Light-colored isocyanate and preparation method thereof

Abstract

The invention provides light-colored isocyanate and a preparation method thereof.The preparation method comprises the steps that firstly, an amine substance, a phosgene solution and an inert solvent are subjected to phosgenation reaction, a photochemical reaction solution is obtained, a certain amount of an auxiliary A is added into the obtained photochemical reaction solution, hydrogen chloride and phosgene in the photochemical reaction solution are removed, and a liquid-phase material is obtained; and adding a certain amount of an auxiliary agent B into the obtained liquid-phase material, and removing the solvent to obtain an isocyanate product. The addition of the assistants A and B can effectively avoid the generation of free radicals, so that the conjugate color development problem of the free radicals and the isocyanate is reduced, and the light-color isocyanate is successfully prepared by controlling the types and metering of the substances A and B.

Description

Technical Field

[0001] The invention belongs to the technical field of isocyanates, and particularly relates to a light-colored isocyanate and a preparation method thereof. Background Art

[0002] As an organic reaction intermediate, isocyanate is widely used in various industries such as industry, agriculture, construction, automobile, and thermal insulation because it can be further synthesized into polyisocyanate, polyurethane, polyurea, spandex and other materials. At present, the mainstream industrial isocyanate synthesis method is phosgenation, and the disadvantage of phosgenation is that an extremely undesirable discoloration will occur during the phosgenation process. This is because a large amount of colored substances are produced during the phosgenation reaction of diamines or polyamines, and are not removed in the subsequent separation process, and are retained in the process of further processing of isocyanate into polyurethane.

[0003] At present, there are several methods to solve the color problem of isocyanates: (1) Control of the engineering process parameters of the photochemical reaction. US5364958 discloses a method for preparing light-colored isocyanates, in which phosgene is completely removed at low temperature after photochemical reaction, and then the reaction liquid is treated with hot HCl gas while hot to achieve the purpose of reducing the color number of the product. (2) Adding additives to lighten the color of the crude isocyanate after phosgenation; US4465639 discloses a method for preparing light-colored isocyanates, that is, adding water after phosgenation and before removing the solvent to obtain a light-colored product. EP0581100 discloses a method for preparing polyisocyanates, in which a chemical reducing agent is added after phosgenation and before removing the solvent to obtain a light-colored isocyanate. (3) Treatment of the final isocyanate; EP0561225 discloses hydrogen treatment of phosgenated isocyanate under a pressure of 1 to 150 bar and a temperature of 100 to 180°C to improve the color of the final product. EP0133528 extracts and purifies isocyanates to obtain a light-colored MDI component. (4) Pretreatment of the raw amine: EP0866057 and US5872278 disclose a method of treating the amine with a Lewis acid or Bronsted acid solid substance before phosgenation to obtain a lighter-colored isocyanate. (5) Controlling the quality of the raw phosgene: CN102317255A discloses a method of adjusting the molar excess of the adjustable carbon monoxide to adjust the color of the isocyanate.

[0004] However, the formation of colored substances in isocyanates does not only come from impurity components, but more from the generation of byproducts during the phosgenation process, which leads to coloration. Controlling parameters such as the amount of phosgene added during the phosgenation process will have a significant impact on the phosgenation reaction effect, resulting in increased side reactions and reduced isocyanate yields. In addition, although adding additives to the obtained isocyanate product can improve the color of the product to a certain extent, it cannot fundamentally avoid the generation of chromogenic substances, and the degree of color improvement is limited.

[0005] In summary, it can be found that developing a method for preparing light-colored isocyanates that can avoid affecting the effect of the phosgenation reaction and fundamentally avoid the generation of chromogenic substances is a technical problem that urgently needs to be solved in this field. Summary of the invention

[0006] In view of the deficiencies in the prior art, the object of the present invention is to provide a light-colored isocyanate and a method for preparing the same. The preparation method adds different types of additives during the phosgene removal and solvent separation stages, thereby blocking the generation of colored substances from the source of phosgenation color-related side reactions, thereby achieving the successful preparation of light-colored isocyanates.

