A hexamethylene diisocyanate composition and its preparation method and application

Abstract

The present invention relates to a hexamethylene diisocyanate composition and a preparation method and application thereof. The hexamethylene diisocyanate composition comprises hexamethylene diisocyanate and 0.2-500 ppm of a cyclic compound, and the chromaticity change rate after heat treatment at 140°C for 4 hours is less than 8. The polyisocyanate prepared by the hexamethylene diisocyanate composition provided by the present invention has excellent low chromaticity relative stability.

Description

Technical Field

[0001] The invention relates to the technical field of isocyanates, and in particular to a low-chroma, relatively stable hexamethylene diisocyanate composition, a preparation method and an application thereof. Background Art

[0002] Hexamethylene diisocyanate is an aliphatic isocyanate with excellent yellowing resistance compared to aromatic isocyanates. It is generally obtained by reacting hexamethylenediamine with phosgene in the industry, and it is particularly advantageous to do it in the gas phase. However, a common problem is that, for whatever reason, industrial isocyanate products are colored or have adverse effects on the color of polyisocyanates such as trimers or biuret or uretdione in their downstream modification steps.

[0003] Patent CN113072512A discloses a method for improving the turbidity change of polyisocyanate during storage by controlling the content of dichlorohexyl isocyanate in 1,6-hexamethylene diisocyanate, but does not provide any teaching on the improvement of product color, nor does it provide any teaching on the influence of other impurities on color.

[0004] Patent CN106946741B discloses a method for preparing dicyclohexylmethane diisocyanate with excellent storage resistance to yellowing. The method comprises purifying the raw material dicyclohexylmethane diamine and controlling the aromatic monoamine compound therein to be below 0.1wt%. The dicyclohexylmethane diisocyanate obtained by phosgenation using the raw material as the raw material has excellent yellowing resistance, but has no guiding effect on the color improvement of hexamethylene diisocyanate and its prepolymer.

[0005] Patent CN110982045B provides a method for preparing a low-color isocyanate curing agent, which is achieved by controlling the double bond content in the long-chain alcohol to ≤10 ppm and the peroxide content to ≤500 ppm, but does not provide any guidance on the quality of the isocyanate.

[0006] Patent CN112250835B discloses a method of reducing the color by adjusting the pH value of the polyisocyanate catalyst solution to 5-7, but also does not provide any guidance on the quality of isocyanate. Summary of the invention

[0007] In view of the deficiencies in the prior art, the present invention provides a low-color, relatively stable hexamethylene diisocyanate composition and a preparation method and application thereof. The polyisocyanate obtained by using the hexamethylene diisocyanate composition prepared by the present invention as a raw material has the characteristics of low-color, relatively stable.

[0008] To achieve this object, the present invention adopts the following technical solutions:

[0009] A hexamethylene diisocyanate composition comprises hexamethylene diisocyanate and 0.2-500 ppm of a cyclic compound.

[0010] The hexamethylene diisocyanate composition of the present invention is a substantially single compound (i.e., hexamethylene diisocyanate) containing 99 wt % or more of hexamethylene diisocyanate as a main component, but is defined as a hexamethylene diisocyanate composition because it contains the above-mentioned cyclic compound as a minor component.

[0011] The hexamethylene diisocyanate composition, the cyclic compound comprises any one or a combination of at least two of the following compounds:

[0012]

[0013] Wherein X is CH3 or H or Cl or Br.

[0014] This type of impurities originates from the product obtained by the reaction of impurities in the feed amine with phosgene (or bromine-containing phosgene). Some of the impurities in the amine come directly from the raw amine, and some are by-products of the raw amine or the impurities in the raw amine after high-temperature heating.

[0015] The researchers of the present invention have found in their studies that when the hexamethylene diisocyanate composition contains 0.2-500 ppm of the above-mentioned cyclic compound, the prepared isocyanate and polyisocyanate thereof have excellent low chromaticity relative stability. When the content is lower than 0.2 ppm or higher than 500 ppm, the low chromaticity relative stability will deteriorate.

[0016] Preferably, the content of cyclic compounds in the hexamethylene diisocyanate composition is 0.4-200 ppm, more preferably 0.8-100 ppm.

