about 20°C), adds 0.2wt% butanone peroxide to react for 2h, and then enters the distillation process to remove the isopropanol solvent. The desolventizing conditions are: vacuum 22Kpa, temperature 50 degrees. In this process, the unreacted butanone peroxide is removed with the solvent. After the solvent is removed, it is sent to the HXDA refining tower again. The distillation conditions are: temperature 172-175 degrees, vacuum 1.0KPa, and the 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 phosgenation to prepare isocyanate.

[0071] 1,3-cyclohexyldimethylamine and phosgene are subjected to gas phase phosgenation reaction. The phosgenation reaction conditions are as follows: before the phosgenation reaction, the raw materials are preheated to 350-360°C, the 1,3-cyclohexyldimethylamine vapor is treated with inert gas nitrogen, the molar ratio of phosgene to 1,3-cyclohexyldimethylamine is controlled to be (5-6):1, the reaction temperature is 230-240°C, the reaction pressure is an absolute pressure of 0.1MPa, and the reaction product is absorbed by chlorobenzene. After the reaction is completed, the obtained isocyanate reaction liquid is further freed of hydrogen chloride, phosgene, and solvent to obtain a crude isocyanate product, and 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 a polyether polyol having a hydroxyl value of 105-112 mg KOH / g to obtain a color-stable polyurethane product.

[0073] Example 2

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

[0075] The hydrogenated HMDA raw material liquid (containing tetrahydrofuran solvent) enters the epoxidation reactor, maintains room temperature (about 20°C), adds 0.2wt% peroxide acetone to react for 2h, and then enters the distillation process to remove the tetrahydrofuran solvent. The solvent conditions are: vacuum 40Kpa, temperature 40 degrees to remove tetrahydrofuran, and unreacted peroxide acetone is removed with the solvent. After removing the solvent, it is sent to the amine refining tower again. The distillation conditions are: temperature 160-165 degrees, vacuum 0.5KPa, and HMDA product is obtained. Through absorbance detection, the A value is 1.9, which meets the requirements and can be used for the next step of phosgenation to prepare isocyanate.

[0076] HMDA and phosgene are subjected to liquid-phase phosgenation reaction in chlorobenzene solvent. The liquid-phase phosgenation reaction conditions are as follows: HMDA is prepared into a 15% solution with chlorobenzene as solvent, and preheated to 40°C, and simultaneously introduced into a reactor containing chlorobenzene with liquid phosgene at -5°C for liquid-phase phosgenation reaction, wherein the feed amount of HMDA is 100Kg / h, the feed 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, and a photochemical liquid is obtained, and after further removing hydrogen chloride, phosgene, and solvent, a crude isocyanate is obtained, and the crude product is further recrystallized to obtain pure isocyanate, and a color number test is performed on it.

[0077] 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.

[0078] Example 3

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

[0080] The tetrahydrofuran solution of 1,4-cyclohexanediamine (CHDA) obtained by hydrogenation is added to the epoxidation reactor, maintained at room temperature (about 20°C), 0.2wt% methyl ethyl ketone peroxide is added to react for 2h, and then sent to the distillation process to remove the tetrahydrofuran solvent. Desolventization conditions: vacuum 40Kpa, temperature 40 degrees. After the solvent is removed, it is sent to the CHDA refining tower, and the distillation conditions are: temperature 90-92 degrees, vacuum 3KPa, and the unreacted methyl ethyl ketone peroxide is obtained in the light component extraction tower to obtain the CHDA product. Through absorbance detection, the A value is 2.5, which meets the requirements and can be used for the next step of phosgenation to prepare isocyanate.

[0081] The CHDA and phosgene are subjected to liquid phase phosgenation reaction in chlorobenzene solvent. The liquid phase phosgenation reaction conditions are as follows: CHDA is prepared into a 10% solution with chlorobenzene as solvent, and preheated to 40°C, and simultaneously introduced into a reactor containing chlorobenzene with liquid phosgene at -5°C for 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, the residence time is 2 h, and a photochemical liquid is obtained. After further removing hydrogen chloride, phosgene, and solvent, a crude isocyanate is obtained, and the crude product is further recrystallized to obtain pure isocyanate, which is subjected to color number detection.