[0007] To achieve this object, the present invention adopts the following technical solutions:

[0008] A method for preparing a light-colored isocyanate, comprising the steps of:

[0009] (1) An amine substance and a phosgene solution are subjected to a phosgenation reaction in an inert solvent to obtain a photochemical reaction liquid containing an isocyanate;

[0010] (2) adding an auxiliary agent A to the photochemical reaction liquid, and then removing hydrogen chloride and phosgene to obtain a liquid phase material; (3) adding an auxiliary agent B to the liquid phase material, and then removing the inert solvent to obtain a light-colored isocyanate;

[0011] The auxiliary agent A in step (2) is selected from one or more of spiroethylene glycol di[2,2'-methylenebis(4,6-di-tert-butylphenyl)]phosphite, tetrakis(2,4-di-tert-butylphenyl-4,4-biphenyl)bisphosphate, and UV-123;

[0012] The auxiliary agent B in step (3) is selected from one or more of triphosphite (GW-540), Tinuvin 144, Tinuvin 770, Tinuvin 292, and Tinuvin 765.

[0013] In the isocyanate preparation process, the temperature of the phosgene and solvent removal stage is higher than that of the phosgenation reaction. Phosgene is easy to form adducts with the by-products of the phosgenation reaction. These adducts will produce color-producing substances after high-temperature treatment in the later solvent separation process. In the present invention, in step (2), a certain amount of auxiliary agent A is added to the photochemical reaction liquid. The auxiliary agent A can combine with phosgene and the by-products of the phosgenation reaction to generate other substances that will not affect the color when treated at high temperature, thereby achieving the goal of preparing light-colored isocyanates.

[0014] In order to further improve the quality of isocyanate, step (3) of the present invention further treats the adduct of the remaining phosgene and the phosgenation by-product on the basis of step (2). After dephosgenation, an auxiliary agent B is added to react with the adduct of phosgene and the phosgenation by-product, so that the adduct can be decomposed to produce a substance that does not affect the color when treated at high temperature.

[0015] In the present invention, the phosgenation reaction in step (1) is carried out at a temperature of 60 to 160°C, such as 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C or 150°C;

[0016] In the present invention, the photochemical reaction liquid in step (1) contains phosgene in an amount of 1000-50000 ppm by mass, such as 1000 ppm, 5000 ppm, 10000 ppm or 50000 ppm, etc., preferably 10000-20000 ppm; in the present invention, the removal of hydrogen chloride and phosgene in step (2) is carried out at a temperature of 100-180°C, such as 110°C, 120°C, 130°C, 140°C, 150°C, 160°C or 170°C, etc., preferably 140-160°C; the removal pressure is -0.2-3barg, for example, -0.15barg, -0.1barg, -0.05barg, 0barg, 0.05barg, 0.1barg, 0.15barg, 0.5barg, 1barg, 2barg or 3barg, etc., preferably -0.1-2barg, more preferably 0-0.5barg.

[0017] In step (2) of the present invention, the theoretical mass ratio of the auxiliary agent A to the photochemical reaction liquid is defined as c, and the theoretical mass ratio c is calculated according to the following formula:

[0018] c=0.0039*a+0.0156*b

[0019] Wherein, c is the theoretical mass ratio of the additive A to the photochemical reaction liquid, ppm;

[0020] The a value represents the mass percentage of phosgene in the photochemical reaction liquid in step (1), in ppm;

[0021] The b value represents the removal temperature of hydrogen chloride and phosgene in the photochemical reaction liquid in step (2), in units of ° C; at the same time, the actual mass ratio of the auxiliary agent A to the photochemical reaction liquid is limited to d, and the range of d / c is 0.1 to 2.0, such as 0.1, 0.2, 0.5, 1.5, 2.0, etc., preferably 0.5 to 1.5. The experimental study of the present invention found that there is a ratio relationship between the theoretical mass ratio c and the values ​​of a and b. The optimal relationship between c and a and b is obtained by fitting in combination with a large amount of experimental data, and the theoretical mass ratio c is calculated; then the actual mass ratio d is determined based on the relationship between the actual mass ratio d and the theoretical mass ratio c, and then the actual addition amount of the auxiliary agent A is determined.

[0022] In the present invention, the mass proportion of phosgene in the liquid phase material of step (2) is 10 to 500 ppm, such as 10 ppm, 50 ppm, 100 ppm or 500 ppm, etc., preferably 50 to 200 ppm.

[0023] In the present invention, the removal of the inert solvent in step (3) is carried out at a temperature of 100 to 220° C., such as 120° C., 140° C., 160° C., 180° C. or 200° C., preferably 130 to 200° C.;

[0024] The removal pressure is -1 to 0 barg, for example, -0.9 barg, -0.8 barg, -0.7 barg, -0.6 barg, -0.5 barg, -0.4 barg, -0.3 barg, -0.2 barg or -0.1 barg, etc., preferably -0.9 to -0.2 barg, more preferably -0.7 to -0.4 barg.