[0017] The content of the cyclic compound described in the present invention can be implemented by, but not limited to, the following methods, such as by controlling the reaction conditions, or separation conditions, or by additional addition, so that the content of the cyclic compound can be controlled within the range.

[0018] In addition, by controlling the content of the cyclic compound, the color change rate of the product of the hexamethylene diisocyanate composition after heat treatment at 140° C. for 4 hours can be less than 8.

[0019] The chromaticity change rate of the isocyanate composition is tested in the following manner:

[0020] 1) Using German BYK LCS IV liquid colorimeter to test the initial chromaticity of the hexamethylene diisocyanate composition, the initial value is recorded as H1;

[0021] 2) Add a certain amount of hexamethylene diisocyanate composition into a 20 ml glass bottle and seal it with nitrogen;

[0022] 3) After preheating the oven to 140° C., place the nitrogen-sealed glass bottle sample of the hexamethylene diisocyanate composition in the oven and heat for 4 hours;

[0023] 4) After heating, take the sample out of the oven, cool it to room temperature, and then test the chromaticity, which is recorded as H2.

[0024] The chromaticity change rate is (H2-H1) / H1*100%.

[0025] The chromaticity change rate of the product of the hexamethylene diisocyanate composition after heat treatment at 140° C. for 4 hours is 5 or less, preferably 3 or less.

[0026] As is well known to those skilled in the art, the hexamethylene diisocyanate composition can be prepared by subjecting the hexamethylene diamine composition to a phosgenation reaction. Specifically, as the phosgenation reaction, a liquid phase phosgenation method in which the hexamethylene diamine composition reacts with phosgene in a liquid phase or a gas phase phosgenation reaction in which the hexamethylene diamine composition reacts with phosgene in a gas phase can be used. The present invention preferably uses a hexamethylene diamine composition obtained by gas phase phosgenation.

[0027] First, hexamethylenediamine is preheated and gasified in the presence or absence of an inert gas, and reacted with the preheated and gasified phosgene to obtain a hexamethylene diisocyanate composition reaction liquid; the reaction liquid obtained in the above steps is then subjected to phosgene removal, hydrogen chloride removal, and solvent removal treatment to obtain the hexamethylene diisocyanate crude product; finally, the above obtained hexamethylene diisocyanate crude product is subjected to impurity removal and purification to finally obtain the hexamethylene diisocyanate composition product.

[0028] Before the phosgenation reaction, the material stream containing hexamethylenediamine is preheated to above 200°C, preferably 200-510°C; the temperature of the material stream containing phosgene is preheated to above 200°C, preferably 200-510°C. In the present invention, the material stream containing hexamethylenediamine includes hexamethylenediamine and / or an inert gas such as nitrogen, argon, helium, etc.; the material stream containing phosgene includes fresh phosgene and / or recycled phosgene, and / or optional inert gases such as nitrogen, argon, helium, etc., wherein fresh phosgene refers to phosgene that has not undergone any phosgene-related reaction after phosgene is synthesized from chlorine and carbon monoxide, and recycled phosgene refers to phosgene that has not reacted after the phosgenation reaction and can continue to participate in the phosgenation reaction after separation and purification.

[0029] In the present invention, the reaction of phosgene and hexamethylenediamine is carried out at an absolute pressure of 0.01-0.5Mpa, preferably 0.1-0.4Mpa. The reaction temperature is 200-600°C, preferably 300-550°C;

[0030] If the high-temperature residence time of the amine and phosgene in the reaction zone of the present invention is too long, it is easy to cause the decomposition or polymerization of the amine, phosgene and the target isocyanate, resulting in the occurrence of undesirable side reactions. If the residence time is too short, the contact reaction time of phosgene and amine is insufficient, the reaction is incomplete, and the reaction yield is seriously affected. Therefore, the reaction residence time of the amine and phosgene in the reaction zone of the present invention is 0.02-20s, preferably 0.05-10s.

[0031] A higher molar ratio of phosgene to amino in the present invention is beneficial to the conversion of amine into isocyanate, but will result in a higher phosgene inventory in the system, increase safety risks, and increase costs due to phosgene preheating and condensation. A too low molar ratio of phosgene to amino may lead to poor reaction effect, affect the reaction yield and stable operation of the device, so the molar ratio of phosgene to amino in the present invention is 2-15:1, preferably 4-8:1.