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

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

[0086] The CHDA and phosgene are subjected to liquid phase phosgenation reaction in chlorobenzene solvent. The liquid phase phosgenation reaction conditions are as follows: CHDA is prepared into a 10% solution with chlorobenzene as solvent, and preheated to 40°C, and simultaneously introduced into a reactor containing chlorobenzene with liquid phosgene at -5°C for 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, the residence time is 2 h, and a photochemical liquid is obtained. After further removing hydrogen chloride, phosgene, and solvent, a crude isocyanate is obtained, and the crude product is further recrystallized to obtain pure isocyanate, which is subjected to color number detection.

[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 the isopropanol solvent without undergoing 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 isocyanate is not subjected to epoxidation treatment, and the reaction liquid after hydrogenation is directly subjected to the next step of distillation to remove the tetrahydrofuran solvent.

[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 isocyanate is not subjected to epoxidation treatment, and the reaction liquid after hydrogenation is directly subjected to the next step of distillation to remove the tetrahydrofuran solvent.

[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 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 ≤2.5, an isocyanate product with an initial platinum-cobalt color number not higher than 10 can be obtained, and the isocyanate is placed in a 60°C environment for 24 hours, and its platinum-cobalt color number is not higher than 35, and the yellowing rate is significantly lower than the control group with a higher raw material absorbance.

[0103] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing light-colored isocyanate, characterized in that: The invention comprises a process of using an amine compound as a raw material to prepare isocyanate through a phosgenation reaction; wherein: The amine compound raw material used is prepared by hydrogenation reaction, and when characterized by ultraviolet spectrophotometry, it meets the following conditions: taking anhydrous ethanol as a blank sample, the absorbance is ≤2.5 at the maximum absorption wavelength in a 0.1wt% ethanol solution.

2. The method according to claim 1, characterized in that The amine compound raw material is alicyclic amine.

3. The method according to any one of claims 1 to 2, characterized in that: The maximum absorption wavelength is 203nm, and / or, The amine compound satisfies an absorbance of ≤2.

0.

4. The method according to any one of claims 1 to 2, characterized in that: The method also includes a process of epoxidizing and purifying the amine compound raw material so as to make it meet the absorbance characterized by the ultraviolet spectrophotometry.

5. The method according to claim 4, characterized in that The epoxidation treatment method comprises: reacting an amine compound raw material with an epoxidation agent to oxidize at least an unsaturated hydrocarbon compound in the amine compound raw material into an epoxide compound; and / or The temperature of the epoxidation treatment is 0-40°C.

6. The method according to claim 5, characterized in that The epoxidation reagent is butanone peroxide, sodium hypochlorite or a high-valent iodine reagent.

7. The method according to claim 1 or 2, characterized in that: The method also includes a step of purifying and separating the isocyanate prepared by the phosgenation reaction.

8. A quality control method for preparing raw material amine compounds for light-colored isocyanates, characterized in that: The characterization was performed by ultraviolet spectrophotometry, with anhydrous ethanol as a blank sample. At the maximum absorption wavelength in a 0.1wt% ethanol solution, the amine compound raw material was prepared by hydrogenation reaction and satisfied an absorbance of ≤2.

5.

9. A light-colored isocyanate, characterized in that: The initial platinum-cobalt color number of the isocyanate is not higher than 10, and the platinum-cobalt color number is not higher than 35 when placed in a 60° C. environment for 24 hours; and / or The isocyanate is prepared by the method described in any one of claims 1 to 7 above.

10. A method for preparing polyurethane, characterized in that: The method comprises preparing isocyanate by the method according to any one of claims 1 to 7, and then polymerizing the isocyanate with a polyol.

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