[0025] In step (3) of the present invention, the theoretical mass ratio of the auxiliary agent B to the liquid phase material is defined as g, and the theoretical mass ratio g is calculated according to the following formula:

[0026] g=0.00012*e 2 +0.00039*f 2

[0027] Wherein, g is the theoretical mass ratio of additive B to liquid phase material, ppm;

[0028] The e value represents the mass percentage of phosgene in the liquid phase material in step (2), in ppm;

[0029] The f value represents the removal temperature of the inert solvent from the liquid phase material in step (3), in °C;

[0030] The actual mass ratio of the auxiliary agent B to the liquid phase material is h, and the range of h / g is 0.1 to 2.0, such as 0.1, 0.2, 0.5, 1.5, 2.0, etc., preferably 0.5 to 1.5. The experimental study of the present invention found that there is an optimal ratio relationship between the theoretical mass ratio g and the values ​​of e and f. The optimal relationship between g and e and f is obtained by fitting a large amount of experimental data, and the theoretical mass ratio g is calculated; then the actual mass ratio h is determined according to the relationship between the actual mass ratio h and the theoretical mass ratio g, and then the actual addition amount of the auxiliary agent B is determined.

[0031] The preparation method of light-colored isocyanate provided by the present invention first adopts an amine substance, phosgene and an inert solvent to carry out a phosgenation reaction to obtain a photochemical reaction liquid containing isocyanate. This process is a method disclosed in the field. It should be noted that the following method provided by the present invention is only used to illustrate one of the methods used to realize the photochemical reaction liquid of the present invention. The phosgenation reaction described in the present invention should not be limited by the steps and parameters in the following method.

[0032] Specifically, in the present invention, firstly, an amine substance, a phosgene solution and an inert solvent are subjected to a phosgenation reaction at 60 to 160° C. to obtain a photochemical reaction liquid containing isocyanate, and this process also produces a gaseous material containing hydrogen chloride and phosgene; an auxiliary agent A is added to the photochemical reaction liquid, and then the hydrogen chloride and phosgene in the reaction liquid are removed at 100 to 180° C. to obtain a liquid material, and this process also produces a gaseous material containing hydrogen chloride and phosgene; then an auxiliary agent B is added to the liquid material obtained above, and then the inert solvent in the material is removed to obtain a light-colored crude isocyanate product.

[0033] Previous studies have shown that the generation of colored substances in the production process of isocyanate is mainly related to the phosgene residue and temperature in the process of phosgene removal and solvent removal. The present invention adds a trace amount of auxiliary agent to the phosgenation reaction liquid before and after the phosgene removal, and accurately controls the amount of auxiliary agent added according to different temperatures and phosgene residues, effectively preventing the generation of free radicals, thereby avoiding the problem of free radicals and isocyanates producing conjugated colors. This method does not require HCl gas stripping treatment of the reaction liquid after phosgene removal, saves dry HCl, and improves the utilization rate of dry HCl. At the same time, it does not need to adjust and limit the photochemical reaction process, avoiding the problem of improving the color number causing the photochemical reaction effect to deteriorate and the isocyanate yield to decrease. The entire preparation method has the advantages of simple process, convenient operation, energy saving, low cost, high efficiency and environmental friendliness. In addition, an unexpected result is that after adding the above-mentioned trace additives A and B, the -NCO loss is reduced and the isocyanate yield is improved during the removal of phosgene, HCl and solvent. The reason for this is analyzed to be that the trace substances can prevent the generation of free radicals, reduce the generation of -NCO self-polymerization catalytic intermediates, and thus reduce the loss of -NCO groups.

[0034] The "light-colored isocyanate" mentioned in the present invention refers to a crude isocyanate product with an L color higher than 85. The L color item in isocyanate is an important indicator for monitoring the quality of the product and has a great influence on the color of subsequent products. Currently, it is measured using an integrating sphere spectrophotometer to measure the transmittance of the sample.

[0035] In the present invention, after the phosgenation reaction in step (1) and the step of removing hydrogen chloride and phosgene from the photochemical reaction liquid in step (2) are completed, gaseous materials are generated, and the above-mentioned gaseous materials are first condensed and then reused, wherein the condensate obtained by condensing the gaseous materials generated in step (1) is refluxed to the reactor of the phosgenation reaction (preferably the reactor of the thermal phosgenation reaction); and the non-condensable gas is sent to the gaseous absorption system, in which the phosgene can be absorbed by an inert solvent, and the obtained phosgene solution is reused in the phosgenation reaction again, and the gaseous hydrogen chloride can also be absorbed by hydrochloric acid in the gaseous absorption system.

[0036] Preferably, the gas phase absorption system may use any absorption tower known in the art, preferably a packed tower or a plate tower, more preferably a packed tower.