[0032] The gaseous target isocyanate product passing through the reaction zone is usually at a temperature above 200°C. It is generally absorbed by a gaseous capture liquid containing an inert solvent to quench the reaction product to obtain a liquid stream containing isocyanate, which is transferred from the gas phase to the liquid phase. At the same time, part of the hydrogen chloride, unreacted phosgene and by-products will also be distributed in the reaction absorption liquid.

[0033] The reaction gas phase capture liquid in the present invention contains a solvent. The inert solvent includes one or more of toluene, xylene, dimethyl phthalate, diethyl phthalate, dibutyl phthalate, methyl benzoate, ethyl benzoate, butyl benzoate, propyl benzoate, chlorobenzene, o-dichlorobenzene, p-chlorotoluene, bromobenzene, etc., but is not limited thereto. These solvents can be used alone or mixed in any proportion.

[0034] In the present invention, the reaction product obtained in the reaction step can be subjected to phosgene removal, hydrogen chloride removal, and solvent removal operations to obtain crude hexamethylene diisocyanate. Phosgene can be used as circulating phosgene to enter the reaction system again after absorption and purification. Part or all of the solvent can be used as a capture liquid for recycling after purification.

[0035] The impurity removal and purification in the present invention is carried out on the obtained crude hexamethylene diisocyanate by a distillation purification process, and finally the hexamethylene diisocyanate composition product is obtained.

[0036] During the distillation purification, continuous distillation or intermittent distillation can be adopted. The distillation tower can be a plate tower or a packed tower. The number of distillation towers can be one tower, two towers or more than two towers to achieve the distillation effect, and there is no special limitation on this.

[0037] According to the method of the present invention, in a preferred embodiment, the content of the above-mentioned cyclic compound in the hexamethylene diisocyanate composition is controlled by continuous distillation. Specifically, the number of theoretical plates of the distillation tower is preferably 15-40, more preferably 25-35. The reflux ratio of the distillation tower is preferably 2-13:1, more preferably 2-6:1. The top pressure of the distillation tower is preferably 0.3-10kpa, more preferably 0.7-5kpa. The bottom temperature of the distillation tower is preferably 120-190°C, more preferably 130-145°C. The top extraction of the distillation tower is preferably 2-9wt%, more preferably 3-7wt%.

[0038] The polyisocyanate prepared by using the hexamethylene diisocyanate composition with the above-mentioned cyclic compound content as a raw material, such as containing any one or a combination of at least two of the following (a)-(e) groups: (a) isocyanurate group, (b) uretdione group, (c) biuret group, (d) carbamate group, (e) urea group, (f) iminooxadiazinedione group, (g) allophanate group, (h) uretonimine group or (i) carbodiimide group, has the advantages of low chromaticity and relative stability.

[0039] Finally, the present invention provides a polyisocyanate composition, which includes but is not limited to a polyisocyanate composition containing an isocyanurate group. The preparation method thereof uses a hexamethylene diisocyanate composition as a raw material, performs a trimerization reaction under the action of a catalyst, adds a terminator to stop the reaction after reaching the reaction end point, and then separates to obtain the polyisocyanate composition containing isocyanurate.

[0040] The catalyst may be a combination of at least one of compound a) quaternary ammonium salt, quaternary ammonium base and quaternary phosphonium salt and compound b) one or more of five-membered or six-membered heterocyclic organic compounds containing nitrogen, phosphorus, oxygen or sulfur atoms.

[0041] The compound a is preferably one or more of tetrabutylammonium acetate, tetramethylammonium acetate, tetramethylammonium propionate, tetramethylammonium hydroxide, benzyltrimethylammonium hydroxide, and benzyltriphenylphosphine chloride; the compound b is preferably one or more of pyrazole, pyridine, imidazole, pyrrole, thiophene, furan, and pyridazine.

[0042] The terminator is an acid compound, including but not limited to at least one of di-n-butyl phosphate, hydrochloric acid, phosphoric acid, dimethyl phosphate, diethyl phosphate, p-toluenesulfonic acid, benzenesulfonic acid, alkylbenzenesulfonic acid, acetyl chloride, and benzoyl chloride.

[0043] The temperature of the trimerization reaction is 60-90°C;

[0044] The mass ratio of the hexamethylene diisocyanate to the catalyst is 200-100000:1; the amount of the terminator is not particularly limited, and preferably, the mass ratio of the hexamethylene diisocyanate to the terminator is 1000-10000:1.

[0045] The beneficial effects of the present invention are:

[0046] According to the method provided by the present invention, a hexamethylene diisocyanate composition having a cyclic compound content of 0.2-500 ppm can be obtained, and the chromaticity change rate after heat treatment at 140° C. for 4 hours is less than 8. The polyisocyanate product prepared using this as a raw material has excellent low chromaticity and relatively stable characteristics compared with existing products. DETAILED DESCRIPTION

[0047] The present invention is further described below in conjunction with the embodiments, but the present invention is not limited to the listed embodiments, and should also include any other known changes within the scope of the rights claimed by the present invention.

[0048] Raw materials and sources:

[0049] Hexamethylenediamine is an industrial-grade product of INVISTA (Shanghai); phosgene is produced by Wanhua Chemical Group Co., Ltd.; dichlorobenzene, Aladdin, purity 99.5%; tetrabutylammonium acetate, Aladdin, purity 99.5%; pyrazole, Aladdin, purity 99%; anhydrous ethanol, Merck Chemical, purity 99.5%; di-n-butyl phosphate, Aladdin, purity 98.5%; cyclohexylaminoacyl chloride, Chemenu, purity 95%.

[0050] The test of cyclic compounds in the hexamethylene diisocyanate composition in the following examples and comparative examples was carried out by gas chromatography. First, the different retention times of the above cyclic compound components in gas chromatography were determined by gas chromatography-mass spectrometry, and the contents were obtained by area normalization method. The test method is as follows:

[0051] The analytical instrument was Agilent 7890B; the chromatographic column model was DB-5 (30m×0.25mm×0.25um); the detector was an FID detector; the injection port temperature was 260°C; the detector temperature was 300°C; the temperature program was from 50°C to 90°C at 10°C / min, maintained for 2 min, from 15°C / min to 180°C, maintained for 2 min, from 20°C / min to 280°C, maintained for 15 min; the injection volume was 0.2ul.

[0052] The product colorimetry was tested using the German BYK LCS IV liquid colorimeter.

[0053] Examples 1-5 and Comparative Example 1-2 are hexamethylene diisocyanate compositions prepared by phosgene method; the prepolymer is prepared by using the hexamethylene diisocyanate compositions obtained in Examples 1-5 and Comparative Example 1-2 as raw materials.

[0054] Example 1

[0055] The inlet temperature of hexamethylenediamine entering the reactor is 378°C, the inlet temperature of phosgene entering the reactor is 382°C, the reaction pressure is 0.15MPa, the reaction temperature is 473°C, the reaction time is 16s, and the molar ratio of phosgene to hexamethylenediamine is 5.3:1. After the reaction product leaves the reaction zone, chlorobenzene is used for spraying and absorbing to obtain a hexamethylene diisocyanate composition reaction liquid, and the reaction liquid is subsequently dephosgenated and desolventized to obtain a crude hexamethylene diisocyanate composition, and the final product is obtained by refining.

[0056] The product is refined by continuous distillation, and the control parameters are as follows:

[0057] The number of theoretical plates of the distillation tower is 28, the pressure at the top of the distillation tower is 0.5 kpa, the temperature at the bottom of the distillation tower is 133°C, the reflux ratio is 4:1, the output from the top of the distillation tower is 5 wt%, the crude hexamethylene diisocyanate is fed from the 4th theoretical plate, and the purified product is withdrawn through the side line of the distillation tower, and the withdrawal position is between the 20th and 21st theoretical plates. The content of cyclic compounds in the obtained product is 94 ppm, and the chromaticity change rate is 2.5 after heat treatment at 140°C for 4 hours.