[0037] Preferably, the absorption temperature of the gas phase absorption system is -15 to 15°C, for example, -13°C, -11°C, -9°C, -7°C, -5°C, -3°C, -1°C, 3°C, 5°C, 7°C or 9°C.

[0038] Preferably, the absorption pressure of the gas phase absorption system is 0-10 barg, for example, 2 barg, 4 barg, 6 barg, 8 barg or 10 barg.

[0039] Preferably, the inert solvent in the gas phase absorption system is selected from any one or a combination of at least two of chlorobenzene, dichlorobenzene, trichlorobenzene, toluene, xylene, benzene and diethyl isophthalate, and more preferably chlorobenzene and / or o-dichlorobenzene.

[0040] Preferably, the mass percentage of phosgene in the phosgene solution obtained in the gas phase absorption system is 50-90%, for example, 55%, 60%, 65%, 70%, 75%, 80% or 85%.

[0041] Preferably, the amine substance in step (1) is selected from diamine or polyamine compounds, preferably any one or a combination of at least two of diaminodiphenylmethane, polymethylene polyphenyl polyamines, diaminotoluene, isophoronediamine, hexamethylenediamine, cyclohexanediamine, p-phenylenediamine, naphthalenediamine, xylene diamine, cyclohexane dimethylene diamine, tetramethyl meta-xylene diamine or dimethylbenzene diamine, more preferably diaminodiphenylmethane and / or polymethylene polyphenyl polyamines.

[0042] Preferably, the inert solvent in step (1) is selected from any one or a combination of at least two of chlorobenzene, dichlorobenzene, trichlorobenzene, toluene, xylene, benzene, and diethyl isophthalate, and more preferably chlorobenzene and / or o-dichlorobenzene.

[0043] Preferably, the mass percentage of phosgene in the phosgene solution in step (1) is 50-90%, for example, 55%, 60%, 65%, 70%, 75%, 80%, 85% or 90%, etc.;

[0044] The phosgene solution refers to a mixed solution formed by phosgene and an inert solvent. The inert solvent used in the phosgene solution is the same as the inert solvent used in the aforementioned phosgenation reaction.

[0045] Preferably, the mass ratio of the amine substance to the phosgene solution in step (1) is 1:(2-8), such as 1:3, 1:4, 1:5, 1:6 or 1:7, and more preferably 1:(3-5);

[0046] Preferably, the mass ratio of the amine substance to the inert solvent in step (1) is 1:(2-6), for example 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5 or 1:5.5, more preferably 1:(2.5-5), and further preferably 1:(3-4).

[0047] Before carrying out the phosgenation reaction in step (1) of the present invention, the amine substance and the inert solvent may be mixed first, and the mixing may be carried out using a mixing device known in the art, preferably a static mixer. Preferably, the phosgenation reaction in step (1) includes a cold phosgenation reaction and a hot phosgenation reaction. The present invention does not impose any special restrictions on the reactors used for the cold phosgenation reaction and the hot phosgenation reaction, and any reactor known in the art may be selected; wherein, the cold phosgenation reaction is preferably a jet reactor, and the hot phosgenation reaction is preferably a kettle reactor, and the specific operating conditions are not particularly limited, and the technicians may screen them according to the known processes.

[0048] Preferably, the temperature of the cold light gasification reaction is 60-140°C, for example, 70°C, 80°C, 90°C, 100°C, 110°C, 120°C or 130°C.

[0049] Preferably, the pressure of the cold light gasification reaction is 1 to 30 barg, for example, 5 barg, 10 barg, 15 barg, 20 barg, 25 barg or 30 barg.

[0050] Preferably, the temperature of the thermal phosgenation reaction is 110-160°C, for example, 115°C, 120°C, 125°C, 130°C, 135°C, 140°C, 145°C, 150°C or 155°C.

[0051] Preferably, the pressure of the thermal phosgenation reaction is 2 to 20 barg, for example, 4 barg, 6 barg, 8 barg, 10 barg, 12 barg, 14 barg, 16 barg or 18 barg.

[0052] As a preferred technical solution of the present invention, the preparation method comprises the following steps:

[0053] (1) subjecting an amine substance, a phosgene solution and an inert solvent to a cold phosgenation reaction at 60 to 140° C. and 1 to 30 barg for 1 to 90 minutes, and then subjecting an amine substance, a phosgene solution and an inert solvent to a hot phosgenation reaction at 110 to 160° C. and 2 to 20 barg for 1 to 8 hours to obtain a photochemical reaction liquid containing isocyanate;

[0054] (2) adding an auxiliary agent A to the photochemical reaction liquid, and then removing hydrogen chloride and phosgene at 100 to 180° C. and −0.2 to 3 barg to obtain a liquid phase material;

[0055] (3) Adding auxiliary agent B to the liquid phase material, and then removing the inert solvent under the conditions of 100 to 220° C. and −1 to 0 barg to obtain a light-colored crude isocyanate product.