[0058] Example 2

[0059] The inlet temperature of hexamethylenediamine entering the reactor is 315°C, the inlet temperature of phosgene entering the reactor is 291°C, the reaction pressure is 0.02MPa, the reaction temperature is 374°C, the reaction time is 0.03s, and the molar ratio of phosgene to hexamethylenediamine is 8:1. After the reaction product leaves the reaction zone, chlorobenzene is used for spraying and absorbing to obtain a hexamethylene diisocyanate composition reaction liquid, and the reaction liquid is subsequently dephosgenated and desolventized to obtain a crude hexamethylene diisocyanate composition, and the final product is obtained by refining.

[0060] The product is refined by continuous distillation, and the control parameters are as follows:

[0061] The number of theoretical plates of the distillation tower is 33, the pressure at the top of the distillation tower is 1.2 kPa, the temperature at the bottom of the distillation tower is 141°C, the reflux ratio is 5:1, the output from the top of the distillation tower is 9wt%, the crude hexamethylene diisocyanate is fed from the 5th theoretical plate, and the purified product is withdrawn through the side line of the distillation tower, and the withdrawal position is between the 22nd and 23rd theoretical plates. The content of cyclic compounds in the obtained product is 0.7 ppm, and the chromaticity change rate after heat treatment at 140°C for 4 hours is 1.2.

[0062] Example 3

[0063] The inlet temperature of hexamethylenediamine entering the reactor is 492°C, the inlet temperature of phosgene entering the reactor is 507°C, the reaction pressure is 0.37MPa, the reaction temperature is 542°C, the reaction time is 9.2s, and the molar ratio of phosgene to hexamethylenediamine is 3:1. After the reaction product leaves the reaction zone, chlorobenzene is used for spraying and trapping to obtain a hexamethylene diisocyanate composition reaction liquid, and the reaction liquid is subsequently dephosgenated and desolventized to obtain a crude hexamethylene diisocyanate composition, and the final product is obtained by refining.

[0064] The product is refined by continuous distillation, and the control parameters are as follows:

[0065] The number of theoretical plates of the distillation tower is 17, the pressure at the top of the distillation tower is 4.7 kPa, the temperature at the bottom of the distillation tower is 183°C, the reflux ratio is 3:1, the output from the top of the distillation tower is 2.5 wt%, the crude hexamethylene diisocyanate is fed from the 6th theoretical plate, and the purified product is withdrawn through the side line of the distillation tower, and the withdrawal position is between the 14th and 15th theoretical plates. The content of cyclic compounds in the obtained product is 231 ppm, and the chromaticity change rate after heat treatment at 140°C for 4 hours is 7.2.

[0066] Example 4

[0067] The inlet temperature of hexamethylenediamine entering the reactor is 274°C, the inlet temperature of phosgene entering the reactor is 251°C, the reaction pressure is 0.015MPa, the reaction temperature is 331°C, the reaction time is 1.4s, and the molar ratio of phosgene to hexamethylenediamine is 14:1. After the reaction product leaves the reaction zone, chlorobenzene is used for spraying and absorbing to obtain a hexamethylene diisocyanate composition reaction liquid, and the reaction liquid is subsequently dephosgenated and desolventized to obtain a crude hexamethylene diisocyanate composition, and the final product is obtained by refining.

[0068] The product is refined by continuous distillation, and the control parameters are as follows:

[0069] The number of theoretical plates of the distillation tower is 38, the pressure at the top of the distillation tower is 9.3 kPa, the temperature at the bottom of the distillation tower is 124°C, the reflux ratio is 12:1, the output from the top of the distillation tower is 7wt%, the crude hexamethylene diisocyanate is fed from the 6th theoretical plate, and the purified product is withdrawn through the side line of the distillation tower, and the withdrawal position is between the 30th and 31st theoretical plates. The content of cyclic compounds in the obtained product is 0.3 ppm, and the chromaticity change rate is 4.8 after heat treatment at 140°C for 4 hours.

[0070] Example 5

[0071] The product obtained in Example 3 was used, and cyclohexylamino acid chloride was added thereto to adjust the cyclic compound content to 52 ppm.

[0072] Comparative Example 1

[0073] The inlet temperature of hexamethylenediamine entering the reactor is 527°C, the inlet temperature of phosgene entering the reactor is 536°C, the reaction pressure is 0.6MPa, the reaction temperature is 608°C, the reaction time is 23s, and the molar ratio of phosgene to hexamethylenediamine is 1:1. After the reaction product leaves the reaction zone, chlorobenzene is used for spraying and absorbing to obtain a hexamethylene diisocyanate composition reaction liquid, and the reaction liquid is subsequently dephosgenated and desolventized to obtain a crude hexamethylene diisocyanate composition, and the final product is obtained by refining.

[0074] The product is refined by continuous distillation, and the control parameters are as follows:

[0075] The number of theoretical plates of the distillation tower is 12, the pressure at the top of the distillation tower is 12.3 kPa, the temperature at the bottom of the distillation tower is 251°C, the reflux ratio is 1:1, the output from the top of the distillation tower is 1.8 wt%, the crude hexamethylene diisocyanate is fed from the 7th theoretical plate, and the purified product is withdrawn through the side line of the distillation tower, and the withdrawal position is between the 10th and 11th theoretical plates. The content of cyclic compounds in the obtained product is 562 ppm, and the chromaticity change rate after heat treatment at 140°C for 4 hours is 11.2.

[0076] Comparative Example 2

[0077] The inlet temperature of hexamethylenediamine entering the reactor is 194°C, the inlet temperature of phosgene entering the reactor is 197°C, the reaction pressure is 0.003MPa, the reaction temperature is 279°C, the reaction time is 0.01s, and the molar ratio of phosgene to hexamethylenediamine is 18:1. After the reaction product leaves the reaction zone, chlorobenzene is used for spraying and absorbing to obtain a hexamethylene diisocyanate composition reaction liquid, and the reaction liquid is subsequently dephosgenated and desolventized to obtain a crude hexamethylene diisocyanate composition, and the final product is obtained by refining.

[0078] The product is refined by continuous distillation, and the control parameters are as follows:

[0079] The number of theoretical plates of the distillation tower is 47, the pressure at the top of the distillation tower is 0.02 kpa, the temperature at the bottom of the distillation tower is 111°C, the reflux ratio is 16:1, the output from the top of the distillation tower is 15 wt%, the crude hexamethylene diisocyanate is fed from the 7th theoretical plate, and the purified product is withdrawn through the side line of the distillation tower, and the withdrawal position is between the 24th and 25th theoretical plates. The content of cyclic compounds in the obtained product is 0.13 ppm, and the chromaticity change rate after heat treatment at 140°C for 4 hours is 9.4.

[0080] The following prepolymers are prepared using the hexamethylene diisocyanate compositions obtained in Examples 1-5 and Comparative Examples 1-2, respectively. The prepolymer preparation method is implemented in the manner of Example 1 in patent CN112250835B.

[0081] Preparation Example

[0082] 5 g of a mixture of tetrabutylammonium acetate and pyrazole in a mass ratio of 1:0.8 was dissolved in 20 g of anhydrous ethanol to prepare a catalyst composition with a mass concentration of 20%. Under nitrogen protection, 2 kg of the hexamethylene diisocyanate composition obtained in the embodiment and the comparative example was heated in a 60°C water bath for 1 h, and then a catalyst composition with a content of 150 ppm (dry weight 0.3 g) relative to the hexamethylene diisocyanate monomer was added, and the reaction was continued at 70°C. When the NCO content in the reaction liquid reached 39.3%, dibutyl phosphate (0.24 g) with a content of 120 ppm relative to the hexamethylene diisocyanate monomer was added to terminate the reaction; then, a thin film evaporator was used to distill twice at 150°C and 0.2 Torr to prepare a polyisocyanate composition. The product was stored at 35°C and the chromaticity data was measured regularly, as shown in Table 1.

[0083]

[0084] In summary, by controlling the cyclic compound in the hexamethylene diisocyanate composition to be 0.1-500 ppm, the chromaticity change rate is less than 8 after heat treatment at 140° C. for 4 hours, and the polyisocyanate obtained using this as a raw material has excellent low chromaticity relative stability.

[0085] The above is only a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art may make several improvements and supplements without departing from the present invention, and these improvements and supplements should also be regarded as within the protection scope of the present invention.

Claims

1. A hexamethylene diisocyanate composition, characterized in that: The hexamethylene diisocyanate composition comprises hexamethylene diisocyanate and 0.2-500 ppm of a cyclic compound, wherein the cyclic compound comprises any one or a combination of at least two of the following compounds: Wherein X is CH3 or H or Cl or Br.