[0056] The present invention also provides a light-colored isocyanate, which is prepared by the preparation method as described above.

[0057] Preferably, the L color of the light-colored isocyanate is higher than 85, such as 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, etc.

[0058] Compared with the prior art, the present invention has the following beneficial effects:

[0059] The preparation method of light-colored isocyanate provided by the present invention firstly carries out phosgenation reaction on an amine substance, a phosgene solution and an inert solvent to obtain a photochemical reaction liquid, and by adding different types of trace additives in the phosgene removal and solvent separation stages, the generation of free radicals is effectively prevented, thereby avoiding the problem of coloration caused by the conjugation of free radicals and isocyanates, starting from the source of the phosgenation color-related side reactions, blocking the generation of colored substances, and successfully preparing a light-colored isocyanate with an L color higher than 85. Surprisingly, the addition of trace additives A and B in the present invention also reduces the generation of -NCO group polymerization catalytic intermediates and reduces the loss of -NCO. DETAILED DESCRIPTION

[0060] The technical scheme of the present invention is further illustrated by specific implementation methods. Those skilled in the art should understand that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention. The main raw materials in the embodiments and comparative examples of the present invention are as follows. Other raw materials and reagents are purchased from commercial sources or obtained by conventional methods unless otherwise specified:

[0061] Diphenylmethanediamine (i.e. diaminodiphenylmethane), diaminotoluene, and isophoronediamine: Wanhua Chemical; Chlorobenzene: purchased from Jiangsu Longchang Chemical Co., Ltd.;

[0062] Phosgene: Wanhua Chemical;

[0063] Spiroethylene glycol di[2,2'-methylenebis(4,6-di-tert-butylphenyl)]phosphite: purchased from Hubei Ruike Chemical Co., Ltd.;

[0064] Tetrakis (2,4-di-tert-butylphenyl-4,4-biphenyl) bisphosphate: purchased from Tianmen Hengchang Chemical Co., Ltd.;

[0065] UV-123: purchased from Tianjin Lianlong New Materials Co., Ltd.;

[0066] Triphosphite (GW-540): purchased from Gaoyi County Hongsen Chemical Co., Ltd.;

[0067] Tinuvin144, Tinuvin770, Tinuvin 292, Tinuvin765: purchased from Shanghai Jingyan Chemical Co., Ltd.

[0068] Example 1

[0069] The steps for preparing light-colored isocyanates are:

[0070] (1) diphenylmethanediamine (60% by mass) with a flow rate of 30 t / h and a pressure of 20 barg, a mixture of polymethylene polyphenyl polyamines and chlorobenzene with a flow rate of 25 t / h and a pressure of 20 barg are uniformly mixed in a static mixer, and then introduced into a jet reactor with a flow rate of 35 t / h and a pressure of 20 barg of phosgene solution (the mass percentage of phosgene is 70%, and the solvent is chlorobenzene), and a cold phosgenation reaction is carried out at 100° C. and 10 barg for 1 min, and then introduced into a kettle reactor for a hot phosgenation reaction at 130° C. and 3 barg for 4 h, to obtain 76 t / h of a photochemical reaction liquid containing isocyanate and a gaseous material containing phosgene and hydrogen chloride;

[0071] (2) adding 3.0 kg / h of spiroethylene glycol di[2,2'-methylenebis(4,6-di-tert-butylphenyl)]phosphite to the photochemical reaction liquid obtained in step (1) (the mass ratio of the auxiliary agent A to the photochemical reaction liquid is 39 ppm; wherein c=0.0039*a+0.0156*b, a=12000 ppm, b=140°C; d / c=0.8), and then feeding the mixture into a phosgene removal tower, removing hydrogen chloride and phosgene under the conditions of a bottom temperature of 140°C and a top pressure of 0.2 barg, to obtain 73 t / h of liquid phase material;

[0072] (3) 1.1 kg / h Tinuvin 770 was added to the liquid phase material obtained in step (2) (the mass ratio of auxiliary agent B to liquid phase material was 16 ppm; wherein g = 0.00012*e 2 +0.00039*f 2 , e = 200ppm, f = 180 ° C; h / g = 0.9), and then sent to a solvent removal tower, under the conditions of a bottom temperature of 180 ° C and a top pressure of -0.6 barg, chlorobenzene is removed, and the solution in the bottom of the solvent removal tower is collected to obtain a light-colored isocyanic acid product.

[0073] The gaseous material and the gaseous material produced after the thermal phosgenation reaction in step (1) are simultaneously fed into a phosgene recovery tower for recovery and reuse. Chlorobenzene is introduced into the phosgene recovery tower. Chlorobenzene countercurrently contacts with the phosgene in the gaseous material and absorbs it to produce a phosgene solution. The bottom temperature of the phosgene absorption tower is -2°C, and the top temperature is 3 barg.

[0074] Example 2

[0075] The steps for preparing light-colored isocyanates are:

[0076] (1) diaminotoluene (56% by mass) with a flow rate of 30 t / h and a pressure of 20 barg, a mixture of polymethylene polyphenyl polyamines and chlorobenzene with a flow rate of 50 t / h and a pressure of 20 barg are uniformly mixed in a static mixer, and then introduced into a jet reactor with a flow rate of 35 t / h and a pressure of 20 barg of phosgene solution (the mass percentage of phosgene is 70%, and the solvent is chlorobenzene), and a cold phosgenation reaction is carried out at 100° C. and 10 barg for 1 min, and then introduced into a kettle reactor for a hot phosgenation reaction at 132° C. and 3 barg for 3.8 hours, to obtain 101 t / h of a photochemical reaction liquid containing isocyanate and a gaseous material containing phosgene and hydrogen chloride;

[0077] (2) adding 0.7 kg / h of tetrakis(2,4-di-tert-butylphenyl-4,4-biphenyl)bisphosphate to the photochemical reaction liquid obtained in step (1) (the mass ratio of the auxiliary agent A to the photochemical reaction liquid is 7 ppm; wherein c=0.0039*a+0.0156*b, a=9000 ppm, b=138° C.; d / c=0.2), and then feeding the mixture into a phosgene removal tower, removing hydrogen chloride and phosgene under the conditions of a bottom temperature of 138° C. and a top pressure of 0.15 barg, to obtain 98 t / h of liquid phase material;

[0078] (3) 1.6 kg / h Tinuvin765 was added to the liquid material obtained in step (2) (the mass ratio of auxiliary agent B to liquid material was 16 ppm; wherein g = 0.00012*e 2 +0.00039*f 2 , e=179ppm, f=205; h / g=0.8), and then sent to a solvent removal tower to remove chlorobenzene under the conditions of a bottom temperature of 205°C and a top pressure of -0.6barg, and the solution in the bottom of the solvent removal tower was collected to obtain a light-colored isocyanic acid product.

[0079] Example 3

[0080] The steps for preparing light-colored isocyanates are:

[0081] (1) isophorone diamine (65% by mass) with a flow rate of 30 t / h and a pressure of 20 barg, a mixture of polymethylene polyphenyl polyamines and chlorobenzene with a flow rate of 25 t / h and a pressure of 20 barg are uniformly mixed in a static mixer, and then introduced into a jet reactor with a flow rate of 60 t / h and a pressure of 20 barg of phosgene solution (the mass percentage of phosgene is 70%, and the solvent is chlorobenzene), and a cold phosgenation reaction is carried out at 105° C. and 10 barg for 0.9 min, and then introduced into a kettle reactor for a hot phosgenation reaction at 130° C. and 3 barg for 4 h, to obtain 83 t / h of a photochemical reaction liquid containing isocyanate and a gaseous material containing phosgene and hydrogen chloride;

[0082] (2) adding 7.8 kg / h of bis[2-methyl-4,6-di(1,1'-dimethylethyl)phenol]ethyl phosphate to the photochemical reaction liquid obtained in step (1) (the mass ratio of the auxiliary agent A to the photochemical reaction liquid is 93 ppm; wherein c=0.0039*a+0.0156*b, a=13500 ppm, b=142° C.; d / c=1.7), and then feeding the mixture into a phosgene removal tower, removing hydrogen chloride and phosgene under the conditions of a bottom temperature of 142° C. and a top pressure of 0.2 barg, to obtain 81 t / h of liquid phase material;

[0083] (3) Add 0.5 kg / h Tinuvin144 to the liquid material obtained in step (2) (the mass ratio of auxiliary agent B to liquid material is 6 ppm; wherein g = 0.00012*e 2 +0.00039*f 2 , e=188, f=180; h / g=0.36), and then sent to a solvent removal tower to remove chlorobenzene under the conditions of a bottom temperature of 180°C and a top pressure of -0.6 barg, and the solution in the bottom of the solvent removal tower was collected to obtain a light-colored isocyanic acid product.