2. The hexamethylene diisocyanate composition according to claim 1, wherein The content of cyclic compounds in the hexamethylene diisocyanate composition is 0.4-200 ppm.

3. The hexamethylene diisocyanate composition according to claim 1, wherein The content of cyclic compounds in the hexamethylene diisocyanate composition is 0.8-100 ppm.

4. The hexamethylene diisocyanate composition according to any one of claims 1 to 3, characterized in that The color change rate of the product of the hexamethylene diisocyanate composition after heat treatment at 140° C. for 4 hours is less than 8; The chromaticity change rate of the isocyanate composition is tested in the following manner: 1) Using German BYK LCS IV liquid colorimeter to test the initial chromaticity of the hexamethylene diisocyanate composition, the initial value is recorded as H1; 2) Add a certain amount of hexamethylene diisocyanate composition into a 20 ml glass bottle and seal it with nitrogen; 3) After preheating the oven to 140° C., place the nitrogen-sealed glass bottle sample of the hexamethylene diisocyanate composition in the oven and heat for 4 hours; 4) After heating, take the sample out of the oven, cool it to room temperature, and then test the chromaticity, which is recorded as H2; The chromaticity change rate is (H2-H1) / H1*100%.

5. The method for preparing the hexamethylene diisocyanate composition according to any one of claims 1 to 4, characterized in that: The method comprises the following steps: preheating hexamethylenediamine in the presence or absence of an inert gas and then gasifying it, and reacting it with the preheated and gasified phosgene to obtain a hexamethylene diisocyanate composition reaction liquid; removing phosgene, removing hydrogen chloride and removing solvent from the reaction liquid obtained in the above steps to obtain the hexamethylene diisocyanate crude product; and finally removing impurities and refining the above obtained hexamethylene diisocyanate crude product to finally obtain the hexamethylene diisocyanate composition product.

6. The preparation method according to claim 5, characterized in that: Before the phosgenation reaction, the material stream containing hexamethylenediamine is preheated to above 200° C.; the temperature of the material stream containing phosgene is preheated to above 200° C.

7. The preparation method according to claim 5, characterized in that: The material stream containing hexamethylenediamine is preheated to 200-510°C before the phosgenation reaction; the material stream containing phosgene is preheated to 200-510°C.

8. The preparation method according to any one of claims 5 to 7, characterized in that: The inert gas is one or more of nitrogen, argon and helium.

9. The preparation method according to any one of claims 5 to 7, characterized in that: The reaction of phosgene and hexamethylenediamine is carried out under an absolute pressure of 0.01-0.5 MPa; the reaction temperature is 200-600° C., and the residence time of the amine and phosgene in the reaction zone is 0.02-20 seconds.

10. The preparation method according to any one of claims 5 to 7, characterized in that: The reaction of phosgene and hexamethylenediamine is carried out under an absolute pressure of 0.1-0.4 MPa; the reaction temperature is 300-550° C., and the reaction residence time of amine and phosgene in the reaction zone is 0.05-10 s.

11. The preparation method according to any one of claims 5 to 7, characterized in that: The molar ratio of phosgene to the amino group in hexamethylenediamine is 2-15:

1.

12. The preparation method according to any one of claims 5 to 7, characterized in that: The molar ratio of phosgene to the amino group in hexamethylenediamine is 4-8:

1.

13. The preparation method according to any one of claims 5 to 7, characterized in that: The impurity removal and purification is carried out in a distillation tower, the theoretical plate number of the distillation tower is 15-40; the reflux ratio of the distillation tower is 2-13:1; and / or, the top pressure of the distillation tower is 0.3-10 kPa; and / or, the bottom temperature of the distillation tower is 120-190°C; And / or, the extraction amount from the top of the distillation tower is 2-9wt%.

14. The preparation method according to any one of claims 5 to 7, characterized in that: The impurity removal and purification is carried out in a distillation tower, the theoretical plate number of the distillation tower is 25-35; the reflux ratio of the distillation tower is 2-6:1; and / or, the top pressure of the distillation tower is 0.7-5 kPa; and / or, the bottom temperature of the distillation tower is 130-145°C; And / or, the extraction amount from the top of the distillation tower is 3-7wt%.

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