[0084] Comparative Example 1

[0085] Isocyanate was prepared by referring to the method of Example 1, except that the auxiliary agent A-spiroethylene glycol di[2,2'-methylenebis(4,6-di-tert-butylphenyl)]phosphite was not added in step (2), and the auxiliary agent BTinuvin770 was not added in step (3). Other operations and parameters remained unchanged to obtain an isocyanate product.

[0086] Comparative Example 2

[0087] Isocyanate was prepared by referring to the method of Example 1, except that spiroethylene glycol di[2,2'-methylenebis(4,6-di-tert-butylphenyl)]phosphite was not added in step (2), and other operations and parameters remained unchanged to obtain an isocyanate product.

[0088] Comparative Example 3

[0089] Isocyanate was prepared by referring to the method of Example 1, except that in step (2), spiroethylene glycol di[2,2'-methylenebis(4,6-di-tert-butylphenyl)]phosphite was replaced by an equal amount of Tinuvin 770, and other operations and parameters remained unchanged to obtain an isocyanate product.

[0090] Comparative Example 4

[0091] Isocyanate was prepared by referring to the method of Example 1, except that Tinuvin 770 was not added in step (3), and other operations and parameters remained unchanged to obtain an isocyanate product.

[0092] Comparative Example 5

[0093] Isocyanate was prepared by referring to the method of Example 1, except that in step (3), Tinuvin 770 was replaced by an equal amount of spiroethylene glycol di[2,2'-methylenebis(4,6-di-tert-butylphenyl)]phosphite, and other operations and parameters remained unchanged to obtain an isocyanate product.

[0094] Comparative Example 6

[0095] Isocyanate was prepared by referring to the method of Example 1, except that Tinuvin 770 was adjusted to be added simultaneously with spiroethylene glycol di[2,2'-methylenebis(4,6-di-tert-butylphenyl)]phosphite in step (2), and Tinuvin 770 was no longer added in step (3). Other operations and parameters remained unchanged to obtain the isocyanate product.

[0096] Comparative Example 7

[0097] Isocyanate was prepared by referring to the method of Example 1, except that spiroethylene glycol di[2,2'-methylenebis(4,6-di-tert-butylphenyl)]phosphite and Tinuvin 770 were adjusted to be added simultaneously in step (3), and spiroethylene glycol di[2,2'-methylenebis(4,6-di-tert-butylphenyl)]phosphite was no longer added in step (2). Other operations and parameters remained unchanged to obtain an isocyanate product.

[0098] The performance test parameters and corresponding test methods in the embodiments and comparative examples of the present invention are as follows:

[0099] L color of isocyanate: measured by integrating sphere spectrophotometer with dichloromethane as standard. NCO content of isocyanate is measured by GB / T2009-3-2009 method.

[0100] The light-colored pure isocyanate and light-colored polymerized isocyanate provided in Examples 1 to 3 and Comparative Examples 1 to 11 were tested according to the above test method. The test results are shown in Table 1:

[0101] Table 1

[0102]

[0103] According to the data in Table 1, it can be seen that the present invention effectively avoids the generation of chromogenic substances in the preparation process by adding trace substances to the reaction liquid before and after dephosgenesis, fundamentally reduces the color of the isocyanate product, thereby reducing the color depth of the isocyanate product, reducing the loss of -NCO groups, and improving the product yield. Specifically, the L chromaticity of the isocyanate product obtained by the preparation method provided in Examples 1 to 3 is 84 to 93. Comparing the data of Example 1 and Comparative Example 1, it can be found that in the desolventizing stage, without taking any measures, direct distillation will result in a decrease in the L chromaticity of the obtained isocyanate product.

[0104] The applicant declares that the present invention illustrates a light-colored isocyanate and its preparation method and application through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned embodiments, that is, it does not mean that the present invention must rely on the above-mentioned embodiments to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of various raw materials of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing a light-colored isocyanate, It is characterized in that the steps include: (1) An amine substance and a phosgene solution are subjected to a phosgenation reaction in an inert solvent to obtain a photochemical reaction liquid containing an isocyanate; (2) adding an auxiliary agent A to the photochemical reaction liquid, and then removing hydrogen chloride and phosgene to obtain a liquid phase material; (3) adding an auxiliary agent B to the liquid phase material, and then removing the inert solvent to obtain a light-colored isocyanate; the auxiliary agent A in step (2) is selected from one or more of spiroethylene glycol di[2,2'-methylenebis(4,6-di-tert-butylphenyl)]phosphite, tetrakis(2,4-di-tert-butylphenyl-4,4-biphenyl)bisphosphate, and UV-123; The auxiliary agent B in step (3) is selected from one or more of triphosphite, Tinuvin 144, Tinuvin 770, Tinuvin 292, and Tinuvin 765.

2. The preparation method according to claim 1, It is characterized in that The amine substance in step (1) is selected from diamine or polyamine compounds, preferably any one or a combination of at least two of diaminodiphenylmethane, polymethylene polyphenyl polyamines, diaminotoluene, isophorone diamine, hexamethylenediamine, cyclohexane diamine, p-phenylenediamine, naphthalene diamine, xylene diamine, cyclohexane dimethylene diamine, tetramethyl meta-xylene diamine or dimethylbenzene diamine, more preferably diaminodiphenylmethane and / or polymethylene polyphenyl polyamines.

3. The preparation method according to claim 1, It is characterized in that The inert solvent in step (1) is selected from any one or a combination of at least two of chlorobenzene, dichlorobenzene, trichlorobenzene, toluene, xylene, benzene and diethyl isophthalate, and is more preferably chlorobenzene and / or o-dichlorobenzene.

4. The preparation method according to claim 1, It is characterized in that The mass percentage of phosgene in the phosgene solution of step (1) is 50-90%; and / or The phosgene solution refers to a mixed solution of phosgene and an inert solvent, wherein the inert solvent is selected from any one or a combination of at least two of chlorobenzene, dichlorobenzene, trichlorobenzene, toluene, xylene, benzene, and diethyl isophthalate, preferably chlorobenzene and / or o-dichlorobenzene.

5. The preparation method according to claim 1, It is characterized in that The mass ratio of the amine substance to the phosgene solution in step (1) is 1:(2-8), preferably 1:(3-5); and / or The mass ratio of the amine substance to the inert solvent in step (1) is 1:(2-6), preferably 1:(2.5-5), more preferably 1:(3-4); and / or The phosgenation reaction in step (1) is carried out at a temperature of 60 to 160° C.; and / or The photochemical reaction liquid of step (1) has a phosgene mass fraction of 1000-50000 ppm, preferably 10000-20000 ppm.

6. The preparation method according to claim 1, It is characterized in that In step (2), the removal of hydrogen chloride and phosgene is carried out at a temperature of 100 to 180° C., preferably 140 to 160° C.; the removal pressure is -0.2 to 3 barg, preferably -0.1 to 2 barg, more preferably 0 to 0.5 barg; and / or The liquid phase material of step (2) contains phosgene in an amount of 10 to 500 ppm by mass, preferably 50 to 200 ppm by mass.

7. The preparation method according to claim 1, It is characterized in that In step (2), the theoretical mass ratio of the auxiliary agent A to the photochemical reaction liquid is defined as c, and the theoretical mass ratio c is calculated according to the following formula: c=0.0039*a+0.0156*b Wherein, c is the theoretical mass ratio of the additive A to the photochemical reaction liquid, ppm; The a value represents the mass ratio of phosgene in the photochemical reaction liquid in step (1), in ppm; the b value represents the removal temperature of hydrogen chloride and phosgene in the photochemical reaction liquid in step (2), in ° C; the actual mass ratio of the auxiliary agent A to the photochemical reaction liquid is d, and the range of d / c is 0.1 to 2.0, preferably 0.5 to 1.

5.

8. The preparation method according to claim 1, It is characterized in that In step (3), the inert solvent is removed at a temperature of 100 to 220° C., preferably 130 to 200° C.; the removal pressure is -1 to 0 barg, preferably -0.9 to -0.2 barg, and more preferably -0.7 to -0.4 barg.

9. The preparation method according to claim 1, It is characterized in that In step (3), the theoretical mass ratio of the additive B to the liquid phase material is defined as g, and the theoretical mass ratio g is calculated according to the following formula: g=0.00012*e 2 +0.00039*f 2 Wherein, g is the theoretical mass ratio of additive B to liquid phase material, ppm; The e value represents the mass percentage of phosgene in the liquid phase material in step (2), in ppm; The f value represents the removal temperature of the inert solvent from the liquid phase material in step (3), in °C; The actual mass ratio of the auxiliary agent B to the liquid phase material is h, and the range of h / g is 0.1 to 2.0, preferably 0.5 to 1.

5.

10. A light-colored isocyanate prepared by the method of claims 1 to 9, It is characterized in that The light-colored isocyanate has an L color greater than 85.

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